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Cross-Sectional Sample Preparation of Integrated Circuits for TEM Analysis, Using Kerfs of Adjacent Chips

IP.com Disclosure Number: IPCOM000034359D
Original Publication Date: 1989-Feb-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 3 page(s) / 32K

Publishing Venue

IBM

Related People

Hu, CK: AUTHOR [+2]

Abstract

A technique is described whereby cross-sectional transmission electron microscope (TEM) samples of integrated circuits can be produced quickly and reproduced, so as to retain large areas for examination. The concept is an improvement over the previous polishing and ion-beam milling techniques in that the kerfs of adjacent chips are used to reduce both the time required and the high failure rate of samples produced. Typically, cross-sectional TEM analysis of integrated circuits materials, as used in semiconductor-based manufacturing processes, is an integral part of process development and failure analysis. However, there is often a time lag between the end of processing and the return of results of the TEM analysis because of the tedious and exacting preparation required.

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Cross-Sectional Sample Preparation of Integrated Circuits for TEM Analysis, Using Kerfs of Adjacent Chips

A technique is described whereby cross-sectional transmission electron microscope (TEM) samples of integrated circuits can be produced quickly and reproduced, so as to retain large areas for examination. The concept is an improvement over the previous polishing and ion-beam milling techniques in that the kerfs of adjacent chips are used to reduce both the time required and the high failure rate of samples produced. Typically, cross-sectional TEM analysis of integrated circuits materials, as used in semiconductor-based manufacturing processes, is an integral part of process development and failure analysis. However, there is often a time lag between the end of processing and the return of results of the TEM analysis because of the tedious and exacting preparation required. The concept of sample preparation is similar to previous concepts [1], but differs in that extra photolithography processing is not needed. The concept also produces samples which allow in-situ TEM experiments of annealing or corrosion of appropriate samples, whereas the previous methods of preparation did not because of the use of epoxy or adhesive materials. Generally, ready-made cross-sectional TEM samples of blanket films are often available, due to the nature of photolithography and reactive ion etching or lift-off processing. The photolithography processes that rely on steppers often leave a very narrow area between kerfs of adjacent chips. This area is usually 0.1 to 1.0 mm wide and up to 10 mm long, and is defined as the "b-kerf" (between- the-kerf) area. The "b-kerf" area can be protected by either positive photoresist, or some masking material, because it is not exposed to light from the projection system of the photolithographic tool. As a result, the photoresist, or masking material, covering the "b-kerf" is processed as if it were to protect some part of the underlying films that were grown, or deposited, prior to any photolithographic processing.

After the photoresist is developed, or the masking material is patterned, the "b-kerf" is protected from any subsequent etching or processing step. When the next sequence of steps is implemented, so as to subtract the unprotected material, the "b-kerf" is patterned into a thin wall of material of nearly the same dimensions as the developed photo...