Method and apparatus for wafer level prediction of thin oxide re

Details Method and apparatus for wafer level prediction of thin oxide re Method and apparatus for wafer level prediction of thin oxide re

1995-01-20

1996-08-20

Karlsen, Ernest F.

Electricity: measuring and testing

Fault detecting in electric circuits and of electric components

Of individual circuit component or element

324769, 437 8, G01R 3126, H01L 2166

Patent

active

055482244

ABSTRACT:
An IC wafer containing thin oxide is fabricated with at least one pair of antenna structures having identical antenna ratio A.sub.R but different antenna plate areas. Each antenna structure includes connected-together conductive plate regions, one plate formed over thick field oxide and the other plate formed over thin oxide on the IC. Because weak oxide defects occur somewhat uniformly throughout the thin oxide, a larger antenna structure will overlie more weak oxide defects than will a smaller antenna structure. If wafer test leakage current across the larger antenna structure exceeds leakage current across the smaller antenna structure, weak oxide is indicated because the defect is area dependent. By contrast, charge-induced damage is substantially independent of the area of the antenna plates. Because the A.sub.R ratios are constant, charge density is constant in the antenna structure portions overlying the thin oxide. If test leakage current on the wafer is substantially the same for each antenna structure, charge-damaged oxide is indicated because the damage is not area dependent. If desired, test MOS devices may be fabricated whose gates are the plates formed over the thin oxide. Defects in the thin (gate) oxide may be identified by examining the characteristics of the test MOS devices.

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"How Plasma Etching Damages Thin Gate Oxides," Calvin T. Gabriel, VLSI Technology, Inc. and James P. McVittie, Stanford Univ., Jun. 1992, Solid State Technogy. p. 81-87.

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