A Simple Optical Pyrometer for in Situ Temperature Measurement During CW Argon Laser Annealing
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A SIMPLE OPTICAL PYROMETER FOR IN SITU TEMPERATURE MEASUREMENT DURING CW ARGON LASER ANNEALING
T.O. SEDGWICK IBM Thomas J. Watson Research Center, Yorktown Heights, NY 10598
ABSTRACT A standard optical disappearing hot wire micropyrometer was modified with a long working distance magnifier to enlarge the laser heated spot so that the maximum temperature of the center of the spot could be observed and measured with some certainty. In situ temperature measurements were made on As ion implanted Si chips using an Argon Ion laser with the beam slightly defocused to a 50-100pm diameter spot on the Si surface. The data curves show a linear function of measured temperature with laser power up until the melting point is reached. By using the Si m.p. as a calibration point, the temperature can be reproducibly measured within a few tens of degrees. Comparisons of actual re-growth rates with those calculated from the well known solid state Si regrowth expression as a function of temperature yields good agreement between measured and calculated temperature.
INTRODUCTION Laser annealing is being actively investigated as an alternative to furnace annealing for the regrowth of silicon single crystal which has been amorphized by ion implantation. In the case of CW annealing, there is evidence that the silicon is regrown by the solid state mechanism which is well known from fur1 2 nace annealing studies. , In CW Ar laser annealing, however, the time for regrowth is in the millisecond range as compared to minutes or hours for furnace annealing while the temperature is presumably in the range 900-1000 C. 3 Except for recently reported Raman measurements, and an early report of the 4 present results there has not been a technique available to measure the temperature of the Si during CW Ar laser annealing which could be used to confirm the details of the solid state growth mechanism in the millisecond time regime. It should be noted that the temperature of a uniformly heated Si wafer (through its thickness) has been monitored by transmission measurements of 10.6m radia5 tion. In this paper, the use of a modified optical pyrometer for in-situ temperature measurement of silicon during CW Argon laser annealing is reported. The resulting measured temperatures and amorphous silicon regrowth rates were found to be consistent with the previously reported solid state regrowth rate 6 for Si from furnace annealing. Samples of
Si were ion implanted with 50 or 100 keV As ions at doses 1 4 15 2 of ixl0 or ix10 atoms/cm . For laser annealing the samples were mounted on a hot stage held at 350°C and the stage was driven in a serpentine scan by stepping motors (10pm steps) at an average translation rate of 2cm/sec. The overlap from one scan to the next was varied from ca 85% (10m step between scans) to less than 10% (70Pm steps between scans). The 25 watt Spectra Physics Model 170 Ar ion laser was operated all lines and multimode. The laser power reported was that of the internal power meter on the Spectra Physics laser with no correction. The
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