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SEMI M36-0699 © SE MI 1999 2 Figure 1 Countin g position s for a 50 mm diameter wafer Figure 2 Countin g position s for a 76 mm diameter wafer

SEMI M36-0699 © SEMI 19991

SEMI M36-0699

TEST METHOD FOR MEASURING ETCH PIT DENSITY (EPD) IN LOW

DISLOCATION DENSITY GALLIUM ARSENIDE WAFERS

This test method was technically approved by the Global Compound Semiconductor Committee and is the

direct responsibility of the Japanese Compound Semiconductor Materials Committee. Current edition

approved by the Japanese Regional Standards Committee on March 17, 1999. Initially available at

www.semi.org April 1999; to be published June 1999.

1 Purpose

1.1 This document provides a method to measure etch

pit density (EPD) in low dislocation density GaAs

wafers.

2 Scope

2.1 This test method describes a procedure to measure

EPD of 50 mm and 76 mm diameter round GaAs

wafers with an EPD of less than 5000/cm

2.2 This test method does not include GaAs wafer

preparation, such as wafer slicing, polishing and pit

etching. The preparation of GaAs wafer can be found in

a Referenced Document.

2.3 This standard does not purport to address all of the

safety issues. It is the responsibility of the user of this

standard to establish appropriate safety and health

practices and to determine the applicability of

regulations prior to use of the test method.

3 Referenced Document

3.1 ASTM Standard

F 140-92 — Test Method for Crystallographic

Perfection of Gallium Arsenide by Molten Potassium

Hydroxide (KOH) Etch Technique.

4 Apparatus

4.1 Microscope - Measuring field should be 1 mm

larger.

NOTE: For accurate EPD measurement, accurate area of the

measuring field should be measured by a standard scale.

5 Procedure

5.1 The counting positions for 50 mm diameter wafers

and for 76 mm diameter wafers are shown in Figure 1

and Figure 2 respectively. The counting points are

located in the center of each mesh. In the case of a 50

mm diameter wafer the mesh size is 5 mm. The total

number of counting positions is 69 and position 35 is

located at the center of the wafer. In the case of 76 mm

diameter wafer the mesh size is 10 mm, and the total

number of counting position is 37. Position 19 is

located at the center of the wafer.

5.2 Count and record the number of etch pits for

which the cores are in the measuring field. If the pits

are crowded and are difficult to count, increase the

magnification. After that count the etch pits and record

the results as well as the microscope magnification.

5.3 Repeat Section 5.3 for all other positions, 2

through 69 positions in the case of 50 mm diameter

wafers and 2 through 37 positions in the case of 76 mm

diameter wafers.

6 Calculations

6.1 The EPD in each measuring field is the number of

pits counted divided by the area.

EPD = (Number of pits) / Area

For example, if the size of measuring field is exactly 1

mm × 1 mm, the area is 0.01 cm

7 Report

7.1 There are several forms that are possible for

reporting the EPD, for example the average EPD of all

the positions or the area less than some specified value

or map of EPD for the entire wafer, etc. An appropriate

report form should be decided between the supplier and

the user.

SEMI M36-0699 © SEMI 1999 2

Figure 1

Counting positions for a 50 mm diameter wafer

Figure 2

Counting positions for a 76 mm diameter wafer

NOTICE: These standards do not purport to address

safety issues, if any, associated with their use. It is the

responsibility of the user of these standards to establish

appropriate safety and health practices and determine

the applicability of regulatory limitations prior to use.

SEMI makes no warranties or representations as to the

suitability of the standards set forth herein for any

particular application. The determination of the

suitability of the standard is solely the responsibility of

the user. Users are cautioned to refer to manufacturer's

instructions, product labels, product data sheets, and

other relevant literature respecting any materials

mentioned herein. These standards are subject to

change without notice.

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compliance with this standard may require use of

copyrighted material or of an invention covered by

patent rights. By publication of this standard, SEMI

takes no position respecting the validity of any patent

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item mentioned in this standard. Users of this standard

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of such rights are entirely their own responsibility.

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