Temperature measuring method using radiation thermometer

Thermal measuring and testing – Temperature measurement – In spaced noncontact relationship to specimen

Reexamination Certificate

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Details

C374S126000, C374S001000

Reexamination Certificate

active

06283630

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a temperature measuring method using a radiation thermometer for measuring the temperature of a measuring object, such as a semiconductor wafer, and capable of calibrating the radiation thermometer before temperature measurement.
2. Description of the Related Art
Semiconductor device manufacturing methods include various heat treatment process, such as an annealing process for annealing a semiconductor wafer after a predetermined impurity has been added to the wafer by a doping process, and various thermal processes, such as film forming processes and etching processes. Since the temperature of the wafer is a significant parameter of the heat treatment process and the thermal process, the control of the temperature of the semiconductor wafer is very important.
A reference value of the result of processing for each recipe, i.e. a value of the result of processing possibly accurately reflecting the effect of the temperature prescribed by each recipe is determined. The reference value of the result of processing for each recipe may be the result obtained when the process is carried out according to the recipe while the temperature of the measuring object is measured by the radiation thermometer calibrated on the basis of temperatures measured by a thermocouple attached to the measuring object.
A radiation thermometer is used for the measurement of the temperature of a semiconductor wafer in a relatively high temperature range. The radiation thermometer measures the intensity of the thermal radiation of a measuring object and determines a temperature on the basis of the measured intensity of the thermal radiation. The emissivity of the semiconductor wafer is dependent on the surface roughness of the semiconductor wafer and the thickness of a film formed on the surface of the semiconductor wafer. Therefore, the temperature of the semiconductor wafer cannot accurately be measured by the radiation thermometer.
SUMMARY OF THE INVENTION
The present invention has been made in view of such a problem and it is therefore an object of the present invention to provide a temperature measuring method capable of accurately measuring the temperature of a measuring object by a radiation thermometer regardless of the surface condition of the measuring object.
The inventors of the present invention made studies to solve the foregoing problem and acquired knowledge that the reflectivity of a measuring object measured by using light of a wavelength that is not transmitted by the measuring object corresponds to the emissivity of the measuring object. A correction table for correcting a measured emissivity was produced on the basis of the reflectivity of the surface of a measuring object and the temperature of the measuring object measured by a thermocouple attached to the measuring object, and the emissivity was corrected by using the correction table.
However, the state of contact of the thermocouple with the measuring object was not reproducible and changed every time the thermocouple is attached to the measuring object. Consequently, measured temperature included an error and hence an accurate correction table could not be produced.
The inventors of the present invention made further studies and acquired knowledge that an accurate correction table can be produced on the basis of the reflectivity of a measuring object, and results of processing the measuring object by a process that provides a result corresponding to process temperatures, and that the temperatures of measuring objects can accurately be measured by a radiation thermometer even if the emissivities of the measuring objects differ from each other due to the difference between the measuring objects in surface condition, such as surface roughness.
The present invention has been made on the basis of the knowledge thus acquired. According to a first aspect of the present invention, a temperature measuring method of measuring a temperature of a measuring object by a radiation thermometer capable of approximating the relation between its output and the temperature of the measuring object by a predetermined straight line and of being calibrated by properly determining a slope and a y-intercept for the straight line, comprises the steps of repeating a procedure including the steps of measuring the reflectivity of a measuring object regarding the light of a wavelength that is not transmitted by the measuring object, and determining a slope and a y-intercept for a proper straight line for the measuring object on the basis of results of processing the measuring object by a process that provides a result corresponding to process temperature, for a plurality of measuring objects, to determine the relation between the reflectivity of the measuring object, and the slope and y-intercept of the proper straight line, and calibrating the radiation thermometer on the basis of the relation, and measuring a temperature of the measuring object.
According to a second aspect of the present invention, a temperature measuring method of measuring a temperature of a measuring object by a radiation thermometer capable of approximating the relation between its output and the temperature of the measuring object by a predetermined straight line and of being calibrated by properly determining a slope and a y-intercept for the straight line comprises the steps of: preparing a plurality of measuring objects differing from each other in surface condition and measuring the reflectivity of each measuring object regarding the light of a wavelength that is not transmitted by the same measuring object; determining a slope and a y-intercept for a proper straight line for each measuring object; determining the relation between the reflectivity of the measuring object, and the proper slope and y-intercept for the proper straight line on the basis of the determined slope and y-intercept for the straight line for each measuring object and the measured reflectivity of each measuring object; and calibrating the radiation thermometer on the basis of the relations and measuring a temperature of the measuring object; in which the step of determining a slope and a y-intercept for the straight line comprises the steps of: setting a plurality of slopes and a plurality of y-intercepts for the straight line, measuring temperature by the radiation thermometer by using each set of the slope and y-intercept for the straight line and subjecting the measuring object to a predetermined process that provides a result corresponding to process temperature by two recipes; expressing the result of processing by an equation as a function of the slope and y-intercept of the straight line for each recipe; determining reference value of the result of processing for each recipe; and calculating a slope and a y-intercept for a proper straight line for the measuring object by substituting the reference value into the equation for each recipe.
According to the present invention, a procedure for measuring the reflectivity of a measuring object regarding the light of a wavelength that is not transmitted by the measuring object, and for determining a slope and a y-intercept for the proper straight line for the measuring object on the basis of results of processing the measuring object by a process that provides a result corresponding to process temperatures is repeated for a plurality of measuring objects to determine the relation between the reflectivity of the measuring object, and the slope and y-intercept of the proper straight line, the radiation thermometer is calibrated on the basis of the relation, and the temperature of a measuring object is measured. Therefore, the radiation thermometer can accurately be calibrated even if different measuring objects have different surface conditions and different reflectivities. Problems resulting from an error in the measured temperature due to the variable contact condition of the thermocouple can be avoided by using the result of processing corresponding to process temperature ins

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