JPS6298722A - Temperature controlling device for optical heating device - Google Patents

Abstract

PURPOSE:To enable the titled device to perform the temperature control accurately as expected by a method wherein an opened loop control is performed up to a specified temperature, and then a closed loop control is performed in accordance with the target pattern. CONSTITUTION:A radiation thermometer 9 receives the radiant light of a semiconductor wafer 4, and it outputs a signal corresponding to the temperature of the wafer. A lamp output controlling device is controlled in such a manner that a lamp group sends out a specified output or an output corresponding to a preset pattern. After the output of the radiation thermometer has reached a specified value, the lamp output controlling device is controlled so that the lamp output is coincided with a target pattern.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to activation of ion implantation layers in semiconductor wafer processes, phosphosilicate glass glue flow, annealing of metals, and formation of ohmic contacts between Si and metals. The present invention relates to a temperature control device for a light heating device used in, for example.

[Conventional technology]

Conventional optical heating devices, such as lamp annealing devices,
As shown in the figure, facing the flat reflecting plate 1, a rod-shaped tungsten haloken lamp (hereinafter abbreviated as a rung) 2,
2... are arranged in parallel (the surface of the reflector 1 may be curved with respect to each lamp 2 in order to enhance the reflection effect), and the combination of the reflector 1 and the lamp 2 are installed spaced apart in the vertical or horizontal direction, and a process tube 3 made of quartz glass is placed between them.

The ion-implanted semiconductor wafer 4 is placed on a quartz susceptor 5 housed in the process tube 3, and in this state is heated by irradiating it with the lamp 2. On the other hand, a processing gas is introduced and exhausted into the processing space formed by the process tube 3 and the lid 6, and the wafer 4 is processed.

Figure 9 is an example of the target pattern of wafer temperature in wafer heat treatment, and the wafer temperature is about 8
It reaches a constant temperature range of about 1000° C. in seconds, and gradually cools down after about 30 seconds. This pattern is obtained by controlling the lamp power.

Incidentally, there are two types of lamp output control methods: an open-loop control method and a closed-loop control method, and each method is implemented as follows.

(1) Open-loop control method A control method that is carried out according to the rung output cover turf determined experimentally. For example, as shown in Figure 10, the lamp output is initially high, and after a certain period of time, it becomes smaller and gradually decreases. control to do so.

(2) Closed-loop control method A temperature sensor such as a thermocouple is brought into contact with the wafer, and the lamp output is controlled to match the target pattern while measuring the temperature of the wafer.

[Problem that the invention seeks to solve]

In conventional temperature control devices for optical heating devices, lamp output was controlled according to one of the two methods described above.
Those methods include the following problems. In other words, (1) Problems with open-loop control method The wafer temperature is determined by the energy given by the lamp, but a) If the initial temperature and absorption rate of the wafer are different, the temperature will rise even if the same energy is given. Differently, the time required for the heated object to reach the desired temperature varies. That is, since the state of the controlled object changes from moment to moment, it is impossible to achieve a pattern with good reproducibility.

'F3) If the initial temperature of the process tube or processing gas is different, the state of temperature rise will be different even if the same energy is applied.

For these reasons, the target pattern shown in FIG. 9 could not be obtained.

(2) When measuring the temperature of an object using a thermocouple in a closed-loop control method using a thermocouple, it is assumed that the thermocouple and the object have reached thermal equilibrium. The thermocouple does not accurately indicate the wafer temperature because the temperature rise occurs in a short period of time, and the temperature of the wafer and thermocouple increases before the thermocouple, wafer, and thermocouple reach thermal equilibrium.

Therefore, even if you control the lamp output based on the thermocouple output and obtain a thermocouple output that matches the target pattern, this only means that you are controlling the thermocouple temperature, and the actual wafer temperature pattern is different from the target pattern. It will not match the pattern.

Therefore, in order to avoid the above-mentioned problems in open-loop and closed-loop control methods, we will use a radiation thermometer that does not require time for thermal equilibrium, and control the lamp output according to the target pattern while measuring the wafer temperature. If so, the following problems will occur.

Problem When measuring the temperature of an object with a radiation thermometer, there is no problem if the object to be measured is opaque at a temperature in the wavelength range of 6D, and there is no thermal radiation source around the object, but there is no problem with the measurement of the temperature of an optical heating device. Sl, which is one of the processing targets, is in the infrared region (up to about 500°C)
Since the process tube itself is a translucent object and its temperature increases, thermal radiation from the process tube passes through the object to be measured (Sl) and enters the radiation thermometer. As a result, the radiation thermometer does not accurately indicate the temperature of the object to be measured.

Furthermore, the measurement range of radiation thermometers is generally limited, making it difficult to measure over the entire temperature rise process of the object to be measured.

In view of the above circumstances, the present invention uses a radiation thermometer only in a specific temperature measurement range to accurately measure the temperature of sea urchins, and combines the open-loop control method and closed-loop control method described above. An object of the present invention is to provide a temperature control device for a light heating device that controls the output of a lamp so as to obtain a temperature change close to a target pattern.

[Means and effects for solving the problems] The present invention has the following features:
In order to solve the above problems, we created a group of rungs that heat the object to be heated, a lamp output control device that controls the lamp output, a radiation thermometer that measures the temperature of the object to be heated, and a rung output control that receives the output of the radiation thermometer. In the temperature control device of the optical heating device, which is composed of an arithmetic unit that sends signals to the device, a constant lamp output determined in relation to the target constant temperature range temperature is performed at the start of heating, and a predetermined temperature (closed loop Either maintain the lamp output in the target constant temperature range at the control start temperature, or fully control the rung output according to a predetermined pattern, and after the closed loop control start temperature is reached, the lamp output is adjusted to match the target pattern. By controlling , heating according to the target pattern can be achieved after the difference in initial conditions is resolved and the radiation thermometer can accurately measure the temperature of the object to be heated.

〔Example〕

FIG. 1 is a longitudinal sectional side view showing how the radiation thermometer 9 is installed. The optical heating device is similar to the conventional device described with reference to FIG. A susceptor 5 on which a wafer is placed is housed therein.

In order to measure the temperature of the wafer 4, a hollow tube 7 is welded to the side opening of the process tube 3, and the other end is connected to a radiation thermometer 9 via a fitting 8.
Passing the hollow tube 7 through the opening of the process tube 3,
It is adapted to receive radiation light from the semiconductor wafer 4.

FIG. 3 is a block diagram of a temperature control device that controls the temperature of the semiconductor wafer 4. As shown in FIG. The temperature control device is composed of a radiation thermometer, a calculation device, a lamp output control device, and a rung group, and the functions of each block are as follows.

(1) Radiation thermometer... Receives radiation from the semiconductor wafer 4 and outputs a signal corresponding to the wafer temperature.

(2) Arithmetic device... The lamp output control device is controlled so that the lamp group emits a constant output or an output according to a predetermined pattern until the output of the radiation thermometer 9 reaches a constant value.

After the output of the radiation thermometer reaches a certain value, the lamp output control device is controlled to match the target pattern.

(3) Lamp output control device... Controls the output of the lamp group according to instructions from the calculation device.
Specifically, the lamp current is controlled using a thyristor or triac.

FIG. 4 shows a circuit configuration of an arithmetic unit for realizing the functions described in item (2) above, and the configuration and operation of the main functional parts will be explained below.

(1) Processing selection switch... The heat treatment pattern shown in Figure 2 is the memo IJ (R
A plurality of heat treatment patterns are prepared in the OM), and the heat treatment pattern is selected by this switch. The temperature pattern shown in FIG. 2 is a pattern in which the constant temperature range temperature T2 is reached approximately t5 seconds after the closed loop start temperature T1, and the temperature gradually decreases after t2 seconds.

(2) Memory (ROM): Data related to heat treatment patterns are stored.The lower 12 bits of the address bus are counters, p1 and upper 4 B.
It is accessed by the encoder. Therefore, 16 types of patterns can be stored.

Note that data related to the lamp output output at the start of processing is stored at addresses xxxx, ya, ya, ke, and φΦΦΦB.

(3) Encoder... 4 Bi for on/off status of 16 processing selection switches
Convert to t data. The output is connected to the upper 4 bits of the memory IJ (ROM).

(4) Counter: Receives a clock signal from a clock generator via a gate and counts up. It is a 12-bit counter, and its output is connected to the lower 12 bits of the address bus of the memory (ROM). Note that it is cleared by a signal issued by the timing control circuit when the start switch is pressed.

(5) The output signal of the comparator radiation thermometer is input through the amplifier, and the signal sent from analog switch 1 (referred to as the reference signal)
Compare with.

If the signal from the radiation thermometer is smaller than the reference signal, a signal of logic level B is sent to the timing control circuit, and if it is larger than the reference signal, a signal of logic level H is sent to the timing control circuit.

(6) Analog switch: The voltage of the input/switch meter connected to the input is set to a voltage corresponding to the close/loose control start temperature determined for each of the 16 types of heat treatment patterns. Then, one voltage is selected from 16 types according to the 4-bit data of the encoder and the voltage is sent to the comparator.

(7) Calculator from P... Calculate from P the difference between the output voltage of the D/A converter and the output voltage of the radiation thermometer corresponding to the target temperature pattern, and apply it to the lamp output control device. analog switch 2
Output via .

(8) Analog switch 2... According to the instructions from the timing control circuit, the output of the D/A converter (via the amplifier 2) and the output of the arithmetic unit or the ground level (N'V) are fully output from the HAP.

(9) Ambut... Amplifies the output of the radiation thermometer and sends it to the computing unit from P via the comparator and subtractor.

00 7amp 2... Amplifies the output of the D/A converter and converts it to analog switch 2.
send to

Next, the arithmetic unit will be explained according to the order of its operation.

(1) When the start switch is pressed, the timing control circuit clears the counter and sends a signal to the analog switch 2 to pass the output of the D/A converter (via the amplifier 2).

Since the memory no.XXXX+YayaYakiYABlueYYYYYYYYYYYYYYY φ~B address is accessed, the voltage corresponding to the address data is output from the analog switch 2 (referred to as initial output).

(2) The wafer is heated by the initial output, and the temperature gradually rises. Since the address XXXX of the analog switch 1 is accessed, a voltage (VR) adjusted by the corresponding potentiometer is applied to the comparator.

As the wafer temperature rises, the output voltage of the radiation thermometer (To
> also increases, but the comparator compares this voltage VO and VR. Then, when Vo<Vn, a signal of logic level L is sent to the timing control circuit, and when Vo≧vR, a signal of logic level H is sent to the timing control circuit.

(3) When the timing control circuit receives a logic level H signal from the comparator, it sends a logic level signal to the gate and a signal to the analog switch 2 to allow the output of the arithmetic unit to pass through P.

(4) As a result, the gate passes the clock generator signal and the counter is counted up.

Therefore, the memory is sequentially accessed from addresses XXX, Y, Φ☆φ, and φ, and a target pattern is generated.

(5) This target pattern signal is D/A converted and subtracted from the signal vo described above (referred to as a deviation signal).

A calculation is performed on this deviation signal by P, and the calculation result is provided to the lamp output control device via the analog switch 2.

(6) The output voltage of the one-way/A converter is sent to the timing control circuit. The timing control circuit determines that processing is complete when the ~V times signal continues for a certain period of time or more, and sends a signal to the analog switch 2 to pass the 4V signal.

Next, FIG. 5 is a block diagram of a second embodiment of the arithmetic unit. This arithmetic unit is composed of an amplifier, an A/D converter, an input device, a microcomputer, a D/A converter, and a display device, and the functions of each block are as follows.

1) Microcomputer φ・φ The functions shown in Figure 4 are input by a program, and the ROM
stored in the area.

2) A/D converter converts the output of the 11° radiation thermometer (via amplifier) into A/D and sends it to the microcomputer.

3) D/A converter: D/A converts the output of the microcomputer and sends it to the lamp output control device.

4) Input device: A device for setting target patterns, control parameters, etc.

5) Display device: Displays data when inputting data from an input device and displays the internal status of the microcomputer.

FIG. 6 is a flowchart illustrating the operation of the microcomputer shown in FIG. 5, and the operation is the same as that in FIG. 4.

That is, first, the target pattern and control parameters are set from the control logic, and the start switch is pressed.

Then, the microcomputer commands to generate an initial output, and open loop control is performed by outputting the initial output until the output of the radiation thermometer reaches a certain temperature. When a certain temperature is reached, calculation is performed using P so as to match the target pattern, the calculation result is output to the D/A converter, and closed loop control is performed. At this time, the target pattern is stored in a memory such as ROM or RAM of the microcomputer. When the process is completed, the process returns to the state before the start.

FIG. 6(1)) shows the method of MD calculation. Here Trt
is the temperature data at time t on the target pattern, Tit
is the output of the radiation thermometer at time t. et, et
, et, Mt, etc. are defined by the calculation formulas shown in the figure.

FIG. 7 is a modified embodiment of the portions j and ° in FIG. 6.

(a) is a period of time until reaching a certain temperature, for example, at time t,
From the initial output to output P at time t2, to output P2 at time t2...
A method of controlling the output in a predetermined pattern, such as (b), a method of starting closed-loop control not at the constant temperature described above, but when the temperature of the radiation thermometer starts to rise. , (,) indicates the start of closed-loop control when the temperature of the radiation thermometer increases by a certain temperature range or more after the temperature starts to rise, for example, when the temperature Tit changes from the rising start temperature Tlto to the temperature Tc.
The method is shown below, which is carried out when the temperature reaches Tito+Te or higher.

Among these methods, in the case of (b) and (e), the basics of the target temperature pattern are given in Fig. 9, but the starting temperature of the closed loop control is, for example, TI, and in this case, tx/sec after the initial output If it has elapsed, rewrite tj seconds as 1.
The temperature pattern in the temperature range of 71 or higher is used as the target pattern.

〔Effect of the invention〕

The present invention performs open-loop control up to a certain temperature, and thereafter performs closed-loop control according to a target pattern. ■ Closed-loop control is achieved by using a radiation thermometer for control from a certain temperature or higher where the object to be heated becomes an opaque object. Therefore, the desired and correct temperature control can be performed.

■ Temperature Tt due to differences in initial conditions (see Figure 2)
Since the time required for the temperature to rise to
, -100°C to -200°C, below which there is no effect).

■ The coefficient from P is adjusted for the range above the constant temperature T (Figure 2). That is, since the adjustment is made within a range where the influence of the initial state is removed, reproducibility between the adjustment stage and the actual processing stage is good.

It has the following effects.

In addition, in the case where the process tube transitions to a closed loop using methods (D) and (C) above, if the process tube reaches thermal equilibrium and the initial temperature of the heated object is constant and the process is performed at regular intervals, the closed loop will be established. Since the transition temperature converges to a constant value, the same result as in (a) above is obtained.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional side view of a light heating device showing the installation situation of a radiation thermometer for carrying out the present invention. FIG. 2 is a diagram showing an example of a target pattern. FIG. 3 is a block diagram of the temperature control device. FIG. 4 is a block diagram showing a first embodiment of the arithmetic device. FIG. 5 is a block diagram showing a second embodiment of the arithmetic unit (microcomputerized). FIG. 6 is a flowchart of processing in the microcomputer. FIG. 7 is a flowchart showing a modified embodiment. FIG. 8 is a longitudinal sectional side view showing a conventional optical heating device. 9th
The figure is a diagram showing an example of a target pattern. FIG. 10 is a diagram showing an example of a conventional open loop output signal. 1...Reflector plate 2...Halogen lamp 3...
・Process tube

Claims (5)

[Claims] (1) A group of lamps that heat the heated object, a lamp output control device that controls the lamp output, a radiation thermometer that measures the temperature of the heated object, and a signal that receives the output of the radiation thermometer and sends a signal to the lamp output control device. consisting of an arithmetic unit, which performs a constant lamp output determined in relation to the temperature of the target constant temperature range at the time of heating start, and maintains the constant lamp output until a predetermined closed-loop control start temperature is reached; Alternatively, temperature control of a light heating device is characterized in that the lamp output is controlled according to a predetermined pattern (open-loop control), and thereafter the lamp output is controlled to match a target pattern (closed-loop control). Device. (2) The temperature control device for a light heating device according to claim 1, wherein the closed loop control start temperature is a temperature at which the output of the radiation thermometer reaches a certain value. (3) The temperature control device for a light heating device according to claim 1, wherein the closed-loop control start temperature is a temperature at which the output of the radiation thermometer starts to rise or a temperature that has risen by a certain temperature range or more after the output of the radiation thermometer starts to rise. . (4) The temperature control device for an optical heating device according to claim 1, wherein the target pattern is defined only in a range above a temperature determined in relation to the temperature of the target constant temperature range. (5) The optical heating device according to claim 1, wherein the target pattern is a pattern in a temperature range higher than the closed loop start temperature, which is extracted in advance from a predetermined pattern starting from 0° C. or an appropriate temperature. Temperature control device.