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TRANSMISSION ELECTRON MICROSCOPY OF SURFACE FEATURES

IP.com Disclosure Number: IPCOM000006576D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2002-Jan-16
Document File: 2 page(s) / 222K

Publishing Venue

Motorola

Related People

N. David Theodore: AUTHOR

Abstract

Transmission electron microscopy (TEM) is a tech- nique used for analyzing the microstructures of semi- conductors, device-structures, metals, and insulating layers. An electron beam is incident upon a thin foil of specimen-material. Electron beams transmitted or diffracted through the thin-foil provide high-resolution information about the material and its microstructure. The technique requires plan-view TEM specimens that consist of thin electron-transparent foils -10-500 nm thick.

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MOTOROLA INC. Technical Developments Volume 16 August 1992

TRANSMISSION ELECTRON MICROSCOPY OF SURFACE FEATURES

by N. David Theodore

  Transmission electron microscopy (TEM) is a tech- nique used for analyzing the microstructures of semi- conductors, device-structures, metals, and insulating layers. An electron beam is incident upon a thin foil of specimen-material. Electron beams transmitted or diffracted through the thin-foil provide high-resolution information about the material and its microstructure. The technique requires plan-view TEM specimens that consist of thin electron-transparent foils -10-500 nm thick.

  Conventional plan-view TEM (PTEM) techniques provide information about the microstructure of speci- mens, but do not provide information about surface fea- tures. This paper presents a novel technique for TEM analysis of surface features on thin fdms. The technique makes possible correlation between microstructure and surface features on thin tilms. Such correlation is strongly relevant for reflective-notching and electromigration studies.

  The conventional technique for PTEM microstruc- ture analysis is as follows. First, prepare a plan-view TEM sample from the thin-film that is to be analyzed. Next, obtain bright-field micrographs by using an aperture to preferentially select the transmitted electron-beam. Dark-field micrographs can be obtained using an aperture to select particular diffracted electron-beams. Such micrographs provide microstructural information but no surface-feature information. An example of a bright-field micrograph (obtained from AI-l.S%Cu) is presented in Figure 1. Information relating to grain-sizes can be obtained from the micrograph, but surface- information is absent.

  The new technique is useful for imaging surface- features on metal or semiconductor thin-tihns using TEM. Correlations can then be made between surface-features and microstructure of the films. Grain-boundary detini- tion is also improved over conventional techniques. The new technique for analysis of surface-features by TEM is as follows. Prepare a plan-view TEM sample from the thin-film that is to be analyzed. In the TEM, move the

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sample to eucentric position. Now focus the imaging lens-system of the TEM on the selected-area aperture. This ftxes the focal plane of the imaging system. Vary the objective-lens current while observing the contrast present in a bright-field image. When c...