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Improving the Dielectric Strength of the Gate Oxide of a Field Effect Transistor

IP.com Disclosure Number: IPCOM000081609D
Original Publication Date: 1974-Jul-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Klepner, SP: AUTHOR [+2]

Abstract

Silicon nitride is commonly used as an oxidation mask for the selective oxidation of a silicon substrate in the manufacture of field-effect transistors. In the usual practice, the nitride mask is used with a thin oxide layer underneath to prevent dislocation formation in the substrate, and to prevent the formation of gate oxides having low-dielectric breakdown voltages. However, the thin oxide layer causes irregularities in the shape of the oxidized layer, which lead to undesirable device characteristics.

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Improving the Dielectric Strength of the Gate Oxide of a Field Effect Transistor

Silicon nitride is commonly used as an oxidation mask for the selective oxidation of a silicon substrate in the manufacture of field-effect transistors. In the usual practice, the nitride mask is used with a thin oxide layer underneath to prevent dislocation formation in the substrate, and to prevent the formation of gate oxides having low-dielectric breakdown voltages. However, the thin oxide layer causes irregularities in the shape of the oxidized layer, which lead to undesirable device characteristics.

In the present process, the use of the oxide underlayer is obviated by using sputtered silicon nitride directly on the silicon surface for use as the oxidation mask. Sputtered silicon nitride has a low-intrinsic stress which does not cause dislocation formation in the substrate. (Chemically vapor deposited nitride may also be used if thin enough to avoid dislocation formation.)

When the sputtered nitride mask is removed after the oxidation step, a light etch is employed to remove a thin layer of silicon. In a subsequent step, when the gate oxide is grown upon the silicon surface its dielectric breakdown strength is improved. The etch composition is typically one part HF, two parts HAC and 200 parts HNO(3).

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