Browse Prior Art Database

Crystal Revelation

IP.com Disclosure Number: IPCOM000052533D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Cazcarra, V: AUTHOR

Abstract

Silicon ingots nearly always have dislocations at the tail end. The length impacted depends on the ingot diameter and on how the tail end of the crystal is made. This problem, if not properly solved, may impact semiconductor yields.

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Crystal Revelation

Silicon ingots nearly always have dislocations at the tail end. The length impacted depends on the ingot diameter and on how the tail end of the crystal is made. This problem, if not properly solved, may impact semiconductor yields.

Different solutions have been used thus far in order to process only the good parts of the crystals.

A thick wafer is sliced at the tail end of the crystal and revealed after chemical tinning. If defects are observed, the process is started again and continued until a good wafer is obtained.

This procedure (although very long) works well when the crystals are pulled according to the <111> direction, since the dislocation figures are triangles. For the crystals pulled according to the <100> direction, revelation is more difficult since the etch figures (theoretically square-shaped) are very difficult to differentiate from etch pits (round-shaped) due to impurities.

To solve this problem, a method will be described which reveals all the tail ends of the crystal.

The chemical revelation comprises the following steps: a - Introduce the tail end of the silicon ingot in a plastic beaker of 2 liters. Add 1 liter of White Etch (composition: 4 volumes of HNO(3), 1 volume of HF), and etch for 10 minutes in order to get a very bright appearance of the crystal tail end. b - Rinse with D.I. water and empty the beaker. c - Put 1 liter of Sirte Etch (composition: 1 volume of HF for 1 volume of H(2)C(2)O(4) solution), wait for 10 m...