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SEMI MF1727-0304 © SEMI 2003, 2004 1 SEMI MF1727-0304 PRACTICE FOR DETECTION OF OX IDATION INDUCED DEFECTS IN POLISHED SILICON WAFERS This practice was technically approved by the Global Silicon Wafer Committee and is th…

SEMI MF1726-1103 © SEMI 2003 3

a b

NOTE: The orientation of the wafer does not define the

locations and direction of the line defects.

Figure 2

Typical Scratches (a) or Mechanically Induced

Defects (b) as Seen With High-Intensity Light

Inspection

8.4.2 Obtain a second sample if evidence of

mechanically or operator induced damage or

contamination is observed, because these artifacts

interfere with the identification of crystal growth

defects.

NOTE 5: Slip defects may be differentiated from the crystal

growth defects by insuring that all of the defects are aligned

as shown in Figure 1. Figure 2 shows the characteristics of

scratches or mechanical damage when viewed under high

intensity light conditions.

8.4.3 Microscopic Defect Counting — Count and report

the density of observed defects using SEMI MF1810.

9 Keywords

9.1 dislocation; epitaxy; grain boundaries; hillock;

polycrystalline imperfections; preferential etch; shallow

pit; silicon; slip; stacking fault

NOTICE: 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 or equipment mentioned

herein. These standards are subject to change without

notice.

By publication of this standard, Semiconductor

Equipment and Materials International (SEMI) takes no

position respecting the validity of any patent rights or

copyrights asserted in connection with any items

mentioned in this standard. Users of this standard are

expressly advised that determination of any such patent

rights or copyrights and the risk of infringement of such

rights are entirely their own responsibility.

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consent of SEMI.

SEMI MF1727-0304 © SEMI 2003, 2004 1

SEMI MF1727-0304

PRACTICE FOR DETECTION OF OXIDATION INDUCED DEFECTS IN

POLISHED SILICON WAFERS

This practice was technically approved by the Global Silicon Wafer Committee and is the direct

responsibility of the North American Silicon Wafer Committee. Current edition approved for publication by

the North American Regional Standards Committee on December 4, 2003. Initially available at

www.semi.org February 2004; to be published March 2004. Originally published by ASTM International as

ASTM F 1727-97. Last previous edition SEMI MF1727-02.

1 Purpose

1.1 Defects induced by thermal processing of silicon

wafers may adversely influence device performance

and yield.

1.2 These defects are influenced directly by

contamination, ambient atmosphere, temperature, time

at temperature, and rate of change of temperature to

which the specimens are subjected. Conditions vary

significantly among device manufacturing technologies.

The thermal cycling procedures of this practice are

intended to simulate basic device processing

technologies. Oxidation cycles other than specified

herein, or multiple oxidation cycles, may sometimes

more accurately simulate device-processing procedures.

The results obtained may differ significantly from those

obtained with the specified oxidation cycles.

1.3 The geometry of some patterns revealed by this

practice suggests that they are related to the crystal

growth process while others seem related to surface

preparation or thermal cycling conditions.

1.4 This practice is suitable for acceptance testing

when used with referenced practices and methods.

2 Scope

2.1 This practice covers the detection of crystalline

defects in the surface region of silicon wafers. The

defects are induced or enhanced by oxidation cycles

encountered in normal device processing. An

atmospheric pressure oxidation cycle representative of

bipolar, metal-oxide-silicon (MOS) and CMOS

technologies is included. This practice reveals strain

fields arising from the presence of precipitates,

oxidation induced stacking faults, and shallow etch pits.

Slip is also revealed that arises when internal or edge

stresses are applied to the wafer.

2.2 Application of this practice is limited to specimens

that have been chemical or chemical/mechanical

polished to remove surface damage from at least one

side of the specimen. This practice may also be applied

to detection of defects in epitaxial layers.

2.3 The surface of the specimen opposite the surface to

be investigated may be damaged deliberately or

otherwise treated for gettering purposes or chemically

etched to remove damage.

NOTICE: This standard does not purport to address

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

responsibility of the user of this standard to establish

appropriate safety and health practices and determine

the applicability of regulatory or other limitations prior

to use.

3 Limitations

3.1 Material having residual work damage in the

polished surface exhibits visible patterns when the

procedures of this practice are used. Usually, edge

damage, lapping damage, tool marks, or scratches are

easily identified by the location and pattern observed.

3.2 Contamination not removed by preparatory

cleaning procedures or deposited following cleaning,

may become visible after oxidation and preferential

etching.

3.3 Slip may be introduced by differential expansion at

the points of wafer support in the furnace boat. Slip

radiating from the points of support may be assumed to

originate from this boat pinch and not be inherent in the

unprocessed wafer. Slip may also be caused by large

thermal gradients imposed across a wafer by fast

insertion or removal from the furnace.

3.4 If the oxidation furnace or apparatus is

contaminated, it can cause extraneous artifacts or

defects.

3.5 Striations, helical features on the surface of a

silicon wafer, are ascribed to periodic dopant

incorporation differences occurring at the rotating solid-

liquid interface during crystal growth. These features

are visible to the unaided eye after preferential etching,

seem continuous under 100× magnification, and may be

confused with ring patterns of oxidation stacking faults.

3.6 Otherwise identical wafers with different back

surface conditions may yield different results by this

practice.

SEMI MF1727-0304 © SEMI 2003, 2004 2

3.7 Wafers, particularly <111> orientation, may show

lower shallow-pit defect density when the back surface

of the wafer is gettered. Backside gettering should be

noted in the sample classification when data are

reported.

4 Referenced Standards

4.1 SEMI Standards

SEMI C3.19 — Standard for Hydrogen (H

) 99.9995%

Quality

SEMI C28 — Specifications and Guidelines for

Hydrofluoric Acid

SEMI C54 — Specifications and Guidelines for

Oxygen

SEMI MF1241 — Terminology of Silicon Technology

SEMI MF1809 — Guide for Selection and Use of

Etching Solutions to Delineate Structural Defects in

Silicon

SEMI MF1810 — Test Method for Counting

Preferentially Etched or Decorated Surface Defects in

Silicon Wafers

4.2 ASTM Standard

D 5127 — Guide for Ultra Pure Water Used in the

Electronics and Semiconductor Industry

NOTICE: Unless otherwise indicated, all documents

cited shall be the latest published versions.

5 Terminology

5.1 Defect-related terminology may be found in SEMI

MF1241.

6 Summary of Practice

6.1 Wet oxidation is used to generate or highlight

defects, or both, in silicon wafers. This oxidation may

also simulate simple device production processes.

6.2 The defects are revealed subsequently by

preferential etching and examination by interference

contrast microscopy according to referenced SEMI

standards.

7 Apparatus

7.1 Oxidation Furnace — furnace shall be consistent

with the intended process application and shall sustain a

designated temperature with uniformity less than ± 5° C

over a zone at least 0.3-m long.

1 Annual Book of ASTM Standards, Vol 11.01. ASTM International,

100 Barr Harbor Drive, West Conshohocken, PA 19428. Telephone:

610-832-9500. Fax: 610-832-9555. Website:

www.astm.org

7.2 Steam Source — Wet oxidation shall be carried out

using a pyrogenic steam generator to provide steam.

7.3 Working Chamber — A pure, fused quartz, silicon

carbide, or silicon tube of an inside diameter sufficient

to hold the specimen wafers. The inlet end shall be

fitted with the appropriate pyrogenic torch apparatus.

The exhaust end shall be fitted to exhaust the process

gases to satisfy applicable environmental requirements

and prevent back streaming of outside air into the

working chamber.

7.4 Wafer Boat — A quartz, silicon or silicon carbide

fixture for holding the specimen wafers either parallel

or perpendicular to the gas flow in the furnace.

7.5 Pickup Tool — A manual or automated transfer

tool fitted with a nonmetallic material such as quartz or

TFE-fluorocarbon. The pickup tool shall be

constructed so that no metal can contact the specimen

wafer.

8 Reagents and Materials

8.1 Purity of Reagents — Chemicals shall conform to

the assay and impurity levels of Grade 1 SEMI

Specifications where they exist. Reagents for which

SEMI specifications have not been developed shall

conform to the specifications of the Committee on

Analytical Reagents of the American Chemical

Society,

where such specifications are available.

Gases shall conform to the purity requirements of the

cited SEMI specifications. Other grades may be used

provided it is first ascertained that the reagent is of

sufficiently high purity to permit its use without

lessening the accuracy of the determination.

8.2 Purity of Water — Reference to water shall be

understood to mean Type E-3 or better water as

described in ASTM Guide D 5127.

8.3 Hydrofluoric Acid — Concentrated, in accordance

with Grade 1 of SEMI C28.

8.4 Hydrogen Gas — In accordance with SEMI C3.19,

for use in pyrogenic steam generator.

8.5 Oxygen Gas — In accordance with SEMI C54, for

use both as furnace ambient and in pyrogenic steam

generator.

2 Reagent Chemicals, American Chemical Society Specifications,

American Chemical Society, Washington, DC. For suggestions on the

testing of reagents not listed by the American Chemical Society, see

Analar Standards for Laboratory Chemicals, BDH Ltd., Poole,

Dorset, U.K., and the United States Pharmacopeia and National

Formulary, U.S. Pharmacopeial Convention, Inc., (USPC), Rockville,

MD.