JPH1192300A - Production of semiconductor substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for efficiently removing or capturing the contaminant impurities intruded into a semiconductor substrate and a semiconductor device during the production process and applicable even in the case of a thin epitaxial layer formed as a defectless layer. SOLUTION: A silicon single crystal ingot 3 pulled up from a molten silicon 2 in a quartz crucible 1 by CZ method or MCZ method is cut off from the molten silicon 2 in the course of the pull-up operation and the temperature of the silicon single crystal ingot 3 is quenched from >=1,200 deg.C to <=600 deg.C. Exclusively a region 3a containing excess void is taken out of the silicon single crystal ingot 3 and machined in the form of a wafer 5 and an epitaxial layer 6 is formed on the wafer 5 to obtain the objective semiconductor substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor substrate, and more particularly to a method of processing a silicon single crystal manufactured by a pulling method (CZ method) or a magnetic field application pulling method (MCZ method), such as an LSI. The present invention relates to a method for manufacturing a semiconductor substrate for manufacturing a semiconductor substrate used for a semiconductor device.

[0002]

2. Description of the Related Art A semiconductor device such as an LSI has as its basic characteristics that a PN junction has a small leak current and an MO.
It is required that the reliability of the gate oxide film of the S transistor be high. One of the causes of deteriorating these characteristics is a normal pulling method (CZ (Czochralski method)).
Magnetic field applied Czochralski method (MCZ), which pulls up a silicon single crystal while applying a magnetic field to suppress convection of silicon melt.
od) method, in the process of manufacturing a semiconductor substrate by manufacturing a silicon single crystal and processing the silicon single crystal and the process of manufacturing a semiconductor device on the obtained semiconductor substrate, heavy metal contamination on the semiconductor substrate and the semiconductor device. Contamination impurities such as elements may be mixed. As a technique for removing or capturing such a contaminant impurity from an operation region of a semiconductor device, there is a gettering technique. One of the most widely used gettering technologies is an intrinsic gettering method (IG (intrinsic inter-
nal gettering) method). In a semiconductor substrate obtained by processing a silicon single crystal manufactured by the CZ method or the MCZ method, oxygen dissolved from a quartz crucible storing a silicon melt as a raw material is mixed in as an impurity. The contaminant impurities are gettered by crystal defects formed by the precipitation of oxygen.

However, if crystal defects due to the oxygen precipitation exist in the surface layer of the semiconductor substrate, the characteristics of the semiconductor device will be degraded. Therefore, as a method for solving such a problem, for example, H. Tsuya, K. Ogawa, F. Shimur
a, Jpn. J. Appl. Phys. 20, L31 (1981). In this method, a defect-free layer is formed on a surface layer of a semiconductor substrate, and a defect region for gettering a contamination impurity is formed inside the semiconductor substrate by an IG method. First, a silicon substrate obtained by processing a silicon single crystal was 1150
Heat treatment in the range of 範 囲 C to 1200 ° C. to melt and decompose oxygen precipitate nuclei on the surface layer of the silicon substrate to diffuse oxygen outward, thereby reducing the oxygen concentration in the surface layer of the silicon substrate; To form In this step, oxygen precipitate nuclei and precipitates which are non-uniformly generated in the step of manufacturing a silicon single crystal by the CZ method or the MCZ method are dissolved. Thereafter, the silicon substrate is heat-treated at a temperature in the range of 500 ° C. to 800 ° C. to newly form oxygen precipitation nuclei and precipitates inside the silicon substrate, thereby manufacturing a semiconductor substrate. At this time, the above-mentioned 1150 ° C. to 1
Since the oxygen concentration has been sufficiently reduced by the heat treatment in the range of 200 ° C., no new oxygen precipitation nuclei and precipitates are formed, and the defect-free layer is maintained.

As one of the methods of manufacturing a semiconductor substrate having a structure in which a defect-free layer is formed on the surface thereof and a defect region for gettering is formed therein, the crystal quality of the defect-free layer is improved. In order to increase the quality, see, for example,
No. 2,270,26 discloses a method using an epitaxial substrate in which an epitaxial layer is formed as a defect-free layer on the surface of a silicon substrate obtained by processing a silicon single crystal produced by a CZ method or an MCZ method. This epitaxial substrate has a carbon concentration of 7 to 10 ppm,
On a silicon substrate having an oxygen concentration of 30 ppm, a film thickness of 10 μm
An epitaxial layer of m to 15 μm is formed. Carbon serves as a precipitation nucleus to promote the effect of oxygen precipitation. First, as a first step, the above-mentioned epitaxial substrate is heat-treated at 750 ° C. for 3 hours, so that oxygen precipitate nuclei and precipitates are formed inside the epitaxial substrate. Next, as a second step, after raising the temperature of the right epitaxial substrate from 750 ° C. to 1000 ° C.,
The semiconductor substrate is manufactured by performing the heat treatment for 4 hours.
In the second step, oxygen precipitate nuclei and precipitates formed inside the epitaxial substrate in the first step further grow,
Stabilize. By the above method, the heat treatment in the range of 1150 ° C. to 1200 ° C., which has been conventionally performed to form the defect-free layer, can be omitted, and the operation region of the semiconductor device can have a higher crystal quality than the conventional defect-free layer. It can be a good epitaxial layer.

[0005]

However, in the conventional method of manufacturing a semiconductor substrate disclosed in Japanese Patent Application Laid-Open No. 63-227026, the formation and growth of oxygen precipitate nuclei and precipitates after the formation of an epitaxial layer are not performed. Since the heat treatment is performed, the effect of the yield on the process in the process greatly affects the cost.

[0006] Further, since a Cl-based gas is used in a reactor for forming an epitaxial layer, the Cl-based gas corrodes a stainless steel gas pipe.
Mo, Fe, or the like scattered from the corroded gas pipe forms a deep level as a contaminant in the band gap of the semiconductor substrate in the process of forming the epitaxial layer, thereby deteriorating the characteristics of the semiconductor device. Therefore, it is necessary to getter contaminant impurities such as Mo and Fe.
In the conventional method for manufacturing a semiconductor substrate disclosed in the above publication, oxygen precipitation nuclei, which are getter sites for gettering contaminant impurities, are not formed during epitaxial layer formation. There is a drawback that there is no gettering ability for impurities.

[0007] With the recent integration of semiconductor devices, the chip area tends to increase more and more. For this reason, in order to improve the productivity of semiconductor devices, silicon substrates have been increasingly larger in diameter. With the increase in diameter of the silicon substrate, the epitaxial layer formed on the silicon substrate is deposited on the silicon substrate in a single-wafer-type reactor in order to secure uniformity in the plane of the thickness and resistance of the epitaxial layer formed on the silicon substrate. It is common to form. In a single-wafer reaction furnace, a silicon substrate is heated by a lamp, so that the silicon substrate is rapidly heated and rapidly cooled. As a result, in an epitaxial substrate obtained by forming an epitaxial layer on a silicon substrate, there is a problem that oxygen precipitation nuclei and precipitates are extremely reduced. This is considered to be due to the following reasons. That is, supersaturated oxygen present inside the silicon substrate aggregates and grows by heat treatment, and whether this growth proceeds stably depends on whether oxygen precipitate nuclei and precipitates exceed critical nuclei at the heat treatment temperature. Or not. This critical nucleus is larger as the temperature is higher, but when the silicon substrate is rapidly heated, there is no time for the small-sized oxygen precipitate nuclei and precipitates to grow sufficiently at low temperatures, so the oxygen precipitate nuclei after the epitaxial layer is formed. It is considered that the density of the precipitates is almost determined by the maximum temperature of the heat treatment.

[0008] Therefore, in order to obtain the density of oxygen precipitate nuclei and precipitates of the semiconductor substrate as required for gettering,
It is necessary to make the heat treatment time for forming and growing oxygen precipitate nuclei and precipitates on the epitaxial substrate longer, which causes a cost increase.
Further, if the heat treatment time is too long, and the oxygen precipitation nuclei and precipitates are excessively formed and grown, the crystal quality of the epitaxial layer is deteriorated (for example, dislocation (slip) or the like). In particular, when the thickness of the epitaxial layer is small, the crystal quality is significantly deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and it is possible to efficiently remove or capture contaminant impurities mixed in a semiconductor substrate or a semiconductor device during a manufacturing process of the semiconductor substrate or the semiconductor device, and to reduce the amount of silicon. It is an object of the present invention to provide a method of manufacturing a semiconductor substrate which can be applied even when an epitaxial layer formed as a defect-free layer on a substrate surface is thin.

[0010]

In order to solve the above problems, a method of manufacturing a semiconductor substrate according to the present invention is provided by a pulling method or a magnetic field applying pulling method from a silicon melt stored in a quartz crucible. A first step of rapidly cooling the temperature of the silicon single crystal ingot from 1200 ° C. or higher to 600 ° C. or lower after separating the silicon single crystal ingot being pulled from the silicon melt;
A second step of extracting only a region containing excessive vacancies generated therein from the silicon single crystal ingot produced in the first step and processing it into a wafer; and forming an epitaxial layer on the wafer. And a third step of manufacturing a semiconductor substrate.

According to a second aspect of the present invention, there is provided a method of manufacturing a semiconductor substrate, comprising: pulling a silicon single crystal ingot from a silicon melt stored in a quartz crucible by a pulling method or a magnetic field applying pulling method, and then again at 1200 ° C. And then raise the temperature of the silicon single crystal ingot to 6
A first step of quenching to not more than 00 ° C., and taking out only a region containing excessive vacancies generated therein from the silicon single crystal ingot produced in the first step,
The method is characterized by comprising a second step of processing into a wafer and a third step of forming an epitaxial layer on the wafer to manufacture a semiconductor substrate.

According to a third aspect of the present invention, in the method of manufacturing a semiconductor substrate, the silicon single crystal ingot is pulled up from a silicon melt stored in a quartz crucible by a pulling method or a magnetic field application pulling method. Is divided into a plurality of blocks of a predetermined size, and the plurality of blocks are heated at a temperature of 1200 ° C. or more, respectively, and then quenched to 600 ° C. or less; A second step of extracting only a region containing excessive vacancies generated therein from the silicon single crystal ingot thus processed and processing it into a wafer, and forming an epitaxial layer on the wafer to manufacture a semiconductor substrate And a third step.

According to a fourth aspect of the present invention, there is provided the method of manufacturing a semiconductor substrate according to any one of the first to third aspects, wherein after the first step, the silicon single crystal ingot or the plurality of silicon single crystal ingots is provided. The temperature of the block should be between 400 ° C and 60 ° C.
Hold for a certain time in the range of 0 ° C or 400 ° C to 400 ° C
The method is characterized in that a fourth step of cooling to ま で C is performed.

According to a fifth aspect of the present invention, there is provided the method of manufacturing a semiconductor substrate according to any one of the first to fourth aspects, wherein after the second step, the wafer is subjected to a temperature of 500 ° C. to 8 ° C.
A fifth step of performing heat treatment in the range of 00 ° C. is performed.

According to a sixth aspect of the present invention, there is provided the method of manufacturing a semiconductor substrate according to any one of the first to fourth aspects, wherein after the second step, a polysilicon film having a predetermined thickness is formed on the back surface of the wafer. A sixth step of forming a layer is performed.

According to a seventh aspect of the present invention, there is provided the method of manufacturing a semiconductor substrate according to any one of the first to sixth aspects, wherein the oxygen concentration in the semiconductor substrate is 16 ppm to 35 ppm. .

The invention according to claim 8 relates to the method for manufacturing a semiconductor substrate according to any one of claims 1 to 7, wherein in the first step, carbon is added to the silicon melt, and 0.5 to 15 ppm of carbon concentration in the substrate
ppm.

[0018]

According to the method of manufacturing a semiconductor substrate having the structure of the present invention, the temperature of a silicon single crystal ingot or a block manufactured by a pulling method or a magnetic field applying pulling method is set to 120 ° C.
After quenching from 0 ° C. or higher to 600 ° C. or lower, only a region containing excess vacancies generated in the silicon single crystal ingot or block is taken out and processed into a wafer, and an epitaxial layer is formed on the wafer. To form a semiconductor substrate. This makes it possible to efficiently remove or capture contaminant impurities mixed into the semiconductor substrate or the semiconductor device during the manufacturing process of the semiconductor substrate or the semiconductor device, and to reduce the thickness of the epitaxial layer formed as a defect-free layer on the wafer surface. Can be applied because the crystal quality is not impaired. Therefore, productivity is improved, for example, the yield is improved.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. The description will be specifically made using an embodiment. A. First Embodiment FIG. 1 is a process chart showing a method for manufacturing a semiconductor substrate according to a first embodiment of the present invention. Hereinafter, the manufacturing process will be described step by step. First, as shown in FIG. 1A, the silicon melt 2 stored in a quartz crucible (growth furnace) 1
The temperature of the silicon single crystal ingot 3 being pulled up by the Z method or the MCZ method has reached 1200 ° C. or higher. Reference numeral 4 denotes a heater. FIG. 3A does not show an electromagnet for applying a magnetic field, which is used in the MCZ method. Therefore, after the silicon single crystal ingot 3 being pulled is separated from the silicon melt 2, the temperature is rapidly cooled to 600 ° C. or less, for example, in about 4 minutes. As a result of this heat treatment, vacancies generated inside the silicon single crystal ingot 3 during its production diffuse outward from the outer peripheral portion of the silicon single crystal ingot 3.
Inside thereof, a vacancy excess containing region 3a is formed. These vacancies are considered to be useful for promoting oxygen precipitation as shown by the reaction formula (1).

[0020]

## EQU1 ## 2Si + 2Oi + V → SiO ₂ (1)

In the reaction formula (1), Si is a silicon atom, Oi is an oxygen atom existing at an interstitial position inside the silicon single crystal ingot 3 as an interstitial impurity, V is a vacancy,
SiO ₂ is an oxygen precipitate. After rapidly cooling the temperature of the silicon single crystal ingot 3 from 1200 ° C. or more to 600 ° C. or less, the temperature is set in the range of 400 ° C. to 600 ° C. in order to grow oxygen precipitation nuclei as getter sites. It may be held for a fixed time. In this case, the oxygen concentration is desirably 16 ppm to 35 ppm. The same applies to other embodiments.

In order to further promote oxygen precipitation, C
Silicon single crystal ingot 3 by Z method or MCZ method
May be added to the quartz crucible 1 together with polycrystalline silicon as a raw material. Carbon atoms are mixed into the lattice positions of the silicon single crystal ingot 3 as substitutional impurities. Since this carbon atom has a covalent bond radius 30% to 40% smaller than that of the silicon atom, the distance between the silicon atoms around the carbon atom is longer than that in the case of no defect. Therefore, impurity oxygen easily collects, and precipitation easily occurs. In this case, the carbon concentration is 0.1.
5 ppm to 15 ppm is desirable. The same applies to other embodiments.

Next, the outer peripheral portion of the silicon single crystal ingot 3 is cut, and only the excess vacancy containing region 3a is taken out and processed into a wafer 5, and then the wafer 5 is heated to 500 ° C. to 800 ° C. Heat treatment is performed in the range to grow oxygen precipitation nuclei (FIG. 2B). This heat treatment need not be performed when the size of the oxygen precipitation nuclei is sufficiently large at the stage when the silicon single crystal ingot 3 is processed into the wafer 5. Then, as shown in FIG. 1C, an epitaxial layer 6 is formed on the wafer 5 to manufacture a semiconductor substrate.

B. Second Embodiment Next, a second embodiment will be described. FIG. 2 is a process chart showing a method for manufacturing a semiconductor substrate according to a second embodiment of the present invention. Hereinafter, the manufacturing process will be described step by step. First, as shown in FIG. 2A, a silicon single crystal ingot 13 is pulled up from a silicon melt 12 stored in a quartz crucible 11 by the CZ method or the MCZ method, and the tip of the silicon single crystal ingot 13 is The silicon single crystal ingot 13 is supplementarily heated by the heater 14 formed longer than usual to supplement the radiant heat of the silicon melt 2 by bringing the silicon single crystal ingot 13 closer to the melt 2 and the temperature thereof is again increased to 1200 ° C. or more. After raising, hold for a certain time. FIG. 2A does not show an electromagnet for applying a magnetic field, which is used in the MCZ method. Next, the temperature of the silicon single crystal ingot 13 was raised to 600 ° C.
The quenching is performed, for example, in about 4 minutes until the above, to form the excess vacancy containing region 13a therein. Incidentally, similarly to the first embodiment, if necessary, the temperature of the silicon single crystal ingot 13 is thereafter maintained within a range of 400 ° C. to 600 ° C. for a certain period of time, or the silicon single crystal ingot 13 is formed by the CZ method or the MCZ method. During the production of the crystal ingot 13, carbon may be added into the quartz crucible 11 together with silicon polycrystal as a raw material.

Next, the outer peripheral portion of the silicon single crystal ingot 13 is cut, only the excess vacancy-containing region 13a is taken out, processed into a wafer 15, and a polysilicon layer 16 having a thickness of about 1 μm is formed on the back surface of the wafer 15. Form (Fig. 2
(B)). This treatment is performed as the first heat treatment.
Heat treatment after processing the wafer 5 in the embodiment of FIG.
Is equivalent to two hours. With this process,
It is considered that the polysilicon layer 16 becomes a getter site of the contamination impurity. This process is called PBS (Poly-silicon Back
Seal) process. Then, as shown in FIG. 2C, an epitaxial layer 17 is formed on the wafer 15 to manufacture a semiconductor substrate.

C. Third Embodiment Next, a third embodiment will be described. FIG. 3 is a process chart showing a method for manufacturing a semiconductor substrate according to a third embodiment of the present invention. Hereinafter, the manufacturing process will be described step by step. First, a silicon single crystal ingot is manufactured by the CZ method or the MCZ method, and after taking out from the pulling furnace, the silicon single crystal ingot is divided into blocks 21a and 21b having appropriate sizes as shown in FIG. Divide. Next, each of the blocks 21a and 21b is
After heating to 00 ° C. or more, it is quenched to 600 ° C. or less, for example, for about 4 minutes, and inside the vacancy excess content region 2
2a and 22b are formed. Note that the first and second
In the same manner as in the embodiment of FIG.
a and 21b are kept in a range of 400 ° C. to 600 ° C. for a certain time, or carbon is added to a quartz crucible together with silicon polycrystal as a raw material in a quartz single crystal ingot by a CZ method or an MCZ method. May be.

Next, the outer peripheral portion of each of the blocks 21a and 21b is cut, and only the excess vacancy-containing regions 22a and 22b are taken out and processed into a wafer 23. If necessary, the wafer 23 is subjected to 500 ° Heat treatment is performed in the range of C to 800 ° C. to grow oxygen precipitation nuclei (see FIG. 3B). Then, as shown in FIG. 3C, an epitaxial layer 24 is formed on the wafer 23 to manufacture a semiconductor substrate.

Next, in order to compare the characteristics of the semiconductor substrate manufactured by the manufacturing methods of the above-described first to third embodiments with the characteristics of the semiconductor substrate manufactured by the conventional manufacturing method, a sample was prepared. The state of gettering was observed. For the sample, after contaminating the surface of a wafer processed from a silicon single crystal ingot or a block with Fe, an epitaxial layer was formed, and then a Schottky diode was formed by evaporating Al thereon. used. Fe contained in the epitaxial layer of this sample
Concentration is DLTS (Deep Level Transient Spectroscpy)
Was measured.

FIG. 4 shows details of the manufactured sample. Sample Nos. 1 and 2 were prepared by the conventional manufacturing method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 63-227026, and Sample Nos. A to I were manufactured by the manufacturing methods of the first to third embodiments. It was produced in. The conductivity type of each sample wafer is all boron-doped P-type. In FIG. 4, the pulling method is the pulling method used when producing a silicon single crystal ingot, and the MCZ method is used for samples of sample numbers E and F, and the CZ method is used for samples of other sample numbers. did. Oxygen concentration was controlled by rotating the crucible to dissolve oxygen from the quartz crucible. The carbon concentration is the concentration of carbon that was unintentionally mixed as an impurity during the production of the silicon single crystal ingot in the case of the sample numbers A to F. In the case of the samples of sample numbers 1, 2, and G to I, This is the concentration of carbon when carbon is added together with silicon polycrystal as a raw material in a quartz crucible at the time of producing a silicon single crystal ingot.

The thermal history of 1200 to 600 ° C. means how the temperature of the silicon single crystal ingot or block has been reduced from 1200 ° C. to 600 ° C. In the case of the samples of sample numbers 1 and 2, the temperature is lowered by a conventional method, and in the case of the samples of sample numbers A to I,
As described in the first to third embodiments, the temperature is rapidly cooled from 1200 ° C. to 600 ° C. in about 4 minutes. Similarly, the thermal history of 600 to 400 ° C. means that the temperature of a silicon single crystal ingot or a block is 600 ° C.
From 400 ° C to 400 ° C. In the case of the sample numbers 1, 2, B and D, the temperature is lowered by a conventional method, and in the case of the sample numbers A and I, as described in the first to third embodiments, The temperature is maintained at 450 ° C. for 2 hours, and in the case of samples C and E to H, the temperature is cooled.

The term “precipitation treatment before growing an epitaxial layer” means how a heat treatment is performed after a silicon single crystal ingot or a block is processed into a wafer and before an epitaxial layer is formed on the wafer surface. In the case of the sample numbers 1, 2, A and G, the right heat treatment was not performed, and the sample numbers C to E
In the case of sample No., the above PBS treatment was performed, and sample No. B
In the case of the sample, the temperature is maintained at 650 ° C. for 2 hours,
In the case of sample No. F, the temperature is maintained at 750 ° C. for 2 hours, and in the case of sample No. H, the temperature is maintained at 650 ° C.
The sample was held at ゜ C for 4 hours, and in the case of sample No. I, the temperature was held at 800 ° C for 2 hours. What is epi layer thickness?
The thickness of the epitaxial layer formed on the wafer surface,
Since it is not possible to measure a thin film, the film thickness is controlled by the time when the epitaxial layer is grown. In addition,
In the case of manufacturing a semiconductor device, it is necessary to perform a heat treatment at 700 ° C. for 3 hours after forming an epitaxial layer on the wafer surface, and then to perform a heat treatment at 1000 ° C. for 4 hours. Because it observes contamination by heavy metals mixed in the formation process,
These samples were not subjected to right heat treatment.

Contamination by Fe is performed by processing a silicon single crystal ingot or a block into a wafer, and then subjecting the wafer surface to APM (ammonia peroxide) → DHF (dilute hydrofluoric acid) → HP
After washing in the order of M (hydrochloric acid / hydrogen peroxide), the washing was performed. The contamination by Fe was performed by dropping a diluted standard solution for atomic absorption analysis onto the wafer surface, spreading the diluted solution over the entire wafer surface, spin coating, and then drying. The drop amount of the right standard solution was set so that the amount of Fe contamination after drying was 1 × 10 ¹¹ cm ⁻² when measured by total reflection X-ray fluorescence.

After the surface of the wafer is contaminated with Fe by the method described above, an epitaxial layer is formed on the surface of the wafer, and Al is further evaporated thereon to form a Schottky diode. Fe
The concentration was measured. FIG. 5 shows the measurement results. D used this time
The LTS has a Fe detection limit of 1 × 10 ¹⁰ cm ⁻³ .
As can be seen from FIG. 5, in the samples of Sample Nos. 1 and 2 manufactured by the conventional manufacturing method, Fe existing between the wafer and the epitaxial layer diffuses into the epitaxial layer in the process of forming the epitaxial layer, resulting in gettering. It has not been. On the other hand, in the samples of sample numbers A to I manufactured by the manufacturing methods of the first to third embodiments,
Compared with the samples of sample numbers 1 and 2, the Fe concentration is lower by two digits or more. This is presumably because getter sites formed by performing a quenching heat treatment at 1200 ° C. to 600 ° C. or other heat treatments before forming an epitaxial layer on the wafer surface worked effectively.
Further, in the samples of the sample numbers C to E, gettering is particularly effectively performed because the polysilicon layer formed on the back surface of the wafer is also a getter site of Fe.

Next, a sample similar to the sample shown in FIG. 4 is used as a semiconductor substrate, a diode is formed thereon,
The leak current at the N junction was measured. FIG. 6 shows a sectional view of a diode formed on a semiconductor substrate in this measurement.
First, for all the samples shown in FIG. 4, after forming an epitaxial layer on the wafer surface, 700 ° C.
3 hours and a heat treatment at 1000 ° C. for 4 hours to obtain a semiconductor substrate 31. This semiconductor substrate 31
With an acceleration voltage of 120 keV and an area concentration of 5 × 10 ¹³ atoms
After implanting boron ions (B ⁺ ) at about / cm ² , 117
Drive-in processing is performed at 5 ° C. for 2 hours to form a P-type well layer 32. Next, LOCOS (local oxidatio
After an element formation region 33 and an element isolation oxide film 34 are formed by the n of silicon method or the like, an N-type diffusion layer 34 is formed in the element formation region 33 to form a diode.

The PN constituted by the N-type diffusion layer 34 and the P-type well layer 32 of the diode thus manufactured.
A leak current was measured by applying a voltage of 5 V to the junction. FIG. 7 shows the measurement results. The area of the N-type diffusion layer 34 where the leak current was measured was 500 μm × 500 μm. The value of the leak current shown in FIG.
The leak current at the junction is measured, and the value is 20% from the larger value. Since 200 PN junctions are selected and measured from within the wafer surface, the values vary, but the sample numbers A to A using the semiconductor substrates manufactured by the manufacturing methods of the first to third embodiments are used. The leak current of all the samples of I was suppressed to the order of 10 ⁻¹² A. On the other hand, many leak currents of the samples of Sample Nos. 1 and 2 using the semiconductor substrate manufactured by the conventional manufacturing method were 10 ⁻⁷ A or more. It was confirmed by analysis that oxygen precipitates protruded to the epitaxial layer in such a place where the leak current was large. This oxygen precipitate is generated when a diode is manufactured to measure a leak current at a PN junction. From the above, according to the conventional manufacturing method, when the carbon concentration is high, after the epitaxial layer is formed on the wafer surface, oxygen precipitation occurs.
3 hours heat treatment at 700 ° C and 4 hours at 1000 ° C
It has been found that if the heat treatment is performed for a long time, a crystal defect is generated even in a relatively thick epitaxial layer, and the value of the leak current at the PN junction increases.

On the other hand, according to the manufacturing methods of the first to third embodiments, since the density of oxygen precipitates is an appropriate amount, gettering can be performed without impairing the crystal quality of the epitaxial layer. It has been found that a semiconductor substrate with high performance can be manufactured. As a result, the thickness of the epitaxial layer can be reduced. Further, since the heat treatment for depositing the oxygen precipitate as the getter site is performed in the state of the silicon single crystal ingot or the block, the productivity can be improved. Further, since the wafer is manufactured from the vacancy excess content region, oxygen can be easily precipitated. In addition, even when oxygen precipitates may be excessive,
Since the rapid heating process is performed at the time of forming the epitaxial layer, it can be avoided.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and a design change or the like may be made without departing from the gist of the present invention. Even if there is, it is included in the present invention. For example, in the above-described first and third embodiments, an example has been described in which the heat treatment is performed on the wafer 5 in the range of 500 ° C. to 800 ° C. as necessary, but is not limited thereto. The second mentioned above
As in the embodiment, a polysilicon layer 16 having a thickness of about 1 μm may be formed on the back surface of the wafer 15. Similarly, in the second embodiment described above, the film thickness of 1 μm
Instead of forming the polysilicon layer 16 of about m,
Heat treatment may be performed on wafer 5 at a temperature in the range of 500 ° C. to 800 ° C.

[0038]

As described above, according to the structure of the present invention, the temperature of the silicon single crystal ingot or the block manufactured by the pulling method or the magnetic field applying pulling method is set to 1 point.
After quenching from 200 ° C. or higher to 600 ° C. or lower, only the region containing excessive vacancies generated therein is taken out from the silicon single crystal ingot or block,
Since a semiconductor substrate is formed by processing the wafer to form an epitaxial layer on the wafer, contaminant impurities mixed into the semiconductor substrate or the semiconductor device during the manufacturing process of the semiconductor substrate or the semiconductor device can be efficiently removed or captured. In addition, even when the epitaxial layer formed as a defect-free layer on the wafer surface is thin, crystal quality is not impaired, so that the present invention can be applied. Thereby, productivity is improved, for example, the yield is improved.

[Brief description of the drawings]

FIG. 1 is a process chart showing a method for manufacturing a semiconductor substrate according to a first embodiment of the present invention.

FIG. 2 is a process chart showing a method for manufacturing a semiconductor substrate according to a second embodiment of the present invention.

FIG. 3 is a process chart showing a method for manufacturing a semiconductor substrate according to a third embodiment of the present invention.

FIG. 4 is a diagram showing a method of manufacturing a semiconductor substrate and manufacturing conditions according to a conventional technique and each embodiment of the present invention.

FIG. 5 is a view showing characteristics of a semiconductor substrate manufactured by a conventional method and a method of manufacturing a semiconductor substrate according to each embodiment of the present invention.

FIG. 6 is a cross-sectional view of a diode manufactured on a semiconductor substrate manufactured by a conventional method and a method of manufacturing a semiconductor substrate according to each embodiment of the present invention.

FIG. 7 is a diagram showing characteristics of a diode manufactured on a semiconductor substrate manufactured by a method of manufacturing a semiconductor substrate according to a conventional technique and each embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Quartz crucible 3,13 Silicon single crystal ingot 3a, 13a, 22a, 22b Vacancy excess area 5,15,23 Wafer 6,17,24 Epitaxial layer 16 Polysilicon layer 21a, 21b Block

Claims (8)

[Claims] 1. A silicon single crystal ingot in the middle of being pulled from a silicon melt stored in a quartz crucible by a pulling method or a magnetic field applying pulling method is separated from the silicon melt, and then the temperature of the silicon single crystal ingot is set to 1200 ° C. The first to rapidly cool from above C to below 600 ° C
A second step of extracting only a region containing excessive vacancies generated therein from the silicon single crystal ingot produced in the first step and processing it into a wafer; A third step of manufacturing a semiconductor substrate by forming an epitaxial layer on the semiconductor substrate. 2. A silicon single crystal ingot is pulled up from a silicon melt stored in a quartz crucible by a pulling method or a magnetic field application pulling method, and then heated again to 1200 ° C. or higher, and then the temperature of the silicon single crystal ingot is lowered. A first step of quenching to 600 ° C. or lower, and a step of taking out only a region containing excessive vacancies generated therein from the silicon single crystal ingot produced in the first step and processing the wafer into a wafer. 2. A method of manufacturing a semiconductor substrate, comprising: a second step; and a third step of manufacturing a semiconductor substrate by forming an epitaxial layer on the wafer. 3. After pulling up a silicon single crystal ingot from a silicon melt stored in a quartz crucible by a pulling method or a magnetic field applying pulling method, the silicon single crystal ingot is divided into a plurality of blocks of a predetermined size. ,
A first step of heating the temperature of each of the plurality of blocks to 1200 ° C. or more and then quenching to 600 ° C. or less; and a void generated inside the silicon single crystal ingot produced in the first step. A semiconductor substrate comprising: a second step of extracting only a region containing excessive holes and processing it into a wafer; and a third step of forming an epitaxial layer on the wafer to manufacture a semiconductor substrate. Manufacturing method. 4. After the first step, the temperature of the silicon single crystal ingot or the plurality of blocks is set to 400.
Hold for a certain time in the range of ゜ C to 600 ゜ C or 600 ゜ C
4. The method of manufacturing a semiconductor substrate according to claim 1, wherein a fourth step of removing the temperature from 400 ° C. to 400 ° C. is performed. 5. The method according to claim 5, further comprising: performing a heat treatment on the wafer at a temperature in a range of 500 ° C. to 800 ° C. after the second step.
5. The method of manufacturing a semiconductor substrate according to claim 1, wherein the following steps are performed. 6. The method according to claim 1, further comprising, after the second step, a sixth step of forming a polysilicon layer having a predetermined thickness on the back surface of the wafer. Of manufacturing a semiconductor substrate. 7. An oxygen concentration in the semiconductor substrate is 16 p.
7. The method of manufacturing a semiconductor substrate according to claim 1, wherein the concentration is from pm to 35 ppm. 8. The method according to claim 1, wherein in the first step, carbon is added to the silicon melt, and a carbon concentration in the semiconductor substrate is set to 0.5 ppm to 15 ppm. 2. The method for manufacturing a semiconductor substrate according to item 1.