JPH0469531A - Temperature measuring method by radiation thermometer - Google Patents

Abstract

PURPOSE:To correct temperature with the output of the radiation thermometer and temperature conversion data by detecting the temperature, etc., of a body to be processed by a temperature measuring element and reading out the temperature conversion data which is characteristic to the body to be measured, etc., according to the detection data. CONSTITUTION:A wafer 10 to be measured is mounted on a supporting pin 12. Before this wafer 10 is processed, the wafer 10 is heated by a heating lamp 14 and placed in a heating state where the radiation thermometer 20 obtains an output A shown in figure 2. After this heat treatment, the output of a thermocouple 30 is monitored. Namely, the temperature detected by the thermocouple 20 is substituted in a function regarding an inclination S and an offset F which is stored in a table memory 32 to know an inclination S and an offset F which are characteristic to the top surface of the wafer. Thus, the emissivity in the reverse surface state of the wafer 10 to be measured is specified.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a temperature measurement method using a radiation thermometer.

(Prior Art) In recent years, semiconductors have made remarkable progress, and along with this, processing processes for manufacturing semiconductors are also required to be controlled with complexity and precision. In particular, the wafer temperature during the fabrication process has an important effect on the outcome of the fabrication process. For example, in CVD equipment, the surface temperature of a semiconductor wafer is closely related to the film formation conditions, and accurate measurement of the wafer temperature and accurate control of the temperature based on this is the key to precise control. It has become indispensable.

Conventionally, methods using a thermal lightning pair and methods using a radiation thermometer are known for measuring the wafer temperature. The measurement method using a radiation thermometer is superior in that temperature can be measured without direct contact with the wafer, which is the object to be measured, unlike thermocouples, and in that it has a quick response.

The principle of a radiation thermometer is that all objects emit infrared rays at their temperature, and by measuring the emitted infrared rays, the temperature of the object to be measured can be determined. The biggest problem with such radiation thermometers is that the emissivity changes depending on the condition of the radiation surface of the object to be measured. For example, in the case of a semiconductor wafer, the emissivity changes even at the same temperature depending on the roughness of the back surface of the wafer or the thickness of the film formed on the back surface. Therefore, it is not possible to accurately measure temperature using only the output of the radiation thermometer, and it is necessary to correct the output of the radiation thermometer according to the condition on the radiation surface of the object to be measured, that is, according to the emissivity. It is.

Conventionally, there have been methods that use reflectance, for example, to correct emissivity in real time. When the emissivity of the object to be measured is unknown, the emissivity ε can be found as ε-1-ρ (ρ is the reflectance).

(Problems to be Solved by the Invention) With the conventional method described above, it is difficult to accurately determine the reflection intensity. This detection sensor has a problem in that radiation light from sources other than the object to be measured enters the sensor, making it impossible to accurately measure temperature. In the present invention, in order to make it possible to measure the temperature of the object to be measured with a measurement accuracy that enables accurate temperature control of the object to be measured, information on the back surface of the object to be measured, that is, the roughness of the radiation surface, which causes measurement errors, is provided. Alternatively, it is possible to ultimately control the temperature of the object to be measured with sufficient accuracy without making a sharp distinction between the degree of film attachment to the radiation surface, and without requiring a special configuration for correction according to emissivity. The present invention provides a temperature measurement method using a radiation thermometer that makes it possible.

``Structure J of the Invention (Means for Solving the Problems) The present invention provides a radiation thermometer that measures temperature based on radiation from an object to be measured, and a temperature sensor that measures the temperature of the object to be measured or its surrounding temperature. Collect temperature conversion data in advance and create a table for multiple types of reference objects with different radiation surface conditions using a sensor, and before measuring the temperature of the object to be measured, calculate the output value of a certain radiation thermometer. Detect the temperature of the object to be measured or the ambient temperature thereof at the time of the measurement using a temperature measuring element, and read out the temperature conversion data specific to the object to be measured from the table based on this data. The present invention is characterized in that the temperature is corrected from the output of the meter and the temperature conversion data.

(Function) The emissivity of the object to be measured differs depending on various conditions such as the roughness of the radiation surface or the degree of coating on the radiation surface, and it is difficult to obtain information on the radiation surface for each object to be measured. It is extremely difficult.

The present invention measures the temperature of multiple types of reference objects with different radiation surface states in advance using a radiation thermometer and a temperature measurement element, collects temperature conversion data for each reference object, and stores it in a table. put. Next, before measuring the temperature of each object to be measured, it is selected which back surface emissivity corresponds to this object to be measured. That is, when the output of the radiation thermometer is fixed for each object to be measured, the temperature of the object or its surrounding temperature at that time is measured by the temperature measuring element. This temperature is not necessarily the exact temperature of the object to be measured, but is obtained as a temperature that depends on the state of the radiation surface of the object to be measured.

As the temperature and LR calculation data for the reference object that has been tabulated in advance, it has the radiation thermometer output and the temperature data of the object to be measured at this time, and as a result, based on the two data obtained from the object to be measured, , it can be identified that the object to be measured corresponds to a certain type of emissivity on the table. and,
When measuring the temperature of an individual object to be measured, the output of the radiation thermometer is calculated using temperature conversion data. It can be converted to the correct body temperature.

(Example) Hereinafter, an example of a temperature measurement method using a radiation thermometer to which the present invention is applied will be specifically described with reference to the drawings.

In FIG. 1, the semiconductor wafer 11-O is supported at three points by, for example, three support pins 12. A plurality of heating lamps 14 are provided above the surface of the wafer 10, and the rewafer 10 is heated by the heating lamps 14.

A radiation thermometer 20 is provided below the wafer 10. The output of this radiation thermometer 20 is input to a temperature calculation circuit 24 via an analog/digital (A/D) converter 22.

This temperature calculation circuit 24 inputs the output of the radiation thermometer 20, performs correction calculations on it based on correction data, outputs this temperature information to a lamp drive circuit 28 for driving the heating lamp 14, temperature to a predetermined temperature.

A thermocouple 30 and a table memory 32 are provided to perform correction calculations in the temperature calculation circuit 24. The thermocouple 30 is used to measure the heated temperature of the wafer 10 depending on the state of the radiation surface (back surface) of the wafer 10, and is provided to measure the thermal conduction of the wafer 10. In this embodiment, the thermocouple 30 is provided at a location away from the wafer 10 to measure the ambient temperature, but the thermocouple 30 may be brought into direct contact with the wafer 10. The table memory 32 stores temperature conversion data collected using the radiation thermometer 20 and thermocouple 30 for a plurality of types of reference objects having different radiation surface states.

Information stored in the table memory 32 will be explained with reference to FIG. 2.

For example, five dummy wafers are prepared, and each of the five dummy wafers has a different back surface roughness or a different film coating state on the back surface. These five dummy wafers are referred to as N001 to No.5. A dummy wafer No. 1 is placed on the support pin 12, and while the temperature is gradually raised using a heating lamp 14, the power of the radiation thermometer 20 and the output of the thermocouple 30 at that time are collected. As a result, as shown in FIG. 2, by taking the output of the radiation thermometer 20 on the horizontal axis and the temperature of the sea urchin, which is the output of the thermocouple 30, on the vertical axis, the dummy wafer of NO1 changes linearly. temperature information can be obtained. Similarly,
Regarding the dummy wafers No. 2 to No. 5, the information as shown in FIG. 2 is collected to obtain the crack 7. As is clear from Fig. 2, T-5Xt+F Here, T: Wafer temperature S; Slope t: Radiation thermometer output F; Offset value In this way, temperature information regarding the dummy wafers No. 1 to No. 5 is obtained. By doing this, it is possible to obtain the slope S of the temperature formula and the offset value F for each dummy wafer with a different back surface state.

Then, when the output of the radiation thermometer 20 is fixed, for example, at A in FIG. 2, the radiation thermometer is As a function of the thermocouple output T when the output of 20 is fixed at the A value, the relationship of slope - S (T) offset - F (T) is obtained by approximating, for example, by the method of least squares, and is stored in the table memory 32. , each of these functions will be stored.

Next, the operation of the temperature measuring device having the above configuration will be explained. The wafer 1o, which is the object to be measured, is placed on the support pins 12, and before processing the wafer 10, the following operations are performed. That is, the heating lamp 14 heats the wafer l.
By heating O, the radiant heat radiation 20 maintains the heated state at a value that provides the output A shown in FIG. For example, a 1° wafer is heat-treated at 350° C. for 35 seconds. and,
After performing this heat treatment, the output of the thermocouple 3o is monitored.

The temperature of this thermocouple 30 reflects the temperature of the wafer 10 depending on the state of the back surface of the wafer 1o. Therefore, in FIG. 2, the measured temperature of the thermocouple 30 is plotted on the vertical axis, and the intersection of this wafer temperature and the fixed value A, which is the output of the radiation thermometer 20, is obtained. In other words, it is possible to know the slope S and offset value F specific to the back surface of the rewafer from this point of intersection. That is, in the functions related to the slope S and offset F stored in the table memory 32,
By manually measuring the temperature detected by the thermocouple 20, the slope S and offset value F specific to the back surface of the wafer can be determined.

Through such operations, it is possible to specify the emissivity depending on the state of the back surface of the wafer 1o, which is the object to be measured.

According to the above embodiment, the thermocouple 30 is not required when measuring the temperature of 1° of the wafer, but is used to collect temperature conversion data regarding the dummy wafer and the wafer 10 which is the object to be measured.
It is used only to identify the state of the back surface when it is installed. Therefore, this thermocouple 30 is not necessarily required when the wafer 10 as the object to be measured is subsequently processed under certain processing conditions. Therefore, it is not necessary to perform temperature measurement using the conventional direct contact method using thermocouples, and the non-contact type radiation thermometer 20 can be used with high accuracy, at least with the same temperature accuracy as the direct contact method using thermocouples. It becomes possible to measure temperature.

Note that the present invention is not limited to the above-mentioned embodiments, and various modifications can be made within the scope of the gist of the present invention. For example, the above-mentioned thermocouple 30 is used as a temperature measuring element used to measure temperature conversion data about a reference object and to identify a reference object that is similar to the measured object.
It is not limited to. Furthermore, when the thermocouple 30 is used for the above function, it may be brought into direct contact with the object to be measured to measure the temperature of the object. Even in such cases, when processing the object to be measured, there is no need for the thermocouple to be in direct contact with the object during processing, so it is better to compare this method with the conventional temperature measurement method using only thermocouples. For example, measurement errors caused by the heat capacity of the thermocouple 30 can be reduced.

[Effects of the Invention] As explained above, according to the present invention, when processing an object to be measured, it is possible to measure the temperature without contact using a radiation thermometer, and moreover, when processing an object to be measured, temperature can be measured without contact. Regardless of the state, the temperature of this object can be measured relatively accurately.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram showing an embodiment of a temperature measuring device for carrying out the method of the present invention, and FIG. 2 is a characteristic diagram to be stored in the table memory in FIG. 1. 10... Object to be measured 20... Radiation thermometer 24... Temperature calculation circuit 30... Temperature measurement element (thermocouple) 32... Table memory.

Claims (1)

[Claims] (1) Using a radiation thermometer that measures temperature based on radiation from an object to be measured and a temperature measurement element that measures the temperature of the object to be measured or its surrounding temperature, multiple types of references with different radiation surface conditions are used. Collect temperature conversion data for the object in advance and create a table, and before measuring the temperature of the object, measure the temperature of the object or the surrounding temperature at a certain output value of the radiation thermometer. Detected by the element, based on this data read temperature conversion data specific to the object to be measured from the table, and when measuring the temperature of the object to be measured, correct the temperature from the output of the radiation thermometer and the temperature conversion data. A temperature measurement method using a radiation thermometer characterized by: