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.
Scope
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 (purchase separately)
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
Revision History
SEMI MF1239-0305 (Reapproved 0222)
SEMI MF1239-0305 (Reapproved 0416)
SEMI MF1239-0305 (Reapproved 0211)
SEMI MF1239-0305 (technical revision)
SEMI MF1230-02 (first SEMI publication)
