JP5888264B2 - Manufacturing method of semiconductor single crystal - Google Patents

Description

  The present invention is based on the FZ method (floating zone method or floating zone melting method) in which a raw crystal is partially heated and melted by an induction heating coil to form a floating zone and a single crystal is grown by moving the floating zone. More particularly, a semiconductor single crystal in which a single crystal is manufactured by moving the floating zone, and a semiconductor single crystal is grown by alternately changing the rotation direction of the growing semiconductor single crystal. It relates to the manufacturing method.

FIG. 6 is a schematic diagram showing an example of a conventional FZ method single crystal manufacturing apparatus. A method for producing a single crystal using the FZ single crystal apparatus 60 will be described.
First, the raw crystal rod 1 is held on the upper holding jig 4 of the upper shaft 3 installed in the chamber 11. On the other hand, a single crystal seed (seed crystal) 8 having a small diameter is held by the lower holding jig 6 of the lower shaft 5 located below the raw crystal rod 1.

  Next, the raw material crystal rod 1 is melted by the induction heating coil 7 and fused to the seed crystal 8. Thereafter, the narrowed portion 9 is formed by seed drawing to make dislocation-free. Then, by rotating the upper shaft 3 and the lower shaft 5 while lowering the raw crystal rod 1 and the single crystal rod 2, the floating zone (referred to as a melting zone or melt) 10 is formed between the raw crystal rod 1 and the grown single crystal rod 2. The crystal diameter is gradually increased to form the cone portion 2a. Thereafter, the straight body portion 2 b is formed, and the floating zone 10 is moved to the upper end of the raw crystal rod 1 to perform zoning to grow the single crystal rod 2.

This single crystal growth is performed in an inert gas atmosphere, and in order to produce an n-type FZ single crystal or a p-type FZ single crystal, the conductivity type and resistivity produced by a dope nozzle (not shown). An amount of inert gas based PH ₃ or B ₂ H _{6 according} to

  As the induction heating coil 7, an induction heating coil in which water for cooling copper or silver is circulated is used, for example, the one shown in FIG. The induction heating coil 7 has asymmetry because the heating in the vicinity of the slit 31 on the connection part 30 side with the high frequency oscillator is stronger than the other parts.

  Here, in order to reduce the variation in the wafer resistivity, the rotating shafts of the raw material rod 1 and the single crystal rod 2 are shifted (eccentric) to agitate the melt. In addition, a method in which the direction of rotation of the single crystal (on the lower shaft side) is rotated alternately between forward rotation and reverse rotation (hereinafter referred to as alternate rotation) is performed (for example, Patent Document 1).

  This alternate rotation is performed from the single-crystal cone portion 2a, and the alternate rotation condition in the cone portion is the same as that of the straight body portion, that is, the number of forward and reverse rotations is the same as that of the straight body portion. By rotating alternately from the cone part, a stable in-plane resistivity distribution can be obtained from the starting position of the straight body part, and the required quality of the entire straight body can be obtained.

JP 2012-148953 A

  However, for the purpose of obtaining a stable in-plane resistivity distribution from the starting position of the straight body of the single crystal, when the semiconductor single crystal (on the lower axis side) is rotated alternately from the cone portion of the single crystal, it is reversed from normal rotation, It was found that the growth unevenness occurred in the single crystal cone due to the temperature difference in the circumferential direction of asymmetric heating due to the influence of the slit of the induction heating coil when switching from reverse rotation to normal rotation. Therefore, if the same alternating rotation condition is used for the cone part where the product of the semiconductor single crystal cannot be obtained as in the prior art and the straight body part to be the product, the single crystal growth unevenness in the cone part becomes large. As a result, there is a problem that the possibility of dislocations in the cone portion increases.

  The present invention has been made in view of the above problems, and in the alternate rotation on the single crystal side for the purpose of obtaining a stable in-plane resistivity distribution from the starting position of the straight body of the single crystal by the FZ method. During semiconductor cone growth, the semiconductor single crystal can be manufactured stably by improving the growth unevenness of the semiconductor single crystal due to the influence of asymmetric heating of the induction heating coil when switching from forward rotation to reverse rotation and from reverse rotation to forward rotation. It aims at providing the manufacturing method of a crystal | crystallization.

  In order to achieve the above-described object, the present invention forms a melting zone by partially heating and melting a raw material crystal while rotating it with an induction heating coil, and the melting zone is moved from one end portion to the other end portion of the raw material crystal. In the method of manufacturing a semiconductor single crystal by the FZ method in which the rotation direction of the growing semiconductor single crystal is alternately changed when growing the semiconductor single crystal by moving, the alternating rotation in the growth of the cone portion of the semiconductor single crystal The number of rotations of normal rotation and reverse rotation of the semiconductor single crystal is increased from the number of rotations of normal rotation and reverse rotation of alternating rotation in the growth of the straight body portion of the semiconductor single crystal, and the semiconductor single crystal is grown. A manufacturing method is provided.

  Thus, the number of rotations of normal rotation and reverse rotation under alternating rotation conditions in single crystal cone growth is increased from the number of rotations of normal rotation and reverse rotation in alternating rotation conditions in single crystal straight body growth to increase the number of rotations of the semiconductor single crystal. The semiconductor single crystal has improved in-plane resistivity distribution from the starting position of the straight body portion in the straight body portion of the single crystal while improving the uneven growth of the single crystal at the single crystal cone portion. Can be manufactured stably.

Moreover, in this invention, it is preferable to make it transfer to the conditions of the alternating rotation in the growth of the straight body part of the said semiconductor single crystal, changing the conditions of alternating rotation continuously during the growth of the cone part of the said semiconductor single crystal.
In this way, in the growth process of the single crystal cone part, the condition of the alternating rotation in the growth of the single crystal straight cylinder part is continuously changed from the middle of the cone part formation to immediately before the straight cylinder part while changing the condition of the alternating rotation continuously. By shifting, it becomes possible to produce a more stable single crystal.

Furthermore, in the present invention, during the growth of the cone portion of the semiconductor single crystal, a program for automatically changing the conditions for alternating rotation according to the diameter of the cone portion during the growth of the semiconductor single crystal can be used.
Thereby, the change of the alternating rotation conditions from a cone part to a straight body part can be performed easily.

  As described above, according to the present invention, it is possible to obtain a stable in-plane resistivity distribution from the starting position of the straight body portion of the single crystal by alternating rotation on the single crystal side, and from forward rotation during the cone portion growth. To provide a method for manufacturing a semiconductor single crystal that can improve the unevenness of growth of a semiconductor single crystal due to the influence of asymmetric heating of an induction heating coil when switching from reverse rotation to reverse rotation, and that can stably manufacture a semiconductor single crystal. it can.

It is the figure which showed Table 1 in the graph in order to compare an Example and a comparative example about the relationship of the rotation frequency of the single crystal (lower shaft side) with respect to the diameter of a single crystal. It is the schematic which shows an example of the induction heating coil in a prior art. It is the figure which showed an example of the relationship of the frequency | count of inversion per 3 minutes during cone part growth with respect to the diameter of the single crystal of this invention and a prior art. It is the figure which showed the fluctuation | variation of the floating zone to single crystal diameter 150mm-160mm in this invention with the graph. It is the figure which showed the fluctuation | variation of the floating zone to the single crystal diameter 150mm-160mm in a prior art with a graph. It is the schematic which shows an example of the FZ method single crystal manufacturing apparatus in a prior art.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings, but the present invention is not limited thereto. Incidentally, since the single crystal manufacturing apparatus used in the method for manufacturing a semiconductor single crystal according to the present invention can be a conventional apparatus as shown in FIG. 6, the apparatus also refers to FIG. 6 in the present invention. I will do it.

First, a raw material crystal 1 is prepared by processing a portion of the raw material crystal rod that starts melting into a cone shape and etching the surface in order to remove processing distortion.
The diameter of the raw crystal 1 can be set to, for example, 100 to 205 mm, but is not limited thereto, and can be determined and selected by those skilled in the art.

Next, the prepared raw material crystal 1 is accommodated in the chamber 11 of the single crystal manufacturing apparatus 60 by the FZ method shown in FIG. 6, and the upper holding jig 4 of the upper shaft 3 installed in the chamber 11 is screwed or the like. Fix it.
On the other hand, a seed crystal 8 is attached to the lower holding jig 6 of the lower shaft 5, and an induction heating coil 7 is electrically connected to the high-frequency oscillator 12. Next, the lower end of the cone portion of the raw crystal 1 is preheated with a carbon ring (not shown), and then an inert gas is supplied to the chamber 11 to make it pressurized.

  Then, after the raw material crystal 1 is heated and melted by the induction heating coil 7, the tip of the cone portion of the raw material crystal is fused to the seed crystal 8, the dislocation is made by the narrowed portion 9, and the upper shaft 3 and the lower shaft 5 are rotated. The single crystal 2 is grown by moving the floating zone 10 to the upper end of the raw crystal 1 by lowering the raw crystal 1 and the grown single crystal 2 at a speed of, for example, 1 to 5 mm / min.

Further, in order to manufacture an n-type FZ single crystal or a p-type FZ single crystal, an inert gas base PH ₃ or B ₂ H _{6 in} an amount corresponding to the conductivity type and resistivity to be manufactured by a dope nozzle (not shown). May be used.
In addition, the resistivity, diameter, and straight cylinder length of the single crystal 2 to be manufactured are, for example, a single crystal resistivity of 1 to 5000 Ωcm, a single crystal diameter of 100 to 205 mm, and a straight cylinder length of 10 to 150 cm. However, the present invention is not limited to these and can be appropriately selected and determined by those skilled in the art.

  At this time, the upper shaft 3 serving as the rotation center of the raw crystal 1 when growing the single crystal and the lower shaft 5 serving as the rotation center of the growing single crystal 2 during the single crystallization are shifted (eccentric). It is preferable to grow a single crystal. By shifting both the central axes in this manner, the melted portion can be stirred during single crystallization, and the quality of the single crystal to be produced can be made uniform. The eccentricity in the eccentricity is appropriately selected and set by those skilled in the art according to the diameter of the single crystal, and is not limited thereto, but can be set to, for example, 10 mm.

  As shown in FIG. 1, the number of rotations of alternating rotation and rotation in the growth of the single crystal cone portion 2a is the same as the number of rotations of alternating rotation and rotation in the growth of the straight body portion 2b of the semiconductor single crystal. The semiconductor single crystal 2 is grown further. That is, the number of inversions of the cone part 2a is made smaller than the number of inversions of the straight body part 2b (see FIG. 3). However, in order to smoothly shift to the growth of the straight body portion, immediately before the straight body portion, the number of forward and reverse rotations (or the number of inversions) due to the alternate rotation of the cone portion 2a and the alternate rotation of the straight body portion 2b. There may be a case where the number of forward rotations and the number of rotations of reverse rotation (or the number of reverse rotations) are the same.

  As a result, when the single crystal side is rotated alternately for the purpose of obtaining a stable in-plane resistivity distribution from the starting position of the straight body portion when growing the single crystal by the FZ method, the cone portion where the product cannot be obtained conventionally is obtained. Since the alternate rotation condition was the same as the alternate rotation condition of the straight body part, the growth at the single crystal cone part when switching from normal rotation to reverse rotation and from reverse rotation to normal rotation in the alternate rotation due to the influence of asymmetric heating of the induction heating coil The frequency of occurrence of unevenness is the same as that of the straight body part, and there is a problem that the cone part is more likely to be dislocated and the dislocation frequency is higher than that of the straight body part. Therefore, it is possible to reduce the reversal frequency from the forward rotation to the reverse rotation and from the reverse rotation to the normal rotation in the cone portion, and to improve the degree of growth unevenness, and to reduce the dislocation in the cone portion. It is possible.

When alternately rotating during the growth of the semiconductor single crystal cone portion, as shown in FIG. 1, the number of rotations of the alternating rotation in the normal rotation and the reverse rotation in the growth of the single crystal cone portion 2a is set as the straight body portion 2b of the semiconductor single crystal. It is preferable to shift to the condition of the alternating rotation in the growth of the straight body portion of the semiconductor single crystal while continuously changing the condition of the alternating rotation while increasing the number of rotations of the alternating rotation in the normal rotation and the reverse rotation.
In this way, in the growth process of the single crystal cone part, the condition of the alternating rotation in the growth of the single crystal straight cylinder part is continuously changed from the middle of the cone part formation to immediately before the straight cylinder part while changing the condition of the alternating rotation continuously. By shifting, it becomes possible to produce a more stable single crystal.

In addition, during the growth of the cone portion of the semiconductor single crystal, when shifting to the alternate rotation condition in the growth of the single crystal straight body portion while continuously changing the alternate rotation condition as described above, By using a program that automatically changes the conditions of alternating rotation according to the diameter of the cone portion of the crystal, it is possible to easily change the alternating rotation conditions from the cone portion to the straight body portion.
This program may be incorporated in a control unit that controls the number of rotations of the lower shaft, or a control unit that separately contains the program may be prepared.

EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated more concretely, this invention is not limited to these.
(Example)
Using the single crystal manufacturing apparatus 60 shown in FIG. 6, zoning is performed by the FZ method using a CZ silicon single crystal of 1000 Ωcm or more as a raw material crystal rod, and 20 silicon single crystals having a diameter of 200 mm are manufactured.
First, an inert gas was flowed into the chamber 11, the furnace pressure was increased, the growth rate was 2.0 mm / min or less, and the lower shaft 5 was eccentric. Doping was performed by spraying an inert gas-based PH ₃ onto the floating zone with a dope nozzle (not shown) to produce an n-type silicon single crystal of 50 Ωcm.
At this time, as shown in Table 1 below, alternate rotation conditions different from those of the straight body portion were adopted in the cone portion where the product could not be acquired.

  Specifically, the growth condition of the cone part is a condition that the reversal frequency is less than that of the straight body part, and as shown in Table 1, when the diameter of the cone part is 150 mm, the single crystal starts to rotate alternately. The number of rotations of the rotation was 20 rotations in the forward rotation, 19.2 rotations in the reverse rotation, and the rotation speed was 20 rpm. Thereafter, as shown in Table 1, the alternating rotation condition was continuously changed to shift to the alternating rotation condition in the straight body portion. The alternating rotation conditions in the straight body of the single crystal were 1.0 rotation for forward rotation, 0.2 rotation for reverse rotation, and a rotation speed of 20 rpm. In this condition, the average time was reversed once every about 3 seconds. Moreover, the program which changes an alternating rotation condition automatically according to the diameter of a single crystal was used.

As evaluation items, the number of inversions per 3 minutes of the single crystal, the degree of growth unevenness (fluctuation in the floating zone length), and the success rate from the diameter of 150 mm at which the cone portion alternately starts to the diameter at the end of the cone portion of 200 mm were investigated. .
When the diameter of the cone portion is 150 mm, the average time is reversed once every about 60 seconds (the rotation amount is 20 rotations in the normal rotation, 19.2 rotations in the reverse rotation, and the rotation speed is 20 rpm). Compared with the conditions (rotation amount in forward rotation is 1.0 rotation, rotation in reverse rotation is 0.2 rotation, rotation speed is 20 rpm), the frequency of occurrence of single crystal growth unevenness in the cone portion is about 1/20.

Further, as shown in FIG. 4, the variation of the floating zone length (single crystal side) 20 from 150 to 160 mm in diameter of the cone portion, that is, the variation width of the single crystal growth unevenness was 4.4%. By increasing the number of rotations, the rotational speed of the melt part, which is a floating zone, is increased, and the degree of uneven growth of the single crystal is less affected by the circumferential temperature difference of the asymmetric heating of the induction heating coil. This is because it has become smaller.
Further, in this example, the success rate from the diameter of 150 mm at which the cone portion began to rotate to the diameter at the end of the cone portion of 200 mm was 17 out of 20 times (success rate 85%).

  However, the degree of uneven growth of the single crystal was measured as follows. In other words, when the single crystal is rotated alternately from forward to reverse and from reverse to forward, the asymmetry of the heating of the induction heating coil becomes significant, and the floating zone length (single crystal side) varies in the circumferential direction (growth). The degree of unevenness of single crystal growth was measured by measuring this degree with a CCD camera.

(Comparative example)
Using the single crystal manufacturing apparatus 60 shown in FIG. 6, zoning was performed by FZ method using a CZ silicon single crystal of 1000 Ωcm or more as a raw material crystal rod, and 20 silicon single crystals having a diameter of 200 mm were manufactured.
First, an inert gas was flowed into the chamber 11, the furnace pressure was increased, the growth rate was 2.0 mm / min or less, and the lower shaft 5 was eccentric. Doping was performed by spraying an inert gas-based PH ₃ onto the floating zone with a dope nozzle (not shown) to produce an n-type silicon single crystal of 50 Ωcm.

  In the cone part where the product could not be obtained, the same alternating rotation conditions as in the case of the straight body part were used as shown in Table 1, and when the diameter of the cone part reached 150 mm, the single crystal alternate rotation was started. The alternating rotation conditions of the single crystal in the cone part and the straight body part were 1.0 rotation for forward rotation, 0.2 rotation for reverse rotation, and a rotation speed of 20 rpm. In the case of this condition, the average time is reversed once every about 3 seconds.

Evaluation items are the number of inversions per 3 minutes of single crystal, the degree of growth unevenness (fluctuation of floating zone length (single crystal side) 20), the diameter of 150 mm from the start of alternate rotation of the cone part to the diameter of 200 mm at the end of cone part The success rate was investigated.
As shown in FIG. 3, the reversal frequency of the single crystal per 3 minutes is about 27 times from the diameter of the cone portion where the alternate rotation starts to 150 mm to the straight body.

As shown in FIG. 5, the variation of the floating zone length (single crystal side) 20 from the cone portion diameter of 150 mm to 160 mm, that is, the variation width of the single crystal growth unevenness was 5.3%.
In addition, the success rate from the diameter of 150 mm at which alternate rotation of the cone portion started to the diameter of 200 mm at the end of the cone portion was 13 out of 20 successes (success rate 65%).
However, the degree of uneven growth of the single crystal was measured in the same manner as in the examples.

  Comparing the example and the comparative example, by adopting the condition of the alternate rotation in the cone part of the present invention, when the cone part has a diameter of 150 mm, the number of inversions per 3 minutes of the single crystal becomes about 1/20. It was. At the same time, the rotation speed of the melt part, which is the floating zone, increases due to the increase in the number of rotations, and the floating zone length (single crystal side) 20 becomes less susceptible to the influence of the circumferential temperature difference of the asymmetric heating of the induction heating coil. The variation (growth unevenness) in the circumferential direction was improved by 0.9% (comparison between FIG. 4 and FIG. 5). These effects result in a 20% improvement in the success rate from the diameter of 150 mm at which the cone portion begins to rotate to the diameter at the end of the cone portion of 200 mm. A stable in-plane resistivity distribution was obtained from the starting position of the straight body of the crystal.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

DESCRIPTION OF SYMBOLS 1 ... Raw material crystal, 2 ... Semiconductor single crystal, 2a ... Cone part, 2b ... Straight trunk | drum part,
3 ... Upper shaft, 4 ... Upper holding jig, 5 ... Lower shaft, 6 ... Lower holding jig,
7 ... Induction heating coil, 8 ... Seed crystal, 9 ... Drawing part, 10 ... Floating zone,
11 ... chamber, 12 ... high frequency oscillator, 20 ... floating zone length (single crystal side),
30 ... Connection part with high frequency oscillator, 31 ... Slit, 60 ... Single crystal manufacturing apparatus.

Claims (3)

When growing a semiconductor single crystal by forming a melt zone by partially heating and melting the raw material crystal while rotating it with an induction heating coil, and moving the melt zone from one end to the other end of the raw material crystal In the method of manufacturing a semiconductor single crystal by the FZ method in which the rotation direction of the growing semiconductor single crystal is alternately changed,
The number of rotations of alternating rotation and reverse rotation in the growth of the cone portion of the semiconductor single crystal is increased from the number of rotations of alternating rotation and reverse rotation in the growth of the straight body portion of the semiconductor single crystal. A method for producing a semiconductor single crystal, characterized in that:   2. The condition of alternating rotation in the growth of the straight body portion of the semiconductor single crystal is shifted to the condition of alternating rotation during continuous growth of the cone portion of the semiconductor single crystal. The manufacturing method of the semiconductor single crystal of description.   3. The program according to claim 2, wherein during the growth of the cone portion of the semiconductor single crystal, a program for automatically changing the condition of alternating rotation according to the diameter of the cone portion during the growth of the semiconductor single crystal is used. A method for producing a semiconductor single crystal.

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