| Title of Invention | A METHOD OF FABRICATING ELECTRICAL CONTACTS |
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| Abstract | This invention relates to a method of fabricating electrical contacts comprising preparing a solution of atleast a salt of nickel, warming the solution to a temperature in the range of 90 to 95°C and preparing an electrolytic bath therewith, subjecting a substrate surface to a pre-treatment with a sensitiser and activator, placing the substrate in the bath and subjecting the same to electrolytic deposition of NixPy layer thereon, where x= 1 to 0.88, y= 0 to 0.12. |
| Full Text | FIELD OF INVENTION This invention relates to a method of fabricating electrical contacts and the electrical contacts produced thereby. This invention further relates to a method of fabricating electrical contacts with the compound semi-conductor formed from at least one metal selected from class III to V of the periodic table. BACKGROUND OF INVENTION The difficulties in making good ohmic contacts to the class III-V compounds of semi-conductor such as InP, GaAs and InGaAs are well known. These materials on the other hand are very important for the fabrication of various electronic devices in general and thermo photovoltaic cells in particular. As a consequence, utilisation of such material for various applications depends upon the ability to make low resistance ohmic contact on them. Ni and its compound are well known contacting material to the above semi- conductors. However, methods for deposition of these materials are difficult. Normal method is to deposit these materials by vacuum technique or radio frequency technique. However, each of the above methods has their own limitations. OBJECTS OF THE INVENTION It is therefore an object of this invention to propose a method of fabricating electrical contacts using a simple technique. It is a further object of this invention to propose propose a method of fabricating electrical contacts using a simple technique which is cost-effective. At the outset of the description which follows, it is to be understood that the ensuing description only illustrates a particular form of this invention. However, At the outset of the description which follows, it is to be understood that the ensuing description only illustrates a particular form of this invention. However, such a particular form is only an exemplary embodiment and the teachings of the invention is not intended to be taken restrictively. BRIEF DESCRIPTION OF INVENTION Thus according to this invention is provided a method of fabricating electrical contacts comprising preparing a solution of atleast a salt of nickel, warming the solution to a temperature in the range of 90 to 95°C and preparing an electrolytic bath therewith, subjecting a substrate surface to a pre-treatment with a sensitiser and activator, placing the substrate in the bath and subjecting the same to electrolytic deposition of NixPy layer thereon, where x= 1 to 0.88, y= 0 to 0.12. This invention further relates to electrical contacts produced by the process. In accordance with this invention, an electroless technique is employed for the deposition of NixPy on semi-conducting substrates like InP, GaAs and InGaAs solution is prepared for the surface treatment of semi-conducting substrates like InP, GaAs, InGaAs, etc. In this electroless technique, a special type of solution bath is prepared. The solution consists of salts of Ni like NiCl2 or MSO4, reducing agent like Na2HPO2, a complexing agent and a stabiliser. The above chemicals are mixed in particular proportion to have the exact solution. The above solution is then warmed to a temperature in the range of 90 to 95°C. The semi-conductor of the above categories is then treated in two other solutions. These are sensitizer and activator. The sensitizer solution is a mixture of salt like SnCl2 and an acid like HCl. Activator is a chemical solution containing a mixture of PdCl2, HCl and H2O. Before deposition of NixPy layer, the substrate surface requires cleaning in cleaning solution to remove contaminations like grease. The substrate is then treated with a sensitizer solution to sensitize the substrate surface. After sensitization, the substrate is activated in activator solution. After activation, the substrate is dipped in plating bath to deposit NixPy coating. Deposition is allowed for 7-10 mins. to have good coating. According to an embodiment of this invention is provided a method of fabricating electrical contacts comprising preparing a solution of atleast a salt of nickel, wanning the solution to a temperature in the range of 65 to 70° C, and preparing an electrolytic bath therewith, subjecting the substrate surface to electroplating for the deposition of NixPy layer thereon. In accordance with the embodiment of the invention, an electroplating technique is employed. The electroplating bath is prepared by mixing the following chemical in particular proportion. The chemicals are NiCl2, NiSO4, NiCO3, H3PO3 and H3PO4. The solution is then warmed to a temperature range of 65-70° C. The substrate is first cleaned to remove contamination like grease. The substrate is then held in a vacuum device and electrical contact is taken out and the substrate is connected to the negative terminal of a d c source. A Ni counter electrode is kept in the plating bath. The counter electrode is connected to the positive terminal of the d c source. A suitable amount of d c electricity is allowed to pass through the substrate and the counter electrode. As a result, a NixPy layer is deposited over the substrate. The strength of the current is fixed according to the % of P to be incorporated into the deposit According to the present invention for deposition of 10% of P, a current density of 1000-1200 A/m2 is required. The substrate is then annealed in air at a temperature in the range of 200-250° C. The annealing enhances the contacting performance. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The invention will now be explained in greater detail with the help of the accompanying drawings wherein Fig.1 is a cross sectional view of a schematic drawing of the preferred embodiment of the semi-con ducting devices normally used; Fig.2 is the schematic diagram for the arrangement for electroplating; Fig.3a is the current voltage characteristics using electroless technique; Fig.3b is the current voltage characteristics using electroplating technique. Fig.1 stands for the device structure those that are generally used. The layer 10 stands for the back metallic layer, the layer 11 stands for semi-conductor like InP or GaAs, the layer 12 stands for InGaAs and layer 13 stands for top metallic contact. WE CLAIM; 1. A method of fabricating electrical contacts comprising preparing a solution of atleast a salt of nickel, warming the solution to a temperature in the range of 90 to 95°C and preparing an electrolytic bath therewith, subjecting a substrate surface to a pre-treatment with a sensitiser and activator, placing the substrate in the bath and subjecting the same to electrolytic deposition of NixPy layer thereon, where x= 1 to 0.88, y= 0 to 0.12. 2. The method as claimed in claim 1 wherein said substrate is a semi- conducting substrate such as Indium phosphide, Gallium arsenide, Indium gallium arsenide and the like. 3. The method as claimed in claim 1, wherein said solution of nickel comprises salts of nickel such as nickel chloride, nickel sulphate, a reducing agent such as nickel hydrogen phosphate a complexing agent and a stabiliser. 4. The method as claimed in claim 1, wherein said sensitizer solution is an aqueous solution of a salt such as tin chloride and an inorganic acid. 5. The method as claimed in claim 1, wherein said activator solution is an aqueous solution of PdCl2 and an inorganic acid. 6. The method as claimed in claim 1, wherein said electroplating bath comprises compounds of nickel such as nickel chloride, nickel sulphate, nickel carbonate and phosphorous and phosphoric acids. 7. The method as claimed in claim 1, wherein said substrate surface is cleaned before electrode position. 8. The method as claimed in claim 1, wherein deposition is conducted for 7 to 10 mlns. 9. The method as claimed in claim 1, wherein for deposition of 1-% of Phosphide, a current density of 1000 to 1200 A/m2 is used. 10. The method as claimed in claim 1, wherein after deposition the substrate is annealed at a temperature in the range of 200 to 250oC. ABSTRACT TITLE: A METHOD OF FABRICATING ELECTRICAL CONTACTS This invention relates to a method of fabricating electrical contacts comprising preparing a solution of atleast a salt of nickel, warming the solution to a temperature in the range of 90 to 95°C and preparing an electrolytic bath therewith, subjecting a substrate surface to a pre-treatment with a sensitiser and activator, placing the substrate in the bath and subjecting the same to electrolytic deposition of NixPy layer thereon, where x= 1 to 0.88, y= 0 to 0.12. |
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363-KOL-2003-(19-03-2012)-CORRESPONDENCE.pdf
363-KOL-2003-(19-03-2012)-FORM-1.pdf
363-KOL-2003-(19-03-2012)-FORM-13.pdf
363-KOL-2003-AMANDE PAGES OF SPECIFICATION.pdf
363-KOL-2003-CORRESPONDENCE 1.1.pdf
363-KOL-2003-CORRESPONDENCE-1.1.pdf
363-KOL-2003-CORRESPONDENCE.pdf
363-kol-2003-correspondence1.2.pdf
363-KOL-2003-DESCRIPTION (COMPLETE).pdf
363-kol-2003-description (provisional).pdf
363-KOL-2003-EXAMINATION REPORT REPLY RECIEVED.pdf
363-KOL-2003-EXAMINATION REPORT-1.1.pdf
363-kol-2003-examination report.pdf
363-KOL-2003-GRANTED-ABSTRACT.pdf
363-KOL-2003-GRANTED-CLAIMS.pdf
363-KOL-2003-GRANTED-DESCRIPTION (COMPLETE).pdf
363-KOL-2003-GRANTED-DRAWINGS.pdf
363-KOL-2003-GRANTED-FORM 1.pdf
363-KOL-2003-GRANTED-FORM 2.pdf
363-KOL-2003-GRANTED-SPECIFICATION.pdf
363-KOL-2003-OTHERS DOCUMENTS 1.1.pdf
363-KOL-2003-REPLY TO EXAMINATION REPORT.pdf
363-kol-2003-specification.pdf
| Patent Number | 254535 | ||||||||
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| Indian Patent Application Number | 363/KOL/2003 | ||||||||
| PG Journal Number | 46/2012 | ||||||||
| Publication Date | 16-Nov-2012 | ||||||||
| Grant Date | 14-Nov-2012 | ||||||||
| Date of Filing | 30-Jun-2003 | ||||||||
| Name of Patentee | BISWAJIT GHOSH | ||||||||
| Applicant Address | PROFESSOR, ENERGY SCIENCE & TECHNOLOGY, SCHOOL OF ENERGY STUDIES, JADAVPUR UNIVERSITY, KOLKATA 700 032, WEST BENGAL, INDIA | ||||||||
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| PCT International Classification Number | H01R 11/00 | ||||||||
| PCT International Application Number | N/A | ||||||||
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