JPS5912633B2 - Diameter deviation detection method in Yusho pulling device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting diameter deviation in a crystal pulling apparatus.

Single crystals of metals or semiconductors have become essential to modern industry.

To obtain this single crystal, it is common to use a so-called melt-pulling device that gradually increases the length of the material by melting it at a high temperature to produce a longer single crystal. In this device, the dimensions (diameter or cross-sectional area) of the single crystal obtained are determined by the pulling speed of the material and the temperature of the melting part, but these determining conditions are quite delicate, and the crystal is As the volume of the melt increases, the volumetric mass remaining in the melt decreases, resulting in a change in heat capacity, making it difficult to ensure uniformity in drawing dimensions.

For this purpose, the heating power (current) or the temperature of the melt is detected for these devices, this is fed back, and the device is controlled by a program (10). Furthermore, in order to further improve accuracy, we detect and feed back the crystals that are being pulled recently, their weight, and the pulling dimensions.
A control method that makes the weight per unit, that is, the cross-sectional area constant, has come to be adopted.

15 Therefore, the present invention uses a crystal pulling device to detect the dimensions (length) of the pulled portion using a deflection measuring device and the pulled weight using a weighing scale, and to calculate a unit based on both of them. A crystal with a constant cross section is obtained by controlling the heating current (or other parameters) by feeding back the deviation between the instantaneous actual value of weight per length and its target value set in advance. .

However, in the case of a lever, the lifted weight is the electrical output of the weight scale, and the lifted dimension is the electrical output of the displacement meter, which are respectively extracted as voltage (or current) and used as input. An electronic calculation circuit extracts the deviation from the target value as an electrical quantity.

In this way, both the weight and the pull-up dimension are taken out individually as a minute voltage30, so if you are not careful when handling it,
There is a drawback that errors such as drift or sensitivity are likely to occur. The present invention solves the above-mentioned drawbacks and in order to allow the detected electrical quantity to be obtained as an already calculated result,
For the bridge circuit of the 35 weight detector based on the strain gauge bridge circuit, a potentiometer having the same configuration as the resistance balance adjustment circuit and whose sliding piece moves in proportion to the pulling dimension; By connecting a constant setting resistor value and making the bridge circuit output due to an increase in lifting weight and the bridge circuit output given by the potentiometer due to an increase in lifting size have opposite polarities, the lifting weight can be increased. The purpose is to propose a method for detecting diameter deviation in a crystal pulling device that detects whether or not a crystal can be pulled with a constant cross-sectional area by finding the deviation from the equivalent weight converted from the pulling dimension. That is.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the diameter deviation detection method in the crystal pulling apparatus of the present invention will be described with reference to the drawings.

As shown in the figure, the input/output terminal 5 of the load detector is a strain gauge bridge circuit composed of resistors 1, 2, 3, and 4.
, 6, 7, and 8, the terminal 9,
If a power source for the bridge circuit is applied from 10, the output between terminals 6 and 8 of the bridge circuit can be taken out from terminals 11 and 12, so the output voltage is proportional to the load detected by the load detector. If this strain gauge is installed to detect the weight of the crystal being pulled, the voltage between the terminals 11 and 12 will be proportional to the weight of the crystal being pulled.

Further, the adjustment circuit including the variable resistor 13 and the fixed resistors 14 and 15 is a well-known balance circuit of a strain gauge bridge circuit, and at the time of starting the measurement of the lifted weight, the terminal 11,
Adjust the output voltage of 12 to zero.

16 is a pulling dimension detector attached to the pulling section of the crystal pulling device.

That is, this pulling dimension detector 16 is mechanically installed so that the sliding piece moves in proportion to the pulling dimension of the crystal to be pulled. As the crystal is pulled up, it therefore imparts an unbalance to the bridge circuit that is proportional to its length. 1
7 is a setting device for the proportionality constant.

Further, 15 is a fixed resistor that sets the rotation angle of the variable resistor 13 (adjustment circuit) and the influence (sensitivity) on the bridge circuit given by the rotation of the variable resistor 16 (or the movement dimension of the sliding piece). be.

When the fixed resistor 14 is much smaller than the variable resistor and the fixed resistor 15 is present, the value changed by the variable resistor 16 via the variable resistor 17 (that is, the range of unbalance given to the bridge) is If the case where the fixed resistor 15 is not present is set to 1, then the ratio decreases to the ratio divided by the fixed resistors 15 and 14.

That is, the fixed resistor 15 is configured to reduce the maximum width of bridge circuit unbalance that can be caused by the fixed resistor 16. Furthermore, by reducing the number of setting devices 17, the variable width (maximum width of unbalance) by the variable resistor 16 can be increased.

Furthermore, if the fixed resistor 15 is fixed at a certain value, the amount of unbalance given to the bridge circuit by the movement of the sliding piece of the variable resistor 16 can be adjusted and set by the variable resistor 17. Since the bridge circuit described above is a load detector using a strain gauge, the unbalance (or output voltage) at which a bridge occurs due to the lifting weight is determined in advance.

When the sliding piece of the variable resistor (detector) 16 moves according to the pull-up dimension, an unbalance as an equivalent weight determined by the setting device 17 (and the fixed resistor) is given to the bridge, and the output voltage is It can be taken out. That is, the variable resistor 13 represents an adjustment circuit that adjusts the output to zero at the initial stage of measurement. Now, the polarity of the movement of the sliding piece of the variable resistor (detector) 16 is such that the electric output of the equivalent weight decreases as the lifted size increases, and as the pulled weight increases, the output voltage of the bridge circuit decreases. When the polarity increases, and when the weight increase and the pulling dimension increase are equal to the set value of the setting device 17, that is, the proportional constant of the pulling dimension to the equivalent weight, the bridge circuit while pulling the crystal The weight detected by the bridge is equal to and opposite in polarity to the equivalent weight of the unbalanced portion given to the bridge by the lifted dimension (detector 16).

That is, the bridge output is zero. Thus, when the output voltage of the bridge circuit is always zero, it is equal to the weight increase of the crystal being pulled, that is, the weight increase calculated from the predetermined increase in the pulling dimension.
Therefore, if the specific gravity of the crystal is constant, the cross section of the crystal will be pulled as constant. Therefore, for example, when the output voltage of the bridge circuit is no longer zero, it indicates that the crystal weight increase is different from the value predetermined by the setting device 17, and therefore, if the output is positive, the weight increase Excessive output indicates that the cross-sectional area is becoming large, and negative output indicates that the cross-sectional area is small.

In this way, by feeding back the output voltage of this bridge circuit to the crystal melting current, the bridge circuit output is always zero, that is, the ratio of the pulling dimension to the weight (cross-sectional area) set by the setting device 17 is kept constant. can be raised to

As is clear from the above explanation, the detection method of the present invention allows one circuit to perform both the lifted weight and lifted dimension without extracting and subtracting each as a voltage. The difference itself is extracted as an output, and since it consists of only passive elements (variable resistors, strain gauges, etc.), it is extremely stable and easy to handle.It is also much easier to detect and has higher detection accuracy than conventional detection methods. It has many effects such as improving

[Brief explanation of drawings]

The drawing is a schematic electrical wiring diagram applied to the diameter deviation detection method of the present invention. 1, 2, 3, 4... Resistance, 5, 6, 7, 8...
...Input/output terminals, 9, 10, 11, 12...
・Terminals, 13, 14...Zero point adjustment circuit, 15
...Fixed resistor, 16...Detector, 17
・・・・・・Setting device.

Claims (1)

[Claims] 1 For the bridge circuit of the weight detector using the strain gauge bridge circuit, a potentiometer whose sliding piece moves in proportion to the pulling dimension and a resistor for setting a proportionality constant have the same configuration as the resistance balance adjustment circuit. By connecting the bridge circuit output due to the increased lifting weight and the bridge circuit output given by the potentiometer due to the increased lifting size, the polarity is opposite to each other.
A crystal pulling device characterized in that whether or not the crystal is being pulled with a constant cross-sectional area is detected by finding the deviation between the increase in the pulled weight and the equivalent weight converted from the pulled dimensions. Diameter deviation detection method in the above device.