TWI596242B - Measurement method of gap between liquid level of raw material melt and lower end of seed, preheating method of seed and manufacturing method of single crystal - Google Patents

Description

Method for determining the interval between the liquid level of the raw material melt and the lower end of the seed crystal, and the preheating method of the seed crystal Method and method for manufacturing single crystal

The present invention relates to a method for measuring a gap between a liquid surface of a raw material melt for culturing a single crystal and a lower end of a seed crystal, a preheating method for seed crystals, and a method for producing a single crystal.

As a manufacturing method of a single crystal, there is a Czochralski method (hereinafter referred to as "CZ method"). In the CZ method, a seed crystal composed of a single crystal is placed on the crucible to be contained in the crucible, and the seed crystal is brought close to the crucible, and the crystal is contacted with the crucible and then pulled upward. Crystallization is carried out to grow monocrystalline crystals under seed crystals. When the seed crystal is to be in contact with the mash, if the temperature difference between the lower end of the seed crystal and the liquid surface of the mash is large, the crystallization of the seed crystal will result in a high density difference due to thermal stress.

The difference can be reduced by the Dash neck method. However, although the frequency is low but has a certain frequency, the difference is left in the center of the crystal (hereinafter, the residual difference is referred to as "axial difference"). In order to reduce the occurrence frequency of the axial difference row, it is necessary to reduce the difference in the density of crystallization before the Dars necking. It is effective to reduce the density of the difference rows which are produced when the crystals have been in contact with the mash.

Therefore, it is preferable to first bring the temperature of the lower end of the seed crystal before the mash to be brought close to the temperature of the liquid surface of the mash. When the seed crystal is placed above the mash, the seed crystal is heated by the radiant heat from the mash. Therefore, the temperature of the seed crystal is higher as the seed crystal is closer to the melt. Therefore, in order to reduce the temperature difference between the lower end of the seed crystal and the liquid surface of the mash, it is effective to arrange the seed crystal at a position close to the liquid surface of the mash and to preheat it.

[First technical literature] [Patent Literature]

[Patent Document 1] JP-A-2005-170773

However, the interval between the liquid surface of the mash and the lower end of the seed crystal (hereinafter referred to as the "interval of crystallization") cannot be correctly measured first. When the crystal is to be preheated, the operator adjusts the relative by visual adjustment. The height of the seed crystal at the surface of the liquid of the sputum is such that the interval under the crystallization becomes the target interval. Therefore, at the time of preheating the crystallization, the interval under crystallization does not actually become the target interval. Moreover, the deviation from the interval of the target spaced apart under the crystal is successively different. Along with this, the temperature of the seed crystal at the time point after the end of the preheating is also different. As a result, when the seed crystal is brought into contact with the liquid surface of the raw material melt, the difference between the temperature of the lower end of the seed crystal and the temperature of the liquid surface of the raw material melt becomes large, and even if the difference is reduced by the Darth necking method, In the row, the shaft-like difference row remains in the crystallization.

In addition, if the interval between the targets is not accurately measured and the interval between the targets is not accurately measured, for example, it is set to 3 mm or less, and the crystals are unexpected. Contact with raw material melt. At this time, the seed crystal is not sufficiently preheated, and the seed crystal is in contact with the raw material melt in a state where the temperature difference between the raw material melt liquid surface and the seed crystal lower end is large, so that a high density difference is generated in the seed crystal, and the axis remains in the crystal. The possibility of a difference is higher.

Therefore, in order to suppress the difference in the temperature difference between the liquid level of the raw material melt and the lower end of the seed crystal, it is necessary to accurately measure the interval under the crystal.

Patent Document 1 discloses an apparatus for adjusting a starting position in the vertical direction of a liquid level of a raw material melt before culturing a single crystal in a single crystal produced by a CZ method. In this device, there is a detection device for detecting the distance from the reference position to the liquid level of the raw material melt. However, with this detecting device, the distance from the reference position to the liquid level of the raw material melt is detected by contacting the raw material melt with the crystal. Therefore, the interval between the single crystal and the raw material melt cannot be known until the single crystal is contacted with the raw material melt.

The present invention has been made in view of such circumstances, and an object thereof is to provide a method for accurately measuring the interval between a raw material melt liquid surface and a seed crystal lower end before a single crystal is brought into contact with a raw material melt liquid surface.

Another object of the present invention is to provide a preheating method which can improve the reproducibility of the temperature of the seed crystal after preheating.

Still another object of the present invention is to provide a method for producing a single crystal which can suppress introduction of a difference row.

The present invention is based on the following method (1) of measuring the distance between the raw material melt liquid surface and the seed crystal lower end, the following (2) seed crystal preheating method, and the following (3) single crystal production method.

(1) A method for measuring the interval, wherein the lower end of the seed crystal is brought into contact with the raw material melt in the crucible, and the liquid surface of the raw material melt is measured and disposed in the raw material melt before the single crystal is grown at the lower end of the seed crystal. a method for spacing the lower ends of the crystals above, wherein: by optical means, the position information of the end points of the real image and the position information of the mirror points are obtained, and the lower end point of the real image is a specific point at the lower end of the single crystal, The mirror point is a point corresponding to the lower end point of the real image on the mirror image of the crystal of the liquid level reflected on the liquid surface; and the point at which the position of the end point of the real image coincides with the position of the mirror point is the liquid of the raw material melt The distance between the surface and the lower end of the above-mentioned crystal was 0, and the distance between the liquid surface of the raw material melt and the lower end of the seed crystal was determined.

(2) A method of preheating a seed crystal, wherein a seed crystal is disposed above a liquid surface of a raw material melt for cultivating a single crystal, and a method of preheating the seed crystal comprises: by (1) The method for measuring the interval, the step of measuring the distance between the liquid surface of the raw material melt and the lower end of the seed crystal; and eliminating the difference between the interval after the measurement at the measurement interval and the target interval, and a step of moving at least one of the above enthalpy; and a step of preheating said crystallization after said step of moving.

(3) A method for producing a single crystal, comprising: a step of preheating seed crystals by a preheating method of the seed crystal of the above (2); and after the preheating step, the crystal of the above species is At least one movement of the above-mentioned crucible causes the above-mentioned crystal to contact the raw material melt contained in the crucible And a step of moving at least one of the above-mentioned crystals and the above-mentioned ruthenium to grow a single crystal at a lower end of the seed crystal after the contacting step.

According to the interval measuring method of the present invention, the interval between the liquid level of the raw material melt and the lower end of the seed crystal can be accurately measured before the seed crystal contacts the liquid surface of the raw material melt. Further, by the preheating method of the present invention, the reproducibility of the temperature of the seed crystal after preheating can be improved.

1‧‧‧ raw material melt

1a‧‧‧Liquid of raw material melt

2‧‧ ‧ kinds of crystal

2L‧‧‧ the lower end of the crystal

Mirror image of 2M, 2M’‧‧ ‧ crystals

Real image of 2R, 2R'‧‧ ‧ crystals

2U‧‧‧ upper end of the mirror

3‧‧‧Image

4‧‧‧坩埚

5‧‧‧ drive

6‧‧‧ Pulling shaft

7‧‧‧ camera

L‧‧‧ interval

P1‧‧‧ real image lower end

P2‧‧‧ mirror point

△L _P ‧‧‧The distance between the endpoint and the mirror point of the real image of the image

[Fig. 1A] Fig. 1A is a view schematically showing the arrangement of the raw material melt and the seed crystal when the interval measurement method of the present invention is carried out, and shows a state in which the seed crystal leaves the molten liquid level.

[Fig. 1B] Fig. 1B is a view schematically showing a state in which the lower end of the seed crystal contacts the molten liquid level.

[Fig. 2] Fig. 2 is a view schematically showing an image of a raw material melt and seed crystals shown in Fig. 1A obliquely from above.

[Formation for implementing the invention]

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Fig. 1A is a view schematically showing the arrangement of the raw material melt and the seed crystal when the interval measurement method of the present invention is carried out, and shows a state in which the lower end of the seed crystal leaves the molten liquid surface. Figure 1B is a schematic view showing the lower end of the seed crystal after contact with the melt level of the raw material State of the map. Fig. 2 is a view schematically showing an image of a raw material melt and seed crystals shown in Fig. 1A obliquely from above.

The raw material melt 1 is housed in a crucible 4 provided in the drawing device. A kind of crystal 2 is disposed above the raw material melt 1 . For example, in the case of cultivating a single crystal, the raw material melt 1 is composed of a molten liquid of cerium, and the seed crystal 2 is composed of a single crystal of cerium.

In the pulling device, there is a camera 7. The camera 7 can be formed, for example, by a CCD camera. By the camera 7, the range of the real image 2R of the seed crystal 2 and the mirror image 2M of the seed crystal 2 which is reflected on the liquid surface 1a of the raw material melt 1 is taken (refer to Fig. 2). By this photographing, the positional information of the real image 2R of the seed crystal 2 and the positional information of the mirror image 2M of the seed crystal 2 which is reflected on the liquid surface 1a of the raw material melt 1 can be obtained.

The crystal 2 is a drawing shaft 6 that is connected to a wire or the like. The drive shaft 5 of the pulling device is connected to the pull shaft 6. The seed crystal 2 can be moved in the vertical direction via the drawing shaft 6 by the driving device 5, so that the seed crystal 2 can be approached and separated from the crucible 4. Further, by the driving amount of the driving device 5, the height position of the seed crystal 2 with respect to the reference position of the pulling device can be detected.

In the present embodiment, the crucible 4 is not substantially moved in the vertical direction with respect to the reference position of the pulling device. Therefore, the height position of the seed crystal 2 detected by the driving device 5 corresponds to the height position of the seed crystal 2 based on the height position of the crucible 4. Here, "the height position of the seed crystal 2 based on the height position of the crucible 4" (hereinafter, simply referred to as "the height position of the seed crystal 2") means that the crucible 4 and the species in the vertical direction are not necessarily required. The interval of the crystallization 2 may be a certain difference from the interval.

In the present embodiment, the lower end 2L of the seed crystal 2 is a kind of crystal 2 The whole of the lower surface. In the following description, in the video 3, a specific point located at the lower end 2L of the real image 2R is referred to as a "real image lower end point" P1, and at the upper end 2U of the mirror image 2M (a mirror image of the lower end 2L), it corresponds to the real image lower end point. The point of P1 is called "mirror point" P2. The real image lower end point P1 can be arbitrarily selected at the lower end 2L of the image 3.

When the distance L between the liquid surface 1a of the raw material melt 1 and the lower end 2L of the seed crystal 2 is measured, first, the seed crystal 2 is moved in the vertical direction by the driving device 5, and the plurality of crystals 2 are used by the camera 7 The image 3 including the real image 2R and the mirror image 2M is obtained at each height position.

Then, for each of the obtained images 3, the position on the image 3 of the end point P1 of the real image and the position on the image 3 of the mirror point P2 are obtained. In this way, the position information of the end point P1 and the position information of the mirror point P2 in the real image are obtained by the optical method.

In the video 3, the position of the end point P1 and the position of the mirror point P2 in the real image are obtained by measuring only the position corresponding to the vertical (vertical) direction of the pulling device, and the image 3 is a digital image. Delimited by the pixel unit. As shown in Fig. 1A, the real image 2R of the seed crystal 2 and the mirror image 2M of the seed crystal 2 are located at substantially symmetrical positions with respect to the liquid surface 1a of the raw material melt 1; similarly, the moving image of the seed crystal 2 after moving 2R' and mirror 2M' are located at substantially symmetrical positions with respect to the liquid surface 1a.

Then, based on the obtained information, the regression equation of the height position Z of the seed crystal 2 and the position _ZP1 of the end point P1 of the real image on the image 3 (hereinafter referred to as "real image regression type") and the height position of the seed crystal 2 are obtained. The regression equation of _Z and the position _ZP2 of the mirror point P2 on the image 3 (hereinafter referred to as "mirror regression equation"). Specifically, by one regression, the real image regression equation can be expressed as _ZP1 = a ₁ × _Z + b ₁ , and the mirror regression equation can be expressed as _ZP2 = a ₂ × _Z + b ₂ (a ₁ , b ₁ , a ₂ and b ₂ is a constant).

In the mirror 2M, since the shaking occurs due to the fluctuation of the liquid surface 1a, the position of the mirror point P2 of the image 3 is affected by this shaking. Increasing the number of times of photographing of the seed crystal 2 at different height positions or the same height position, and measuring the position of the mirror point P2 of the image 3 for each of the obtained images 3, by increasing the number of measurements, the shaking of the mirror return type can be reduced. Impact. Therefore, the number of such measurements is preferably tens of points, for example, 40 points or more.

Next, the distance ΔL _P between the end point P1 of the real image of the image 3 and the mirror point P2 when the seed crystal 2 is at an arbitrary height position _Z is obtained by ΔL _P = (P _{real -} P _mirror ).

P _real : Substituting the height position _Z into the position on the image 3 of the end point P1 under the real image in the real image regression type. That is, P _real = _ZP1 = a ₁ × _Z + b ₁ .

P _mirror : Substituting the height position _Z into the position on the image 3 of the mirror point P2 at the time of the mirror regression. That is, P _mirror = _ZP2 = a ₂ × _Z + b ₂ .

Therefore, ΔL _P = (a ₁ - a ₂ ) × _Z + (b ₁ - b ₂ ) (A)

Can be expressed as above. The distance ΔL _P can be said to be the relative position of the real image 2R based on the position information obtained by the optical method and based on the position of the mirror image 2M.

The displacement amount Δ _Z of the height position Z of the crystal 2 corresponds to the distance ΔL _P on the image 3, and is ΔL _P = (a ₁ - a ₂ ) × Δ _Z by the above formula (A).

Therefore, _{△ Z = △ L P / (} a 1 -a 2).

That is, when the distance between the end point P1 and the mirror point P2 of the real image is ΔL _P , if the height position of the seed crystal 2 is lowered by Δ _Z , the distance between the end point P1 and the mirror point P2 of the real image becomes smaller ΔL _P The amount (ΔL _P =0), the lower end 2L of the seed crystal 2 becomes the liquid surface 1a which contacts the raw material melt 1. Therefore, it can be said that the distance L between the liquid surface 1a of the raw material melt 1 and the lower end 2L of the seed crystal 2 is ΔL _P /(a ₁ - a ₂ ) before moving the seed crystal 2 . This is based on the real image regression method and the mirror regression equation. The position of the end point P1 of the real image coincides with the position of the mirror point P2, that is, when the seed crystal 2 satisfies the height position _{Z of ZP1} = _ZP2 , it is set as the raw material melt 1 The interval between the liquid surface 1a and the lower end 2L of the seed crystal 2 is 0 (refer to FIG. 1B), and the interval L is obtained.

In addition, since the movement of the real image and the movement of the mirror image are generally symmetrical, a ₁ = - a ₂ can be set. Therefore, it is also possible to set the interval L to ΔL _P /(2a ₁ ) without using a mirror regression equation which is susceptible to fluctuations in the liquid surface.

According to the above method, the subjectivity of the worker can be excluded, and the liquid surface 1a of the raw material melt 1 and the lower end 2L of the seed crystal 2 can be accurately measured before the lower end 2L of the seed crystal 2 contacts the liquid surface 1a of the raw material melt 1. Interval L.

At the time of preheating the seed crystal 2, the interval L between the liquid surface 1a of the raw material melt 1 and the lower end 2L of the seed crystal 2 is first determined by the above method. Then, by the driving device 5, the interval between the liquid surface 1a of the raw material melt 1 and the lower end 2L of the seed crystal 2 is such that the difference between the measured interval L and the target interval is 2 Move in the direction to eliminate this difference. Thereby, the interval between the liquid surface 1a of the raw material melt 1 and the lower end 2L of the seed crystal 2 is substantially the target interval.

Then, keep this state for example, for a few minutes. Thereby, the seed crystal 2 is preheated by receiving the radiant heat from the raw material melt 1. By crystallization each time 2 The preheating is carried out at a predetermined interval from the liquid surface 1a of the raw material melt 1, and the reproducibility of the temperature of the seed crystal 2 after the preheating can be improved. Further, if the interval between the targets is set small enough, the difference between the temperature of the lower end 2L of the seed crystal 2 and the temperature of the liquid surface 1a of the raw material melt 1 can be sufficiently narrowed, and the thermal shock when the lower end 2L contacts the liquid surface 1a can be reduced. Thereby, it is possible to suppress the introduction of the seed crystal 2 into the difference.

Further, by accurately measuring the interval between the liquid surface 1a and the lower end 2L, it is possible to avoid the unexpected contact of the seed crystal 2 with the raw material melt 1 . For example, when the seed crystal 2 is preheated, a conventional method of adjusting the distance L between the liquid surface 1a of the raw material melt 1 and the lower end 2L of the seed crystal 2 by visual observation by the operator is small as a target. In the case of 3 mm or less, for example, there is a case where the crystal 2 is in contact with the raw material melt 1 except for the unexpected one. However, according to the present invention, even when this interval is set to 3 mm or less, preheating can be performed without bringing the seed crystal 2 into contact with the raw material melt 1.

However, since the liquid level 1a of the raw material melt 1 fluctuates, and the distance between the liquid level 1a and the lower end 2L is determined, it is necessary to make the seed crystal 2 not in contact with the raw material melt 1 in consideration of the wave operation setting. The interval of the target is preferably set to 1 mm or more.

After the seed crystal 2 is preheated by the above method, the seed crystal 2 is lowered, and the seed crystal 2 is brought into contact with the raw material melt 1 contained in the crucible 4, and thereafter, the seed crystal 2 is raised to grow the single crystal to the seed crystal. The lower end, whereby a single crystal can be produced.

In the above embodiment, the crucible 4 is not moved in the vertical direction with respect to the reference position of the pulling device, but the crucible 4 may be configured to be moved up and down by the driving device. At this time, by the driving amount of the driving device, The height position of the crucible 4 relative to the reference position of the drawing device is detected; the height position of the seed crystal 2 based on the height position of the crucible 4 may be, for example, the height position of the crucible 4 detected by the driving amount of the driving device. The difference between the height positions of the seed crystals 2 detected by the driving amount of the driving device 5 is obtained.

Further, it may be configured such that the seed crystal 2 is moved relative to the reference position of the drawing device and does not move in the vertical direction. At this time, the height position of the seed crystal 2 based on the height position of the crucible 4 may be, for example, the height position of the crucible 4 detected by the driving device.

When the seed crystal 2 is preheated in the case where the crucible 4 is movable in the vertical direction, in order to eliminate the difference between the measured interval L and the target interval, the seed crystal 2 may be moved in the vertical direction, or may be made. 4 moves in the up and down direction instead of moving the seed crystal 2 in the vertical direction.

Further, when the single crystal is produced in the case where the crucible 4 can be moved in the vertical direction, the seed crystal 2 may be moved in the vertical direction, or the crucible 4 may be moved in the vertical direction instead of the seed crystal 2 in the up and down direction. In the case of moving, the seed crystal 2 is brought into contact with the raw material melt 1 to grow a single crystal under the seed crystal 2.

The raw material melt 1 and the seed crystal 2 to be used in the present invention are not limited to those composed of ruthenium, and may be composed of other materials such as ruthenium, Al ₂ O ₃ (sapphire) or a compound semiconductor material, as long as they are The mirror image 2M of the seed crystal 2 may be reflected on the liquid surface 1a of the raw material melt 1.

1‧‧‧ raw material melt

1a‧‧‧Liquid of raw material melt

2‧‧ ‧ kinds of crystal

2L‧‧‧ the lower end of the crystal

Mirror image of 2M, 2M’‧‧ ‧ crystals

Real image of 2R, 2R'‧‧ ‧ crystals

2U‧‧‧ upper end of the mirror

4‧‧‧坩埚

5‧‧‧ drive

6‧‧‧ Pulling shaft

7‧‧‧ camera

L‧‧‧ interval

P1‧‧‧ real image lower end

P2‧‧‧ mirror point

Claims (7)

A method for measuring a gap by measuring a liquid surface of the raw material melt and a substance disposed above the raw material melt before the lower end of the seed crystal is brought into contact with the raw material melt in the crucible and the single crystal is grown at the lower end of the seed crystal. The method for spacing the lower end of the crystal is characterized in that the position information of the end point of the real image and the position information of the mirror point are obtained by an optical method, and the end point of the real image is a specific point at the lower end of the crystal, the mirror image The point is a point corresponding to the lower end point of the real image in the mirror image of the crystal of the above-mentioned liquid surface; the point at which the position of the end point of the real image coincides with the position of the mirror point is the liquid level of the raw material melt The distance from the lower end of the above-mentioned crystal was 0, and the interval between the liquid surface of the raw material melt and the lower end of the seed crystal was determined. The method for measuring an interval according to claim 1, wherein at least one of the liquid levels of the raw material melt and the raw material melt in the crucible is determined by an optical method at each of a plurality of height positions. Position information of the end point of the real image and position information of the mirror point; and determining the interval between the liquid surface of the raw material melt and the lower end of the seed crystal based on the following (a) and (b): (a) The displacement amount of the height position of the crystal is obtained based on the height position of the liquid surface of the raw material melt in the crucible; (b) the displacement amount of the relative position of the real image corresponds to the displacement of the above (a) The position of the mirror image of the above-mentioned crystal is based on the position information based on the position of the mirror image of the above-mentioned crystal. The method for measuring an interval according to the second aspect of the invention, wherein the seed crystal and the liquid are photographed at a plurality of height positions with respect to a height position of the crucible containing the raw material melt in the above-mentioned crystal. And obtaining a video image including the real image and the mirror image of the crystal of the above-mentioned crystal, and obtaining the position information of the end point of the real image of the seed crystal and the position information of the mirror point on the image. The method for measuring an interval according to the second aspect of the invention, wherein the height of the above-mentioned crystal and the position of the lower end of the real image are a regression equation of the real image and the height position of the crystal and the mirror point. The relationship between the displacement amount of the above (a) and the displacement amount of (b) is obtained by the regression equation of the position. The method for measuring an interval according to the third aspect of the invention, wherein the height of the above-mentioned crystal and the position of the lower end of the real image are a regression equation of the real image and the height position of the crystal and the mirror point. The relationship between the displacement amount of the above (a) and the displacement amount of (b) is obtained by the regression equation of the position. A preheating method for crystallization, which is a method for arranging seed crystals above a liquid surface for cultivating a single crystal raw material melt, and preheating the above crystallization, characterized in that it comprises: The method for measuring an interval according to any one of the items 5, wherein a step of measuring a distance between a liquid surface of the raw material melt and a lower end of the seed crystal is performed; and the interval between the measurement at the measurement interval and the target is determined. The difference in spacing causes at least one of the above crystallization and the above enthalpy a step of moving; and a step of preheating said crystallization after said step of moving. A method for producing a single crystal, comprising: a step of preheating crystallization by a preheating method of crystallization as described in claim 6; after the preheating step, the crystallization is performed At least one movement of the ruthenium, the step of contacting the seed crystal with the raw material melt contained in the crucible; and after the contacting step, moving at least one of the seed crystal and the crucible to form a single crystal in the crystal The steps to grow at the bottom.