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Forming Deep P+ Diffusions in a Semiconductor Body

IP.com Disclosure Number: IPCOM000081639D
Original Publication Date: 1974-Jul-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Aboaf, JA: AUTHOR [+3]

Abstract

This process is capable of producing deep P+ diffusions suitable for use as isolating pockets in complementary metal-oxide semiconductor (MOS) devices. The use of deep pockets results in a larger base width which minimizes the silicon-controlled rectifier (:SCR) problems associated with such devices. This process for forming deep diffusions in a silicon semiconductor, is based on the use of aluminum as an impurity for forming the P-type pocket. Aluminum has a higher diffusivity than boron and when a drive-in is made after removing the aluminum dopant source, an N-type skin can be formed.

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Forming Deep P+ Diffusions in a Semiconductor Body

This process is capable of producing deep P+ diffusions suitable for use as isolating pockets in complementary metal-oxide semiconductor (MOS) devices. The use of deep pockets results in a larger base width which minimizes the silicon-controlled rectifier (:SCR) problems associated with such devices. This process for forming deep diffusions in a silicon semiconductor, is based on the use of aluminum as an impurity for forming the P-type pocket. Aluminum has a higher diffusivity than boron and when a drive-in is made after removing the aluminum dopant source, an N-type skin can be formed.

In this process, a masking layer of a thermal oxide is formed on an N-type silicon wafer 10 by conventional techniques. The area of the deep P-type diffused region is delineated in the thermal oxide 12, by conventional photoresist and etching techniques. As shown in Fig. 1, an Al(2) 0(3) blanket layer 16 is deposited on the surface of semiconductor body 10 over layer 12 and in direct contact with body 10 in opening 14. The structure is then heated for 30 minutes at approximately 1100 degrees C, wherein the aluminum penetration depth of approximately three microns is obtained resulting in region 18.

It is also possible to replace the Al(2)O(3) (layer 16) by a layer of pyrolytic SiO(2) 20 and a successive Al(2)O(3) layer 22 which is formed on body 10. The use of SiO(2) layer 20 avoids pitting that could occur if very high temperatu...