Two-step anisotropic etching process for patterning a layer without penetrating through an underlying thinner layer
US4484979A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 16, 1984 |
| Grant date | Nov 27, 1984 |
| Priority date | — |
| Expiry date | Apr 16, 2004 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S438/978
- WIPO fieldSemiconductors
- WIPO sectorElectrical engineering
Abstract
Patterning of a relatively thick silicon nitride layer coating a relatively thin silicon dioxide layer which coats a major surface of a silicon wafer is accomplished by reactive ion etching, without penetrating through the silicon dioxide layer to the major surface of the silicon wafer, by means of a two-step reactive ion etching procedure using a patterned masking layer. During the first etching step the silicon nitride layer is not completely penetrated; during the second step the nitride layer but not the silicon dioxide layer is completely penetrated. The gas mixture for the first etching step differs from that of the second etching step in accordance with prescription that the ratio of the etch rate of silicon dioxide to that of silicon nitride during the second step is significantly smaller than such ratio during the first step. Preferred gas mixtures are oxygen and CHF.sub.3 in the ratio of about 0.6 to 1.0 for the first etching step and about 9 to 1 for the second etching step. Other systems of layers and wafers can be similarly patterned by means of two-step etching processes using selections of the gas mixtures in accordance with this prescription for the ratios of etch r…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.