JPS60200888A - Method for controlling diameter of melted zone in preparation of crystal by heating with infrared ray - Google Patents

Abstract

PURPOSE:To maintain melting condition appropriately always and to grow a crystal by heating with infrared rays by measuring the diameter of a melted zone successively, by binarizing the measured values and allowing the values to be stored successively and then operating to control the quantity of electricity to be fed to an infrared ray lamp. CONSTITUTION:A line sensor 22 scans a melted zone 8 in response to clocks from a clock circuit 21 in a stage of crystal growth and outputs a signal corresponding to the dimension of the diameter of the melted zone. The output is amplified by an amplifier 23 and binarized by comparing with a referential voltage by a comparing means 24. The binarized signal is outputted to a controlling means 25. A timing pulse generator 18a generates a pulse signal for each one revolution of the melted zone 8, and the controlling means 25 stores successively the binarized measured signal. The controlling means 25 adopts the dimension of the diameter at the position of the angle of revolution corresponding to the largest rate of change, and operates basing on the measured data measured at preceding m times with the present data. The amt. of electric power to be fed to the infrared ray lamp is controlled through an electric power controller 28 basing on the result of the operation.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to the production of infrared heated crystals by arranging an infrared lamp at one focal point of a spheroidal mirror and arranging a material rod and a molten zone of a seed crystal at the other focal point. Concerning technology for controlling the diameter of the molten zone.

DESCRIPTION OF THE PRIOR ART FIG. 1 is a schematic front sectional view showing an example of a conventional single crystal manufacturing apparatus. Referring to Figure 1,
This device has the form of a dual circular heating furnace 3 in which two semicircular spheroidal mirrors 1 and 2 are slid together and connected.

At one focal point Fa, Fb of each spheroidal mirror 1°2 is a halogen lamp 4, which is an example of an infrared lamp serving as a heat source.
5 is placed. Also, the other focal point F2. of the spheroidal mirror 1.2 which is close to each other. A molten zone 8 formed between a raw material rod 6 and a seed crystal 7 that rotate in the same or opposite directions is disposed at F2.

In this device, light radiated from a halogen lamp 4.5 is focused on a melting zone 8 by a spheroidal mirror 1.2, thereby heating and melting the raw material rod 6 and causing crystal growth. In addition to the bielliptical heating furnace 3 shown in Fig. 1, small elliptical heating furnaces using a single spheroidal mirror are also widely used. The heating crystal manufacturing equipment has excellent advantages such as being able to obtain stable output, not causing any deviation in composition in the growth direction, and being able to observe the state of crystal growth.

However, in order to sustain crystal growth using the apparatus shown in FIG. 1, the molten zone 8 must be shaped like an hourglass, approximately close to the intracranial ω1E platform, as shown in a partial front view in FIG. It is important to maintain the shape. Therefore, conventionally,
While observing the melted zone 8 with the naked eye, the operator manually controlled the downward supply speed of the material rod 6 and the power of the halogen lamp 4.5. That is, when the shape of the molten zone 8 becomes unfavorable to crystal growth, the supply speed of the raw material rod 6 is increased or decreased, or the power supplied to the halogen lamp 4.5 is adjusted. Therefore, when producing a single crystal, an operator had to stay with the equipment for a long time to make adjustments.

Moreover, when the power supplied to the halogen lamp 4.5 is adjusted, the light m of the halogen lamp 4.5 itself (although it changes immediately, the melting state of the melting zone 8 is
It does not quickly follow changes in the amount of light, and changes occur in the melted zone 8 only after a considerable amount of time has passed. Therefore, the operator must change the power ρ supplied to the halogen lamp 4.5 while anticipating in advance the time delay in changing the melting state of the melting zone 8. Therefore, if excessive power is supplied, the melting zone 8 will become unnecessarily enlarged, resulting in the complication of making excessive adjustments. However, there is a problem in that complicated adjustment operations are still required to achieve the optimum melting state.

OBJECT OF THE INVENTION Therefore, an object of the invention is to solve the above-mentioned problems y/i
! Provides a method for controlling the diameter of a molten zone for infrared heated crystal production, which eliminates the troublesome work of the operator, and allows the molten state of the molten zone to be kept at an appropriate level at all times. It's about doing.

Summary of the Invention The present invention focuses on the fact that changes in the melting condition of the melting zone appear as changes in the diameter of the melting zone, and by controlling the diameter of the melting zone, the optimum melting condition for crystal growth is achieved. This is what we aim to achieve. The present invention provides a line sensor for measuring the diameter of a molten zone, a binarizing means for converting the output of the line sensor into two values, and a line sensor for measuring the diameter of a molten zone.
timing pulse generating means for generating a timing pulse when a plurality of predetermined angular positions are reached for each rotation;
In response to the pulse signal from the timing pulse generation means, the measurement signals converted into 21 signals by the binarization means are sequentially stored, and the molten zone diameter dimension at the angular position where the rate of change is the largest for each rotation is measured. As data, m (m is an integer)
A control means that performs calculation processing according to a predetermined calculation formula based on the previous measurement data and the current measurement data, and controls the amount of electricity such as power and voltage supplied to the infrared lamp based on the calculation result. This is a method for controlling the diameter of the molten zone in the production of infrared heated crystals.

Other features of the invention will become clear from the following description of the embodiments.

DESCRIPTION OF THE EMBODIMENTS As described above, the present invention optimizes the melting condition of the molten zone for crystal growth by controlling the diameter of the molten zone. - That is, as shown in FIG. 2, when the molten zone 8 has an hourglass shape that is approximately similar to an intracranial truncated cone, crystal growth is maintained in an optimal state. However,
As the crystal growth progresses, the temperature of the melting zone 8 increases, and the power and voltage supplied to the halogen lamp become excessive, or the downward supply speed of the material rod 6 becomes slightly faster.
As shown by the broken line A, more crystalline crystals are melted than necessary and the span below the melt zone 8 increases. On the other hand, if the downward supply speed of the material rod 6 is slow, or if the supply type horn or voltage to the halogen lamp is small, the supply of material will be reduced and the melted zone 8 will be moved along the broken line B.
As shown in , the diameter is smaller than the optimum state. Therefore, if the diameter of the portion indicated by the dashed-dotted line C is maintained at the optimum diameter in the molten state in consideration of the above phenomenon, crystal growth can be stably maintained.

By the way, if the cross section of the melt zone 8 is a perfect circle, it is sufficient to measure the diameter of the melt zone 8 from one direction, but if the cross section of the melt zone 8 is a perfect circle, it is usually It changes into various shapes such as ellipses. Therefore, in order to accurately grasp the melting state of the melted zone 8, it is necessary to measure the diameter of the melted zone 8 from a plurality of directions. Therefore, in the present invention, the diameter of the molten zone 8 is measured at a plurality of angular positions, and the diameter at the angular position where the rate of change is the largest is used as measurement data to determine the power and voltage supplied to the halogen lamp. . By using the diameter dimension at the angular position where the rate of change was the largest as data, the molten zone 8
This is because it is possible to accurately and quickly follow changes in the diameter of.

As described above, this invention attempts to achieve an optimal melting situation by measuring the diameter of the melting zone 8 and changing the light intensity of the halogen lamp based on the measured change in diameter. .

FIG. 3 is a schematic perspective view showing a control device according to an embodiment of the present invention. The diameter of the melting zone 8 (the diameter of the portion indicated by the dashed line C in FIG. 2) is the diameter of the CO
It is measured by a line sensor camera 12 including a D line sensor. The line sensor/camera 12 has a bellows 13
A half-mirror box 14 is provided via. A portion of the light incident from the melting zone 8 is reflected by the half mirror 15 in the half mirror box 14.
It is guided to a line sensor inside the line sensor/camera main body part 12a. On the other hand, the half mirror box 14 is also provided with a screen 16 so that the state of the melted zone 8 can be observed with the naked eye.

The line sensor/camera 12 is connected to the control roller 17 and includes a binarization means for binarizing the output of the line sensor. A reference power controller (not shown) that sequentially stores and performs arithmetic processing according to the PIDi control formula described later to control the power supplied to the halogen lamp (not shown).
gives output to

A timing pulse generator 18 is also connected to the controller 17 . This timing pulse generator 18 is
A timing pulse is generated in accordance with the rotation of the seed crystal 7, that is, the rotation of the molten zone 8. Based on the timing pulse from the timing pulse generator 1B, the control means in the controller 17 is configured to store the measurement No. 18 from the line sensor.

FIG. 4 shows a schematic block diagram of an infrared heating single crystal manufacturing apparatus including the embodiment shown in FIG. In the block diagram of FIG. 4, a portion surrounded by a chain line E shows a circuit included in the line sensor camera and controller 17 shown in FIG.

That is, the line sensor camera 12 shown in FIG.
includes a clock circuit 21, an amplifier 23 for amplifying the output from the line sensor 22, and a comparison means 24 for binarizing the output from the amplifier 23, and the controller 17 includes the above-mentioned control means 25 and a timing pulse It includes a preset counter 26 connected to the generator 18. The control means 25 operates based on the clock from the clock circuit 21 according to a pre-installed program. The line sensor 22 scans the molten zone 8 in accordance with the clock from the clock circuit 21 and outputs a signal according to the span method. The output of the line sensor 22 is amplified by an amplifier 23 and compared with a reference voltage by a comparing means 24,
Binarized. This binarized signal is given to the control means 25, and is arithmetic-processed according to the PID calculation formula, which will be briefly described, to calculate a control output value, which is added to one reference power from the program generator 27 to power the halogen lamp. [Con] ~
Supply power is output via the roller 28.

In this embodiment, two timing pulse generators 18 are used.
One timing pulse generator 18a includes two timing pulse generators 188.18b, and one timing pulse generator 18a has one timing pulse generator 188.
Each time it rotates, one pulse signal (hereinafter referred to as the origin signal) is generated at a predetermined position, and when the control means 25 receives this origin signal, it stores the measurement data from the line sensor 22.

The timing pulse generator 181) used is one that sequentially generates pulses of, for example, 1201 [1il] when the melting zone 8 rotates once, and the timing pulse generator 181) sequentially generates pulses of, for example, 1201 [1il] when the melting zone portion 8 rotates once.
is reset by the origin signal from the timing pulse generator 18a, and is set to a predetermined value of 6 given by the control means 25.
1 preset the numerical value, and the timing pulse generator 18b
It sequentially counts the pulses given from , and when the count value reaches a preset predetermined value, it gives an output signal to the control means 25 . The preset predetermined value is not limited to one type, and a plurality of values can be set, thereby making it possible to measure the diameter of the molten zone 8 at various angular positions. In response to the pulse signals provided by the timing pulse generator 18b and the preset counter 26, the control means 25 stores measurement data from the line sensor. Therefore, an arbitrary value is set by the input means 29, and each time the preset counter 26 counts timing pulses of an arbitrary value, the diameter dimension of the molten zone portion 8 at an arbitrary rotation angle is used as measurement data and the control means 25 can be stored. The reason for measuring the diameter of the molten zone 8 at a point other than the origin in this way is that the cross section of the molten zone 8 is not necessarily a perfect circle as mentioned above, and depending on the material, it may be elliptical or long. This is because the diameter of the melted zone 8 often changes to various shapes such as circles, and if the diameter of the melted zone 8 is measured from multiple angular positions and the diameter at the angular position where the rate of change is the largest is adopted as the measurement data. This is because changes in (y) of the melted zone portion 8 can be followed accurately and quickly.

The input means 29 is constituted by, for example, a keyboard, and the control means 25 inputs the optimum reference diameter value for crystal growth, constants included in the PID calculation formula described later, etc.
It is for inputting.

As described above, in this embodiment, the power supplied to the halogen lamp is controlled by the P⊙D calculation formula. PI here
In the differential form expression, the D calculation formula is 8 YN = I] (
△ e N +Ie N + D △ 2 ei+)・
...(1), and in equation (1), t3iT:e N = S M (S
indicates the optimum diameter of the melted zone 8, and M indicates the average value of the measured diameters of the melted zone 8 over 11 times. ). In other words, equation (1) calculates VN to the control amount of power supplied to the halogen lamp based on the change from the optimum diameter S of the melting zone 8. In addition, in formula (1), P, I, D
are constants.

ΔON and Δ2(3u are the following equations (2) and (3)
It is something that can be deceived.

ΔeN=eIl−eo・(2) Δ2eN−ΔeN−Δeo・(3) In this invention, eN, ΔeN, and Δ2eN represent the melted zone 8
Among the diameters at a plurality of rotational angular positions, the value at the angular position where the rate of change is greatest is adopted as measurement data. Further, eN is calculated using the current measurement data M, and eo is calculated using the measurement data M m times ago. Therefore, the control output ΔYN is calculated based on the current measurement data and the measurement data m times ago. Using the data m times ago in this way means that even if the power supplied to the halogen lamp is changed, the molten zone 8
This is based on the knowledge that the effects of a change become apparent only after a considerable period of time has passed. That is, in this embodiment, the measurement data of the molten zone part 8 is adopted by averaging the values n times, and furthermore, by using the measurement data m times ago and the current measurement data of the averaged measurement diameter, This is intended to gently apply the control output ΔyN.

The value of the control output Δy is at most 5 W<5, and the time it takes for a change in the power control output to be reflected on the diameter of the melted zone 8 is about 5 minutes. Further, the total control output over the entire crystal growth ranges from -100W to -1-300W.

The control output Δy calculated as described above is output from the control means 25 in the block diagram of FIG. Power is supplied from the power controller 28 to the halogen lamp.

FIG. 5 is a diagram for explaining the overall operation of the apparatus including the embodiments shown in FIGS. 3 and 4. FIG.

Next, the operation including this embodiment will be explained with reference to FIGS. 3 to 5. The method of controlling the diameter of the melted zone of the present invention maintains the diameter of the melted zone portion 8 at an optimal value. Therefore, the process of first melting the raw material rod 6 on the seed crystal 7 (see FIG. 4) and forming the molten zone 8 is performed manually as in the conventional method. Next, the diameter of the formed molten zone 8 is maintained optimally by the control method of the present invention. First, the timing pulse generator 18a sends a rotation signal, that is, an origin signal to the control means 25 every time the melting zone 8 rotates once.
is giving to When this rotation signal is applied, the control means 25 takes in and stores the binarized measurement data of the molten zone portion 8 via the line sensor 22, the amplifier 23, and the comparison means 24. Next, when the rotation signal is output n times,
When the n pieces of measurement data are taken in by the control means 25, the control means 25 calculates the average value of the n pieces of measurement data and stores this as measurement data M. Next, the control means 25 calculates the difference e between the optimum diameter size S of the molten zone 8 set in advance by the input means 29 and the measured f-ta M, and e
Remember. Therefore, the measurement data M1. "M2...
・Sequentially, e I + e 2 ・・
・is memorized.

When the control means 25 is set to the control mode with the measurement data M and the change e in the diameter of the melted zone 8 stored in sequence as described above, the control means 25 changes the current change in the diameter of the melted zone 8. minute eN and the change in diameter e from m times ago.

The difference ΔeN is calculated, and ΔeN−Δeo is calculated to calculate Δ2oN. eN, which was captured in this way,
△eN and Δ2 eN and preset constant]
], 1, and D, the calculation ΔyN'=p(ΔeN+IeN+DΔ2 eN) is performed, and the control output ΔVN is obtained.

This control output ΔVy is given from the control means 25 to the halogen lamp power controller 28, and is added to the reference power YO from the program generator 27 to provide the halogen lamp supply power Y,'-Y. 10ΔVN is output.

After the control output Δy is output, the current data used for calculation (3N, ΔeN, Δ2ON and YN
is stored in the control means 25 as the previous data.

Next, if there is a change in the input constant, the constant is set by the input means and the calculation process is performed again, but if there is no change in the constant, the next calculation process is performed as is.

In this way, the power supplied to the halogen lamp is controlled according to the diameter of the melting zone 8. Therefore, there is no need for an operator to attend to the single crystal production apparatus and monitor the boiling process, and it becomes possible to automatically and unattendedly grow a single crystal.

In addition to the timing pulse generator 18a, in the block diagram shown in FIG. counter 2
6 is set number C.

The timing pulse generator 18b provides 120 pulse signals per revolution to the Bricella counter 26 as described above. The preset force/counter 26 inputs a pulse signal to the control means 25 using the input means 29.
When the count value reaches the preset value input in advance, an output signal is given to the control means 25. The preset counter 2G is reset by the above-mentioned origin signal. When the preset counter 26 counts the pulse signal by the preset value, the pulse from the timing pulse generator 18b (number i is the pulse signal from the control means 25).
This signal causes the control means 25 to:
The comparison means 24 takes in the binarized signal. Therefore, by setting a plurality of preset values in the preset counter 2G, it is possible to store measurement data of the diameter 3'' method of the molten zone 8 in the control means 25 at a plurality of locations other than the origin for each rotation.

By the way, although it is not clear from the flow diagram shown in Figure 5,
The data taken in by the control means 25 at an angular position other than the origin in response to the pulse signal from the timing pulse generator 18b is independent of the data when the origin signal is given.
The values of n times are averaged and stored in the control means 25 as e'', e''. The control means 25 controls each of e , e l , e I at the origin position or other set angular position.
+..., of which the change is Δe1Δe
' and 80 JL is adopted as the measurement diameter, and the calculation of equation (1) is performed. By measuring the diameter of the molten zone 8 at multiple angular positions in this way, changes in the diameter of the molten zone 8 can be quickly detected even when the molten zone 8 is not a perfect circle when viewed in cross section. Therefore, it is possible to control the melting zone 8 in an optimal state.

Effects of the Invention As described above, according to the present invention, there is provided a line sensor for measuring the diameter of the melted zone, a binarizing means for binarizing the output of the line sensor, and A timing pulse generating means generates a timing pulse when a plurality of predetermined angular positions are reached for each rotation of the band, and a binarizing means binarizes the pulse signal from the timing pulse generating means. The measured signals are stored sequentially, and the molten zone diameter dimension at the angular position where the rate of change was the largest for each rotation is used as the measurement data, and the measurement data m (m is an integer) times before and the current measurement data are combined. The diameter of the molten zone is optimized for crystal growth. Therefore, the complicated work of the operator can be eliminated, and crystal growth can be performed almost unattended. Furthermore, since the diameter of the molten zone is measured at a plurality of angular positions, there is no need for complicated positioning between the rotation origin and the crystal plane.

The present invention is applicable not only to single crystal manufacturing using a dual circular infrared heating furnace, but also to other single crystal manufacturing apparatuses using, for example, a small circular infrared heating furnace.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view showing an example of an infrared heating single crystal manufacturing apparatus to which the present invention is applied. FIG. 2 is a partial front view of the infrared heating single crystal manufacturing apparatus shown in FIG. 1, without enlarging the melting zone. FIG. 3 is a schematic perspective view showing the construction of an embodiment of the present invention. FIG. 4 is a block diagram of an infrared heating single crystal manufacturing apparatus including the embodiment shown in FIG. 3. Figure 5 shows
FIG. 4 is a flowchart for explaining the overall operation of the infrared heating single crystal manufacturing apparatus including the embodiment shown in FIGS. 3 and 4. FIG. 1.2...Spheroidal mirror, 4.5...Halogen lamp, 6...Material rod, 7...Weighing crystal, 8...Melting zone, 12...Line sensor/camera , 17... Controller including control means, 18a, 18b... Timing pulse generator, 22... Line sensor, 24...
- Comparison means as a binarization means, 25... control means. Patent applicant Nichiden Kikai Co., Ltd. Suwa Seikosha Co., Ltd. Representative Patent attorney Kube Fukami (and 2 others) Pit 7 Diagram Collection 2 Figure 30 ] Figure S

Claims (1)

[Claims] An infrared heating crystal production device in which an infrared lamp is arranged as a heat source at one focal point of a spheroidal mirror, and a material rod and a seed crystal are arranged at the other focal point to form a molten zone. A method for controlling a diameter of a melted zone, the method comprising: a line sensor for measuring the diameter of a melted zone; a binarizing means for binarizing the output of the line sensor; and one revolution of the melted zone. timing pulse generating means for generating a timing pulse when a plurality of predetermined angular positions are reached; The measured signals are stored sequentially, and the diameter of the melted zone at the angular position where the rate of change is the most significant for each rotation is measured as m (m is an integer).
A control means performs calculation processing according to a predetermined calculation formula based on the previous measurement data and the current measurement data, and controls the amount of electricity supplied to the infrared lamp based on the calculation result. 1. A method for controlling a molten zone diameter in infrared heated crystal production, the method comprising maintaining a molten zone diameter optimal for the growth of crystals.