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The present Fourier Transform Infrared (FTIR) spectrometer technique calibrates the temperature of a wafer in an epitaxial reactor within less than 10 C.
English (United States)
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Epitaxial Reactor Wafer Temperature Calibration Using FTIR Spectroscopy
The present Fourier Transform Infrared (FTIR) spectrometer technique
calibrates the temperature of a wafer in an epitaxial reactor within less than 10 C.
Ion-implanted blanket or 9 pattern wafers are used. Initial reflectivity vs.
wave number traces are made using a FTIR spectrometer to preselect wafers
with known plasma resonance characteristics, as shown in Fig. 1. The peak in
the trace has been associated with the plasma resonance which comes from the
interaction of the infrared photons with the free carriers in a semiconductor
material. The peak wave number and the reflectivity value both characterize
initial starting wafers. This guarantees constant C(o) and x(j) for a subcollector
These wafers are used in the reactor and heat treated at various
temperatures as read by a digital voltmeter (DVM) on the reactor panel and over
a fixed time period set by the process. FTIR traces are again measured. A shift
in the plasma resonance frequency towards lower wave number with a lower
reflectivity is shown in Fig. 2 as a function of the temperature of prebake. This
occurs due to the removal of surface impurity from the test wafers and is a
function of temperature and time of the prebake.
A table showing the DVM reading on the reactor panel, the plasma
resonance frequency, and the reflectivity value all define one temperature point
for the reactor. Such a measurement is made on any epitaxia...