JPS6283627A - Digital temperature detector - Google Patents

Abstract

PURPOSE:To enable high accuracy measurement, by comparing output of temperature detector with that of reference voltage generator and measuring temperature of a specimen. CONSTITUTION:Temperature of a specimen 1 is measured actually by a tempera ture detector 2 and an output of the detector 2 is added to a comparator 3. A reference voltage generator 4 adds a voltage proportional to the target temper ature after generation thereof to the comparator 3 and it is composed of a D/A convertor. The generator 4 generates an output of the opposed polarity to an output voltage of the detector the voltage of which being proportional to the target temperature controlled by a digital control C from the outside. The comparator 3 stays immune from significant error of amplification, because of its output voltage being zero-V for equal absolute value of the output voltages of detector 2 and generator 4. Upon causing a difference between both output voltages, the comparator issues a voltage and its output voltage is given to an A/D converter 6 after DC amplification 5. When this convertor 6 is used with 10 bits, measurements become available at an accuracy of 0.02 deg.C. Further, when the comparator 3 produces an output, the output of the compara tor 3 can be made zero by a signal C.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a digital warm detection device, and more specifically, a temperature range of about ±0. This invention relates to a digital temperature detection device that performs high-precision measurements below IC and is used to control the temperature of high-temperature furnaces such as diffusion furnaces.

Conventional technology wafers are heat treated in high temperature furnaces such as diffusion furnaces;
In order to manufacture high-quality semiconductor devices, the temperature inside the furnace is required to always be at the target temperature.

Therefore, the temperature inside the furnace must be controlled, but in order to do so, it is necessary to measure the temperature inside the furnace with high precision.

Conventionally, a platinum-rhodium sensor (temperature detector) is used for this temperature measurement;
As shown in Figure 2, this output voltage is amplified several hundred times with a DC amplifier and then applied to an analog-to-digital conversion circuit (A/D converter). The output of the /D converter is input to a central processing unit (CPU) for processing.

Problems to be Solved by KA68 In the conventional temperature detection method, a highly accurate DC amplifier and A/D converter are required in order to perform highly accurate measurements.

However, A/D converters cannot provide higher precision than digital-to-analog conversion circuits (D/A converters). The measurement limit is approximately 0.085r.

Also, in order to ensure this temperature limit (1,085c).

The amplification degree of the DC amplifier requires an accuracy of 0.006 inches or less, but even with this method, it is not possible to stably obtain the above accuracy.

In this way, in the conventional measurement force ° method, oO ~ 1400C
High precision measurement of 0.02 to 0.03 C or less in the temperature range of 0.02 to 0.03 C was not possible.

In view of the above circumstances, the purpose of Kinoto 1-c is to provide a digital temperature detector capable of highly accurate measurement.

Means for Solving the Problems In the present invention, the outputs of a temperature detector that outputs an output proportional to the temperature of the object to be measured and a reference voltage generator are input to a comparator, and the output of the comparator is converted into A, This is a digital temperature measuring instrument characterized by inputting data to a /D converter.

Setting the output of the working reference voltage generator and inputting this output to the comparator, as well as inputting the output of the temperature detector to the comparator, the comparator will output if there is a difference between the two outputs, and A However, when there is no difference between the two outputs, that is, when the temperature of the object to be measured matches the target temperature, the comparator does not output, and therefore the output of the A/D converter is It becomes zero.

Further, if a difference occurs between the two outputs, the output of the reference voltage generator is controlled until the output of the comparator disappears, and the temperature of the object to be measured can be determined.

Example An embodiment of the present invention will be described with reference to the accompanying drawings.

In the figure, reference numeral 1 denotes an object to be measured such as a diffusion furnace, and the temperature of this object to be measured 1 is actually measured by a temperature detector 2. This temperature detector 2 is constituted by, for example, a platinum-rhodium sensor, and its output is applied to a comparator 3.

The reference voltage generator 4 generates a voltage proportional to the target temperature and applies it to the comparator 3, and is constituted by a D/A converter. A 16-bit D/A converter is used for this D/A converter, and the measurement range from 00 to 1400C is approximately 0.
Measured with a resolution of 0.02r.

An output proportional to the target temperature is generated by the external digital control signal C of the D/A converter u.
This output voltage has the opposite polarity to the output voltage of the temperature detector 2.

The comparator 3 is connected to the A/D converter 6 via the DC amplifier 5.
The A/D converter 6 is further connected to the CPU 7.

When the absolute values of the output voltages of the temperature detector 2 and the reference voltage generator are equal, that is, when the temperature of the object to be measured and the target temperature match, the comparator 3 outputs a voltage of O volts. Even if it is amplified by a DC amplifier, it is 0 volts, so even if the error in the amplification degree is as large as 1 to 2 inches, it has no effect on the measurement accuracy.

When a difference occurs between the two output voltages, that is, when the temperature of the object to be measured and the target temperature do not match, the comparator outputs a voltage 1, and the output voltage is amplified by a DC amplifier 5, and then Enters A/D converter 6. For example, it is sufficient to measure the temperature range of ±IOC of this A/D converter 6id and mll constant temperature, so if a 10-bit one is used,
Can measure with high accuracy of 0.02C. The CPU 7 calculates and processes the output of the A/D converter 6 and the control signal C of the D/A converter, produces a temperature measurement result, and performs necessary control.

In addition, when there is an output from the comparator 3, that is, when the temperature of the object to be measured and the target temperature do not match, the output of the reference voltage generator 4 is controlled by the digital control signal C to change the output of the comparator 3. By setting the voltage to O volts, the temperature of the object to be measured can be accurately determined. That is, when the zero halt is reached, the absolute values of the output of the reference voltage generator 4 and the output of the temperature detector are equal, so the temperature corresponding to the output of the reference voltage generator 4 is equal to the temperature of the object to be measured. They are equal.

Other Embodiments The present invention is not limited to the above embodiments, but may be implemented as follows.

(D reference voltage generator does not need to use a D/A converter, and any stable DC voltage generation source may be used.

(2) If a chopper amplifier is used as the DC amplifier, measurement accuracy can be improved.

(3) A differential amplifier may be used as a comparator by making the polarity of the output positive pressure of the temperature detector and the reference pressure generator the same.

(4) Current may be used as the output of the temperature detector. In this case, the output of the reference voltage generator is also a current, but when the current is output in this way, there is no influence of resistance compared to voltage, so measurements can be carried out with greater coverage.

Effect of Term 11C As described above, the temperature of the object to be measured is measured by comparing the outputs of the temperature detector and the reference voltage generator, so that highly accurate measurement can be performed.

That is, when the output of the comparator is 0 holt, the target temperature and the temperature of the object to be measured match, so the temperature of the object to be measured can be measured with high precision according to the output of the reference voltage generator at this time. be able to.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the tree climbing 8A, and FIG. 2 is a block diagram showing a conventional example. 2... Temperature detector 3... Comparator

Claims (1)

[Claims] 1. The outputs of a temperature detector that outputs an output proportional to the temperature of the object to be measured and a reference voltage generator are input to a comparator, and the output of the comparator is input to an A/D converter. A digital temperature measuring device that allows input. 2. The digital temperature detection device according to claim 1, wherein the reference voltage generator is a D/A converter. 3. The digital temperature detection device according to claim 1, wherein the reference voltage generator outputs a current. 4. The digital temperature detection device according to claim 1, wherein the temperature detector outputs a current. 5. A digital temperature detection device characterized in that the outputs of the temperature detector and the reference voltage generator have opposite polarities. 6. A digital temperature detection device characterized in that the outputs of the temperature detector and the reference voltage generator have the same polarity. 7. A digital temperature detection device characterized in that the comparator is connected to an A/D converter via a DC amplifier.