JP7272249B2 - Single crystal growth method and single crystal growth apparatus - Google Patents

Description

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

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

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

JP-A-9-278586

By the way, although the apparatus described in Patent Document 1 can detect an abnormality in the level of the silicon melt, normal measurement cannot be performed when some abnormality occurs in the shape of the liquid surface of the silicon melt. become unable. Therefore, a system capable of detecting an abnormality in the liquid surface is desired.

INDUSTRIAL APPLICABILITY The present invention provides a single crystal growing method and a single crystal growing method that can immediately determine whether or not the liquid surface of a raw material melt contained in a crucible is normal when growing a single crystal by the Czochralski method. The purpose is to provide an apparatus.

The single crystal growth method of the present invention is a single crystal growth method for growing a single crystal by the Czochralski method, in which light emitted from a light source is directed from above toward the liquid surface of a raw material melt contained in a crucible. and receiving the reflected light reflected by the liquid surface of the raw material melt, and based on the amount of light received per unit time in the irradiation and light receiving step, the shape of the liquid surface of the raw material melt is determined. and a determination step of determining whether or not the system is normal.

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

In the irradiation and light receiving step, when the diameter of the single crystal increases, the emitted light emitted from the light source is used to detect a meniscus generated at the interface between the edge of the single crystal and the raw material melt. A configuration may be adopted in which the position where the liquid surface of the raw material melt is irradiated is adjusted.
The meniscus is a curved liquid surface formed by surface tension at the interface between the edge of the single crystal and the raw material melt.

A single crystal growth apparatus of the present invention is a single crystal growth apparatus for growing a single crystal by the Czochralski method. The shape of the liquid surface of the raw material melt is determined based on the light source that emits incident light, the light receiving section that receives the reflected light reflected by the liquid surface of the raw material melt, and the amount of light received by the light receiving section per unit time. and a judgment unit for judging whether or not is normal.

In the single crystal growth apparatus described above, the single crystal growth apparatus is arranged outside the chamber, is movable in the vertical direction, reflects light emitted downward from the light source, guides it into the chamber through the window, and directs the reflected light to the chamber. a movable mirror that reflects and guides the light to the light receiving part; and a prism mirror leading out of the chamber through the window.

In the above single crystal growth apparatus, the emitted light is directed to the movable mirror so as to detect a meniscus generated at the interface between the edge of the single crystal and the raw material melt when the diameter of the single crystal increases. It is also possible to adopt a configuration in which the positions of are adjusted.

According to the present invention, it is possible to immediately grasp the state of the liquid surface of the raw material melt by determining whether or not the shape of the liquid surface of the raw material melt is normal based on the amount of light received.

It is a schematic sectional drawing of the pulling-up apparatus of embodiment of this invention. 1. It is the schematic which looked at the liquid surface form determination apparatus of embodiment of this invention from the direction different from FIG. It is a figure explaining the up-and-down movement of a movable mirror. It is a schematic diagram explaining the positional relationship between a silicon single crystal and a laser beam. FIG. 4 is a schematic diagram for explaining how a laser beam and a meniscus interfere with each other due to an increase in the diameter of a silicon single crystal; 1 is a flow chart of a single crystal growth method according to an embodiment of the present invention; 4 is a graph showing the relationship between the diameter of a silicon single crystal and the frequency of light reception;

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
[Lifting device]
FIG. 1 is a schematic cross-sectional view of a lifting device 1 according to an embodiment of the invention. FIG. 2 is a schematic view of the liquid level determination device 12 provided in the lifting device 1, viewed from a direction different from that of FIG. In order to facilitate understanding of the structure, the drawing shows X, Y and Z axes that are orthogonal to each other (the same applies to other drawings). The X and Y axes correspond to the horizontal direction and the Z axis corresponds to the vertical direction.
1 is a view of the trajectory of the laser beam L of the liquid surface configuration determination device 12 viewed from the side (in the direction along the Y axis), and FIG. It is a diagram viewed from the direction along the line). 1, the laser beam L is guided by the movable mirror 16 and the prism mirror 17, but the movable mirror 16 and the prism mirror 17 are omitted in FIG.

A pulling apparatus 1 is an apparatus 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 forming an outer shell, a crucible 3 arranged in the center of the chamber 2, a heater 4, and a liquid surface shape determining device 12. .

The crucible 3 has a circular shape when viewed from above in the vertical direction, and is a container in which the silicon melt M (raw material melt) is stored. 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 outside the crucible 3 . The heater 4 is a resistance heating type so-called carbon heater. A heat insulator 6 is provided outside the heater 4 along the inner surface of the chamber 2 .

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

A thermal shield 8 is arranged in the chamber 2 . The heat shield 8 has a substantially conical tubular 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 to the silicon single crystal S being grown. 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 direction of the pulling axis at the central part of the single crystal and the outer peripheral part of the single crystal. play a role.

A gas introduction port 10 is provided in the upper portion of the chamber 2 . A gas inlet 10 introduces an inert gas G such as argon gas into the chamber 2 . An exhaust port 11 is provided at the bottom 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 through the gas inlet 10 descends between the silicon single crystal S being grown and the thermal 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 outside the heat shield 8 and further outside the crucible 3 . After that, the inert gas G descends outside the crucible 3 and is discharged from the exhaust port 11 .

[Liquid level determination device]
The liquid surface configuration determination device 12 is a device that determines the configuration of the liquid surface MA of the silicon melt M. As shown in FIG. Specifically, the liquid surface configuration determination device 12 is a device capable of determining that the configuration of the liquid surface MA is not normal, such as a configuration in which the liquid surface MA is undulating like waves. is.
The liquid surface form determination device 12 of the present invention reflects the light emitted from the light source on the liquid surface MA, and determines whether or not the form of the liquid surface MA is normal based on whether or not the reflected light can be received by the light receiving device. judge.
Here, the state that the shape of the liquid surface MA of the silicon melt M is not normal means that there is some abnormality in the growth of the single crystal, and the shape of the liquid surface MA that is not observed when the single crystal is normally grown. say that For example, there is a form in which undulations such as waves are generated on the liquid surface MA. In addition, as another abnormal example, there is some abnormality in the growth of the single crystal, and the liquid surface MA is curved or the liquid surface MA is inclined, which is not observed when the single crystal is grown normally. A form such as a form in which the In addition, as a specific example of some kind of abnormality in the growth of a single crystal, the crystal diameter deviates from the set value due to equipment failure and the crystal diameter increases, and the crucible rotation speed deviates from the set value and the crucible rotates. The crucible may be rotated due to axial runout. In addition, there are cases where the setting value of the crystal diameter or the setting value of the crucible rotation speed set by the operator is incorrect due to human error. A case in which the melt in the crucible shakes greatly may also be mentioned.

As shown in FIGS. 1 and 2, the liquid surface configuration determination device 12 has an emission/reception unit 13, a movable mirror 16, a prism mirror 17, a control device 20, and a display device . In FIG. 2, the incident angle .theta.1 and the reflection angle .theta.2 of the laser beam L on the liquid surface MA are shown enlarged, and actually the angles .theta.1 and .theta.2 are small angles of 5 degrees or less. In other words, the laser beam L is applied vertically or substantially vertically from above to the liquid surface MA.

The emitting/receiving unit 13 is arranged outside the chamber 2 and is a unit that emits and receives the laser light L. As shown in FIG. The emission/reception unit 13 has an emission device 14 that emits the laser light L1 (emission light) and a light reception device 15 (light reception section) that receives the laser light L2 (reflection light).
The light receiving device 15 has a lens 18 that collects the incident laser beam L2 and a sensor 19 that detects the collected laser beam L2.

The emission device 14 is, for example, a device using a laser light source with a wavelength of 400 nm to 550 nm as a light source. In this way, by using a laser light source whose wavelengths are significantly different from those of yellow, red, and near-infrared ghost light emitted from the furnace, it is possible to reduce the influence of ghost light. The emission device 14 can emit not only continuous light but also pulsed laser light.

When an imaging element 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 line 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 surface MA and guide the laser beam L2 reflected by the liquid surface MA to the light receiving device 15 .
The movable mirror 16 is arranged outside the chamber 2 and is a mirror that can rotate and move up and down.
The angle of the optical path of the laser light L can be changed by rotating the movable mirror 16 about the axis 16A extending horizontally along the reflecting surface 16B (arrow R in FIG. 1).

3A and 3B are diagrams for explaining the elevation (vertical movement) of the movable mirror 16. FIG. 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 movement). The optical path is indicated by a solid line, and the optical path after movement is indicated by a two-dot chain line.).
Although the movable mirror 16 of this embodiment is configured to be able to rotate and move up and down, other mechanisms may be used as long as the optical path can be adjusted. Also, if there is no need to move the optical path, a fixed mirror may be employed.

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

In the liquid surface form determination device 12, the laser light L1 emitted from the emission device 14 is reflected by the movable mirror 16 and the prism mirror 17, and the liquid surface MA is irradiated with the reflected light. It is configured to be reflected and received by the sensor 19 of the light receiving device 15 .
Specifically, each component of the liquid surface configuration determining device 12 receives the laser light L emitted from the emitting device 14 by the light receiving device 15 when the liquid surface MA of the silicon melt M is substantially flat. are positioned so that When each component of the liquid surface configuration determination device 12 is adjusted in this way, when the liquid surface MA of the silicon melt M is not substantially planar, 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 light L. The non-substantially planar shape includes, for example, a wave-like undulating shape and a meniscus Me formed at the interface between the edge of the silicon single crystal S and the liquid surface MA.

The meniscus Me is a curved liquid surface formed by surface tension at the interface between the edge of the silicon single crystal S and the silicon melt M. As shown in FIG.
Further, when the inclination of the liquid surface MA of the silicon melt M is not a normal inclination, for example, when the liquid surface MA of the silicon melt M is normal and normal, the liquid surface MA is an inclined surface. , the direction of the reflected light of the laser light L is changed and the light receiving device 15 does not receive the laser light L. FIG.

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

The judging section 22 has a function of judging whether or not the form of the liquid surface MA of the silicon melt M is normal based on the decrease in the amount of light received per unit time of the laser beam L monitored. When the amount of received light is lower than a set threshold value (for example, 20% of the amount of emitted laser light), the determination unit 22 determines that the shape of the liquid surface MA of the silicon melt M is not normal. 23, for example, character information such as "receiving amount decreased" is displayed to warn the operator.
Note that the threshold for the amount of received light is set based on the amount of emitted laser light, and is always set to a value smaller than the emitted amount of laser light. However, the light received by the light receiving device 15 includes noise. Therefore, it is not preferable to set the threshold to 0% of the emitted amount of laser light.

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

The liquid surface configuration determination device 12 of this 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. As shown in FIG. Specifically, when the diameter of the silicon single crystal S becomes larger than the set value set by the operator, the liquid surface configuration determination device 12 emits from the emission device 14 so as to detect the meniscus Me. The position at which the liquid surface MA of the silicon melt M is irradiated with the laser light L is adjusted.
That is, the liquid surface shape determining apparatus 12 of the present embodiment utilizes the decrease in the amount of received laser light L due to the irradiation of the curved meniscus Me with the laser light L, so that the diameter of the silicon single crystal S to monitor.

As shown in FIG. 4, the operator sets the distance between the silicon single crystal S having the desired diameter in the radial direction and the outer peripheral surface of the silicon single crystal S having the desired diameter by, for example, 10 mm. The movable mirror 16 is adjusted so that the laser beam L is irradiated at the position of .
The pulling apparatus 1 of this 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 surface configuration determination device 12 is adjusted so that the laser light L is reflected on the liquid surface 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 can be appropriately changed.

When the pulling device 1 and the liquid level determination device 12 are set in this way, as shown in FIG. , is reflected by the substantially planar liquid surface MA, and is received by the light receiving device 15 . That is, the laser beam L is reflected by the planar liquid surface MA without being affected by the meniscus Me. The radial width of the meniscus Me is 5 mm.

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

Next, a specific method for growing the silicon single crystal S will be described.
The pulling of the silicon single crystal S by the CZ method involves heating the silicon charged into the crucible 3 to a molten state, implanting the seed crystal SC in the silicon melt M, and lifting the seed crystal SC upward by the pulling shaft 7 . This is done by raising the

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

In the irradiation and light receiving step S1, the laser beam L emitted from the emitting device 14 is irradiated to the liquid surface MA of the silicon melt M through the mirrors 16 and 17 a predetermined number of times per unit time, and the laser beam L is reflected by the liquid surface MA. This is the step of receiving reflected light.
The determining 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/receiving step S1.
In the display step S3, the determination unit 22 displays "decrease in the amount of received light" on the display device 23 when the amount of received light becomes lower than the set threshold value. Since the liquid surface configuration 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 detect the silicon single crystal S 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 frequency of receiving the laser beam L (the amount of received light). In FIG. 7, the horizontal axis represents the relative value of the diameter of the silicon single crystal S (for example, 310 mm), and the vertical axis represents the number of times the light receiving device 15 receives light. The laser light L has a pulse shape of 1000 pulses/second, and the number of times of light reception is the number of times the light receiving device 15 receives the laser light L in 5 seconds. Therefore, the number of times of emission 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 frequency of light reception is high, the frequency of light reception is 1000 times or less before and after the set value, and the frequency of light reception is 20% or less. I know it's happening. From this result, it can be seen that it is possible to determine that the diameter of the silicon single crystal S has exceeded a predetermined value using the liquid level determination device 12 .

According to the above-described embodiment, by using the liquid level determination device 12 to determine that the liquid surface MA of the silicon melt M is not substantially planar, the diameter of the silicon single crystal S is determined to be a predetermined value. It can be determined that the value of
Further, by using the amount of light received as a criterion for determination, an increase in the diameter of the silicon single crystal S can be immediately grasped.

Further, by adopting the vertically movable mirror 16 and the prism mirror 17 as mirrors for guiding the laser light L into the chamber 2, the radial position of the optical path of the laser light L can be freely adjusted. As a result, the liquid surface configuration determination device 12 can be adapted to handle silicon single crystals S having various diameters.

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

The present invention is not limited to the above-described embodiments, and various improvements and design changes are possible without departing from the scope of the present invention.
For example, in the above embodiment, the silicon single crystal S was manufactured using the pulling apparatus 1, but the present invention is not limited to this. For example, a germanium single crystal may be produced by placing a germanium melt in a crucible.

DESCRIPTION OF SYMBOLS 1... Lifting device, 2... Chamber, 3... Crucible, 4... Heater, 5... Support shaft, 6... Heat insulating material, 7... Lifting shaft, 8... Thermal shield, 10... Gas inlet, 11... Exhaust port, 12 Liquid surface configuration determination device 13 Output/receiving unit 14 Output 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 beam M Silicon melt MA Liquid surface Me Meniscus S Silicon single crystal SC Seed crystal .

Claims (8)

A single crystal growing method for growing a single crystal by the Czochralski method,
an irradiation/receiving step of irradiating a laser beam emitted from a light source from above onto the liquid surface of the raw material melt contained in the crucible, and receiving the laser beam reflected by the liquid surface of the raw material melt in a pulsed form ;
a determination step of determining whether or not the surface of the raw material melt is normal based on the amount of the laser light received per unit time in the irradiation and light receiving step. Single crystal growth method. 2. The method of growing a single crystal according to claim 1, wherein the amount of light received is the frequency of light received per unit time of the pulsed laser light. 2. In the determining step, it is determined that the liquid surface of the raw material melt is not normal when the amount of received laser light per unit time is lower than a threshold value. Item 3. The method for growing a single crystal according to item 2 . In the irradiation and light receiving step, when the diameter of the single crystal increases, the laser light emitted from the light source is used to detect a meniscus generated at the interface between the edge of the single crystal and the raw material melt. 4. The method for growing a single crystal according to any one of claims 1 to 3, wherein the position of irradiation on the liquid surface of the raw material melt is adjusted. A single crystal growth apparatus for growing a single crystal by the Czochralski method,
a crucible containing the raw material melt;
a light source that emits a laser beam from above toward the liquid surface of the raw material melt;
a light-receiving unit that receives a pulsed laser beam reflected by the surface of the raw material melt;
a determination unit that determines whether or not the liquid surface of the raw material melt is normal based on the amount of the laser light received by the light receiving unit per unit time. Crystal growing device. The pulsed laser light received by the light-receiving unit is pulsed laser light emitted from the light source, or pulsed continuous laser light emitted from the light source by a shutter. The single crystal growth apparatus according to claim 5, characterized in that: The laser light emitted downward from the light source is reflected and guided into the chamber through a window portion, and the laser light is reflected to the light receiving portion. A movable mirror that guides,
a prism arranged in the chamber for reflecting the laser light guided into the chamber by the movable mirror toward the liquid surface, reflecting the laser light, and guiding the laser light out of the chamber through the window; 7. The single crystal growth apparatus according to claim 5, further comprising a mirror. The position of the movable mirror is adjusted so that the laser beam detects a meniscus generated at the interface between the edge of the single crystal and the raw material melt when the diameter of the single crystal increases. The single crystal growth apparatus according to claim 7 , characterized in that:

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