Browse Prior Art Database

Process Monitor

IP.com Disclosure Number: IPCOM000077418D
Original Publication Date: 1972-Jul-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Liles, RE: AUTHOR [+2]

Abstract

Phosphosilicate glass (PSG) is used to improve threshold stability of N channel field-effect transistors. The amount of gate oxide PSG (mole % and thickness) is a critical process. The mole % thickness product of the PSG layer is the important parameter.

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Process Monitor

Phosphosilicate glass (PSG) is used to improve threshold stability of N channel field-effect transistors. The amount of gate oxide PSG (mole % and thickness) is a critical process. The mole % thickness product of the PSG layer is the important parameter.

The amount of PSG removed can be monitored by determining the difference in PSG polarization shift before and after the cleaning step. Only one measurement is required to insure that an adequate amount of PSG is retained.

The required measurement is a flatband voltage shift due to a two minute, 25 degrees C, 4.3 x 10/6/ volts per cm stress on the product thin silicon oxides. A C-V trace measurement is made on any thin oxide capacitor structure available for test on the product wafer. For two minutes a voltage stress of 4.3 x 10/6/ volts per cm is applied to the capacitor structure. The C-V trace is again taken.

The flatband voltage point is determined on each of these traces to give a value for the flatband voltage shift.

A correlation, as shown in the figure, of flatband voltage shift to the mole % phosphorous times thickness of PSG product can be made, by measurements of PSG characteristics on a set of samples. The PSG thickness and mole % of phosphorous could be determined by chemical analysis and ellipsometer measurements on these samples. However, it is not necessary to use complicated analysis and measurements on product wafers, since the mole % phosphorous - PSG thickness product is shown i...