# US 5,705,025 A · Method for dry etching of a semiconductor substrate

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- Number: US 5,705,025 A
- Document ID: US5705025A
- Status: Granted
- Kind: A
- Application number: 08/539,198
- Filed: 1995-10-04
- Granted: 1998-01-06
- Earliest claimed: 1994-10-04
- Assignees: Siemens Aktiengesellschaft
- Inventors: Ralf Dietrich; Gerhard Franz
- Web page: https://patentgrep.com/patent/US5705025A

## CPC

- G02B 6/1245: {Geodesic lenses}
- Y10S 438/978: forming tapered edges on substrate or adjacent layers
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

A method for dry etching of a semiconductor substrate includes producing convex structures on a surface of a semiconductor wafer by using a suitable masking and a suitable etchant. A thick photoresist layer is applied to a semiconductor wafer and structured. The structured photoresist layer is liquified by the influence of temperature to produce a spherical structure and is then hardened as an etchable masking. The semiconductor wafer structured with the photoresist layer is etched in plasma at etching speeds being similar for the semiconductor material and the photoresist, for transferring a convex structure of the photoresist layer to the semiconductor wafer, during etching down of the photoresist layer.

## Claims

### Claim 1

In a method for dry etching of a semiconductor substrate, which includes producing a convex structure on a surface of a semiconductor wafer by using a suitable mask and a suitable etchant, the improvement which comprises:
applying a thick photoresist layer to a semiconductor wafer;
structuring the photoresist layer;
liquefying the structured photoresist layer by the influence of temperature to produce a spherical structure and then hardening the spherical structure as an etchable masking;
etching the semiconductor wafer structured with the photoresist layer in plasma at etching speeds being similar for the semiconductor material and the photoresist, for transferring a convex structure of the photoresist layer to the semiconductor wafer, during etching down of the photoresist layer; and
applying a dielectric antireflective layer to the semiconductor wafer having the convex structure, whereby the antireflective layer covers the convex structure of the semiconductor wafer.

### Claim 2 (depends on 1)

The method according to claim 1, which comprises applying the photoresist layer to a semiconductor material selected from the group consisting of silicon and III/V semiconductor material.

### Claim 3 (depends on 1)

The method according to claim 1, which comprises applying the photoresist layer to the semiconductor wafer in a thickness of approximately 10 .mu.m to 60 .mu.m.

### Claim 4 (depends on 1)

The method according to claim 1, which comprises etching with a gas selected from the group consisting of SF.sub.6, O.sub.2, He and CHF.sub.3 being used as etching gases.

### Claim 5 (depends on 1)

The method according to claim 1, which comprises, subsequently to the step of applying the dielectric antireflective layer, applying and structuring a metallizing layer and a solderable securing layer on a back side of the semiconductor wafer.

### Claim 6 (depends on 5)

The method according to claim 5, which comprises:
carrying out the steps of producing the convex structure in the semiconductor wafer, applying a dielectric antireflective layer to the semiconductor wafer having the convex structure, and
applying and structuring a metallizing layer and a solderable securing layer on a back side of the semiconductor wafer for wafers of a wafer package.

### Claim 7 (depends on 6)

The method according to claim 6, which comprises separating the wafers of the wafer package.

### Claim 8 (depends on 6)

The method according to claim 6, which comprises separating the wafers of the wafer package, into wafers each having one convex structure.