ASTM F1894 - 98(2011)

    Test Method for Quantifying Tungsten Silicide Semiconductor Process Films for Composition and Thickness

    Active Standard ASTM F1894 | Developed by Subcommittee: F01.17

    Book of Standards Volume: 10.04


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    Significance and Use

    This test method can be used to ensure absolute reproducibility of WSix film deposition systems over the course of many months. The time span of measurements is essentially the life of many process deposition systems.

    This test method can be used to qualify new WSix deposition systems to ensure duplicability of existing systems. This test method is essential for the coordination of global semiconductor fabrication operations using different analytical services. This test method allows samples from various deposition systems to be analyzed at different sites and times.

    This test method is the chosen calibration technique for a variety of analytical techniques, including, but not limited to:

    Electron spectroscopy for chemical analysis (ESCA or XPS),

    Auger electron spectroscopy (AES),

    Fourier transform infrared red spectroscopy (FTIR),

    Secondary ion mass spectrometry (SIMS), and

    Electron dispersive spectrometry (EDS) and particle induced x-ray emission (PIXE).

    1. Scope

    1.1 This test method covers the quantitative determination of tungsten and silicon concentrations in tungsten/silicon (WSix) semiconductor process films using Rutherford Backscattering Spectrometry (RBS). (1) This test method also covers the detection and quantification of impurities in the mass range from phosphorus (31 atomic mass units (amu) to antimony (122 amu).

    1.2 This test method can be used for tungsten silicide films prepared by any deposition or annealing processes, or both. The film must be a uniform film with an areal coverage greater than the incident ion beam (2.5 mm).

    1.3 This test method accurately measures the following film properties: silicon/tungsten ratio and variations with depth, tungsten depth profile throughout film, WSix film thickness, argon concentrations (if present), presence of oxide on surface of WSix films, and transition metal impurities to detection limits of 1×1014 atoms/cm2.

    1.4 This test method can detect absolute differences in silicon and tungsten concentrations of ±3 and ±1 atomic percent, respectively, measured from different samples in separate analyses. Relative variations in the tungsten concentration in depth can be detected to ±0.2 atomic percent with a depth resolution of ±70.

    1.5 This test method supports and assists in qualifying WSix films by electrical resistivity techniques.

    1.6 This test method can be performed for WSix films deposited on conducting or insulating substrates.

    1.7 This test method is useful for WSix films between 20 and 400 nm with an areal coverage of greater than 1 by 1 mm2.

    1.8 This test method is non-destructive to the film to the extent of sputtering.

    1.9 A statistical process control (SPC) of WSix films has been monitored since 1993 with reproducibility to ±4 %.

    1.10 This test method produces accurate film thicknesses by modeling the film density of the WSix film as WSi2 (hexagonal) plus excess elemental Si2. The measured film thickness is a lower limit to the actual film thickness with an accuracy less than 10 % compared to SEM cross-section measurements (see 13.4).

    1.11 This test method can be used to analyze films on whole wafers up to 300 mm without breaking the wafers. The sites that can be analyzed may be restricted to concentric rings near the wafer edges for 200-mm and 300-mm wafers, depending on system capabilities.

    1.12 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

    1.13 This standard does not purport to address all of the safety concerns, 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 limitations prior to use. The reader is referenced to Section 8 of this test method for references to some of the regulatory, radiation, and safety considerations involved with accelerator operation.


    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    E135 Terminology Relating to Analytical Chemistry for Metals, Ores, and Related Materials

    E673 Terminology Relating to Surface Analysis

    E1241 Guide for Conducting Early Life-Stage Toxicity Tests with Fishes


    ICS Code

    ICS Number Code 29.045 (Semiconducting materials)

    UNSPSC Code

    UNSPSC Code 41115403(Spectrometers); 23211101(Semiconductor process systems)


    DOI: 10.1520/F1894-98R11

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