JP6720841B2 - Method for manufacturing semiconductor silicon single crystal - Google Patents

Description

The present invention relates to a method for producing a semiconductor silicon single crystal (hereinafter, also referred to as FZ silicon single crystal) by the FZ method (floating zone method or floating zone melting method).

The FZ method is used, for example, as one of the methods for producing a semiconductor single crystal such as a silicon single crystal which is most often used as a semiconductor element at present.

FIG. 9 is a schematic view illustrating an example of each manufacturing step in the method for manufacturing an FZ silicon single crystal by the FZ method. As shown in FIG. 9, the lower end portion of the semiconductor rod (raw material rod) 104 as a raw material is melted and fused to the seed crystal 105 ((a) seeding step), and further produced in this seeding. Drawing (necking step) to remove the dislocations ((b) necking step), and thereafter, the crystallization side semiconductor rod (semiconductor single crystal rod) 109 is grown while expanding it to a desired diameter ((c) cone portion). Forming process). Further, the crystallization side semiconductor rod 109 is grown while controlling it to have a desired diameter ((d) straight body portion forming step), the supply of the raw material is stopped, and the diameter of the crystallization side semiconductor rod 109 is reduced to reduce the crystal. The outgoing semiconductor rod 109 is separated from the raw semiconductor rod 104 ((e) separating step). A semiconductor crystal (FZ silicon single crystal) can be manufactured through the above steps.

Normally, N-type or P-type impurity doping is required to give a desired electrical resistivity to a semiconductor silicon single crystal. In the FZ method, a gas doping method is known in which a dopant gas is blown to the melting zone (see Non-Patent Document 1).

As a dopant gas, for example, PH ₃ or the like is used for doping P (phosphorus) that is an N-type dopant, and B ₂ H ₆ or the like is used for doping B (boron) that is a P-type dopant. The electrical resistivity of a silicon single crystal changes depending on the difference in the concentration of these N-type dopant and P-type dopant in the crystal. However, in the case of doping only an N-type dopant or only a P-type dopant in ordinary crystal production, The electrical resistivity becomes lower as the amount of dopant added increases.

In order to obtain a semiconductor silicon single crystal having a desired electric resistivity, the dopant addition amount calculated based on the electric resistivity of the raw material and the desired electric resistivity needs to be appropriately maintained. A semiconductor silicon single crystal having a desired electrical resistivity can be obtained by growing a single crystal by the FZ method while adjusting the concentration and the flow rate of the supplied dopant gas while appropriately maintaining the dopant addition amount. ..

In the FZ method, the silicon melt is in the floating zone and is produced without contact with any other member other than the atmosphere in the furnace. Therefore, the impurity concentration of the semiconductor silicon single crystal produced by the FZ method is extremely low and high. It is characterized by its purity.

For example, in the CZ method (Czochralski method) for producing a semiconductor silicon single crystal using a quartz crucible, SiO is generated by the reaction between a silicon melt and SiO _{2 in the} crucible, and oxygen is dissolved in the silicon melt. Oxygen is mixed into the manufactured CZ silicon single crystal to have a high oxygen concentration, whereas the semiconductor silicon single crystal produced by the FZ method has an extremely low oxygen concentration. Even in the case of the FZ method using a CZ silicon crystal rod having a higher oxygen concentration than a high-purity polysilicon rod as a raw material, the oxygen concentration is usually required to be as low as possible.

On the other hand, in order to impart the same intrinsic gettering effect or slip resistance as the silicon wafer by the CZ method to the silicon wafer by the FZ method, the silicon melt is made of high-purity quartz during the production of the semiconductor silicon single crystal by the FZ method. A method for obtaining a semiconductor silicon single crystal by the FZ method, which has an oxygen concentration similar to that of the semiconductor silicon single crystal by the CZ method, by contacting or inserting a different oxygen supply material and doping the silicon melt with oxygen (for example, Patent Document 1). 2, 3) or a method of increasing the mechanical strength by making the oxygen concentration in the peripheral portion of the FZ silicon single crystal to be the same as that of the CZ silicon single crystal (for example, Patent Document 4).

Further, Patent Document 5 discloses a method of increasing the oxygen partial pressure of the atmosphere in the furnace to change the temperature fluctuation of the melt to make the oxygen concentration variation uniform. Further, Patent Document 6 discloses a method in which a raw material containing a large amount of impurities, for example, oxygen is prepared, growth conditions are determined such that the obtained FZ silicon single crystal has a desired oxygen concentration, and the introduction amount is controlled. ..

JP-A-59-102891 JP-A-02-197118 Japanese Patent No. 2807688 Japanese Patent Laid-Open No. 07-291783 JP, 2000-335995, A JP, 2005-160800, A

WOLFGANG KELLER, ALFRED MUHLBAUER, "Floating-Zone Silicon" p. 82-92, MARCEL DEKKER, INC. Issue

In recent years, power devices have been in the spotlight from the viewpoint of energy saving, but thyristors, diodes, IGBTs (Insulated Gate Bipolar Transistors), etc. are used to introduce lattice defects by He irradiation or electron beam irradiation to control carrier lifetime. There are devices that use technology. In a semiconductor wafer used for manufacturing such a device, it is possible to relatively easily control to a desired lattice defect amount by increasing the oxygen concentration to some extent.

A semiconductor silicon single crystal by the FZ method, which is a raw material of a silicon wafer used for such a switching device, is manufactured by using a high-purity polysilicon rod or a CZ silicon crystal rod manufactured by the CZ method as a raw material. The oxygen concentration of these semiconductor silicon single crystals was smaller than 5.6×10 ¹⁵ atoms/cm ³ when a high-purity polysilicon rod was used as the raw material, and 1.4 when the CZ silicon crystal was used as the raw material. All of them are at a low level of ×10 ¹⁶ atoms/cm ^{3 to} 1.9×10 ¹⁶ atoms/cm ³ . On the other hand, in the case of the semiconductor silicon single crystal by the CZ method, the oxygen concentration is as high as 1.6×10 ¹⁷ atoms/cm ³ or more. In order to further improve the device characteristics, it is desirable that the oxygen concentration of the silicon wafer, which is a material, be kept within a certain narrow range at a level between the semiconductor silicon single crystal by the FZ method and the semiconductor silicon single crystal by the CZ method. Substantially, the oxygen concentration of the semiconductor silicon single crystal by the FZ method needs to be higher than the conventional level described above.

Further, regarding the increase of the oxygen concentration of the semiconductor silicon single crystal by the FZ method, although it is manufactured for the purpose of increasing the oxygen concentration to the same level as that of the CZ silicon single crystal, the purpose is to keep the oxygen concentration within a predetermined range. It was never manufactured in.

Therefore, when an attempt is made to produce a semiconductor silicon single crystal by the FZ method, which has a desired oxygen concentration, all the methods of the prior art documents use some form of external oxygen in the FZ for a semiconductor silicon single crystal having a low oxygen concentration. Is added. In this case, the concentration of oxygen in the semiconductor silicon single crystal is as high as that of CZ silicon single crystal. Furthermore, in the recent large-diameter semiconductor silicon single crystal production (for example, 200 mm) by the FZ method, when such a method is applied, it becomes difficult to obtain the semiconductor silicon single crystal itself. It is certain that problems such as deterioration of resistivity distribution) will occur, and it is desired to manufacture a semiconductor silicon single crystal by the FZ method of desired quality by a simple and reliable method capable of obtaining a crystal.

Here, the semiconductor silicon single crystal has an oxygen concentration which is not completely uniform but has a distribution in a cross section perpendicular to the growth direction, that is, in the wafer surface. Further, even in the CZ silicon crystal as a raw material, the oxygen concentration is not uniform throughout the crystal, and an oxygen concentration distribution occurs in the growth direction. Therefore, it is necessary to consider the oxygen concentration distribution in the cross section and in the growth direction in order to keep the whole semiconductor silicon single crystal to be produced within the desired oxygen concentration range, and especially the required oxygen concentration range is small. In such a case, there is a high possibility that a quality non-conforming part will occur, so that some ingenuity is required.

In addition, the required oxygen concentration range is wide enough to allow some fluctuation, and even if there are no quality-incompatible parts, if there is a difference in oxygen concentration level due to each part in the same crystal, thermal This may lead to quality differences such as changes in the degree of donor generation, which may affect the yield during semiconductor device manufacturing.

The present invention has been made in view of the above problems, and in the production of a semiconductor silicon single crystal by the FZ method, a semiconductor silicon single crystal having an oxygen concentration within a desired range in the entire semiconductor silicon single crystal to be produced is provided. An object is to provide a method for producing crystals.

In order to achieve the above object, according to the present invention, in a method for producing a semiconductor silicon single crystal by the FZ method using a CZ silicon crystal produced by the CZ method as a raw material,
Preliminarily measuring the oxygen concentration in the axial direction of the CZ silicon crystal to obtain an oxygen concentration distribution,
Processing the shape of the CZ silicon crystal according to the obtained oxygen concentration distribution in the axial direction of the CZ silicon crystal;
And a step of producing the semiconductor silicon single crystal by the FZ method, using the CZ silicon crystal having the shape processed as a raw material, the method for producing the semiconductor silicon single crystal by the FZ method.

Thus, after the shape of the CZ silicon crystal is processed according to the oxygen concentration distribution in the axial direction of the CZ silicon crystal acquired in advance, the CZ silicon crystal processed in this shape is used as a raw material and the semiconductor is processed by the FZ method. By producing a silicon single crystal, it is possible to control the oxygen concentration of the produced FZ semiconductor silicon single crystal so that it falls within a desired range.

At this time, in the step of processing the shape of the CZ silicon crystal,
It is preferable that the diameter of the CZ silicon crystal is changed in the axial direction so as to correlate with the obtained oxygen concentration distribution of the CZ silicon crystal in the axial direction.

By doing so, it is possible to effectively control the oxygen concentration within the desired range in the entire semiconductor silicon single crystal to be manufactured.

At this time, in the step of processing the shape of the CZ silicon crystal,
In the axial oxygen concentration distribution of the obtained CZ silicon crystal, the diameter of the CZ silicon crystal at the low oxygen concentration position is smaller than the diameter of the CZ silicon crystal at the high oxygen concentration position. It is preferably processed.

In this way, by performing processing such that the raw material diameter is changed so as to cancel out the oxygen concentration in the obtained oxygen concentration distribution in the axial direction of the CZ silicon crystal according to the magnitude of the oxygen concentration, the FZ is manufactured. It is possible to make the oxygen concentration of the semiconductor silicon single crystal closer to a uniform value in the growth direction by the method, and more reliably control the oxygen concentration in the desired range over the entire crystal.

At this time, the diameter of the semiconductor silicon single crystal produced by the FZ method is preferably 150 mm or more.

Even in the production of such a large diameter single crystal, the present invention makes it possible to reliably obtain the single crystal.

At this time, it is preferable to use, as a raw material, the CZ silicon crystal having an oxygen concentration of 50 times or more the desired oxygen concentration of the semiconductor silicon single crystal produced by the FZ method.

By doing so, it is possible to obtain a semiconductor silicon crystal having a desired oxygen concentration range under the manufacturing conditions for obtaining a high-quality FZ single crystal, and it is necessary to significantly change the manufacturing conditions of the FZ method. Is not provided.

At this time, the oxygen concentration of the entire semiconductor silicon single crystal produced by the FZ method in the axial direction is 2.1×10 ¹⁶ atoms/cm ³ or more and 8.0×10 ¹⁶ atoms/cm ³ or less, and more preferably It is preferably in the range of 4.0×10 ¹⁶ atoms/cm ³ or more and 5.0×10 ¹⁶ atoms/cm ³ or less. The oxygen concentration used in the present invention is based on ASTM'79.

With this configuration, the oxygen concentration in the entire axial direction of the semiconductor silicon single crystal produced by the FZ method is higher than that of the semiconductor silicon single crystal produced by the conventional FZ method, and the semiconductor silicon single crystal is within a predetermined narrow range. Crystals can be produced.

According to the method for producing a semiconductor silicon single crystal of the present invention, the shape of the CZ silicon crystal is processed according to the oxygen concentration distribution in the axial direction of the CZ silicon crystal acquired in advance, and then the CZ silicon processed by this shape is processed. By using a crystal as a raw material and manufacturing a semiconductor silicon single crystal by the FZ method, it is possible to control the oxygen concentration of the entire manufactured semiconductor silicon single crystal to fall within a desired range. As a result, the quality required for manufacturing the device can be satisfied in the entire semiconductor silicon single crystal, and the quality and productivity of the crystal are improved, and the crystal is stable, so that a stable product supply can be achieved.

FIG. 3 is a process chart showing an example of a method for producing a semiconductor silicon single crystal of the present invention. It is a schematic diagram showing a manufacturing device of a semiconductor single crystal used for a manufacturing method of a semiconductor silicon single crystal of the present invention. It is a graph which shows an example of oxygen concentration distribution in the cross section of semiconductor silicon single crystal. It is a graph which shows an example of the oxygen concentration distribution of the CZ silicon raw material crystal in the axial direction. 6 is a graph showing a relationship between an impurity introduction rate (oxygen concentration in FZ crystal/oxygen concentration in raw material) and a numerical value K. It is the graph which showed the diameter of the CZ silicon raw material crystal processed in the Example. It is the graph which showed the oxygen concentration distribution of the axial direction of the FZ silicon single crystal manufactured in the Example. It is the graph which showed the oxygen concentration distribution of the axial direction of the FZ silicon single crystal manufactured in the comparative example. It is a schematic diagram explaining an example of each manufacturing process in a manufacturing method of a semiconductor single crystal by the FZ method.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.

As described above, it is desirable that the quality conventionally required for the semiconductor silicon single crystal by the FZ method is high purification, that is, the impurity concentration is as low as possible, which is one of the characteristics of the semiconductor silicon single crystal by the FZ method. It was also.

However, depending on the method of manufacturing a device manufactured from a semiconductor silicon wafer by the FZ method, it may be preferable that a certain amount of impurities such as oxygen be contained in the semiconductor silicon single crystal in a certain amount. We conducted a thorough study to deal with such problems. As a result, the CZ silicon crystal shape is processed in accordance with the axial oxygen concentration distribution of the CZ silicon crystal acquired in advance, and the CZ silicon crystal processed in this shape is used as a raw material. It has been found that by producing a single crystal, the oxygen concentration of the entire semiconductor silicon single crystal produced can be controlled so as to fall within a desired range. Then, the best mode for carrying out these was scrutinized to complete the present invention.

First, an example of a semiconductor silicon single crystal production apparatus capable of producing a semiconductor silicon single crystal of the present invention will be described with reference to FIG.

As shown in FIG. 2, an upper shaft 12 and a lower shaft 13 are provided in the chamber 11 of the semiconductor silicon single crystal manufacturing apparatus 10. A CZ silicon crystal 14 having a predetermined diameter is attached to the upper shaft 12 as a raw material semiconductor rod (CZ silicon crystal 14), and a seed crystal 15 is attached to the lower shaft 13.

Further, the high frequency heating coil 16 for melting the CZ silicon crystal 14 is provided, and the crystallized semiconductor rod (semiconductor silicon single crystal 19) can be grown while moving the melting zone 18 relative to the CZ silicon crystal 14. .. Further, the dopant gas can be supplied from the dope nozzle 20 (dopant gas supply means) during the growth.

Next, a method for manufacturing a semiconductor silicon single crystal of the present invention will be described with reference to FIG. Hereinafter, a case where the semiconductor silicon single crystal manufacturing apparatus of FIG. 2 described above is used will be described.

First, a CZ silicon single crystal manufactured by the CZ method is prepared as a raw material. Then, a step of measuring the oxygen concentration in the axial direction of the CZ silicon crystal in advance and acquiring the oxygen concentration distribution is performed (SP1 in FIG. 1).

Here, it is preferable to use, as a raw material, a CZ silicon crystal having an oxygen concentration of 50 times or more the oxygen concentration of a desired semiconductor silicon single crystal produced by the FZ method. By doing so, even if oxygen is scattered into FZ and becomes low oxygen, a semiconductor silicon crystal having a desired oxygen concentration range can be obtained under the manufacturing conditions for obtaining a high-quality FZ single crystal. It can be obtained, and there is no restriction that drastically changes the manufacturing conditions.

At this time, the desired oxygen concentration is 2.1×10 ¹⁶ atoms/cm ³ or more and 8.0×10 ¹⁶ atoms/cm ³ or more in the entire axial direction of the semiconductor silicon single crystal produced by the FZ method. cm ³ or less, more preferably 4.0×10 ¹⁶ atoms/cm ³ or more and 5.0×10 ¹⁶ atoms/cm ³ or less. The oxygen concentration used in the present invention is based on ASTM'79.

Thus, the semiconductor silicon single crystal produced by the FZ method has a higher oxygen concentration in the entire axial direction than that of the conventional semiconductor silicon single crystal by the FZ method, and the semiconductor silicon single crystal is contained within a predetermined narrow range. It can be manufactured.

Next, a step of processing the shape of the CZ silicon crystal is performed according to the obtained oxygen concentration distribution of the CZ silicon crystal in the axial direction (SP2 in FIG. 1).

Here, it is preferable to perform processing so that the diameter of the CZ silicon crystal is changed in the axial direction so as to correlate with the obtained oxygen concentration distribution of the CZ silicon crystal in the axial direction. By doing so, it is possible to effectively control the oxygen concentration in the entire FZ semiconductor silicon single crystal to be manufactured so as to fall within a desired range.

It will be described below that the oxygen concentration distribution in the axial direction of the semiconductor silicon single crystal produced by the FZ method can be improved by adjusting the diameter of the raw material crystal (CZ silicon crystal).

Regarding the oxygen introduced into the semiconductor silicon single crystal produced by the FZ method, the oxygen contained in the CZ raw material is supplied to the melt (melting zone 18 in FIG. 2), and the amount removed from the melt is the FZ single crystal. It is thought that the oxygen amount actually introduced into the single crystal determines the oxygen concentration in the melt at that time, particularly the oxygen concentration near the solidification interface. Since oxygen in the melt evaporates from the melt surface in contact with the atmosphere in the furnace, the oxygen concentration in the melt becomes low near the melt surface. Therefore, the oxygen concentration distribution in the melt in the vicinity of the solidification interface in the crystal diameter direction is low on the crystal outer peripheral side close to the melt surface and high in the crystal center. Therefore, the oxygen concentration in the cross-sectional direction of the manufactured semiconductor silicon single crystal is not uniform and has the same tendency as the oxygen concentration distribution in the melt. FIG. 3 shows an example of the oxygen concentration distribution in the cross section of the semiconductor silicon single crystal.

Furthermore, since the oxygen supplied to the melt is the oxygen contained in the CZ raw material, the amount of oxygen supplied changes depending on the oxygen concentration of the raw material melted at each time point during the semiconductor silicon single crystal growth by the FZ method. That is, the change in oxygen concentration in the longitudinal direction (axial direction) of the CZ silicon crystal used as a raw material affects the change in oxygen concentration in the growth direction (axial direction) of the semiconductor silicon single crystal produced by the FZ method.

As described above, when considering the entire semiconductor silicon single crystal to be manufactured, it is difficult to say that the oxygen concentration is completely uniform in any part of the crystal. Will have a range. For this reason, when the entire crystal is kept in a desired oxygen concentration range, it is necessary to reduce the change in oxygen concentration in the cross section and/or the change in oxygen concentration in the crystal growth direction.

However, it is difficult to make the oxygen concentration change in the cross section of the semiconductor silicon single crystal uniform due to its growth principle, and it is inevitable that the crystal has the oxygen concentration distribution in the cross section. Therefore, it is necessary to suppress the fluctuation of oxygen concentration in the crystal growth direction, but one method for achieving this is to suppress the fluctuation of oxygen concentration in the longitudinal direction of the raw material. However, particularly when obtaining a semiconductor silicon single crystal having an oxygen concentration higher than the conventional level, it is necessary to increase the oxygen concentration of the CZ silicon crystal as a raw material. In such a case, the longitudinal length of the CZ silicon crystal is increased. It is also difficult to suppress the change in oxygen concentration in the direction.

Therefore, assuming that the change in the oxygen concentration in the longitudinal direction of the CZ silicon crystal as the raw material is unavoidable, the diameter of the raw material is adjusted according to the change in the oxygen concentration in the raw material to grow a semiconductor silicon single crystal using the raw material. Thus, the oxygen concentration of the semiconductor silicon single crystal obtained by the FZ method can be kept within a desired range in the entire axial direction.

Therefore, as described above, the oxygen concentration of the CZ silicon crystal that is the raw material is measured in advance (SP1), and the change in the longitudinal direction is confirmed. FIG. 4 shows an example of the oxygen concentration distribution in the longitudinal direction of the raw material. For example, when a raw material having an oxygen concentration distribution as shown in FIG. 4 is used, the amount of oxygen supplied to the melt decreases as the semiconductor silicon single crystal grows. Higher at the beginning of growth and lower at the end of growth. That is, the oxygen concentration distribution in the growth direction of the semiconductor silicon single crystal has the same tendency as the oxygen concentration distribution in the longitudinal direction of the CZ raw material.

Here, the amount of oxygen actually introduced into the semiconductor silicon single crystal is less than the amount of oxygen supplied to the melt because most of it is removed by evaporation.

The amount of oxygen evaporated from the melt during the growth of the semiconductor silicon single crystal is proportional to the melt residence time and the melt surface area, and has a contradictory relationship with the furnace pressure. Therefore, the oxygen introduction rate with the raw material oxygen concentration as the denominator and the FZ silicon single crystal oxygen concentration as the numerator is determined by the numerical value K represented by (melt retention time)×(melt surface area)/(furnace pressure).

Here, the element of the melt residence time is related to the amount of melted melt in a straight body and the amount of melted raw material within a crystal unit time (crystal growth amount), that is, the crystal growth rate, but strictly speaking, the raw material diameter is constant. This is true under the condition that the raw material supply rate is constant, and when the raw material diameter changes, the change in the evaporation amount of oxygen until the raw material melts and falls into the melt staying on the growing single crystal. It is thought to exist.

That is, it is considered that the parameter of the raw material supply rate influences the oxygen concentration, and from the relationship of the crystal growth amount per unit time, the raw material calculated as ((crystal diameter)/(raw material diameter)) ² ×(crystal growth rate) The oxygen introduction rate can be changed by controlling the supply rate.

FIG. 5 shows the relationship between the numerical value K in the production of a semiconductor silicon single crystal and the oxygen concentration ratio between the raw material crystal and the semiconductor silicon single crystal. The melt residence time was calculated from the amount of melted melt in a straight body and the amount of melted raw material (crystal growth amount) within a crystal unit time, and the melt surface area was approximately used as the cross-sectional area of the produced crystal.

The oxygen concentration change range in the growth direction of the semiconductor silicon single crystal to be acquired can be estimated by the change in the source oxygen concentration measured in advance, that is, the change in the supply oxygen concentration at each time point of the FZ crystal growth and the numerical value K.

At this time, in order to suppress the change in oxygen concentration in the crystal growth direction, the diameter of the CZ silicon crystal of the raw material is changed in the longitudinal direction (axial direction). Perform an offsetting operation.

That is, the CZ silicon crystal is processed in advance in such a manner that the raw material diameter is changed in the longitudinal direction in a manner that correlates with an increase or decrease in the oxygen concentration in the axial direction of the CZ silicon crystal, and then used for manufacturing a semiconductor silicon single crystal by the FZ method. As a result, the variation in oxygen concentration in the growth direction of the semiconductor silicon single crystal manufactured by the FZ method can be reduced, and the variation in oxygen concentration in the entire crystal can be suppressed to the range of variation in oxygen concentration in the cross section.

Specifically, in the obtained oxygen concentration distribution in the axial direction of the CZ silicon crystal, the diameter of the CZ silicon crystal at the low oxygen concentration position is made smaller than the diameter of the CZ silicon crystal at the high oxygen concentration position. It is preferably processed. In this way, according to the oxygen concentration distribution in the axial direction of the obtained CZ silicon crystal, the diameter of the raw material is changed so as to cancel it according to the magnitude of the oxygen concentration, and then the crystal is manufactured by the FZ method. As a result, the oxygen concentration of the semiconductor silicon single crystal obtained by the FZ method can be made closer to uniform in the growth direction, and it can be more surely controlled within the desired oxygen concentration range in the entire crystal. In this case, the diameter of the CZ silicon crystal can be easily processed by grinding the outer circumference. After processing, it can be used as a raw material for the FZ method by performing etching or cleaning.

Then, a step of manufacturing a semiconductor silicon single crystal by the FZ method is performed using the CZ silicon crystal whose shape is processed as described above as a raw material (SP3 in FIG. 1).

At this time, the diameter of the semiconductor silicon single crystal produced by the FZ method is preferably 150 mm or more. According to the present invention, it is possible to reliably obtain a single crystal having a desired oxygen concentration range even in the production of such a large diameter crystal.

First, as the raw material semiconductor rod, the CZ silicon crystal 14 whose oxygen concentration in the axial direction has been measured in advance and whose shape has been processed according to the oxygen concentration distribution in the axial direction is attached to the upper shaft 12. A seed crystal 15 is attached to the lower shaft 13.

Then, the CZ silicon crystal 14 is melted by the high frequency heating coil 16 or the like, and then fused to the seed crystal 15. The crystallization side semiconductor rod (semiconductor silicon single crystal 19) grown from the seed crystal is made dislocation-free by the diaphragm 17 and lowered relative to the high frequency heating coil 16 while rotating both axes, and the melting zone 18 is made of CZ silicon. The semiconductor silicon single crystal 19 is grown while moving upward relative to the crystal 14.

After forming the diaphragm 17, the semiconductor silicon single crystal 19 grown from the seed crystal 15 is grown while being expanded to a desired diameter to form the cone portion 22, and the cone portion 22 is formed, and between the CZ silicon crystal 14 and the semiconductor silicon single crystal 19. A melting zone 18 is formed in the substrate, and the straight body portion 21 is formed by growing the semiconductor silicon single crystal 19 while controlling it to have a desired diameter while adjusting the descending speed of the upper axis according to the diameter of the raw material crystal.

At this time, the semiconductor silicon single crystal can be manufactured under almost the same manufacturing conditions as the conventional manufacturing conditions without significantly changing the manufacturing conditions, and desired quality can be obtained without impairing the productivity of the semiconductor silicon single crystal. it can.

Then, the melting zone 18 is moved to the upper end of the CZ silicon crystal 14 to complete the growth of the straight body portion 21 of the semiconductor silicon single crystal 19, and the diameter of the semiconductor silicon single crystal 19 is reduced to form the semiconductor silicon single crystal 19. The production of the semiconductor silicon single crystal is completed by separating from the CZ silicon crystal 14.

According to the method for producing a semiconductor silicon single crystal of the present invention as described above, the shape of the CZ silicon crystal is processed after the shape of the CZ silicon crystal is processed according to the oxygen concentration distribution in the axial direction of the CZ silicon crystal acquired in advance. By using the prepared CZ silicon crystal as a raw material to produce a semiconductor silicon single crystal by the FZ method, it is possible to control the oxygen concentration of the entire semiconductor silicon single crystal produced to fall within a desired range. As a result, the quality required for manufacturing the device can be satisfied in the entire semiconductor silicon single crystal, so that the productivity of the crystal can be improved and the product can be stably supplied in a stable manner.

Further, in the method of manufacturing a semiconductor silicon single crystal by the FZ method using CZ silicon crystal as a raw material, even if the oxygen concentration distribution in the manufactured semiconductor silicon single crystal cross section is taken into consideration, the entire crystal has a predetermined oxygen concentration range. A semiconductor silicon single crystal can be manufactured. For example, in the entire axial direction of the semiconductor silicon single crystal produced by the FZ method, the oxygen concentration is 2.1×10 ¹⁶ atoms/cm ³ or more and 8.0×10 ¹⁶ atoms/cm ³ or less, and more preferably 4. It can be in the range of 0×10 ¹⁶ atoms/cm ³ or more and 5.0×10 ¹⁶ atoms/cm ³ or less.

Furthermore, except for adjusting the descending speed of the upper axis according to the diameter of the raw material crystal, there is no need to make any changes to the growth conditions on the single crystal side, so that other crystals such as the resistivity distribution in the crystal cross section The semiconductor silicon single crystal as described above can be manufactured without changing the quality. Therefore, desired quality can be obtained without impairing the productivity of the semiconductor silicon single crystal.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited thereto.

(Example)
According to the method for producing a semiconductor silicon single crystal of the present invention, the oxygen concentration is 4.0×10 ¹⁶ atoms/cm ^{3 to} 5.3×10 ¹⁶ atoms/in the entire axial direction of the semiconductor silicon single crystal produced by the FZ method. An FZ silicon single crystal having a crystal diameter of 200 mm was manufactured so as to be within the range of cm ³ .

First, a CZ silicon crystal was prepared as a raw material, and the oxygen concentration in the axial direction of this CZ silicon crystal was measured in advance to obtain an oxygen concentration distribution. The change in oxygen concentration in the longitudinal direction measured in advance at this time is as shown in FIG.

Next, from the change in the oxygen concentration of the raw material shown in FIG. 4, the change in the raw material diameter according to the change in the raw material supply rate necessary to suppress the change in the oxygen concentration in the crystal growth direction was calculated. FIG. 6 shows the rate of change in diameter in the longitudinal direction of the raw material, with the raw material diameter at the start of the straight body being 1.0. In this way, the raw material CZ silicon crystal was processed so that the diameter at the position where the oxygen concentration was low was smaller than the diameter at the position where the oxygen concentration was high.

Then, a semiconductor silicon single crystal was manufactured by the FZ method using the CZ silicon crystal processed into this shape as a raw material. At this time, the manufacturing conditions in the straight body were constant except that the descending speed of the upper shaft was gradually increased. At this time, the value of K calculated from the melt residence time, the melt surface area, and the furnace pressure was 18.6. (In this case, the oxygen introduction rate of the FZ silicon single crystal/raw material rod was calculated to be 2.7%)

The obtained crystals were sampled at arbitrary intervals and the oxygen concentration was measured at each position. As a result, the oxygen concentration range was as shown in FIG. 7. As shown in FIG. 7, the maximum value of the oxygen concentration in the entire semiconductor silicon single crystal produced by the FZ method is 5.3×10 ¹⁶ atoms/cm ³ , and the minimum value is 4.1×10 ¹⁶ atoms/cm ³ . , A crystal was obtained in which the whole fell within the desired oxygen concentration range.

(Comparative example)
The CZ silicon crystal whose oxygen concentration change in the longitudinal direction was almost the same as that of the raw material used in the example was used as the raw material, and the shape as in the example was not processed. Therefore, the upper shaft speed should be the same as before. An FZ silicon single crystal having a crystal diameter of 200 mm was manufactured under the same conditions as in Example except for the above.

As a result of sampling the crystals obtained by the crystal production of the comparative example at arbitrary intervals and measuring the oxygen concentration at each position, the oxygen concentration range was as shown in FIG. The maximum value of oxygen concentration in the entire crystal was 5.2×10 ¹⁶ atoms/cm ³ , and the minimum value was 3.6×10 ¹⁶ atoms/cm ³ .

The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the invention having substantially the same configuration as the technical idea described in the scope of the claims of the present invention and exhibiting the same action and effect is the present invention It is included in the technical scope of.

DESCRIPTION OF SYMBOLS 10... Semiconductor silicon single crystal manufacturing apparatus, 11... Chamber, 12... Upper axis,
13... Lower axis, 14... CZ silicon crystal, 15... Seed crystal,
16... High-frequency heating coil, 17... Drawing, 18... Melting zone,
19... Semiconductor silicon single crystal, 20... Dope nozzle, 21... Straight body part,
22... Cone part.

Claims (7)

In a method for producing a semiconductor silicon single crystal by the FZ method using a CZ silicon crystal produced by the CZ method as a raw material,
Preliminarily measuring the oxygen concentration in the axial direction of the CZ silicon crystal to obtain an oxygen concentration distribution,
Processing the shape of the CZ silicon crystal according to the obtained oxygen concentration distribution in the axial direction of the CZ silicon crystal;
And a step of producing the semiconductor silicon single crystal by the FZ method, using the CZ silicon crystal of which the shape is processed as a raw material, the method of producing the semiconductor silicon single crystal by the FZ method. In the step of processing the shape of the CZ silicon crystal,
2. The semiconductor silicon single crystal according to claim 1, wherein the CZ silicon crystal is processed so that the diameter of the CZ silicon crystal is changed in the axial direction so as to be correlated with the obtained oxygen concentration distribution of the CZ silicon crystal. Manufacturing method. In the step of processing the shape of the CZ silicon crystal,
In the axial oxygen concentration distribution of the obtained CZ silicon crystal, the diameter of the CZ silicon crystal at the low oxygen concentration position is smaller than the diameter of the CZ silicon crystal at the high oxygen concentration position. The method for producing a semiconductor silicon single crystal according to claim 2, wherein the method is performed. The method for producing a semiconductor silicon single crystal according to claim 1, wherein a diameter of the semiconductor silicon single crystal produced by the FZ method is 150 mm or more. 5. The CZ silicon crystal having an oxygen concentration of 50 times or more the desired oxygen concentration of the semiconductor silicon single crystal produced by the FZ method is used as a raw material. A method for producing a semiconductor silicon single crystal according to 1. The semiconductor silicon single crystal produced by the FZ method has an oxygen concentration of 2.1×10 ¹⁶ atoms/cm ³ or more and 8.0×10 ¹⁶ atoms/cm ³ or less in the entire axial direction. The method for producing a semiconductor silicon single crystal according to any one of claims 1 to 5. The semiconductor silicon single crystal produced by the FZ method as a whole has an oxygen concentration in the range of 4.0×10 ¹⁶ atoms/cm ³ or more and 5.0×10 ¹⁶ atoms/cm ³ or less in the entire axial direction. The method for producing a semiconductor silicon single crystal according to claim 6.

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