JPH01212291A - Method and apparatus for growing crystal - Google Patents

Abstract

PURPOSE:To enable the control of a crystal growth speed (change in a growth boundary face position) and growth boundary face shape which are heretofore not controllable by executing computation and processing in accordance with the information on the temps. at plural points on the outside circumference of a crucible in crystal growth by a perpendicular Bridgman method. CONSTITUTION:The following constitution is adopted in the crystal growth method of growing the crystal 2 of the shape defined by the crucible 5 having a cylindrical shape or various shapes by starting the crystal growth from one end of the crucible 5 from the raw material melt or soln. prepd. by melting or synthesizing in the above- mentioned melt and gradually progressing the crystal growth in nearly the specified direction: The temps. at the specific plural points on the outside circumference of the crucible 5 are detected (thermocouples 111-115) and the temp. distribution in the crucible 5, the position of the growth boundary face and the position thereof are calculated and estimated (15, 16, 17) at every specified time in accordance with the temps. at the plural points. Both of the change in the growth boundary face position (growth speed) or the change in the growth boundary face shape or growth boundary face position and the growth boundary face shape are controlled (comparator 18, controller 19) in accordance with the results of such calculation and estimation.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a technique for growing single crystals of metals, semiconductors, oxides, etc. A raw material melt, known under names such as the vertical Bridgman method, is prepared in a so-called crucible, which is basically a container made of an immovable material, and then the melt is used to seed crystals. The growth of a single crystal with a specific orientation is started using a special method or by a special method, and the crystal shape is gradually solidified from the bottom to the top K (or from the top to the bottom) of the crucible. A crystal growth method and its growth equipment for growing a single crystal under specified conditions f! It is related to.

Hereinafter, the present invention will be described in detail using an example in which a caAm single crystal, which is one of the typical compound semiconductors, is grown by the liquid-sealed vertical Bridgman method (or the liquid-sealed vertical temperature gradient solidification method).

[Conventional technology]

Figure 3 shows GaAa obtained by the liquid-sealed vertical replacement Tudjiman method.
FIG. 2 is a schematic diagram showing the inside of a furnace showing single crystal growth and the concept of crystal growth control. In the same figure, 1 is a seed crystal, 2
3 is a grown GaAm crystal, 3 is a Ga melt, 4 is a liquid sealant, 5 is a crucible having a circular cross-sectional shape, 6 is a crucible holder, 7 is a crucible shaft that supports this holder 6,
8 is a crucible drive mechanism for rotating and vertically moving the crucible 5 via this shaft 7; 9s + 9z +
9s and 94 are heating elements that can be controlled independently, 10 is an airtight container, and 21 is a control device for changing the electric power of the heating elements 91-94 and the position of the crucible 50 rotations.

In such an apparatus configuration, in conventional crystal growth, seed crystals 1. GaAs polycrystal as a raw material, liquid sealant 4 in a solid state, etc. are filled, and then heated to a high temperature using a heating element 91 to 94 to soften the sealant 4.
After melting the K material GaA@, single crystal growth is started by seeding, and the growth interface 12 is gradually moved upward,
A crystal growth state as shown in FIG. 3 is realized.

[Problem to be solved by the invention]

A major problem in controlling growth in the crystal growth method described above is that it is extremely difficult to control the growth rate of the crystal, the movement speed of the growth interface 12 position, and the shape of the growth interface cannot be detected. .

Liquid encapsulation pulling (LE) is currently in practical use as a manufacturing method for compound semiconductor crystals including GaAs crystals.
In the case of crystal growth using the C) method or the horizontal Bridgman (HB) method, an observation window is provided in the airtight container or furnace body.
Observe the growth status or detect the weight of the growing crystal (in the case of the LEC method), and based on this information, adjust the temperature conditions in the furnace (mainly temperature distribution) by changing the power of the heating element or the crucible. A desired crystal growth rate is achieved by controlling the position (board position in the case of the HB method) using K. On the other hand, in the case of crystal growth such as the above-mentioned vertical Bridgman method according to the present invention, it is impossible in principle to observe the position and shape of the growth interface, as well as to measure the weight of the grown crystal part. However, precise control of growth rate and interface shape was not performed. That is, in the conventional method, for example, as schematically shown in FIG. , the temperature distribution changes from p to P! as the crystal growth progresses. , the growth interface changes from 121 to 1 in response to the change in the melting point (Tm) position.
It was only assumed that the crystals had moved to the snow (crystals had grown). In this case, the average crystal growth rate is only estimated from the time when the temperature distribution moves from PI to pg and the distance between the growth interface 121 and the growth interface 12. It was also not enough to know the growth rate. Furthermore, the shape of the growth interface was only estimated from observations of growth striations that appear inside the crystal after crystal growth.

By the way, the crystal growth rate has a significant effect on crystal properties such as the segregation of impurities at the growth interface, the shape of the growth interface, and the thermal history of the crystal part after growth. Required. In addition, the shape of the growth interface during crystal growth is an important factor in growing the entire crystal as a single crystal, and is also known to be a factor that affects crystal quality, such as the occurrence of defects in the grown crystal part. ing.

However, the above-mentioned conventional method has a serious drawback in that the position and shape of the growth interface cannot be accurately measured and therefore cannot be controlled.

In view of the above points, the present invention has been made to solve the drawbacks of the prior art.The purpose of the present invention is to solve the problems of the prior art. It was difficult to control it. It is an object of the present invention to provide a crystal growth method and a growth apparatus that enable control of the crystal growth rate (change in the growth interface position) and the growth interface shape.

[Means to solve the problem]

In order to achieve the above object, the present invention detects the temperature of a plurality of specific tubes and places around the crucible, and based on the temperature information of the plurality of places, the temperature distribution inside the crucible and the growth interface are determined at regular intervals. The position and shape of the growth interface are calculated and estimated, and based on the calculation results, the change in the growth interface position (growth rate) or the growth interface shape, or both the change in the growth interface position and the growth interface shape are controlled. This is what I did.

[Effect]

Therefore, in the present invention, it is possible to control the growth rate of the crystal growth interface position and the interface shape with a predetermined precision.

〔Example〕

Next, before describing embodiments, an overview of the present invention will be explained with reference to FIG. 1.

FIG. 1 is a conceptual diagram illustrating the present invention in detail.

In the same figure, 111.11, 1h, 114 and 11
g indicates five pairs of thermocouples for detecting temperatures at specific locations on the outer periphery of the crucible according to the present invention.

Here, the number and position of the thermocouples to be installed vary depending on the type, size, and shape of the crystal to be grown, as well as the required crystal growth rate and control precision of the interface shape. Regarding the number of thermocouples, in principle, it is sufficient to have two or more pairs (plurality), but in the case of crystal growth having the shape shown in FIG. 1, it is preferable to install three or more pairs. Furthermore, in the case of crystals with complex shapes and large sizes (large diameter and long length),
It is preferable to install 4 pairs or 5 pairs or more. It has been found that the greater the number of thermocouples, the more accurate the calculation of the temperature distribution inside the crucible, which will be described later, can be improved, and as a result, it is effective in improving the control precision of the desired growth rate and interface shape. There is.

The installation location of thermocouples is determined empirically, taking into consideration the number of thermocouples used, crystal shape, etc.

Generally, good results have been obtained by placing the crystal near the area where the crystal shape changes, as shown in FIG.

In addition, it is preferable to install the thermocouple as close to the crucible 5 as possible, but the reproducibility of the installation position for each crystal growth, the time of assembling the furnace body configuration (hot zone), the time of charging raw materials, etc. It may be installed at an appropriate position inside the crucible holder, taking into account the nature of the crucible. Another requirement regarding the installation of these thermocouples is that the plurality of installed thermocouples 111 to 1 is all made of GaAs fusion.

The structure is such that it can be rotated or moved up and down while maintaining a constant relative position to the crucible 5 containing the liquid 3 or the GaAs crystal 2. That is, the output connection lines of these thermocouples 111 to 11s are connected from the lower part of the crucible holder 6 to the crucible shaft 7, and are connected to the crucible shaft 7 of the airtight container 1.
0 and connected to the temperature needle R14 via a mechanism such as a slip ring 13. Next, the temperature distribution calculation means 15 calculates, in addition to the temperature data at each thermocouple installation position measured by the temperature measurement means 14, the structure of the crucible 5, the shape of the substance in the crucible, and the heat Based on information such as physical physical constants, the shape of the crucible holder 6, and thermal physical constants, the temperature distribution inside the crucible is calculated at regular time intervals using a predetermined method, and the t-signal of this information is also calculated. It has the function of outputting as . Furthermore, the temperature distribution display means 16 displays the temperature distribution inside the horn using image processing means such as isotherms based on the calculation results of the temperature distribution calculation means 15, and also displays the temperature distribution of the material (GaAs) to be grown. It has the function of displaying the position and shape of the growth interface based on information regarding the melting point, etc., and outputting this information as an electrical signal.

On the other hand, the program signal output means 1T outputs, over time, a program qgram signal of the growth interface position and shape, which is performed by assuming a desired growth interface movement speed in advance, as well as the growth interface movement speed and the growth interface shape. It has the means to do so. A part of the output signal is transmitted to the temperature distribution display means 16 and processed for displaying the program status, and the other part is transmitted to the comparator 18. This comparator 18 has a function of comparing the output signal of the temperature distribution calculation means 15 and the output signal of the program signal output means 17 and outputting the difference signal, and this signal is sent to the controller 19.
transmitted to. Here, the controller 19 controls means for controlling the temperature and temperature distribution in the crucible 5, that is, the electric power of the heating elements 91 to 94 which are heating means, the relative position of the crucible 5 with respect to the heating elements, and the temperature of the melt in the crucible. It has a function of controlling the strength of the applied magnetic field generated by the magnetic field applying means 20, which is known to be effective in temperature distribution control.

The basics of the specific control method are the deviation signal output from the comparator 18 and each heating element 9! ~
Based on the information regarding the crucible position and temperature distribution in the crucible or the strength of the applied magnetic field and the temperature distribution in the crucible, etc., the control power of each heating element 91 to 94 is determined based on the crucible 50 position, applied V & field. One of the strengths or the like is changed to an appropriate value either alone or at the same time, so that the deviation signal from the comparator 18 always approaches zero.

As described above, according to the present invention, the temperature distribution inside the crucible, the position and shape of the growth interface are calculated and estimated at regular intervals based on temperature information at multiple locations around the crucible periphery, and based on the results. By controlling the change in the growth interface position and the growth interface shape], with a preset specified accuracy,
Control of the growth rate of the growth interface position and the shape of the interface was realized, and this will be explained in detail with reference to the following examples.

Embodiment 1 FIG. 4 is a schematic diagram showing a crystal growth furnace and a control device according to an embodiment of the present invention. In the figures, the same reference numerals indicate the same or corresponding parts.

In Figure @1, approximately 2
000 g of 01 Ninho Melt 2 was prepared. Approximately 200 EOB Os was used as the liquid sealant 4. The crucible holder 6 is made of high purity graphite. 4 heating elements, 9t, L
and 94 are also composed of high-purity graphite resistors,
Heat generation was controlled by externally applied power. The atmosphere in the furnace during crystal growth was set to about 5 atmospheres of inert gas. Five pairs of thermocouples used for temperature detection 111.1'h, 113.114
and 11s were all based on platinum-platinum rhojucum. The detected thermocouple output was taken out to the outside of the airtight container 10 through a slip ring 13 at the bottom of the crucible shaft 7, and inputted to a temperature measuring means 14 having a means for converting the thermocouple output into an actual temperature. Next, the signal converted into temperature information of each part (5 points) around the crucible was input to the temperature distribution calculator R15. The temperature distribution calculator 915 of this embodiment is a system consisting of a personal computer (for example, PC-9801) and a temperature distribution calculation program to which the finite element method is applied.

2. In other words, this system is based on the shape and material of the crucible 5 and crucible holder 6, the amount and physical constants of the GIAI melt 3 in the crucible, the amount and physical constants of the liquid sealant (NZOs) 4, etc. This is a simulation system constructed based on determined boundary conditions. This system was configured to calculate the temperature distribution inside the crucible once every 4 minutes by inputting temperature information around the crucible (5 points).

Furthermore, information on the calculated temperature distribution can be found in the temperature distribution table foot RI
It was communicated to B. Here, the temperature distribution in one melt and the crystal is displayed on a TV monitor with isothermal lines at regular intervals (10°C), with the isotherm line of the melting point corresponding to the growth interface 12 of the crystal as the boundary, and the shape and position of the growth interface 12 are shown. Furthermore, the temperature distribution of the metal body inside the crucible 5 can be grasped.

Next, control of the crystal growth rate in this example, that is, the moving speed of the growth interface 12 (in this example, 5 wa /
h) was carried out as follows.

The program signal output terminal 917 outputs a signal of the position change of the growth interface 12 (the interface shape is approximately a plane) with respect to the elapsed time, which is programmed in advance, and a temperature distribution calculation circuit 9
The comparator 18 compares the signal of the change in the position of the growth interface 12 calculated in step 15 (in this example, the melting point position at the center was approximately recognized as the position of the growth interface), and this deviation signal is sent to the controller. This was communicated to 18. The controller 111 controls the deviation signal within a certain range according to a predetermined control algorithm that mainly controls the crucible position and assists in controlling the heating power of the four heating elements 91 to 94. The growth rate of the crystal was controlled as follows.

The GaAg crystal grown by K as described above was
The diameter of the constant diameter part is determined by the shape of the BN crucible 5, 80
The growth rate in this example was confirmed by changing the rotation speed of the crucible from the usual 2Orpm to lrpmK at fixed time (2 hours) intervals during crystal growth. A control process was introduced to reduce K (for about 5 minutes), and the interval of growth stripes generated in the grown crystal due to this was observed using an X-ray topography. As a result, it was confirmed that the interval of the growth stripes caused by the change in the rotation of the above-mentioned crucible was controlled within the range H of 10±0.2, and the growth rate set in this example was 5Ill//.
It was confirmed that crystal growth was occurring at 1 h. In addition,
The correspondence between the calculated temperature distribution in this example and the actual temperature distribution in the melt and in the crystal is as follows: Needless to say, this is done by correlating the temperature distribution measurement experiment with the calculation results, in order to improve the accuracy of this calculation system.

Example 2 This example was carried out for the purpose of making it possible to control the shape of the growth interface 12 in addition to controlling the growth rate performed in Example 1 above. In FIG. 2 relating to this embodiment, 9
The fifth heating element m is added and is used to precisely control the temperature distribution near the growth interface 12. In addition, the pBN crucible 5 used had a diameter of 80 cm, and the GaA crucible doped with In impurities at 1020 atoms/crn.
s Melt 3 is about 2000 g 1 B used as liquid sealant 4
I Os is approximately 200 g. The atmosphere inside the furnace was set to 5 atmospheres. The temperature detection using thermocouples 111 to 114 and the temperature distribution calculation system are the same as in the first embodiment.

Next, the control of the growth rate and growth interface shape performed in this example will be explained. Program signal output means 1
At T, the growth is approximated to a spherical surface based on the change in the position of the center of the growth interface 12 (the interface shape is not a plane) over the elapsed time, and the position of the center of the growth interface and 0.8r (r: radius of the crystal). Changes in the interface shape are programmable. This program output, the position of the growth interface calculated by the temperature distribution calculation means 15 (the melting point position at the center of the crucible was set as the position of the growth interface), and the shape of the growth interface (the melting point position at the center of the crucible and the melting point device of 0.8r) A comparator 18 compares the signals of the changes in the shape (which was originally approximated to a spherical surface), and transmits these deviation signals to the controller 19.

In this example, the growth rate (change in the growth interface position) and the growth interface shape were controlled by the controller 19 based on the following control algorithm.

(2) The heating voltage of the heating elements 91, 9 and 94 is kept constant to maintain the basic temperature distribution in the furnace.

(2) The position of the crucible is moved according to a preprogrammed growth rate so that the growth interface is approximately at the center of the heating element 95.

(2) The growth interface shape is controlled by using the heating power of the heating element 9s as the main control means and by using the strength of the applied magnetic field as an auxiliary control means.

As in the case of Example 1, the 90aAa crystal grown in the above manner had a diameter of 80m, a length of the constant diameter part of about 501m, and <
It was a single crystal with a growth orientation of 100>. The shape of the growth interface, which was mainly controlled in this example, was confirmed to be a convex interface toward the targeted melt side by observing the small concentration of InO added as growth stripes using an X-ray topography. .

In the above-described embodiments of the present invention, the case where a GaAg crystal, which is a typical compound semiconductor, is grown by the liquid-sealed vertical Bridgman method (or the liquid-sealed temperature gradient solidification method) was described as an example. Regarding crystals, the idea of the invention is not limited to GL and S crystals, but can also be applied to other semiconductor crystals, metal crystals, and even oxide crystals. Also, how to grow crystals! 7C- Even if the normal vertical Bridgman method,
- It goes without saying that great effects can be obtained when applied to crystal growth methods where observation of the growth state is generally difficult, such as the horizontal purine Raman method.

〔Effect of the invention〕

As explained above, the crystal growth method and growth apparatus of the present invention estimate the position and shape of the growth interface, which was impossible in the past, using a computer simulation method based on the measured temperature distribution information, and also control it. This is what made it possible. As a result, in crystal growth, the single crystallization rate, which is related to the growth rate and the shape of the growth interface, can be significantly improved. Furthermore, in terms of crystal quality, by controlling the growth rate, the distribution of added impurities (In, etc.) in the growth direction can be made uniform, and dislocations can be easily reduced and controlled. Furthermore, it becomes possible to estimate and control the temperature distribution in the crystal after growth, and it is possible to suppress the generation of dislocations by reducing and controlling thermal stress. In addition, significant effects were recognized, including the ability to obtain information useful for controlling point defects in crystals by estimating and controlling the thermal history of crystals.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a crystal growth furnace and a control device according to one embodiment of the present invention, FIG. 2 is a schematic diagram of a crystal growth furnace according to another embodiment of the present invention, and FIG. 1 is a schematic diagram showing the concept of a crystal growth apparatus and growth control using the static vertical Bridgman method. 1...Seed crystal, 2...Ga human language crystal 3...
・・G&人8 Melt liquid, 4・・Liquid sealant, 5・・・・
Crucible, 6@... Fist ruribo holder, T... Crucible shaft, 8... Crucible drive mechanism, 91-9.・・・・・・
Heating element, 10...Airtight container, 111-114...
Fuzzy thermocouple, 12--Growth interface, 13--Slip ring, 14--Temperature measurement means, 15--Temperature distribution calculation means, 16--Temperature distribution display means, 1T
... Program signal output means, 18 ... Comparator, 19 ... Controller, 20 ... Magnetic field application means. Patent applicant Nippon Cat Story Co., Ltd.

Claims (2)

[Claims] (1) Start crystal growth from one end of the melted or synthesized raw material melt or solution in a crucible having a cylindrical shape or various shapes, and gradually grow the crystal in a substantially constant direction. In the crystal growth method for growing a crystal in a shape defined by the crucible, detecting the temperature at a plurality of specific locations around the crucible;
Based on the temperature information at multiple locations, the temperature distribution inside the crucible, the position of the growth interface, and its shape are calculated and estimated at regular intervals, and based on the calculation and estimation results, changes in the growth interface position ( A crystal growth method characterized by controlling both the growth rate) or the growth interface shape, or both the change in the growth interface position and the growth interface shape. (2) In an apparatus for carrying out the crystal growth method according to claim 1, there is provided a means for detecting the temperature at a plurality of specific locations on the outer periphery of the crucible, and for extracting and outputting these temperature signals to the outside; means for approximating and outputting the temperature distribution inside the crucible and the position and shape of the crystal growth interface; means for outputting the position of the growth interface and changes in its shape over time which are programmed in advance; and the output of the approximate calculation and the program. a means for comparing the output and outputting the deviation information at a predetermined signal level; and a means for adjusting the growth interface position or its shape so as to reduce the deviation to a predetermined value or less based on this comparison/deviation information, or both of these. A crystal growth apparatus characterized by having a means for controlling.