Browse Prior Art Database

Etching Mask and Technique Resistant to Concentrated HF

IP.com Disclosure Number: IPCOM000092239D
Original Publication Date: 1968-Oct-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Burkhardt, PJ: AUTHOR

Abstract

This technique protects portions of a semiconductor from prolonged exposure to concentrated HF etching solutions. Multiple beam interference measurements are used in the evaluation of thin films. In the procedure, a step is first etched in the film and subsequently the depth of the step is measured. The step must be straight and sharply defined. For relatively fast etching films, black wax is an adequate mask. However, when longer etch exposures in strong HF solutions are required, such as for etching pyrolytic and sputtered Si(3)N(4) films, black wax deteriorates. This results in jagged steps which cannot be accurately measured.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 87% of the total text.

Page 1 of 1

Etching Mask and Technique Resistant to Concentrated HF

This technique protects portions of a semiconductor from prolonged exposure to concentrated HF etching solutions. Multiple beam interference measurements are used in the evaluation of thin films. In the procedure, a step is first etched in the film and subsequently the depth of the step is measured. The step must be straight and sharply defined. For relatively fast etching films, black wax is an adequate mask. However, when longer etch exposures in strong HF solutions are required, such as for etching pyrolytic and sputtered Si(3)N(4) films, black wax deteriorates. This results in jagged steps which cannot be accurately measured.

A mask of a fluorocarbon grease, such as KEL-F*, withstands concentrated HF for at least one and one-half hours and still yields a straight step. Furthermore, on thick films, a slight taper of the step makes it convenient for determining the number of interference fringes. The grease is easily applied and easily removed with acetone.

In using the fluorocarbon grease, the grease can be first applied to a glass slide or the like in a thin layer. The slide is subsequently pressed against the surface to be masked. The straight edge of the slide deposits a straight edge of grease on the substrate. The glass slide is then slid off leaving a portion of the grease on the slide. The resultant grease film is under some degree of tension. The amount of tension at the step determines the rate a...