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Replication Technique

IP.com Disclosure Number: IPCOM000074397D
Original Publication Date: 1971-Apr-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Rideout, VL: AUTHOR

Abstract

A semiconductor "superlattice" structure has been suggested as a test specimen for evaluating resolution in the surface scanning electron microscope. The usefulness of the superlattice structure as a test specimen is limited for several reasons. First, only a small number of test specimens can be fabricated from each superlattice sample. The fabrication process is essentially piecemeal and is continually dependent on the epitaxial crystal growth facility for a supply of new samples. Second, the layer spacing of test specimens obtained from different superlattice samples will differ due to the unavoidable experimental variations that exist between different epitaxial growth runs. Furthermore, the layer spacing of test specimens obtained from a common superlattice sample also differs due to experimental difficulties.

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Replication Technique

A semiconductor "superlattice" structure has been suggested as a test specimen for evaluating resolution in the surface scanning electron microscope. The usefulness of the superlattice structure as a test specimen is limited for several reasons. First, only a small number of test specimens can be fabricated from each superlattice sample. The fabrication process is essentially piecemeal and is continually dependent on the epitaxial crystal growth facility for a supply of new samples. Second, the layer spacing of test specimens obtained from different superlattice samples will differ due to the unavoidable experimental variations that exist between different epitaxial growth runs. Furthermore, the layer spacing of test specimens obtained from a common superlattice sample also differs due to experimental difficulties. Thus each resolution test specimen tends to be unique. These problems can be alleviated by fabricating film replicas from a single semiconductor superlattice test specimen in a manner similar to that by which spectrometer replica gratings are fabricated from a ruled master grating.

Film replicas are prepared as follows: A superlattice specimen is first cleaved to provide a substantially planar surface on which to form the replicas. The superlattice structure itself consists of alternating layers of gallium-arsenide and gallium-arsenide-phosphide which have been formed by epitaxial deposition or vacuum evaporation. The specimen is then etched with a preferential etchant composed of H(2)O, H(2)O(2), and HF (10:1:1) which attacks gallium-arsenide faster than gallium-arsenide-phosphide. Etching enhances the topology of the layered structure so that it becomes similar to a mechanically ruled spectrometer maste...