- SEMI MF1239 - Test Method for Oxygen Precipitation Characteristics of Silicon Wafers by Measurement of Interstitial Oxygen Reduction
This Standard was technically approved by the Silicon Wafer Global Technical Committee. This edition was approved for publication by the global Audits and Reviews Subcommittee on February 1, 2016. Available at www.semiviews.org and www.semi.org in April 2016; originally published by ASTM International as ASTM F1239-89; previously published February 2011.
NOTICE: This Document was reapproved with minor editorial changes.
Oxide precipitates in the bulk of a silicon wafer can act as gettering sites for contamination that may be introduced during manufacture of circuits and devices. This contamination (usually metallic impurities), if not gettered, can reduce device manufacturing yields and degrade device or circuit performance. Thus, the oxygen precipitation characteristics of the silicon wafer can significantly affect both yields and performance.
Although interstitial oxygen concentration is an important factor in affecting the amount of oxygen precipitation that occurs in silicon during a specific thermal cycle, the presence of other impurities such as carbon or nitrogen, and differences in dopant type and density, thermal history, or defect properties of the crystal can also affect the precipitation characteristics. Thus, it is frequently necessary to choose particular material properties and preparation techniques to obtain the desired precipitation characteristics for a particular application.
This Test Method may be used to compare the oxygen reduction of two or more groups of silicon wafers. This Test Method is based on thermal cycles that simulate certain common device processing cycles.
Cycle A — A one-step precipitation cycle, provides an indication of the native nucleation sites present in the as-received wafers.
Cycle B — A two-step nucleation-precipitation cycle, simulates the precipitation that occurs in normal n-MOS device processing.
These test methods may be used to compare qualitatively the precipitation characteristics of two or more groups of wafers.
These test methods may also be used to determine the uniformity of oxygen reduction across a wafer (in conjunction with SEMI MF951) or from wafer to wafer within a lot.
These test methods cover complementary procedures for testing the oxygen precipitation characteristics of silicon wafers. It is assumed that the precipitation characteristics are related to the amount of interstitial oxygen lost during specified thermal cycles.
These test methods may be applied to any n- or p-type Czochralski silicon wafers of any orientation whose thickness, resistivity, and surface finish are such as to permit the oxygen concentration to be determined by infrared absorption and whose oxygen concentration is such as to produce measurable oxygen loss.
These test methods are not suitable for determining the width or characteristics of a ‘denuded zone’, a region near the surface of a wafer that is essentially free of oxide precipitates.
Because these test methods are destructive, suitable sampling techniques must be employed.
Determination of material performance in actual device fabrication situations is beyond the scope of these methods. However, by comparing the results of these tests with actual device yields and performance, criteria for selection of specific material characteristics may be established.
The values stated in SI units are regarded as standard.
Referenced SEMI Standards
SEMI C28 — Specifications for Hydrofluoric Acid
SEMI C29 — Specifications and Guide for 4.9% Hydrofluoric Acid 10:1 v/v
SEMI C54 — Specifications and Guidelines for Oxygen
SEMI C59 — Specifications and Guidelines for Nitrogen
SEMI M59 — Terminology for Silicon Technology
SEMI MF951 — Test Method for Determination of Radial Interstitial Oxygen Variation Silicon Wafers
SEMI MF1188 — Test Method for Interstitial Atomic Oxygen Content of Silicon by Infrared Absorption with Short Baseline
SEMI MF1619 — Test Method for Measurement of Interstitial Oxygen Content of Silicon Wafers by Infrared Absorption Spectroscopy with p-Polarized Radiation Incident at the Brewster Angle