WO2019013301A1

WO2019013301A1 - Single-crystal growth apparatus

Info

Publication number: WO2019013301A1
Application number: PCT/JP2018/026393
Authority: WO
Inventors: 金子　良夫; 十倉　好紀; 尚博加賀; 佐野　直樹
Original assignee: 国立研究開発法人理化学研究所; アウレアワークス株式会社
Priority date: 2017-07-12
Filing date: 2018-07-12
Publication date: 2019-01-17

Abstract

Provided is a single-crystal growth apparatus for growing a single crystal by irradiation with heating laser light. Provided is a growth apparatus provided with: a raw material rod extending along a first direction, the vertical direction being the first direction; and M laser irradiation heads for radiating M heating laser beams to the raw material rod, the laser irradiation heads being provided in a radial pattern with the raw material rod at the center thereof; the irradiation intensity distribution of the M heating laser beams in a two-dimensional plane orthogonal to the optical axes of the heating laser beams having heating laser beams having an irradiation intensity distribution asymmetrical in the first direction, a second irradiation intensity distribution in a second direction orthogonal to the first direction having a substantially uniform irradiation intensity, and the irradiation intensity gradually decreasing downward and the irradiation intensity steeply decreasing upward in the irradiation intensity distribution in the first direction.

Description

Single crystal growth system

The present invention relates to a single crystal growth apparatus.

In a floating melting zone single crystal growth method using laser light for growing a single crystal by melting a raw material rod installed in the vertical direction, heating laser light is substantially uniform in the axial direction of the raw material rod and in the radial direction of the raw material rod A heating method has been proposed in which a plurality of heating laser beams having an irradiation intensity distribution (this irradiation intensity distribution is often referred to as a top hat irradiation intensity distribution) having an irradiation intensity of Patent Document 1).
[Patent Document 1] Patent No. 5181396

Problem to be solved

However, a plurality of heating laser beams having an irradiation intensity distribution (that is, top hat irradiation intensity distribution) in which the heating laser light is substantially uniform in the axial direction of the raw material bar and substantially uniform in the radial direction of the raw material bar In the conventional heating method according to the above, a steep temperature gradient is generated in the axial direction of the crystal rod grown from the melting zone, so the quality of the obtained single crystal is deteriorated.

General disclosure

In the first aspect of the present invention, the raw material rod extending in the first direction with the vertical direction as the first direction and the material rod radially provided about the raw material rod, and M raw laser beams are applied to the raw material rod The irradiation intensity distribution of the M heating laser beams in a two-dimensional plane orthogonal to the optical axis of the heating laser light is provided with M laser irradiation heads for irradiation, and the first irradiation intensity predetermined in the first direction A second irradiation intensity distribution having a distribution and in a second direction orthogonal to the first direction has substantially uniform irradiation intensity, and the first irradiation intensity distribution has a maximum intensity Imax or a continuous maximum intensity Imax. Assuming that the position of the lower end portion of is 50, and the position of the downward 50% irradiation intensity (0.5 × Imax) of the maximum intensity Imax is Z1,
ZL-Z1 2 2 mm
To provide a single crystal growth apparatus.

In the second aspect of the present invention, the first irradiation intensity distribution is such that the position of the upper end portion of the maximum intensity Imax or the continuous maximum intensity Imax is ZU, and the upward 50% irradiation intensity of the maximum intensity Imax (0. Assuming that the position of 5 × Imax) is Z2,
3 mm Z Z2-ZU ≧ 0 mm
To provide a single crystal growth apparatus.

In the third aspect of the present invention, a raw material rod extending in the vertical direction is prepared, and M heating laser beams are applied to the raw material rod using M laser irradiation heads provided radially about the raw material rod. The irradiation intensity distribution of M heating laser beams in a two-dimensional plane orthogonal to the optical axis of the heating laser beam has a first irradiation intensity distribution determined in advance with the vertical direction as the first direction. And, the second irradiation intensity distribution in the second direction orthogonal to the first direction has a substantially uniform irradiation intensity, and the first irradiation intensity distribution has the lower end of the maximum intensity Imax or the continuous maximum intensity Imax. Assuming that the position is ZL and the position of the 50% irradiation intensity (0.5 × Imax) below the maximum intensity Imax is Z1:
ZL-Z1 2 2 mm
A method of growing a single crystal is provided.

In the fourth aspect of the present invention, the first irradiation intensity distribution is such that the position of the upper end portion of the maximum intensity Imax or the continuous maximum intensity Imax is ZU, and the upward 50% irradiation intensity of the maximum intensity Imax ( Assuming that the position of 0.5 × Imax) is Z2,
3 mm Z Z2-ZU ≧ 0 mm
A method of growing a single crystal is provided.

The above summary of the invention does not enumerate all of the features of the present invention. In addition, a combination of these feature groups can also be an invention.

1 shows an example of a perspective view of a single crystal growth apparatus 100 according to a first embodiment. 1 shows an example of a top view of a single crystal growth apparatus 100. FIG. An example of lens composition of laser irradiation head 50 is shown. An example of irradiation intensity n cloth of the heating laser beam 3 is shown. An oval-shaped irradiation intensity distribution shape in the (XZ) plane of the heating laser light 3 of Example 1 is shown. The irradiation intensity distribution of the Z-axis direction of the raw material stick | rod 1 which concerns on Example 1 is shown. The irradiation intensity distribution of the X-axis direction of the raw material stick | rod 1 which concerns on Example 1 is shown. The example of melting temperature observation of the melting zone 4 during crystal growth is shown. An example of the division method of the laser beam 5 is shown. An example of upper arrangement of the reflective mirror 80 concerning Example 2 is shown. An example of upper arrangement of the reflective mirror 80 concerning Example 2 is shown. The irradiation intensity distribution of the X-axis of the heating laser beam 3 which concerns on Example 2, and Z-axis direction is shown. An example of lower part arrangement | positioning of the reflective mirror 80 which concerns on Example 3 is shown. The irradiation intensity distribution of the X-axis of the heating laser beam 3 which concerns on Example 3, and Z-axis direction is shown. The irradiation intensity distribution of the Z-axis direction of the heating laser beam 3 which concerns on Example 4 is shown. The irradiation intensity distribution of the X-axis of the heating laser beam 3 which concerns on Example 4, and Z-axis direction is shown. The irradiation intensity distribution of the Z-axis direction of the heating laser beam 3 which concerns on Example 5 is shown. The irradiation intensity distribution of the Z-axis direction of the heating laser beam 3 which concerns on Example 6 is shown.

Hereinafter, the present invention will be described through the embodiments of the invention, but the following embodiments do not limit the invention according to the claims. Moreover, not all combinations of features described in the embodiments are essential to the solution of the invention.

Example 1
FIG. 1 shows an example of a perspective view of a single crystal growth apparatus 100 according to a first embodiment. FIG. 2 shows an example of a top view of the single crystal growth apparatus 100 at the time of growth of the raw material rod 1 to the crystal rod 2.

The single crystal growth apparatus 100 includes N power supplies 10, one laser light source 20, one laser light dividing device 30, M optical fibers 40, M laser irradiation heads 50, and M And the plurality of dampers 60. M is an integer greater than 1 (ie, M> 1). In this example, the case where the number of power supplies 10 is N = 2 and the number of divisions M = 5 is shown. The raw material rod 1, the crystal rod 2 and the melting zone 4 are shown. The single crystal growth apparatus 100 of this example has two radiation thermometers 70 of a radiation thermometer 70-1 and a radiation thermometer 70-2. The radiation thermometer 70-1 measures the temperature within a radius of 0.5 mm at the upper and lower centers on the central axis of the melting zone 4. The radiation thermometer 70-2 measures the temperature of the crystal rod 2 within a radius of 0.5 mm in the range of about 0 mm to 20 mm directly below the melting zone 4 on the central axis of the crystal rod 2.

In the present specification, the vertical direction is taken as the first direction. The raw material stick | rod 1 extended along a 1st direction is installed. The Z-axis direction is taken as the central axis direction of the raw material rod 1. In a two-dimensional plane perpendicular to the optical axis of the heating laser light 3, the direction perpendicular to the Z axis is taken as the X axis direction. In addition, a direction perpendicular to the Z axis (that is, the radial direction of the raw material rod 1) with the central axis of the raw material rod 1 as a center is referred to as an R direction. The raw material rod 1 of this example has a diameter D. The height of the melting zone 4 is H. Furthermore, in the present specification, the downward direction refers to the gravity direction in the vertical direction, and the upward direction refers to the direction opposite to the gravity direction in the vertical direction.

In the floating melting zone method in the single crystal growth apparatus 100, heating irradiation light is required to melt the raw material rod 1. The single crystal growth apparatus 100 of this example uses M pieces of heating laser light 3 as the heating irradiation light of the columnar raw material rod 1.

The M heating laser beams 3 are radially incident on the raw material rod 1 around the central axis of the raw material rod 1. The M heating laser beams 3 have an oval-shaped irradiation intensity distribution in a (XZ) two-dimensional plane orthogonal to the optical axis of the heating laser beams 3. The shape of the irradiation intensity distribution of the M heating laser beams 3 has a length including at least one shape of a circular shape, an elliptical shape, a rectangular shape, and a shape combining some of these shapes in the (XZ) plane It is circular. More specifically, M heating laser beams 3 have a bell-shaped irradiation intensity distribution in the Z-axis direction (that is, the extending direction of the raw material rod 1) in the (XZ) plane, and X The irradiation intensity distribution is substantially uniform in the axial direction.

One laser light source 20 is driven by N power supplies 10 to generate one laser light 5. One laser light source 20 may be controlled by the output of N power supplies provided to satisfy N <M. When the laser light source 20 has a high output of 1 KW or more, the current required is several tens of A or more. When the amount of supply current of a commercially available power source is small, two or more may be used. Even in two or more power supplies, the power supply can be controlled like one by cascade connection. One laser light source 20 emits the generated one laser beam 5 to one laser beam splitter 30. One laser light source 20 may include a plurality of semiconductor diodes.

One laser beam splitting device 30 splits one laser beam 5 into M beams. The laser beam splitting device 30 causes the split laser beam 5 to enter M optical fibers 40. The laser beam splitting device 30 of this example splits one laser beam 5 into M beams.

The M optical fibers 40 have five optical fibers 40-1 to 40-5. The M optical fibers 40 emit the M laser beams 5 as the M heating laser beams 3. The cross-sectional shape of the M optical fibers 40 has an oval cross-sectional shape made of at least one of a circular cross-sectional shape, an elliptical cross-sectional shape, a rectangular shape, and a shape combining these shapes.

The M laser irradiation heads 50 condense the M heating laser beams 3 incident from the M optical fibers 40 on the raw material rod 1. The M laser irradiation heads 50 are arranged radially about the Z-axis direction in which the raw material rod 1 extends. Further, the M laser irradiation heads 50 are disposed so as to irradiate the raw material rods 1 with the M heating laser beams 3 at equal angles. The laser irradiation head 50 of the present example irradiates the heating laser light 3 from an odd number of five directions at an angle of an interval of about 72 degrees centering on the raw material rod 1. The number of the M laser irradiation heads 50 is preferably an odd number.

For example, when M is an odd number arrangement of five, the irradiation intensity distribution on the outer periphery of the raw material rod 1 has a uniformity of the irradiation intensity of 95%. The irradiation intensity distribution on the outer periphery of the raw material rod 1 when M is 7 has a uniformity of the irradiation intensity of 97%. The uniformity of the irradiation intensity of the irradiation intensity distribution on the outer periphery of the raw material rod 1 in the case of 6 where M is an even number is 85%. When the laser irradiation head 50 has an even number M, the uniformity of the irradiation intensity of the irradiation intensity distribution is reduced. Therefore, it is preferable that the number of the M laser irradiation heads 50 is an odd number. The M laser irradiation heads 50 shape the M heating laser beams 3 into a predetermined irradiation shape.

The damper 60 shown in FIG. 2 has a water cooling mechanism, and absorbs the heating laser beam 3 which has passed around the raw material rod 1 of the M heating laser beams 3. The M dampers 60 are provided to face the M laser irradiation heads 50 with the raw material rod 1 interposed therebetween. Thereby, damage due to heating of the inside of the single crystal growth apparatus 100 by the M laser irradiation heads 50 can be prevented.

The radiation thermometer 70-1 measures the temperature of the melting zone 4 by measuring the intensity of the light emitted from the melting zone 4 formed by melting the raw material rod 1. The radiation thermometer 70-1 can measure the local temperature within the 0.5 mm radius of the melting zone 4 during crystal growth. An in-situ observation method that can measure local temperature within 0.5 mm radius of melting zone 4 during crystal growth determines the crystal structure composition of the crystal material, realizes crystal growth of the composition, and optimum conditions for single crystal preparation It is extremely important in determining the For example, the composition obtained differs depending on the melting zone temperature. This is because the melting temperature gives inherent physical property information of the material which does not depend on the growth conditions of the crystal device. In the case of observation with a conventional halogen lamp using a confocal ellipsoid, in-situ temperature observation of a minute area is difficult because the melting zone 4 is surrounded by a mirror. The temperature reproducibility of the radiation thermometer 70 is within ± 1 ° C. Once optimization of the melting temperature can be realized, the output of the laser light source 20 is controlled by the power supply 10 so that the optimum temperature is obtained even if the diameter of the melting zone 4 changes and the crystal growth time is changed. it can. The radiation thermometer 70-1 is a great weapon for the control method during crystal growth, as opposed to the method of monitoring the melting state of the melting zone 4 with a camera. For example, the single crystal growth apparatus 100 controls the input power of the N power supplies 10 according to the radiation light intensity measured by the radiation thermometer 70. Thereby, the single crystal growth apparatus 100 adjusts the radiation light intensity of the heating laser light 3.

The radiation thermometer 70-2 measures temperatures in the range of about 0 to 20 mm in the vicinity of the upper end of the crystal rod 2 and immediately below the melting zone. This measurement makes it possible to monitor the cooling state near the upper end of the crystal rod 2. The measurement of the temperature of the crystal rod 2 is important because the thermal conductivity coefficient is largely different depending on the material. Insulating materials, semiconductor materials and metals have thermal conductivity coefficients that differ by several orders of magnitude. Also, the heat conduction coefficient near the melting temperature is often unknown. For this reason, it is very important to measure the temperature of the crystal rod 2 in the crystal growth state in which the actual shape of the crystal rod 2 and the crystal rod 2 are held. Not only that, valuable physical information on the material can be obtained.

For example, the temperature at a portion 10 mm below the upper end of the crystal rod 2 is measured. Thereby, the cooling rate of the crystal rod 2 can be monitored. The temperature of melting zone 4 is observed at 70-1. Let that temperature be TM. It is assumed that the temperature of the crystal rod 2 of 10 mm downward from the upper end part boundary of the melting zone 4 and the crystal rod 2 is TS. When the growth rate is S mm / hour, (TM-TS) / (10 / S) is the average cooling temperature per hour from the melting temperature of the single crystal obtained. In the case of TM-TS = 400 ° C., S = 4 mm / hour, the average cooling rate in one hour from the melting temperature is 160 ° C. Knowing the average cooling time near the high melting temperature is very important because it has a great influence on residual thermal strain during crystal formation.

The cooling time of the grown single crystal is preferably short. In particular, the cooling time near the melting temperature is important. It is necessary for the elements constituting the crystal to settle at the crystal lattice point, which is a potential stable point, from the intense movement in the molten state. When moving from this intense movement to the potential stability point, it is necessary to gradually cool so that the metastable potential position is not determined before stabilizing at the crystal lattice point. In the case of rapid cooling, there is an opportunity for the element to stabilize at the metastable potential position. Elements remaining in the metastable position may cause thermal residual strain to the crystal lattice due to the occurrence of cracks, affect the conduction electrons, and may cause serious adverse effects such as deterioration of reproducibility such as the superconducting transition temperature. Whether the cooling time 160 ° C. of the crystal rod 2 from the melting temperature is too large depends on the material properties. The case where a crack is generated in the obtained crystal rod 2 is an example in which the cooling rate is obviously too fast. This is also an example in which the cooling rate is too fast even in the case where a change in the electron conduction properties of the crystal is exhibited, such as a decrease in the superconducting transition temperature. It is necessary to further reduce the intensity gradient in the downward irradiation intensity distribution of the Z-axis for materials in which such a phenomenon is recognized. Alternatively, it is necessary to increase the crystal growth rate. In any case, the conventional laser FZ single crystal device having an irradiation intensity distribution (top hat irradiation intensity distribution) having a sharp irradiation intensity distribution in the Z-axis direction is extremely serious in terms of the quality of the obtained single crystal. May have.

The raw material rod 1 is a sintering rod of the raw material. The melting zone 4 can be formed between the raw material rod 1 and the crystal rod 2 by heating and melting the lower end portion of the raw material rod 1 and the upper end portion of the crystal rod 2 with M heating laser beams 3. For example, the melting temperature of the raw material is 200 ° C. to 3000 ° C. In the floating melting zone method, the crystal surface of the upper end of the crystal rod 2 is epitaxially grown to obtain a single crystal. This epitaxial growth can be realized by depositing layers by gradually lowering the crystal rod 2. The descending speed of the crystal rod 2 is the crystal growth rate.

The quartz tube 6 is a circular tube made of quartz transparent to the wavelength of the M heating laser beams 3. The raw material rod 1 is disposed on the central axis of the quartz tube 6. The quartz tube 6 is filled with a gas optimum for crystal growth of the crystal rod 2.

The M laser irradiation heads 50 form M heating laser beams 3 having a bell-shaped irradiation intensity distribution in the Z-axis direction and a substantially uniform irradiation intensity distribution in the X-axis direction. In the present specification, the bell-shaped irradiation intensity distribution refers to an irradiation intensity distribution having an intensity distribution in which the irradiation intensity decreases gradually in the upward and downward directions with the vicinity of the center of the irradiation intensity distribution in the Z-axis direction becoming maximum. . The irradiation intensity that is the maximum intensity of the irradiation intensity distribution in the Z-axis direction is Imax. By making the irradiation intensity distribution in the Z-axis direction bell-shaped, the M laser irradiation heads 50 make the reduction of the irradiation intensity distribution of the crystal part epitaxially grown at the interface between the melting zone 4 and the crystal rod 2 smooth and Suppress rapid cooling of parts. The shape whose irradiation intensity decreases in the downward direction of the Z axis has a polygonal irradiation intensity distribution even if it has a curved irradiation intensity distribution or a linear irradiation intensity distribution. You may In one example, the M heating laser beams 3 have a bell-shaped irradiation intensity distribution in the Z-axis direction.

The important point here is that even when the irradiation intensity distribution in the Z-axis direction has a bell shape, the irradiation intensity distribution is substantially uniform in the X-axis direction. The conventional method using a halogen lamp differs greatly from this example in that the Z-axis direction and the X-axis direction also have a bell shape. Having a substantially uniform irradiation intensity distribution in the X-axis direction ensures that the uniformity of the irradiation intensity in the outer peripheral direction of the raw material rod 1 is as high as 95% in the case of the five laser irradiation heads 50. It is possible to suppress rapid cooling of the crystal rod 2 grown thereon.

Furthermore, the irradiation intensity distribution of the M heating laser beams 3 may be asymmetric in the Z-axis direction. In one example, the lower end portion where the raw material rod 1 is melted may have a sharp irradiation intensity distribution in the M heating laser beams 3. The decrease distribution of the irradiation intensity in the direction of the Z-axis of the bell shape may have an asymmetric distribution of irradiation intensity which is steeper than the decrease distribution of the irradiation intensity in the direction of the Z-axis. The sharply decreasing irradiation intensity distribution suppresses the effect of the molten material of the melting zone 4 being sucked into the raw material rod 1. The raw material rod 1 is a fired rod, and the material density is smaller than that of the crystal rod 2. For this reason, the liquefied material permeates into the gap of the raw material rod 1. The suction of the melt into the rod 1 causes a decrease in the diameter W of the melting zone 4 in the R direction, and at the same time increases the diameter D of the lower end of the rod 1. The decrease in the diameter W of the melting zone 4 and the increase in the diameter D of the raw material rod 1 due to the suction of the melt cause the melting zone 4 to become unstable. In order to suppress the amount of the molten liquid absorbed by the material rod 1, the temperature gradient on the side of the material rod 1 needs to be steep. Such asymmetrical irradiation intensity distribution in the Z-axis direction suppresses absorption to the raw material rod 1, and moreover, the thermal strain to the grown crystal rod 2 is alleviated by the gentle temperature gradient on the crystal rod 2 side. Do. A conventional halogen lamp can not realize such an illumination shape. It can be realized only if the heating light is a highly directional laser light. The irradiation intensity distribution of the irradiation shape of the halogen lamp has an irradiation intensity distribution in a very wide range of 50 mm or more in the vertical direction, and is a light source which is essentially different from the laser light.

In addition, when heating laser light, which is the conventional top hat irradiation intensity distribution, is used, even if the steep irradiation intensity distribution on the side of the raw material rod 1 can be realized, the thermal residual strain due to the steep irradiation intensity distribution on the crystal rod 2 Generate This causes a crack in the crystal rod 2 and causes serious problems such as deterioration of the reproducibility of the superconducting transition temperature Tc.

FIG. 3A shows an example of the lens configuration of the laser irradiation head 50. As shown in FIG. FIG. 3B shows an example of the irradiation intensity distribution of the heating laser light 3.

The laser irradiation head 50 has a plurality of lenses. The laser irradiation head 50 adjusts the shape and the irradiation intensity of the irradiation intensity distribution of the heating laser light 3 by adjusting the intervals and the focal lengths of the plurality of lenses. For example, the laser irradiation head 50 converts the laser light 5 from the M optical fibers 40 into parallel light with a convex lens. The M parallel heating laser beams 3 pass through the transparent flat plate. This portion is a component of the irradiation head A. Thereafter, the component B is configured to transmit a transparent flat plate and thereafter have a bell shape in the Z-axis direction and a substantially uniform irradiation intensity distribution in the X-axis direction with three lenses. By appropriately selecting three lenses, a bell shape in the Z-axis direction and a substantially uniform irradiation intensity distribution in the X-axis direction can be obtained. An oval E in the drawing indicates a two-dimensional irradiation intensity distribution on the (XZ) plane formed on the laser irradiation head 50.

The laser irradiation head 50 is configured to move the distance L between the part A and the part B. The laser irradiation head 50 fixes the component A on the optical bench and adjusts the movable distance L to adjust the irradiation distance with the raw material rod 1. In order to change the half width W ₀ when the intensity of the bell-shaped irradiation intensity in the Z-axis direction becomes 50%, it is necessary to change the focal length of the lens of the B component. Therefore, the lens replacement of the B component is designed in advance so that it can be easily replaced from the side. By changing the lens length and adjusting the movable distance L, the bell shape in the Z-axis direction can be expanded or contracted to the predetermined bell shape at the position of the raw material rod 1 without changing the substantially uniform length in the X-axis direction. it can.

Further, FIG. 3B shows an example of the oval-shaped irradiation intensity distribution of the M heating laser beams 3 collected on the raw material rod 1. The irradiation intensity distribution in the Z-axis direction of the M heating laser beams 3 is a bell-shaped irradiation intensity distribution. Imax is the maximum value of the irradiation intensity in the Z-axis direction. The laser irradiation head 50 adjusts the plurality of lenses so that the irradiation intensity distribution decreases in the vertical direction of the Z axis from the position of Imax at which the irradiation intensity in the Z axis direction is maximum.

Z1 is the position of 50% irradiation intensity (0.5 × Imax) in the downward direction (ie, in the negative direction of the Z axis). Further, Z2 is a position of 50% irradiation intensity (0.5 × Imax) in the upward direction (that is, the positive direction of the Z axis). Z1 ′ is a position of 10% irradiation intensity (0.1 × Imax) in the downward direction (ie, in the negative direction of the Z axis). Further, Z2 'is a position of 10% irradiation intensity (0.1 × Imax) in the upward direction (that is, the positive direction of the Z axis).

The position of the maximum intensity Imax on the Z axis is Z = 0. When the case where the maximum intensity Imax is substantially uniform in the Z-axis direction is continuous, it is expressed as the continuous maximum intensity Imax. Assuming that the position of the lower end in the Z-axis direction of the continuous maximum intensity Imax is ZL, Z1 which is the position of the 50% irradiation intensity (0.5 × Imax) is
[Equation 1]
ZL-Z1 2 2 mm
It has an irradiation intensity distribution that satisfies That is, the reduction of the irradiation intensity is suppressed so that the irradiation intensity is 50% or more at a position of 2 mm below the maximum intensity Imax. Thereby, the quenching of the obtained crystal rod 2 is relaxed. In the top hat irradiation intensity distribution, the irradiation intensity becomes zero at a position 2 mm below the maximum intensity Imax, and the obtained crystal rod 2 is rapidly cooled.

Furthermore, the cooling rate from the melting temperature of the crystal rod 2 to a temperature near room temperature can be controlled. The irradiation intensity distribution in the direction of the Z-axis formed by the M heating laser beams 3 has an upward and downward width at which the irradiation intensity becomes 10% of the maximum value in the bell-shaped irradiation intensity distribution in the first direction. Where Z ₀ and the height in the first direction of the melting zone 4 where the material rod 1 is melted is H,
[Equation 2]
(Z ₀ -H) / 2 ≧ S
Adjust multiple lenses to meet Moreover, it is preferable that the laser irradiation head 50 adjust the space | interval of a lens, without changing the number of objects of several lenses.

S is crystal growth rate (mm / hour). By designing the Z ₀ and (2S + H) mm, so that the cooling time from the melting temperature of the grown crystal rod 2 was designed to be substantially 1 hour. For example, the crystal growth rate is 4 mm per hour. The height H of the melting zone 4 is 5 mm. In the case of a bell-shaped heating laser having an irradiation intensity distribution of Z ₀ = 21 mm, the obtained crystal has a cooling time from the melting temperature T _M to the temperature of T _M × 0.1 designed to be 2 hours. If S = 2 mm / hour, the cooling time is designed to be 4 hours.

The M laser irradiation heads 50 may adjust the bell-shaped irradiation intensity distribution according to the moving speed of the crystal rod 2 (that is, the crystal growth speed). For example, the M laser irradiation heads 50 may make the slope of the bell-shaped irradiation intensity distribution gentler as the moving speed of the crystal rod 2 increases. In addition, the M laser irradiation heads 50 may make the slope of the bell-shaped irradiation intensity distribution steep according to the decrease in the moving speed of the crystal rod 2. The M laser irradiation heads 50 adjust the lens replacement or the interval of L and adjust the irradiation intensity distribution of the M heating laser beams 3.

FIG. 4 shows the case of Example 1 of the irradiation temperature shape of the oval shape of the heating laser beam 3. The irradiation intensity distribution of this example is a simulation result of the lens optical system calculated based on the irradiation intensity distribution from the circular optical fiber 40. By appropriately selecting the focal length and the like of the lens system, highly accurate results can be obtained. From the figure, it is confirmed that the irradiation temperature shape of the heating laser light 3 has an oval shape.

FIG. 5 shows an example of the irradiation intensity distribution in the Z-axis direction of the raw material rod 1. The M heating laser beams 3 of this example have a bell-shaped irradiation intensity distribution in the Z-axis direction.

The bell shape is an irradiation intensity distribution in which the intensity gradually decreases in the vertical direction around the position Z = 0 of the maximum irradiation intensity Imax. Such an irradiation intensity distribution is also called a Gaussian distribution shape. In particular, the important point is the downward inclination of the Z axis. By using the M heating laser beams 3 having the downward gentle slope, temperature cooling from the melting temperature accompanying the lowering of the upper end of the grown crystal rod 2 with the growth rate is alleviated. The sharp decrease in the downward irradiation intensity causes rapid cooling from the melting temperature as the upper end of the grown crystal rod falls with the growth rate.

In the method in which the irradiation intensity distribution has a top hat irradiation intensity distribution, the irradiation intensity is zero at about 2 mm from the lower end of the continuous Imax. The 50% irradiation intensity is not even about 1 mm, and has a very steep temperature gradient downward from Imax. The reason why the irradiation intensity at position Z1 of 50% irradiation intensity is important is that the thermal strain phenomenon to the crystal obtained a temperature gradient in the region of half (50%) of the melting temperature from the melting temperature of the material is greatly affected. It is because it exerts. Therefore, the irradiation intensity distribution of 100% to 50% of the irradiation intensity which makes this temperature range is crucial in relieving the residual thermal strain given to the crystal rod. Therefore, the irradiation intensity distribution of the M heating laser beams 3 must have a gradual decrease in the downward intensity. The position Z1 of 50% of the maximum intensity Imax in the bell shape distribution must be at least 2 mm or more from the position Z = 0 of Imax. The advantage of the bell-shaped radiation intensity distribution is that the intensity gradient near Imax is small. This feature ensures that the temperature gradient at this position can be reduced because the slope of the irradiation intensity distribution near the boundary between the melting zone 4 and the crystal rod 2 is small.

The position Z1 in the lower direction of the irradiation intensity of 0.5 × Imax is −6 mm. This can suppress rapid cooling of the crystal rod to around room temperature. The width Z ₀ of the M heating laser beams 3 at which the irradiation intensity distribution of the M heating laser beams 3 is 10% is 21 mm. In the case of a crystal growth rate of 4 mm / hour, the system is cooled to the temperature of the melting temperature × 0.1 in ((21-5) / 2) / 4 = 2 hours. If the growth rate is 2 mm / hour, the cooling time can be 4 hours. If the growth rate is 1 mm / hour, the cooling time can be 8 hours. The first radiation intensity distribution may have a linear or polygonal radiation intensity distribution. Further, the first irradiation intensity distribution may have an irradiation intensity distribution which is a combination of a part of a bell-shaped irradiation intensity distribution and a part of a linear or polygonal irradiation intensity distribution.

As mentioned above, the heating laser beam 3 can moderate the rapid cooling to the crystal stick 2 by giving a desired inclination to the irradiation intensity distribution in the Z-axis direction, and can suppress the crack generation of the crystal due to the thermal stress. In addition, it reduces or eliminates the serious influence of residual thermal strain on the physical properties of the crystalline material. In particular, in the case of an insulating material having a low thermal conductivity, the inclination of the irradiation intensity distribution in the Z-axis direction is an essential requirement.

Here, as for the irradiation intensity distribution in the radial direction, it is preferable that the crystal rod 1 is included in the region having the diameter D of the raw material rod 1 and the substantially uniform irradiation intensity distribution in the X-axis direction. The M heating laser beams 3 have a substantially uniform irradiation intensity distribution in the X-axis direction. Let L be the length of a constant irradiation intensity. When the diameter L of the raw material rod 1 is W, the length L is
[Equation 2]
L ≧ W
Adjust multiple lenses to meet

In the case of Example 1 in FIG. 6, L is 8 mm long. W has a uniform length suitable for the diameter of the raw material rod 1 of about 5 to 6 mm. Furthermore, it has a gentle irradiation intensity distribution of ± 2 mm on the left and right. This inclination increases the margin when the raw material rod 1 is decentered to the left and right.

FIG. 7 shows an example of an actual measurement value of the radiation thermometer 70-1. The vertical axis indicates the temperature [° C.] of the melting zone 4 and the horizontal axis indicates the time. The material of the raw material rod 1 is Nd ₂ Mo ₂ O ₇ . Nd ₂ Mo ₂ O ₇ melts around 1630 ° C. The temperature of the melting zone 4 decreases by about 10 ° C. from 1630 ° C. to 1620 ° C. after 2 hours. The temperature change of the melting zone 4 can not be determined by the monitor image monitoring the melting zone 4. The temperature drop of the melting zone 4 is due to the attenuation of the transmitted light of the M heating laser beams 3 due to the adhesion to the inner surface of the quartz tube 6 due to the evaporation of the raw material. Although the deposit on the inner surface of the quartz tube 6 can be confirmed after crystal preparation, it can not be observed during crystal preparation. In this example, by using the radiation thermometer 70, the temperature change of the melting zone 4 can be monitored during crystal production. Thereby, the single crystal growth apparatus 100 can control the intensity of the M heating laser beams 3 in accordance with the temperature change of the melting zone 4. That is, the single crystal growth apparatus 100 can stably produce the crystal rod 2 by in-situ observation of the temperature of the melting zone 4.

The temperature reproducibility of the radiation thermometer is within ± 1 ° C. Therefore, once the temperature of the melting zone 4 can be confirmed, the material can be easily controlled to the melting temperature after the next time. The single crystal growth apparatus 100 controls the intensity of the M heating laser beams 3 so that the monitor temperature by the radiation thermometer 70-1 becomes constant. In one example, the single crystal growth apparatus 100 detects a decrease in melting temperature due to the evaporant from the source material, increases the applied current of the power supply 10, and controls the melting zone temperature to be kept constant. The single crystal growth apparatus 100 of this example can prevent the temperature of the melting zone 4 from lowering by controlling the intensity of the M heating laser beams 3.

The single crystal growth apparatus 100 may automatically control the temperature of the melting zone 4. For example, the single crystal growth apparatus 100 can control the temperature of the melting zone 4 within ± 1 ° C. by detecting the output of the radiation thermometer 70-1 and performing PID control of the power supply current for the heating laser. Thus, the single crystal growth apparatus 100 preferably includes the radiation thermometer 70-1.

FIG. 8 shows an example of the method of dividing the laser light 5. One laser beam splitting device 30 includes a Y-direction collimator 31, an X-direction collimator 32, a splitting mirror 33, a first focusing lens 36, and a second focusing lens 37. Thereby, one laser beam 5 irradiated by one laser light source 20 is divided into five optical fibers 40.

One laser light source 20 irradiates one laser beam 5 to one laser beam splitter 30. One laser light source 20 is connected to the heat sink 25.

The Y-direction collimator 31 and the X-direction collimator 32 convert one laser light 5 from one laser light source 20 into parallel light. The Y-direction collimator 31 and the X-direction collimator 32 are an example of a collimator lens.

The split mirror 33 splits one incident laser beam 5 into M beams. One laser beam splitter 30 of this example has four split mirrors 33 in order to split one laser beam 5 into five. In one example, the splitting mirror 33 splits one laser beam 5 by reflecting a part of one laser beam 5 and transmitting the other.

The first condensing lens 36 and the second condensing lens 37 condense the laser light 5 split by the splitting mirror 33 and make it enter the optical fiber 40. The first condenser lens 36 and the second condenser lens 37 are arranged to satisfy the condition of the beam parameter product (BPP) of the optical fiber 40. In addition, although the lens which condenses the laser beam 5 to the optical fiber 40 was comprised by the 1st condensing lens 36 and the 2nd condensing lens 37 which are two condensing lenses of the minimum number, the condensing more than that is carried out It may be a combination of lenses.

The split mirror 33 may be provided with a mechanism such as an actuator in order to move without changing the angle between the incident laser light 5 and the vertical axis of the split mirror 33. When the split mirror 33 includes an actuator, the ratio of splitting the laser beam 5 can be freely adjusted. Therefore, one laser beam splitting device 30 can control so that the laser beam intensity of the laser beam 5 split into M beams becomes uniform.

Example 2
FIG. 9 shows an example of the configuration of a single crystal growth apparatus 100 having M reflection mirrors. As shown in FIG. 10, M reflection mirrors 80 are respectively provided between the M laser irradiation heads 50 and the raw material rod 1. In the case of this example, the distance WD between the laser irradiation head 50 and the raw material rod 1 is 160 mm, and the distance d between the laser irradiation head 50 and the M reflection mirrors 80 is 77 mm. The M reflection mirrors 80 reflect at least a part of the M heating laser beams 3. Thus, the M reflection mirrors 80 make the upper and lower irradiation light intensity distributions asymmetric in the shape of the irradiation intensity distribution of the M heating laser beams 3. For example, the shape of the irradiation intensity distribution in the Z-axis direction is adjusted to an asymmetric bell shape. Further, the M reflection mirrors 80 adjust the asymmetric shape of the irradiation intensity distribution in the Z-axis direction by adjusting the incident angles of the M heating laser beams 3 and the height of the reflection mirror 80. For example, the M reflection mirrors 80 may adjust the shape of the irradiation intensity distribution in the Z-axis direction of the M heating laser beams 3 to an irradiation intensity distribution of an asymmetric triangle or an asymmetrical polygon. The M reflection mirrors 80 are an example of M adjustment units for adjusting the shape of the irradiation intensity distribution of the M heating laser beams 3. In the second embodiment, the M adjustment units consist of five reflection mirrors 80-1 to 80-5.

The M reflection mirrors 80 may be disposed above the M heating laser beams 3. When the M reflection mirrors 80 are disposed at the top, the M reflection mirrors 80 reflect the top of the M heating laser beams 3. For example, the M reflection mirrors 80 reflect the upper portions of the M heating laser beams 3 downward in the single crystal growth apparatus 100.

The material of the M reflection mirrors 80 is not particularly limited as long as the material reflects M heating laser beams 3. In one example, the material of the M reflective mirrors 80 is silver. The reflection mirror 80 made of silver has a high reflectance of 97% or more when the wavelength of the laser light 5 is 940 nm. The material of the M reflection mirrors 80 is preferably a material which is not affected by the heat from the melting zone 4 which is at a high temperature. In addition, it is preferable that the M reflection mirrors 80 be spaced apart from the melting zone 4 so as not to be affected by the heat from the melting zone 4 which is high temperature.

Assuming that the position of the upper end of the maximum intensity Imax or the continuous maximum intensity Imax is ZU, and the position of the upward 50% irradiation intensity (0.5 × Imax) of the maximum intensity Imax is Z2.
3 mm Z Z2-ZU ≧ 0 mm
The height of the upper position and the angle of the five reflection mirrors with respect to the five heating laser beams 3 can be adjusted so that the irradiation intensity distribution in the upward direction of the Z direction is satisfied.

The single crystal growth apparatus 100 may use M absorbing materials that absorb the M heating laser beams 3 instead of the M reflecting mirrors 80 as the M adjusting units. In this case, the single crystal growth apparatus 100 may adjust the asymmetry of the irradiation intensity distribution in the Z-axis direction by adjusting the amount and height of absorption of the M absorption materials.

FIG. 11 shows the irradiation intensity distribution in the Z-axis direction of the heating laser light 3 according to the second embodiment. In this example, the irradiation intensity distribution in the Z-axis direction and the irradiation intensity distribution in the X-axis direction are respectively shown. In FIG. 11, Z = 0 is the position of the maximum intensity Imax.

The position Z2 of the upper 50% irradiation intensity (0.5 × Imax) is 3 mm. When the height H of the melting zone 4 is 4 mm, the upper end of the melting zone 4 is Z = 2 mm, which is half of H = 4 mm. The irradiation intensity becomes a steep irradiation intensity of 50% of Imax at a position 1 mm upward from the upper end of the melting zone 4. The position Z2 ′ of the upper 10% irradiation intensity (0.1 × Imax) is 4 mm. As a result, the irradiation intensity becomes zero at 2 mm upward from the upper end of the melting zone 4. Since the lower end portion of the material rod 1 can be rapidly cooled by such a temperature gradient, suction of the molten liquid into the material rod 1 is suppressed.

On the other hand, the position Z1 of the 50% irradiation intensity (0.5 × Imax) on the lower side is −6 mm. When the height H of the melting zone 4 is 4 mm, the lower end of the melting zone 4 is −2 mm. As a result, in the crystal rod 2, the irradiation intensity has an irradiation intensity of 50% of Imax at a portion of the crystal rod 2 of 4 mm from the lower end of the melting zone 4 of 6-2 = 4 mm in the Z axis. When the crystal growth rate is 4 mm / hour, the cooling time in this period is 1 hour. The position Z1 ′ of the lower 10% irradiation intensity (0.1 × Imax) is −6 mm. When the height H of the melting zone 4 is 4 mm, the lower end of the melting zone 4 is −12 mm. As a result, in the crystal rod 2, the irradiation intensity of the M heating laser beams 3 at the portion of the crystal rod 2 of 10 mm from the lower end of the melt zone 4 of Z axis of 12-2 = 10 mm is 10% of Imax. It has strength. When the crystal growth rate is 4 mm / hour, the cooling time in this period is 2.5 hours. If the crystal growth rate is 2 mm / hour, this cooling time is 5 hours. Since the upper end portion of the crystal rod 2 can be gradually cooled by such a temperature gradient, residual thermal strain on the crystal rod 2 is suppressed.

[Example 3]
FIG. 12 shows an example of the lower arrangement of the reflection mirror 80 according to the third embodiment. FIG. 13 shows the irradiation intensity distribution in the case of the lower arrangement of the heating laser light 3 according to the third embodiment. FIG. 13 shows the irradiation intensity distribution in the Z-axis direction and the irradiation intensity distribution in the X-axis direction. A rectangular shape with a length of 10 mm in the X-axis direction and a length of 10 mm in the Z-axis direction, this rectangular shaped irradiation intensity distribution arranges a mirror under the heating laser beam 3 having a uniform top hat shaped irradiation intensity distribution. . The irradiation shape at the upper end in the Z-axis direction realizes a linear sharp decrease according to the original top hat irradiation intensity distribution. The height is about 4 mm wide and has a substantially uniform intensity distribution, and then the irradiation intensity gradually decreases over the height of 6 mm. The irradiation intensity distribution in the X direction has a uniform irradiation intensity of 10 mm. By disposing M reflection mirrors 80 below the M heating laser beams 3 and utilizing the light diffraction effect, it is possible to realize a gentle irradiation intensity distribution in the downward direction of the Z axis.

Example 4
FIG. 14 shows an example of the irradiation intensity distribution before adjustment. The laser irradiation head 50 of this example includes a Z axis adjustment lens 38 and an X axis adjustment lens 39. The Z axis adjustment lens 38 and the X axis adjustment lens 39 are an example of an adjustment lens for adjusting the irradiation intensity distribution of the heating laser light 3. The laser irradiation head 50 of this example shifts the Z-axis adjustment lens 38 downward from the optical axis of the M heating laser beams 3 to generate coma. Thereby, the laser irradiation head 50 adjusts the asymmetric shape of the irradiation intensity distribution in the Z-axis direction. For example, the laser irradiation head 50 of this example is adjusted so that the downward inclination of the irradiation intensity distribution is gentle.

The Z axis adjustment lens 38 has a curvature in the Z axis direction. The laser irradiation head 50 can adjust the shape of the heating laser light 3 by adjusting the position of the Z axis adjustment lens 38. For example, the laser irradiation head 50 adjusts the asymmetric shape of the irradiation intensity distribution in the Z-axis direction by controlling the position of the Z-axis adjustment lens 38. The graph of FIG. 14 shows the irradiation intensity distribution of the heating laser beam 3 obtained when the optical axis of one Z-axis adjustment lens 38 is shifted downward. That is, the optical axis of the Z axis adjustment lens 38 is shifted downward in parallel to the optical axis of the heating laser light 3. The irradiation shape at the upper end in the Z-axis direction achieves a sharp and linear decrease. The radiation intensity decreases gently over Z = -8 mm of the Z axis.

FIG. 15 shows a simulation diagram of the irradiation intensity on the (X, Z) plane. The graph of FIG. 15 shows the irradiation intensity (%) of the heating laser light 3 in the Z-axis direction and the irradiation intensity (%) of the heating laser light 3 in the X-axis direction. The irradiation intensity (%) of the heating laser light 3 in the X-axis direction has a substantially uniform irradiation intensity with a width of ± 4 mm.

The X axis adjustment lens 39 has a curvature in the X axis direction. Thus, the laser irradiation head 50 can be adjusted to have an irradiation intensity distribution having substantially uniform irradiation intensity in the X-axis direction.

In the fourth embodiment, the irradiation intensity distribution in the predetermined Z-axis direction can be realized by changing the arrangement of the plurality of lenses constituting the laser irradiation head 50 without using the reflection mirror 80. Further, the downward inclination of the irradiation intensity distribution can be adjusted by adjusting the positions of the plurality of lenses without replacing the plurality of lenses.

[Example 5]
FIG. 16 shows an example of a method of adjusting the irradiation intensity distribution in the Z-axis direction. In the laser irradiation head 50 of this embodiment, an acute angle is formed between the Z axis of one or more adjustment lenses of the plurality of adjustment lenses and the optical axis of the M heating laser beams 3. The Z axis of one or more adjustment lenses of the plurality of adjustment lenses is rotated. By generating coma, the asymmetric shape of the first irradiation intensity distribution is adjusted. Thereby, the laser irradiation head 50 adjusts the asymmetric shape of the irradiation intensity distribution in the Z-axis direction. For example, the laser irradiation head 50 of this example is adjusted so that the downward inclination of the irradiation intensity distribution is gentle.

In the fifth embodiment, the irradiation intensity distribution in the predetermined Z-axis direction can be realized by changing the arrangement of the plurality of lenses constituting the laser irradiation head 50 without using the reflection mirror 80. Further, the downward inclination of the irradiation intensity distribution can be adjusted by adjusting the positions of the plurality of lenses without replacing the plurality of lenses.

[Example 6]
FIG. 17 shows an example of a method of adjusting the irradiation intensity distribution in the Z-axis direction. The optical axis of the heating laser beam 3 of this embodiment is inclined downward with respect to the optical axis of the laser irradiation head 50 to generate coma aberration, thereby adjusting the asymmetric shape of the first irradiation intensity distribution. Thereby, the laser irradiation head 50 adjusts the asymmetric shape of the irradiation intensity distribution in the Z-axis direction. For example, the laser irradiation head 50 of this example is adjusted so that the downward inclination of the irradiation intensity distribution is gentle.

The X axis adjustment lens 39 has a curvature in the X axis direction. As a result, the laser irradiation head 50 can be adjusted to have a substantially uniform irradiation intensity distribution in the X-axis direction.

In the sixth embodiment, the irradiation intensity distribution in the predetermined Z-axis direction can be realized by changing the arrangement of the plurality of lenses constituting the laser irradiation head 50 without using the reflection mirror 80. Further, the downward inclination of the irradiation intensity distribution can be adjusted by adjusting the positions of the plurality of lenses without replacing the plurality of lenses.

The single crystal growth apparatus 100 of the present example suppresses the narrowing of the diameter of the melting zone 4 and the increase of the diameter of the raw material rod 1 by suppressing the suction from the melting zone 4 to the raw material rod 1, and the melting zone 4. Stabilize In addition, the single crystal growth apparatus 100 of this example can relieve the residual thermal strain on the crystal rod 2 and provide a crack-free single crystal with good physical properties.

The Z-axis adjustment lens 38 shown in FIGS. 14 to 17 may be configured of a cylindrical lens or a plurality of lens groups.

In the present specification, in the second and third embodiments, the case where M reflection mirrors 80 are used as the M adjustment units has been described. However, as long as the single crystal growth apparatus 100 can adjust the irradiation intensity distribution of the M heating laser beams 3, any adjustment unit may be used. For example, the single crystal growth apparatus 100 includes, as M adjustment units, transmission preventing materials provided with slits in the vicinity of the raw material rod 1. In addition, the single crystal growth apparatus 100 may adjust the irradiation intensity distribution of the M heating laser beams 3 by the hologram method using the reflecting mirror having the concavo-convex shape. Furthermore, the single crystal growth apparatus 100 may provide an optical path difference in the M laser irradiation heads 50 and adjust the irradiation intensity distribution by an interference method using a reflecting mirror.

Further, in the fourth to fifth embodiments, the method of setting the irradiation shapes of the M heating laser beams 3 in the Z-axis direction to the asymmetric irradiation shape distribution by designing the arrangement of the lenses of the irradiation head without using the adjustment unit . In the sixth embodiment, the Z axis of the M heating laser beams 3 is arranged by inclining the optical axis of the heating laser beams 3 downward from the optical axis of the lens of the laser irradiation head 50 without using the adjustment unit. The method of making the irradiation shape of direction into the asymmetric irradiation shape distribution was described. These methods are excellent in that the adjustment section is not used and the loss of the M heating laser beams 3 can be reduced because the M heating laser beams 3 are not reflected.

As described above, the single crystal growth apparatus 100 generates M heating laser beams 3 having the following features and irradiates the raw material rods 1 and the crystal rods 2 with each other.

(1) The single crystal growth apparatus 100 generates M heating laser beams 3 in which the irradiation intensity distribution at the upper end of the crystal rod 2 gradually decreases in the Z-axis direction.

(2) The single crystal growth apparatus 100 generates M heating laser beams 3 whose irradiation intensity distribution at the lower end portion of the raw material rod 1 sharply decreases in the Z-axis direction.

(3) The single crystal growth apparatus 100 generates M heating laser beams 3 in which the irradiation intensity distribution at the upper end of the crystal rod 2 gradually decreases in the Z-axis direction, and the irradiation intensity at the lower end of the raw material rod 1 M heating laser beams 3 whose distribution sharply decreases are generated. The single crystal growth apparatus 100 may include M laser irradiation heads 50 that can easily adjust the irradiation intensity distribution.

(4) The single crystal growth apparatus 100 generates M heating laser beams 3 in which the irradiation intensity distribution at the upper end of the crystal rod 2 gradually decreases in the Z-axis direction, and the irradiation intensity at the lower end of the raw material rod 1 M heating laser beams 3 whose distribution sharply decreases are generated. The single crystal growth apparatus 100 may be provided with M reflection mirrors 80 which can easily adjust the irradiation intensity distribution.
(5) The M optical fibers 40 are fibers having a circular cross-sectional shape and can generate the M heating laser beams 3 of the irradiation intensity distribution of the above (1) to (4). The heating laser beam having an irradiation intensity distribution substantially uniform in the Z axis direction and the diameter (X direction or R direction) direction which is the central axis direction of the raw material rod 1 requires a rectangular fiber of an expensive rectangular cross section. Since circular fiber is inexpensive, the merit of cost reduction is also great.

(6) The M laser irradiation heads 50 can adjust the irradiation intensity distribution of the above (1) to (4) with a small number of lenses. This reduces the cost of the M laser irradiation heads 50. In addition, the size of the M laser irradiation heads 50 can be reduced, and the apparatus size of the single crystal growth apparatus 100 can also be reduced. For example, the apparatus size of the single crystal growth apparatus 100 is about 1100 mm in width and about 1100 mm in depth with respect to the conventional apparatus size of 1400 mm in width and 1600 mm in depth.

(7) The single crystal growth apparatus 100 can monitor the temperature of a small region of about 0.5 mmφ in radius of the melting zone 4 during crystal growth. Thereby, the temperature of the melting zone 4 can be accurately controlled, and a technique for stably growing a single crystal is provided. In addition, the temperature of the region at the upper end of the growing crystal rod 2 can be monitored during crystal growth. As a result, the reproducibility of setting of the melting temperature at the time of single crystal growth can be secured, the cooling rate of the crystal rod 2 can be monitored, and an important production technique for producing high quality single crystals is provided.

(8) The M heating laser beams 3 are formed by two power supplies 10 and one laser beam splitting device 30. The conventional apparatus requires five power supplies and five laser light sources for five heating laser beams 3. It is necessary to supply five cooling waters to five laser light sources. In the case of a single crystal growth apparatus 100 having one laser beam splitting device 30, two power supplies 10 may be sufficient. A single wattage semiconductor laser may be prepared for the main body laser. As a result, it is possible to reduce the cost of an expensive laser light source which costs several million yen per unit. The semiconductor laser requires a water cooling mechanism and dry air. The cooling water to the five laser light sources does not require complicated adjustments such as five water distribution and five return water flow adjustment. In particular, the temperature of the return water can not be controlled individually by the five diodes. Five chillers are required to individually control the temperature of the five laser light sources. The inability to ensure the accuracy of the cooling temperature of the laser light source greatly affects the stability and repeatability of the output intensity of the laser light. The output intensity dependency of the temperature of the semiconductor diode that generates laser light is large. It also eliminates the need for complex piping of dry gas to prevent water adhesion of the laser light source. In this way, the number of necessary peripheral devices can be drastically reduced, leading to a great cost advantage. The single crystal growth apparatus 100 enables control of one laser light source 20 with high temperature accuracy, and improves the temperature dependency of the irradiation intensity of the M heating laser beams 3.

Moreover, the method of dividing | segmenting by one set of laser beam splitter 30 can suppress easily the dispersion | variation in five irradiation lights. It can be adjusted to about 5%. In the case of a plurality of laser beams, there are individual differences in semiconductor laser characteristics. For this reason, it is difficult to suppress the variation of the heating laser light to 10% or less. Also, the amount of variation changes with time of use. As described above, in the case of using a large number of semiconductor lasers, variation in the characteristics can not be suppressed and a serious problem occurs in crystal production. Even if the uniformity in the X-axis direction of the raw material rod 1 is secured, the variation of the irradiation intensity can not be reduced to the original irradiation intensity distribution. In the single crystal growth apparatus 100 of this example, one laser light source 20 is divided by one laser light dividing device 30, so that in principle there is no variation in the irradiation intensity of the M heating laser beams 3 There will be no variation due to aging.

As described above, the heating laser light single crystal growth apparatus 100 has a feature that is not found in the conventional laser heating method having the irradiation intensity distribution of the top hat irradiation intensity. That is, the single crystal growth apparatus 100 can significantly reduce the thermal strain on the grown single crystal. Being able to control the cooling time to the grown crystal while considering the crystal growth time is an essential technology for single crystal growth. The heating laser method having the irradiation intensity distribution of the irradiation intensity distribution of the conventional top hat irradiation shape can not avoid the rapid cooling environment of the obtained crystal rod 2. It is obvious to apply a large residual strain to the crystal rod 2, and it has very serious problems in the crystal preparation technology.

The heating laser light type single crystal growth apparatus 100 can significantly reduce the thermal strain on the grown single crystal and, at the same time, can suppress the suction of the melt into the raw material rod. Thereby, the thermal strain to the grown single crystal can be greatly reduced without impairing the stability of the melting zone.

Although the present invention has been described using the embodiment, the technical scope of the present invention is not limited to the scope described in the above embodiment. It is apparent to those skilled in the art that various changes or modifications can be added to the above embodiment. It is also apparent from the scope of the claims that the embodiments added with such alterations or improvements can be included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Raw material stick | rod 2. Crystal rod 3 Heating laser beam 4 Melting zone 5 Laser beam 6 Quartz tube 10 Power source 20 ... Laser light source, 25 ... Heat sink, 30 ... Laser beam splitting device, 31 ... Y direction collimator, 32 ... X direction collimator, 33 ... Split mirror, 36 ... First Condenser lens 37: second condenser lens 38: Z-axis adjustment lens 39: X-axis adjustment lens 40: optical fiber 50: laser irradiation head 60 ... Damper, 70-1 ... Radiation thermometer, 70-2 ... Radiation thermometer, 80 ... Reflection mirror, 100 ... Single crystal growth device, 500 ... Single crystal growth device, 501: Raw material rod, 502: Crystal rod, 503: Heating laser beam, 504: Melting zone, 5 0 ... optical fiber, 550 ... laser irradiation head

Claims

A raw material rod extending along the first direction with the vertical direction as the first direction;
M laser irradiation heads provided radially around the raw material rod and irradiating the raw material rods with M heating laser beams;
The irradiation intensity distribution of the M heating laser beams in a two-dimensional plane orthogonal to the optical axis of the heating laser light has a first irradiation intensity distribution predetermined in the first direction, and The second radiation intensity distribution in the second direction orthogonal to the one direction has a substantially uniform radiation intensity,
In the first irradiation intensity distribution, the position of the lower end of the maximum intensity Imax or the continuous maximum intensity Imax is ZL, and the position of the 50% irradiation intensity (0.5 × Imax) below the maximum intensity Imax is Z1. Then,
ZL-Z1 2 2 mm
A single crystal growth system.
The single crystal growth apparatus according to claim 1, wherein the first irradiation intensity distribution has a bell-shaped irradiation intensity distribution.
The single crystal growth apparatus according to claim 1, wherein the first irradiation intensity distribution has a linear or polygonal irradiation intensity distribution.
The single radiation intensity distribution according to claim 1, wherein the first radiation intensity distribution comprises a combination of a part of a bell-shaped radiation intensity distribution and a part of a linear or polygonal radiation intensity distribution. Crystal growth device.
The single crystal growth apparatus according to any one of claims 1 to 4, wherein the first irradiation intensity distribution has an asymmetrical irradiation intensity distribution in the upper direction and the lower direction in the first direction.
The single crystal growth apparatus according to claim 5, wherein the first irradiation intensity distribution has a gradient in which the irradiation intensity in the upward direction decreases is larger than a gradient in which the irradiation intensity in the downward direction decreases.
The first irradiation intensity distribution is
Assuming that the position of the upper end portion of the maximum intensity Imax or the continuous maximum intensity Imax is ZU, and the position of the upper 50% irradiation intensity (0.5 × Imax) of the maximum intensity Imax is Z2.
3 mm Z Z2-ZU ≧ 0 mm
The single crystal growth apparatus according to any one of claims 1 to 6.
The M adjustment units provided between the M laser irradiation heads and the raw material rod and adjusting the irradiation intensity distribution of the M heating laser beams irradiated from the M laser irradiation heads are further provided. An apparatus for growing a single crystal according to any one of claims 1 to 7, comprising.
The M adjustment units are M reflection mirrors that adjust the irradiation intensity distribution of the M heating laser beams by reflecting at least a part of the M heating laser beams. The single crystal growth apparatus of description.
The single crystal growth apparatus according to claim 9, wherein the M reflection mirrors are provided at the upper or lower part of the first irradiation intensity distribution.
The M adjustment units are M absorption materials that adjust the irradiation intensity distribution of the M heating laser beams by absorbing at least a part of the M heating laser beams. The single crystal growth apparatus of description.
The single crystal growth apparatus according to claim 11, wherein the M absorption materials are provided at the upper or lower part of the first irradiation intensity distribution.
The single crystal growth apparatus according to any one of claims 1 to 12, wherein the M laser irradiation heads are an odd number.
The single crystal growth apparatus according to any one of claims 8 to 12, wherein the M adjustment units are an odd number.
One laser light source for irradiating one laser beam,
One laser beam splitting device for splitting the one laser beam into M beams;
And M optical fibers for emitting the M laser beams incident from the one laser beam splitting device as M heating laser beams.
The M laser irradiation heads for forming the M heating laser beams from the M optical fibers into a predetermined irradiation intensity distribution have a relationship of M> 1. The single crystal growth apparatus described in.
The single crystal growth apparatus according to any one of claims 1 to 15, wherein the M laser irradiation heads include a plurality of lenses.
The plurality of lenses include one or more lenses having a curvature in the Z-axis direction,
By generating a coma aberration as an optical axis arrangement in which the optical axes of the M heating laser beams are inclined downward with respect to the optical axes of one or a plurality of lenses having a curvature in the Z axis direction, The single crystal growth apparatus according to claim 16, wherein the asymmetric shape of the first irradiation intensity distribution is adjusted.
The plurality of lenses includes one or more adjustment lenses having a curvature in the Z-axis direction,
17. The single crystal growth device according to claim 16, wherein the plurality of lenses adjust the asymmetric shape of the first irradiation intensity distribution by controlling the positions of the one or more adjustment lenses.
The first irradiation intensity distribution by causing the plurality of lenses to shift the optical axes of the one or more adjustment lenses downward with respect to the optical axes of the M heating laser beams to generate a coma aberration The single crystal growth apparatus according to claim 18, wherein the asymmetric shape of is adjusted.
The plurality of lenses have an acute angle formed by the Z axis of the one or more adjustment lenses and the optical axes of the M heating laser beams, and the Z axis of the one or more adjustment lenses is The single crystal growth apparatus according to claim 18, wherein the asymmetry shape of the first irradiation intensity distribution is adjusted by rotating the light source to generate coma aberration.
The single crystal growth device according to any one of claims 18 to 20, wherein the plurality of adjustment lenses are cylindrical lenses or a plurality of lens groups.
The M laser irradiation heads are
Let S be the crystal growth rate,
In bell-shaped irradiation intensity distribution of the first direction, when the irradiation intensity of the width of 10% of the maximum value and Z 0, the height of the first direction of the melting zone in which the feed rod is melted and H ,
(Z 0 -H) / 2 ≧ S
The single crystal growth apparatus according to any one of claims 16 to 21, wherein the plurality of lenses are arranged to satisfy the following.
The M laser irradiation heads are
Let L be the width of the substantially uniform irradiation intensity distribution in the second direction of the M heating laser beams,
When the diameter of the raw material rod is D,
L D D
The single crystal growth apparatus according to any one of claims 16 to 22, wherein the plurality of lenses are arranged to satisfy the following.
The laser beam splitting device
A collimator lens for converting the one laser beam from the one laser light source into parallel light;
A plurality of split mirrors for splitting the one laser beam into M laser beams;
The single crystal growth apparatus according to claim 15, further comprising: a condensing lens that condenses the M laser beams onto the M optical fibers.
The radiation rod further includes a radiation thermometer which measures the temperature of the melting zone by measuring the intensity of light emitted from the melting zone where the raw material rod is melted.
The single crystal growth apparatus according to any one of claims 1 to 24, wherein the irradiation intensity of the M heating laser beams is controlled by the output of N power supplies provided to satisfy N <M.
The radiation rod further includes a radiation thermometer that measures the temperature of the crystal rod by measuring the intensity of light emitted from the crystal rod grown from the raw material rod.
The single crystal growth apparatus according to any one of claims 8 to 14, wherein the M adjustment units are adjusted based on the measured temperature of the radiation thermometer.
The cross-sectional shape of the M optical fibers has an oval cross-sectional shape made of at least one combination of a circular cross-sectional shape, an elliptical cross-sectional shape, a rectangular shape, and a shape combining these shapes. The single crystal growth apparatus according to one aspect.
The shape of the irradiation intensity distribution of the M heating laser beams in a two-dimensional plane orthogonal to the optical axis of the heating laser beam has a circular shape, an elliptical shape, a rectangular shape, or at least a shape combining some of these shapes. 28. The single crystal growth device according to any one of claims 1 to 27, having an oval shape including one shape.
Prepare a raw material rod that extends in the vertical direction,
The raw material rods are irradiated with M heating laser beams using M laser irradiation heads provided radially about the raw material rod;
The irradiation intensity distribution of the M heating laser beams in a two-dimensional plane orthogonal to the optical axis of the heating laser light has a first irradiation intensity distribution determined in advance with the vertical direction as a first direction, And, the second irradiation intensity distribution in the second direction orthogonal to the first direction has a substantially uniform irradiation intensity,
In the first irradiation intensity distribution, the position of the lower end of the maximum intensity Imax or the continuous maximum intensity Imax is ZL, and the position of the 50% irradiation intensity (0.5 × Imax) below the maximum intensity Imax is Z1. Then,
ZL-Z1 2 2 mm
How to grow single crystals.
The method for growing a single crystal according to claim 29, wherein the first irradiation intensity distribution is such that the gradient of decreasing the irradiation intensity in the upward direction is larger than the gradient of decreasing the irradiation intensity in the downward direction.
The first irradiation intensity distribution is
Assuming that the position of the upper end portion of the maximum intensity Imax or the continuous maximum intensity Imax is ZU, and the position of the upper 50% irradiation intensity (0.5 × Imax) of the maximum intensity Imax is Z2.
3 mm Z Z2-ZU ≧ 0 mm
A method of growing a single crystal according to claim 29 or 30.
The shape and the irradiation intensity of the first irradiation intensity distribution are adjusted by adjusting an interval and a focal length of a plurality of lenses of the M laser irradiation heads, according to any one of claims 29 to 31. Of growing single crystals.
The asymmetric shape of the first irradiation intensity distribution is adjusted by adjusting the incident angles and heights of M reflection mirrors of the M adjustment units, according to any one of claims 29 to 32. Of growing single crystals.
The asymmetric shape of the first irradiation intensity distribution is adjusted by adjusting the absorption amounts and heights of M absorption materials of the M adjustment units, according to any one of claims 29 to 33. Of growing single crystals.
The M laser irradiation heads and the M adjustment units are
The gradient of the downward irradiation intensity distribution in the first irradiation intensity distribution is reduced according to the increase in the moving speed of the crystal rod,
The method for growing a single crystal according to any one of claims 29 to 34, wherein the gradient of the downward irradiation intensity distribution in the first irradiation intensity distribution is increased according to the decrease in the moving speed of the crystal rod. .
Measuring the intensity of radiant light emitted from the melting zone where the raw material rod is melted;
The input power of N power supplies provided to satisfy N <M is controlled to irradiate the M heating laser beams according to the measured radiant light intensity. The method of growing a single crystal according to any one of
Measure the emitted light intensity emitted from the crystal rod,
The M adjustment units are controlled to adjust the downward irradiation intensity distribution of the M heating laser beams according to the measured radiant light intensity. Of growing single crystals.