JP2021088467A - Single crystal growth method and single crystal growth apparatus - Google Patents

Abstract

To grasp at once a form of raw material melt stored in a crucible.SOLUTION: There is provided a single crystal growth method for growing a single crystal S by a Czochralski method. The single crystal growth method has a light irradiation and reception step for irradiating a liquid surface MA of raw material melt M stored in a crucible 3 from above with emission light emitted from a light source 14, and receiving reflected light reflected by the liquid surface MA of the raw material melt M, and a determination step for determining whether a form of the liquid surface MA of the raw material melt M is normal, based on a received light amount per unit time in the light irradiation and reception step.SELECTED DRAWING: Figure 1

Description

The present invention relates to a single crystal growing method and a single crystal growing device for growing a single crystal by the Czochralski method.

As a method for producing a single crystal such as a silicon single crystal, a method called a Czochralski method (hereinafter referred to as a CZ method) is known. In the CZ method, a single crystal is produced by landing a seed crystal on the liquid surface of a silicon melt in a crucible and pulling the seed crystal upward.

By the way, during the growth of a single crystal, various parameters such as the gap between the heat shield and the liquid level of the silicon melt and the diameter of the silicon single crystal to be grown are used for the purpose of obtaining a higher quality single crystal. Is being monitored. For example, Patent Document 1 describes an apparatus for detecting an abnormality in the liquid level of a silicon melt.

Japanese Unexamined Patent Publication No. 9-278586

By the way, the apparatus described in Patent Document 1 can detect an abnormality in the liquid level of the silicon melt, but if any abnormality occurs in the morphology of the liquid level of the silicon melt, normal measurement can be performed. become unable. Therefore, when an abnormality occurs in the liquid level, a system capable of detecting the abnormality is desired.

The present invention is a single crystal growing method and a single crystal growing method capable of immediately grasping whether or not the morphology of the liquid surface of the raw material melt contained in the crucible is normal when growing a single crystal by the Czochralski method. The purpose is to provide the device.

The single crystal growing method of the present invention is a single crystal growing method for growing a single crystal by the Czochralski method, and emits light emitted from a light source with respect to the liquid surface of the raw material melt contained in the crucible from above. The form of the liquid surface of the raw material melt is based on the irradiation and light receiving step of receiving the reflected light reflected on the liquid surface of the raw material melt and the light receiving amount per unit time in the irradiation and receiving step. It is characterized by having a determination step of determining whether or not it is normal.

In the determination step, when the amount of light received per unit time decreases and becomes lower than the threshold value, it is preferable to determine that the liquid surface morphology of the raw material melt is not normal.

In the irradiation / light receiving step, when the diameter of the single crystal is increased, the emitted light emitted from the light source is said to detect the meniscus generated at the interface between the edge of the single crystal and the raw material melt. The position where the raw material melt is irradiated on the liquid surface may be adjusted.
The meniscus is a curved liquid surface morphology generated by surface tension at the interface between the edge of a single crystal and the raw material melt.

The single crystal growing device of the present invention is a single crystal growing device that grows a single crystal by the Czochralski method, and is ejected from above with respect to the crucible containing the raw material melt and the liquid surface of the raw material melt. A form of the liquid surface of the raw material melt based on a light source that emits emitted light, a light receiving portion that receives reflected light reflected by the liquid surface of the raw material melt, and a light receiving amount per unit time in the light receiving unit. It is characterized by having a determination unit for determining whether or not is normal.

In the single crystal growing device, the single crystal growing device is arranged outside the chamber and can move in the vertical direction, reflects the emitted light emitted downward from the light source, guides the reflected light into the chamber through the window portion, and transmits the reflected light. A movable mirror that reflects and guides it to the light receiving portion, and the emitted light that is arranged in the chamber and guided into the chamber by the movable mirror is reflected toward the liquid surface and the reflected light is reflected. The configuration may include a prism mirror that guides the outside of the chamber through the window portion.

In the single crystal growing apparatus, the emitted light is a movable mirror so as to detect a meniscus generated at an interface between the edge of the single crystal and the raw material melt when the diameter of the single crystal is increased. The position of the above may be adjusted.

According to the present invention, the state of the liquid level of the raw material melt can be immediately grasped by determining whether or not the shape of the liquid level of the raw material melt is normal based on the amount of light received.

It is the schematic sectional drawing of the pulling device of embodiment of this invention. It is the schematic which looked at the liquid level morphology determination apparatus of embodiment of this invention from the direction different from FIG. It is a figure explaining the vertical movement of a movable mirror. It is the schematic explaining the positional relationship between a silicon single crystal and a laser beam. It is a schematic diagram explaining how the laser beam and the meniscus interfered with each other due to the expansion of the diameter of the silicon single crystal. It is a flowchart of the single crystal growth method of embodiment of this invention. It is a graph which shows the relationship between the diameter of a silicon single crystal, and the light receiving frequency.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
[Pulling device]
FIG. 1 is a schematic cross-sectional view of the pulling device 1 according to the embodiment of the present invention. FIG. 2 is a schematic view of the liquid level morphology determining device 12 provided in the pulling device 1 as viewed from a direction different from that of FIG. In the figure, the X-axis, Y-axis, and Z-axis that are orthogonal to each other are shown for easy understanding of the structure (the same applies to other figures). The X-axis and Y-axis correspond to the horizontal direction, and the Z-axis corresponds to the vertical direction.
It should be noted that FIG. 1 is a view of the locus of the laser beam L of the liquid level morphological determination device 12 viewed from the side (direction along the Y axis), and FIG. 2 is a view showing the locus of the laser beam L from the front (with the X axis). It is a view from the direction along the line). Further, in FIG. 1, the laser beam L is guided by the movable mirror 16 and the prism mirror 17, but in FIG. 2, the movable mirror 16 and the prism mirror 17 are omitted.

The pulling device 1 is a device for pulling and growing a silicon single crystal S by the Czochralski method. As shown in FIG. 1, the pulling device 1 includes a chamber 2 constituting an outer shell, a crucible 3 arranged in the center of the chamber 2, a heater 4, and a liquid level morphological determination device 12. ..

The crucible 3 is a container that has a circular shape when viewed from above in the vertical direction and stores the silicon melt M (raw material melt). The crucible 3 has a double structure composed of an inner quartz crucible 3A and an outer graphite crucible 3B. The crucible 3 is fixed to the upper end of a support shaft 5 that can rotate and move up and down and extends along the Z axis.

The heater 4 is a heating device that heats the silicon melt M in the crucible 3. The heater 4 has a cylindrical shape and is arranged coaxially with the central axis A of the crucible 3 on the outside of the crucible 3. The heater 4 is a resistance heating type so-called carbon heater. A heat insulating material 6 is provided on the outside of the heater 4 along the inner surface of the chamber 2.

Above the crucible 3, a pull-up shaft 7 is arranged coaxially with the support shaft 5. The pull-up shaft 7 is formed of a wire or the like. The pull-up shaft 7 rotates clockwise or counterclockwise at a predetermined speed. A seed crystal SC is attached to the lower end of the pull-up shaft 7. The pull-up shaft 7 rotates the seed crystal SC (silicon single crystal S) clockwise or counterclockwise when viewed from above in the vertical direction.

A heat shield 8 is arranged in the chamber 2. The heat shield 8 has a substantially conical cylinder shape and surrounds the silicon single crystal S being grown above the silicon melt M in the crucible 3.
The heat shield 8 blocks high-temperature radiant heat from the silicon melt M in the crucible 3, the heater 4, and the side wall of the crucible 3 with respect to the growing silicon single crystal S. The heat shield 8 suppresses the diffusion of heat to the outside in the vicinity of the solid-liquid interface, which is the crystal growth interface, and controls the temperature gradient in the pulling axial direction of the central portion of the single crystal and the outer peripheral portion of the single crystal. Take a role.

A gas introduction port 10 is provided in the upper part of the chamber 2. The gas introduction port 10 introduces an inert gas G such as argon gas into the chamber 2. An exhaust port 11 is provided in the lower part of the chamber 2. The exhaust port 11 sucks and discharges the gas in the chamber 2 by driving a vacuum pump (not shown). The inert gas G introduced into the chamber 2 from the gas introduction port 10 descends between the growing silicon single crystal S and the heat shield 8. Next, the inert gas G passes through the gap between the lower end of the heat shield 8 and the liquid surface of the silicon melt M, and then flows toward the outside of the heat shield 8 and further toward the outside of the crucible 3. After that, the inert gas G descends outside the crucible 3 and is discharged from the exhaust port 11.

[Liquid level morphology determination device]
The liquid level morphology determination device 12 is a device that determines the morphology of the liquid level MA of the silicon melt M. Specifically, the liquid level morphological determination device 12 is a device capable of determining that the morphology of the liquid level MA is not normal, such as a undulating form of the liquid level MA like a wave. Is.
The liquid level morphological determination device 12 of the present invention reflects the emitted light emitted from the light source by the liquid level MA, and whether or not the morphology of the liquid level MA is normal is determined by whether or not the reflected light can be received by the light receiving device. To judge.
Here, the fact that the morphology of the liquid level MA of the silicon melt M is not normal means that there is some abnormality in the growth of the single crystal and the morphology of the liquid level MA is not recognized when the single crystal is normally grown. Say that it is. For example, a form in which the liquid level MA has undulations such as waves can be mentioned. In addition, as another example of abnormalities, there is some abnormality in the growth of the single crystal, which is not observed when the single crystal is normally grown. The liquid level MA is curved or the liquid level MA is inclined. There is a form such as a crystallized form. Further, as a specific example in which there is some abnormality in the growth of a single crystal, the crystal diameter deviates from the set value of the crystal diameter due to a malfunction of the device and the crystal diameter becomes large, and the crucible deviates from the set value of the crucible rotation speed. Rotation and rotation of the crucible can be mentioned. In addition, there are cases where the crystal diameter setting value set by the operator or the crucible rotation speed setting value is incorrect due to human error, and when a natural disaster hinders the growth of a single crystal, for example, due to an earthquake. In some cases, the melt in the crucible shakes significantly.

As shown in FIGS. 1 and 2, the liquid level morphology determination device 12 includes an emission light receiving unit 13, a movable mirror 16, a prism mirror 17, a control device 20, and a display device 23. In FIG. 2, the incident angle θ1 and the reflection angle θ2 of the laser beam L on the liquid surface MA are shown to be large, and the angles θ1 and θ2 are actually small angles of 5 ° or less. That is, the laser beam L is irradiated vertically or substantially perpendicularly to the liquid surface MA from above.

The emission / light receiving unit 13 is a unit that is arranged outside the chamber 2 and emits and receives the laser beam L. The emission light receiving unit 13 includes an emission device 14 that emits laser light L1 (emission light) and a light receiving device 15 (light receiving unit) that receives laser light L2 (reflected light).
The light receiving device 15 includes a lens 18 that collects the incident laser beam L2 and a sensor 19 that detects the focused laser beam L2.

The emitting device 14 is, for example, a device using a laser light source having a wavelength of 400 nm to 550 nm as a light source. As described above, by using a laser light source having a wavelength significantly different from that of the ghost light having yellow, red, and near-infrared wavelengths generated from the inside of the furnace, it is possible to reduce the influence of the ghost light. The emitting device 14 can emit not only continuous light but also pulsed laser light.

When an image sensor such as a CCD sensor is used as the sensor 19 of the light receiving device 15, the relative light receiving sensitivity can be improved.
As an alternative to the laser light source, a general light source such as xenon, mercury or halogen or a single wavelength light source such as sodium ray can be used.

The movable mirror 16 and the prism mirror 17 are mirrors that guide the laser beam L1 emitted from the emitting device 14 to the liquid level MA and guide the laser beam L2 reflected by the liquid level MA to the light receiving device 15.
The movable mirror 16 is a mirror that is arranged outside the chamber 2 and can be rotated and moved up and down.
The angle of the optical path of the laser beam L can be changed by rotating the movable mirror 16 around the axis 16A extending in the horizontal direction along the reflection surface 16B (arrow R in FIG. 1).

FIG. 3 is a diagram illustrating raising and lowering (movement in the vertical direction) of the movable mirror 16. As shown in FIG. 3, by moving the movable mirror 16 upward (arrow U in FIG. 3), the optical path of the laser beam L can be moved outward in the radial direction of the silicon single crystal S (before the movement). The optical path is indicated by a solid line, and the optical path after movement is indicated by a two-point chain line.)
The movable mirror 16 of the present embodiment is configured to be rotatable and ascending / descending, but the present invention is not limited to this as long as the optical path can be adjusted, and other mechanisms may be used. Further, if it is not necessary to move the optical path, a fixed mirror may be adopted.

The prism mirror 17 is arranged in the chamber 2 and reflects the laser beam L1 incident from the window portion 2A toward the liquid surface MA, and the laser beam L2 reflected from the liquid surface MA is reflected through the window portion 2A in the furnace. It is a mirror that leads to the outside.

In the liquid level morphology determination device 12, after the laser beam L1 emitted from the exit device 14 is reflected by the movable mirror 16 and the prism mirror 17 and irradiated to the liquid level MA, the reflected light is reflected by the prism mirror 17 and the movable mirror 16. It is configured to be reflected and received by the sensor 19 of the light receiving device 15.
Specifically, in each component of the liquid level morphology determining device 12, when the liquid level MA of the silicon melt M is substantially flat, the laser beam L emitted from the emitting device 14 is received by the light receiving device 15. The position is adjusted so as to be. When each component of the liquid level morphological determination device 12 is adjusted in this way, if the liquid level MA of the silicon melt M is not substantially flat, the direction of the reflected light of the laser light L changes and the light is received. The device 15 does not receive the laser beam L. The non-planar form includes, for example, a form in which undulations occur like a wave, and a form in which a meniscus Me formed at the interface between the edge of the silicon single crystal S and the liquid surface MA is generated.

The meniscus Me is a curved liquid surface form generated by surface tension at the interface between the edge of the silicon single crystal S and the silicon melt M.
Further, when the inclination of the liquid level MA of the silicon melt M is not a normal inclination, for example, when the liquid level MA of the silicon melt M is usually horizontal and normal, the liquid level MA is an inclined surface. Even in the case of, the direction of the reflected light of the laser beam L changes and the light receiving device 15 does not receive the laser beam L.

As shown in FIG. 1, the control device 20 includes a device control unit 21 that controls an exit device 14, a movable mirror 16, and the like, and a determination unit 22.
The device control unit 21 has a function of controlling the emitting device 14 so as to emit the pulsed laser beam L a predetermined number of times per unit time (for example, 1000 pulses / second).
The determination unit 22 is electrically connected to the light receiving device 15, and has, for example, a function of monitoring the amount of light received by the light receiving device 15 for receiving the laser beam L (reflected light) per unit time.
The above is the case where the pulsed laser beam L is used, but the continuous light laser beam L may be used. Further, when the continuous light laser beam L is used, a shutter (for example, 1000 times of opening / closing / second) that opens / closes at high speed is installed in the emitting device 14 or the light receiving device 15, and the laser light received by the light receiving device 15 L may be apparently pulsed.

The determination unit 22 has a function of determining whether or not the form of the liquid level MA of the silicon melt M is normal based on the decrease in the amount of received light received per unit time of the monitored laser beam L. When the received light amount becomes lower than the set threshold value (for example, 20% of the emitted amount of the laser light), the determination unit 22 determines that the form of the liquid level MA of the silicon melt M is not normal, and displays the display device. For example, character information such as "reduced light reception amount" is displayed on the 23, and an alarm is issued to the operator.
The threshold value of the received light amount is set based on the emitted amount of the laser light and is always set to a value smaller than the emitted amount of the laser light, but the light received by the light receiving device 15 includes noise. Therefore, it is not preferable to set the threshold value to 0% of the amount of emitted laser light.

On the other hand, when the pulsed laser beam L or the apparent pulsed laser beam L is used, the light receiving frequency (the number of pulse counts) of the received laser light L per unit time may be used as the light receiving amount.
For example, when a pulsed laser beam L having an emission frequency of 1000 pulses / sec is used, it can be set to display "reduced light receiving amount" when the light receiving frequency is lower than 200 times / sec.

The liquid level morphology determining device 12 of the present embodiment is configured to detect the meniscus Me generated at the interface between the edge of the silicon single crystal S and the silicon melt M. Specifically, the liquid level morphology determining device 12 emitted from the emitting device 14 so as to detect the meniscus Me when the diameter of the silicon single crystal S becomes larger than the set value set by the operator. The position where the laser beam L is applied to the liquid surface MA of the silicon melt M is adjusted.
That is, the liquid level morphology determination device 12 of the present embodiment utilizes the fact that the amount of light received by the laser beam L decreases as the laser beam L irradiates the curved meniscus Me, so that the diameter of the silicon single crystal S is reduced. To monitor.

As shown in FIG. 4, the operator is the outside of the silicon single crystal S having a desired diameter in the radial direction, and the distance from the outer peripheral surface of the silicon single crystal S having a desired diameter is, for example, 10 mm. The movable mirror 16 is adjusted so that the laser beam L is irradiated at the position of.
The pulling device 1 of the present embodiment is adjusted so that the diameter of the silicon single crystal S is 300 mm (radius 150 mm). Correspondingly, the position of the liquid level morphological determination device 12 is adjusted so that the laser beam L is reflected on the liquid level MA 160 mm away from the central axis A of the silicon single crystal S. The diameter of the silicon single crystal S is not limited to 300 mm, and the setting can be changed as appropriate.

When the pulling device 1 and the liquid level morphology determining device 12 are set in this way, as shown in FIG. 4, when the diameter of the silicon single crystal S is correctly 300 mm, the laser beam L emitted from the emitting device 14 is emitted. , It is reflected by the liquid surface MA which is substantially flat, and is received by the light receiving device 15. That is, the laser beam L is reflected by the flat liquid surface MA without being affected by the meniscus Me. The radial width of the meniscus Me is 5 mm.

On the other hand, when the diameter of the silicon single crystal S fluctuates during pulling for some reason and becomes larger than 310 mm (the diameter of the silicon single crystal S increases by 10 mm), as shown in FIG. 5, the silicon single crystal S of the silicon single crystal S The meniscus Me generated at the interface between the edge and the silicon melt M moves radially outward, and the laser beam L interferes with the meniscus Me.
As a result, the laser beam L is reflected in a direction different from the normal direction, is not received by the light receiving device 15, and the amount of received laser light L monitored by the determination unit 22 is reduced.

Next, a specific method for growing the silicon single crystal S will be described.
To pull up the silicon single crystal S by the CZ method, the silicon put into the crucible 3 is heated to a melted state, the seed crystal SC is implanted in the silicon melt M, and the seed crystal SC is raised by the pulling shaft 7. It is done by pulling up to.

As shown in FIG. 6, the single crystal growing method of the present embodiment includes an irradiation and receiving step S1 for irradiating and receiving the laser beam L, a determination step S2 for determining the form of the liquid level MA, and a display step S3. Have.

In the irradiation / light receiving step S1, the laser beam L emitted from the emitting device 14 is irradiated to the liquid level MA of the silicon melt M through the mirrors 16 and 17 a predetermined number of times per unit time, and is reflected by the liquid level MA. This is a process of receiving reflected light.
The determination step S2 is a step of determining the form of the silicon melt M based on the amount of light received per unit time in the irradiation / light receiving step S1.
In the display step S3, when the light receiving amount becomes lower than the set threshold value, the determination unit 22 displays “reduced light receiving amount” on the display device 23. Since the liquid level morphology determination device 12 of the present embodiment is configured to detect the meniscus Me generated at the interface between the edge of the silicon single crystal S and the silicon melt M, the operator can perform the silicon single crystal S. It can be seen that the diameter of is larger than the desired diameter.

FIG. 7 is a graph showing the relationship between the diameter of the silicon single crystal S measured by an optical diameter measuring device (not shown) and the light receiving frequency (light receiving amount) of the laser beam L. In FIG. 7, the horizontal axis is a relative value with respect to the set value (for example, 310 mm) of the diameter of the silicon single crystal S, and the vertical axis is the number of times of light reception by the light receiving device 15. The laser beam L is in the form of a pulse of 1000 pulses / second, and the number of times of light reception is the number of times that the light receiving device 15 receives the laser light L in 5 seconds. Therefore, the number of emissions for 5 seconds is 5000 pulses.

As can be seen from FIG. 7, when the diameter of the silicon single crystal S is smaller than the set value (310 mm), the light receiving frequency is high, the number of times of light reception is 1000 times or less before and after the set value, and the light receiving frequency is 20% or less. You can see that it is. From this result, it can be seen that it can be determined that the diameter of the silicon single crystal S exceeds a predetermined value by using the liquid level morphology determination device 12.

According to the above embodiment, the diameter of the silicon single crystal S is determined by determining that the liquid level MA of the silicon melt M is not substantially planar by using the liquid level morphology determination device 12. It can be determined that the value of is exceeded.
Further, by using the amount of received light as a determination material, it is possible to immediately grasp the increase in the diameter of the silicon single crystal S.

Further, by adopting a movable mirror 16 and a prism mirror 17 that can be raised and lowered as mirrors that guide the laser beam L into the chamber 2, the radial position of the optical path of the laser beam L can be freely adjusted. As a result, the liquid level morphological determination device 12 corresponding to the silicon single crystal S having various diameters can be obtained.

[Another Embodiment]
In the above embodiment, the liquid level morphology determination device 12 is used to monitor the diameter of the silicon single crystal S, but the present invention is not limited to this. For example, the liquid level morphology determination device 12 may be used to monitor the fluctuation of the liquid level MA due to the rotation of the crucible 3.
With such a configuration, it is possible to immediately grasp the rotation failure of the crucible 3.

The present invention is not limited to the above embodiment, and various improvements and design changes can be made without departing from the gist of the present invention.
For example, in the above embodiment, the silicon single crystal S is produced by using the pulling device 1, but the present invention is not limited to this. For example, a germanium single crystal may be produced by accommodating a germanium melt in a crucible.

1 ... Lifting device, 2 ... Chamber, 3 ... Rutsubo, 4 ... Heater, 5 ... Support shaft, 6 ... Insulation material, 7 ... Pulling shaft, 8 ... Heat shield, 10 ... Gas inlet, 11 ... Exhaust port, 12 ... Liquid level morphology determination device, 13 ... Emission light receiving unit, 14 ... Emission device (light source), 15 ... Light receiving device, 16 ... Movable mirror, 17 ... Prism mirror, 18 ... Lens, 19 ... Sensor, 20 ... Control device, 21 ... Device control unit, 22 ... Monitoring unit, 23 ... Display device, A ... Central axis, L ... Laser light, M ... Silicon melt, MA ... Liquid level, Me ... Meniscus, S ... Silicon single crystal, SC ... Seed crystal ..

Claims (6)

It is a single crystal growth method that grows a single crystal by the Czochralski method.
An irradiation / light receiving step of irradiating the liquid surface of the raw material melt contained in the rutsubo from above with the emitted light emitted from the light source and receiving the reflected light reflected by the liquid surface of the raw material melt.
A method for growing a single crystal, which comprises a determination step of determining whether or not the morphology of the liquid surface of the raw material melt is normal based on the amount of light received per unit time in the irradiation / light receiving step. The single crystal growth according to claim 1, wherein in the determination step, when the amount of light received per unit time becomes lower than the threshold value, it is determined that the morphology of the liquid surface of the raw material melt is not normal. Method. In the irradiation / reception step, when the diameter of the single crystal is increased, the emitted light emitted from the light source is said to detect the meniscus generated at the interface between the edge of the single crystal and the raw material melt. The single crystal growing method according to claim 1 or 2, wherein the position of being irradiated on the liquid surface of the raw material melt is adjusted. It is a single crystal growth device that grows a single crystal by the Czochralski method.
A crucible containing the raw material melt and
A light source that emits light emitted from above to the liquid surface of the raw material melt,
A light receiving portion that receives the reflected light reflected by the liquid surface of the raw material melt, and a light receiving portion.
A single crystal growing apparatus comprising: a determination unit for determining whether or not the morphology of the liquid surface of the raw material melt is normal based on the amount of light received per unit time in the light receiving unit. It is arranged outside the chamber, can move in the vertical direction, reflects the emitted light emitted downward from the light source and guides it into the chamber through the window portion, and reflects the reflected light to the light receiving portion. Movable mirror to guide and
A prism arranged in the chamber and guided into the chamber by the movable mirror to reflect the emitted light toward the liquid surface and to reflect the reflected light and guide the reflected light to the outside of the chamber through the window portion. The single crystal growing apparatus according to claim 4, further comprising a mirror. The position of the movable mirror is adjusted so that the emitted light detects the meniscus generated at the interface between the edge of the single crystal and the raw material melt when the diameter of the single crystal is increased. The single crystal growing apparatus according to claim 5.

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