semi合集-English.pdf - 第5409页
SEMI M58-0704 © SEMI 2004 2 4 Referenced Standards 4.1 SEMI St andards SEMI M50 — Test Me thod for Determ ining Capture Rate for Surface Sca nning Inspection System s by the Overlay Method SEMI M52 — Guide for Specifying…
SEMI M58-0704 © SEMI 2004 1
SEMI M58-0704
TEST METHOD FOR EVALUATING DMA BASED PARTICLE
DEPOSITION SYSTEMS AND PROCESSES
This test method was technically approved by the Global Silicon Wafer Committee and is the direct
responsibility of the North American Silicon Wafer Committee. Current edition approved by the North
American Regional Standards Committee on April 22, 2004. Initially available at www.semi.org May 2004;
to be published July 2004.
1 Purpose
1.1 SEMI M52 requires the use of certified reference
materials (CRMs) for calibration of scanning surface
inspection systems (SSISs). The calibration method is
defined in SEMI M53. This test method provides the
procedure to determine whether a specific particle
deposition system, using a differential mobility
analyzer (DMA), can produce the required CRMs.
1.2 Both organizations producing depositions internally
for in-house use and companies manufacturing
depositions for sale can apply this test method to ensure
that their particle deposition systems provide
depositions that meet the requirements of SEMI M52.
2 Scope
2.1 This test method covers determination of the
deposition peak diameter and the associated expanded
relative combined peak diameter uncertainty produced
by a particle deposition system and its associated
deposition procedures for comparison to the 3%
requirement of SEMI M52.
2.2 This test method also covers determination of the
ability of the deposition system to produce depositions
with diameter distributions that are less than 5% full
width at half maximum (FWHM) as required by SEMI
M52 even when using a particle source with a much
wider distribution.
2.3 These tests require that the deposition system
employ a DMA (or an equivalent programmable
filtering system) to accomplish both peak diameter
determination and narrowing of particle source
distributions (see Related Information 1).
2.4 This test method covers determination of
repeatability over a period of one week. Tests can be
repeated periodically to determine long term stability.
Long term stability of most DMA-based particle
deposition systems is believed to be on the order of a
year or more, but it is recommended that the tests be
repeated on an annual basis or whenever the instrument
appears to be out of control.
2.5 This test method requires the use of three different
kinds of particle distributions with specified
characteristics and wafers that have surface
characteristics adequate to allow detection of the
smallest particles utilized with a capture rate of greater
than 95%.
NOTICE: This standard does not purport to address
safety issues, if any, associated with its use. It is the
responsibility of the users 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 This test method is limited to use of depositions of
PSL spheres, even though the deposition system under
test may be capable of depositing particles of other
materials.
3.2 When used to make a deposition from a suspension
of PSL spheres that does not have an observable
certified peak diameter (or if the deposition is made at a
size away from the peak of the distribution in the
suspension), the uncertainty with which the deposition
system evaluates a peak deposition diameter includes
bias information determined from measurements on a
known standard or standards with extremely narrow
distributions. At the time when this test method was
developed, only one such standard existed. Therefore if
the bias contribution to uncertainty is a function of the
peak diameter in the suspension, the determination may
be in error at peak diameters away from that of the
known standard.
3.3 There is the possibility that the deposited particle
diameter may differ slightly from the certified value for
the bottle containing the suspension because the
surfactant in the suspension and contaminants in the
water may cause an increase in particle size. This
limitation can be avoided by using DMAs with the
same spray system, the same purity of dilution water,
and the same suspension concentration both to size the
particles in the bottle and make the deposition. This
possibility may be minimized by using PSL suspension
fluids with low non-volatile content to reduce the
possibility of non-volatile materials drying onto the
particles in the suspension.
SEMI M58-0704 © SEMI 2004 2
4 Referenced Standards
4.1 SEMI Standards
SEMI M50 — Test Method for Determining Capture
Rate for Surface Scanning Inspection Systems by the
Overlay Method
SEMI M52 — Guide for Specifying Scanning Surface
Inspection Systems for Silicon Wafers for the 130-nm
Technology Generation
SEMI M53 — Practice for Calibrating Scanning
Surface Inspection Systems using Depositions of Mon-
odisperse Polystyrene Latex Sphere on Unpatterned
Semiconductor Wafer Surfaces
SEMI MF1241 — Terminology of Silicon Technology
4.2 ISO Standard
1
ISO 14644-1 Cleanrooms and associated controlled
environments — Part 1: Classification of airborne
particulates
NOTICE: As listed or revised, all documents cited
shall be the latest publications of adopted standards.
5 Terminology
5.1 Definitions for terms related to surface scanning in-
spection systems are found in SEMI M50, SEMI M52,
and SEMI M53.
5.2 Additional terminology related to silicon wafer
technology is defined in SEMI MF1241.
6 Summary of Method
6.1 Three bottles (A, B and C) of PSL sphere
suspensions meeting specific requirements are obtained.
Bottle A is a CRM with a certified peak diameter and a
very narrow diameter distribution so that no matter how
the deposition system functions, the deposition will
meet the requirements of SEMI M52. Bottles B
(smaller diameters) and C (larger diameters) have much
wider distributions and there are no restrictions on peak
diameter accuracy.
6.2 Over a five day period, spot depositions of the same
number of each of the three PSL sphere sizes are made
each morning on one or more wafers and a final scan
check of the diameter of spheres in Bottle A is made
late in the day.
1 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.
6.3 The deposited diameters from each bottle, as
determined by the deposition system, are recorded on a
data sheet.
6.4 At the end of the week the spot depositions are
scanned with an SSIS to obtain a histogram for each
spot deposition. The FWHM values are obtained from
these histograms and recorded. The peak diameter
values and particle counts found from the SSIS may
also be recorded, but these values are not required to
verify the requirements of SEMI M52.
6.5 The results for each bottle are analyzed to determine
if the deposition system has a peak diameter expanded
relative combined standard uncertainty less than 3%
and a deposited FWHM on the wafer of less than 5%,
as required by SEMI M52.
7 Apparatus
7.1 Particle Deposition System
7.1.1 The particle deposition system to be evaluated
must be available in a clean room of class 4 or better as
defined in ISO 14644-1.
7.1.2 The deposition system must have an atomizer
that takes the particles from the liquid suspension to an
air droplet mist.
7.1.3 The particle deposition system must have a DMA
(or an equivalent programmable filtering system) to
accomplish both peak diameter determination and
narrowing of particle source distributions.
7.1.4 The deposition system must have wafer handling
equipment appropriate for the wafers on which the
depositions are being made.
7.2 Surface Scanning Inspection System
7.2.1 An SSIS appropriate for use with the wafers used
and the PSL spheres deposited must be capable of
determining the FWHM of each of the depositions
made.
7.2.2 The SSIS does not have to be calibrated in
accordance with SEMI M53 in order to be used in this
test method, but the results obtained when the test
method is performed can give an indication of the
calibration of the SSIS in the size region of the test.
8 Reagents and Materials
8.1 PSL Spheres
8.1.1 Three types of PSL liquid sphere suspensions are
used in this test method.
8.1.1.1 Bottle A is a CRM that contains a suspension of
PSL spheres with a relative expanded peak diameter
uncertainty much less than 3% and a FWHM less than
SEMI M58-0704 © SEMI 2004 3
5%. It is used in the measurement of (1) peak diameter
repeatability and (2) peak diameter bias of the
deposition system.
2
8.1.1.2 Bottle B contains a suspension of PSL spheres
with a single well defined peak diameter that is at least
20% smaller than that of the spheres in Bottle A, and a
FWHM that is significantly larger than 5%. It is used
in the measurement of (1) peak diameter repeatability
and (2) FWHM of the deposition system when filtering
a smaller diameter with a broad diameter distribution.
8.1.1.3 Bottle C contains a suspension of PSL spheres
with a single well defined peak diameter that is at least
30% larger than Bottle A, and a FWHM that, if
possible, is larger than 5%. It is used in the
measurement of (1) peak diameter repeatability and (2)
FWHM of the deposition system when filtering a larger
diameter with a broad diameter distribution.
NOTE 1: Because spheres with peak diameters larger than
100 nm often have a FWHM smaller than 5% it may not be
possible to secure a bottle with FWHM greater than 5%; in
this case use a bottle with as large a FWHM as possible.
8.2 Wafers
8.2.1 One or more polished silicon wafers of
appropriate diameter that have a high enough surface
quality that the smallest PSL spheres deposited can be
detected on the SSIS with a capture rate greater than
95% as determined in accordance with SEMI M53.
9 Preparation and Control of Apparatus
9.1 The deposition system under test must be available
to run without scheduled, or unscheduled, maintenance
or other interruption for the full five day test period.
9.2 Maintain a control chart of the voltage(s) associated
with one or more peak diameters on a daily or weekly
basis to ensure that the deposition system is under
control.
9.3 Repeat the entire test procedure, calculations, and
interpretation of results (see Sections 10 through 12) on
an annual basis or whenever the control chart shows out
of control conditions.
10 Procedure
10.1 Obtain three bottles of suspensions of PSL spheres
(A, B and C) as described in Section 8.1. Record the
peak diameter certified 1σ relative uncertainty, and
%FWHM of the particle distribution in Bottle A on the
data sheet. Record the supplier, part number, and lot
number for each bottle of suspensions. If available,
record the same information for Bottles B and C. An
2 At the present time, NIST SRM 1963 meets these requirements.
example data sheet is shown in Figure 1 and a
completed example is shown in Figure R2-1.
NOTE 2: If desired, the data sheet can be set up as a spread-
sheet that automatically completes the calculations discussed
in Section 11. This spreadsheet is outlined in Related
Information 2. If this is done, error messages will appear in
the cells that contain the equations to perform the calculations
until the data has been entered.
10.2 Record on the data sheet the laboratory name, the
contact for the test, the address, telephone number, and
e-mail address by which the contact can be reached, and
the dates of the test.
10.3 Record on the data sheet the identification of the
deposition system under test, including supplier and
model number, serial number, and software revision. If
the test has been performed previously on this
deposition system, enter the date of the last previous
test.
10.4 Choose one or more wafers upon which to make
the depositions and load the first wafer into the
deposition system.
10.5 Choose a value of N (between 1000 and 3000)
particles for the deposition count and record this value
on the data sheet. Use the same value of N for all
depositions.
10.6 Depositions on the First Day
10.6.1 On the morning of the first day of a five day
period, scan the particles from Bottle A in the
deposition system to find the peak diameter. Record
the peak diameter as found by the deposition system in
the Day 1 row of the first Bottle A column of the
Deposition System Diameter portion of the data sheet.
Then use the deposition system, centered at the peak
diameter, to make a deposition of N particles at a
location on the first wafer.
10.6.2 Repeat this procedure for bottles B and C,
recording the peak diameter as found by the deposition
system in the appropriate Day 1 columns of the
Deposition System Diameter portion of the data sheet.
10.6.3 Near the end of the day, make a final peak
diameter scan (but not an additional deposition) of
bottle A. Record the peak diameter as found by the
deposition system in the Day 1 row of the second Bottle
A column of the Deposition System Diameter portion
of the data sheet.
10.7 Repeat the procedures of subsection 10.6 for the
next four days, using additional locations on the wafer
or on additional wafers.
10.8 At the end of the five days run the wafer (or
wafers) on an SSIS, to obtain a histogram for each of
the 15 depositions.