JPS63170297A - System for controlling runout width of single crystal silicon in cz furnace - Google Patents

Abstract

PURPOSE:To prevent the deterioration of quality and shape of a single crystal arising from oscillation, by detecting the high luminance points of a high-luminance band- shaped ring formed to the boundary part between the single crystal grown in a CZ furnace and melt by a specific camera and controlling the oscillation of a wire by means of a controller and wire steady rest. CONSTITUTION:A crucible 2 contg. a silicon melt 3 is so disposed in the CZ furnace 1 that the crucible can be driven to rotate. The columnar single crystal silicon 6 is stuck to a seed crystal 5 at the top end of a wire 4 suspended toward the center of the crucible 2 and is grown. The boundary part between the single crystal silicon 6 and the melt 3 is detected as the high-luminance band-shaped ring 7 by scanning the one-dimensional CCD camera 8. The two high-luminance points A, B thereon are inputted as detection signals an, bn (e.g.: a1 and b1 and a2 and b2) to a controller 10. The controller controls the runout width of the wire 4 by driving the wire steady rest 11 which is operated to decrease the runout width of the wire 4 by contacting the wire 4 when the displacement calculated by the steady rest 11, a floppy driving device 12, a CRT display 13, etc., exceeds a permissible value. The deterioration of the crystal is thus prevented and the quality thereof is improved.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides a single-crystal silicon amplitude control system in a CZ furnace that controls the amplitude of single-crystal silicon produced in a CZ furnace within a predetermined range. Regarding.

(Prior art) In recent years, the capacity of CZ furnaces has increased, and as a result, the wire method, which is less susceptible to the effects of microvibrations and allows the furnace height to be set low, is used, in other words, the seed crystal is suspended from the tip of the wire via a jig. ,
A method is mainly adopted in which the wire is rotated and wound while raising the produced single crystal silicon.

(Problem to be Solved by the Invention) However, in the above wire method, the rotation center of the wire (in other words, the rotation center of single crystal silicon) and the rotation center of the crucible (in other words, the rotation center of the silicon solution) are Single-crystal silicon tends to swing due to misalignment, which causes deterioration of the single crystal, and in the case of the worst case, there is a risk of polycrystalization, deterioration of shape, and (deformation). .

Therefore, the present invention detects the swing width of the center point of single-crystalline silicon and controls the swing width of the wire based on this detected value, thereby reducing the risk of deterioration of the quality and shape of the single crystal due to the swing. The purpose is to prevent this and improve product quality.

(Means for Solving Problems and Their Effects) The single-crystal silicon amplitude control system of the present invention controls the diameter of the band-shaped ring formed at the boundary between the silicon melt in the crucible and the single-crystal silicon at the tip of the wire. a one-dimensional CCD camera that scans a straight line containing the ring and detects two high-intensity points on the belt-like ring; a wire steadying device that contacts the wire and reduces twisting of the wire; and a control device that includes a microcomputer. and, within a predetermined period, the control device sequentially calculates the midpoint between the two high brightness points based on the detection signal from the one-dimensional CCD camera,
The maximum displacement of the intermediate point is calculated based on the calculated intermediate point, and when this displacement exceeds an allowable value, the wire steady rest device is driven to control the swing width of the wire.

' Therefore, by setting the above series of control cycles to be larger than the oscillation cycle of the single crystal silicon during growth, the misalignment between the single crystal silicon and the wire can be minimized as the swing width of the wire is manipulated. Therefore, deterioration of the single crystal and deterioration of the shape can be prevented.

(Example) An embodiment of the present invention will be described below based on the drawings.

FIG. 1 is a schematic diagram showing a CZ furnace and its control system during growth of single crystal silicon. In Figure 1, l is CZ
A furnace chamber, 2 a crucible disposed within the CZ furnace chamber 1 so as to be rotatably driven by a motor, 3 a silicon melt in the crucible 2, 4 a wire hanging down from the center of the crucible 2, 5 is a seed crystal attached to the lower end of wire 4, 6
is single crystal silicon that adheres to the seed crystal 5 and grows.

A winder (5!l not shown) is provided above the chamber 1 to rotate and wind up the wire 4. Furthermore, according to a COD camera, etc., the boundary between the surface of the single crystal silicon 6 and the silicon melt 3 in the CZ furnace can be seen as a high-intensity band-shaped ring 7'' (hereinafter referred to as a fusion ring) as shown in Fig. 2. Therefore, a one-dimensional CCD camera 8 that scans on a scanning line R that includes the diameter of this fusion ring 7 is installed diagonally above the window 9.

This one-dimensional camera 8 is configured by arranging, for example, 2048 elements in a row, and these elements are numbered from 0 to 2048.
This indicates the array position starting from number 0. In FIG. 2, C indicates the center of the single crystal silicon 6. Therefore, the one-dimensional CCD camera 8 detects two high brightness points A and B on the fusion ring 7 as shown in FIG. Detection signals a, , b are obtained corresponding to the array positions of the elements. Detection signal a of this one-dimensional CCD camera 8-
1°bn is input to the control device 110, and this control device 1
0 is connected to a wire steady rest device 1'l, a floppy drive device 12, and a CRT display 13.

The wire steady rest device ull is shown in FIGS. 3(a) and (
As shown in b), a rod 13, a pole screw 15.
A speed reducer 16 and a pulse motor 17 are attached.

The rod 13 is supported so as to be movable in a direction orthogonal to the wire 4.

The tip thereof passes through the upper part 91a, and a 7-shaped holding member 13a that contacts the wire 4 is attached to this tip. The above-mentioned pole screw 15 is.

The rod 1 is rotatably supported parallel to the rod 13.
3 is screwed into a nut member 14 fixed to the central portion thereof, and is connected to a pulse motor F via a speed reducer '16, and the lot 13 is moved forward and backward by the rotational drive of the pulse motor 17. In the figure, 18 is an airtight seal, and 19.20 is a limit switch.

Further, as shown in FIG. 4, the control device IO includes an interface circuit 21 that processes the detection signal alset)fl of the one-dimensional CCD camera 8 based on clock pulses from a microcomputer (MPU) 20, which will be described later. Microcomputer 20 and wire steady rest device 1
It is composed of a drive circuit 22 and the like for driving 1.

The microcomputer 20 is composed of an I10 port, a memory, an arithmetic section, a control section, each register, a clock generator, etc., and processes according to a program written in the memory, and sends signals to a drive circuit 22 composed of a transistor circuit. Output and wire steady rest device 11
In conjunction with this, the rod 13 and the holding member 13a at its tip are extended, and the V groove of the holding member 13a contacts the wire 4 to control the swing width of the wire. It is done.

Next, the operation of this embodiment will be explained based on FIG. 5.

FIG. 5 is a flowchart showing an outline of the wire runout width control process.

When the power switch is turned on, power is supplied to the microcomputer 20, other circuits, and the CZ furnace, and control starts, and inside the microcomputer 20,
Initial settings are performed in step PL. In the one-dimensional CCD camera 9, as shown in FIG. 6, since the single crystal silicon 6 oscillates, the two high brightness points A and B of the fusion ring 7 are displaced, and the corresponding detection Signal (a*+bt)s(ansb*)"" (an-bn)
These detection signals an are detected in step P2.

b, are read at predetermined time intervals. In step P, the detected position in the one-dimensional COD camera 9 is converted using the detection signals an and bn, and in step P4, based on the position-converted signals a'ゎ and bo, C1=a, +bn
/2, each intermediate point Cn is sequentially stored in the memory. In this case, the above calculation and storage process are performed N times within a preset period that is longer than the oscillation period of single crystal silicon 6. When these processes reach N times in step P, the maximum value Cs is selected from among the 1, 2.3-N intermediate points Ci stored in the memory in step P6.
aw and the minimum value Cmin are calculated, and in step P7 Ca
The variation range C- of the intermediate point position is determined by the calculation ``C-yaw〇 sim.Then, in step P, the calculation ``Cd''C, -c is calculated based on the circularity of the single crystal silicon 6 (C is the correction The correction value Cd' of the fluctuation width is determined by the constant), and in step P, the fluctuation width Cd'' is determined to be the actual length, and (-m
) is converted to In this length conversion, assuming the length of one array element to be k (1m), Ln = k x Cd”
By the calculation (■■), it is obtained as the amplitude of the original center point C.

Next, in step P1°, it is determined whether or not the wire steady rest device 11 is currently performing a steady rest operation, and if the steady rest operation is currently being performed, steps pea to P1 are performed as described later.
Shift to process 0. If steady rest operation is not in progress,
Step Pit~PI? Step pH
At step P, it is determined whether or not the amplitude of fluctuation is smaller than a preset allowable amount L0, and if L≦L0, the process returns to step P. Also, if L≦L0, fP, □=L x
Obtain the operating position P1 of the wire by calculating O and 7, select the time when the wire and the holding member are not in contact with each other in PI3 so as not to apply vibration to the wire, and proceed to step P14 and pH1.
The above goal! The extension operation of the presser member 13a is performed step by step (0, 5■■) until reaching lp. When the presser member 13a reaches the target position,
In step Pi6, a periodic timer for the control cycle used to update the steady rest position is started, and in step PTT, an error monitoring timer for checking the effect of the steady rest control is started, and the process returns to step P3. Stop control is performed. Also, the above step P. If the steady rest is in use, step Pl&1 determines whether the period timer has gone up or not. If it has gone up, step pts determines whether the current runout width is within the allowable value L0, and if it is within the allowable value. In this case, after confirming that there is no contact between the wire and the holding member in step P2, the series of wire resting operations is canceled in step pat, and the process returns to step P2. If it is not within the allowable value, the current runout L1 is set to the previous value in step P22. It is determined whether the reduction is within a predetermined reduction range, for example, 30%, than -1, and if it is not reduced, step pat and step P
Proceeding to ffi8, it is determined whether the current runout Ln has increased or the error monitoring timer has run up, and if both are affirmative, an error is reported in step PH9. If the swing amplitude is within the 30% reduction range in step pat, then in step pts, for example, P
The wire steady rest operating position Pn is recalculated based on the previous value pn-1 by the calculation n=0.7 Then, the steady rest device 11 is extended based on the updated target position Pn until it reaches the updated target position P, and the process returns to step P2.

In this way, in this embodiment, when the swing width of the center point of the growing single crystal silicon exceeds a predetermined value, the steady resting operation of the single crystal silicon wire is performed in response to the swing width. Therefore, the fluctuation of single crystal silicon can be quickly corrected.

(Effects of the Invention) As explained above, according to the present invention, the maximum amplitude of the center point of the growing single crystal silicon is detected, and when this amplitude exceeds a predetermined value, the By performing the wire steadying operation, the swinging can be quickly corrected, reducing the occurrence of single crystal silicon deterioration and shape deterioration, and clarifying the relationship between the wire holding position and the touch. This makes it possible to further improve the precision of production and improve the quality of single crystal silicon.

[Brief explanation of the drawing]

1 to 6 show an embodiment of the present invention, FIG. 1 is a schematic diagram showing a CZ furnace and control system during single crystal silicon growth, and FIG. 2 is a schematic diagram showing the brightness distribution of a fusion ring. , FIGS. 3(a) and 3(b) are a plan view of the wire steady rest device and a sectional view taken along the line A-A in FIG. 3(a), FIG. 4 is a schematic configuration diagram of the control device, and FIG. 5 6 is a flowchart showing an outline of control processing, and FIG. 6 is an explanatory diagram of detection signals by a one-dimensional CCD camera. 2.3... Crucible and silicon melt 4.5-... Wire and seed crystal 6... Single crystal silicon 7... Fusion ring (band-shaped ring) 8... One-dimensional COD camera 10.20 --Control device and microcomputer 1
1-...Wire steady rest device al ~a,,b,""-b,""Detection signal Patent applicant Kyushu Electronic Metals Co., Ltd. Patent applicant Osaka Titanium Manufacturing Co., Ltd. Representative Patent attorney Masa Sumi Mori 2. 3-... Crucible and silicon melt 4.5-... Wire and seed crystal 6... Single crystal silicon 7... Fusion ring (band-shaped ring) 8... One-dimensional CCD camera 10.20-...・Control device and microcomputer 1
1...Wire steady rest vtWi a, ~a7. et al., ~b, ---Detection signals Fig. 2, Fig. 6, a2a, b2b. (Issuance of procedural amendments) March 14, 1988 Director General of the Patent Office Kunio Ogawa 1 Indication of the case 1988 Patent Application No. 2750 2 Name of the invention Single crystal silicon amplitude control system in a CZ furnace 3 Amendment Relationship with cases involving patent applicants

Claims (1)

[Claims] A crucible containing molten silicon is rotatably arranged in a CZ furnace, and single crystal silicon is grown by adhering to a seed crystal at the tip of a wire hanging down toward the center of the crucible to produce columnar single crystal silicon. In the amplitude control system of the manufacturing equipment, a straight line including the diameter of the band-shaped ring formed at the boundary between the single crystal silicon and the silicon melt during the growth is scanned, and two high-intensity points of this band-shaped ring are detected. a one-dimensional CCD camera that detects the wire, a wire steady rest device that contacts the wire and reduces the swing width of the wire, and a control device that includes a microcomputer, and within a predetermined period, the control device controls the The midpoint between the two high brightness points is calculated one after another based on the detection signal from the one-dimensional CCD camera, the maximum displacement of the midpoint is calculated based on the calculated midpoint, and this displacement exceeds the allowable value. 1. A single crystal silicon swing amplitude control system in a CZ furnace, characterized in that the wire swing rest device is driven to control the swing width of the wire when the wire exceeds the swing range.