Field enhanced tunnel oxide on treated substrates

US4806202A · kind A · utility

Assignee

• Intel Corporation · US

Inventors

• Daniel Tang · Fremont, US
• Himanshu Choksi · Fremont, US
• Simon Wang · Sunnyvale, US
• Simon Tam · Evanston, US

Key dates

• Filing date: Oct 5, 1987
• Grant date: Feb 21, 1989
• Expiry date: Oct 5, 2007

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10S438/964

Abstract

A method for growing tunnel oxides on a specially treated substrate surface. The method comprises steps for roughening the substrate surface to induce low tunneling voltage in the subsequently grown tunnel oxide layer. The tunnel oxide layer is grown in a low temperature steam cycle to further provide enhanced tunneling. The surface treatment comprises the steps of growing a first oxide layer to seal the surface of the substrate followed by growing a second oxide on the first oxide layer. In the preferred embodiment, a plasma etch utilizing an oxide etcher with high energy ion bombardment and an aluminum electrode is utilized to etch through the first and second oxide layers. The aluminum electrode causes sputtered aluminum on the second oxide layer's surface. The sputtered aluminum blocks the anisotropic etching leaving a grass type oxide residue on the substrate surface. The etching continues, overetching into the substrate surface. The grass type oxide residue causes pitting to occur on the substrate surface. This pitting, resulting in sharpened features on the surface, yields enhanced tunneling characteristics for a subsequently grown tunnel oxide layer. The residue is then rem…