JP2816625B2 - Single crystal manufacturing apparatus and control method therefor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing a single crystal and a method for controlling the same, and more particularly, to an apparatus for producing a single crystal for measuring the purity of a gas in the apparatus and maintaining the quality of the single crystal, and a control thereof. It is about the method.

[0002]

2. Description of the Related Art Conventionally, this type of single crystal manufacturing apparatus has an airtight container 51 as shown in FIG. A crucible 5 made of graphite or quartz (silica) or the like is provided in the airtight container 51.
A cylindrical graphite heating element 59 (referred to as a graphite heater 59) for melting a semiconductor material 57 such as polycrystal inserted into the crucible 53 at a high temperature is provided outside the crucible 53. The semiconductor material 57 melted in the crucible 53 by the heat of the graphite heater 59 is brought into contact with the seed crystal 63 attached to the crystal pulling shaft 61, and pulls the seed crystal 63 while rotating the seed crystal 63 or the crucible 53 or both. A crystal 64 is grown. The airtight container 51 is filled with an atmosphere gas such as argon gas or nitrogen supplied from a pipe 67 by a vacuum pump (not shown) from a pipe 65 and supplied from a pipe 67, and the inside of the container is usually 10 ^-3 to 10 ^-1 Torr.
Has been decompressed. The pulling shaft 61 and the supporting shaft 69 of the crucible 53 rotate at a speed of usually 30 rpm or less.

[0003] Oil seals 71 and 73 made of Teflon or the like are attached to the lifting shaft 61 and the support shaft 69 in order to prevent air from flowing into the airtight container 51. Further, the airtight container is used to take out the crystal,
3. The structure is divided into at least two or more parts 75, 77, 79 for replacing or maintaining the heating element 59 and the like. O-rings 81 and 83 made of silicon or the like are arranged between the joining portions to maintain airtightness. A shutter 85 that closes when the single crystal rod 64 is removed is provided above the airtight container 51. In the above-mentioned conventional example, the pressure reduction is described, but the configuration for the atmospheric pressure is similarly configured.

[0004]

However, this single crystal needs to be of high purity. However, in a single crystal pulling apparatus using the Czochralski method (hereinafter referred to as CZ method), a source of contamination is generated during the single crystal pulling process. It is said that there are more than one. It has been pointed out that the atmosphere during lifting is one of the factors. In this case, evaporation of impurities from the high-temperature heating section is considered to be no problem by preventing the evaporant from the portion heated to a high temperature in the furnace from back-diffusing into the melt by the flow of the atmospheric gas. . However, if there is a leak in the airtight container or the pulling device, or if the purity of the atmosphere gas in the CZ pulling device changes, the impurity concentration in the pulled single crystal changes, and the quality of the pulling single crystal decreases, such as the purity. . In addition, the analysis of the crystal after the completion of the product of the single crystal rod reveals the decrease in the purity of the single crystal only after the crystal is analyzed. The present invention focuses on the above problems, and relates to a single crystal manufacturing apparatus and a control method therefor. In particular, the present invention measures a gas purity in a manufacturing apparatus and maintains a single crystal quality and a single crystal manufacturing apparatus and a control method thereof. It is about improvement.

[0005]

According to a first aspect of the present invention, there is provided an apparatus for producing a single crystal and a method for controlling the same, the method comprising the steps of: In a single crystal manufacturing apparatus using a sealing member on a shaft such as a crystal pulling shaft or a packing material such as an O-ring on a division surface of an airtight container, a component of an atmosphere gas for monitoring purity during growth of the single crystal. A mass spectrometer for measuring the concentration is attached. The second is based on the first invention
According to the invention, the mass spectrometer comprises an outlet pipe for taking out the gas from the airtight container, and a mass analyzer for analyzing the components and concentrations of the gas. Further, in the third invention, a differential evacuation device for reducing the pressure to a predetermined value of vacuum is provided between the airtight container and the mass analyzer.

According to a fourth aspect of the present invention, an airtight container for producing a single crystal by sending an atmospheric gas, wherein a sealing member is used for a shaft such as a pulling shaft of the single crystal, or a packing material such as an O-ring is used for a divided surface of the airtight container. In a single crystal manufacturing apparatus, at least two or more outlet pipes for guiding a gas for measuring components and concentrations of gas in an airtight container, and a mass analyzer for measuring components and concentrations of gas from the outlet pipes And a comparing device for determining leakage from the sealing material or the packing material based on the molecular weight of the mass spectrometer.

According to a fifth aspect of the present invention, in a single crystal manufacturing apparatus for manufacturing a single crystal by sending an atmosphere gas into an airtight container, the composition of the atmosphere gas is monitored in order to monitor the purity during the growth of the single crystal.
The concentration is measured, and the production of the single crystal is stopped when the component / concentration of the atmospheric gas exceeds a predetermined value.

[0008]

According to the above construction, a mass spectrometer is attached to a single crystal manufacturing apparatus, and the molecular weight and molecular structure of components such as organic molecules, water molecules, oxygen molecules, etc. in the apparatus are measured. The atmosphere of the gas is monitored. The transition of the composition and concentration of this gas is measured, and whether the transition of the composition and concentration of the gas exceeds a predetermined value, and whether or not the single crystal was formed with high purity by
Can be determined. For this reason, when the product of the single crystal rod is completed, the purity of the single crystal is known, and if there is an abnormality during the production, the apparatus is stopped, so that the man-hour and energy can be saved. In addition, gas components in the airtight container
Since the concentration is measured at least at two or more locations, it is possible to specify whether the leakage is from the sealing material or the packing material.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a single crystal manufacturing apparatus and a control method thereof according to the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a first embodiment of a single crystal manufacturing apparatus according to the present invention. In FIG. 1, the same parts as those of the related art are denoted by the same reference numerals, and description thereof will be omitted. The mass spectrometer 1 is provided in the single crystal manufacturing apparatus 100. The mass spectrometer 1 is composed of an outlet pipe section 5 for taking out a gas from the airtight container 51 and a mass analyzer 11 for analyzing the structure and molecular weight (component / concentration) of gas molecules. The outlet pipe part 5 is an airtight container 51.
A pipe 6 for drawing gas from the vicinity of the upper part of the crucible 53 in the drawing to the outside, a differential pumping device 7 attached to one end of the drawn pipe, and a vacuum pump for sucking gas from the differential pumping device 7 8. The mass analyzer 11 is composed of, for example, a quadrupole mass analyzer, a magnetic field mass analyzer and the like 13 for measuring a molecular weight and a molecular structure by ionizing a gas, and a data recorder 15. The mass spectrometer 11 is connected to a control device 20 for controlling the single crystal manufacturing apparatus 100. The control device 20 has a storage unit 21 for storing permissible predetermined values of components and concentrations of various gases. The comparison unit 23 compares the data with a predetermined allowable component / concentration value. The control unit 25 controls the single crystal manufacturing apparatus 100 when the measured data exceeds the predetermined value.

[0010] The control device 20 is connected to a warning device 26 for warning an operator when measured data exceeds a predetermined value, and a CRT device 27 for monitoring the transition. Further, when the measured data exceeds a predetermined value, it is connected to a stop device 28 that stops the manufacturing apparatus. For example, the stop device 28 reduces the amount of electric power supplied to the graphite heater 59 in the airtight chamber and activates the puller. The growth of the single crystal has been stopped. Although the example in which the data recorder is connected to the mass analyzer is described, the data recorder may be connected to the control device 20.

In the above configuration, usually, the crucible 53
The semiconductor material 57 melted therein is grown after being brought into contact with the seed crystal 63 attached to the crystal pulling shaft 61, and the single crystal rod is gently pulled up while rotating. At this time, the atmosphere gas such as argon gas and nitrogen supplied from the supply pipe 67 flows out of the exhaust pipe 65 through the periphery of the single crystal rod into the airtight container 51. The gas is taken out of the airtight container 51 by the outlet pipe section 5, reduced to a predetermined vacuum by the differential exhaust device 7, sent to the mass spectrometer 11, and the gas is ionized to measure the molecular structure and molecular weight. At this time, CHX, oxygen, C
O ₂ , etc. are measured sequentially.

For example, assuming that an abnormality occurs during a normal operation, leakage was actively generated from the oil seal 71 of the pulling shaft 61 (point A in FIG. 2). At this time, as shown in FIG. 2, the components and concentrations of the gas change, and the signal of CHX is abnormally increased. Also, at this time, it was found that the larger the leak amount of the oil seal 71, the larger the increase amount of the oxygen signal. Increasing the amount of CHX in the atmosphere gas increases the carbon concentration in the silicon melt and also increases the carbon concentration in the pulled single crystal rod. The single crystal rod was pulled up and analyzed and found that the carbon concentration changed from almost the same position where the oil seal 71 leaked positively. Although only the oil seal is described in the above embodiment, similar results can be obtained with the O-ring.

FIG. 3 shows a second embodiment of the single crystal pulling apparatus according to the present invention. In FIG. 3, the same components as those in the conventional and the first embodiments are denoted by the same reference numerals, and description thereof will be omitted. In the mass spectrometer 30, the conduit portion 31 is taken out from the exhaust pipe 65 below the airtight container 51, and one end 31 a of the conduit portion 31 is connected to the outside of the outlet pipe portion 5 for taking out the gas from the airtight container 51.
The port 33 a of the port solenoid valve 33 is connected to the other end 31 b of the port solenoid valve 33 to an exhaust pipe 65. Similarly, the outlet pipe section 5 taken out of the airtight container 51 is connected to the port 33b of the three-port solenoid valve 33, and the remaining port 33c of the three-port solenoid valve 33 is connected to the differential exhaust device 7.

In the above configuration, similarly to the first embodiment, the atmosphere gas such as argon gas and nitrogen supplied from the supply pipe 67 passes through the single crystal rod in the hermetic container 51.
It flows out of the exhaust pipe 65. This gas is transferred to an airtight container 5
The gas to be taken out (measured) is selected from the outlet pipe portion 5 and the conduit portion 31 of the exhaust pipe 65, and the position to be measured by the 3-port solenoid valve 33 is alternately selected according to a command from the control device 40. The component / concentration of the gas sent to the mass analyzer 11 via the differential exhaust device 7 is measured. Also at this time, the mass analyzer 11 sequentially measures CHX, oxygen, CO ₂ , and the like.

For example, assuming that an abnormality occurs during a normal operation, a leak was actively generated from the O-ring 83 at the joint of the airtight container 51 (point B in FIG. 4). At this time, the data measured from the conduit portion 31 of the exhaust pipe 65 causes a change in the gas component and concentration as shown in FIG. 4, the graphite heater 59 reacts with the air, and the signal of CO + N ₂ abnormally increases. doing. At this time, the data measured from the airtight container 51 to the outlet pipe section 5 showed that the molecular weight CO + N ₂ of the gas having the same tendency as in FIG. 4 was increased. FIG. 4 also shows that the amount of increase in the signals of oxygen and CHX is large as in the case of the leak of the oil seal 71, and that the leak from the O-ring 83 has occurred. The single crystal rod was pulled up and analyzed and found that the carbon concentration changed from the same position where the O-ring 83 leaked positively. As described above, it has been found that the leaking portion can be estimated by measuring the components and concentrations of the gas from the airtight container 51 and the gas from the outlet portion 5 and the conduit portion 31 of the exhaust pipe 65 and comparing them with the comparing portion 23. .

FIG. 5 is a view showing a gas leak measuring device and a crucible heating device control device of the single crystal pulling apparatus of the present invention. The gas leak measuring device is configured as follows. The ionization chamber 101 and the ion separation chamber 10 are connected from the inside of the airtight container 51 of the single crystal manufacturing apparatus 100 via the pipe 6.
2 are connected. The ions separated and sorted in the ion separation chamber 102 reach the ion detector 103. The ion detector 103 includes a secondary electron multiplier 104 and a Faraday cup 111. If the amount of ions reaching the ion detector 103 is extremely small, the central processing is performed via the secondary electron multiplier 104, the pulse amplifier 105, the waveform shaping circuit 106, the counter circuit 107, and the I / O input / output port 108. Input to the device 109. However, in the case of a large amount of ions, after reaching the Faraday cup 111, the ions are input to the central processing unit 109 via the DC amplifier 112, the sample and hold circuit 113, the A / D converter 114, and the I / O input / output port 108. .

The control device of the crucible heating device is configured as follows. The heating of the graphite heater 59 is performed by the power supply 1
21 through a breaker 122, a thyristor stack 123, a transformer 124, a diode stack 12
By reaching the heater 59 through 5, a three-phase full-wave clear-flow DC method is performed. The thyristor stack 123 is controlled by a thyristor control unit 126,
Central processing unit 128 via I / O input / output port 127
Do with. In addition, regarding the computer of the central processing unit,
Any of a one-chip microcomputer, a board computer, and a personal computer may be used, and they are separately described, but may be configured the same.

Next, the operation of the above configuration will be described. The measurement gas 101 is supplied from the inside of the airtight container 51 to the pipe 6.
To the ionization chamber 101. The transported measurement gas is a heated filament 101 in the ionization chamber 101.
It is ionized by the thermal electrons generated from a. The ionized molecular ions or atomic ions are supplied to the ion separation chamber 102.
Will be introduced. From the ionized mixed gas ions, only a target gas is separated and selected in the ion separation chamber 102 and reaches the ion detection unit 103. Ion detector 10
In the case of an extremely small amount, the ions that have reached 3 reach the secondary electron multiplier 104 by applying an electric field. The ions that have reached the secondary electron multiplier 104 are amplified and converted into electric signals. This signal is represented as a number per unit time. The output of the secondary electron multiplier 104 is the pulse amplifier 1
After being amplified at 05 and converted into a rectangular wave by the waveform shaping circuit 106,
The data is counted by the counter circuit 107 for a certain period of time and input to the central processing unit 109 via the I / O input / output port 108. The central processing unit 109 calculates a value correlated with the number per unit time, compares it with a value set in the storage device 110, and if the value exceeds the set value, the I / O
The data is input to the central processing unit 122 for controlling the graphite heater 59 via the input / output port 124. Further, an alarm is issued from the alarm device 26 as necessary.

However, when the amount of ionized gas is large, it is necessary to move straight to reach the Faraday cup 111.
The electric field of the next electron multiplier 104 is turned off. After reaching the Faraday cup, the DC amplifier 112 and the sample hold circuit 11
3, A / D converter 114, I / O input / output port 10
8 to the central processing unit 109. The output from the Faraday cup 111 is multiplied by a predetermined constant in the central processing unit 109 to calculate the density,
When the set value is compared with the set value within 0 and exceeds the set value, the central processing for controlling the graphite heater 59 is performed via the I / O input / output ports 108 and 127 in the same manner as in the case where the amount of ions is extremely small. Input to device 128. Further, an alarm is issued from the alarm device 26 as necessary.

A signal exceeding the set value is output to the I / O input / output 10
The central processing unit 128 for controlling the graphite heater, which has received the signals via the switches 8 and 127, closes the gate of the thyristor stack 123 via the thyristor control unit 126 and cuts off the anode current of the thyristor. Thereby, the heating of the graphite heater 59 is stopped.

[0021]

As described above, according to the apparatus for producing a single crystal and the method for controlling the same of the present invention, the components and concentrations of organic molecules, water molecules, oxygen molecules, and the like in the apparatus are measured to obtain the gas in the apparatus. By monitoring the atmosphere, it is possible to determine whether the transition of the composition and concentration of the gas exceeds a predetermined value, and whether or not the single crystal was formed with high purity. For this reason, when the product of the single crystal rod is completed, the purity of the single crystal is determined, and if there is an abnormality during the production, the apparatus is stopped, so that the man-hour and energy can be saved. If the amount of leakage is significant, the graphite heated to a high temperature in the airtight room will react with oxygen derived from air,
Although there is a case where remarkably deteriorated and it becomes impossible to use repeatedly, an excellent effect that the present invention can be prevented beforehand can be obtained since the leak amount can be known.

[Brief description of the drawings]

FIG. 1 is a schematic overall configuration diagram of a first embodiment of a single crystal pulling apparatus according to the present invention.

FIG. 2 is a diagram showing changes in gas components and concentrations when leakage from the oil seal portion of the present invention occurs.

FIG. 3 is a schematic overall configuration diagram of a second embodiment of the single crystal pulling apparatus of the present invention.

FIG. 4 is a diagram showing changes in gas components and concentrations when leakage from an O-ring portion of the present invention occurs.

FIG. 5 is a view showing a gas leak measuring device and a control device of a crucible heating device of the single crystal pulling apparatus of the present invention.

FIG. 6 is a schematic overall configuration diagram of one embodiment of a conventional single crystal pulling apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mass spectrometer 5 Lead-out pipe part 7 Differential exhaust device 11 Mass spectrometer 15 Data recorder 20 Controller 21 Storage part 23 Comparator 25 Control part 26 Warning device 27 CRT device 31 Conduit part 33 3-port solenoid valve 51 Airtight container 53 Crucible 59 Cylindrical graphite heating element 71, 73 Oil seal 81, 83 O-ring 100 Single crystal manufacturing equipment

Claims (5)

(57) [Claims] 1. An airtight container for producing a single crystal by sending an atmospheric gas, wherein a single crystal is manufactured using a sealing member on a shaft such as a pulling shaft of the single crystal, or a packing material such as an O-ring on a division surface of the airtight container. 3. A single crystal manufacturing apparatus according to claim 1, further comprising a mass spectrometer for measuring a component / concentration of an atmospheric gas for monitoring the purity of the single crystal during growth. 2. The single crystal manufacturing apparatus according to claim 1, wherein the mass spectrometer comprises a lead-out pipe portion for taking out the gas from the airtight container, and a mass analyzer for analyzing a component and concentration of the gas. 3. The apparatus for producing a single crystal according to claim 1, wherein a differential pumping device for reducing the pressure to a predetermined value is provided between the airtight container and the mass analyzer. 4. An airtight container for producing a single crystal by sending an atmospheric gas, wherein a single crystal is manufactured using a sealing member on a shaft such as a pulling shaft of the single crystal, or a packing material such as an O-ring on a divided surface of the airtight container. In the gas component in the airtight container
At least two or more outlet pipes for guiding the gas for measuring the concentration, a mass analyzer for measuring the component and concentration of the gas from the outlet pipe, and a sealing material or a packing material depending on the component and concentration of the mass analyzer. A single crystal manufacturing apparatus, comprising: a comparison device for determining leakage from the device. 5. A single crystal producing apparatus for producing a single crystal by sending an atmospheric gas into an airtight container, wherein a component and a concentration of the atmospheric gas are measured in order to monitor the purity of the single crystal during growth.
A method for controlling the production of a single crystal, characterized in that the production of a single crystal is stopped when the component / concentration of the atmospheric gas exceeds a predetermined value.