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Improvements to MOS Retention Time Based Tests

IP.com Disclosure Number: IPCOM000042455D
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Goulard, R: AUTHOR [+2]

Abstract

For FET product characterization, semiconductor suppliers have developed different tests, such as the one described in [*]. Another technique is called the MOS retention time process. This process is comprised of the following steps: - Huang cleaning in a HF bath; - oxidation at 1000ŒC; 20 minutes in dry O2, 90 minutes in H2O, 30 minutes in dry O2 followed by an anneal: 1 hour in N2; - dots deposition; - sintering at 450ŒC. Then the electrical tests may take place. For this MOS retention process, the wafers are in specification (yield > 90%) if they have more than 30 ppma of initial oxygen content. However, this test takes into account only the beneficial effect of oxygen, called internal gettering, but not the detrimental effects, such as the nucleation or precipitation of oxygen atoms.

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Improvements to MOS Retention Time Based Tests

For FET product characterization, semiconductor suppliers have developed different tests, such as the one described in [*]. Another technique is called the MOS retention time process. This process is comprised of the following steps: - Huang cleaning in a HF bath; - oxidation at 1000OEC; 20 minutes in dry O2, 90 minutes in H2O, 30 minutes in dry O2 followed by an anneal: 1 hour in N2; - dots deposition; - sintering at 450OEC. Then the electrical tests may take place. For this MOS retention process, the wafers are in specification (yield > 90%) if they have more than 30 ppma of initial oxygen content. However, this test takes into account only the beneficial effect of oxygen, called internal gettering, but not the detrimental effects, such as the nucleation or precipitation of oxygen atoms. For the material supplier, there has been so far no characterization before semiconductor processing takes place in the manufacturing lines which include all the oxygen effects and therefore would be sufficiently representative of wafer behavior during the subsequent semiconductor heat treatments. On the other hand, one problem met in the semiconductor lines is a single cell fail. For wafers with particular characteristics, we have defects formed close to the active face which produce this electrical failure detected on wafers which have either a too high oxygen concentration
([0]>40) or a too high precipitation rate. The aim of this test is to describe a special MOS heat treatment, sufficiently selective to eliminate bad wafers prior to subsequent semiconductor processing. Compared with the standard MOS test, the improvement...