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Low Mobile Ion Concentration by System Scavenging

IP.com Disclosure Number: IPCOM000088850D
Original Publication Date: 1977-Aug-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Gardiner, J: AUTHOR [+4]

Abstract

A critical parameter in successful field-effect transistor (FET) or charge-coupled device (CCD) processes is maintaining a low mobile ion concentration wherein polycrystalline silicon electrodes are used. Many thin films, including doped polycrystalline Si, are deposited in reactors in which mobile ions, such as Na+, are encountered. Standard techniques, such as HCl purging to reduce the ions, are difficult to use with chemical vapor deposition (CVD) reactors. The temperature of HCl cleaning as well as stripping of protective coatings on the susceptors are examples of the difficulty of using HCl cleaning in CVD systems.

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Low Mobile Ion Concentration by System Scavenging

A critical parameter in successful field-effect transistor (FET) or charge- coupled device (CCD) processes is maintaining a low mobile ion concentration wherein polycrystalline silicon electrodes are used. Many thin films, including doped polycrystalline Si, are deposited in reactors in which mobile ions, such as Na+, are encountered. Standard techniques, such as HCl purging to reduce the ions, are difficult to use with chemical vapor deposition (CVD) reactors. The temperature of HCl cleaning as well as stripping of protective coatings on the susceptors are examples of the difficulty of using HCl cleaning in CVD systems.

Predeposit doped phosphorous silicate glass (PSG) is forned in the CVD reactor prior to the insertion of samples being prepared for doped polycrystalline Si. The PSG will deposit on the susceptor and walls of the reactor, as well as flush the feed system of ions. Any mobile ion impurity will be gettered by the PSG in the system environment. Since polycrystalline silicon lands of highest N type impurity are needed, any system doping of the polycrystalline silicon lands is beneficial.

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