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SEMI M1-0305 © SEMI 1978, 2005 44 RELATED INFORMATION 2 TEST METHODS NOTICE : This related information is not an official p art of SEMI M1 and is not intended to modify or supersede the official sta ndard. This inform at…

SEMI M1-0305 © SEMI 1978, 2005 43

RELATED INFORMATION 1

SURFACE METAL CONTAMINATION

NOTICE: This related information is not an official part of SEMI M1 and is not intended to modify or supersede

the official standard. Approval was by full letter ballot procedures with publication authorized by the NA Regional

Standards Committee beginning with the 1995 edition of the standard. Determination of the suitability of the

material is solely the responsibility of the user.

R1-1 Scope

R1-1.1 Maximum allowable surface metal contamination levels for wafers to be used in integrated circuit (IC)

fabrication generally depend upon the IC device density and upon the IC process design. In general, as the device

density increases, the allowable surface metal contamination levels become lower.

R1-1.2 This related information is intended to provide guidance regarding allowable surface concentrations of metal

contaminants that have been reported to be deleterious to circuit and device performance.

R1-2 Suggested Allowable Surface Metal

Contamination Levels for 1 µm Geometries

R1-2.1 Table R1-1 lists suggested surface metal limits for

circuits and devices with a minimum linewidth in the

range of 0.8 µm to 1.2 µm for two alkali metals (Na, K), a

light metal (Al), and five heavy metals (Cr, Fe, Ni, Cu,

Zn). These are same elements as are listed in the items

under Section 2-7 of Table 1, Part 2, and they are listed in

the same order as they appear in that table.

Contaminant levels in Table R1-1 are significantly higher than

would be allowed for leading edge technologies at the time of

approval of this standard.

R1-3 Test Methods

R1-3.1 The test methods suitable for use in determining

the levels of each surface metal contaminant are listed in

the items under Section 2-7 of Table 1, Part 2. This list

and the related discussion of these test methods in Related Information 2 should be referenced in selecting methods

appropriate for testing the individual surface metals.

Table R1-1 Suggested Polished Wafer Surface

Metal Contamination Limits Appropriate to Circuits

and Devices with a Minimum Linewidth in the

Range 0.8 µm to 1.2 µm

Element Contaminant Level

Sodium (Na)

Not greater than 1  10

atoms/cm

Aluminum (Al)

Not greater than 1  10

atoms/cm

Potassium (K)

Not greater than 1  10

atoms/cm

Chromium (Cr)

Not greater than 1  10

atoms/cm

Iron (Fe)

Not greater than 1  10

atoms/cm

Nickel (Ni)

Not greater than 1  10

atoms/cm

Copper (Cu)

Not greater than 1  10

atoms/cm

Zinc (Zn)

Not greater than 1  10

atoms/cm

SEMI M1-0305 © SEMI 1978, 2005 44

RELATED INFORMATION 2

TEST METHODS

NOTICE: This related information is not an official part of SEMI M1 and is not intended to modify or supersede

the official standard. This information was developed during the revision of this standard in 2004. It is based in part

on information previously published as part of SEMI M28, withdrawn in October 2000. Approval was by full letter

ballot procedures with publication authorized by the NA Regional Standards Committee on November 4, 2004.

Determination of the suitability of the material is solely the responsibility of the user.

R2-1 Scope

R2-1.1 This Related Information Section discusses aspects of the various test methods listed in Table 1 together

with additional information about other test methods that are not listed in Table 1 but either have been or still are

used in the industry.

R2-1.2 The next section contains references to the test methods that are not cited in the main body of SEMI M1 but

that are discussed here. The various test methods are discussed in order that the items they cover are listed in Table

R2-1.3 Note that silicon wafers are extremely fragile. While the mechanical dimensions of a wafer can be

measured by use of tools such as micrometer calipers and other conventional techniques, the wafer may be damaged

physically in ways that are not immediately evident. Special care must, therefore, be used in the selection and

execution of measurement methods.

NOTICE: This section 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 practices and determine the

applicability of regulatory or other limitations prior to use.

R2-2 Referenced Standards

R2-2.1 The standards listed in this section are referenced only in this related information. See Section 4 for other

standards that are referenced in this related information.

R2-2.2 SEMI Standards

SEMI M49 — Guide for Specifying Geometry Measurement Equipment for Silicon Wafers for the 130 nm

Technology Generation

SEMI M50 — Test Method for Determining Capture Rate and False Count 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 MF43 — Test Methods for Resistivity of Semiconductor Materials

SEMI MF154 — Guide for Identification of Structures and Contaminants Seen on Specular Silicon Surfaces

SEMI MF398 — Test Method for Majority Carrier Concentration in Semiconductors by Measurement of

Wavenumber or Wavelength of the Plasma Resonance Minimum

SEMI MF723 — Practice for Conversion Between Resistivity and Dopant Density for Boron-Doped, Phosphorus-

Doped, and Arsenic-Doped Silicon.

SEMI MF1527 — Guide for Application of Silicon Certified Reference Materials and Reference Wafers for

Calibration and Control of Instruments for Measuring Resistivity of Silicon

SEMI MF1529 — Test Method for Sheet Resistance Uniformity Evaluation by In-Line Four-Point Probe with the

Dual-Configuration Procedure

SEMI MF1618 — Practice for Determination of Uniformity of Thin Films on Silicon Wafers

SEMI MF1810 — Test Method for Counting Preferentailly Etched or Decorated Structural Defects on Silicon

Wafers

SEMI M1-0305 © SEMI 1978, 2005 45

R2-2.3 JEITA (formerly JEIDA) Standard

EM-3505 — Height Calibration in 1 nm Order for AFM

R2-2.4 DIN Standards

50430 — Measurement of the Electrical Resistivity of Silicon or Germanium Single Crystals in Bars by Means of

the Two-point-probe Direct Current Method

50444 — Conversion Between Resistivity and Dopant Density; Silicon

R2-2.5 ANSI Standard

ANSI/ASME B46.1 — Surface Texture (Surface Roughness, Waviness, and Lay)

R2-2.6 ISO Standards

ISO 4287/1 — Surface Roughness – Terminology – Part 1: Surface and its Parameters

ISO 14644/1 — Clean Room and Associated Controlled Environments — Classification of Air Cleanliness

NOTICE: Unless otherwise indicated, all documents cited shall be the latest published versions.

R2-3 General Characteristics

R2-3.1 Crystal Orientation—The crystallographic orientation of the source crystal can be determined by the x-ray

methods of SEMI MF26, JEITA EM-3501, or DIN 50433/1, the optical method of SEMI MF26 or DIN 50433/2, or

the Laue method of DIN 50433/3. X-ray methods are most commonly used by wafer suppliers.

{Need some

discussion here about differences between MF26 and EM-3501}}

R2-3.2 Conductivity Type—One of the five methods of SEMI MF42, one of the methods of JIS H 0607, or one of

the four methods of DIN 50432 should be used to determine conductivity type. This quantity is generally well

controlled by silicon wafer suppliers and is not usually verified on incoming.

R2-3.3 Many of these tests need to be carried out in cleanroom environments of ISO Class 4, 5, or 6 depending on

the cleanliness requirements. These classes are defined in ISO 14664-1.

R2-4 Electrical Characteristics

R2-4.1 Resistivity of wafers is most appropriately determined for referee purposes by SEMI MF84 or DIN 50431.

Under some circumstances these tests may be considered destructive, and an alternative means may be required.

One nondestructive test is SEMI MF673, having a range from 0.0001 to 100 ·cm. Another nondestructive test is

SEMI MF398, which is limited to carrier concentrations in the ranges from 1.5 × 10

to 1.5 × 10

3

for n-type

silicon and from 3 × 10

to 5 × 10

3

for p-type silicon, and has only moderate inter-laboratory precision. Other

older methods that require a bar-shaped test specimen include SEMI MF43 and DIN 50430; these methods are no

longer in general use. It is also possible to establish the dopant density from room temperature measurements in

silicon using SEMI MF723 (for boron, phosphorus, or arsenic doped silicon) or DIN 50444 (for boron and

phosphorus doped silicon only). SEMI MF1527 is a useful standard in describing ways of ensuring that resistivity

measuring instruments are performing correctly.

R2-4.2 Radial Resistivity Variation is generally determined by SEMI MF81 or DIN 50435. These test methods use

several different measurement positions so the desired position must be specified. It is also possible to measure the

resistivity in one of the circular patterns specified in SEMI MF1618 using SEMI MF1529 as the resistivity

measurement method.

R2-4.3 Resistivity Striations can generally be viewed visually using one of the techniques discussed in Section R2-

9. For an electrical measurement, spreading resistance (SEMI MF525) is generally employed but this is strictly an

off-line measurement.

R2-4.4 Minority Carrier Lifetime can be measured by a number of methods. The photoconductive decay methods

(SEMI MF28, JIS H 0604, and DIN 50440/1 all require the use of special test specimens; Microwave reflectivity

measurements (SEMI MF1535 and JEITA EM-3502) are applicable to measurements on wafers, but special surface

passivation procedures may be required to obtain meaningful results. Minority carrier lifetime may also be inferred

from measurements made in accordance with SEMI MF1388, which yields generation lifetime if the measurements