JP2000313693A - Thermal conduction type seed crystal for producing semiconductor single crystal and growth of single crystal by the thermal conduction type seed crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for growing a single crystal by immersing a seed crystal in a melt and pulling and growing the single crystal without causing necking in the production of a semiconductor single crystal by a Czochralski method. SOLUTION: This thermal conduction type seed crystal 10 is constituted of a growing seed 1 whose lower end is immersed in a melt to grow a semiconductor single crystal, a thermal conduction member 2 which is attached to the growing seed 1 and immersed in the melt before the growing seed 1 is immersed in the melt to transfer the heat of the melt to the growing seed 1 and a quartz cylinder 3 for covering the thermal conduction member 2. The thermal conduction member 2 is attached to the growing seed 1 so as to surround the growing seed and has plural slits 2c arranged in the vertical direction from the lower part to the bottom part. The quartz cylinder 3 has the same number of inverted wedge-shaped notch parts as that of the slits 2c and wedge- shaped parts 3b formed between two adjoining notch parts are mutually different in length in the vertical direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermally conductive seed crystal used for producing a semiconductor single crystal by the Czochralski method and a method for growing a single crystal using the thermally conductive seed crystal.

[0002]

2. Description of the Related Art Single crystal silicon is generally manufactured by the Czochralski method. In the Czochralski method, polycrystalline silicon is filled in a quartz crucible provided in a single crystal manufacturing apparatus, and the polycrystalline silicon is heated and melted by a heater provided around the quartz crucible to form a melt. Then, the seed crystal attached to the seed holder is immersed in the melt, and the seed holder is pulled up while rotating the seed holder and the quartz crucible in the same or opposite directions to grow single crystal silicon to a predetermined diameter and length. .

When a seed crystal is immersed in a melt, thermal stress is generated and dislocation occurs in the seed crystal. In order to remove the dislocation, a neck portion having a diameter of about 3 to 4 mm is formed below the seed crystal by using a dash neck method, and the dislocation is released to the surface of the neck portion. Then, after the dislocation-free state is confirmed, the shoulder is formed to enlarge the single crystal to a predetermined diameter, and then the process shifts to the formation of a straight body.

In recent years, the weight of single crystals has increased with the increase in the diameter or the axial length of single crystals for the purpose of improving the efficiency of semiconductor device production, improving the yield, etc., and the strength of the neck portion has reached the limit. I have. Therefore, the neck portion may be broken by the conventional crystal pulling method, and a safe single crystal growth cannot be performed. As a countermeasure against this, the present inventors have proposed a method for producing a single crystal not using the dash neck method as disclosed in Japanese Patent Application No.
No.-51302 (not disclosed) proposes a seed crystal for producing a single crystal and a method for producing a single crystal. The seed crystal for producing a single crystal in this proposal is, for example, as shown in FIG.
Using the seed crystal, a seed 11 for growth and a hollow heat conducting member 12 having a through hole in the upper end surface and having an opening at the bottom are manufactured, and the seed 11 for heat conduction is produced. After fitting and inserting into the through hole in the upper end surface of the
The growth seed 11 is attached to the seed holder 5. As shown in FIG. 10, the heat conducting member 12 is immersed in the melt 6 before the growing seed 11, so that the heat of the melt 6 is The seed 11 for growth is transmitted to the seed 11 and immersed in the melt 6 after reaching a sufficiently high temperature. As a result, dislocation due to thermal shock does not occur in the growth seed 11, and the dislocation introduced into the heat conducting member 12 does not propagate to the growth seed 11. In this state, as shown in FIG. 11, the entire heat conducting member 12 is immersed in the melt 6 to dissolve it, and then the growing seed 11 is pulled up, thereby immediately expanding the single crystal without forming a neck at the lower end thereof. The work can be started, and the process can proceed to a shoulder forming step.

According to WO 97/32059, the seed crystal is surrounded by a heat insulating tube made of quartz, and the lower end of the heat insulating tube is immersed in the melt prior to the seed crystal to raise the temperature of the seed crystal. In addition, a thermal shock is prevented from occurring when the seed crystal is immersed in the melt.

[0006]

However, the above prior art has the following problems. Japanese Patent Application No. 10-51302
In the seed crystal for producing a single crystal disclosed in Japanese Patent Application Laid-Open Publication No. H11-133, the melt 6 penetrates into the fitting portion between the heat conduction member 12 and the growing seed 11 and solidifies in the process of melting the heat conduction member 12. As a result, there is a problem that the seeds 11 for growth grow into dislocations. In addition, at the end of the melting process of the heat conducting member 12, as shown in FIGS.
Occurs and floats around the growing seeds 11. Then, as shown in FIG. 14, when the needle-shaped dissolution residue 13 adheres to the seed 11 for growth, there is also a problem that the seed 11 for growth is dislocated. In addition, WO97 / 32
Since the bottom surface of the heat retention tube used in No. 059 is flat, the entire bottom surface is separated from the melt at once at the time of lifting, which causes a problem that the liquid surface is wavy and the growing single crystal is dislocated. is there.

The present invention has been made in view of the above-mentioned conventional problems. In the production of a semiconductor single crystal by the Czochralski method, after immersing a seed crystal in a melt, the single crystal is formed without necking. It is an object of the present invention to provide a thermally conductive seed crystal for producing a semiconductor single crystal, which can be grown and capable of pulling a heavy single crystal, and a method for growing a single crystal using the thermally conductive seed crystal.

[0008]

In order to achieve the above object, a first invention of a heat conductive type seed crystal for producing a semiconductor single crystal according to the present invention is to immerse a lower end in a melt to obtain a semiconductor single crystal. A seed for growing a crystal, a member for heat conduction attached to the outside of the seed for growth, and immersed in the melt prior to the seed for growth to conduct heat of the melt to the seed for growth; And a quartz tube covering the member. According to the first aspect of the heat conduction type seed crystal for producing a semiconductor single crystal, the heat conduction member is immersed in the melt before the growth seed, so that the heat of the melt is smaller in volume than the growth seed. It is conducted to the growing seed through a large heat conducting member. Therefore, the seed for growth is sufficiently preheated by the heat conducting member before the lower end thereof comes into contact with the melt,
The thermal shock during immersion in the melt is reduced, and no dislocation occurs. The dislocations introduced into the heat conducting member do not propagate to the seeds for growth that come into contact with the heat conducting member at the discontinuous surface. Further, the quartz tube does not dissolve even when immersed in the melt, and no crystal growth occurs. As described above, the growing seed does not need to form a neck portion to eliminate dislocations, and the process can proceed to the step of forming the straight body portion with the same diameter, so that a single seed having sufficient strength to withstand pulling of a heavy single crystal. The crystal holding part can be easily formed, and the productivity can be improved.

In a second aspect of the present invention, there is provided a heat conduction type seed crystal for producing a semiconductor single crystal, wherein the heat conduction member is mounted so as to surround a growing seed. In addition, a plurality of slits are provided in a vertical direction from a lower portion to a lower end portion. According to the second aspect of the heat conduction type seed crystal for producing a semiconductor single crystal, since a plurality of slits are provided in the heat conduction member in the up-down direction, the state in which the seed for growing is applied to the melt through these slits. And the growth state of the single crystal can be observed, and the workability in pulling the crystal is good. Further, the lower part of the heat conducting member is divided into a plurality of parts by the slit, and the crystal growing at the lower part of the heat conducting member at the time of pulling the crystal is also divided by the slit. Therefore, the crystal that grows below the heat conducting member is easily guided to the quartz tube, and the separation from the melt can be easily controlled by the quartz tube.

A third invention of a heat conduction type seed crystal for producing a semiconductor single crystal according to the present invention is the heat conduction type seed crystal according to the second invention, wherein the quartz cylinder has an inverted wedge shape having the same number as the number of slits of the heat conduction member. And the wedge-shaped portions formed between two adjacent notches have different vertical lengths. According to the third aspect of the heat conduction type seed crystal for producing a semiconductor single crystal, since the vertical lengths of the plurality of wedge-shaped portions provided in the quartz cylinder are different from each other, the seed crystal immersed in the melt can be used. In the process of pulling up with dislocations, the timings at which the lower ends of the wedge-shaped portions separate from the melt are shifted from each other. Therefore, the seed crystal can be pulled up without dislocation without rippling the melt. In addition, since the contact area of each wedge-shaped portion of the quartz cylinder with the melt decreases downward, the contact area between the crystal growing under the heat conducting member and the melt is reduced, and thus the fusion of the grown crystal is reduced. The liquid is easily drained when it is detached from the liquid, and the ripples are extremely small, so that dislocation-free is further facilitated.

According to a fourth aspect of the present invention, there is provided a heat conduction type seed crystal for producing a semiconductor single crystal, wherein the heat conduction type seed crystal according to the third invention is provided with a heat conduction member. The position of the slit is matched. According to the fourth invention of the heat conduction type seed crystal for producing a semiconductor single crystal,
Since the upper end position of the notch provided in the quartz tube and the position of the slit provided in the heat conducting member match, the slit of the heat conducting member is not covered by the quartz tube, and the quartz tube is attached. You can observe the seeds for growth. Thereby, workability at the time of pulling a single crystal can be improved.

In a first aspect of the present invention, there is provided a method for growing a single crystal using a heat-conducting seed crystal, wherein a heat-conducting member having a vertically extending slit extending from a lower portion to a lower end portion is mounted outside a growing seed. Further, the heat conducting member is covered with a quartz cylinder having an inverted wedge-shaped notch, and the slit of the heat conducting member is aligned with the upper end position of the notch of the quartz cylinder to form a heat conducting seed crystal. The heat conduction type seed crystal attached to the seed holder is lowered to a height at which the lower end of the growth seed for the heat conduction type seed crystal is immersed in the melt, and thereafter, a single crystal is grown at the lower end of the growth seed. While pulling up. According to the first aspect of the method for growing a single crystal using a heat-conductive seed crystal, the lower end of the seed for growth is lowered only to a height at which the seed for growth is immersed in the melt. The fitting part with the member for use is not immersed in the melt. Therefore, the melt does not penetrate into the fitting portion between the seed for growth and the member for heat conduction, and the floating needle-like residue generated when all the members for heat conduction are dissolved does not occur. Dislocation of the seed can be prevented. Since the seeds for growth do not generate dislocations due to thermal shock during immersion in the melt, necking is not required, and the process can immediately proceed to the shoulder forming step. Therefore, since the single crystal can be pulled up with the diameter of the seed for growth, a single crystal having sufficient strength to withstand a large weight can be easily manufactured, and productivity can be improved.

The second invention of the method for growing a single crystal using a heat conduction type seed crystal according to the present invention is the first invention of the method for growing a single crystal using a heat conduction type seed crystal according to the first invention. The amount of the crystal grown at the lower end of the conducting member is guided by the wedge-shaped portion formed between the cutouts of the quartz cylinder and decreasing in contact with the melt downward, and the lower end of the wedge-shaped portion is guided. To separate from the melt. According to the second invention of the method for growing a single crystal using a heat conduction type seed crystal, the crystal that grows at the lower end of the remaining melted portion by immersing the heat conduction member in the melt is thermally conductive as the single crystal is pulled up. As the wedge-shaped part of the quartz cylinder on the outside of the
As the contact area with (6) is reduced, it is induced to form a wedge, and detaches from the melt without waving at the lower end of the wedge. Therefore, the single crystal growing under the seed for growth can be pulled up without dislocation.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. The heat conductive type seed crystal for producing a semiconductor single crystal according to the present invention includes a seed for growing, a heat conductive member, and a quartz tube. As shown in FIG. 1, the seed 1 for growth comprises an upper portion 1a having a diameter substantially equal to that of a normal seed crystal and a lower portion 1b having a larger diameter than the upper portion 1a.
The upper portion 1a is provided with a locking portion 1d attached to a seed holder (not shown).

The heat conducting member 2 is made of the same material as the seed 1 for growth, and is opened downward as shown in FIG. 2 (a) and FIG. 2 (b) which is a bottom view of FIG. 2 (a). A large-diameter hole 2a which has a substantially hollow cylindrical shape, is provided inside the heat conducting member 2, and accommodates the lower portion 1b of the growing seed 1 shown in FIG. A tapered hole 2b provided and into which the tapered portion 1c of the growing seed 1 is inserted.
And The heat conducting member 2 includes a plurality of members (4 in this embodiment) parallel to the axial direction from the lower end of the large-diameter hole 2a.
) Slits 2c. Width W of slit 2c
Has a size sufficient for observing the lower portion 1b of the seed 1 for growth when the member 2 for heat conduction is fitted to the seed 1 for growth.

As shown in FIG. 3, the quartz cylinder 3 is made of a member made of high-purity quartz that covers the upper surface and the outer peripheral surface of the heat conducting member 2, and a plurality of (in the embodiment, 4
Cutouts 3a are provided. Notch 3
a has an inverted wedge shape in which the lower end is wide and gradually narrows upward, and the number of the cutouts 3 a is the same as the number of the slits 2 c of the heat conducting member 2. The upper end of the notch 3a is provided at a position corresponding to the slit 2c of the heat conducting member 2 when the quartz tube 3 is covered with the heat conducting member 2. A wedge-shaped portion 3 is provided between these notches.
b are formed, but the wedge-shaped portions 3b adjacent to each other have different axial lengths. The upper end of the quartz tube 3 is provided with a hole 3c through which the upper part 1a of the growing seed 1 passes. The quartz used as the material of the quartz tube 3 according to the present invention has high purity,
There are a transparent type and an opaque type, and any type may be used.

When the heat conducting member 2 is fitted to the growing seed 1 and the quartz tube 3 is put on the heat conducting member 2, the heat conducting type seed crystal 10 shown in FIG. 4 is completed.

FIGS. 5 to 8 show a procedure for pulling a single crystal using the heat conduction type seed crystal of the present invention. As shown in FIG. 5, the heat conduction type seed crystal 10 is attached to the seed holder 5 connected to the lower end of the pull-up shaft 4, and is lowered toward the melt 6. The lower end of the use member 2 and a part of the quartz cylinder 3, that is, a part of the wedge-shaped part having a long axial length, first contacts the melt 6, and then each wedge-shaped part of the quartz cylinder 3 contacts the melt 6. At this time, the heater power and the quartz crucible rotation number are adjusted while observing the melting state of the heat conduction member 2 so that the melt temperature of the heat immersion part of the heat conduction member 2 continues to be smoothly melted. . During this time, the temperature of the melt 6 through the melting of the heat conducting member 2 is reduced.
From the seed for growth 1
Temperature rises to a remarkably high temperature range as compared with the case where the seed for growth 1 alone is brought close to the surface of the melt 6, and the temperature difference between the melt 6 and the seed for growth 1 becomes extremely small.

When the lifting shaft 4 is further lowered, the seeds 1 for growth are immersed in the melt 6 as shown in FIG. By this time, since the growth seed 1 has received sufficient heat conduction from the melt 6 via the heat conduction member 2, the thermal shock at the time of immersion in the melt is greatly reduced, and no dislocation is introduced. Then, in this state, the temperature of the melt is adjusted so as to maintain a temperature at which the diameter of the growing seed 1 does not change. The fitting portion between the growing seed 1 and the heat conducting member 2 is not immersed in the melt 6.

After the growing seed 1 has been blended into the melt 6,
When the heat conduction type seed crystal 10 is raised, crystals grow at the lower ends of the seeds 1 for growth and the members 2 for heat conduction, respectively, as shown in FIG. Of these, since no dislocation has been introduced into the silicon growth portion 7 that grows at the lower end of the seed 1 for growth, there is no need to enter the necking step, and the process immediately proceeds to the step of forming the shoulder 8 as shown in FIG. Then, a single crystal is grown as in a normal process. On the other hand, the heat conducting member 2
Since the silicon growth portion 9 growing at the lower end of the crystal is guided by the wedge-shaped portion provided in the quartz cylinder 3 by gradually reducing the contact with the melt, the contact area with the melt 6 gradually decreases. This facilitates separation from the melt 6. Also, silicon does not grow on the quartz tube 3. For this reason, the crystal grown at the lower end of the dissolved residual portion of the heat conducting member 2 is separated from the melt 6 almost at the same time when each wedge-shaped portion 3 b of the quartz tube 3 separates from the melt 6. In addition, since the wedge-shaped portions 3b of the quartz cylinder 3 have different axial lengths, the timing of separation from the melt 6 at the lower ends of the individual wedge-shaped portions is not simultaneous, so that the vibration of the melt surface is extremely small. Can be suppressed.

In the above embodiment, the heat conduction member is immersed and melted in the melt to sufficiently conduct heat conduction to the growth seed, and the temperature of the growth seed is increased before coming into contact with the melt. be able to. As a result, the thermal shock when the seed for growth is immersed is reduced, and the seed for growth can be immersed without introducing dislocation. When the heat conduction type seed crystal is raised from this position, crystals grow at the respective lower ends of the growth seed and the heat conduction member, but contact the melt downward on the outside of the heat conduction member. Since there is a quartz cylinder having a wedge-shaped portion in which is gradually reduced, crystal growth directed downward from the lower end of the heat conducting member is guided to the quartz cylinder, and the cross-sectional area thereof is gradually reduced. Further, since the adjacent wedge-shaped portions of the quartz cylinder have different axial lengths, the quartz tubes are sequentially separated from the melt from a short portion. Therefore, the melt vibration when the quartz tube and the crystal grown at the lower end of the heat conducting member are separated from the melt is minimized, and only the single crystal growing at the lower end of the seed for growth is immersed. Create a state that you are doing. Since the seeds for growth are immersed in a dislocation-free state, it is possible to directly shift to the shoulder forming step without going through the necking step. Since necking is not performed, the cross-sectional area of the seed crystal is maintained as it is, and the cross-sectional area can support the grown single crystal. WO 97/32059
Since the bottom surface of the heat retaining tube is flat in the case, when the heat retaining tube separates from the melt during the growth of the single crystal, the melt may undulate, and the single crystal during the growth may be dislocated. Then there is no fear. Further, if the heater power and the number of rotations of the quartz crucible are adjusted, the detachment can be easily controlled.

As described above, according to the present invention, the following effects can be obtained. (1) Since the growth seed is sufficiently preheated and then immersed in the melt, the introduction of dislocation due to thermal shock does not occur, and the necking step by the dash method becomes unnecessary. Therefore, the minimum diameter of the single crystal is substantially equal to the diameter of the seed crystal, and the weight of the single crystal that can be pulled increases, so that productivity can be improved. (2) Since the upper part of the heat conduction type seed crystal is not immersed in the melt,
The melt penetrates into the fitting portion between the seed for growth and the member for heat conduction, and the seed for growth is dislocated, or needle-like dissolution residue generated when the member for heat conduction is melted adheres to the seed for growth. Problems such as dislocations are solved, and a high-quality single crystal can be manufactured.

[Brief description of the drawings]

FIG. 1 is a perspective view of a growing seed.

2A and 2B show a heat conducting member, wherein FIG. 2A is a perspective view and FIG.
Is a bottom view.

FIG. 3 is a perspective view of a quartz tube.

FIG. 4 is a perspective view of a heat conduction type seed crystal.

FIG. 5 is an explanatory view of a procedure for pulling a single crystal using a heat conduction type seed crystal, and shows a state where the heat conduction type seed crystal is brought close to a melt.

FIG. 6 is an explanatory view of a state where the heat conduction type seed crystal is immersed in a melt.

FIG. 7 is an explanatory view of a state in which the pulling of the heat conduction type seed crystal is started.

FIG. 8 is an explanatory view showing a state in which a single crystal is grown at the lower end of a seed for growing a thermally conductive seed crystal.

FIG. 9 is an explanatory view of a state where a seed crystal according to a conventional technique is brought close to a melt.

FIG. 10 is an explanatory view showing a state in which a lower part of a heat conducting member of a seed crystal is immersed in a melt.

FIG. 11 is an explanatory view showing a state where the entire heat conducting member of the seed crystal is immersed in a melt.

FIG. 12 is an explanatory diagram of a state in which needle-like dissolution residues have occurred around a seed for growing.

FIG. 13 is an explanatory view showing a state in which needle-like dissolved residues are floating around a seed for growth.

FIG. 14 is an explanatory view showing a state where needle-like dissolution residues adhere to the seeds for growth.

[Explanation of symbols]

1,11: seed for growing, 2,12: member for heat conduction, 2
c: slit, 3: quartz cylinder, 3a: cutout, 3b ...
Wedge-shaped portion, 5: seed holder, 6: melt, 7, 9: silicon growth portion, 10: heat conduction type seed crystal.

Claims (6)

[Claims] A seed for growing a semiconductor single crystal by immersing a lower end of the seed in a melt; and a seed mounted on the outside of the seed for growing, wherein the seed is located ahead of the seed for growing. A heat conducting member (2) that conducts the heat of the melt (6) to the seed for growth (1) by immersing it in the melt (6), and a quartz tube that covers the heat conducting member (2)
(3) A thermally conductive seed crystal for producing a semiconductor single crystal, comprising: 2. The heat conduction type seed crystal for producing a semiconductor single crystal according to claim 1, wherein the heat conduction member (2) is mounted so as to surround the growing seed (1), and extends from a lower portion to a lower end portion. A thermally conductive seed crystal for producing a semiconductor single crystal, wherein a plurality of slits (2c) are provided in a vertical direction. 3. The heat conduction type seed crystal for producing a semiconductor single crystal according to claim 2, wherein the quartz cylinder (3) has the same number of inverted wedge-shaped notches as the number of slits (2c) of the heat conduction member (2). A wedge-shaped portion (3b) formed between two adjacent notches (3a) having different lengths in the vertical direction. Conductive seed crystal. 4. A heat conduction type seed crystal for producing a semiconductor single crystal according to claim 3, wherein the plurality of notches (3) of the quartz cylinder (3) are provided.
A thermally conductive seed crystal for producing a semiconductor single crystal, characterized in that the upper end of (a) is aligned with the position of the slit (2c) of the thermally conductive member (2). 5. A seed for growing a heat conducting member (2) having a slit (2c) in a vertical direction from a lower portion to a lower end portion.
(1), and the heat conducting member (2) is further covered with a quartz tube (3) having an inverted wedge-shaped notch (3a), and the slit (2c) of the heat conducting member (2) is provided. And notch (3a) of quartz tube (3)
A heat conduction type seed crystal (10) is formed by matching the upper end position of the heat conduction type seed crystal (10) and attached to the seed holder (5).
The heat-conductive seed crystal (10) is lowered to a level where the lower end of the seed (1) for growth of (0) is immersed in the melt (6), and then a single crystal is grown on the lower end of the seed (1) for growth. A method of growing a single crystal using a heat conductive seed crystal, wherein the single crystal is pulled while being pulled. 6. The method for growing a single crystal using a heat-conductive seed crystal according to claim 5, wherein the amount of crystal grown at the lower end of the heat-conducting member (2) as the single crystal is pulled is reduced by quartz. It is guided by a wedge-shaped part (3b) formed between the notch part (3a) of the cylinder (3) and decreasing the contact with the melt (6) downward, and is guided by a lower end of the wedge-shaped part (3b). A method for growing a single crystal using a heat-conducting seed crystal, comprising separating the single crystal from a melt (6).