semi合集-English.pdf - 第7495页

SEMI MF1723-1104 © SEMI 2004 1 SEMI MF1723-1104 PRACTICE FOR EVALUATION OF POLYCRYSTALLINE SILICON RODS BY FLOAT-ZONE CRYSTA L GROWTH AND SPECTROSCOPY This guide was technically approved b y the Global Silicon Wafer Com …

SEMI MF1708-1104 © SEMI 2004 6

with SEMI MF1630 or by photoluminescence analysis

in accordance with SEMI MF1389, or both.

14 Interpretation of Results

14.1 The results obtained from spectroscopic

techniques on the analytical slice as obtained, directly

represent the impurity concentrations in the granular

polysilicon provided no impurity contamination is

found during the process. In reality, there is always

small impurity contamination during the consolidation

and conversion to a single crystal. This contamination

leads to results higher than actually present in the

granular polysilicon.

15 Precision

15.1 In the mid-nineties, the precision of this practice

was established by one laboratory as follows: A large

sample of granular polysilicon was evaluated repeatedly

and periodically by this practice for over more than a

year. Low temperature Fourier transform infrared

spectroscopy was used to measure the impurity

concentrations. The combined errors of sample

handling, consolidation to polysilicon rod, conversion

to a single crystal ingot, and the infrared determinations

gave a standard deviation of 0.03 ppba at the 0.06 ppba

concentration level for boron and phosphorus and a

standard deviation of 0.03 ppma for interstitial carbon

at the 0.07 ppma level.

15.2 Analysis of more recent similar data indicates that

the standard deviation is less than 0.02 ppba at the 0.04

ppba concentration level for boron and phosphorus and

0.02 ppma for interstitial carbon at the 0.05 ppma level.

16 Keywords

16.1 granular polysilicon; polycrystalline silicon;

polysilicon consolidation; polysilicon evaluation;

polysilicon impurities

NOTICE: SEMI makes no warranties or representa-

tions 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.

International), 3081 Zanker Road, San Jose, CA 95134. Reproduction of

the contents in whole or in part is forbidden without express written

consent of SEMI.

SEMI MF1723-1104 © SEMI 2004 1

SEMI MF1723-1104

PRACTICE FOR EVALUATION OF POLYCRYSTALLINE SILICON

RODS BY FLOAT-ZONE CRYSTAL GROWTH AND SPECTROSCOPY

This guide 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 August 16, 2004. Initially available at www.semi.org

September 2004; to be published November 2004. Original edition published by ASTM International as

ASTM F 1723-96. Last previous edition SEMI MF1723-02.

1 Purpose

1.1 The concentration of acceptor and donor impurities

in polycrystalline silicon (polysilicon) is used by the

grower of monocrystalline silicon ingots to calculate

the additional dopant needed to produce the required

ingot resistivity or to predict the resistivity of undoped

ingots.

1.2 The concentration of acceptor and donor elements

and carbon in the polysilicon is used by the crystal

grower to determine material acceptance.

1.3 The concentration of impurities in the polysilicon

is used for monitoring source gas purity, polysilicon

production processes, development of new processes,

and materials acceptance purposes.

1.4 This practice describes the sampling system and

float-zone crystal growth procedures used to prepare

polysilicon core samples for analysis of acceptor,

donor, and carbon content.

2 Scope

2.1 This practice covers procedures for sampling

polycrystalline silicon rods and growing single crystals

from these samples by the float-zone technique. The

resultant single crystal ingots are analyzed by

spectrophotometric methods to determine the trace

impurities in the polysilicon. These trace impurities are

acceptor (usually boron or aluminum, or both), donor

(usually phosphorus or arsenic, or both), and carbon

impurities.

2.2 The useful range of impurity concentration covered

by this practice is 0.002 to 100 parts per billion atomic

(ppba) for acceptor and donor impurities, and 0.02 to 15

parts per million atomic (ppma) for carbon impurity.

These impurities are analyzed in the ingot samples by

infrared or photoluminescence spectroscopy.

2.3 This practice is applicable only to evaluation of

polysilicon ingots grown by a method that utilizes a

slim silicon rod (filament) upon which the polycrystal-

line silicon is deposited.

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 guides and determine the

applicability of regulatory or other limitations prior to

use.

3 Limitations

3.1 Polysilicon rods that are cracked, highly stressed,

or have deep dendritic growth cannot be sampled due to

shattering or breaking during the coring process.

3.2 Polysilicon cores with fractures, cracked surfaces,

or voids in the surface are difficult to clean. Impurities

are not completely etched out of the cracks or voids, or

etch residues may remain in the cracks, thus contrib-

uting contamination. Cracked or highly stressed cores

may shatter or break during the zoning process. Cores

must be cleaned after fabrication to remove any oil,

grease, or handling contamination.

3.3 The purity of the acids and deionized water (DI) is

critically important. Impurities in the acids, etching

apparatus, or water may interfere with accurate,

reproducible analysis. Etching and zoning should be

done in a clean room to minimize impurities from the

ambient air, walls, floors, and furniture. The specific

acid mixture, acid etch temperature, silicon removal

rate, number of etch-rinse cycles, and exposure time are

other factors that must be monitored and controlled to

prevent impurity interferences. Any materials that

contact the etched cores, such as boats and containers,

must be cleaned before use and monitored to prevent

contamination. Gloves or other materials used to wrap

the etched cores must be tested and monitored to

prevent contamination.

3.4 The zoner itself, especially the preheater, can

introduce impurities into the growing silicon ingot. The

walls, preheater, coil, and seals of the zoner are usual

sources of contamination. Maintaining a clean zoner is

very important to the procedures covered by this

practice.

SEMI MF1723-1104 © SEMI 2004 2

3.5 Any variation from the prescribed float-zoning

procedures that can affect the distribution of the volatile

impurities in the gas, liquid, and solid phases will alter

the results. Variations in core diameter, zone dimen-

sions, pull rate, seal purity, or ambient conditions may

alter the effective distribution coefficient or evaporation

rate and thus change the amount of impurity incorpor-

ated into the crystal.

3.6 Each acceptor or donor element and carbon have

unique segregation coefficients. By growing several

ingots with lengths up to 30 times the zone length, the

effective segregation coefficient can be measured.

These should agree with published values.

Wafers

are cut from this ingot at equilibrium positions

corresponding to the segregation coefficient. Wafers

cut from other locations may not accurately represent

the amount of impurity in the polysilicon. If ingots can

not be grown to sufficient length to achieve the flat

portion of the axial concentration profile, wafers can be

cut from the ingot, and the measured values corrected

for the effective segregation coefficient, based on

repeated measurements of control rods.

3.7 In the conversion of the core to a monocrystal

during zoning, it is possible to lose structure and have a

zoned rod that is not monocrystalline. Ingots with

excessive crystallographic defects give photolumines-

cence or infrared spectra with excessive noise; such

spectra are difficult to interpret accurately. In extreme

cases, it is not possible to obtain acceptable spectra.

4 Referenced Standards

4.1 SEMI Standards

SEMI C3.42 — Specification for Argon

SEMI C28 — Specifications and Guidelines for Hydro-

fluoric Acid

SEMI C35 — Specifications and Guideline for Nitric

Acid

SEMI MF26 — Test Methods for Determining the

Orientation of a Semiconductive Single Crystal

SEMI MF42 — Test Methods for Conductivity Type of

Extrinsic Semiconducting Materials

SEMI MF397 — Test Method for Resistivity of Silicon

Bars Using a Two-Point Probe

SEMI MF723 — Practice for Conversion Between

Resistivity and Dopant Density for Boron-Doped,

Phosphorus-Doped, and Arsenic-Doped Silicon

SEMI MF1241 — Terminology of Silicon Technology

1 Pfann, W., Zone Melting, John Wiley and Sons, New York, 1958.

2 Keller, W., et al., Floating Zone Silicon, Marcel Dekker, Inc., New

York, 1981.

SEMI MF1389 — Test Methods for Photoluminescence

Analysis of Single Crystal Silicon for III-V Impurities

SEMI MF1391 — Test Method for Substitutional

Carbon Content of Silicon by Infrared Absorption

SEMI MF1630 —Test Method for Low Temperature

FT-IR Analysis of Single Crystal Silicon for III-V

Impurities

SEMI MF1725 — Guide for Analysis of Crystallo-

graphic Perfection of Silicon Ingots

4.2 ASTM Standard

D 5127 — Guide for Ultra Pure Water Used in the

Electronics and Semiconductor Industry

4.3 Federal Standard

209-E — Airborne Particulate Cleanliness Classes in

Cleanrooms and Clean Zones

4.4 ISO Standard

ISO 14644–1 — Cleanrooms and associated controlled

environments—Part 1: Classification of airborne

particulates

NOTICE: Unless otherwise indicated, all documents

cited shall be the latest published versions.

5 Terminology

5.1 Definitions

5.1.1 Terms related to semiconductor technology are

defined in SEMI MF1241.

5.1.2 Other Definitions

5.1.2.1 control rod, n — a cylinder of polysilicon taken

from a polysilicon rod with a uniform deposition layer,

having known amounts of boron, phosphorus, and

carbon from repeated analysis.

5.1.2.2 core, n — a cylinder of polysilicon obtained

from a larger piece of polysilicon by drilling with a

hollow diamond drill.

3 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

4 Standardization Documents Order Desk, Bldg. 4 Section D, 700

Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS. (This

standard has been superseded by ISO 14644-1 and may no longer be

available.)

5 International Organization for Standardization, ISO Central

Secretariat, 1, rue de Varembé, Case postale 56, CH-1211 Geneva 20,

Switzerland. Telephone: 41.22.749.01.11; Fax: 41.22.733.34.30

Website:

www.iso.ch

; also available in the US from American

National Standards Institute, New York Office: 11 West 42nd Street,

New York, NY 10036, USA. Telephone: 212.642.4900; Fax:

212.398.0023 Website:

www.ansi.org, and in other countries from

ISO member organizations.