JPS6117537B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a silicon granule supply device for supplying silicon granules according to crystal growth capacity in a crystal pulling device.

[Technical background of the invention and its problems]

In general, as semiconductor substrates (wafers) become cheaper,
Needless to say, indirect material costs are saved. As a countermeasure, it is possible to continuously supply silicon material without lowering the furnace temperature. Once the furnace has cooled down,
This is because expensive crucibles used for crystal growth may crack or break. Naturally, a considerably long cooling time was required to bring the temperature from high temperature to room temperature, and a time to raise the temperature was also required to raise the temperature again, so the operating efficiency of the apparatus was significantly reduced. Further, the yield of the product was also poor because the dopant concentration was different between the beginning of pulling and the time of completion of pulling.

[Purpose of the invention]

The purpose of this invention is to steadily supply silicon granules according to the crystal growth capacity without drastically changing the temperature inside the furnace, and to enable long-term unmonitored operation, thereby making crystals inexpensive. , provides a silicon granule supply device that can vary the dopant concentration in the crystal substrate by providing multiple locations in one crucible, and can control the temperature curve inside the crucible to an ideal level by varying the supply amount. It is to be.

[Summary of the invention]

A casing in an inert gas atmosphere, a hopper disposed inside the casing to hold and store silicon granules, a movable plate that holds the hopper and has a sliding surface in the vertical axis direction, and A load transducer that weighs silicon granules by contacting multiple points, a fixed plate that holds this load transducer, a movable hopper that receives the silicon granules discharged from the tip of the hopper, and a gate height that adjusts the position of this movable hopper. a straight feeder and a trough for conveying the silicon granules discharged from the movable hopper; a quartz port for guiding the silicon granules discharged from the trough to the crucible of the heating furnace; and a silicon granule between the movable hopper and the trough. This is a silicon granule feeding device equipped with a unclogging device for unclogging granules.

[Embodiments of the invention]

The silicon granule supply device of the present invention is constructed as shown in FIG. (for example, Ar) to prevent oxidation inside the crucible (described later) through the quartz port (described later).

Such a housing 17 is provided with a funnel-shaped hopper 2 for holding and storing the silicon granules 1, and is attached to a movable plate 3 that can be moved in the vertical axis direction. A plurality of low-friction bearings 5 are provided in the circumferential direction of the movable plate 3 so that it can move relative to the fixed plate 4 directly below it. The fixed plate 4 has
A plurality of load transducers 6 for weighing the silicon granules 1 are provided in contact with the movable plate 3 in the circumferential direction. This load converter 6 measures the hopper 2, movable plate 3, and silicon granules 1, but a control panel (not shown) measures the total load minus the hopper 2 and movable plate 3, i.e. Only silicon granules are now visible.

Furthermore, a movable hopper 7 is provided below the hopper 2 to receive the silicon granules 1 discharged from the tip of the hopper, and a trough 9 is disposed in the horizontal portion 7a of the casing 7 adjacent to the movable hopper 7. ing. A quartz port 10 is arranged vertically near the tip of the trough 9 exposed outside the housing 7, and the quartz port 10 is located in a heating furnace 45 having a crucible (not shown). Naturally, the quartz port 10 is sealed with the heating furnace 45 and with the horizontal portion 17a of the housing 17 by the bellows 46.

During operation, the silicon granules 1 charged into the hopper 2 move downward due to their own weight, and the lowest ones enter the movable hopper 7. The silicon granules 1 in the movable hopper 7 fall onto the trough 9 of the linear feeder 8 by their own weight in the same manner as described above. The silicon granules 1 that have fallen onto the trough 9 are moved in the P direction by the vibration motion of the linear feeder 8. Finally, it passes through the quartz port 10 and enters the crucible in the heating furnace 45.

Further, the device of the present invention not only simply supplies the silicon granules 1, but also includes a device 11 for unblocking the silicon granules 1. That is, the particle size of silicon granules 1 is generally 0.4 to 1.0 mm, but in rare cases it is 1.5 mm.
Items larger than 3 mm or rod-shaped instead of spherical pass through the mesh sieve in the previous step and get stuck between the movable hopper 7 and the trough 9, causing clogging. When blockage occurs, the supply of granules naturally stops, which in turn changes the temperature profile within the crucible. Therefore, in the device of the present invention, clogging is automatically detected by the control system described later, and when the silicon granules 1 stagnate for a set time, the connecting rod 12 fixed to the movable hopper 7 is raised by the actuator 13. , a gap 14 between the lowermost end of the movable hopper 7 and the upper surface of the trough 9
becomes large and the blockage is cleared. Naturally, the movable hopper 7 has upper and lower slides 15 so that it can be raised and lowered. Also, the original gap 14
The adjustment of the connecting rod 12 is performed by the manipulator 16.
Adjust by moving. This part is called a gate height adjustment device 44 .

Next, the following can be considered as maintenance for this device. That is, one of them is to re-inject the silicon granules, and at this time, the clamper 19 is raised by moving the lever 18 in the Q direction. The lift height of the clamper 19 changes as the lever 18 moves. The moving shaft 20 receives this, and the clamper 19 finally rises. The moving shaft 20 is such that when the lever 18 is in the state shown in FIG.
The lid 22 is held down. Note that an O-ring 23 is provided between the lid 22 and the housing 17 to prevent leakage. Another maintenance step is adjusting the gate 14. At this time, the door 24 provided on the side surface of the housing 17 is opened, the adjustment is made by turning the manipulator 16, and the door 24 is closed again after the adjustment. still,
Similar to the above, a gasket 25 is provided here to prevent leakage.

Next, the control system of this device will be explained with reference to the block diagram of FIG. First, input/output will be explained. The input signal is the load transducer 6 for measuring the weight of the silicon granules 1 described above. In this invention, three load transducers 6 are used. In addition, there is a sensor 28 that detects the position of the melt surface 27 in the crucible 102, but in this invention, touch sensors 28-1, 28-2, 28-3 made of carbon are used.
are used, and are provided at three locations within the crucible 102. This touch sensor 28-1 detects the melt level 27 at a steady state, and the touch sensor 28-1 detects the melt level 27 at a steady state.
The touch sensor 8-2 detects the lower end area of the crucible 102 to detect an extremely low amount of the melt 29, and the touch sensor 28-3 detects the upper end area of the crucible 102 to detect an excess of the melt 29. On the other hand, output signals include a linear feeder 8 that conveys silicon granules 1 on a trough 9 and an actuator 13 that converts a gap 14 between the movable hopper 7 and the trough 9.

The load converter 6 is connected to an amplifier 33, but the input signal is amplified by this amplifier 33, and after the amplifier 33 there is a remaining amount indicator 34 that indicates the remaining amount of silicon granules 1. Furthermore, the input signal after amplification enters the slope calculation circuit 35, and the silicon granule 1
The slope of the supply amount is calculated. Further, the supply amount setting switch 36 is changed by the switch signal of the touch sensor 28 , and the signal is sent to the slope calculation circuit 35.
The comparison circuit 37-1 compares and verifies the output signal with the output signal of , and inputs it to the PID circuit 38 later. The changeover switch 39 is for automatic/manual switching, and a variable resistor 40 is arranged on the manual side. Further, the signal of the supply setting switch 36 is further compared with the signal output from the comparison circuit 37-1 via the supply management width setting device 41 in the comparison circuit 37-2. When the control width exceeds the setting and continues for more than the time set by the timer circuit 47, the alarm 43 and actuator 13 are activated. That is, the device determines that granule clogging has occurred and releases the clogging by itself. Further, the actual supply amount is displayed on an actual supply amount display 47 after the slope calculation circuit 35. The supply amount setting display is shown on the setting display 51 after the supply amount setting switching 36 described above. Furthermore,
There is a deviation display 48 for recognizing whether the adjustment of the PID circuit 38 is successful, and below this deviation display 48, the output to the straight feeder 8 is displayed 49. Incidentally, interfaces between the main body of the control system and the output section are shown at 50-1, 50-2, and 50-3.

Next, the control method will be described below. That is, the supply amount of the silicon granules 1 is set in two stages so as to increase or decrease the extremely small range of the touch sensor 28-1 that detects the liquid level when the melt 29 is steady during crystal pulling;
Automatic control is possible for each. in particular,
If the melt 29 increases and comes into contact with the touch sensor during steady state, the supply amount is reduced (e.g. 1.1 g/min), and conversely, when the melt 29 decreases and separates from the touch sensor 28-1, the supply amount is increased (e.g. 1.2g/min). As a result, changes in the amount of melt 29 in the crucible 102 can be reduced, so that changes in temperature applied to the outside can be reduced. FIG. 3 shows the controlled state of silicon granules. That is, this FIG. 3 shows the above supply setting A31 (1.1g/mi) for the ideal supply line 30-1.
n), the supply setting B32 (1.2 g/min) is shown being switched. Further, the fluctuation in each supply setting is shown as an actual supply line 30-2, and the allowable range of the fluctuation is shown as a supply management width 33.

〔Effect of the invention〕

According to this invention, silicon granules are constantly supplied without drastically changing the temperature inside the furnace, and long-term unmonitored operation is possible. This results in cheaper crystals. Further, by providing a plurality of devices of the present invention in one crucible, changing the dopant concentration of the silicon granules held by each crucible, and controlling the amount of supply thereof, the dopant concentration of the crystal substrate can be varied. Furthermore, by differentiating the supply amounts from a plurality of devices as described above, the temperature curve inside the crucible can be controlled to an ideal value.

In this invention, what is supplied is silicon granules, but the present invention is not limited to this, as long as the particle size is approximately uniform, the material and purpose of use may be any, and the present invention can be applied to materials other than silicon granules.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a silicon granule feeding device according to an embodiment of the present invention, FIG. 2 is a block diagram showing a circuit for controlling the device of the present invention, and FIG.
The figure is a characteristic curve diagram showing the control state of silicon granule supply. 1... Silicon granules, 2... Hoppers, 3...
Movable plate, 4... fixed plate, 6... load converter, 7...
...movable hopper, 8...straight feeder, 9...trough, 10...quartz port, 11 ...that is, release device, 13...actuator, 28 ...touch sensor, 29...molten material, 44 ...gate height Size adjustment device, 102... crucible.

Claims (1)

[Claims] 1. A casing in an inert gas atmosphere, a hopper disposed within the casing for holding and storing silicon granules,
a movable plate that holds the hopper and has a sliding surface in the vertical axis direction; a load transducer that contacts the movable plate at multiple points in the circumferential direction to measure silicon granules;
A fixed plate that holds the load converter, a movable hopper that receives the silicon granules discharged from the tip of the hopper, a gate height adjustment device that adjusts the position of the movable hopper, and a conveyor for transporting the silicon granules discharged from the movable hopper. a quartz port for guiding silicon granules discharged from the trough to a crucible of a heating furnace; and a release device for unclogging the silicon granules between the movable hopper and the trough. Characteristic silicon granule supply device. 2. The silicon granule feeding device according to claim 1, wherein the position of the movable hopper can be changed using an actuator. 3. The silicon granule supply device according to claim 1, wherein the load converter receives changes in the supply amount of the silicon granules and changes the amplitude of the linear feeder. 4 Equipped with a touch sensor for detecting the position of the melt surface of the crucible, a touch sensor for detecting overflow of the melt from the crucible, and a touch sensor for detecting that the melt in the crucible has decreased to a minimum. A silicon granule supply device according to claim 1. 5. The silicon granule feeding device according to claim 1, wherein the amplitude of the linear feeder is changed in accordance with changes in the position of the melt level in the crucible.