Browse Prior Art Database

Silicon Dioxide Step Gauge

IP.com Disclosure Number: IPCOM000096250D
Original Publication Date: 1963-Mar-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Pliskin, WA: AUTHOR

Abstract

This step gauge indicates film thicknesses of the order of a few hundred angstroms to 1. 5 microns. The step gauge has improved stability over barium stearite type gauges and is not destroyed by handling or mild heating.

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Silicon Dioxide Step Gauge

This step gauge indicates film thicknesses of the order of a few hundred angstroms to 1. 5 microns. The step gauge has improved stability over barium stearite type gauges and is not destroyed by handling or mild heating.

The step gauge is fabricated by growing film 20 on substrate 22, typically silicon. Substrate 22 is subjected to a thermal oxidation process to grow film 20 as thick as the thickest step desired in the step gauge. Typically, film 20 is grown by subjecting substrate 22 to a steam atmosphere at approximately 1000 degrees C. Then, a portion 30 of the wafer is covered with a protective coating, such as black wax, photo resist or other coating, which is not affected by an etching. Next, the film on substrate 22 is etched by immersing in an etched solution which etches at a rate consistent with the step thickness difference desired. As an example, a 5. 25% hydrofluoric solution made by mixing 10 cubic centimeters of hydrofluoric acid (49% HF) with 100 cubic centimeters of water etches 4. 3 angstroms per second of the described silicon dioxide film. Thus, fifty-eight seconds exposure etches 250 angstroms of silicon dioxide over the remaining portion of the wafer. If a step of less than 250 angstroms is desired, shorter times or more dilute etching solutions are used. At fifty-eight seconds, the film and substrate are flooded with water to stop etching. Thus, the film has a first step 30 and a second step 32 in it of preselecte...