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SEMI M54-0304 © SEMI 2003, 2004 6 SEMI MF523 — Standard Practice for Unaided Visual Inspection of Polished Silicon Wafer Surfaces SEMI MF1241 — Standard Terminology of Silicon Technology 7.2 Other Docs 5 DIN 50443-2 — Te…

SEMI M54-0304 © SEMI 2003, 2004 5

methods include GDMS, SSMS, Secondary Ion Mass

Spectroscopy (SIMS) and atomic absorption

spectroscopy (AAS).

5.14 Surface contaminants are identified and quantified

with Time-of-Flight-SIMS (TOF-SIMS) and Total

Reflection X-Ray Fluorescence (TXRF). The latter

technique is difficult to apply for impurities with atomic

weight below those of the matrix elements Ga and As.

5.15 Deposition of high quality epitaxial layers without

chemical pre-cleaning depends on the surface oxide

structure of the substrate, as prepared by the supplier, as

well as the thermal oxide desorption and the epitaxial

deposition procedures of the purchaser. Hence an

individual supplier-purchaser specific evaluation is

necessary. Test epitaxy followed by layer quality

assessment is recommended.

5.16 The lateral substrate homogeneity is assessed by

automated analytic instrumentation elaborated to

generate topographic images of important material

parameters, including electrical resistivity, EL2

concentration, EPD and minority carrier lifetime.

Macroscopic (e.g. radial) variations as well as

mesoscopic fluctuations (generally correlated to the

cellular dislocation structure) may be assessed. Such

topographic analysis is provided, respectively, by

contactless capacitive resistivity mapping (see DIN

50448), EL2 absorption topography (see footnote 3),

specular light reflection topography and

photoluminescence topography. The first three

topography techniques provide quantitative data.

Photoluminescence topography gives qualitative

homogeneity information only, because the

interrelations between the luminescence intensity and

the various radiative and nonradiative recombination

processes are only partially understood. The details of

the topographic measurements, i.e. lateral resolution

and edge exclusion, must be defined by individual

supplier-purchaser agreement.

5.17 As precipitates, other inclusions and voids are

visualized with light scattering tomography (LST). At

present it is not possible to differentiate between these

scattering centers and to obtain quantitative information

concerning their concentration and size. Hence LST

images provide a qualitative information only.

5.18 Micro-roughness, also referred to as haze, is

indicated by a diffuse reflection of collimated, laterally

extended high intensity illumination from the wafer

surface. Localized haze and haze observed on

particular wafers of a batch indicate potentially

disadvantageous variations of surface quality. The

agreement should specify the conditions of observation

(e.g. illumination intensity).

5.19 Surface irregularities (stain, scratches, pits, orange

peel, dimples) are identified by high intensity

illumination or by standard and phase sensitive

(Nomarski) microscopy. Individual agreement is

recommended concerning the permitted surface density

of these defects.

6 Ordering Information

6.1 The material properties of SI GaAs substrates, as

described in Section 4, are addressed in the ordering

agreement using the tables given below. The

subdivisions into “important”, “optional” and “other”

specifications are suggested only, i.e. supplier and

purchaser may agree on an individual choice, taking

into account the respective application as well as cost

considerations.

6.2 In addition to specifying individual material

properties as listed below, the purchase order may

specify the fabrication procedures according to Sections

4.2 and 4.3.

6.3 Substrates are usually delivered in batches. The

batch homogeneity is defined in the purchasing

agreement by variation ranges of specified parameters.

The ordering agreement shall also state whether batches

must originate from one ingot or may be assembled

from several specified or unspecified ingots. In either

case the supplier guarantees compliance with the

specified batch homogeneity by control of fabrication

technology and appropriate test sample evaluations.

6.4 Table 1 lists the parameters that are considered

important to specify the material quality of SI GaAs

substrates. The level of importance may be adjusted

individually by taking into account the intended use for

implantation or epitaxy. The quoted absolute values

suggest a customary material specification, to be

adopted unless individual considerations warrant other

choices.

6.5 Table 2 lists optional parameters that are important

for specific applications only, hence may or may not be

considered relevant for a particular supplier/purchaser

agreement. For most of these parameters, standard test

methods at present do not exist.

6.6 Table 3 lists other parameters which in general

need not be specified, but are addressed for clarification

and to provide a basis for agreement in the event that a

purchaser desires to include such parameters into a

purchasing specification.

7 Related Documents

7.1 SEMI Standards

SEMI M1 — Specification for Polished

Monocrystalline Silicon Wafers

SEMI M54-0304 © SEMI 2003, 2004 6

SEMI MF523 — Standard Practice for Unaided Visual Inspection of Polished Silicon Wafer Surfaces

SEMI MF1241 — Standard Terminology of Silicon Technology

7.2 Other Docs

DIN 50443-2 — Testing of materials for semiconductor technology; recognition of defects and inhomogeneities in

semiconductor single crystals by X-ray topography; III-V-semiconductor compounds

Table 1 Important SI GaAs Material Parameter Specifications and Suggested Standard Values

Parameter Section Wafer

Diameter

Suggested Value Unit Verification

Technique

Standard Test

Method

Section

Carbon

concentration

4.7 n.a. 1 × 10

-3

LVM spectroscopy SEMI M30

DIN 50449-1

5.4

Electrical resistivity 4.11 n.a. >1 × 10

Ωcm

Hall effect

Capacitive probe

SEMI F76, M39

DIN 50448

5.5

Electron mobility 4.12 n.a. > 6000 cm

/Vs Hall effect SEMI F76, M39 5.6

EPD of LEC grown

material

4.13 150 mm

100 mm

76 mm

< 1.5 × 10

< 1.0 × 10

-2

Structural etching +

light reflection

ASTM F1404,

DIN 50454-1

5.7

EPD of VGF and

VB material

4.13 150 mm

100 mm

76 mm

< 1 ×10

< 5 × 10

-2

Structural etching,

light reflection,

microscopy

SEMI M36

DIN 50454-1

5.8

Particles with

diameter

≥ 300 nm

4.17 150 mm

100 mm

76 mm

< 100

< 40

< 20

Wafer with

edge exclusion

Laser scattering none 5.9

Microroughness

(haze)

4.17 n.a. not visible Wafer with

edge exclusion

High intensity

illumination

none 5.18

Table 2 Optional SI GaAs Material Parameter Specifications

Parameter Section Verification Technique Section

Average EL2

concentration 4.5 Optical absorption 5.10

Total concentration of impurities acting as

donors

4.6 GDMS, SSMS 5.11

Total concentration of impurities acting as

acceptors

4.7 GDMS, SSMS 5.12

Concentration of boron 4.9 DIN 50449-2, GDMS, SSMS, SIMS, AAS 5.13

Surface concentration of specified contaminants 4.17 TOF-SIMS, TXRF 5.14

Epi-ready qualification including shelf life 4.18 Supplier/purchaser specific 5.15

Surface irregularities (stain, scratches, pits,

orange peel, dimples)

4.17 High intensity illumination or microscopic

inspection (SEMI M15)

5.19

Table 3 Other SI GaAs Material Parameters

Parameter Section Verification Technique Section

Lateral variation of EL2

concentration 4.5 Optical absorption topography 5.10

Lateral variation of resistivity 4.11 Transient capacitance, DIN 50448 5.5

Lateral variation of EPD 4.14 Structural etching and light reflection, DIN

50454-1

5.8

5 Available from Deutches Institut für Normung e.V., Beuth Verlag GmbH, Burggrafenstrasse 4-10, D-10787 Berlin, Germany, website:

www.din.de

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