JP2010215431A - Method for producing semiconductor single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a semiconductor single crystal by an FZ method (a floating zone method or a floating zone melting method) controllable of an in-plane resistivity distribution of the produced semiconductor single crystal in the radial direction and particularly reducing the variation of in-plane resistivity. <P>SOLUTION: The method for producing the semiconductor single crystal by the FZ method using a gas doping technique for jetting at least a dopant gas toward a floating zone to dope the semiconductor single crystal with the dopant and obtain the desired resistivity. The semiconductor single crystal is produced beforehand and the in-plane resistivity distribution of the produced semiconductor single crystal in the radial direction is acquired at the least. When the semiconductor single crystal being a product is produced, the amount of the dopant to be used for doping the semiconductor single crystal being the product with the dopant by using the gas doping technique is adjusted according to the beforehand acquired in-plane resistivity distribution during the time to form a straight drum part thereof so that the in-plane resistivity distribution of the semiconductor single crystal being the product in the radial direction is controlled. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a semiconductor single crystal by the FZ method (floating zone method or floating zone melting method), and more specifically, a dopant gas is injected into the melting zone to cause the semiconductor crystal to have a desired electrical resistivity (hereinafter, The present invention relates to a method for manufacturing a semiconductor single crystal by an FZ method using gas doping.

The FZ method is used as one of methods for producing a semiconductor single crystal, for example, a silicon single crystal that is currently most frequently used as a semiconductor element.
Usually, in order to give a desired resistivity to a silicon single crystal, doping with N-type or P-type impurities is necessary. In the FZ method, a gas doping method in which a dopant gas is injected into a melting zone is known (see Non-Patent Document 1).

As the dopant gas, for example, PH ₃ or the like is used for doping P (phosphorus) which is an N-type dopant, and B ₂ H ₆ or the like is used for doping B (boron) which is a P-type dopant. The resistivity of the silicon single crystal varies depending on the concentration difference in the crystals of the N-type dopant and the P-type dopant, but when doping only the N-type dopant or only the P-type dopant in normal single crystal production, The resistivity decreases with increasing dopant doping.

  In order to obtain a silicon single crystal having a desired resistivity, it is necessary to appropriately adjust the doping amount of the dopant so as to obtain a desired resistivity in consideration of the resistivity of the raw material. As a result of manufacturing a single crystal by the FZ method while adjusting the concentration and flow rate (injection amount) of the supplied dopant gas and maintaining the dopant doping amount appropriately, an FZ silicon single crystal having a desired resistivity is obtained. Can be obtained.

  As a device of a gas doping method for obtaining a semiconductor single crystal by FZ method having a desired resistivity (sometimes referred to as FZ single crystal), by changing the doping gas concentration during the production of one semiconductor single crystal rod A growth axis of a raw material rod when a multi-doped FZ single crystal rod manufacturing method (see Patent Document 1) in which a plurality of resistivity portions are formed in one single crystal rod, or when a CZ silicon single crystal is used as a raw material rod There has been proposed an FZ method (see Patent Document 2) or the like in which the dopant doping amount by gas doping is changed in accordance with the change in resistivity along the direction.

  It is desired that a wafer manufactured from a silicon single crystal obtained by the FZ method has a small resistivity variation in the wafer surface and is as uniform as possible over the entire surface. Here, the uniformity of the in-wafer in-plane resistivity distribution is to make the in-plane resistivity distribution uniform in a cross section perpendicular to the growth axis direction of the FZ single crystal (that is, in the radial plane).

  In order to satisfy this requirement, a method of adjusting crystal manufacturing conditions within a predetermined range (for example, see Patent Document 3), a method of growing while alternately changing the rotation direction of a single crystal (for example, Patent Document 4), etc. are proposed. Thus, the resistivity in the wafer surface is made uniform.

Japanese Patent No. 2617263 JP 2008-87984 A Japanese Patent No. 2621069 Japanese Patent No. 2820027

“Floating-Zone Silicon” by WOLFGAN KELLER, ALFRED MUHLBAUER, p. 82-92, MARCEL DEKKER, INC. Issue

  In recent years, in the field of discrete devices and the like, in order to reduce the manufacturing cost, it is also required to increase the diameter of the wafer obtained from the material FZ silicon single crystal, and the demand for FZ silicon single crystal having a large diameter of 150 mm or more has increased. continuing.

  However, especially in the case of an FZ silicon single crystal having a diameter of 150 mm or more, using the methods as described in Patent Document 3 and Patent Document 4 is of course effective in reducing in-plane resistivity variation. This is sufficient, and the in-plane resistivity variation is larger than in the case of an FZ silicon single crystal having a diameter of 125 mm or less. Further, regardless of whether the diameter of the FZ silicon single crystal is enlarged, further reduction in in-plane resistivity variation is continuously demanded.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to control the in-plane resistivity distribution in the radial direction of a manufactured semiconductor single crystal, and particularly to a surface. An object of the present invention is to provide a method for manufacturing a semiconductor single crystal by the FZ method, which can reduce variation in resistivity.

  In order to achieve the above object, the present invention provides a method for producing a semiconductor single crystal by FZ method using gas doping in which at least a dopant gas is injected into a melting zone to dope a semiconductor crystal with a dopant to obtain a desired resistivity. At least when the semiconductor single crystal is manufactured in advance to obtain the in-plane resistivity distribution in the radial direction of the semiconductor single crystal, and the semiconductor single crystal to be a product is manufactured, The amount of dopant doped by the gas doping into the semiconductor single crystal is adjusted according to the previously obtained radial in-plane resistivity distribution, and the in-plane resistivity distribution in the radial direction of the semiconductor single crystal to be the product There is provided a method for producing a semiconductor single crystal characterized by controlling the above.

  As described above, the present invention is a method for manufacturing a semiconductor single crystal by FZ method using gas doping. First, a semiconductor single crystal is manufactured in advance, and an in-plane resistivity distribution in the radial direction is obtained. Then, during the production of the semiconductor single crystal to be the product, the amount of dopant doped by gas doping to the semiconductor single crystal to be the product is formed in the above-mentioned radial in-plane. It adjusts according to the resistivity distribution, and controls the in-plane resistivity distribution in the radial direction of the semiconductor single crystal as a product.

  Thus, if a semiconductor single crystal that is actually a product is manufactured, a semiconductor single crystal and a semiconductor wafer in which the in-plane resistivity distribution in the radial direction is controlled as desired can be obtained. For example, in-plane resistivity variation is reduced, and the in-plane resistivity distribution can be made more uniform than before. Furthermore, it is possible to improve the yield and productivity of elements manufactured from the wafer.

  At this time, for example, if the in-plane resistivity distribution in the radial direction is made more uniform, the previously obtained radial in-plane resistivity distribution has a low resistivity at the central portion of the semiconductor single crystal at the peripheral portion. In the case of a distribution having a downwardly convex shape with a high resistivity, the semiconductor single crystal that is the product is adjusted to decrease the doping amount of the dopant as the crystal grows, and the resistivity is increased. In the case of an upwardly convex distribution with a high resistivity at the center and a low resistivity at the periphery, the doping amount of the dopant is adjusted to increase as the semiconductor single crystal as the product grows. It is preferable to reduce the resistivity.

  In the crystal growth by the FZ method, the crystal growth interface, that is, the interface between the melt melt and the solidified crystal (solid-liquid interface) is convex downward, and the crystal center solidifies relatively late. By adjusting the doping amount of the dopant as described above according to the shape of the radial in-plane resistivity distribution, the radial in-plane resistivity distribution can be appropriately made uniform.

At this time, the diameter of the semiconductor single crystal to be the product can be 150 mm or more.
According to the method for producing a semiconductor single crystal of the present invention, the in-plane resistivity distribution of a crystal having a large diameter, which has been difficult in the past, can be further uniformized. The effect is more exhibited when the diameter of the FZ crystal to be produced is 150 mm or more, and more prominently when the diameter is 200 mm or more.

Moreover, the adjustment of the doping amount of the dopant to the semiconductor single crystal as the product can be performed by adjusting the injection amount and / or concentration of the dopant gas injected into the melting zone.
If it does in this way, the doping amount of the dopant to the semiconductor single crystal used as a product can be adjusted simply.

Further, it is preferable to adjust the doping amount of the dopant to the semiconductor single crystal to be the product so as to have a predetermined range of resistivity over the entire straight body portion.
If the doping amount of the dopant is adjusted in this way, the resistivity within a predetermined range can be obtained over the entire straight body part, and all of the straight body part can be effectively used, and the yield and production can be improved. Can be improved.

  As described above, according to the method for producing a semiconductor single crystal of the present invention, a semiconductor single crystal having a controlled radial in-plane resistivity distribution can be obtained. In particular, the in-plane resistivity distribution in the radial direction of a single crystal having a large diameter can be made uniform. This reduces the variation in resistivity in the radial plane of the wafer manufactured from the crystal, and further improves the yield and productivity when manufacturing elements from the wafer. As a result, the semiconductor single crystal Supply stability can also be improved.

It is the schematic which shows an example of the apparatus for manufacturing the semiconductor single crystal by FZ method. It is a schematic diagram which shows the growth state of the semiconductor single crystal by FZ method. (A) It is the schematic diagram of the crystal | crystallization cross section cut off in the surface which passes along the crystal center and is parallel to a crystal growth axis. FIG. 4B is a schematic view of a crystal cross section taken along a plane passing through the crystal center and perpendicular to the crystal growth axis. It is the flowchart which showed an example of the procedure of the manufacturing method of the semiconductor single crystal of this invention. It is a graph which shows the resistivity distribution acquired from the single crystal in a preliminary test. (A) It is a graph which shows the resistivity distribution along the crystal growth axis direction. (B) In-plane resistivity distribution in the radial direction at the start point (L1) of the straight body portion. (C) In-plane resistivity distribution in the radial direction at the midpoint (L2) of the straight body portion. (D) In-plane resistivity distribution in the radial direction at the end point (L3) of the straight body portion. It is a graph which shows the resistivity distribution acquired from the single crystal used as the product in this test. (A) It is a graph which shows the resistivity distribution along the crystal growth axis direction. (B) In-plane resistivity distribution in the radial direction at the start point (L1) of the straight body portion. (C) In-plane resistivity distribution in the radial direction at the midpoint (L2) of the straight body portion. (D) In-plane resistivity distribution in the radial direction at the end point (L3) of the straight body portion. It is a graph which shows the resistivity distribution acquired from the silicon single crystal in the preliminary test of an Example. (A) It is a graph which shows the resistivity distribution along the crystal growth axis direction. (B) In-plane resistivity distribution in the radial direction at a position of 0 mm in the straight body portion. (C) In-plane resistivity distribution in the radial direction at a position of 350 mm in the straight body portion. (D) In-plane resistivity distribution in the radial direction at a position of 700 mm in the straight body portion. It is a graph which shows the resistivity distribution acquired from the silicon single crystal in this test of an Example. (A) It is a graph which shows the resistivity distribution along the crystal growth axis direction. (B) In-plane resistivity distribution in the radial direction at a position of 0 mm in the straight body portion. (C) In-plane resistivity distribution in the radial direction at a position of 350 mm in the straight body portion. (D) In-plane resistivity distribution in the radial direction at a position of 700 mm in the straight body portion.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.
The present inventor has intensively investigated a method for producing an FZ single crystal in order to achieve a reduction in variation in the radial in-plane resistivity of the semiconductor single crystal (FZ single crystal) by the FZ method. Specifically, first, an FZ single crystal was manufactured, and the state of crystal growth in the crystal and further the resistivity distribution were investigated.
Hereinafter, a silicon single crystal will be described as an example.

  FIG. 1 shows an outline of an example of an apparatus for manufacturing a semiconductor single crystal by the FZ method. The FZ single crystal manufacturing apparatus 1 has a chamber 2, and an upper shaft 3 and a lower shaft 4 that can rotate are provided in the chamber 2. A silicon rod having a predetermined diameter is attached to the upper shaft 3 as a raw material rod 5, and a seed crystal 6 is attached to the lower shaft 4. In the chamber 2, a high-frequency coil 7 for melting the raw material rod 5 and a dope nozzle 9 for ejecting a dopant gas into the melting zone 8 where the raw material rod 5 is melted during gas doping are arranged. Yes.

  In order to manufacture an FZ single crystal using such an FZ single crystal manufacturing apparatus 1, the tip of the raw material rod 5 attached to the upper shaft 3 is melted by the high-frequency coil 7 and then the seed crystal 6 attached to the lower shaft 4. The silicon single crystal 11 is grown while moving the melting zone 8 relative to the raw material rod 5 while lowering the upper shaft 3 and the lower shaft 4 while rotating them. At this time, after squeezing, the diameter of the silicon single crystal 11 is gradually expanded to a desired diameter to form a cone portion 12, and after reaching the desired diameter, crystal growth is performed while maintaining the desired diameter, 13 is formed. During the growth, a dopant gas is injected from the dope nozzle 9 into the melting zone 8 to supply the dopant, thereby forming a silicon single crystal rod having a desired resistivity. The melting zone 8 is moved to the upper end of the raw material bar 5 to complete the production of the silicon single crystal 11.

The state of crystal growth in the crystal of the silicon single crystal 11 thus obtained was examined.
FIG. 2A is a schematic diagram of a crystal cross section showing a state of crystal growth taken along a plane passing through the crystal center and parallel to the crystal growth axis. The melt melt 14 in which the raw material rod 5 is melted is recrystallized to form the silicon single crystal 11, and a solid-liquid interface 15 exists at the boundary between the melt melt 14 and the silicon single crystal 11. As the silicon single crystal 11 grows, the solid-liquid interface 15 moves relatively upward.

  In the production of a silicon single crystal by the FZ method, the temperature gradient in the radial direction of the production single crystal is large, and the solid-liquid boundary surface 15 has a downwardly convex shape as shown in FIG. In the solid-liquid interface 15, the difference in position in the crystal growth axis direction between the periphery and the center of the crystal (solid-liquid interface depth 16) increases as the diameter of the silicon single crystal 11 to be manufactured increases.

In order to eliminate the quality difference due to the crystal part of the silicon single crystal 11 to be manufactured, the manufacturing conditions are usually set so as to keep the state during the single crystal manufacturing as constant as possible, and the shape of the solid-liquid interface greatly changes. It remains substantially constant without any change.
On the other hand, when manufacturing a wafer from the manufactured silicon single crystal rod, it is perpendicular to the crystal growth axis direction (that is, the crystal growth axis direction) (except for the case where it is desired to acquire a wafer having a specified direction and tilted angle from the crystal axis direction). (For example, see the dotted line P in FIG. 2A). For this reason, the surface of one wafer does not coincide with the solid-liquid interface at the time of crystal growth. That is, the positions are not generated simultaneously in the radial plane of the wafer, but the entire wafer is generated over a predetermined time (solid-liquid interface depth ÷ crystal growth rate).

  FIG. 2B shows a crystal cross section (radial cross section) at a certain position and at a certain point (portion indicated by a dotted line P in FIG. 2A) cut along a plane perpendicular to the crystal growth axis. Considering the generation history when viewed in the crystal cross section, as shown in the cross section of FIG. 2 (B), it gradually solidifies from the peripheral portion inward in a concentric shape, and finally the central portion solidifies. It should be a history. The same applies to the surface after the wafer has been subjected to a treatment such as polishing according to the product specifications after cutting.

By the way, it is considered that the in-plane resistivity distribution is determined by the following process.
1. While the FZ single crystal is produced, melt convection occurs in the melting zone, but the melt convection varies depending on the FZ production conditions.
2. Melt convection is not uniform throughout the melt, and there are differences depending on the position in the crystal diameter direction.
3. The dopant concentration in the melt is macroscopically uniform throughout the melt, but due to the difference in melt convection, the amount of dopant taken into the crystal from the solid-liquid interface also varies.
4). Even on the solid-liquid boundary surface, there is a difference in resistivity at each position in the radial direction, and a resistivity distribution (= solid-liquid boundary surface resistivity distribution) occurs.
5). Since the dopant is continuously supplied during the FZ single crystal production, the dopant concentration in the melt is kept constant, and the FZ production conditions are also kept, so that the melt convection is substantially unchanged. However, the resistivity distribution in the solid-liquid interface is not changed in the axial direction, and the resistivity at each position in the crystal diameter direction is little changed with time, and the crystal growth axis direction has almost the same radial distribution. To be kept.

  For this reason, as described above, even if the entire radial cross section of a portion in the crystal is not generated at the same time, even if there is a deviation in the generation timing depending on the position in the plane, The resistivity at the position is substantially uniform without variation in the crystal growth axis direction, and the in-plane resistivity distribution remains unchanged and remains the same.

Here, the present inventor has conceived to change the in-plane resistivity distribution by changing the amount of dopant supplied as the crystal grows.
Even if the amount of dopant supplied during crystal growth is changed, the distribution shape itself of the in-plane resistivity at the solid-liquid boundary during the production of the single crystal does not change because the melt convection is unchanged. However, since the change of the dopant concentration in the melt and the change of the resistivity occur, the resistivity along the growth axis direction at each position in the crystal diameter direction changes before and after the change of the supplied dopant amount. Since the crystal cross section perpendicular to the single crystal growth axis that becomes the later wafer surface is generated over a predetermined time rather than simultaneously, the amount of dopant supplied is changed during the generation (solidification) of a part of the cross section. When it is made, the resistivity of the part produced | generated after that in the said cross section changes according to the change of the dopant amount to supply. Therefore, the actually obtained resistivity distribution of the cross section changes from the in-plane resistivity distribution expected at the time when the already-generated part at the time of change of the supplied dopant amount is generated.

  Further, prior to manufacturing a single crystal that is actually a product using predetermined FZ single crystal manufacturing conditions, in-plane in the radial direction of the single crystal obtained using the predetermined FZ single crystal manufacturing conditions in advance. Obtain the resistivity distribution. Based on the distribution, if the amount of dopant supplied when actually producing a single crystal as a product is adjusted, the in-plane resistivity distribution can be effectively changed and controlled to a desired distribution. The inventor has found that this is possible, and has completed the present invention.

FIG. 3 shows an example of a specific procedure of the method for producing a semiconductor single crystal according to the present invention.
In addition, the kind of semiconductor single crystal to manufacture is not specifically limited, In addition to the silicon single crystal shown as an example below, a desired semiconductor single crystal can be manufactured suitably.
Also, the size of the crystal diameter is not particularly limited. In particular, when the diameter is 150 mm or more, further 200 mm or more, for example, it has been difficult to achieve uniform in-plane resistivity distribution in the radial direction in the past. However, in the present invention, uniform control is possible. Yes, the effect of the present invention can be exhibited more remarkably. As the diameter of the single crystal to be produced increases, the solid-liquid interface depth increases, and the necessity for reducing in-plane resistivity variation increases. Therefore, the application of the present invention is particularly effective when producing large-diameter crystals. .
Moreover, although the example manufactured using the FZ single crystal manufacturing apparatus 1 shown in FIG. 1 is demonstrated, it is not limited to this, It is possible to use a suitable FZ single crystal manufacturing apparatus each time.

(Preliminary test)
First, a silicon single crystal is manufactured (manufacturing a single crystal) under the same manufacturing conditions (except for gas doping conditions) as when manufacturing a silicon single crystal that is actually a product later.
In this way, in producing a silicon single crystal for preliminary testing, it is possible to perform a more effective preliminary test by using the same production conditions as those for producing a silicon single crystal as a product. In particular, the in-plane resistivity distribution in the radial direction of the silicon single crystal as a product can be controlled more precisely, which is preferable.

As described above, the silicon single crystal is manufactured by using the FZ single crystal manufacturing apparatus 1 and melting the tip of the raw material bar 5 (silicon polycrystalline bar) attached to the upper shaft 3 with the high-frequency coil 7. Fused to the seed crystal 6 attached to the shaft 4, dislocation-free by the throttle 10, lowered while rotating the upper shaft 3 and the lower shaft 4, and moved the melting zone 8 relative to the raw material rod 5 A silicon single crystal 11 is grown. At this time, after the drawing, the cone portion 12 is formed to a desired diameter, and the straight body portion 13 is further formed. The melting zone 8 is moved to the upper end of the raw material bar 5 to complete the production of the silicon single crystal 11.
During the growth, a dopant gas is injected from the dope nozzle 9 into the melting zone 8 to supply the dopant, thereby forming a silicon single crystal rod having a desired resistivity. Here, for simplicity, the injection amount and concentration of the dopant gas are constant, but are not particularly limited.

Next, the in-plane resistivity distribution in the radial direction is acquired for the manufactured silicon single crystal 11 (acquisition of the in-plane resistivity distribution in the radial direction of the manufactured single crystal).
As a method for obtaining the radial in-plane resistivity distribution, for example, a wafer is cut out from the straight body portion 13 of the silicon single crystal 11, and the in-plane resistivity distribution in the radial direction is obtained for each wafer. This corresponds to the in-plane resistivity distribution in the radial direction at the position where the wafer of the silicon single crystal 11 is cut out. If the information of the in-plane resistivity distribution in each wafer is accumulated, the in-plane resistivity distribution in the radial direction of the entire straight body portion 13 of the silicon single crystal 11 can be obtained. An existing method may be used as a method for measuring the resistivity.
At this time, the shape of the solid-liquid interface is also acquired. Depending on the shape of the solid-liquid boundary surface, for example, the central portion and the peripheral portion in the radial direction of the crystal can be compared to determine which is first solidified and recrystallized. However, as described above, in the production of a silicon single crystal by the FZ method, the solid-liquid interface generally has a downwardly convex shape.

  An example of the radial in-plane resistivity distribution thus obtained is shown in FIG. FIG. 4A is a resistivity distribution along the crystal growth axis direction (each average of radial in-plane resistivity distributions is shown along the crystal growth axis direction). (D) is an in-plane resistivity distribution in the radial direction at the start point (L1), the intermediate point (L2), and the end point (L3) of the straight body part 13, respectively.

  As shown in FIG. 4A, in this example, the average of the resistivity in each radial direction from the beginning to the end of the straight body portion 13 is substantially constant. That is, the doping amount of the dopant is almost constant from start to finish.

  In addition, as shown in FIGS. 4B to 4D, in this example, at the positions of L1, L2, and L3, the in-plane resistivity in the radial direction is low at the center of the crystal and at the periphery. Since it is higher, it has a downwardly convex shape. As described above, this is considered to be due to the difference in the dopant amount of the dopant taken into the crystal from the solid-liquid interface because of the melt convection that varies depending on the position in the radial direction.

(main exam)
Next, a silicon single crystal that is actually a product is manufactured (manufacture of a single crystal that is a product).
At this time, the doping amount of the dopant is adjusted by adjusting the gas doping conditions according to the in-plane resistivity distribution in the radial direction of the single crystal obtained in the preliminary test (see FIGS. 4B to 4D). To do. Thus, the in-plane resistivity distribution in the radial direction of the silicon single crystal to be the product is controlled as desired.

For example, if a silicon single crystal having a uniform in-plane resistivity distribution in the radial direction is manufactured in order to meet market demands, a downwardly convex distribution shape as shown in FIGS. The dopant doping amount is adjusted so as to narrow the vertical width.
Specifically, from the distribution of FIGS. 4B to 4D, since the resistivity is lower in the radial center that grows later, in this case, the doping amount of the dopant is reduced as the crystal grows. It is effective to manufacture a silicon single crystal as a product while increasing the resistivity in the crystal growth axis direction. That is, by increasing the resistivity at the time of generating the central portion rather than at the time of generating the peripheral portion that solidifies first, it is possible to reduce the variation in resistivity in the radial plane.

  The resistivity distribution along the crystal growth axis direction at this time (the average of the radial in-plane resistivity distributions shown along the crystal growth axis direction) is shown in FIG. The in-plane resistivity distributions in the radial direction at the start point (L1), the intermediate point (L2), and the end point (L3) are shown in FIGS.

  Contrary to FIGS. 4B to 4D, a silicon single crystal having a high resistivity in the central portion and a low resistivity in the peripheral portion and an upward convex radial in-plane resistivity distribution can be obtained. In the case of using the conditions, it is effective to increase the doping amount of the dopant as the crystal grows and manufacture a silicon single crystal as a product while decreasing the resistivity in the crystal growth axis direction.

  In adjusting the doping amount of the dopant by gas doping, for example, it can be performed by adjusting the injection amount and concentration of the dopant gas injected from the dope nozzle 9. These adjustment methods are preferable because the amount of dopant doped into the crystal can be easily adjusted. In addition, the method is not particularly limited as long as it can adjust the doping amount of the dopant appropriately, and can be used as appropriate.

  In addition, in adjusting the doping amount of the dopant according to the radial in-plane resistivity distribution obtained in advance, a change in the injection amount of the dopant gas is calculated using a computer or the like, and the gas doping conditions It is good to set and pattern. In this way, it is possible to adjust the doping amount so as to obtain a desired resistivity distribution more appropriately and simply.

  As described above, the change in the doping amount of the dopant that minimizes the variation in resistivity (upper and lower width of the resistivity distribution) in the radial direction of the silicon single crystal and the wafer cut out from the single crystal is obtained. Although it is possible to adjust, on the other hand, a change in resistivity in the direction of the crystal growth axis is unavoidable (see FIG. 5A).

For this reason, in crystal production, in addition to the degree of variation in in-plane resistivity, crystal growth can be achieved by adjusting the dopant doping amount in consideration of the desired resistivity range, straight body length, etc. It is preferable to adjust the degree of change in resistivity in the axial direction.
In particular, if the resistivity is adjusted so that the resistivity can fall within a predetermined range (for example, within the standard) over the entire straight body portion 13 (see FIG. 5A), all of the straight body portions are adjusted. It is possible to obtain a silicon single crystal that can be effectively used, has an excellent in-plane resistivity distribution in the radial direction, and can manufacture elements with high yield and productivity.

  By the present invention as described above, the in-plane resistivity distribution in the radial direction can be controlled as desired, and the semiconductor single crystal is more suitable for the purpose (particularly, the uniformity of the in-plane resistivity distribution in the radial direction). It is possible to obtain As a result, the yield and productivity of device manufacture can be increased.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.
(Example)
An FZ silicon single crystal is manufactured using the method for manufacturing a semiconductor single crystal of the present invention. A silicon single crystal having a crystal diameter of 150 mm, a straight body length of 700 mm, a conductivity type N type, and a target resistivity range of 45 to 75 Ωcm (target center value of 60 Ωcm) is manufactured.

First, as a preliminary test, the gas doping conditions were adjusted so that the resistivity of the silicon single crystal to be produced was constant in the crystal growth axis direction. And the resistivity distribution of the obtained single crystal was investigated. In addition, the solid-liquid interface shape was convex downward.
FIG. 6A shows a resistivity distribution along the crystal growth axis direction of the silicon single crystal at this time (each average of radial in-plane resistivity distributions is shown along the crystal growth axis direction). 6B to 6D show the in-plane resistivity distribution in the radial direction of the wafer cut out from the single crystal at this time. FIG. 6B shows the wafer cut out from the position of 0 mm, which is the starting point of the single crystal straight body, FIG. 6C shows the position of 350 mm, and FIG. The in-plane resistivity distribution in the radial direction is shown.

As shown in FIGS. 6 (B) to 6 (D), the in-plane resistivity distribution in the radial direction at this time has a low resistivity at the center of the single crystal (wafer) throughout the manufactured single crystal and the resistance at the peripheral portion. It became a mortar-like distribution shape with a high rate and a downward convexity.
Here, RRG = ((maximum resistivity in the wafer plane−minimum resistivity in the wafer plane) / (minimum resistivity in the wafer plane)) × 100
In this case, the RRG value in this case was 10.5% at the position of 0 mm, 11.8% at the position of 350 mm, and 12.3% at the position of 700 mm. Moreover, in the entire single crystal straight body, the lowest RRG value was 10.5%. The larger the value of RRG, the greater the variation in resistivity in the radial plane.

  Therefore, based on the distribution of resistivity shown in FIG. 6, the product of this test to be performed next is obtained so that the variation in resistivity in the radial plane is reduced as compared with the single crystal manufactured for the preliminary test. In the production of a single crystal, the doping amount of the dopant was actually adjusted by changing the gas doping conditions in the crystal growth axis direction. That is, the in-plane resistivity distribution in the radial direction of the silicon single crystal to be manufactured next was controlled to be more uniform.

More specifically, the radial radial in-plane resistivity distribution (see FIGS. 6B to 6D) has a low convexity at the center and a low resistivity at the periphery. Therefore, the injection amount of the dopant gas was reduced as the crystal was grown, and the doping amount of the dopant was adjusted to be reduced. Further, in consideration of the target resistivity range of 45 to 75 Ωcm, the doping amount of the dopant was adjusted so that the entire straight body of the crystal was within the range.
The production conditions were the same as in the preliminary test except for the gas doping conditions.
Under the conditions as described above, a silicon single crystal as a product was manufactured, and the resistivity distribution was investigated.

FIG. 7A shows the resistivity distribution along the crystal growth axis direction of the silicon single crystal at this time (each average of the radial in-plane resistivity distributions shown along the crystal growth axis direction). 7B to 7D show the in-plane resistivity distribution in the radial direction of the wafer cut out from the single crystal at this time. 7B shows the wafer cut out from the position of 0 mm, which is the starting point of the single crystal straight body, FIG. 7C shows the position of 350 mm, and FIG. 7D shows the wafer cut out from the position of 700 mm, which is the end point. The in-plane resistivity distribution in the radial direction is shown.
Table 1 shows the rate of increase in resistivity in the crystal growth axis direction.

First, as shown in FIGS. 7B to 7D, the in-plane resistivity distribution in the radial direction of the obtained wafer is still lower than the resistivity in the central portion, which is lower than the resistivity in the peripheral portion. Although it is a distribution shape, as compared with the distribution shape of the resistivity in the preliminary test shown in FIGS. 6B to 6D, the variation in the resistivity is remarkably reduced, and the in-plane resistance in the radial direction is the target. It can be seen that the shape of the rate distribution could be made more uniform. When the RRG value is calculated, the rate of increase in resistivity in the crystal growth axis direction is 4.7% at the position of 0 mm of the single crystal straight body, and the rate of increase in resistivity in the crystal growth axis direction is 350 mm and 700 mm. The position was 6.0% and 5.5%, respectively. Therefore, regarding the change in the RRG value of the single crystal in the preliminary test and the single crystal in the main test, the position of -5.8% (4.7% -10.5%) at the position of 0 mm from the single crystal straight body portion, the position of 350 mm -5.8% (6.0% -11.8%) at the position of 700 mm and -6.8% (5.5% -12.3%) at the position of 700 mm, all of which could be reduced.
As a whole, there was a tendency that the degree of decrease in the RRG value increased as the resistivity increase rate in the crystal growth axis direction increased.

Further, in the whole single crystal straight body part in this test, the maximum value of the RRG value was 6.0%. That is, it was possible to make it smaller than the value at the preliminary test (minimum value of 10.5%) over the entire straight body portion, and to reduce the variation of the resistivity in the radial direction over the entire straight body portion. .
Furthermore, the entire straight body was able to be within a target resistivity range of 45 to 75 Ωcm.

  That is, the in-plane resistivity distribution in the radial direction is more uniform, the quality is superior, and the entire straight body portion is within the desired resistivity range, and all usable silicon single crystals are obtained. I was able to get it.

(Comparative example)
An FZ silicon single crystal is manufactured using a conventional method for manufacturing a semiconductor single crystal. A silicon single crystal having a crystal diameter of 150 mm, a crystal length of 700 mm, a conductivity type N type, and a target resistivity range of 45 to 75 Ωcm (target center value of 60 Ωcm) is manufactured.

A silicon single crystal was produced under the same production conditions as in the preliminary test of the example. And the resistivity distribution of the obtained single crystal was investigated. In addition, the solid-liquid interface shape was convex downward.
As a result, the same results as in FIG. 6 were obtained. The RRG value was similar.

  As described above, in the comparative example according to the conventional method, although the entire straight body portion is within the target resistivity range (see FIG. 6A), the in-plane resistivity distribution in the radial direction at each position in the crystal growth axis direction. , The resistivity variation is relatively large (see FIGS. 6B to 6D). On the other hand, if the manufacturing method of the present invention is used, the distribution of the in-plane resistivity in the radial direction can be controlled as desired as in the embodiment, and in particular, it can be made uniform. In addition, the variation in the in-plane resistivity at each position in the crystal growth axis direction can be significantly reduced as compared with the comparative example (see FIG. 7). Moreover, at the same time, the entire straight body portion can be aimed and kept within the resistivity range.

  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 ... FZ single crystal manufacturing apparatus, 2 ... Chamber, 3 ... Upper axis, 4 ... Lower axis,
5 ... Raw material rod, 6 ... Seed crystal, 7 ... High frequency coil, 8 ... Melting zone,
9 ... Dope nozzle, 10 ... Aperture, 11 ... Silicon single crystal,
12 ... cone part, 13 ... straight body part, 14 ... melt melt,
15 ... solid-liquid interface, 16 ... solid-liquid interface depth.

Claims (5)

In a method for producing a semiconductor single crystal by FZ method using gas doping in which at least a dopant gas is injected into a melting zone to dope a semiconductor crystal with a dopant to obtain a desired resistivity,
At least when the semiconductor single crystal is manufactured in advance and the in-plane resistivity distribution in the radial direction of the semiconductor single crystal is obtained, and the semiconductor single crystal to be a product is manufactured, The doping amount of the dopant by the gas doping to the semiconductor single crystal is adjusted according to the previously acquired radial in-plane resistivity distribution, and the in-plane resistivity distribution in the radial direction of the semiconductor single crystal to be a product is adjusted. A method for producing a semiconductor single crystal, comprising controlling the semiconductor single crystal. The previously obtained radial in-plane resistivity distribution is
In the case of a downwardly convex distribution with a low resistivity in the central portion of the semiconductor single crystal and a high resistivity in the peripheral portion, the dopant doping amount is reduced as the product semiconductor single crystal grows. To increase the resistivity,
In the case of an upward convex distribution with a high resistivity at the center of the semiconductor single crystal and a low resistivity at the periphery, the dopant doping amount is increased as the semiconductor single crystal as the product grows. The method of manufacturing a semiconductor single crystal according to claim 1, wherein the resistivity is reduced by adjusting the resistance in such a manner.   3. The method for producing a semiconductor single crystal according to claim 1, wherein a diameter of the semiconductor single crystal to be the product is 150 mm or more.   The amount of dopant doped into the semiconductor single crystal as the product is adjusted by adjusting the injection amount and / or concentration of the dopant gas injected into the melting zone. The manufacturing method of the semiconductor single crystal as described in any one.   5. The method according to claim 1, wherein the doping amount of the dopant to the semiconductor single crystal to be the product is further adjusted so as to have a resistivity within a predetermined range over the entire straight body portion. A method for producing a semiconductor single crystal according to one item.

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