Microdefects in wafers sliced from selected positions along Czochralski (CZ)-grown, silicon single crystal ingots were investigated by means of transmission electron microscopy (TEM). Specimens taken from the central regions of these wafers, previously subjected to specific thermal treatments, were prepared either by ultrasonic cutting and jet thinning or by an anisotropic thinning method. Ultrasonic cutting was found to generate microdefects in the thin surface regions of the TEM specimen discs. The density of ultrasonically generated defects (USD's) was found to vary directly with the ultrasonic energy input from the cutter. Ultrasonic waves transmitted through abrasive slurry into the discs, causing lattice vibrations, are believed to be responsible for the microdefect generation. Anisotropic thinning for the preparation of TEM specimens was carried out in an agitated bath of KOH-Isopropyl Alcohol (IPA)-H₂O at 80°C and 60°C. A great number of high-surface-quality, self-supporting thin films can be produced with large (about 30 mils square) electron-transparent areas. Edges of the thin films are in <110> directions and can be used as quick reference for defect orientation during electron microscopy. Specimens from heat-treated wafers disclosed the presence of precipitates measuring some 100-1500 nm on one side, surrounded by prismatic dislocations punched out in <110> directions in the crystal. The precipitates appear to be thin platelets (less than 40 Å in thickness), lying on {100} planes and are viewed either as flat squares or rectangles, or as edge-on rods inclined 45° to the <110> directions. The edges of the platelets are in <110> directions. Prismatic punched-out dislocation loops are formed in rows, the axes of which are in <110> directions. A row of loops seen edge-on is similar in size if its axis is in the surface <110> directions. When loop axes are in the oblique <110> directions from the surface, they appear as closed rhombus loops with line senses in <112> directions. Their size increases with distance from the precipitate. The observed dislocation loops were found to be of interstitial type with a Burger's vector of a/2 <110>. The total defect density (precipitates and dislocation loops) of a specimen depend strongly on the thermal history of the wafer and on the wafer position in the ingot.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/184803 |
| Date | January 1982 |
| Creators | CHANG, LI-HSIN. |
| Contributors | Demer, Louis J. |
| Publisher | The University of Arizona. |
| Source Sets | University of Arizona |
| Language | English |
| Detected Language | English |
| Type | text, Dissertation-Reproduction (electronic) |
| Rights | Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. |
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