semi合集-English.pdf - 第7490页
SEMI MF1708-1104 © SEMI 2004 2 SEMI MF1630 — Test Method for Low Temperature FT-IR Analysis of Single Crystal Silico n for III-V Impurities 4.2 ASTM St andard D 5127 — Guide for Ultra Pure Water Used in the Electronics a…
SEMI MF1708-1104 © SEMI 2004 1
SEMI MF1708-1104
PRACTICE FOR EVALUATION OF GRANULAR POLYSILICON BY
MELTER-ZONER SPECTROSCOPIES
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 1708-96. Last previous edition SEMI MF1708-02
1 Purpose
1.1 Polycrystalline silicon is used as the starting
material for growth of large single crystal ingots by
Czochralski methods.
1.2 Although Czochralski grown ingots are intention-
ally doped during crystal growth to the desired
resistivity and type, the dopant levels in the polysilicon
must be known to calculate the amount of dopant to be
added. This practice provides a means to determine the
impurity levels in granular polysilicon to be used for
crystal growth.
1.3 Carbon levels in polysilicon must be known so that
the concentration of carbon in the ingot can be
controlled to a low level.
1.4 This practice has applicability in production control,
quality assurance, materials research, and materials
acceptance.
2 Scope
2.1 This practice describes a procedure to consolidate
granular polysilicon into a solid rod and then to convert
the polysilicon rod into a single crystal by a float-zone
technique. The resultant single crystal ingot is used for
the determination of trace impurities in the polysilicon.
These impurities are acceptor and donor components
(usually boron, aluminum, phosphorus, arsenic, and
antimony) as well as substitutional carbon.
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. The
acceptor and donor impurities in a slice taken from the
single crystal ingot are analyzed by photoluminescence
or infrared spectroscopies. The carbon impurity is
determined by analysis of a slice by infrared
spectroscopy.
2.3 This practice is applicable only to evaluation of
polysilicon granules as produced by thermal
decomposition and deposition of silane, or one of the
chlorosilanes, onto high purity seeds of polysilicon in a
continuous or batch fluid bed reactor. The granules are
near spherical in shape and range in size from 200 to
3000 m with a mean size of about 900–1200 m.
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 The quartz tubes used in this procedure must be of
high purity, especially in regards to the impurities to be
measured. Boron is of particular concern since it is
always present in quartz and may frequently appear in
uncharacteristically high concentrations in polysilicon.
3.2 All chemicals and gases used in this procedure must
be free of components to be measured or they may give
extraneously high results.
3.3 Loss of single crystal during the zone pass will
produce an ingot that may give unsatisfactory results.
The quality of the infrared or photoluminescence
spectra usually reveals the lack of single crystal.
4 Referenced Standards
4.1 SEMI Standards
SEMI C3.42 — Specification for Argon
SEMI C28 — Specifications and Guidelines for
Hydrofluoric Acid
SEMI C31 — Specification for Methanol
SEMI C34 — Specification and Guideline for Mixed
Acid Etchants
SEMI C35 — Specifications and Guideline for Nitric
Acid
SEMI MF1241 — Terminology of Silicon Technology
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 MF1708-1104 © SEMI 2004 2
SEMI MF1630 — Test Method for Low Temperature
FT-IR Analysis of Single Crystal Silicon for III-V
Impurities
4.2 ASTM Standard
D 5127 — Guide for Ultra Pure Water Used in the
Electronics and Semiconductor Industry
1
4.3 Federal Standard
209-E — Airborne Particulate Cleanliness Classes in
Cleanrooms and Clean Zones
2
4.4 ISO Standard
ISO 14644–1 — Cleanrooms and associated controlled
environments—Part 1: Classification of airborne
particulates
3
NOTICE: Unless otherwise indicated, all documents
cited shall be the latest published versions.
5 Terminology
5.1 Acronym
5.1.1 PTFE — polytetrafluoroethylene, a chemically
resistant polymer.
5.2 Definitions
5.2.1 Most terms used in this practice are defined in
SEMI MF1241.
5.2.2 Other Definitions
5.2.2.1 granular polysilicon, n — nearly spherical,
granules (200 to 3000 m) of polysilicon as produced
in a fluidized bed reactor.
5.2.2.2 melter/zoner, n — an apparatus designed to
melt granular polysilicon to a solid rod and then convert
the polycrystalline rod to a single crystal ingot by an rf
coupled coil.
5.2.2.3 silicon pedestal, n — a piece of single crystal
silicon cut from a high purity silicon ingot.
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
2 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.)
3 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.
6 Summary of Practice
6.1 Granular polysilicon is converted into a single
crystal silicon rod in a two-step procedure.
6.1.1 First, the silicon granules are consolidated into a
polysilicon rod by melting fluidized granules into the
molten (bottom) end of a silicon pedestal during a
downward pass of the coil of the zone furnace. After
about 15 g of polysilicon has been melted and cooled in
the zone process, a polysilicon rod about 8 to 12 mm in
diameter and up to 70 mm in length is obtained.
6.1.2 In the second step, a single crystal silicon seed is
melted into the tail end of the polycrystalline rod and a
single zone pass is done in the upward direction to level
the impurities and to convert the silicon to a single
crystal rod. This produces a single crystal silicon ingot
about 8 to 12 mm in diameter and up to 70 mm in
length from which a section is sliced for measurement
of impurities. The entire consolidation and zoning
requires about 30 min to accomplish.
6.1.3 A slice 2 to 4 mm thick is taken from the center
one-third of the single crystal silicon ingot for
measurement of impurities by infrared or
photoluminescence spectroscopies.
7 Apparatus
7.1 Acid Exhaust Fume Hood — To provide for exhaust
of acid fumes, a clean air environment (ISO Class 6
minimum, as defined in ISO 14544-1), a drain for acids
and water, and a deionized water supply. This hood
provides for the cleaning of quartz containers, funnels,
and tubes used in the melter/zoner as well as a place to
etch silicon pieces and samples used in this practice.
NOTE 1: ISO class 6 is about the same as Class 1000 as
defined in Federal Standard 209E).
7.2 Laminar Flow Hood — To provide a flow of clean
(ISO Class 6 minimum) air for drying of components
and the etched and clean silicon pieces.
7.3 Quartz Sample Containers — 200 to 300 mL
capacity quartz bottles to contain and transport granular
polysilicon samples.
7.4 Quartz Funnel — A funnel of sufficient size to
transfer granular polysilicon from the sample container
to the 15 mm inside diameter quartz tube.
7.5 Quartz Tube — A section of high purity quartz tube
with 18 mm outside diameter, 15 mm inside diameter,
and a length of 556 mm. The inside diameter and
outside diameter variances should be small to avoid
problems with clearances both internally and externally.
This tube provides the working enclosure for both the
consolidation and the zone leveling within the confines
of the working coil of the melter/float zone apparatus.
SEMI MF1708-1104 © SEMI 2004 3
7.6 Melter/Float Zone Apparatus — A radio frequency
(rf) generator operating between 2.0 and 3.0 MHz with
a copper, water-cooled working coil for rf coupling to
the silicon (see Figure 1). The coil shall have an inside
diameter of 20 mm to accommodate the 18 mm outside
diameter quartz tube and shall have sufficient power to
sustain a molten zone of at least 2 cm. Controls to
adjust the power output of the rf generator must be
readily available to the operator. The apparatus shall
have a carriage to vertically support and move the
quartz tube through the coil in a smooth and continuous
manner. The upper and lower endpieces of the carriage
shall be designed with chucks to hold silicon pedestals
as well as the quartz tubing. These endpieces shall
provide a seal to exclude air from the inside of the tube
and have connections for argon entry at the bottom
endpiece and exhaust at the top. Manual as well as
motorized movement of the carriage in the vertical
direction while minimizing horizontal motion is
essential. This entire apparatus is set up and utilized
inside a Class 6 clean room.
Figure 1
Melter/Float Zone Apparatus
7.7 PTFE Plunger-Diffuser — A cylindrical piece of
PTFE machined to close tolerance that fits snugly but
can be moved freely inside the quartz tube. This PTFE
plunger is drilled with an array of small holes for
diffusion of argon gas from the bottom endpiece of the
zoner carriage, through a bed of polysilicon granules,
and finally exhausted through the top endpiece. The
bottom of this plunger is machined to fit on the end of a
stainless steel rod that is extended through and
supported by the bottom endpiece. This rod provides a
way to vertically move the PTFE plunger/diffuser plate
within the quartz tube.
7.8 Chucks — Designed to hold silicon pedestals and
seed rods.
7.8.1 Upper Chuck — A three-jaw chuck designed to
hold a 6-mm silicon pedestal rod inside the quartz tube
and supported vertically from the top carriage piece.
7.8.2 Lower Chuck — A cylindrical piece of stainless
steel that fits inside the quartz and upon the upper end
of the stainless steel rod extending from the lower
endpiece with a hole drilled in the top about 3 mm
inside diameter and 1 cm deep (see Figure 1). This
supports a 2.5 mm single crystal silicon seed rod in a
near vertical position while allowing some (about 2
mm) horizontal movement at the top of an 80 mm rod.
7.9 Hydrogen Torch — Constructed by restricting the
end of a
¼ in. outside diameter piece of stainless steel
tubing and drilling a 1.5 mm hole as the orifice. This
torch is used to preheat the silicon to the point where rf
coupling occurs.
7.10 Diamond Saw — Suitable for cutting a sample 2 to
4 mm thick from the single crystal ingot.
7.11 Clean Room Garb — Including gowns, gloves, lint
free paper, etc.
7.12 Polyethylene Forceps — Size to hold 6 to 12-mm
silicon slice.
7.13 PTFE Beakers — 100 mL in size for handling
acids used in etching or cleaning.
8 Reagents and Materials
8.1 Hydrogen Gas — Low purity gas cylinder for
hydrogen torch.
8.2 Argon Gas — In accordance with SEMI C3.42.
8.3 Hydrofluoric (HF) Acid (49 %), in accordance with
Grade 1 of SEMI C28.
8.4 Nitric (HNO
3
) Acid (70 %) — In accordance with
Grade 1 of SEMI C35.
8.5 Mixed Acid Etchant (MAE) 57:18:25 — Composed
of HF:HNO
3
:Acetic Acid, in accordance with Grade 1
of SEMI C34.
8.6 Methanol — In accordance with Grade 1 of SEMI
C31.