Oxide removal method for improvement of subsequently grown oxides for a twin-tub CMOS process

A method for removing oxide from the surface of a semiconductor body having a thick oxide and an adjoining thin oxide prior to forming a gate oxide for a field effect device, comprising the steps of:

• depositing a photoresist layer;
• subsequent to the photoresist layer depositing step, defining the photoresist layer so as to expose the thick oxide while still covering the thin oxide;
• subsequent to the photoresist layer defining step, etching the thick oxide so that a portion of the thick oxide remains, and has a thickness comparable to that of the thin oxide;
• subsequent to the thick oxide etching step, removing the photoresist layer covering the thin oxide;
• and
• subsequent to the photoresist layer removing step, etching the thin oxide and the remaining portion of the thick oxide without appreciably over-etching the surface of the semiconductor body.

A method for avoiding degradation of a surface of a semiconductor body having a thick oxide layer and an adjoining photoresist-masked first thin oxide layer, comprising the steps of:

• converting the thick oxide into a second thin oxide;
• removing the photoresist subsequent to the thick oxide converting step;
• and
• etching the first and second thin oxides subsequent to the photoresist removing step, wherein the thickness of the first and second thin oxides and the duration of etching are such that appreciable degradation of the surface of the semiconductor body does not occur.

A method for avoiding degradation of a surface of a semiconductor body having a thick oxide layer and an adjoining photoresist-masked first thin oxide layer, comprising the steps of:

• converting the thick oxide into a second thin oxide;
• removing the photoresist subsequent to the thick oxide converting step;
• and
• etching the first and second thin oxides subsequent to the photoresist removing step, wherein the thickness of the first and second thin oxides and the duration of etching are such that the surface of the semiconductor body remains free of appreciable surface micro-roughness.