KR102461073B1 - Silicon single crystal growth method - Google Patents

Abstract

(Project) To provide a method for growing a silicon single crystal capable of growing a defect-free crystal with high accuracy in consideration of the effect of stress acting on the single crystal during single crystal growth.
(Solution) A single crystal growing apparatus in which a water cooling body 11 surrounding the single crystal 8 during growth is disposed, and a heat shield 10 surrounding the outer peripheral surface and the lower end surface of the water cooling body 11 is disposed. and a gap variable control for pulling up a single crystal while changing the gap between the liquid level of the raw material melt 9 and the heat shield 10, and in the direction of the pulling axis in the vicinity of the solid-liquid interface at the center of the single crystal 8 When the temperature gradient is G _c , and the temperature gradient in the pulling axis direction in the vicinity of the solid-liquid interface of the outer periphery of the single crystal 8 is Ge , A = 0.1769 × G _c + _0.5462 , 0.9 × A ≤ G _c /G _e The single crystal (8) is pulled under the condition that ≤ 1.1 × A is satisfied.

Description

Silicon single crystal growth method

The present invention relates to a method for growing a silicon single crystal by the Czochralski method (hereinafter referred to as the "CZ method"), and in particular, OSF (Oxidation Induced Stacking Fault: Oxidation Induced Stacking Fault), COP (Crystal Originated Particle) ), and to a method for growing a defect-free crystal in which point defects such as infrared scatterer defects such as LD (Interstitial-type Large Dislocation) and dislocation clusters do not occur.

Most of the silicon single crystals used as substrate materials for semiconductor devices are manufactured by the CZ method. In the CZ method, in a chamber maintained in an inert gas atmosphere under reduced pressure, seed crystals are immersed in a silicon raw material melt stored in a quartz crucible, and the immersed seed crystals are gradually pulled up. Thereby, a silicon single crystal is grown continuously at the lower end of the seed crystal.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram explaining the situation which various defects generate|occur|produce based on the Voronkov theory. As shown in the figure, in the Boronkov theory, when the pulling speed is V (mm/min) and the temperature gradient in the pulling axis direction in the vicinity of the solid-liquid interface of the ingot (silicon single crystal) is G (°C/mm) , V/G, which is their ratio, is taken on the horizontal axis, and the concentration of vacancy-type point defects and the concentration of interstitial silicon-type point defects are taken on the same vertical axis, and the relationship between V/G and the point defect concentration is schematically expressed. Also, it is explained that a boundary exists between a region in which vacancy-type point defects occur and a region in which interstitial silicon-type point defects occur, and that the boundary is determined by V/G. Hereinafter, "temperature gradient in the pulling axis direction" may be simply described as "temperature gradient".

A vacancy-type point defect is a vacancy from which the silicon atom which should constitute a crystal lattice is missing, and a representative representative of the aggregate of this vacancy-type point defect is COP. The interstitial silicon-type point defect has a source of interstitial silicon into which silicon atoms have penetrated between the crystal lattices, and LD is a representative representative of the aggregate of this interstitial silicon-type point defect.

As shown in FIG. 1, when V/G exceeds a critical point, the single crystal in which the vacancy-type point defect prevailed will grow. On the other hand, when V/G is lower than the critical point, a single crystal in which interstitial silicon-type point defects predominate is grown. For this reason, in the range where V/G is less than (V/G) ₁ , which is smaller than the critical point, the interstitial silicon-type point defects dominate in the single crystal, and the region [I] in which aggregates of interstitial silicon-type point defects exist. appears, and LD occurs. In the range where V/G is larger than (V/G) ₂ , which is larger than the critical point, vacancy point defects dominate in the single crystal, and a region [V] in which aggregates of vacancy point defects exist appears, and COP occurs. do.

In the range where V/G is the critical point to (V/G) ₁ , the defect-free region [ _PI ] in which interstitial silicon-type point defects do not exist as aggregates in the single crystal is in the range from the critical point to (V/G) ₂ A defect-free region [P _V ] in which vacancy-type point defects do not exist as aggregates in the single crystal appears, and neither COP nor LD defects including OSF occur. Here, the defect-free region [P _I ] and [P _V ] are collectively referred to as the defect-free region [P]. An OSF region forming an OSF nucleus exists in the region [V] (the range in which V/G is (V/G) ₂ to (V/G) ₃ ) adjacent to the defect-free region [P _V ].

Fig. 2 is a schematic diagram showing the relationship between the pulling rate and defect distribution at the time of single crystal growth. As for the defect distribution shown in the same figure, a silicon single crystal is grown while gradually decreasing the pulling speed V, and the grown single crystal is cut along a central axis (pulling axis) to obtain a plate-shaped specimen, Cu is attached to the surface, and heat treatment is performed. After carrying out, the result of observing the plate-shaped specimen by the X-ray topography method is shown.

As shown in FIG. 2 , when growth is performed at a high pulling speed, a region [V] in which aggregates (COP) of vacancy-type point defects exist is generated over the entire area in a plane orthogonal to the pulling axis direction of the single crystal. . When the pulling speed is decreased, an OSF region appears in a ring shape from the outer periphery of the single crystal. The OSF region gradually decreases in diameter as the pulling rate decreases, and disappears when the pulling rate becomes V ₁ . In connection with this, a defect-free region [P] (region [P _V ]) appears in place of the OSF region, and the entire in-plane area of the single crystal is occupied by the defect-free region [P]. Then, when the pulling rate is lowered to V ₂ , a region [I] in which aggregates (LD) of interstitial silicon-type point defects exist appears, eventually replacing the defect-free region [P] (region [P _I ]). Thus, the entire in-plane area of the single crystal is occupied by the region [I].

These days, with the development of miniaturization of semiconductor devices, the quality required for silicon wafers is higher and higher. For this reason, in the production of a silicon single crystal, which is a material of a silicon wafer, various point defects such as OSF, COP, and LD are excluded, and a technique of cultivating a defect-free crystal in which a defect-free region [P] is distributed throughout the plane is not strongly demanded.

In order to meet this demand, when pulling a silicon single crystal, as shown in Figs. 1 and 2 above, V/G in the hot zone spreads throughout the plane, so that agglomerates of interstitial silicon-type point defects do not occur. As the first critical point (V/G) ₁ or more, it is necessary to manage so as to ensure that it is below the second critical point (V/G) ₂ at which the aggregate of vacancy-type point defects does not occur. In actual operation, the target of the pulling speed is set between V ₁ and V ₂ (for example, the median of both), and even if the pulling speed is changed during growth, it is in the range of V ₁ to V ₂ (“pulling speed margin” or It is called “PvPi margin”).

In addition, since the temperature gradient G depends on the dimension of the hot zone in the vicinity of the solid-liquid interface, the hot zone is appropriately designed in advance prior to single crystal growth. Generally, a hot zone is comprised with the water cooling body arrange|positioned so that the single crystal|crystallization under growth may be surrounded, and the heat shield body arrange|positioned so that the outer peripheral surface and the lower end surface of this water cooling body may be surrounded. Here, as the management index in designing the hot zone, the temperature gradient G _c at the central portion of the single crystal and the temperature gradient G _e at the outer periphery of the single crystal are used. And, in order to grow a defect-free crystal, for example, in the technique disclosed in Patent Document 1, the difference ΔG (=G _e - G _c ) between the temperature gradient G _c at the center of the single crystal and the temperature gradient _Ge at the outer periphery of the single crystal is 0.5° C. /mm or less.

However, in recent years, it has been found that V/G, that is, critical V/G, which should be targeted in the growth of a defect-free crystal varies depending on the stress acting in the single crystal at the time of growth of the single crystal. For this reason, in the technique disclosed by the said patent document 1, since the effect of the stress is not considered at all, the situation in which a perfect defect-free crystal|crystallization is not obtained arises quite a bit.

In this regard, for example, in Patent Document 2, a single crystal having a diameter of 300 mm or more is a target for growth, and in consideration of the effect of stress in the single crystal, the temperature gradient G _c at the center of the single crystal and the temperature gradient G _e at the outer periphery of the single crystal A technique for making the ratio (hereinafter, also referred to as “temperature gradient ratio”) G _c /G _e larger than 1.8 is disclosed. However, in the technique disclosed by patent document 2, even if the effect of the stress in a single crystal is considered, it cannot necessarily be said that the perfect defect-free crystal|crystallization is obtained. This is considered to be due to an insufficient control range of the temperature gradient ratio G _c /G _e .

Japanese Laid-Open Patent Publication No. 11-79889 Japanese Patent Publication No. 4819833

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a method for growing a silicon single crystal capable of growing a defect-free crystal with high precision in consideration of the effect of stress acting in the single crystal during single crystal growth. do.

In order to achieve the above object, the present inventors paid attention to the stress acting in a single crystal at the time of single crystal growth, performed numerical analysis in which this stress was added, and intensively studied. As a result, the following knowledge was obtained.

3 is a diagram showing the relationship between stress σ _mean and critical V/G acting in a single crystal. As a result of investigating the relationship between critical V/G and average stress σ _mean by comprehensive thermal analysis in which the conditions of the hot zone were changed in various ways, as shown in FIG. 3 , (critical V/G) = 0.17 + 0.0013 × σ _mean found out that

The distribution of stress in the vicinity of the solid-liquid interface of a single crystal has regularity, and the distribution of the in-plane stress can be grasped by the stress or temperature gradient limited to the center of the single crystal. As a result, by considering the effect of the stress in the single crystal and determining the temperature gradient at the center of the single crystal or the stress at the center of the single crystal, the optimum distribution of the in-plane temperature gradient for growing defect-free crystals, and furthermore, the optimum temperature gradient ratio It becomes possible to grasp G _c /G _e . And, by using the optimal temperature gradient ratio G _c /G _e as a management index, it is possible to design the appropriate dimensions of the hot zone, and furthermore, based on the optimal temperature gradient ratio G _c /G _e , By setting the management range, it becomes possible to grow defect-free crystals with high precision.

The present invention has been completed based on the above findings, and is a method for growing a silicon single crystal by the CZ method in which a single crystal having a diameter of 300 mm or more is pulled from a melt of a raw material in a crucible disposed in a chamber. A single crystal growing device in which a cooling body is disposed and a heat shield surrounding the outer circumferential surface and the lower end surface of the water cooling body is used is used, and the gap between the liquid level of the raw material melt and the heat shield disposed above the raw material melt is used. a gap variable control for _pulling the single crystal while changing When the temperature gradient of G _e , A = 0.1769 × G _c + 0.5462, 0.9 × A ≤ G _c /G _e ≤ 1.1 × A The single crystal is pulled under the condition that it is satisfied.

According to the conventional knowledge, in order to widen the pulling rate margin at which a defect-free crystal can be obtained, it is thought that it is better to make the in-plane distribution of the temperature gradient in the crystal uniform anyway. However, according to the new knowledge of the present inventors, it became clear that a pulling-up speed margin cannot be expanded unless it is set as the in-plane distribution of the temperature gradient in a crystal|crystallization according to the stress state in a crystal|crystallization. According to the present invention, since the control range of the temperature gradient ratio G _c /G _e is appropriately set in consideration of the effect of stress in the single crystal, it becomes possible to grow a defect-free crystal from the top to the bottom of the single crystal with high accuracy. Further, by using the single crystal produced by the present invention, it becomes possible to efficiently manufacture a high-quality wafer having a diameter of 300 mm or 450 mm. In addition, when the diameter of the wafer is 300 mm, it is preferable that the diameter of the single crystal (straight body part) be 301 mm or more and 340 mm or less, and when the diameter of the wafer is 450 mm, the single crystal (straight body part). It is preferable to set the diameter of 451 mm or more to 510 mm or less.

In the present invention, the gap variable control is obtained from the quantitative value of the crucible rising speed required for maintaining the gap, which changes with pulling of the single crystal at a constant distance, and the change in the target value of the gap. It is preferable to control the crucible rising speed using the sum of the fluctuation value of the crucible rising speed and the correction value of the crucible rising speed obtained from the difference between the target value of the gap and the actual measured value. In this control, since the role of the correction value of the crucible rising speed is specialized only for correction for eliminating the gap between the target value of the gap and the measured value, it is possible to prevent the crucible rising speed amplitude from increasing. Accordingly, it is possible to achieve stabilization of the crystal thermal history from the top to the bottom of the silicon single crystal, suppress the change in the in-plane distribution of crystal defects, and increase the production yield of the high-quality silicon single crystal.

In the present invention, it is preferable to obtain the change in the target value of the gap from a gap profile that defines the relationship between the target value of the gap and the crystal length that changes with pulling of the single crystal. Thereby, the fluctuation value of the crucible rising speed can be easily and accurately calculated|required, and the stability of the crucible rising speed can further be improved.

In this invention, it is preferable to calculate|require the said correction value from the difference between the target value of the said gap calculated|required from the said gap profile, and the measured value of the said gap. Thereby, the correction value of the crucible rising speed can be calculated|required easily and accurately, and the stability of the crucible rising speed can further be improved.

In the method for producing a single crystal according to the present invention, a decrease in the volume of the melt is obtained from an increase in the volume of the single crystal accompanying pulling up the single crystal, and the quantitative value is obtained from a decrease in the volume of the melt and the inner diameter of the crucible. it is preferable Thereby, the quantitative value of the crucible rising speed can be calculated|required simply and accurately.

In the present invention, the gap profile preferably includes at least one gap constant control section for maintaining the gap at a constant distance, and at least one gap variable control section for gradually changing the gap. In this case, the gap variable control section may be formed after the constant gap control section as the second half of the single crystal body section growing process, or formed before the constant gap control section as the first half of the single crystal body section growing process. it may be In addition, the gap profile includes first and second gap variable control sections for gradually changing the gap, and the first gap variable control section includes the gap constant control section as the first half of the single crystal body part growing process. It is preferable that the second gap variable control section is formed after the constant gap control section as the second half of the single crystal body portion growing step. Thereby, the in-plane distribution of crystal defects from the top to the bottom of the single crystal can be made substantially constant, and thereby, the production yield of a high-quality single crystal can be increased. In addition, the first half of the body part growing process means a process of producing a single crystal of the first half of the body part by dividing the total length of the body part of the single crystal into two, and the latter half of the body part growing process is a single crystal of the latter part of the body part means the manufacturing process.

In the method for producing a single crystal according to the present invention, it is preferable to calculate the measured value of the gap from the position of the mirror image of the heat shield reflected on the liquid level of the melt photographed with a camera. Thereby, the measured value of a gap can be calculated|required simply and accurately by an inexpensive structure.

According to the method for growing a silicon single crystal of the present invention, since the control range of the temperature gradient ratio G _c /G _e is appropriately set in consideration of the effect of stress in the single crystal, it is possible to grow a defect-free crystal with high accuracy. .

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram explaining the situation which various defects generate|occur|produce based on the Voronkov theory.
Fig. 2 is a schematic diagram showing the relationship between the pulling rate and defect distribution at the time of single crystal growth.
Fig. 3 is a diagram showing the relationship between stress σ _mean at the center of a single crystal and critical V/G.
4 : is a figure which exemplifies the distribution situation of the optimal in-plane temperature gradient G(r) for every temperature gradient _Gc of the center part of a single crystal.
5 is a diagram illustrating a distribution situation of an optimal temperature gradient ratio G _c /G _e according to a temperature gradient G _c at the center of a single crystal.
6 is a diagram illustrating the distribution of the optimum in-plane temperature gradient G(r) for each stress σ _{mean_c} at the center of a single crystal.
7 is a diagram illustrating a distribution situation of the optimum temperature gradient ratio G _c /G _e depending on the stress σ _{mean_c} at the center of the single crystal.
Fig. 8 is a diagram schematically showing the configuration of a single crystal growing apparatus to which the method for growing a silicon single crystal of the present invention can be applied.
9 is a graph showing the relationship between the gap H between the heat shield 10 and the liquid level of the raw melt 9 and the temperature gradient ratio G _c /G _e .
Fig. 10 is a flowchart showing a process for manufacturing a silicon single crystal.
11 is a schematic cross-sectional view showing the shape of a silicon single crystal ingot.
12 : is a schematic diagram for demonstrating the relationship between the gap profile and crystal defect distribution during a crystal pulling process, and has shown the case of the conventional constant gap control especially.
13 : is a schematic diagram for demonstrating the relationship between the gap profile and crystal defect distribution during a crystal pulling process, and has shown the case of the gap variable control of this invention especially.
It is a block diagram of the gap variable control function for demonstrating the calculation method of a crucible raising speed.

Hereinafter, an embodiment of the method for growing a silicon single crystal of the present invention will be described in detail.

1. Equation of critical V/G introducing stress effect

When growing a defect-free crystal, the target pulling speed (hereinafter also referred to as "critical pulling speed") is V _cri (unit: mm/min), and the temperature gradient in the pulling axis direction in the vicinity of the solid-liquid interface of the single crystal. When is G (unit: °C/mm), the critical V _cri /G, which is the ratio, can be defined by the following equation (1) by introducing the effect of stress acting in the single crystal at the time of single crystal growth. The vicinity of the solid-liquid interface of a single crystal here means the range where the temperature of a single crystal is from melting|fusing point to 1350 degreeC.

V _cri /G = (V/G) _σmean=0 + α × σ _mean … (One)

In the same expression, (V/G) _σmean=0 is an integer representing the critical V/G when the average stress in the crystal is zero. α is the stress coefficient, and σ _mean is the average stress (unit: MPa) in the single crystal. For example, when a single crystal having a diameter of 310 mm is used as a growth target, (V/G) _σmean=0 is 0.17, and α is 0.0013. Here, the average stress σ _mean corresponds to the stress of the component that affects the volume change of the single crystal at the time of growth, and can be grasped by numerical analysis. The vertical components σ _rr , σ _θθ , and σ _zz of the stress acting on each of the three surfaces of the surface and the surface orthogonal to the pulling axis direction are extracted, and these are summed and divided by 3. Here, positive of average stress σ _mean means tensile stress, and negative means compressive stress.

Since (V/G) _{σmean = 0} is a constant, the expression (1) above becomes the following expression (2) by substituting ξ for (V/G) _{σmean = 0} .

V _cri /G = ξ + α × σ _mean … (2)

Equation (2) above shows the relationship between the critical _Vcri /G and the average stress (σ _mean ) in one dimension, but in order to grow a defect-free crystal, it is necessary to think within a plane orthogonal to the pulling axis direction of the single crystal. .

2. Expansion of the expression of critical V/G with stress effect to in-plane distribution of single crystals

At the position of the radius r (unit: mm) from the center of the single crystal, the critical pulling speed V _cri (unit: mm/min) and the temperature gradient G(r) (unit: °C/mm) at the position of the radius r The ratio critical V _cri /G(r) can be defined by the following equation (3) according to the above equation (2) when a stress effect is introduced.

V _cri /G(r) = ξ + α × σ _mean (r) … (3)

In the same equation, σ _mean (r) is the average stress (unit: MPa) in the vicinity of the solid-liquid interface at the position of the radius r from the center of the single crystal, and represents the distribution of the average stress in the plane near the solid-liquid interface of the single crystal. From the same formula, the temperature gradient G(r) at the position of the radius r can be expressed by the following formula (4).

G(r) = V _cri /(ξ + α × σ _mean (r)) … (4)

Here, since the temperature gradient G(r) represents the distribution of the temperature gradient in the plane perpendicular to the pulling axis direction of the single crystal, in order to grow a defect-free crystal, the distribution of the optimal in-plane temperature gradient G(r) Although it wants to calculate|require, it becomes a problem that it is difficult to predict the distribution of average stress (sigma) _mean (r) in a plane. Moreover, it is also a problem that the distribution of the in-plane average stress (sigma) _mean (r) differs with conditions.

Then, the prediction method of in-plane mean stress (sigma) _mean (r) was examined.

2-1. The relationship between the temperature gradient at the center of a single crystal and the average stress (stress)

The relationship between the temperature gradient G(0) (=G _c ) at the center of a single crystal and the average stress σ _mean (0) (= σ _{mean_c} ) at the center of the single crystal was studied. This examination was performed as follows. Assuming that a single crystal with a diameter of 310 mm is grown, first, the radiant heat of the single crystal surface in each hot zone condition is calculated by comprehensive thermal analysis in which the conditions of the hot zone are changed in various ways, and then each calculated hot Radiant heat in zone conditions and variously changed solid-liquid interface shapes were used as boundary conditions, and the temperature in the single crystal in each boundary condition was recalculated. Here, as the hot zone condition change, the gap between the lower end of the heat shield surrounding the single crystal and the liquid level of the raw material melt in the quartz crucible (hereinafter also referred to as “liquid level gap”) was changed. In addition, as the condition change of the solid-liquid interface shape, the height in the pulling axis direction from the liquid level of the raw material melt to the center of the solid-liquid interface (hereinafter also referred to as "interface height") was changed. Then, for each condition, the stress (average stress) was calculated based on the distribution of the temperature in the single crystal obtained by the recalculation.

From the analysis results, the average stress σ _mean (0) (= σ _{mean_c} ) at the center of the single crystal is proportional to the temperature gradient G(0) (= G _c ) at the center of the single crystal, regardless of the interface height, between the two It was found that there is a relationship of equation (5).

σ _mean (0) = -15.879 × G(0) + 38.57 … (5)

2-2. Normalization of in-plane mean stress

Then, normalizing the distribution of the in-plane average stress σ _mean (r) was examined by the numerical analysis described above. Here, as shown by the following equation (6), the ratio n(r) of the average stress σ _mean (r) at the position of the radius r and the average stress σ _mean (0) (= σ _{mean_c} ) at the center of the single crystal is It was set as the standardized stress ratio.

n(r) = σ _mean (r)/σ _{mean_c} … (6)

As a result, it was found that the normalized stress ratio n(r) tends to be substantially the same depending on the position of the radius r, even if the liquid level Gap and the interface height are different, and can be expressed by the following equation (7).

n(r) = 0.000000524 × r ³ - 0.000134 × r ² + 0.00173 × r + 0.986 … (7)

However, in the central part (r=0) of a single crystal, since σ _mean (r) = σ _{mean_c} , n(0) is 1 from the above expression (6). At the outer periphery of the single crystal (r = e (e is, for example, 155 mm when a single crystal having a diameter of 310 mm is an object)), σ _mean (r) = 0, so n(e) is (6) ) is 0 from the equation.

Then, from said (6) Formula and said (5) Formula, in-plane mean stress (sigma) _mean (r) can be represented by following (8) Formula.

σ _mean (r) = n(r) × σ _{mean_c}

= n(r) × (-15.879 × G(0) + 38.57) … (8)

From the same formula, the distribution of the in-plane average stress σ _mean (r) can be grasped if the average stress σ _mean (0) (= σ _{mean_c} ) of the central portion of the single crystal is known, in other words, the temperature gradient G(0) of the central portion of the single crystal ) (=G _c ) can be known if it is known.

3. Derivation of distribution of optimal in-plane temperature gradient G(r)

When a single crystal having a diameter of 310 mm is used as a growth target, the in-plane temperature gradient G(r) can be expressed by the following equation (9) by substituting the above equation (8) into the above equation (4).

G(r) = V _cri /(ξ + α × n(r) × (-15.879 × G(0) + 38.57)) … (9)

Here, by examining the standardization of the distribution of the temperature gradient G(r), the ratio (G(r)/G() of the temperature gradient G(r) at the position of the radius r and the temperature gradient G(0) at the center of the single crystal 0)) as the standardized temperature gradient ratio, the following equation (10) is derived from the above equation (9).

G(r)/G(0) = [V _cri /(ξ + α × n(r) × (-15.879 × G(0) + 38.57))]/[V _cri /(ξ + α × n(0) ) × (-15.879 × G(0) + 38.57))]

= (ξ + α × n(0) × (-15.879 × G(0) + 38.57))/(ξ + α × n(r) × (-15.879 × G(0) + 38.57)) … (10)

From the same formula, the in-plane temperature gradient G(r) can be expressed by the following formula (11).

G(r) = [(ξ + α × n(0) × (-15.879 × G(0) + 38.57))/(ξ + α × n(r) × (-15.879 × G(0) + 38.57) )] × G(0) … (11)

In the formulas (10) and (11), n(0) is 1 as described above. n(r) is represented by the formula (7) above. However, as described above, n(r), ie, n(e), in the outer peripheral portion (r=e) of the single crystal is zero.

For this reason, it can be said that the distribution of the optimal in-plane temperature gradient G(r) can be grasped|ascertained using the said (11) formula by determining the temperature gradient G(0) (= _Gc ) of the central part of a single crystal.

Further, when a single crystal having a diameter of 310 mm is used as a growth target, the in-plane temperature gradient G(r) can be expressed by the above formula (4), and the normalized temperature gradient ratio (G(r)/G(0)) As , the following equation (12) is derived from the equation (4).

G(r)/G(0) = [V _cri /(ξ + α × n(r) × σ _mean (0))]/[V _cri /(ξ + α × n(0) × σ _mean (0) ))]

= (ξ + α × n(0) × σ _mean (0))/(ξ + α × n(r) × σ _mean (0)) … (12)

From the same formula, the in-plane temperature gradient G(r) can be expressed by the following formula (13).

G(r) = [(ξ + α × n(0) × σ _mean (0))/(ξ + α × n(r) × σ _mean (0))] × G(0) … (13)

In the formulas (12) and (13), n(0) is 1 as described above. n(r) is represented by the formula (7) above. However, as described above, n(r), ie, n(e), in the outer peripheral portion (r=e) of the single crystal is zero.

For this reason, it is said that the distribution of the optimal in-plane temperature gradient G(r) can be grasped using the above equation (13) by determining the average stress at the center of the single crystal, that is, the stress σ _mean (0) (= σ _{mean_c} ). can

4. Optimal range of the ratio G _c /G _e of the temperature gradient G _c at the center of the single crystal and the temperature gradient G _e at the outer periphery

When a single crystal with a diameter of 310 mm is to be grown, the optimum temperature gradient G(r) is calculated according to the position of the radius r from the center of the single crystal for each temperature gradient G _c at the center of the single crystal by Equation (11) above. If it is, the distribution situation of the in-plane temperature gradient G(r) becomes as shown in FIG. 4, for example.

4 : is a figure which exemplifies the distribution situation of the optimal in-plane temperature gradient G(r) for every temperature gradient _Gc of the center part of a single crystal. From the figure, it turns out that the distribution of the optimal in-plane temperature gradient G(r) can be grasped|ascertained by determining the temperature gradient G(0) (= _Gc ) of the central part of a single crystal.

Here, as a main management index for cultivating a defect-free crystal, there is a ratio G _c /G _e of the temperature gradient G _c at the central portion of the single crystal and the temperature gradient G _e at the outer peripheral portion of the single crystal. From the calculation result by the formula (11) above, if the optimum temperature gradient ratio G _c /G _e is calculated according to the temperature gradient G(0) (=G _c ) at the center of the single crystal, the temperature gradient ratio G _c /G _e The distribution state of is as shown in FIG. 5, for example.

5 is a diagram illustrating a distribution situation of an optimal temperature gradient ratio G _c /G _e according to a temperature gradient G _c at the center of a single crystal. The figure shows the case where a single crystal with a diameter of 310 mm is used as a growth object, ie, the case where r=e=155 mm. From the same figure, there is a correlation between the temperature gradient G _c at the center of the single crystal and the optimum temperature gradient ratio G _c /G _e (=G(0)/G(150)), and the linear equation It became clear that the relationship between

G _c /G _e = 0.1769 × G _c + 0.5462 … (14)

For this reason, by determining the temperature gradient G(0) (=G _c ) of the central portion of the single crystal, the optimum temperature gradient ratio G _c /G _e can be grasped using the above equation (14). And, since the relationship of the same (14) formula is established, if the single crystal is pulled under the condition of G _c /G _e that satisfies the following formula (a), it becomes possible to grow a defect-free crystal with high accuracy.

0.9 × A ≤ G _c /G _e ≤ 1.1 × A … (a)

In the formula (a), A is 0.1769 x G _c + 0.5462.

When the temperature gradient ratio G _c /G _e is less than “0.9×A” or exceeds “1.1×A”, the growth of the defect-free crystal becomes unstable. More preferably, the temperature gradient ratio G _c /G _e is "0.95 x A" or more and "1.05 x A" or less.

In addition, when a single crystal with a diameter of 310 mm is to be grown, the optimum temperature gradient G(r) according to the position of the radius r from the center of the single crystal for each stress σ _{mean_c} at the center of the single crystal is obtained by the equation (13) above. If calculated, the distribution state of the in-plane temperature gradient G(r) will be as shown in FIG. 6, for example.

6 is a diagram illustrating the distribution of the optimum in-plane temperature gradient G(r) for each stress σ _{mean_c} at the center of a single crystal. The figure shows that the optimal distribution of in-plane temperature gradient G(r) can be grasped|ascertained by determining the stress σ _mean (0) (= σ _{mean_c} ) at the center of the single crystal.

Here, there exists a temperature gradient ratio _Gc / _Ge as a main management parameter|index for cultivating a defect-free crystal|crystallization. From the calculation result by the formula (13) above, if the optimum temperature gradient ratio G _c /G _e is calculated according to the stress σ _mean (0) (=σ _{mean _c} ) at the center of the single crystal, the temperature gradient ratio G _c /G The distribution state of _e is as shown in FIG. 7, for example.

7 is a diagram illustrating a distribution situation of the optimum temperature gradient ratio G _c /G _e depending on the stress σ _{mean_c} at the center of the single crystal. The figure shows the case where a single crystal with a diameter of 310 mm is used as a growth object, ie, the case where r=e=155 mm. From the same figure, there is a correlation between the stress σ _{mean_c} at the center of the single crystal and the optimum temperature gradient ratio G _c /G _e (= G(0)/G(150)), It became clear that a relationship was established.

G _c /G _e = -0.0111 × σ _{mean_c} + 0.976 … (15)

For this reason, by determining the stress σ _mean (0) (= σ _{mean _c} ) of the central portion of the single crystal, the optimum temperature gradient ratio G _c /G _e can be grasped using the above equation (15). And since the relationship of the same (15) formula is established, if the single crystal is pulled under the condition of G _c /G _e that satisfies the following formula (b), it becomes possible to grow a defect-free crystal with high accuracy.

0.9 × B ≤ G _c /G _e ≤ 1.1 × B … (b)

In the above formula (b), B is -0.0111 × σ _{mean_c} + 0.976.

When the temperature gradient ratio G _c /G _e is less than “0.9×B” or exceeds “1.1×B”, the growth of the defect-free crystal becomes unstable. More preferably, the temperature gradient ratio G _c /G _e is "0.95 x B" or more and "1.05 x B" or less.

However, in the above formulas (a) and (b), the temperature gradient G _c at the center of the single crystal is within the range of 2.0 to 4.0° C./mm when a single crystal having a diameter of 310 mm is used as a growth target. It is because various point defects, such as OSF, COP, and LD, generate|occur|produce when it deviates from this range. A more preferable range of the temperature gradient G _c at the central portion of the single crystal is 2.5 to 3.5°C/mm.

As described above, the distribution of the stress σ _mean (r) in the vicinity of the solid-liquid interface of a single crystal has regularity, and the distribution of the in-plane stress σ _mean (r) is the stress σ _{mean_c} or temperature gradient G limited to the center of the single crystal. _c can be identified. As a result, taking into account the effect of stress affecting the occurrence of point defects, the temperature gradient G _c at the center of the single crystal or the stress σ _{mean_c} at the center of the single crystal is determined, so that the in-plane temperature gradient G is optimal for growing defect-free crystals. It becomes possible to grasp|ascertain the distribution of (r), and furthermore, the optimal temperature gradient ratio _Gc / _Ge . And, by using the optimal temperature gradient ratio G _c /G _e as a management index, it is possible to design the appropriate dimensions of the hot zone, and furthermore, based on the optimal temperature gradient ratio G _c /G _e , By setting the management range, it becomes possible to grow defect-free crystals with high precision.

5. Growth of silicon single crystal

Fig. 8 is a diagram schematically showing the configuration of a single crystal growing apparatus to which the method for growing a silicon single crystal of the present invention can be applied. As shown in the figure, the outer periphery of the single crystal growing apparatus is comprised by the chamber 1, and the crucible 2 is arrange|positioned in the center part. The crucible 2 has a dual structure composed of an inner quartz crucible 2a and an outer graphite crucible 2b, and is fixed to the upper end of a support shaft 3 that can be rotated and moved up and down. The rotation and raising/lowering operation of the support shaft 3 are controlled by the crucible drive mechanism 14 .

The heater 4 of the resistance heating type which surrounds the crucible 2 is arrange|positioned on the outer side of the crucible 2, and the heat insulating material 5 is arrange|positioned along the inner surface of the chamber 1 on the outer side. Above the crucible 2, a pulling shaft 6, such as a wire, which rotates at a predetermined speed in the opposite direction or the same direction on the same axis as the supporting shaft 3, is disposed. A seed crystal 7 is attached to the lower end of the pulling shaft 6 . The operation of the pulling shaft 6 is controlled by the crystal pulling mechanism 15 .

In the chamber 1 , a cylindrical water cooling body 11 is disposed above the raw material melt 9 in the crucible 2 to surround the silicon single crystal 8 being grown. The water cooling body 11 is made of, for example, a metal having good thermal conductivity such as copper, and is forcibly cooled by cooling water flowing therein. This water cooling body 11 promotes cooling of the single crystal 8 during growth, and plays a role of controlling the temperature gradient in the pulling axis direction of the single crystal central portion and the single crystal outer peripheral portion.

Moreover, the normal heat shield 10 is arrange|positioned so that the outer peripheral surface and the lower end surface of the water cooling body 11 may be surrounded. The heat shield 10 blocks the high-temperature radiant heat from the raw material melt 9 in the crucible 2, the heater 4, and the side wall of the crucible 2 with respect to the single crystal 8 during growth, and the crystal About the vicinity of the solid-liquid interface which is a growth interface, the diffusion of heat to the low-temperature water-cooling body 11 is suppressed, and it plays a role of controlling the temperature gradient of a single-crystal center part and a single-crystal outer peripheral part together with the water cooling body 11.

A gas introduction port 12 for introducing an inert gas such as Ar gas into the chamber 1 is formed in the upper portion of the chamber 1 . An exhaust port 13 for sucking and discharging gas in the chamber 1 by driving a vacuum pump (not shown) is formed in the lower portion of the chamber 1 . The inert gas introduced into the chamber 1 from the gas inlet 12 descends between the single crystal 8 and the water cooling body 11 during growth, and the lower end of the heat shield 10 and the liquid level of the raw material melt 9 . After passing through the gap (liquid level gap) of

A camera 16 is provided outside the chamber 1 , and the camera 16 images the vicinity of the solid-liquid interface through an observation window formed in the chamber 1 . The captured image of the camera 16 is processed by the image processing unit 17, and the crystal diameter, the liquid level position, and the like are obtained. The control unit 18 controls the heater 4, the crucible driving mechanism 14, and the crystal pulling mechanism 15 based on the image processing result.

When the silicon single crystal 8 is grown using such a growing device, a solid raw material such as polycrystalline silicon filled in the crucible 2 is filled in the crucible 2 while the inside of the chamber 1 is maintained in an inert gas atmosphere under reduced pressure into the heater 4 is melted by heating to form a raw material melt 9 . When the raw material melt 9 is formed in the crucible 2, the pulling shaft 6 is lowered to immerse the seed crystal 7 in the raw material melt 9, and the crucible 2 and the pulling shaft 6 are set in a predetermined position. While rotating in the direction, the pulling shaft 6 is gradually pulled up, thereby growing a single crystal 8 continuous to the seed crystal 7 .

When growing a single crystal having a diameter of 310 mm, in order to grow a defect-free crystal, in the vicinity of the solid-liquid interface of the single crystal, the temperature gradient ratio G _c /G _e satisfies the conditions of the above formula (a) or (b). , the pulling speed of the single crystal and the gap (the height of the crucible 2 ) are adjusted to pull up the single crystal. In addition, prior to growth of the single crystal, the dimensional shape of the hot zone (heat shield and water cooling body) is designed so that it is suitable for the optimum temperature gradient ratio G _c /G _e obtained by the above formula (14) or (15), , use this hot zone. Thereby, a defect-free crystal|crystallization can be grown with high precision.

9 is a graph showing the relationship between the gap H and the temperature gradient ratio G _c /G _e between the heat shield 10 and the liquid level of the raw material melt 9 , the horizontal axis is the gap H, and the vertical axis is G _c /G _e is indicating In the same figure, the triangle plot points are the values of the gap H and the temperature gradient ratio G _c /G _e obtained by comprehensive thermal simulation for growing a silicon single crystal having a diameter of 310 mm using a hot zone having a specific structure. The relationship is shown, and the lower limit of 0.9A and the upper limit of _1.1A of _Gc /Ge in the formula (a) are shown by two straight lines. The region placed between these two straight lines is a range defined by the formula (a), ie, a range in which a defect-free crystal is obtained.

As shown in FIG. 9, in the range where the gap _H is about _58-70 mm, it turns out that Gc/Ge satisfy|fills Formula (a). Thus, by adjusting the gap _H , the temperature gradient ratio _Gc /Ge can be set within the range of 0.9A-1.1A.

10 is a flowchart showing the manufacturing process of the silicon single crystal 8. As shown in FIG. 11 is a schematic cross-sectional view showing the shape of a silicon single crystal ingot.

As shown in FIG. 10 , in the manufacturing process of the silicon single crystal 8 according to the present embodiment, the raw material melt 9 is produced by heating and melting the silicon raw material in the crucible 2 with a heater 4 . S11, a liquid landing step S12 in which the seed crystal mounted on the tip of the pulling shaft 6 is lowered to land on the raw melt 9, and a single crystal by gradually pulling up the seed crystal while maintaining a state of contact with the raw melt 9 It has a crystal pulling process (S13-S16) which grows up.

In the crystal pulling step, a necking step S13 of forming a neck portion 8a with a narrow crystal diameter for dislocation-free, a shoulder portion growing step S14 of forming a shoulder portion 8b with a gradually increasing crystal diameter along with crystal growth; A body portion growing step S15 of forming the body portion 8c in which the crystal diameter is kept constant, and a tail portion growing step S16 of forming a tail portion 8d having a gradually reduced crystal diameter along with crystal growth are performed in this order.

Thereafter, a cooling step S17 of separating the silicon single crystal 8 from the melt surface to promote cooling is performed. As a result, the silicon single crystal ingot 8I having the neck portion 8a, the shoulder portion 8b, the body portion 8c, and the tail portion 8d as shown in FIG. 11 is completed.

As described above, the type and distribution of crystal defects contained in the silicon single crystal 8 depend on the ratio V/G of the crystal pulling rate V and the temperature gradient G, and the in-furnace thermal environment surrounding the crystal, that is, the hot zone. are strongly influenced by Therefore, when the hot zone changes with the progress of the crystal pulling process, even if the gap is maintained at a constant distance, G _c /G _e cannot be made to fall within the range of 0.9A to 1.1A, and the desired pulling speed In some cases, margins cannot be secured.

For example, in the middle of the body part growing step S15 shown in Fig. 8, a single crystal ingot of sufficient length exists in the space above the silicon melt, whereas at the start of the body part growing step S15, such a single crystal ingot is formed. Since it does not exist, even if the heat shield 10 was formed, the heat distribution in space will be somewhat different. In addition, at the end of the body portion growing step S15, the output of the heater 4 is increased to prevent solidification of the silicon melt accompanying the decrease of the raw material melt 9 in the crucible. do. When the hot zone is changing in this way, even if the gap is maintained at a constant distance, since the thermal history in the crystal changes, the in-plane distribution of crystal defects cannot be kept constant.

Therefore, in the present embodiment, the gap is not always maintained at a constant distance from the top to the bottom of the ingot, but the gap is changed according to the crystal growth stage. That is, the gap is changed so that the temperature gradient ratio G _c /G _e satisfies the above expression (a) or (b). By changing the gap in this way, the in-plane distribution of crystal defects from the top to the bottom of the ingot can be controlled as desired, and the reduction in the pulling rate margin can be suppressed to improve the manufacturing yield of defect-free crystals. How the gap can be changed to suppress a decrease in the pulling rate margin differs depending on the hot zone. Therefore, in order to keep the temperature gradient ratio G _c /G _e from the top to the bottom of the crystal within the range of 0.9A to 1.1A to make the in-plane distribution of crystal defects constant, how does the hot zone change with the progress of the crystal pulling process? It is necessary to appropriately set the gap profile according to the crystal growth stage while taking into account whether it changes.

12 and 13 are schematic diagrams for explaining the relationship between the gap profile and the crystal defect distribution during the crystal pulling process. FIG. 12 is a case of a conventional constant gap control, and FIG. 13 is a case of a variable gap control of the present invention, respectively. is indicating

As shown in Fig. 12, in the constant gap control for always maintaining the gap at a constant distance during the crystal pulling process, since the temperature gradient ratio G _c /G _e changes as the hot zone changes, the in-plane distribution of crystal defects is kept constant. can't keep That is, in the top, the center, and the bottom of the silicon single crystal ingot 8I, the in-plane distribution of crystal defects is different, so that G _c /G _e is optimized at the center of the ingot 8I. Thus, a desired pulling-up speed margin can be secured, but the desired pulling-up speed margin cannot be secured at the top and bottom of the ingot 8I.

On the other hand, in the present invention, as shown in Fig. 13 , the gap profile is set so that the gap is gradually narrowed in accordance with the progress of the crystal pulling process. In particular, the gap profile according to the present embodiment is a first gap constant control section (S1) in which the gap is kept constant from the start of the crystal pulling process, and a first gap formed in the first half of the body part growing process and gradually lowering the gap. Variable control section (S2), second gap constant control section (S3) for maintaining the gap constant, second gap variable control section (S4) formed at the end of the body part growing process and gradually lowering the gap (S4), crystal pulling process A third constant gap control section S5 for maintaining the gap constant until the end of , is formed in this order. Such a gap profile is set according to the change of the hot zone, and thereby, as shown, it becomes possible to maintain a constant in-plane distribution of crystal defects from the top to the bottom of the ingot 8I, thereby increasing the manufacturing yield of defect-free crystals.

In addition, the above gap profile is an example, and is not limited to a profile in which the gap is gradually narrowed according to the progress of the crystal pulling process. Therefore, for example, it is also possible to gradually lower the gap in the first variable gap control period S2 and gradually increase the gap in the second variable gap control period S4 .

The temperature gradient of the outer peripheral portion of the single crystal 8 is more susceptible to the influence of the change of the gap than the temperature gradient of the central portion. When the gap is wide, the radiant heat from the heater 4 passes through the gap and is easily transmitted to the single crystal 8, so the temperature gradient _{Ge of the outer periphery of the single crystal 8 becomes relatively small, and the temperature gradient ratio G c /} G _e increases. Conversely, when the gap is narrow, the radiant heat from the heater 4 is blocked by the heat shield 10, making it difficult to transmit to the single crystal 8, so that the temperature gradient _Ge of the outer periphery of the single crystal 8 becomes relatively large, The temperature gradient ratio G _c /G _e becomes small. Therefore, by adjusting the gap, the temperature gradient ratio G _c /G _e can be easily adjusted.

In the case of performing the gap variable control, a phenomenon in which the crucible rising speed is greatly oscillated may occur by simply correcting the crucible rising speed and changing the gap. Such a oscillation phenomenon may become an obstacle for the purpose of maintaining a constant in-plane distribution of crystal defects from the top to the bottom of the ingot 8I by the gap variable control and increasing the manufacturing yield of defect-free crystals. Therefore, in the present invention, such a vibration phenomenon is prevented and a high-quality crystal can be manufactured.

Next, the calculation method of the crucible rising speed in the gap variable control of this invention is demonstrated, referring a functional block diagram of FIG.

As shown in FIG. 14 , the gap variable control function has a crucible rising speed calculation unit 30 . The crucible rising rate calculating unit 30 is a quantitative value calculating unit 31 that calculates a quantitative value V _f of the crucible rising rate necessary for constant control of the liquid level position and the gap that change with the pulling of the silicon single crystal 8 . ), a variation value calculating unit 32 that calculates a variation value Va of the crucible rising speed from the change in the target value of the gap, and _a correction value V of the crucible rising speed from the difference between the target value of the gap and the measured value of the gap It has the correction value calculation part 33 which calculates _adj , while the crucible drive mechanism 14 outputs liquid level rising speed V _M , and the sum value of quantitative value V _f , fluctuation value _Va and correction value V _adj to control the position of the crucible. Further, the crystal pulling mechanism 15 outputs the crystal length _{ΔLS (crystal pulling speed V S )} . The image processing unit 17 measures the gap and the crystal diameter between the liquid level of the raw material melt 9 and the heat shield 10 from the captured image of the camera 16 .

In the gap variable control, the crucible rising speed is controlled for every control cycle based on the crucible rising speed V _C calculated using the formula (16) shown below.

V _C = V _f + V _a + V _adj … (16)

Here, V _f is a quantitative value of the crucible rising speed required to keep the gap constant, and is the crucible rising speed used for controlling the gap constant. In addition, Va is a change value of the crucible rising speed obtained from the change in the gap target value, and V _adj is _a correction value of the crucible rising speed obtained from the difference between the current target value of the gap and the actual measured value.

Quantitative value V _f of a crucible raising rate is calculated|required from following (17) Formula.

V _f = ((P _S × D _S ² ) ÷ ( _PL × D _C ² )) × (V _S - V _M ) + V _M … (17)

P _S : Silicon solid specific gravity (=2.33 × 10 ^-3 )

P _L : Specific gravity of silicon melt (=2.53 × 10 ^-3 )

D _S : current crystal diameter

D _C : inner diameter of the current quartz crucible

V _S : current crystal raise rate

V _M : Crucible ascent rate (level rise rate) of the previous time

In addition, the liquid level rise rate V _M becomes the following expression (18).

V _M = -((P _S × D _S ² × ΔL _S ) ÷ (P _L × D _C ² - P _S × D _S ² )) + ((P _L × D _C ² × ΔL _C ) ÷ (P _L × D _C ² - P _S × D _S ² )) … (18)

ΔL _S : Amount of crystal movement per 1 control cycle

ΔL _C : Crucible movement per 1 control cycle

In this way, in the calculation of the quantitative value V _f of the crucible rising speed, the amount of crystal movement (crystal length) _ΔLS per one control cycle from the crystal pulling mechanism 15 is obtained, and determined from the crystal diameter _DS and the amount of crystal movement _ΔLS An increase in the volume is obtained, an increase in the crystal volume and a decrease in the melt volume are calculated from the inner diameter of the crucible DC, and a quantitative value _{V f} of the crucible rising rate is calculated from the decrease in the melt volume and the inner diameter of the crucible _DC . The crystal diameter _DS is calculated|required by the image processing part 17 processing the single crystal|crystallization taken in the picked-up image of the camera 16. _The crucible inner diameter DC is a fixed value obtained from the design dimensions of the quartz crucible 2a.

When the liquid level rising rate V _M is in balance with the current crystal pulling rate V _S , the quantitative value V _f of the crucible rising rate becomes equal to the liquid level rising rate V _M , so that the gap is maintained at a constant distance. Also, if the level rise rate _{V M} is larger than the current crystal pulling rate _{V S} , the quantitative value V _f of the crucible rising rate becomes smaller than the level rise rate V _M. Since the quantitative value V _f of the crucible rising speed is larger than the liquid level rising speed V _M , the gap can be kept constant.

The variation value _Va of the crucible rising speed becomes as follows (19) Formula.

V _a = (H _{pf_i} - H _{pf_i+1} ) ÷ T ... (19)

Here, H _{pf_i} is the current (i-th) gap target value (mm), and H _{pf_i+1} is the gap target value (mm) after one control cycle (i+1 time). This gap target value is set according to the crystal length, for example, and the crystal length after one control period can be obtained from the increment of the crystal length obtained by multiplying the current crystal pulling rate V _S by the control period T (min). Although the control period T is not specifically limited, For example, it can set to 2 minutes. In this way, the variation value _{Va of the crucible rising speed is obtained from the difference between the current gap target value H pf_i and} the gap target value H _{pf_i+1} after one control period. When the target value of the gap is constant (H _{pf_i+1} = H _{pf_i} ) without changing, V _a = 0 . For example, when the gap is changed from 50 mm to 51 mm, it is necessary to increase the gap by 1 mm. Since such a change in the target value of the gap can be known from the gap profile, it is necessary to increase the gap by 1 mm. The fluctuation value Va of the crucible rising speed _is added to the quantitative value _Vf .

Correction value V _adj of crucible raising speed becomes as following (20) Formula.

V _adj = (H _{pf_i} - H _i ) ÷ T × k . (20)

Here, H _i is the current gap measurement value (mm), preferably a moving average value rather than the latest single value. Moreover, k is a gain, and it is preferable that it is 0.001 or more and 0.1 or less. When k is set to, for example, 0.05, the influence of the deviation of the measured gap value on the crucible rising speed is suppressed to 1/20. When the gap measurement value is equal to the gap target value, the crucible raising correction rate V _adj = 0.

As described above, the accurate value of the inner diameter _DC of the quartz crucible 2a is required for calculation of the quantitative value V _f of the crucible rising rate. However, since the quartz crucible 2a softens near the melting point of silicon and may deform during pulling, the value of the gap deviate from the target value. In addition, the gap value deviates from the target value due to various factors. Therefore, in this embodiment, the gap is actually measured from the position of the mirror image of the heat shield 10 reflected by the melt surface, and the control error of the gap is calculated from the crucible rising speed calculated from the decrease amount of the raw melt 9, , by adding the correction value V _adj of the rising speed of the quartz crucible 2a which eliminates this control error to the quantitative value V _f , the gap is controlled with high precision.

As described above, the crucible rising speed V _C is the quantitative value V _f of the crucible rising speed required to keep the gap constant, the variation value V _a of the crucible rising speed obtained from the change in the gap target value, and the gap It consists of the sum of the correction value V _adj of the crucible rising speed obtained from the difference between the target value and the actual measured value. For the change in the gap target value obtained from the gap profile, the measured gap value is a value based on the quantitative value. By including in advance in the crucible rising speed irrespective of this, the fluctuation of the correction value V _adj of the crucible rising speed can be made as small as possible. That is, since the role played by the correction value V _adj of the crucible rising speed is specialized only by correction for eliminating the gap between the target value and the measured value, it is possible to prevent the crucible rising speed amplitude from increasing, and the crucible rising speed is stable control of

As described above, the method for growing a silicon single crystal according to the present embodiment includes gap variable control for pulling up the single crystal while changing the gap between the liquid level of the raw material melt and the heat shield, and in the vicinity of the solid-liquid interface at the center of the single crystal. Let the temperature gradient of G _c and the temperature gradient Ge in the vicinity of the solid-liquid interface of the outer periphery of the single crystal, and A = 0.1769 × G _c + _0.5462 , the temperature gradient ratio G _c /G _e is 0.9 × A ≤ G Since the single crystal is pulled up while changing the gap under the condition that _c /G _e ≤ 1.1 × A , a defect-free crystal can be grown with high precision while taking the stress acting in the single crystal into consideration when growing the single crystal.

Further, in the method of growing a silicon single crystal according to the present embodiment, a gap profile in which a target gap value changes according to a crystal length is prepared, and a crucible rising rate V _C is controlled so that a measured gap value conforms to the gap profile during crystal growth. Therefore, it is possible to prevent an increase in the amplitude of the crucible rising speed, and as a result, a high-quality silicon single crystal with little change in the in-plane distribution of crystal defects from the top to the bottom of the silicon single crystal can be manufactured with good yield.

Further, in the present embodiment, a quantitative value V _f of the crucible rising rate required to keep the gap constant, and a variation value V _a of the crucible rising rate required to change the gap from a change in the target value of the gap, Since the sum of the correction value V _adj of the crucible rising speed necessary to correct the difference between the target value of the gap and the measured value is used as the crucible rising speed V _C , the control of the crucible rising speed caused by the gap variable control is unstable. can be improved, thereby improving the crystal acquisition rate.

As mentioned above, although preferred embodiment of this invention was described, this invention is not limited to said embodiment, Various changes are possible in the range which does not deviate from the main point of this invention, and they are also within the scope of the present invention. Not to mention what is included.

For example, in the said embodiment, as a correction value of a crucible rising speed, the reciprocal 1/T of a control period and gain k to the difference (H _{pf_i} - H _i ) between the gap target value H _{pf_i} and the gap measurement value H _i Although multiplication values are used, the present invention is not limited to such values, and correction values calculated by various calculation methods can be used.

Moreover, although the method of growing a silicon single crystal was mentioned as an example in the said embodiment, this invention is not limited to this, Various single crystal pulled up by the CZ method can be made into object.

The method for growing a silicon single crystal of the present invention is very useful for growing a defect-free crystal in which various point defects such as OSF, COP, and LD do not occur.

1: chamber
2: Crucible
2a: quartz crucible
2b: graphite crucible
3: support shaft
4: Heater
5: Insulation
6: impression shaft
7: seed crystal
8: silicon single crystal
8I: Silicon single crystal ingot
8a: neck
8b: shoulder
8c: body part
8d: tail
9: Raw material melt
10: heat shield
11: water cooling body
12: gas inlet
13: exhaust port
14: crucible driving mechanism
15: crystal lifting mechanism
16 : camera
17: image processing unit
18: control unit
30: crucible rising speed calculation unit
31: quantitative value calculation unit
32: variable value calculation unit
33: correction value calculation unit

Claims (10)

A method for growing a silicon single crystal by the Czochralski method in which a single crystal having a diameter of 300 mm or more is pulled from a melt of a raw material in a crucible disposed in a chamber, the method comprising:
A single crystal growing device in which a water cooling body surrounding the single crystal during growth is disposed and a heat shield surrounding the outer peripheral surface and the lower end surface of the water cooling body is disposed;
and a gap variable control for pulling up the single crystal while changing a gap between the liquid level of the raw material melt and the heat shield disposed above the raw material melt,
The temperature gradient in the pulling axis direction in the vicinity of the solid-liquid interface at the center of the single crystal is G _c , and the temperature gradient in the pulling axis direction in the vicinity of the solid-liquid interface in the outer periphery of the single crystal is G _e , A = 0.1769 × G _c + 0.5462 When the single crystal is pulled under the conditions satisfying 0.9 × A ≤ G _c /G _e ≤ 1.1 × A,
The gap variable control is
a quantitative value of the crucible rising speed required to maintain the gap, which changes with the pulling of the single crystal, at a constant distance;
a change value of the crucible rising speed obtained from a change in the target value of the gap;
The method for growing a silicon single crystal according to claim 1, wherein the crucible rising speed is controlled by using the sum of the correction values of the crucible rising speed obtained from the difference between the target value of the gap and the actual measured value. The method of claim 1,
A method for growing a silicon single crystal, wherein a decrease in the volume of the raw material melt is obtained from an increase in the volume of the single crystal accompanying pulling up the single crystal, and the quantitative value is obtained from a decrease in the volume of the raw material melt and the inner diameter of the crucible. The method of claim 1,
A method for growing a silicon single crystal, wherein the change in the target value of the gap is obtained from a gap profile that defines a relationship between a crystal length that changes with pulling of the single crystal and a target value of the gap. 4. The method of claim 3,
The said correction value is calculated|required from the difference between the target value of the said gap calculated|required from the said gap profile, and the measured value of the said gap. 5. The method according to any one of claims 1 to 4,
The gap profile includes at least one gap constant control section for maintaining the gap at a constant distance, and at least one gap variable control section for gradually changing the gap, the silicon single crystal growing method. 6. The method of claim 5,
The method for growing a silicon single crystal, wherein the gap variable control section is formed after the constant gap control section as a second half of the step of growing the body portion of the single crystal. 6. The method of claim 5,
The method for growing a silicon single crystal, wherein the gap variable control section is formed before the constant gap control section as a first half of the single crystal body portion growing process. 6. The method of claim 5,
The gap profile includes first and second gap variable control sections for gradually changing the gap,
The first variable-gap control section is formed before the constant-gap control section as the first half of the single-crystal body part growing process,
and the second variable-gap control section is formed after the constant-gap control section as a second half of the single-crystal body portion growing process. 5. The method according to any one of claims 1 to 4,
A method for growing a silicon single crystal, wherein the measured value of the gap is calculated from the position of the mirror image of the heat shield reflected on the liquid level of the raw material melt photographed with a camera. delete

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