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ADVANCES IN TEM SPECIMEN PREPARATION

IP.com Disclosure Number: IPCOM000006526D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2002-Jan-11
Document File: 5 page(s) / 257K

Publishing Venue

Motorola

Related People

N. David Theodore: AUTHOR [+2]

Abstract

Transmission electron microscopy [TEM] is an ana- lytical technique that involves propagation of electron beams through a thin foil of material. The transmitted beams contain information that make possible the anal- ysis and study of(i) microstructure of device-structures, semiconductor, metal, or insulating layers, (ii) continu- ity of layers, including the. presence of pin-holes or islanding, (iii) quality of interfaces, (iv) material interac- tions such as phase-reactions, corrosion, action of dihit- sion barriers and glue layers in device-structures, (v) defects such as dislocations, grain-boundaries, twins, pre- cipitates, stacking faults in materials. For TEM analysis, thin-foil specimens (h lo-500 nm thick) have to be pre- pared in plan-view (for plan-view TEM), or in cross- section (for cross-section TEM), from the materials of interest; the resulting foils have to be electron transpar- ent. This paper presents advances in TEM specimen preparation in three areas (i) preparation ofmultiple plan- view TEM specimens, (ii) preparation of multiple cross- section TEM [XTEM] specimens, and (iii) preparation of specific-feature XTEM specimens.

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MOTOROLA INC. Technical Developments Volume 16 August 1992

ADVANCES IN TEM SPECIMEN PREPARATION

by N. David Theodore and Ray Doyle

  Transmission electron microscopy [TEM] is an ana- lytical technique that involves propagation of electron beams through a thin foil of material. The transmitted beams contain information that make possible the anal- ysis and study of(i) microstructure of device-structures, semiconductor, metal, or insulating layers, (ii) continu- ity of layers, including the. presence of pin-holes or islanding, (iii) quality of interfaces, (iv) material interac- tions such as phase-reactions, corrosion, action of dihit- sion barriers and glue layers in device-structures, (v) defects such as dislocations, grain-boundaries, twins, pre- cipitates, stacking faults in materials. For TEM analysis, thin-foil specimens (h lo-500 nm thick) have to be pre- pared in plan-view (for plan-view TEM), or in cross- section (for cross-section TEM), from the materials of interest; the resulting foils have to be electron transpar- ent. This paper presents advances in TEM specimen preparation in three areas (i) preparation ofmultiple plan- view TEM specimens, (ii) preparation of multiple cross- section TEM [XTEM] specimens, and (iii) preparation of specific-feature XTEM specimens.

PART I: SIMULTANEOUS MULTIPLE

PLAN-VIEW TEM SPECIMENS

  The task of specimen preparation for plan-view TEM is often diBicult, tedious and labor-intensive. Conven- tional techniques involve a tedious process of specimen preparation that needs to be repeated for each wafer that needs to be analyzed. Part I of this paper presents a novel technique for simultaneous preparation of multi- ple plan-view TEM specimens. The technique reduces repetition of sample preparation (for multiple wafers) thus reducing specimen preparation time, tedium and labor required; this then produces increased through- put and productivity.

The conventional technique for preparation of plan- view TEM specimens is as follows. We are given four Si

wafers with varied deposited and annealed layers for F'fEM analysis. The procedure described below is for one F'fEM sample. We repeat the procedure four times to produce samples from the four wafers. First, ultrasonically drill a 3mm disc from the wafer, with the layer-of-interest [LOI) on top. Dimple the disc from the bottom to obtain a IlnaI thickness [in the center) of - 10pm. Ion mill the disc from the bottom till a perforation is obtained. The perforted disc is shown in perspective- view in Figure 1. Material near the perforation in the disc will be electron-transparent, and ready for TEM analysis. Repeat the above procedure four times to pre- pare samples from the four wafers.

  The new technique for preparation of plan-view TEM specimens is as follows. Once again we are given four wafers [A,B,C,Dl with different top layers. This time we intend to make a simultaneous quadruple PTEM spec- imen. First, cut strips of Si [ - lmm x 2 mm] from each wafer...