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Browse Prior Art Database

Reference Method for Etch End-Point Detection

IP.com Disclosure Number: IPCOM000043669D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Bayer, T: AUTHOR [+4]

Abstract

It is proposed that a transparent reference sample, which is a thin film or a plate with a homogeneous thickness, be positioned adjacent to a sample of ceramic material to be plasma-etched. During plasma etching, the decreased thickness of the reference sample, which retains a smooth surface, can be measured by means of known interferometric methods. A condition for such measurement is a fixed etch rate ratio, which is independent of variations of the process parameters, between the ceramic and the reference material. Using CF4 as an etchant, an about 10 mm deep recess is plasma-etched into ceramic material containing aluminum. The depth tolerance of the recess is about Å 0.7 mm which roughly equals the cathode non-uniformity of the etch depth, i.e., the permissible run-to-run variation of the depth is several percent.

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Reference Method for Etch End-Point Detection

It is proposed that a transparent reference sample, which is a thin film or a plate with a homogeneous thickness, be positioned adjacent to a sample of ceramic material to be plasma-etched. During plasma etching, the decreased thickness of the reference sample, which retains a smooth surface, can be measured by means of known interferometric methods. A condition for such measurement is a fixed etch rate ratio, which is independent of variations of the process parameters, between the ceramic and the reference material. Using CF4 as an etchant, an about 10 mm deep recess is plasma-etched into ceramic material containing aluminum. The depth tolerance of the recess is about Å 0.7 mm which roughly equals the cathode non-uniformity of the etch depth, i.e., the permissible run-to-run variation of the depth is several percent. Owing to the great run-to-run variations occurring during plasma etching, the etch depth cannot be controlled as a function of the etch time. It is merely possible to monitor the process by in- situ etch depth determination, using etch end-point detection (EEPD). For this purpose, a transparent reference sample is positioned in the reactor adjacent to the aluminum ceramic material to be etched. It has been found that the requirement of the proposed method of having a fixed etch rate ratio between the ceramic and the reference material is met almost ideally by monocrystalline Al2O3 as a sapphire. An exam...