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SEMI M35-1104 © SEMI 1999, 1104 3 6 Terminology 6.1 Most terminology used in this guide is defi ned in SEMI M1 and/or SEMI MF1241. 6.2 Othe r terms are defined as f ollows: 6.2.1 extended light scatterer (XLS)  a featur…

SEMI M35-1104 © SEMI 1999, 2004 2

manufactured to a known size, or has been measured

via AFM.

3.2.2 Haze is specified as parts per million (ppm) of

measured scattered optical power relative to the

incident optical power on the surface. All of the

associated measurement conditions must be given (or

implied) with the specified haze value. These

conditions include: source incident angle (measured as

a polar angle from surface normal), source polarization

(S, P, other), source wavelength (or wavelength band),

nominal source spot size at the wafer, haze collection

angles (given as solid angles with directions). All of

these quantities must be part of a haze specification,

either by description, or by implication to specific

instrumentation (with known or fixed parameters).

3.2.3 Haze is quantified by measuring scattered light

power over one or more solid angles and then

normalizing by the light power incident on the surface.

It is nothing more than the diffuse reflectance of a

surface in specified directions for a known source

(incident angle, polarization, spot size, wavelength

band) and receiver (or detector) configuration (solid

angles and locations). Measured haze can be expected

to change if the surface is changed, or if any of the

measurement parameters change.

3.2.4 Under special conditions, where the source of the

haze is known, it may be possible to use a model to

predict the haze reading on one instrument from the

haze reading on another. For example, if on the basis of

product experience and measurements on a few wafers,

the surface power spectral density function can be

determined, then the haze due to surface roughness can

be calculated for an instrument with different

parameters. Haze caused by a large number of small

particles and/or film contamination is more difficult to

model.

3.2.5 An SSIS often reports haze as the arithmetic

average of a grid of local haze measurements taken over

the FQA. This average can be, and often is, biased by

wafer haze distributions that exhibit long, positively

skewed tails. SSIS software is being developed that

automatically calculates other haze statistics, such as

the median haze value, the standard deviation of the

haze distribution, and so on.

3.3 The SSIS used for automated inspection of silicon

wafer surfaces should be calibrated in terms of latex

sphere equivalents in accordance with SEMI M53 or

another method agreed upon between supplier and

customer.

4 Limitations

4.1 The following measurement considerations impose

limitations on the guidelines.

4.1.1 Histograms calculated in latex sphere equivalents

may be distorted, because a given surface has in general

LLSs of different size, shape, and material.

4.1.2 Measurement results do not always compare well

between systems, because different SSIS designs

employ different geometries and gather light scattered

in different directions. Haze maps may have different

levels and localized surface features may have different

calculated sizes.

4.1.3 All scanning systems have a minimum LSE size

of LLSs that can be reliably mapped and sized. The

limitation is due to a combination of system electrical

noise and the detection of non-particle light scatter

signals, such as those created by Rayleigh scatter,

surface roughness and system optics. Operation near

this noise floor limits the utility of this guide for LLSs

of those sizes.

4.1.4 Measurements made near the wafer edge often

result in large numbers of false counts called edge blast.

These counts are caused by small amounts of stray light

propagating near the incident beam that scatter from the

relatively rough wafer edge back into the detector

optics. Under certain combinations of sensitivity and

edge exclusion, light scattered from these effects may

cause false counts within the FQA.

4.1.5 Types of LLS signals that may be mis-identified

as scratches include lines of particles, pits, false counts,

stacking faults, slip, and spin dry residue.

4.1.6 Closely spaced features may be counted as a

single scattering event because the scanning spot size is

generally much larger than the feature diameter.

4.1.7 Scratch orientation usually affects scanner

response. Thus the minimum detectable scratch cross-

section may vary with orientation.

5 Referenced Standards

5.1 SEMI Standards

SEMI M1  Specifications for Polished Mono-

crystalline Polished Silicon Wafers

SEMI M53 — Practice for Calibrating Scanning

Surface Inspection Systems using Depositions of

Monodisperse Polystyrene Latex Sphere on

Unpatterned Semiconductor Wafer Surfaces

NOTICE: Unless otherwise indicated, all documents

cited shall be the latest published versions.

SEMI M35-1104 © SEMI 1999, 1104 3

6 Terminology

6.1 Most terminology used in this guide is defined in

SEMI M1 and/or SEMI MF1241.

6.2 Other terms are defined as follows:

6.2.1 extended light scatterer (XLS)



a feature larger

than the spatial resolution of the inspection equipment,

on or in a wafer surface, resulting in increased light

scattering intensity relative to that of the surrounding

wafer, sometimes called an area defect (see

SEMATECH # 95082941A-TR, Section 8).

6.2.2 power spectral density  statistical function that

shows how the mean-square (rms)

of a given quantity

is distributed among the various surface spatial

frequencies inherent in the profile height. Also known

as power spectrum.

NOTE 1: For additional information see the extended

discussion of this term in SEMI MF1811.

6.2.3 scanning surface inspection system (SSIS)



instrument for rapid examination of the entire quality

area on a wafer to detect the presence of localized light

scatterers or haze or both, also called particle counter

and laser surface scanner.

7 Specifications

7.1 Specification guidelines are given below for

several different LLSs and XLSs.

7.1.1 Generic LLS  There shall be no more than N

LLSs (particles or pits) of size greater than or equal to

D nm latex sphere equivalent (LSE) diameter on the

wafer within the fixed quality area (FQA).

7.1.1.1 Options: Size ranges and counts may be

specified using an edge-referenced edge exclusion, if

agreed upon between supplier and customer.

7.1.2 Particles  There shall be no more than N

particles of size greater than or equal to D nm LSE

diameter on the wafer within the FQA. Size ranges and

counts may be specified.

7.1.2.1 Options: Size ranges and counts may be

specified using an edge-referenced edge exclusion, if

agreed upon between supplier and customer.

7.1.3 Pits  There shall be no more than N pits of size

greater than or equal to D nm in LSE diameter on the

wafer within the FQA. Size ranges and counts may be

specified.

7.1.3.1 Options: Size ranges and counts may be

specified using an edge-referenced edge exclusion, if

agreed upon between supplier and customer.

7.1.4 Scratches  There shall be no more than N

scratches of length greater than or equal to L nm on the

wafer within the FQA.

7.1.4.1 Options: Size ranges and counts may be

specified using an edge-referenced edge exclusion, if

agreed upon between supplier and customer.

7.1.4.2 Scratch aspect ratios different than 5:1 and

minimum lengths may be used by agreement of

supplier and customer.

7.1.5 Generic XLS 

There shall be no generic XLSs

of N ppm or greater in an area larger than A mm

within

the FQA.

7.1.6 Haze (Using Defined Conditions)  Either local

haze or average haze may be specified as follows: The

haze shall not exceed N ppm over the wafer surface

when measured over a solid angle of



sr of circular

cross section centered about the surface normal with a



nm laser source of a specified polarization incident on

the sample at



degrees. Suppliers and customers may

agree to use other statistics of the wafer haze

distribution in haze specifications.

NOTE 2: For example: the median wafer haze shall not

exceed M ppm; the standard deviation of wafer haze shall not

exceed S ppm; the inter-quartile range of wafer haze shall not

exceed IQR ppm. Statistics based on the log of the haze

distribution may also be used.

7.1.7 Haze (Using an Instrument Definition)  Either

local haze or average haze may be specified in the

following way. The haze shall not exceed N ppm over

the wafer surface when measured with a model XXX

particle scanner under YYY operating conditions.

Suppliers and customers may agree to use other

statistics of the wafer haze distribution in haze

specifications (see Note 2).

7.2 Specifications may be selected from Table 1.

8 Related Document

8.1 Many terms associated with examination of wafer

surfaces are defined in the following SEMATECH

report:

8.1.1 Glossary of Terms, SEMATECH Technology

Transfer Document # 95082941A-TR

1 Available from SEMATECH, 2706 Montopolis Drive, Austin, TX,

tel.: 512.356.3500, fax: 512.779.2826, website:

www.sematech.org

Table 1 Specification Elements Related to Automatic Inspection of Silicon Wafer Surfaces

Parameter Specification Elements Specified Measurement Conditions

1. Generic LLS ___, max number with LSE dia > __nm,

nominal edge exclusion of __ mm

2. Particles ___, max number with LSE dia > __nm

nominal edge exclusion of __ mm

3. Pits ___, max number with LSE dia > __nm

nominal edge exclusion of __ mm

4. Scratches ___, max number

length >

__ m

nominal edge exclusion of __ mm

5. Generic XLS __ ppm, max with area > __ mm

nominal edge exclusion of __ mm

6. Haze (conditions) __ ppm, max with __ degree incident angle,

at __ nm wavelength,

at __ polarization,

over __ sr solid collection angle,

in __degree polar direction and __

degree azimuthal direction,

nominal edge exclusion of __ mm

7. Haze (instrument) __ ppm, max

(or other statistics)

with model XXX SSIS

under YYY conditions

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.

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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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