Title of Invention

"PRODUCTION AND METHODOLOGY FOR ELECTRONIC GRADE DI-ISOPROPYL TELLURIDE"

Abstract

The present invention relates to an electronic grade Di-isopropyl telluride (DIPTe) of atleast 99.9999% purity. The present invention also provides a method for preparing an electronic grade di-isopropyl telluride (DIPTe) of atleast 99.9999% purity comprising: (a) reduction of elemental tellurium with sodium borohydride; (b) reacting of the resulting monotelluride with isopropylbromide; (c) followed by extraction of DIPTe. The Di-isopropyl telluride (DIPTe) formed by the method of present invention is electronic grade and has a high purity of atleast 99.9999%. The Di-isopropyl telluride (DIPTe) is employed as the preferred precursor for growing of II-VI compound semiconductors.

Full Text

FIELD OF INVENTION: The invention relates to an electronic grade Di-isopropyl telluride (DIPTe) of atleast 99.9999% purity. The invention furhter relates to a process for preparation of an electronic grade Di-isopropyl telluride (DIPTe) of atleast 99.9999% purity. By reduction of elemental tellurium with sodium borohydride, reacting of the resulting monotelluride with isopropylbromide followed by extraction of DIPTe. BACKGROUND OF INVENTION: From group II - VI of periodic table, semiconductor compound materials such as cadmium telluride, cadmium mercury telluride are useful as photo conductors for infrared heat sensors in automobile engines, solar cells, infrared detectors for night vision devices and heat seeking devices. Metal organic chemical vapor deposition (MOCVD) is the technique, which is commonly employed for the deposition of thin films of compound semiconductors on to a substrate such as silicon. MOCVD technique is also being used in electronic industries for coating or doping a substrate. The important criteria for effective reagent i.e. precursor to be used in MOCVD are the volatility of the precursor, clear decomposition without rendering impurities into the grown film. The electrical properties of the film, depends upon the purity of the precursors. For the preparation of compound semiconductors by MOCVD method the precursors of purity better than 99.999% is required. US 5312983 relates to organometallic tellurium compounds useful in chemical vapor deposition process and teaches novel tellurium compounds of the formula:TeR1R2, wherein R1 is fluorinated alkyl having the formula CnF(2n+1).xHx where n may range from 1 to 6 and x may range from 0 to 2n and R2 is selected from the group consisting of alkyls having 2 to 6 carbon atoms, cyclopentadienyl, benzyl, alpha-methylbenzyl and bis (alpha-methyl)benzyl. The novel tellurium reagents are useful as source for organometallic vapor deposition process, particularly the MOCVD fabrication of II-IV semiconductor metals such as HgxCd1_xTe. The compounds are synthesized by high yield ligand exchange reactions between Te(RO2 and Te(R2)2. US 5456207 refers to tri isopropylindium di-isopropyl telluride adduct {(CH3)2CH}3ln:Te{CH(CH3)2}2 which is synthesized and used as universal n type dopant for both II/VI semiconductor materials as well as III/V semiconductor materials disclosed. This dopant precursor is particularly suited for indium doping of II/V semiconductor materials at low carrier concentrations down to 1014 cm-3 and does not exhibit an appreciable memory effect. The prior art do not produces Di-isopropyl telluride of purity of upto 99.9999%. OBJECT OF INVENTION: Primary object of the invention is to produce Di-isopropyl telluride of electronic grade. Another objective of the present invention is to produce Di-isopropyl telluride purity level i.e atleast 99.9999%. Further objective of the present inventi6n is to provide a process for preparation of Di-isopropyl telluride of electronic grade. Further objective of the present invention is to provide Di-isopropyl telluride of electronic grade for use in growing of II-VI compound semiconductors. STATEMENT OF INVENTION: According to one aspect of present invention, there is provided an electronic grade Di-isopropyl teUuride (DIPTe) of atleast 99.9999% purity. Another aspect of the present invention is to provide a process for preparing an electronic grade di-isopropyl telluride (DIPTe) of atleast 99.9999% purity comprising the following steps: (a) adding finely grounded tellurium in a solvent to form a slurry; (b) reducing tellurium slurry obtained in step (a) with sodium borohydride, in presence of sodium hydroxide, maintaining the temperature from 85-90 degree C; (c) stirring the reaction mixture obtained in step (b) to obtain di-sodium di-telluride followed by refluxing; (d) cooling the reaction mixture obtained in step (c) to 0 degree C; and adding isopropyl bromide; (e) heating the reaction mixture of step (d) to 60 degree C with constant stirring for atleast 6 hours in the inert gas atmosphere till the completion of the reaction between disodium telluride and isopropyl bromide; (f) extracting oily layer from the reaction mixture of step (e) with diethyl ether; (g) drying the ethereal layer of step (f) over anhydrous sodium sulphate, followed by removing diethyl ether and excess di-isopropyl bromide are removed by vacuum filtration and recovering yellow oily crude layer as filtrand; (h) purifying di-isopropyl telluride by fractional vacuum distillation of the crude layer of step (g). SUMMARY: The invention relates to An electronic grade Di-isopropyl telluride (DIPTe) of atleast 99.9999% purity. The invention further relates to a process for preparation of an electronic grade Di-isopropyl telluride (DIPTe) of atleast 99.9999% purity. By reduction of elemental tellurium with sodium borohydride, reacting of the resulting monotelluride with isopropylbromide followed by extraction of DIPTe. DESCRIPTION OF INVENTION: Di-isopropyl telluride (DIPTe) is synthesized by reducing tellurium metal to Te2- followed be subsequent reaction with isopropyl bromide. The synthesis of DIPTe is optimized in such a way so that the formation of Di-isopropyl ditelluride (DEPDTe) is avoided. Distillation of the product mixture under reduced pressure yield pure DIPTe. Tellurium slurry is prepared by adding finely divided tellurium powder in a solvent. The solvent is selected from isopropyl alcohol and diethyl ether and the kind. Solvents are purified by conventional procedures in quartz assemblies under argon atmosphere. A three necked flask equipped with a gas inlet, double wall cooled condenser and pressure equalizing funnel is flame dried and flushed with argon gas. Tellurium slurry is taken in the reaction flask and argon gas is bubbled through it to create inert atmosphere. A freshly prepared sodium hydroxide is added into the slurry of tellurium in the reaction flask followed by the addition of a solution of sodium borohydride. The temperature rises to 85 to 90 degree C accompanied with evolution of gas. The temperature is maintained preferably at 90 degree C by an oil bath. Sodium hydroxide maintains the pH of the reaction mixture. The reaction mixture should be basic in nature and pH from 8 to 10 is maintained. Sodium borohydride solution is prepared in degassed water; and is added slowly to the reaction mixture with constant stirring. The slurry of gray tellurium starts turning purple being the characteristic of disodium ditelluride of the formula Na2Te2. When the evolution of gas stops the remaining half of sodium borohydride solution is added drop wise. The reaction mixture is re-fluxed for more than 24 hours at 90 degree C. At this stage the whole of the tellurium slurry is concentrated and becomes colorless indicating the formation of disodium telluride Na2Te. The reaction mixture is cooled to 0 degree C and to this is added isopropyl bromide drop wise with constant stirring. The reaction mixture turns yellow as the alkylation proceed. The reaction mixture is heated to 60 degree C with continuous stirring for more than 6 hours in inert atmosphere to complete the reaction. The yellow oily layer is separated from the aqueous layer by extracting with diethyl ether. The ethereal layer is dried over anhydrous sodium sulfate and diethyl ether and excess isopropyl bromide are removed by vacuum filtration yellow crude layer is recovered as filtrand. DIPTe is then purified by fractional vacuum distillation of crude layer. Organotellurium compounds such as dimethyl telluride, diethyl telluride, diisopropyl telluride, diallyl telluride and methyl allyl telluride are used as precursors for MOVPE growth of II-VI compound semiconductors. Diisopropyl telluride (DIPTe) is employed as the preferred precursor for achieving the low temperature growth of CdHgTe by MOVPE. DIPTe is used to grow II-VI compound semiconductors by MOVPE. EXAMPLE Tellurium slurry is prepared by adding finely divided tellurium powder in isopropanol. Solvent is purified by conventional procedures in quartz assemblies under argon atmosphere. A three necked flask equipped with a gas inlet, double wall cooled condenser and pressure equalizing funnel is flame dried and flushed with argon gas. Tellurium slurry is taken in the reaction flask and argon gas is bubbled through it to create inert atmosphere. A freshly prepared sodium hydroxide is added into the slurry of tellurium in the reaction flask followed by the addition of a solution of sodium borohydride. The temperature rises to 90 degree C accompanied with evolution of gas. The temperature is maintained by an oil bath. Sodium borohydride solution is prepared in degassed water; and is added slowly to the reaction mixture with constant stirring. The slurry of gray tellurium starts turning purple being the characteristic of disodium ditelluride of the formula Na2Te2. When the evolution of gas stops the remaining half of sodium borohydride solution is added drop wise. The reaction mixture is re-fluxed for 24 hours at 90 degree C. At this stage the whole of the tellurium slurry is concentrated and becomes colorless indicating the formation of disodium telluride Na2Te. The reaction mixture is cooled to 0 degree C and to this is added isopropyl bromide drop wise with constant stirring. The reaction mixture turns yellow as the alkylation proceed. The reaction mixture is heated to 60 degree C with continuous stirring for 6 hours in inert atmosphere to complete the reaction. The yellow oily layer is separated from the aqueous layer by extracting with diethyl ether. The ethereal layer is dried over anhydrous sodium sulfate and diethyl ether and excess isopropyl bromide are removed by vacuum filtration yellow crude layer is obtained as filtrand. DIPTe is then purified by fractional vacuum distillation of crude layer. DIPTe of 99.999902% purity is obtained. Trace Elemental Analysis of DIPTe by ICP-MS (Table Removed) WE CLAIM: 1. A process for preparing an electronic grade di-isopropyl telluride (DIPTe) of at least 99.9999% purity comprising the following steps: (a) adding finely grounded tellurium in a solvent to form a slurry; (b) reducing tellurium slurry obtained in step (a) with sodium borohydride, in presence of sodium hydroxide, maintaining a temperature from 85-90 degree C; (c) stirring the reaction mixture obtained in step (b) to obtain di-sodium di-telluride followed by refluxing; (d) cooling the reaction mixture obtained in step (c) to 0 degree C; and adding isopropyl bromide; (e) heating the reaction mixture ei obtained in step (d) to 60 degree C with constant stirring for at least 6 hours in the inert gas atmosphere till the completion of the reaction between disodium telluride and isopropyl bromide; (f) extracting oily layer from the reaction mixture el obtained in step (e) with diethyl ether; (g) drying the ethereal oily layer of step (f) over anhydrous sodium sulphate, followed by removing diethyl ether and removing excess di-isopropyl bromide by vacuum filtration and recovering yellow oily crude layer as filtrand; (h) purifying di-isopropyl telluride by fractional vacuum distillation of the crude layer of step (g). 2. A process for preparing an electronic grade di-isopropyl telluride of at least 99.9999% purity as claimed in claim 1, wherein solution of sodium borohydride is prepared in degassed water. 3. A process for preparing an electronic grade di-isopropyl telluride of at least 99.9999% purity as claimed in claim 1, wherein the reaction mixture in step (c) is refluxed for at least 24 hours. 4. A process for preparing an electronic grade di-isopropyl telluride of at least 99.9999% purity as claimed in claim 1, wherein said solvent is an organic solvent selected from a group consisting of isopropanol and Diethyl ether. 5. A process for preparing an electronic grade di-isopropyl telluride of at least 99.9999% purity as claimed in claim 1, wherein the temperature of 85 - 90 degree C is maintained by an oil bath. 6. A process for preparing an electric grade di-isopropyl telluride of at least 99.9999% purity as claimed in claim 1, wherein pH of the reaction mixture is maintained from 8 to 10. 7. A process for preparing an electric grade di-isopropyl telluride of at least 99.9999% purity as claimed in any of the preceding claims 1-6, as and when used for preparation of an electric grade di-isopropyl telluride of at least 99.9999% purity. 8. A process for preparing an electric grade di-isopropyl telluride of at least 99.9999% purity as claimed in any of the preceding claims 1-6, as and when used for preparation of an electric grade di-isopropyl telluride of at least 99.9999% purity for use in growing II-VI compound semiconductors. Dated this IS"" day of April, 2007 The Controller of Patents (Ramesh C. Dhawan) The Patent Office, Patent Agent No. IN/PA-340 New Delhi of LALL LAHIRI & SALHOTRA AGENTS FOR THE APPLICANT

Documents:

822-del-2007-abstract.pdf

822-del-2007-Claims-(21-08-2013).pdf

822-del-2007-claims.pdf

822-del-2007-Correspondence Others-(21-08-2013).pdf

822-DEL-2007-Correspondence-Others.pdf

822-del-2007-description (complete).pdf

822-del-2007-description (provisional).pdf

822-DEL-2007-Form-1.pdf

822-del-2007-form-18.pdf

822-DEL-2007-Form-2.pdf

822-del-2007-form-26.pdf

822-DEL-2007-Form-3.pdf

822-del-2007-form-5.pdf

822-del-2007-Petition-137-(21-08-2013).pdf