Title of Invention

"A LAYER OF SINGLE CRYSTAL BORON DOPED DIAMOND AND A METHOD OF PRODUCING THE SAME"

Abstract A layer of single crystal boron doped diamond produced by CVD wherein the total boron concentration is uniform, with a variation over the majority volume which is less than 50%, measured with a lateral resolution at each measurement point of less than 50µm, wherein the majority volume represents at least 70% of the total volume of the layer, and wherein the layer has at least one of the following characteristics (i) to (iii): (i) the layer is formed from a single growth sector, (ii) the layer thickness exceeds 100 µm, and (iii) the volume of the layer exceeds 1 mm .
Full Text The present invention relates to a layer of single crystal boron diamond produced by cvd
BACKGROUND OF THE INVENTION
This invention relates to doped diamond and more particularly to doped diamond produced by chemical vapour deposition (hereinafter referred to as CVD diamond).
There are a range of applications of diamond for which a doped diamond layer of significant dimensions, with a uniform dopant concentration and associated electronic and/or optical properties would be advantageous. Dependent on the detailed application, this material needs to substantially exclude detrimental electronic or optically active traps or defects. To date, material of this type has not been available.
Applications such as high power electronics require bulk free standing diamond with thicknesses ranging from 50 to 1000 urn and lateral sizes varying from 1 x 1 mm2 to 50 x 50 mm2. For viable production in a competitive market it is beneficial that the diamond used for these structures is grown as a bulk material and processed into the final devices. In addition, wafer scale processing is possible with larger pieces, further reducing device fabrication costs. For optical applications, such as filters and absorbed power measurement devices, the large size and thickness of the raw material can be an intrinsic requirement of the device. Thus there are a range of benefits to . synthesising thick layers.
Boron is the only known dopant in diamond which has well characterised relatively shallow dopant behaviour Other potentially shallow dopants reported in the liteiature to be under investigation include S, P, O, Li, but these are not yet available as reliable bulk dopants There are many electronic applications which need doped diamond, often over relatively large areas and with very uniform properties However, the incorporation of boron during synthesis is a very sensitive property of the particular growth sector Polycrystalline diamond contains a random selection of growth sectors, and although the average boron concentration may be uniform on a scale much larger than the grain size, at the same scale as the grain size the local boron concentration varies substantially from point to point
Dopants can also be put into diamond by post growth treatment The only currently reliable post growth treatment applicable to diamond is ion implantation, and this provides a method of producing layered diamond structures, but not uniform bulk doping For instance, a 'p-i' (p-type - intrinsic) structure can be produced by using an appropriate dose and energy for boron implantation into a high quality natural type lla diamond Unfortunately residual damage (vacancies and interstitials) is always created under conditions of ion implantation This damage is impossible to remove completely, although annealing treatments can reduce it The damage leads to degraded charge earner properties resulting from defect scattering and compensation of boron acceptors
Methods of depositing or growing material such as diamond on a substrate by chemical vapour deposition (CVD) are now well established and have been described extensively in the patent and other literature Where diamond is being deposited on a substrate by CVD, the method generally involves providing a gas mixture which, on dissociation, can provide hydrogen or a halogen (e g F,CI) in atomic form and C or carbon-containing radicals and other reactive species, e g CHX, CFX wherein x can be 1 to 4 In addition,
oxygen containing sources may be present, as may sources foi nitrogen, and for boron In many processes inert gases such as helium, neon or argon are also present Thus, a typical source gas mixture will conlam hydiocarbons CxHy wherein x and y can each be 1 to 10 or halocarbons CxHyHalz wherein x and z can each be 1 to 10 and y can be 0 to 10 and optionally one or more of the following COx, wherein x can be 0 5 to 2, O2, H2 and an inert gas Each gas may be present in its natural isotopic ratio, or the relative isolopic ratios may be artificially controlled, for example hydrogen may be present as deuterium or tritium, and carbon may be present as 12C or 13C Dissociation of the source gas mixture is brought about by an energy source such as microwaves, RF (radio frequency) energy, a flame, a hot filament or jet based technique and the reactive gas species so produced are allowed to deposit onto a substrate and form diamond
CVD diamond may be produced on a variety of substrates Depending on the nature of the substrate and details of the piocess chemistry, polycrystalline or single crystal CVD diamond may be produced
Obtaining incorporation of boron into the solid during deposition is less difficult than for many other potential dopants The incorporation ratio for boron, which is the ratio of the dopant boron (B) to caibon (C) concentration in the solid ([B]/[C] solid), compared to that in the depositing gas ([B]/[C] gas) is generally about 1 (in the {100} growth sector) although it varies with many factors There are many methods by which CVD diamond may be doped during synthesis with boron With microwave plasma, hot filament and arc jet techniques, diborane (B2H6) or some other appropriate gas may be added to the gas stream, the incoming gases may be bubbled through methanol or acetone containing bona (B2O3), boron powder may be placed in the chambei, or a boron rod inserted into the plasma For growth by the combustion flame method a fine mist of methanol containing boric acid can be injected into the gas stream with an atomiser Diamond films have also been doped
unintentionally when, for example, the plasma has decomposed a substrate holder fabricated from hexagonal boron nitride
Nitrogen can also be introduced in the synthesis plasma in many forms Typically these are N2, NH3, air and N2H4
Although high purity single crystal (SC) CVD diamond has an important role in potential high power electronics, the number of potential applications would be substantially increased if a CVD doped diamond with uniform and advantageous electronic properties was available In addition, there are other applications of boron doped diamond where uniformity in the co\ovtr, luminescence, or other properties associated with B doping is advantageous
SUMMARY OF THE INVENTION
According to a first aspect of the invention, there is provided a layei of single crystal boron doped diamond produced by CVD wherein the total boron concentration is uniform, with a variation over the majority volume which is less than 50%, and preferably less than 20%, measured with a lateral resolution at each measurement point of less than 50 µm, and preferably with a lateral resolution at each measurement point of less than 30 µm,
and having at least one of the characteristics (i) to (iii)
(i) the layer is formed from a single growth sector, which is preferably one of the {100}, the {113}, the {111} and the {110}, and more preferably the {100}, sectors,
(ii) the layer thickness exceeds 100 (im, and preferably exceeds 500 µm, and
(m) the volume of the layer exceeds 1 mm3, and preferably exceeds 3 mm3, and more preferably exceeds 10 mm3, and even more pieferably exceeds 30 mm3
The term "majonty volume" as used herein and in the claims represents al least 70%, preferably greater than 85%, and more preferably greater than 95%, of the total volume of the diamond layer
The CVD single crystal boron doped diamond layei of the invention may also contain nitrogen as a dopant The diamond layer will generally contain a nitrogen concentration no greater than 1/5 of that of the boron concentration, and preferably less than 1/50 of that of the boron concentration
The diamond layer is preferably of "high ciyslalline quality" In this context "high crystalline quality" allows the presence of the dopant boron atoms and nitrogen atoms and associated point defects such as those including vacancies, hydrogen and the like
The single crystal boron doped diamond layer may also have one or moie of the following chaiactenstics in the majority volume of the diamond, where that majority volume is defined as above
(a) the layer contains an uncompensated boron concentration greater than1x1014 atoms/cm3 and less than 1 x 1020 atoms/cm3, preferably an uncompensated boron concentration greater than 1 x 1015 atoms/cm3 and less than 2 x 1019 atoms/cm3, and more preferably an uncompensated boipn concentration greater than5xl015 atoms/cm3 and less than 2 x 1018 atoms/cm3,
b) a hole mobility (uh) measured at 300K which exceeds
for Nh not exceeding 8 x 1015 atoms/cm3
(Equation Removed)
for Nh greater than 8 x 1015 atoms/cm3
(Equation Removed)
where Nh is the concentration of holes (or equivalently, the concentration of ionised boron acceptors), the functional relationship between p.h and Nh is based on current models and the value of G represents the gain over the best values of |ih currently reported G has a value of greater than 1 1, and preferably a value greater than 1 4, and more preferably a value greater than 1 7, and even more preferably a value greater than 20
(c) Low or absent luminescent features at 575 and 637 nm, relating to nitrogen-vacancy (N-V) centres Specifically, the ratio of integrated intensities of the nitrogen vacancy centre zero-phonon lines at 575 nm and 637 nm centre is less than 1/50, and preferably less than 1/100, and more preferably less than 1/300 the integrated intensity of the diamond Raman line at 1332 cm-1 when measured at 77 K with 514 nm Ar ion laser excitation
(d) A Raman line width as measured at 300K of less than 4 cm"1
FWHW (full width at half maximum height) and preferably less
than 3 cm1 and more prefeiably less than 2 5 cm"1, undei 514
nm Ar ion excitation
(e) A high degree of uniformity in the uncompensated boron concentration as measured by FTIR using the method described below In particular, the frequency distribution of uncompensated boron measurements taken by FTIR over a representative sample taken from the layer must be such that 90% of the measurements vary by less than 50%, and preferably by less than 30%, expressed as a percentage or the mean
(f) A uniform bound exciton emission (BE) at 238 nm consistent with the concentration of uncompensated substitutional boron atoms in the solid, measuring the BE at 77 K under UV excitation using the method described below In particular, the frequency distribution of the BE taken by this method over any representative surface of the layer or sample taken from the layer must be such that 90% of the measurements vary by less than 50%, and preferably by less than 30%, expressed as a percentage of the mean
(g) A strong free exciton (FE) intensity measured at 77 K under UV excitation, with a high degree of uniformity measured using the method given below In particular, the frequency distribution of FE measurements taken by this method over any representative surface of the layer or sample taken from the layer must be such that 90% of the measurements vary by less than 50%, and
preferably by less than 30%, expressed as a percentage of the mean
The high mobility found in the CVD diamond of the invention is surprising The current model for the variation of the mobility with concentration of carriers (or ionised acceptors), in the domain where the carrier concentration is greater than 8 x 1015 atoms/cm3, is based on the belief that the acceptor boron atoms are the dominant scattering mechanism, and that their contribution is essentially intrinsic to their presence Consequently this model suggests that values higher than this cannot be achieved In contrast therefore, the results of (he work described herein show the model to be in error, in (hat other factors, which can be removed, have previously limited the mobility in doped diamond reported in the literature
The single crystal boron doped CVD diamond layer of the invention may be free standing or form a layer or region of a larger diamond body or layer That larger diamond layer or body may be single crystal or polycrystalline diamond produced by CVD or other synthetic method That larger diamond layer or body may be doped with boron, nitrogen or other elements
The diamond layer or body of the invention may take the form of a gemstone
According to another aspect of the invention there is provided a method of producing a layer of boron doped single crystal CVD diamond This method includes the steps of providing a diamond substrate having a surface which is substantially free of crystal defects, providing a source gas, such source gas including a source of boron, dissociating the source gas and allowing homoepitaxial diamond growth on the surface which is substantially free of crystal defects thereby producing a layer of single crystal boron doped diamond, preferably of the type described above Essential to this method is
that the diamond giowth takes place on a diamond surface that is substantially free of crystal defects
The method of the invention may additionally include the use of controlled nitrogen additions to the source gas The nitrogen in the source gas provides an additional means of control of the morphology developed by the growing single crystal, and the incorporation ratio for nitrogen is substantially lower than that for boron Thus nitrogen additions, calculated as molecular nitrogen, in the range greater than 0 5 ppm and less than 10000 ppm, and preferably in the range greater than 1 ppm and less than 1000 ppm, and more preferably in the range greater than 3 ppm and less than 200 ppm do not adversely affect the electronic properties of the boron doped layer significantly, since the doped material intentionally has boron piesenl as a scattering centre, but does enhance the size of the {100} giowth sector and reduce the size of competing growth sectors such as the {111} This means that, for growth on a {100} plate, the addition of nitrogen enables the growth to remain substantially {100} growth sector Those skilled in the ait will appreciate that the stage of using nitrogen to modify the morphology, and the stage of growing the unifoimly boron doped layei may be separated or sequential
The uniformly boron doped diamond of the invention thus enables a wide range of applications in areas such as electronic, deteclois, high powei electronics etc In addition, there are other applications where the uniformity in the colour, luminescence, or other properties associated with uniform boron doping is advantageous For example, in certain applications such as a cutting blade, boron may be used to colour the diamond thus improving visual control, and uniformity in the colour can be perceived as a factor indicating quality Alternatively the diamond may be used in decorative applications such as polished gemstones, where uniformity in colour is again generally perceived as a quality factor
For the various applications mentioned above, the diamond layer or body may be used as such or it may be severed, by cutting for example, to produce two or more and generally a large number of smaller pieces or elements which will find use in one or more of the applications described above The shape and size of the piece or element will be dictated by the application
DETAILED DESCRIPTION OF THE INVENTION
In addition to the characteristics described above, the layer of single crystal boron doped CVD diamond of the invention may have one or more of the following characteristics in the majority volume of the diamond layer, the majority volume being that defined above
1 A level of any single impurity Si, P, S, Ni, Co, Al, Mn, Fe of not greater than 1 ppm and a total content of these impurities of not greater than 5 ppm Preferably the level of any of these impurities, other than B and N, is not greater than 0 05 to 0 5 ppm and the total content of these impurities is not greater than 0 5 to 2 ppm
2 A cathodoluminescence (CL) emission signal in the 575 nm band which is low or absent, and an associated photoluminescence (PL) line, measured at 77 K under 514 Ar ion laser excitation (nominally 300 mW incident beam) which has an integrated peak area less than 1/50 and preferably less than 1/100 and more preferably less than 1/300 of the integrated peak area of the diamond Raman peak at 1332 cm1
3 In electron spin paramagnetic resonance (EPR), a neutral single substitutional nitrogen centie [N-C]° at a concentration less than 40 ppb and more typically less than 10 ppb
4 In EPR, a spin density less than 1 x 1017 cm3 and more typically
less than 5 x 1016 cm"3 at g=2 0028 In single crystal diamond this
line at g = 2 0028 is related to lattice defect concentialions and is
typically large in natural type lla diamond, in CVD diamond
plastically defoimed through indentation, and in pooi quality
homoepitaxial diamond
5 Excellent optical properties having a UVA/isible and IR (infrared)
transparency close to the theoretical maximum for type lib diamond
and, more particularly, low or absent single substitutional nitrogen
absorption at 270 nm in the UV (ultraviolet), and low or absent C-H
stretch bands in the spectral range 2500 to 3100 cm"1
wavenumbers in the IR The absorption spectrum of
semiconducting boton doped diamond is characterised by a
continuum absorption starting at about 370 meV in the near
infrared spectral region, and extending into the visible region to
about 2 2 eV This absorption is responsible for the characteustic
blue coloui (pale blue for concentrations ~5 x 1015 cm3 and very
dark blue to black for ~5 x 1019 cm3) Thiee prominent bands at
304, 348 and 363 meV aie observed at energies below the
continuum threshold which, if measured at low temperature with
high resolution, exhibit a considerable amount of fine structure
6 X-ray topographs showing features related to growth where edges of the original substiate are grown out to form edges
As the concentration of the potentially compensating nitrogen is substantially lower than that of the boron, uniformity in the uncompensated boron distribution is generally indicative of unifoimity in the total boron concentration
In addition, the electronic properties are primarily dependent on the uncompensated boron concentration rather than the total boron concentration Thus uniformity in the uncompensated boron is an important parameter
Diamond containing uncompensated boron shows a characteristic one-phonon absorption feature with a maximum at 1282 cm-1 (159 meV) It has been found that there is a linear relationship between the concentration of uncompensated boron and the contribution of this band to the absorption coefficient at 1282 cm 1 The concentration of boron in ppm is 1 2 x (Absorption Coefficient at 1282 cm1) when the measurement is carried out at room temperature
Diamond containing uncompensated boron also shows a characteristic absorption at 2457 cm-1 (304 5 meV) that can be revealed by subtraction of the intunsic two-phonon absorption When the feature at 1282 cm"1 is too weak to be usable, the uncompensated boron concentration can be derived from the integiated absorption coefficient of the band at 2457 cm"1 using the relationship
uncompensated B cone (ppm) = 0 00142 x integrated absorption coefficient at 2457 cm-1 (meV cm-1)
A bulk measurement of the uniformity of the concentration of the uncompensated boron in a parallel sided diamond sample can be made using FTIR absoiption spectroscopy in the following way A representative map of the infrared absorption characteristics over the whole sample is built up by collecting FTIR spectra at room temperature with a 0 5 cm"1 resolution and an aperture size of 0 5 mm, the map containing a minimum of 20 datapoints One of the relationships above is then chosen based on the average measurement taken and used to derive the concentration of uncompensated boron for each position The uniformity is then judged from the fiequency plot of the concentration measurements taken, assessing the percentage of

measurements further away from the average than the limit to the deviation set
The ultraviolet cathodoluminescence spectia (recorded at 11 K) of high quality boron doped diamond shows strong boron bound exciton emission at 5 22 eV (237 5 nm) and free exciton emission at 5 27 eV (235 2 nm) For high quality diamond with boron concentrations up to approximately 1 ppm, there exists an approximate proportionality between the ratio of the integrated intensities of these two emissions measured at 77 K and the concentration of uncompensated boron This is given by the relationship
[uncompensated B in ppm] = 1 86 x l(B bound exciton intensity)/1 (free exciton intensity)
Across a wide range of boron concentrations measurement of this latio at different positions across a sample can be used to judge the uniformity of the characteristics of the diamond in the near surface region The sample is coated with a thin (5 nm), uniform layer of gold to prevent charging effects, mounted at 11 K in an scanning electron microscope and a MonoCL system is used to collect UV CL spectra with an accelerating voltage of 15 kV, a current of 0 2 microamps and a spot size of less than 10 pm x 10 pm
The UV CL characteristics of a sample can be mapped by collecting spectra at positions defined by the intersection points of a grid made up of two sets of perpendicular lines with a spacing of 500 µm or 1 mm dependent on the area to be covered, aquiring data at a minimum of 30 points The uniformity is then judged from the frequency plot of the concentration measurements taken, assessing the total width of the distribution of 90% of the measurements expressed as a percentage of the mean value This procedure was applied to the measured intensity of the bound exciton and free exciton emission, and to the calculated ratio of the two intensities
Where there is significant variation in trapping defects that quench the bound exciton emission, then these increase the variation observed in the bound exciton emission, unless the bound exciton emission is totally quenched everywhere by them
The presence of a strong free exciton indicates the substantial absence of defects such as dislocations and impurities The link between low defect and impurity densities and high FE emission has been previously reported for individual crystals in polycrystalline CVD diamond synthesis At higher boron levels, typically greater than 20 - 25 ppm in the solid, the free exciton emission is eventually quenched by the high boron point defect density and not due to crystalline defects such as dislocations Uniformity of the free exciton emission is a good measure of the lack of local high densities of defects
SIMS analysis was typically performed 02+ primary beam , with a primary voltage of 10kV, a beam current of typically 1 pA and a spatial resolution of less than 50 pm Mapping was typically completed by stepping the analysis point on a 0 5 mm or 1 mm pitch over the face of the layer, obtaining from each face typically a minimum of 20 points and more preferably a minimum of 40 points Calibration was by comparison with implant standards Data from the SIMS was analysed by finding the mean of the dataset, and then finding the full range of the data expressed as a percentage of the mean for the different % fractions of the dataset, with the two opposite major faces of a layer given approximately equal weighting in order to characterise a volume Reproducibility of the SIMS is typically of the order of 3-5%, dependent on conditions, with a detection limit around 2-5 x 1014 atoms/cm3
In order to chaiactense a volume of material, typically the two opposite surfaces were characterised by SIMS and BE/FE mapping, and the through thickness sample by IR absorption
The resolution of the measurement technique (SEM analysis foi BE, FE and uncompensated boron concentration, and SIMS analysis for total boron concentration), is relevant to the types of variations in boron concentration which can be observed in diamond For example, in polycrystallme diamond, with a typical grain size of 100 µm, a 1 mm analysis spot scanned across the sample may average out and thus not observe the substantial variations of B concentration found between individual grains or growth sectors By taking a sample of 20 or more datapoints with a resolution of 50 pm or less, it is possible to demonstrate that such small scale variations are not present
It is important for the production of the uniformly boion doped CVD diamond single crystal layer of the invention that giowth takes place on a diamond surface which is substantially free of crystal defects In this context, defects primarily mean dislocations and micro cracks, but also include twin boundanes, point defects, low angle boundaries and any other disruption to the crystal structure Preferably the substrate is a low birefiingence type la natural, lb or lla high pressure/high temperature synthetic diamond or a CVD synthesised single crystal diamond Defects can degrade the material in two ways, adversely affecting the electronic properties (e g the hole mobility) and also influencing the local uptake of boron Since dislocation multiplication occurs dunng the growth of thick layers, the control of dislocations within the substrate and early stages of growth is particularly important
The defect density is most easily characterised by optical evaluation after using a plasma or chemical etch optimised to reveal the defects (referred to as a revealing plasma etch), using for example a brief plasma etch of the type described below Two types of defects can be revealed
1) Those intrinsic to the substrate material quality In selected natural diamond the density of these defects can be as low as 50/mm2 with more typical values being 102/mm2, whilst in others it can be 106/mm2 or greater
2) Those resulting from polishing, including dislocation structures and microcracks forming chatter tracks (sometimes known as clatter tracks) along polishing lines The density of these can vary considerably over a sample, with typical values ranging from about 102/mm2, up to more than 104/mm2 in poorly polished regions or samples
The pieferred low density of defects is such that the density of surface etch featuies related to defects, as described above, is below 5 x 103/mm2, and moie prefeiably below 102/mm2
The defect level at and below the substrate surface on which the CVD growth takes place may thus be minimised by careful preparation of the substrate Included here under preparation is any process applied to the material from mine recovery (in the case of natural diamond) or synthesis (in the case of synthetic material) as each stage can influence the defect density within the material at the plane which will ultimately form the substrate surface when piepaiation as a substrate is complete Particular processing steps may include conventional diamond processes such as mechanical sawing, lapping and polishing (in this application specifically optimised to yield low defect levels), and less conventional techniques such as laser processing or ion implantation and lift off techniques, chemical/mechanical polishing, and both liquid and plasma chemical processing techniques In addition, the surface RQ (root mean square deviation of surface profile from flat measured by stylus profilometer, preferably measured over 0 08 mm length) should be minimised,
typical values pnoi to any plasma etch being no more than a few nanometeis, i e less than 10 nanometers
One specific method of minimising the surface damage of the substrate, is to include an in situ plasma etch on the surface on which the homoepitaxial diamond giowth is to occur In principle this etch need not be in situ, nor immediately prior to the growth process, but the greatest benefit is achieved if it is in situ, because this avoids any risk of further physical damage or chemical contamination An in situ etch is also generally most convenient when the growth process is also plasma based The plasma etch can use similar conditions to the deposition or diamond giowing process, but with the absence of any carbon containing source gas and generally at a slightly lower temperature to give better control of the etch rate For example, it can consist of one or more of
(i) an oxygen etch using predominantly hydrogen with optionally a small amount of Ar and a required small amount of 02 Typical oxygen etch conditions are piessures of 50-450 x 102 Pa, an etching gas containing an oxygen content of 1 to 4 percent, an aigon content of 0 to 30 percent and the balance hydrogen, all percentages being by volume, with a substrate temperatuie 600-1100°C (more typically 800°C) and a typical duration of 3-60 minutes
(n) a hydrogen etch which is similar to (i) but where the oxygen is absent
(in) alternative methods for the etch not solely based on argon, hydrogen and oxygen may be used, for example, those utilising halogens, other inert gases or nitrogen
Typically the etch consists of an oxygen etch followed by a hydrogen etch and then moves directly into synthesis by the introduction of the carbon source gas The etch time/temperature is selected to enable remaining surface damage fiotn processing to be removed, and for any surface contaminants to be removed, but without forming a highly roughened surface and without etching extensively along extended defects such as dislocations which intersect the surface and thus cause deep pits As the etch is aggressive, it is particularly important for this stage that the chamber design and material selection for its components be such that no material is transferred by the plasma into the gas phase or to the substrate surface The hydrogen etch following the oxygen etch is less specific to crystal defects, rounding off the angularities caused by the oxygen etch which aggressively attacks such defects and providing a smoother, better surface for subsequent growth
The surface or surfaces of the diamond substrate on which the CVD diamond growth occurs are preferably the {100}, {110}, {113} or {111} surfaces Due to processing constraints, the actual sample surface orientation can differ from these ideal orientations up to 5°, and in some cases up to 10°, although this is less desirable as it adversely affects reproducibility
It is also important in the method of the invention that the impurity content of the environment in which the CVD growth takes place is properly controlled More particularly, the diamond growth must take place in the presence of an atmosphere containing substantially no contaminants, and that the intentionally added boron (and nitrogen if used) concentrations are suitably controlled The degree of control required for the boron and nitrogen dopant concentrations is application dependent, but typically needs to be stable to better than 20% and, more typically better than 10%, and even more typically better than 3% Such control requires careful control of the nitrogen impurities in the source gas, as nitrogen is a common contaminant In order to achieve this degree of control, the level of nitrogen m the source gas, prior to the deliberate nitrogen addition,
is generally maintained at less than 500 parts per billion in the gas phase (as a molecular fraction of the total gas volume), and preferably less than 300 parts per billion, and more preferably less than 100 parts per billion Measurement of absolute and relative nitrogen (and boron) concentrations in the gas phase at concentrations as low as 100 ppb requires sophisticated monitoring equipment such as that which can be achieved, for example, by gas chromotography An example of such a method is now described
Standard gas chromatography (GC) art consists of A gas sample stream is extracted from the point of interest using a narrow bore sample line, optimised for maximum flow velocity and minimum dead volume, and passed through the GC sample coil before being passed to waste The GC sample coil is a section of tube coiled up with a fixed and known volume (typically 1cm3 for standard atmospheric pressure injection) which can be switched from its location in the sample line into the carrier gas (high purity He) line feeding into the gas chromatography columns This places a sample of gas of known volume into the gas flow entering the column, in the art, this procedure is called sample injection
The injected sample is carried by the carrier gas through the fust GC column (filled with a molecular sieve optimised for sepaiation of simple inorganic gases) and is partially separated, but the high concentration of primary gases (e g H2, Ar) causes column saturation which makes complete separation of, foi example nitrogen difficult The relevant section of the effluent from the first column is then switched into the feed of a second column, thereby avoiding the majority of the other gases being passed into the second column, avoiding column saturation and enabling complete separation of the target gas (N2) This procedure is called "heart-cutting"
The output flow of the second column is put through a discharge lonisation detector (DID), which detects the increase in leakage current through the carrier gas caused by the presence of the sample Chemical identity is determined by the gas residence time which is calibrated from standard gas mixtures The response of the DID is linear over more than 5 orders of magnitude, and is calibrated by use of specially prepared gas mixtures, typically in the range of 10-100 ppm, made by gravimetric analysis and then verified by the supplier Linearity of the DID can be verified by careful dilution experiments
This known art of gas chromatography has been further modified and developed for this application as follows The processes being analysed here are typically operating at 50 - 500 x 102 Pa Normal GC operation uses the excess pressure over atmospheric pressure of the source gas to drive the gas through the sample line Here, the sample is driven by attaching a vacuum pump at the waste end of the line and the sample drawn through at below atmospheric pressure However, whilst the gas is flowing the line impedance can cause significant pressure drop in the line, affecting calibration and sensitivity Consequently, between the sample coil and the vacuum pump is placed a valve which is shut for a short duration before sample injection in order to enable the pressure at the sample coil to stabilise and be measured by a pressuie gauge To ensure a sufficient mass of sample gas is injected, the sample coil volume is enlarged to about 5 cm3 Dependent on the design of the sample line, this technique can operate effectively down to pressures of about 70 x 102 Pa Calibration of the GC is dependent on the mass of sample injected, and the greatest accuracy is obtained by calibrating the GC using the same sample pressure as that available from the source under analysis Very high standards of vacuum and gas handling practice must be observed to ensure that the measurements are correct
The point of sampling may be upstream of the synthesis chambet to characterise the incoming gases, within the chamber to characterise the chamber environment, or downstream of the chambei
Typically B was added to the process as B2H6 using a calibrated source of nominally 100 ppm B2H6 in H2 to simplify control, and likewise the nitrogen was added to the process as N2 using a calibrated source of nominally 100 ppm N2 in H2 to simplify control Additions of both B and N are expressed as ppm, calculated for B as [B2H6]/[AII gases] where [B2H6] represents (he number of moles of B2H6 and [All gases] represents the number of moles of all gases present, and likewise as [NJ/fAII gases] for N2
The gas mixture used in the synthesis process may contain any gases known in the art and will contain a caibon-contaming material which dissociates producing radicals or other reactive species The gas mixture will also generally contain gases suitable to provide hydrogen or a halogen in atomic form
The dissociation of the source gas is preferably carried out using microwave energy in a reactor examples of which are known in the art However, the transfer of any impurities from the reactor should be minimised A miciowave system may be used to ensure that the plasma is placed away from all surfaces except the substrate surface on which diamond growth is to occur and its mount, the substrate earner Examples of a pieferred mount matenals are molybdenum, tungsten, silicon and silicon carbide Examples of prefened reactor chamber materials are stainless steel, aluminium, copper, gold, platinum
A high plasma power density should be used, resulting from high microwave power (typically 1-60 kW, for substrate carrier diameters of 25-300 mm) and high gas pressures (50-500 x I02 Pa, and preferably 100-450 x I02 Pa)
Usmg the above conditions it has been possible to produce thick high quality boron doped single crystal CVD diamond layers with charge carriers of unusually high mobility and with a morphology optimised for the production of unifoim large volumes suitable for commercial products
Some examples of the invention will now be described
EXAMPLE 1
Substiates suitable for synthesising single crystal CVD diamond of the invention may be prepared as follows
(i) Selection of stock material (la natural stones and lb HPHT stones) was optimised on the basis of microscopic investigation and birefringence imaging to identify substrates which were free of strain and imperfections
(n) Laser sawing, lapping and polishing to minimise subsurface defects using a method of a revealing plasma etch to determine the defect levels being introduced by the processing
(in) After optimisation it was possible routinely to produce substrates having one or more surfaces in which the density of defects measurable after a revealing etch is dependent primarily on the material quality and is below 5 x 103/mm2, and generally below 102/mm2 Substrates prepared by this process are then used for the subsequent synthesis
A high temperature/high pressure synthetic 1b diamond was grown in a high pressure ptess, and as a substrate using the method described above to minimise substrate defects to form a polished plate 7 65 x 8 25 mm2 by 0 54 mm thick, with all faces {100} The surface roughness RQ at this stage was less than 1 nm The substiate was mounted on a tungsten substrate carrier using a high temperature diamond braze This was introduced into a reactor and an etch and growth cycle commenced as described above, and more particularly
1) The 2 45 GHz microwave leaclor was pre-fitted with point of use purifiers, reducing unintentional contaminant species in the incoming gas stream to below 80 ppb
2) An in siiu oxygen plasma etch was performed using 15/75/600 seem (standard cubic centimetre per minute) of 02/Ar/H2 at 270 x 102 Pa and a substiate temperature of 753°C for a penod of 10 minutes
3) This moved without interruption into a hydrogen etch with the removal of the 02 from the gas flow, at a temperature of 758°C for a period of 10 minutes 4) This moved into the growth process by the addition of the carbon source (in this case CH4 ) and dopant gases The CH4 flow was at 30 seem B2H6 was used as the source of boron dopant The B2H6 gas phase concentration was 1 4 ppm The temperature was 780°C
4) On completion of the growth period, the substrate was removed from the reactor and the CVD diamond layer grown on a surface of low defect density, as described above, removed from the substrate
5) This layer was then polished flat to produce a unifoimly doped 735 µm thick layer with edges and lateral dimensions about 5x5 mm2
6) This layer, identified as CD-1, was cleaned and oxygen ashed to a surface terminated by O2 and tested for its mobility using the Hall technique This was found to be 360 cm2A/s at 300K, and 185 cm2/Vs at 440K This data is consistent with a T3'2 dependence predicted by a model of acoustic phonon scattering
7) The layer was analysed using SIMS, and measured to have a uniform total B concentration of 6 2 x 1018 atoms/cm3
8) The carrier concentration was measured using the Hall technique and found to be 4 5 x 1013 at 200 K, 4 x 1015 at 300 K, and 1 6 x 1017 at 500 K Based on a carrier concentration of 4x I015 at 300 K, equation (1) giving the upper bounds of reported material would predict a mobility of 163 cm2/Vs, compared with the measured value of 360 cm2/Vs Thus G, the factor (defined in equation 1 above), showed an improvement or gain over poor art materials of greater than 2 2
EXAMPLE 2
The procedure set out in Example 1 was repeated with the following variation in conditions
1) The polished HPHT substrate plate was 5 x 5mm square by 500 µm thick, with all faces {100}
2) The in situ oxygen plasma etch was performed using 15/75/600 seem of O2/Al/H2 at 333 x 102 Pa and a substrate temperature of 800°C for a period of 30 minutes
3) This was followed by a 30 minute hydrogen etch, in which the 02 was removed from the process stieam and a temperature of 810°C recorded
4) The growth process was initiated by the addition of CH4 flowing at 36 seem, and B2H6 and N2 flows to give gas phase concentrations of 0 05 and 7 ppm, respectively The temperature was 812°C
5) On completion of the growth period, the subsliate was removed from the reactor and the CVD diamond layer removed from the substrate
6) This layer, identified as CD-2, was then polished flat to produce a 410 urn thick layer with edges and lateral dimensions 7x7 mm2
7) The layer was analysed using SIMS, and a series of
measuiemenls showed the layer to have a uniform boion
concentration of 6 1 x 1016 atoms/cm3 SIMS mapping of the B
concentration showed no variation in concentiation within the
resolution of the mapping capability, which had a lateral spatial
resolution less than 30 mm and a sensitivity at the level of
measurement of better than 10% The nitrogen concentration
was measured to be less than 5 x 1015 atoms/cm3
8) This layer CD2 was cleaned and oxygen ashed to a surface terminated by O2 and tested for its mobility and carrier concentration The carrier concentration was measured to exceed 4 5x1013 and the mobility was measured to exceed 2 5 x 103 cm2/Vs, giving a value for G of about 1 5
9) CD-2 was further characterised by the data provided below
(i) The CL spectra showing free and bound exitons and no other features
(n) EPR spectra, showed no neutral substitutional nitrogen and only a weak line at g=2 0028
(m) Optical spectra showing the near theoretical transmission beside the characteristic absorption associated with a uncompensated boron concentration of 6 5x101e atoms/cm3
(iv) X-ray rocking curves map, showing the angular spread of the sample to be less than 10 arc sec
(v) Raman spectrum showing a line width (FWHM) to be approximately 2 cm-1
EXAMPLE 3
The procedure set out in Example 1 was repeated with the following variation in the growth conditions
Ar 75 seem, H2 600 seem, CH4 30 seem, 330 x 102 Pa, 795°C, 4 4 kW, boron and nitrogen gas phase concentrations of 15 and 0 5 ppm respectively The CVD diamond layer grown was then suitably processed and analysed on both surfaces of the layer which was 300 urn thick
On the top surface, a SIMS map showed a boron concentration of 1 75 x 1019 cm3 and on the opposite side an average SIMS concentration of 1 98x1019cm"3
EXAMPLE 4
The procedure set out in Example 1 was repeated with the following variation in the growth conditions
Ar 50 seem, H2 600 seem, CH4 40 seem, 330 x 102 Pa, 795°C, 4 4 kW, boron and nitrogen gas phase concentrations of 0 05 and 0 7 ppm respectively The CVD diamond layer grown was then suitably processed and analysed on both surfaces of the layer which was 113pm thick
On the top surface, SIMS maps were obtained on both a 0 5 mm pilch over an area of 2 mm x 4 5 mm, and over the larger area of 5 mm x 6 mm on a 1 mm pitch Data on the back surface was obtained on a 1 mm pitch The volume undei analysis was thus 3 4 mm3
On the front surface the mean boron concentration was measured to be 0 56 , and on the back surface 0 52 ppm The percentage volume of the material thus conforming to a particular range of concentrations about the mean was thus determined to be as shown in Table 1
TABLE 1 - SIMS concentration and distribution analysis for B on 1 mm pitch
(Table Removed)
Thus, from Table 1 it can be seen that 100% of the B measurements fell within a total range of 47% on the top face of the sample, and within a range of 30% on the i ear face of the sample, and within a range of 48% for both major surfaces bounding the volume under analysis combined Similarly, 70% of these measurements fell within a range of 19% for both faces combined
The nitrogen concentration was measured in the layer to be less than 0 06 ppm, this upper limit being set by the sensitivity under the conditions used for the measurements
The back surface of the sample was further analysed in the SEM using the MonoCL system for the FE and BE intensity, aquiring data over a 6 x 6 array (36 datapoints) on a 1 mm pitch, with the results shown in Table 2
TABLE 2 - Distribution of FE and BE measurements
(Table Removed)
Thus, 90% of the measurements on the bottom face of the sample fell within a total range about the mean of 25% for the free exciton, 18% for the bound exciton, and 25% for the BE/FE ratio
EXAMPLE 5
A layer was grown by the process described in Example 4 This was then suitably processed and analysed on front and back surfaces of a layer 233 pm thick The volume under analysis was 7 0 mm3
The boron concentration was determined to be 0 34 ppm in the top face, 0 29 ppm in the bottom face, with a average of 0 32 ppm The percentage volume of the material conforming to a particular range of concentrations about the mean were thus determined to be as shown in Table 3
TABLE 3 - Distribution SIMS B measurements

(Table Removed)
The nitrogen concentration was measured in the layer to be less than 0 03 ppm, this upper limit being set by the sensitivity under the conditions used for the measurements
The front and back surfaces of the sample were further analysed in the SEM using the MonoCL system for the FE and BE intensity, aquirmg data over a 6x6 array (36 datapoints) on a 1 mm pitch with the results shown in Table 4
TABLE 4 - Distribution of FE and BE measurements
(Table Removed)
Using the top and bottom major faces of the layer as two representitive surfaces, this shows that 90% of the measurements taken for the bound exciton, free exciton, and BE/FE ratio all fall within a spread of substantially less than 30% about the mean
EXAMPLE 6
A layer was grown by the process described in Example 4 This was then suitably processed and analysed on both front and back surfaces of a layer 538 pm thick The volume under analysis was 16 1 mm3
The boron concentration was determined to be 0 52 ppm in the front surface, 0 34 ppm in the back surface, with a average of 0 43 ppm 70% of the volume of this layer was determined to lie in the range of -23 3 to +23 4 of the mean, a total range of 46 7%
SIMS mapping for boron was then repeated on the growth face with a resolution of less than 30 µm, to further demonstrate the local uniformity of boron uptake, with the results shown in Table 5 below Analysis for elements other than carbon showed no impurities above a detection limit of 0 5 ppm
The nitrogen concentration was measured in the layer to be less than 0 03 ppm, this upper limit being set by the sensitivity under the conditions used for the measurements
The front and back surfaces of the sample were further analysed in the SEM using the MonoCL system for the FE and BE intensity, aquinng data over a 6 x 6 array (36 datapoints) on a 1 mm pitch, with the results shown in Table 5
TABLE 5 - Distribution of B concentration and FE and BE measurements
(Table Removed)
1SIMS, This layer was also mapped using IR absorption over an area of 5 x 5 mm (36 datapoints) on a 1 mm pitch to measure the variation in uncompensated boron 90% of the measurements fell within a full range of 34% about the mean value,
The Raman/photoluminescence spectrum of the plate was measured at 77 K, using argon ion laser light at 514 nm The spectrum was dominated by the diamond Raman line at approx 1332 cm"1 which has a line width (FWHM) of 1 6 cm-1 The zero-phonon lines at 575 nm and 637 nm were below detection, giving a maximum value to the ratio of their respective peak intensities to the Raman peak intensity of 1 1000
EXAMPLE 7
A layer was grown by the process described in Example 4 This was then processed into a layer 818 µm thick and mapped using IR absorption over an area of 5 x 5 mm (36 datapoints) on a 1 mm pitch to measure the variation in uncompensated B 90% of the measurements fell within a full range of 13% about the mean value









We claim:
1. A layer of single crystal boron doped diamond produced by CVD wherein the total boron
concentration is uniform, with a variation over the majority volume which is less than 50%,
measured with a lateral resolution at each measurement point of less than 50µm, wherein the
majority volume represents at least 70% of the total volume of the layer, and wherein the layer
has at least one of the following characteristics (i) to (iii):
(i) the layer is formed from a single growth sector,
(ii) the layer thickness exceeds 100 µm, and
(iii) the volume of the layer exceeds 1 mm3.
2. A diamond layer as claimed in claim 1, wherein the variation over the majority volume is less than 20%.
3. A diamond layer as claimed in claim 1 or claim 2, wherein the variation is measured with a lateral resolution at each measurement point of less than 30 µm.
4. A diamond layer as claimed in any one of the preceding claims, wherein the majority volume of the layer contains an uncompensated boron concentration greater than 1 x 10 atoms/cm3 and less than 1 x 1020 atoms/cm3.
5. A diamond layer as claimed in any one of claims 1 to 3, wherein the majority volume of the layer contains an uncompensated boron concentration greater than 1 x 1015 atoms/cm3 and less than 2 x 1019 atoms/cm3.
6. A diamond layer as claimed in any one of claims 1 to 3, wherein the majority volume of the layer contains an uncompensated boron concentration greater than 5x10 atoms/cm and less than 2 x 1018 atoms/cm3.
7. A diamond layer as claimed in any one of the preceding claims, which has a hole
mobility (µh) measured at 300K which exceeds
for Nh not exceeding 8 x1015 atoms/cm
(Equation (1)
(Equation Removed)
for Nh greater than 8 x 1015 atoms/cm3
(Equation (2)
where Nh is the concentration of holes, and G has a value greater than 1.1.
y
8. A diamond layer as claimed in claim 7, wherein G has a value greater than 1.4.
9. A diamond layer as claimed in claim 7, wherein G has a value greater than 1.7.
10. A diamond layer as claimed in claim 7, wherein G has a value greater than 2.
11. A diamond layer as claimed in any one of the preceding claims, which has low or absent luminescent features at 575 and 637nm, relating to N-V centres.
12. A diamond layer as claimed in any one of claims 1 to 10, wherein the ratio of each of the integrated nitrogen vacancy centre zero-phonon lines at 575 nm and 637 nm with the integrated intensity of the diamond Raman line at 1332 cm-1 when measured at 77 K with 514 nm Ar ion laser excitation, is less than 1/50.
13. A diamond layer as claimed in claim 12, wherein the ratio is less than 1/100.
14. A diamond layer as claimed in claim 12, wherein the ratio is less than 1/300.
15. A diamond layer as claimed in any one of the preceding claims, which has a Raman line width as measured at 300 K of less than 4 cm"1 FWHIW under 514 nm Ar ion excitation.
16. A diamond layer as claimed in claim 15, wherein the Raman line width is less than 3 cm'1 FWHW.
17. A diamond layer as claimed in claim 15, wherein the Raman line width is less than 2.5 cm-1 FWHW.
18. A diamond layer as claimed in any one of the preceding claims, wherein the frequency distribution of uncompensated boron measurements taken by FTIR over a representative sample taken from the layer is such that 90% of the measurements vary by less than 50% of the mean.
19. A diamond layer as claimed in any one of claims 1 to 17, wherein the frequency distribution of uncompensated boron measurements taken by FTIR over a representative sample taken from the layer is such that 90% of the measurements vary by less than 30%) of the mean.
20. A diamond layer as claimed in any one of the preceding claims, wherein the frequency distribution of the BE taken over any representative surface of the layer or a sample taken from the Jayer is such that 90% of the measurements vary by less than 50% of the mean.
21. A diamond layer as claimed in any one of claims 1 to 19, wherein the frequency distribution of the BE taken over any representative surface of the layer or a sample taken from the layer is such that 90% of the measurements vary by less than 30% of the mean.
22. A diamond layer as claimed in any one of the preceding claims, wherein the frequency distribution of FE measurements taken over any representative surface of the layer or sample taken from the layer is such that 90% of the measurements vary by less than 50% of the mean.
23. A diamond layer as claimed in any one of claims 1 to 21, wherein the frequency distribution of. FE measurements taken over any representative surface of the layer or sample taken from the layer is such that 90% of the measurements vary by less than 30% of the mean.
24. A diamond layer as claimed in any one of the preceding claims, wherein the majority volume represents greater than 85% of the total volume of the layer.
25. A diamond layer as claimed in any one of claims 1 to 23, wherein the majority volume represents greater than 95% of the total volume of the layer.
26. A diamond layer as claimed in any one of the preceding claims, wherein the layer is formed from a single growth sector which is one of the {100}, the {113}, the {111} and the {110} sectors.
27. A diamond layer as claimed in any one of the preceding claims, which has a thickness exceeding 500 µm.
28. A diamond layer as claimed in any one of the preceding claims, which has a volume exceeding 3 mm3.
29. A diamond layer as claimed in any one of claims 1 to 27, Which has a volume exceeding 10mm3.
30. A diamond layer as claimed in any one of the preceding claims, which further contains nitrogen as a dopant.
31. A diamond layer as claimed in claim 30, wherein nitrogen concentration is no greater than 1/S that of the boron concentration.
32. A diamond layer as claimed in claim 30, which contains a nitrogen concentration of less than 1/50 that of the boron concentration.
33. A diamond body in which a diamond layer as claimed in any one of the preceding claims,
forms a layer or region thereof and an element produced therefrom.
34. A method of producing a layer of single crystal boron doped diamond including the steps of
providing a diamond substrate having a surface which is substantially free of crystal defects,
providing a source gas, such source gas including a source of boron, dissociating the source gas
and allowing homoepitaxial diamond growth on the surface which is substantially free of crystal
defects.
35. A method as claimed in claim 34, wherein the layer of single crystal boron doped diamond is that defined in any one of claims 1 to 32.
36. A method as claimed in claim 34 or claim 35, wherein the source gas has nitrogen added to it in an amount suitable to control the morphology developed by the growing single crystal diamond.
37. A method as claimed in claim 36, wherein the nitrogen addition to the source gas is greater than 0,5 ppm and less than 10000 ppm.
38. A method as claimed in claim 36, wherein the nitrogen addition to the source gas is
greater than 1 ppm and less than 1000 ppm.
39. A method as claimed in claim 36, wherein the nitrogen addition to the source gas is greater than 3 ppm and less than 200 ppm.
40. A method as claimed in any one of claims 34 to 39, wherein the density of surface etch features related to defects on the surface on which diamond growth occurs is below 5x10 /mm .
41. A method as claimed in any one of claims 34 to 39, wherein the density of surface etch features related to defects on the surface on which diamond growth occurs is below 102/mm2.
42. A method as claimed in any one of claims 34 to 41, wherein the surface on which diamond growth occurs is subjected to a plasma etch prior to diamond growth.
43. A method as claimed in any one of claims 34 to 42, wherein the diamond growth occurs on a {100), (110), {113} or {111) surface.
44. A method as claimed in any one of claims 36 to 43, wherein the boron source is B2H6.


Documents:

1650-delnp-2004-Abstract-(24-11-2010).pdf

1650-delnp-2004-abstract.pdf

1650-DELNP-2004-Claims-(17-06-2011).pdf

1650-delnp-2004-Claims-(24-11-2010).pdf

1650-delnp-2004-claims.pdf

1650-DELNP-2004-Correspondence Others-(17-06-2011).pdf

1650-delnp-2004-Correspondence Others-(23-06-2011).pdf

1650-delnp-2004-Correspondence-Others-(24-11-2010).pdf

1650-delnp-2004-correspondence-others.pdf

1650-DELNP-2004-Description (Complete)-(17-06-2011).pdf

1650-delnp-2004-description (complete).pdf

1650-DELNP-2004-Form-1-(17-06-2011).pdf

1650-delnp-2004-Form-1-(24-11-2010).pdf

1650-delnp-2004-form-1.pdf

1650-delnp-2004-form-18.pdf

1650-DELNP-2004-Form-2-(17-06-2011).pdf

1650-delnp-2004-Form-2-(24-11-2010).pdf

1650-delnp-2004-form-2.pdf

1650-DELNP-2004-Form-3-(17-06-2011).pdf

1650-delnp-2004-Form-3-(24-11-2010).pdf

1650-delnp-2004-form-3.pdf

1650-delnp-2004-form-5.pdf

1650-delnp-2004-GPA-(24-11-2010).pdf

1650-delnp-2004-gpa.pdf

1650-delnp-2004-Petition 137-(24-11-2010).pdf


Patent Number 249195
Indian Patent Application Number 1650/DELNP/2004
PG Journal Number 41/2011
Publication Date 14-Oct-2011
Grant Date 10-Oct-2011
Date of Filing 11-Jun-2004
Name of Patentee ELEMENT SIX LIMITED
Applicant Address ISLE OF MAN FREEPORT, BALLASALLA, ISLE OF MAN IM99 6AQ, U.K.
Inventors:
# Inventor's Name Inventor's Address
1 GEOFFREY, ALAN SCARSBROOK, 40 CAVENDISH MEAD, SUNNINGHILL, ASCOT, BERKSHIRE SL5 9TD U.K.
2 PHILIP, MAURICE MARTINEAU, LITTLEWICK END, CORONATION ROAD, LITTLEWICK GREEN, BERKSHIRE SL6 3RA U.K.
3 DANIEL, JAMES TWITCHEN, 10 PARK DRIVE, SUNNINGDALE, BERKSHIRE SL5 0BD U.K.
4 ANDREW, JOHN WHITEHEAD, 60 CHEYLESMORE DRIVE, FRIMLEY, CAMBERLEY, SURREY GU16 9BW U.K.
5 MICHAEL, ANDREW COOPER, 28 CLIFTON ROAD, WOKINGHAM, BERKSHIRE U.K.
6 BÄRBEL, SUSANNE, CHARLOTTE DORN, 11 SLAIDBURN GREEN, FOREST PARK, BRACKNELL, BERKSHIRE RG12 0WGU.K.
PCT International Classification Number C30B 25/10
PCT International Application Number PCT/IB02/05324
PCT International Filing date 2002-12-13
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 0130005.2 2001-12-14 U.K.