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Electrical Defect Test for Silicon and Aluminum Metal Oxide Semiconductor Process

IP.com Disclosure Number: IPCOM000051917D
Original Publication Date: 1981-Apr-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Geiss, PJ: AUTHOR [+3]

Abstract

The Silicon and Aluminum Metal Oxide Semiconductor (SAMOS) process [IBM J. Res. Develop. 24, 268-282 (May 1980)] employs a polysilicon field shield separated from the silicon substrate by a thin nitrideoxide dual dielectric. This field shield is physically shorted to the silicon substrate with first level metallization. As a result, defects in the dielectric which occur between the field shield and the p-type substrate are inconsequential. Defects in the dielectric which occur in areas where the field shield passes over n-type diffusions, however, short the diffusion to the substrate and render the diffusion inoperative. Defects of this type can be major detractors in defect-limited yield of SAMOS products. Since they are in the silicon-nitride-oxide semiconductor structure, they are known as SNOS defects.

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Electrical Defect Test for Silicon and Aluminum Metal Oxide Semiconductor Process

The Silicon and Aluminum Metal Oxide Semiconductor (SAMOS) process [IBM J. Res. Develop. 24, 268-282 (May 1980)] employs a polysilicon field shield separated from the silicon substrate by a thin nitrideoxide dual dielectric. This field shield is physically shorted to the silicon substrate with first level metallization. As a result, defects in the dielectric which occur between the field shield and the p-type substrate are inconsequential. Defects in the dielectric which occur in areas where the field shield passes over n-type diffusions, however, short the diffusion to the substrate and render the diffusion inoperative. Defects of this type can be major detractors in defect-limited yield of SAMOS products. Since they are in the silicon-nitride-oxide semiconductor structure, they are known as SNOS defects. In this method the polysilicon field shield is used as a defect-monitoring electrode immediately after it is patterned.

lmplementation of the test occurs immediately following the patterning of the polysilicon layer. Since at this point the polysilicon is not shorted to the substrate, there is no need to make electrical contact to diffusions. With the backside of the p-type wafer grounded, a probe is applied to the patterned polysilicon field shield and the SNOS structure is biased by both positive and negative voltages. Leakage current is monitored under each condition. Should a SNOS defect be present between t...