Monitoring wafer temperature during thermal processing of wafers by measuring sheet resistance of a test wafer
First Claim
1. A test wafer that is included with a lot of product wafers during thermal processing of the product wafers to determine a product wafer temperature achieved at the product wafers during the thermal processing of the product wafers, the test wafer comprising:
- a lightly doped silicon wafer having a bare sheet resistance of 10 Ω
/square to 40 Ω
/square; and
a layer of titanium deposited on the lightly doped silicon wafer after the lightly doped silicon wafer is precleaned, the layer of titanium having a predetermined thickness such that an initial sheet resistance measured on top of the layer of titanium is 6.3±
0.2 Ω
/square, and wherein a measurement of the initial sheet resistance at a plurality of locations on the test wafer results in a standard deviation that is less than 1% of a mean of the measurement of the initial sheet resistance at the plurality of locations.
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Abstract
A method for monitoring the temperature of a product wafer during thermal processing of the product wafer in an emissivity independent thermal processing system includes processing a test wafer in the emissivity independent thermal processing system that thermally processes the product wafer. The test wafer is pretreated before being thus placed in the thermal processing system. The test wafer is thermally processed following a substantially same thermal processing recipe as that used for thermal processing of the product wafers. After the thermal processing of the test wafer, a sheet resistance of the test wafer is measured. This sheet resistance is correlated to a wafer temperature at the test wafer that was achieved during the thermal processing of the test wafer. Because the product wafer and the test wafer are thermally processed within an emissivity independent thermal processing system, the test wafer temperature is correlated to a product wafer temperature at the product wafer that was achieved during the thermal processing of the product wafer. With such monitoring of the product wafer temperature during actual thermal processing of the product wafer, thermal processing may be more tightly controlled to ensure that a thermal processing recipe is accurately followed.
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Citations
3 Claims
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1. A test wafer that is included with a lot of product wafers during thermal processing of the product wafers to determine a product wafer temperature achieved at the product wafers during the thermal processing of the product wafers, the test wafer comprising:
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a lightly doped silicon wafer having a bare sheet resistance of 10 Ω
/square to 40 Ω
/square; anda layer of titanium deposited on the lightly doped silicon wafer after the lightly doped silicon wafer is precleaned, the layer of titanium having a predetermined thickness such that an initial sheet resistance measured on top of the layer of titanium is 6.3±
0.2 Ω
/square, and wherein a measurement of the initial sheet resistance at a plurality of locations on the test wafer results in a standard deviation that is less than 1% of a mean of the measurement of the initial sheet resistance at the plurality of locations. - View Dependent Claims (2, 3)
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Specification