Browse Prior Art Database

Prevention of Autodoping

IP.com Disclosure Number: IPCOM000079250D
Original Publication Date: 1973-Jun-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Beyer, KD: AUTHOR [+2]

Abstract

Diffusions into a semiconductor can be made by depositing a doped SiO(2) layer over the surface of the device, forming by photolithographic techniques the doped oxide into islands overlying the desired diffused regions, and subsequently heating to drive the impurity into the semiconductor. This method has the advantage of high-optical resolution, but the disadvantage of high-leakage currents between the diffused regions resulting from out-diffusion of the doped oxide islands.

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Prevention of Autodoping

Diffusions into a semiconductor can be made by depositing a doped SiO(2) layer over the surface of the device, forming by photolithographic techniques the doped oxide into islands overlying the desired diffused regions, and subsequently heating to drive the impurity into the semiconductor. This method has the advantage of high-optical resolution, but the disadvantage of high-leakage currents between the diffused regions resulting from out-diffusion of the doped oxide islands.

In this process a thin SiO(2) layer 10 having a thickness on the order of 1000 angstroms is grown thermally on silicon monocrystalline substrate 12. An arsenic doped oxide layer 14, having a thickness on the order of 2,000 to 5,000 angstroms, is then pyrolytically deposited on layer 10 at approximately 470 degrees C. A layer of photoresist is then deposited on layer 14, exposed, and developed to overlie the desired island pattern 16.

As shown in Fig. 2, the exposed portions of layer 14 are etched leaving islands 18 of arsenic doped SiO(2), without removing the protective SiO(2) layer between the islands. A drive-in step forms diffused regions 20 beneath islands
18. As shown in Fig. 3, removal of islands 18 and layer 10 produce a body 12 having diffused regions suitable for further processing and deposition of an epitaxial layer, without any leakage between arsenic diffused areas 20.

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