JP2000119089A - Single crystal pulling apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To speed up the growth of a single crystal and also to lengthen the lifetime of a radiation shield by forming beveled part so as to reduce the diameter of cylindrical part of the radiation shield having the shape of a frustum of a cone and having an opening for a single crystal to pass through. SOLUTION: When a single crystal pulling apparatus has a three-layered radiation shield 10 including a heat-insulating material installed above a silicon melt surface 13 for the purpose of effectively shutting out primary radiant heat from the melt 3 to a single crystal 20, of retaining the temperature of the conical part of the shield 10 so as to be low and of effectively shutting out secondary radiant heat from the conical part to the single crystal 20, the temperature gradient of the single crystal 20 in its axial direction increases and high-speed crystal pulling is made to become possible at high rate of single crystal. Effective exhaust is carried out by beveling or rounding the outskirts of the bottom of the shield 10 (e.g. by forming a cylindrical arc) so as to enlarge the breather path, and therefore it is possible to prevent SiO2 from sticking to the shield 10 and also to prevent the SiO2 from dropping from the shield 10 to the melt surface 13 thus inducing the dislocation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a single crystal pulling apparatus, and more particularly to a single crystal pulling apparatus having an improved radiation shield.

[0002]

2. Description of the Related Art In general, a single crystal for a silicon wafer is pulled by a Czochralski method (CZ method).

In a conventional single crystal pulling apparatus, a quartz glass crucible 61 is placed above a quartz glass crucible 61 of a single crystal pulling apparatus 60, as shown in FIG. In order to shield the radiant heat from the melt surface 63 of the silicon melt 61 or the silicon melt 62 to the single crystal 64 and prevent the single crystal pulling speed from decreasing, an inverse formed by a single-layer metal plate so as to surround the single crystal 64 A radiation shield 65 having a truncated cone shape is provided.

[0004] Such a conventional single crystal pulling apparatus 60 has the effect of preventing the single crystal pulling speed from being lowered, but the heat generated by the reflection from the surface 63 of the melt toward the single crystal 64. Alternatively, as a result of the radiation shield 65 itself being heated to a high temperature, the secondary radiation heat is radiated toward the single crystal 64, and the cooling effect on the single crystal 64 is insufficient, so that the deterioration of the crystal quality is unavoidable. I cannot get a lift.

As an improvement of the single crystal pulling apparatus 60 having the radiation shield 65 of the conventional shape described above, Japanese Patent Publication No.
No. 35715 discloses a single crystal pulling apparatus 71 having a radiation shield 70 having a shape as shown in FIG. Conventional single crystal pulling apparatus 71 as shown in FIG.
The radiation shield 70 has a thickness between the inner surface 72 and the outer surface 73 of the radiation shield 70, the thickness of the heat insulating material 7 partially or entirely increased as approaching the melt surface 74.
5 is provided. The single crystal pulling apparatus 71 having such a radiation shield 70 improves the heat insulation performance of radiant heat and can easily increase the crystal growth rate. However, the inert gas filling the single crystal pulling apparatus 71 uses the radiation shield 70. Distance d2 formed between the lower end 76 of the glass and the melt surface 74, the outer surface 73 of the radiation shield 70 and the quartz glass crucible 7
7 passes through a space distance d3 formed between the inner wall surfaces 78, and at this time, in the lower L-shaped portion 79 in which the flow direction changes from the horizontal direction to the vertical ascending direction, the gas flow is disturbed, and the gas flow is further reduced. Since the cross-sectional area is small, turbulence of the gas flow is amplified, and effective exhaust is not performed. Results exhaust gas becomes insufficient, generated from a quartz glass crucible 77, SiO ₂ is radiation shield 70 contained in an inert gas, in particular adhered to the L-shaped portion 79, the short life and SiO ₂ of the radiation shield 70 This causes the dislocation to be induced by dropping on the melt surface 74, which lowers the productivity of pulling a single crystal.

[0006]

Therefore, it is possible to easily increase the crystal growth rate, effectively exhaust the inert gas, and shorten the radiation shield by SiO ₂ contained in the inert gas. There has been a demand for a single crystal pulling apparatus which prevents the life of the single crystal and further prevents the SiO _{2 from} dropping onto the surface of the melt to increase the productivity of pulling the single crystal.

The present invention has been made in consideration of the above circumstances, and enables a single crystal to be pulled at a high speed, prevents the occurrence of dislocations, increases the productivity of the pulling of a single crystal, and has a long service life of a radiation shield. It is an object of the present invention to provide a single crystal pulling apparatus which has been developed.

[0008]

Means for Solving the Problems According to the first aspect of the present invention, which has been made to attain the above object, a quartz glass crucible provided in a furnace is heated to remove polysilicon loaded in the quartz glass crucible. In a single crystal pulling apparatus for melting and pulling a semiconductor single crystal, a radiation shield is provided above the quartz glass crucible, and the radiation shield has an inverted frustoconical cone having an opening through which the single crystal penetrates. Portion, and communicates with the lower end of the conical portion, extends radially outward from the lower end of the conical portion, and faces the polysilicon melt surface so as to form an air passage between the polysilicon melt surface. And a cylindrical straight body facing the inner surface of the quartz glass crucible so as to form a ventilation path between the horizontal portion and the inner surface of the quartz glass crucible; Section and horizontal section A chamfered portion made of a heat insulating material filled in a hollow portion formed and provided at a communicating portion between the horizontal portion and the straight body portion such that the straight body portion is reduced in diameter toward the center line direction of the single crystal. The present invention is characterized in that the apparatus is a single crystal pulling apparatus characterized by forming.

The gist of the invention of claim 2 of the present application is the single crystal pulling apparatus according to claim 1, wherein the chamfered portion is formed by an arc portion.

According to a third aspect of the present invention, the chamfered portion is formed by a circular arc portion, and the radius of curvature of the circular arc portion is defined by a ventilation path formed between the surface of the polysilicon melt and the horizontal portion and a quartz glass crucible. The gist of the invention is a single crystal pulling apparatus according to claim 1, wherein the distance is larger than a space distance of an air passage formed between the inner surface and the straight body portion.

According to a fourth aspect of the present invention, there is provided a single crystal pulling apparatus according to the first aspect, wherein the chamfered portion is formed by an inclined portion.

According to a fifth aspect of the present invention, the chamfered portion is formed by an inclined portion, and the horizontal projection length and the vertical projection length of the inclined portion are adjusted by the ventilation formed between the surface of the polysilicon melt and the horizontal portion. The gist of the invention is a single crystal pulling apparatus according to claim 4, wherein the clearance is larger than a space distance of a passage and an air passage formed between the inner surface of the quartz glass crucible and the straight body.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a single crystal pulling apparatus according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a single crystal pulling apparatus 1 according to the present invention.
The lifting apparatus 1 comprises a water-cooled furnace 2 and a furnace 2
It has a quartz glass crucible 4 which melts polysilicon as a raw material and is made into molten silicon 3, a graphite crucible 5 holding the quartz glass crucible 4, and a heater 6 surrounding the graphite crucible 5. . The pulling apparatus 1 has a double-layer structure in which a quartz glass crucible 4 is disposed inside and a graphite crucible 5 is disposed outside. This graphite crucible 5 is
And is coupled to a motor (not shown) and rotated,
And it is attached to a crucible rotating shaft 8 which is raised and lowered by a lifting device (not shown).

Above the quartz glass crucible 4 rotated by the crucible rotating shaft 7, a pulling wire 9 to which a seed 8 for pulling a single crystal is attached is provided. The wire 9 is provided outside the furnace body 2 and is equipped with a wire rotating device (not shown) that is urged by a motor (not shown) to wind up and rotate the wire 9.

Above the quartz glass crucible 4 and the silicon melt 3, heat radiation from the silicon melt 3 is prevented, and an inert gas such as argon gas (hereinafter referred to as Ar) flowing in the furnace body 2. .) Is provided.

As shown in FIG. 2 in an enlarged manner, the radiation shield 10 forms an inner surface portion 11 of the radiation shield 10 and has an inverted truncated cone-shaped conical portion 11 having an opening 12 through which a single crystal 20 penetrates. A horizontal portion 14 communicating with a lower end of the conical portion 11 and extending radially outward from the lower end of the conical portion 11 and facing the melt surface 13 and facing an inner surface 15 of the quartz glass crucible 4. A vertically extending cylindrical body 16, and a heat insulating material 18 filled in a hollow part 17 formed by the body 16, the conical part 11 and the horizontal part 14.
And more. Therefore, the radiation shield 10 is formed in a three-layer structure with the conical portion 11, the straight body portion 16, and the heat insulating material 18, and the heat insulating property is enhanced.

Further, in a communicating portion 19 in which the horizontal portion 14 communicates with the straight body portion 16, a chamfered portion provided with the straight body portion 16 to decrease in diameter toward the center line of the single crystal 20, for example, a cylindrical portion A circular arc portion 19 is formed.

The upper end 2 of the conical portion 11 and the straight body 16
From 2, 23, an annular ring extending radially and horizontally outwardly,
A flange-shaped or flange-shaped rim portion 24, 25 is provided, and a hollow portion 28 for filling a heat insulating material 27 is formed by a cylindrical support portion 26 extending downward from the annular rim portion 24, 25. Is provided.

As described above, the cylindrical arc portion 19 provided so as to reduce the diameter in the direction of the center line of the single crystal 20.
Is designed so that the horizontal projection length of the outer surface of the arc portion 19 is A and the vertical projection length is B, that is, A = B, so that the radius of curvature of the arc portion 19 is obtained.

On the other hand, the radiation shield 10 is always mounted at a substantially constant height by raising the air passage 32 and the rotating shaft 7 having a space distance D1 between the inner wall surface 30 of the opening 12 and the outer wall side wall 31 of the single crystal 20. The air passage 33 having a space distance D2 between the melt surface 13 and the horizontal portion 14 maintained at this time, and the space distance D between the straight body portion 16 and the inner wall surface 15 of the quartz glass crucible 4.
It is attached to the attachment part 35 of the furnace body 2 via the support part 26 so that three ventilation paths 34 are formed.

Here, A = B> D2, D during each spatial distance.
The radiation shield 10 is attached so that the relationship of 3 is satisfied.

Reference numeral 36 denotes an exhaust port provided in the furnace bottom 37 of the furnace body 2.

Since the single crystal pulling apparatus 1 according to the present invention has the above-described structure, in order to pull up the silicon single crystal 20, nugget-like polysilicon is put into a quartz glass crucible 4, and Ar is placed in a furnace. The quartz glass crucible 4 is heated by energizing the heater 6 and flowing into the furnace body 2 from above the body 2,
The motor is energized to rotate the rotating shaft 7 connected to the motor, thereby rotating the quartz glass crucible 4.

After a certain period of time, the seed shaft 9 is lowered, and the seed crystal is brought into contact with the melt surface 13 to grow the single crystal 20 and pull up the single crystal 20.

In the single crystal pulling step, since the radiation shield 10 is provided above the melt surface 13,
Primary radiant heat of the single crystal 20 from the silicon melt 3 is effectively blocked. Further, since the radiation shield 10 is formed of a triple layer including the heat insulating material 18, the temperature of the conical portion 11 of the radiation shield 10 is kept low, and the secondary radiation heat from the conical portion 11 to the single crystal 20 is also effectively reduced. Cut off, single crystal 2
The temperature gradient in the direction of the vertical axis of 0 becomes large, and a crystal with a high single crystallization ratio can be pulled at a high speed.

On the other hand, an inert gas, eg, Ar, introduced from the upper part of the furnace body 2 descends along the seed shaft 10 and the silicon single crystal 20, and the opening 1 provided in the radiation shield 10
The exhaust port 1 provided in the bottom portion 38 of the furnace body 2 through the ventilation path 32 formed in the furnace body 2 and the ventilation path 33 and the ventilation path 34
2 is discharged out of the furnace body 2.

In the process of flowing the Ar furnace body 2 as described above, a corner portion formed between the ventilation path 33 and the ventilation path 34,
That is, the arc portion 1 is located at the position where the flow direction of Ar changes from the horizontal direction to the vertical ascending direction, and at the bottom outer periphery of the radiation shield 10.
Since the gas passages 9 and 9 are provided in the circumferential direction and the gas passages 33 and 34 are enlarged, the exhaust gas is sufficiently efficiently exhausted without disturbing the flow of Ar, and the crystal pulling with a higher single crystallization rate can be performed. .

Further, the radiation shield 10 is provided with an arc portion 19 on the outer peripheral side of the bottom portion, and the ventilation path 33 and the ventilation path 34 are enlarged so that exhaust can be performed sufficiently effectively, so that SiO ₂ adheres to the radiation shield 10. To prevent the radiation shield 10 from prolonging its life, and furthermore, a crystal having a high single crystallization rate without causing SiO ₂ attached to the radiation shield 10 to fall on the melt surface 13 to induce dislocation. Pulling is possible.

Next, another embodiment of the single crystal pulling apparatus according to the present invention will be described.

As shown in FIG. 3, a single crystal pulling apparatus 38 according to the present invention has a structure almost similar to that of the above-described embodiment, and a radiation shield is provided above a quartz glass crucible 39 and a silicon melt 40. 41 are provided. As shown in FIG. 3, the radiation shield 41 has an inner truncated cone 44 having an inverted truncated cone shape having an opening 43 through which the single crystal 42 penetrates.
And a three-layer structure of a straight body part 45 and a heat insulating material 46 interposed between the straight body part 45 and the conical part 44.

Further, a horizontal portion 47 is provided between the inner conical portion 44 and the outer straight body portion 45, and the straight body portion 45 communicates with the horizontal portion 47 so that the diameter of the straight body portion 45 decreases in the direction of the center line of the single crystal 42. A chamfer-shaped chamfered portion, for example, an inclined portion 48 is provided, and the horizontal portion 47 is chamfered by the inclined portion 48.

As described above, the inclined portion 48 provided so as to reduce the diameter toward the center line direction of the single crystal 42 has a horizontal projection length of E on the outer surface of the inclined portion 48 and a vertical projection length of Designed for F.

On the other hand, the radiation shield 41 is always mounted at a substantially constant height by raising the ventilation path 52 and the rotating shaft 53 having a space distance L1 between the wall surface 50 of the opening 43 and the side wall 51 of the single crystal 42. Between the melt surface 54 and the horizontal portion 47 maintained at a constant distance L2 and the straight body portion 45
Distance L3 between the inner wall surface 56 of the quartz glass crucible 39 and
Is attached to a support plate (not shown) via an attachment portion (not shown) so that the ventilation path 57 is formed. Here, the radiation shield 41 is attached so that the relationship of E, F> L2, L3 is satisfied between the respective spatial distances.

Since the radiation shield 41 has the above-described structure, a corner portion 59 formed between the ventilation path 55 and the ventilation path 57 during the ventilation of the inert gas, for example, Ar, through the furnace body 58, that is, An inclined portion 48 is provided at a position where the flow direction of Ar changes from the horizontal direction to the vertical ascending direction, and the ventilation path 55 and the ventilation path 57 are widened by chamfering, so that the Ar flow is not disturbed and exhaust is sufficient. Effectively performed, a crystal can be pulled with a higher single crystallization ratio.

Further, it is possible to prevent the SiO ₂ from adhering to the radiation shield 41 to prolong the life of the radiation shield 41, and the SiO ₂ adhering to the radiation shield 41 drops on the melt surface 54 to cause dislocation. A crystal having a high single crystallization ratio can be pulled without causing induction.

[0037]

EXAMPLES [Examples] (Testing method): In the single crystal pulling apparatus of the first embodiment, the horizontal projection length A and the vertical projection length B of the outer surface of the arc portion are A = B, and Spatial distance D of air passage between liquid surface and horizontal part
2 and the space distance D3 of the ventilation path between the straight body portion and the inner wall surface of the quartz glass crucible, A = B>
A radiation shield was attached and a single crystal pulling test was performed so that the relationship of D2 and D3 was satisfied.

(Test result): In the example, the single crystal pulling speed was improved by 50% as compared with the case where the single crystal was pulled using the conventional radiation shield having a single layer structure (FIG. 4). Also,
The single crystallization ratio was 100%. As described above, the pulling rate was greatly improved, and the single crystallization ratio was 100%.
% And good results. Furthermore, the radiation shield was observed immediately after pulling up.
_{No 2} was deposited, demonstrating effective exhaust.

[Comparative Example] (Test method): The test is the same as that of the embodiment, except that a radiation shield is attached and a single crystal pull-up test is performed so that the relationship of A = B <D2, D3 is established between the respective spatial distances. went.

(Test result): The single crystal pulling speed was improved by 50% as compared with the case where a single crystal was pulled from the conventional radiation shield having a single layer structure. The single crystallization ratio was 82%. Thus, although significant or improvement is observed for the pulling rate, the observed radiation shield immediately after pulling, adhesion of SiO ₂ is confirmed in the conical part the lower part of the radiation shield, that the effective exhaust has not been made confirmed. It is considered that the SiO ₂ adhered to the lower portion of the conical portion dropped on the surface of the melt, causing dislocation of the single crystal, and the single crystallization ratio was reduced to 82%.

[0041]

In the single crystal pulling apparatus according to the present invention, the radiation shield is formed as a triple layer, so that heat radiation from the melt surface and the radiation shield to the single crystal is effectively blocked, and the vertical axis of the single crystal. The temperature gradient in the direction becomes large, and a crystal with a high single crystallization ratio can be pulled at a high speed. In addition, a chamfered portion is provided in the communicating portion between the ventilation passages, and the ventilation passage is expanded to perform sufficient exhaust, thereby enabling a crystal to be pulled with a higher single crystallization rate, and a SiO ₂ radiation shield. To prevent radiation from sticking to the radiation shield, prolong the life of the radiation shield, and prevent the SiO ₂ adhered to the radiation shield from falling on the melt surface to prevent the dislocation of the single crystal from being induced, thereby increasing the single crystal crystallization rate. Crystal pulling is possible.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a single crystal pulling apparatus according to the present invention.

FIG. 2 is an enlarged sectional view showing a main part of FIG. 1;

FIG. 3 is an enlarged sectional view showing a main part of the embodiment other than the single crystal pulling apparatus according to the present invention.

FIG. 4 is a schematic diagram of a conventional single crystal pulling apparatus.

FIG. 5 is a schematic diagram of a conventional single crystal pulling apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Single crystal pulling apparatus 2 Furnace body 3 Fused silicon 4 Quartz glass crucible 5 Graphite crucible 6 Heater 7 Crucible rotation axis 8 Seed 9 Wire 10 Radiation shield 11 Inner surface part 12 Opening part 13 Melt surface 14 Horizontal part 15 Inner surface 16 Direct Body 17 Hollow part 18 Insulating material 19 Communication part (arc part) 20 Single crystal 21 Center line 22 End part 23 End part 24 Annular rim part 25 Annular rim part 26 Support part 27 Insulating material 28 Hollow part 30 Wall surface 31 Side wall 32 Ventilation Path 33 Ventilation path 34 Ventilation path 35 Attachment part 36 Exhaust port 37 Furnace bottom 38 Single crystal pulling device 39 Quartz glass crucible 40 Silicon melt 41 Radiation shield 42 Single crystal 43 Opening 44 Conical part 45 Straight body part 46 Thermal insulation material 47 Horizontal section 48 Inclined section 50 Wall section 51 Side wall 52 Ventilation path 53 Rotating shaft 54 Melt surface 55 Ventilation path 5 Reference Signs List 6 inner wall surface 57 ventilation path 58 furnace body 59 corner part 60 single crystal pulling device 61 quartz glass crucible 62 silicon melt 63 melt surface 64 single crystal 65 radiation shield 70 radiation shield 71 single crystal pulling device 72 inner surface 73 outer surface Side 74 Surface of melt 75 Insulation material 76 Lower end 77 Quartz glass crucible 78 Inner wall surface 79 L-shaped part

Claims (5)

[Claims] 1. A single crystal pulling apparatus for heating a quartz glass crucible provided in a furnace body to melt polysilicon loaded in the quartz glass crucible and pull up a semiconductor single crystal, wherein the quartz glass crucible is A radiation shield is installed above, and this radiation shield communicates with the inverted truncated cone-shaped conical portion having an opening through which the single crystal penetrates, and communicates with the lower end of the conical portion. Extending toward
And forming an air passage between a horizontal portion provided to face the polysilicon melt surface so as to form an air passage between the polysilicon melt surface and the inner surface of the quartz glass crucible. And a heat insulating material filled in a hollow portion formed by the cylindrical portion, the conical portion, and the horizontal portion. The cylindrical portion directly faces the inner surface of the quartz glass crucible. A single crystal pulling apparatus, characterized in that a chamfered portion is provided in the communicating portion of the body so that the straight body is reduced in diameter toward the center line of the single crystal. 2. The single crystal pulling apparatus according to claim 1, wherein the chamfered portion is formed by an arc portion. 3. The chamfered portion is formed by an arc portion, and the radius of curvature of the arc portion is defined by a ventilation path formed between the surface of the polysilicon melt and the horizontal portion, the inner surface of the quartz glass crucible, and the straight body portion. 2. The single crystal pulling apparatus according to claim 1, wherein the distance is larger than a spatial distance of an air passage formed therebetween. 4. The single crystal pulling apparatus according to claim 1, wherein the chamfered portion is formed by an inclined portion. 5. The chamfered portion is formed by an inclined portion, and a horizontal projection length and a vertical projection length of the inclined portion are determined by a ventilation path formed between the surface of the polysilicon melt and the horizontal portion and a quartz glass crucible. 5. The single crystal pulling apparatus according to claim 4, wherein the distance is larger than a space distance of an air passage formed between the inner surface and the straight body portion.