JP2000026196A - Silicon semiconductor substrate and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent vacancy defects from being caused by adding nitrogen and thereby to produce a heat-treated substrate having a high quality surface layer of denuded zone(DZ) in the production of a silicon single crystal substrate by a Czochralski method. SOLUTION: In this production, nitrogen is added at the time of producing a silicon single crystal by a Czochralski method and the produced silicon single crystal contg. 1×1013 to 1×1016 atoms/cm3 nitrogen is subjected to heat treatment to produce a semiconductor substrate in which the density of crystal defects each having a >=0.1 μm size (expressed in terms of the diameter), in the region ranging from the surface of the substrate to a 1 μm depth, is <=104 ((number of defects)/cm3). Thus, the objective substrate having an almost defectless surface layer of denuded zone(DZ) can be produced and a wafer that enable a high manufacturing yield of a device, can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the improvement of the quality of a silicon semiconductor substrate, and more particularly to a silicon semiconductor substrate for removing defects inside or on the surface of a substrate and improving the yield of devices formed on the substrate, and a method of manufacturing the same. About.

[0002]

2. Description of the Related Art When a semiconductor device is manufactured using a silicon semiconductor substrate, it is known that crystal defects in the substrate cause operation failure of the device, and the manufacturing yield of the device changes depending on the density of crystal defects in the substrate. ing. In recent years, COP (Crystal Originated) has been used as a crystal defect causing this device operation failure.
A defect called “Particle” has attracted attention.
This is because when a silicon semiconductor substrate is etched with a mixture of ammonia and hydrogen peroxide, pits are generated on the substrate surface due to lattice defects in the crystal, and the pits are measured by an inspection device that counts particles on the substrate surface. It is so called. The COP is a name indicating all the defects detected by such a measuring method, and is usually a Czochralski (CZ) method or a C
In a silicon single crystal grown by the Z method, the substance of this defect is considered to be an octahedral-like void in the crystal (hereinafter referred to as a vacancy defect), which is presumed to cause structural destruction of the device. Have been. Several techniques have been proposed as techniques for reducing or eliminating COPs harmful to device fabrication.

As a technique for eliminating COP, it is known that the crystal growth rate during growing a single crystal is 0.8 mm / min or less (Japanese Patent Laid-Open No. 2-267195). This is because the amount of vacancy type vacancies, which are the elements that create vacancy defects, at the crystal growth interface is reduced, and the cooling rate of the single crystal is reduced, thereby causing vacancy during cooling. Supersaturated vacancy type point defects (vac
ancy) is suppressed. However,
This method has a problem that productivity is lowered due to a reduction in growth rate, and another type of crystal defect such as a dislocation loop is generated from the COP.

As a technique for suppressing the generation of COP, control of the cooling behavior of a single crystal, in particular, when the single crystal
It is known that the control of the time for passing through the temperature range of 000 ° C. is effective (JP-A-8-12493, JP-A-8-91983, and JP-A-9-227289). Since these techniques do not significantly reduce the growth rate of the single crystal, there is no problem in terms of productivity.
The lower limit of the OP density reduction is about 10 ⁵ / cm ³ , and it is difficult to achieve a further reduction, for example, a density of 10 ⁴ / cm ³ or less.

[0005] Further, as a COP reduction technique, when the crystal is cooled at the time of growing the crystal, the holding time of the single crystal during the cooling in the temperature range of 850 ° C to 1100 ° C is set to less than 80 minutes, or the nitrogen concentration when growing the crystal is reduced. There is known a technique in which a silicon single crystal of 1 × 10 ¹⁴ / cm ³ is grown, then processed into a silicon wafer and then heat-treated at a temperature of 1000 ° C. or more for 1 hour or more (Japanese Patent Application Laid-Open No. 10-98047). This is a technique that makes it easier to eliminate defects during heat treatment by shifting the size distribution of COP generated during crystal production to a smaller size. However, the effect of this size reduction is more pronounced as the oxygen concentration is lower,
7 to 10 × 10 ¹⁷ / c commonly used in the Czochralski method
Not performed at an oxygen concentration of m ³ . For this reason, it is difficult to achieve both the provision of the gettering ability utilizing the generation of oxygen precipitates inside the substrate and the reduction of COP, which are usually obtained by increasing the oxygen concentration in the substrate.

In addition to the COP reduction technique at the time of growing a single crystal, there is also known a technique of reducing and eliminating COP on a substrate surface by performing a heat treatment after slicing and polishing a single crystal to form a substrate. . For example, JP-A-3-233
No. 936 proposes performing a heat treatment at 800 to 1250 ° C. for 10 hours or less. However,
When heat treatment is performed in an oxidizing atmosphere shown in the examples of this publication, there is a defect that vacancy defects are transferred to the substrate surface due to oxidative erosion of the substrate surface and pits on the substrate surface increase, and It is difficult to reduce the COP density within a range of 1 μm from the substrate surface to 10 ⁴ / cm ³ or less. Japanese Patent Application Laid-Open No. 59-20264 proposes a heat treatment in a hydrogen atmosphere. According to this method, the COP on the outermost surface can be eliminated by using a hydrogen atmosphere, and the COP density within 0.5 μm from the surface can be reduced to 10 ⁴ particles / cm ³ or less. The COP density cannot be reduced to 10 ⁴ pieces / cm ³ or less, and formation of a defect-free layer is insufficient from the viewpoint of device fabrication. Further, in this method, since an explosive atmosphere of hydrogen is used, it is necessary to take sufficient safety measures.

[0007] Regarding the addition of nitrogen during single crystal growth of silicon, the method of addition of nitrogen is described in JP-A-60-25.
No. 1190 is known. JP-A-57-17497 discloses an increase in crystal strength, and JP-A-8-91993 discloses a method of suppressing a change in resistivity as a nitrogen addition effect in a float zone (FZ) single crystal. Have been. Further, when oxygen is present in the single crystal, COP defects can be reduced by adding nitrogen. Graf et al. (The Electrochemical Soci
ety Proceeding Vol. 96-13,
pp. 117, 1996), regarding this mechanism, the same mechanism that suppresses vacancy type defects (vacancies) in FZ crystals also works in the case of CZ crystals, and vacancies that are aggregates of vacancy type defects are used. Infers that the size of the defect is reduced.

[0008]

SUMMARY OF THE INVENTION The present invention is to provide a silicon semiconductor substrate for producing a semiconductor device, with good productivity, a crystal defect which becomes a problem in device production which cannot be completely removed by the conventional technique as described above. It is an object of the present invention to provide a silicon semiconductor substrate that has been effectively reduced or eliminated and a method for manufacturing the same.

[0009]

Means for Solving the Problems We have made intensive studies on defects generated in a silicon semiconductor substrate, and found that defects having a problematic size can be almost completely eliminated in a device fabrication region of a silicon semiconductor substrate. The present invention has been completed.

That is, the present invention relates to Czochralski (C)
Z) A silicon semiconductor substrate obtained from a silicon single crystal grown by a method or a magnetic field applying CZ method, wherein a density of crystal defects having a diameter of 0.1 μm or more in terms of a diameter of at least 10 μm in a region from the substrate surface to a depth of 1 μm is 10%. A silicon semiconductor substrate characterized in that the number is ⁴ / cm ³ or less.
More preferably, the nitrogen content at the center of the thickness of the silicon semiconductor substrate is 1 × 10 ¹³ atoms / cm ³ or more.
It is a silicon semiconductor substrate having a density of × 10 ¹⁶ atoms / cm ³ or less. Further, the present invention provides the silicon semiconductor substrate having a nitrogen content of 1 × 10 ¹⁶ atoms / cm ³ or less, particularly 1 × 10 ¹³ atoms / cm ³ or more and 1 × 10 ¹⁶ atoms / cm ³ or more.
a silicon semiconductor substrate having a local concentration portion due to nitrogen segregation, which has a signal intensity of not more than 2 ms / cm ³ and a nitrogen concentration measured by secondary ion mass spectrometry in the substrate of not more than twice the average signal intensity. It is.

The present invention also relates to a CZ method or a CZ applying a magnetic field.
A silicon semiconductor substrate obtained from a silicon single crystal grown by a method, having a density distribution in which crystal defects decrease from the center of the substrate thickness toward the surface, and having a crystal defect of 0.1 μm or more in terms of diameter on the substrate surface. Area density 1 piece / cm
² or less, and the volume density of crystal defects having a diameter of 0.1 μm or more at a depth of 0.1 μm from the substrate surface is 1% or less of the substrate thickness center and the nitrogen content at the substrate thickness center is 1% or less. A silicon semiconductor substrate characterized by being at least 10 ¹³ atoms / cm ^{3 and not} more than 1 10 ¹⁶ atoms / cm ³ . The term “crystal defects” as used herein refers to any crystal defects that cause device failure, such as vacancy defects, oxygen precipitates, and stacking faults.

[0012] The present invention also provides a method of 1 × 10 ¹⁶ atoms /
The silicon semiconductor substrate obtained from a silicon single crystal grown by the CZ method or the magnetic field applied CZ method using a silicon melt containing cm ³ or more 1.5 × 10 ¹⁹ atoms / cm ³ or less of nitrogen, 1000 ° C. to 1,300 A method for producing a silicon semiconductor substrate, comprising performing heat treatment at a temperature of not more than 1 ° C. for 1 hour or more. Further, when growing a silicon single crystal by a CZ method or a CZ method applying a magnetic field, the pulling speed is set to V
(Mm / min), when the average value of the temperature gradient in the crystal in the pulling axis direction in the temperature range from the melting point of silicon to 1300 ° C. is G (° C./mm), V / G ≧ 0.2 (mm
² / ° C. min), and heat treatment is preferably performed in a non-oxidizing gas atmosphere or in a gas atmosphere containing oxygen in an amount of 0.01 vol% or more and 100 vol% or less. It is preferable that the surface of the substrate is mirror-finished by polishing the surface of the substrate after the heat treatment in 0.5 μm or more and 1.0 μm or less.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The silicon semiconductor substrate of the present invention is a silicon semiconductor substrate obtained from a silicon single crystal grown by a CZ method or a magnetic field applying CZ method, and has a diameter of at least 1 μm from the substrate surface. .1μ
It is necessary that the density of crystal defects of m or more be 10 ⁴ / cm ³ or less. We have examined crystal defects in the device fabrication region of the silicon semiconductor substrate, and as a result, defects that reliably cause structural destruction of the device have a size of 0.1 μm or more in terms of diameter. It has been found that defects smaller than the size often do not become obstacles. In addition, in device fabrication of a silicon semiconductor substrate, defects in a region from the surface to a depth of 1 μm greatly affect the yield. Therefore, at least in a region at a depth of 1 μm from the substrate surface, if a defect harmful to the device can be removed, The yield of devices to be created can be greatly improved. If the defect density is 10 ⁴ / cm ³ or less, the defect density is a ratio of one defect in a 1 cm × 1 cm × 1 μm region. If the defect size is considered to be sufficient when the current device size is considered. Conceivable.

Further, in the silicon semiconductor substrate of the present invention, nitrogen is supplied at 1 × 10 ¹³ atoms at the center of the substrate thickness.
/ Cm ³ or more and 1 × 10 ¹⁶ atoms / cm ³ or less, more preferably 5 × 10 ¹³ atoms / cm ³ or more and 1 × 10
¹⁶ atoms / cm ³ or less, and further 5 × 10 ¹⁴ atoms
It is preferably contained in the range from ms / cm ^{3 to} 1 × 10 ¹⁶ atoms / cm ³ . By introducing nitrogen into a silicon single crystal, the concentration of point defects and the aggregation behavior of point defects at the time of crystal growth change, transforming the vacancy defects into the crystal, and increasing the density to 10 ⁷ / cm ³ or more. Oxygen precipitates are generated. Depending on the pulling conditions, transformed vacancy defects may be generated at 5% or less of the density of oxygen precipitates. If the nitrogen content in the substrate is less than 1 × 10 ¹³ atoms / cm ³ , it is difficult to transform the vacancy defects, and 1 × 10 ¹⁶ atoms / cm ³ is difficult.
If it exceeds s / cm ³ , dislocation is likely to occur during crystal growth, and nitrogen forms complex defects with oxygen to change the resistance of the substrate, and stacking faults are more likely to occur by heat treatment. The nitrogen content in the substrate was determined by SIMS (Se
condary Ion Mass Spectros
copy)).

Further, in the present invention, the nitrogen content of the silicon semiconductor substrate is 1 × 10 ¹⁶ atoms / cm ^3.
Below, especially 1 × 10 ¹³ atoms / cm ³ or more and 1 × 10
It has a local concentration portion due to nitrogen segregation that is ¹⁶ atoms / cm ³ or less and the nitrogen concentration in the substrate measured by secondary ion mass spectrometry is twice or more the average signal intensity. Preferably, there is. Nitrogen introduced during crystal growth is not always uniformly distributed in the crystal. Depending on crystal growth conditions, local segregation and concentration of nitrogen may cause a local increase in signal intensity at an average nitrogen concentration or at least twice the intensity of the lower limit of measurement. This may be observed even when the average nitrogen concentration measured by SIMS is less than 1 × 10 ¹⁶ atoms / cm ³ or less than the lower limit of measurement. Even in such a case, the suppression of aggregation of point defects and the generation of oxygen precipitates during crystal growth are sufficient, and the defects can be easily eliminated by subsequent annealing.

The oxygen precipitates generated by the addition of nitrogen can be eliminated near the substrate surface by providing a density distribution in which the oxygen concentration decreases from the center of the substrate thickness toward the surface. Then, a density distribution in which crystal defects decrease from the center of the substrate thickness toward the surface is formed, and the diameter is reduced to 0.1 μm at a depth of 0.1 μm from the substrate surface.
It is necessary to reduce the volume density of the above crystal defects by two digits or more (1% or less) as compared with the center of the substrate thickness. The surface density of crystal defects having a diameter of 0.1 μm or more at the outermost surface of the substrate can be reduced to 1 / cm ² or less by heat treatment in a non-oxidizing atmosphere or surface polishing. If the density of these crystal defects (mainly oxygen precipitates) is exceeded, structural destruction of the device is likely to occur, and the yield of the device formed on the substrate will deteriorate.

A method for manufacturing such a silicon semiconductor substrate
The above conditions are determined by the CZ method or the magnetic field applying CZ method.
Any manufacturing method can be used as long as a substrate that satisfies
It is not limited. However, with good productivity and efficiency
In order to manufacture the silicon semiconductor substrate of the present invention,
1 × 10¹⁶atoms / cm^Three1.5 × 10 or more¹⁹at
oms / cm^ThreeUse a silicon melt containing the following nitrogen
Silicon grown by CZ method or CZ method applying magnetic field
A silicon semiconductor substrate obtained from a single crystal at a temperature of 1000 ° C. or higher
It is desirable to heat-treat at a temperature of 1300 ° C or less for 1 hour or more.
Good. The segregation coefficient of nitrogen is 7 × 10^-FourAnd 1 × 10
¹⁶atoms / cm^Three1.5 × 10 or more ¹⁹atoms /
cm^ThreeIf a silicon melt containing the following nitrogen is used,
× 10¹³atoms / cm^ThreeMore than 1 × 10¹⁶atoms
/ Cm^ThreeThe following nitrogen-containing crystals can be grown.

The CZ method or the magnetic field application CZ method
When growing a crystal, the pulling speed is set to V (mm / min),
Pull in the temperature range from the silicon melting point to 1300 ° C.
G (° C./m
m), the V / G value is 0.2 (mm^Two/ ℃ mi
n) Under the above conditions, 1 × 10¹⁶atoms
/ Cm^Three1.5 × 10 or more¹⁹atoms / cm^ThreeIncluding
Grown from a silicon melt that has
This is at a pulling speed of about 1.5 mm / min or more,
Nitrogen concentration is 1 × 10¹³atoms / cm^ThreeMore than 1 × 10
¹⁶atoms / cm ^ThreeCreated from the crystal)
Using a semiconductor substrate that has been
(DZ layer) can be made deeper than 1 μm.
You.

As described above, in the crystal containing nitrogen in the crystal, since oxygen precipitates are generated, defects can be almost completely eliminated only by outwardly diffusing oxygen on the wafer surface. Further, the transformed vacancy defect has an unstable form, and easily disappears by heat treatment. For it,
In conventional crystals, vacancy defects must be eliminated, and the elimination involves complicated absorption and release of silicon point defects and precipitation and release of oxygen in the crystal. Requires a high temperature of about 1200 ° C., and cannot be completely eliminated unless a dangerous gas such as hydrogen is used as the atmosphere. Regarding the heat treatment temperature of the present invention, 1000 ° C or higher and 1300 ° C or lower,
Desirably, the temperature is 1100 ° C or more and 1200 ° C or less. If the temperature is low, it takes a lot of time for oxygen to diffuse out,
If the temperature is too high, the thermal equilibrium solid solubility in the crystal will increase, preventing outward diffusion of oxygen. At 1150 ° C. or higher, the higher the temperature becomes, the more the surface of the substrate becomes rough. Generally, when the heat treatment furnace is operated at a high temperature, unexpected contamination of the furnace body is likely to occur. Therefore, it is desirable that the heat treatment temperature can be lowered to reduce the risk. Therefore, it is desirable to perform the heat treatment at a temperature as low as possible in the indicated temperature range, taking into account the required depth of the DZ layer and the allowable time of the heat treatment time from an economical viewpoint.

In the wafer of the present invention, since the oxygen precipitate inside grows by heat treatment, the heat-treated wafer can have a high-density gettering layer inside. A so-called IG wafer having a DZ layer on such a surface and a high density gettering layer inside, so-called three-stage heat treatment (outward diffusion of oxygen + formation of oxygen precipitation nuclei + formation of oxygen precipitates)
However, if the manufacturing method of the present invention is used, a wafer having a DZ layer having higher integrity than a normal IG wafer and having a high density gettering layer therein can be subjected to a single heat treatment. It is possible to create with.

The heat treatment atmosphere is preferably a non-oxidizing atmosphere in which the oxygen concentration on the wafer surface can be effectively reduced, and as a result, plate-like precipitates generated by the addition of nitrogen can be easily eliminated. As the non-oxidizing gas, an argon gas is desirable from the viewpoint of economy. Although the use of helium gas has the advantage of reducing the purity of the contained impurities, especially the amount of impurity oxygen in the gas, it is economical and difficult to handle the heat treatment furnace due to the large thermal conductivity of helium gas. There's a problem. Nitrogen gas is inappropriate because it forms nitride on the substrate surface. A reducing atmosphere such as hydrogen can be used because it has the same effect as argon gas, but it is not always suitable because of the difficulty of handling, especially the danger of explosion.

It should be further noted that it is necessary to reduce the amount of impurities mixed during the heat treatment as much as possible.
This is because oxygen in the atmosphere in the furnace including when the sample is inserted into the furnace has a great effect on the integrity of the DZ layer and the surface roughness of the crystal surface. Regarding this point, Japanese Patent Application No. 9-29
As pointed out in No. 7158. It also points out that by reducing impurities, it is possible to further improve the crystallinity of the surface layer, and to use this effect to smooth the COP pits present on the crystal surface before heat treatment. Is possible.

The atmosphere gas may be an atmosphere containing not less than 0.01 vol% and not more than 100 vol% of oxygen instead of a non-oxidizing atmosphere. In this case, the surface needs to be polished again. The merit of mixing oxygen is that the management of impurities such as moisture mixed during the heat treatment, which was pointed out in the previous section, can be relaxed. As a specific atmosphere, a gas obtained by mixing oxygen in an inert gas atmosphere such as argon is used. Although the amount of oxygen to be mixed is preferably several percent, it is also possible to use 100 vol% oxygen gas. The mixing amount is 0.01 vol
If it is less than%, it is necessary to strictly control the mixing of impurities such as moisture into the atmosphere gas, and the merit of mixing oxygen is lost. On the wafer surface after the heat treatment, traces of crystal defects are generated on the wafer surface like chemical etching pits due to an oxide film generated during the heat treatment, and thus the surface needs to be polished again. In order to completely remove defect marks, the surface needs to be polished by 0.5 μm or more. Also,
When the re-polishing amount is larger than 1.0 μm, the re-polishing amount is 0.1% in terms of diameter.
it is difficult to density the more crystal defects μm is 10 ⁴ / cm ³ or less is a thickness of the surface defect-free layer 1μm or more.

As described above, the heat treatment of the crystal containing nitrogen during the growth of the crystal makes it simpler than the conventional one.
Under heat treatment conditions that are safe and have little possibility of process contamination,
It is possible to obtain a DZ layer having a reduced defect density equal to or higher than that of a conventional heat-treated wafer and a depth higher than that of the conventional heat-treated wafer.

[0026]

The present invention will be specifically described below with reference to examples.

Reference Example As a reference example, the following eight crystals were pulled up by the Czochralski method. The oxygen concentration was about 6.5 to 8.5 × 10 ¹⁷ atoms / cm ³ (measured by an infrared absorption method using a conversion coefficient of JEIDA). Each crystal dissolves about 40 kg of raw material and has a diameter of 1
Create 55mm ingot of about 30kg, p-type 10
A crystal of Ωcm was obtained. Nitrogen was added by simultaneously dissolving a wafer having a nitride film formed on a non-doped silicon crystal by a CVD method at the time of dissolving the raw materials.

1) Pulling speed 1 mm / without adding nitrogen
A crystal was grown in min.

2) 7 × 10 ¹⁵ a of nitrogen in the melt of the raw material
toms / cm ³ was added, A crystal was grown at a pulling speed of 1mm / min. V / G at this time is 0.15 (mm ² /
° C min). The nitrogen concentration of the crystal was measured by SIMS, but no nitrogen was detected (1 × 10 ¹⁴ atoms / cm).
³ or less), and calculating the nitrogen concentration from the equilibrium segregation coefficient,
It was about 5 × 10 ¹² atoms / cm ^{3 in the} crystal.

3) Nitrogen in the melt of the raw material is 5 × 10 ¹⁶ a
toms / cm ³ was added, A crystal was grown at a pulling speed of 1mm / min. V / G at this time is 0.15 (mm ² /
° C min). The nitrogen concentration of the crystal was measured by SIMS, but no nitrogen was detected (1 × 10 ¹⁴ atoms / cm).
³ or less), and calculating the nitrogen concentration from the equilibrium segregation coefficient,
It was about 4 × 10 ¹³ atoms / cm ^{3 in the} crystal.

4) Nitrogen in the melt of the raw material is 3 × 10¹⁷a
toms / cm^ThreeAt a pulling speed of 1 mm / min.
A crystal was grown. V / G at this time is 0.15 (mm^Two/
° C min). Calculate nitrogen concentration from equilibrium segregation coefficient
Then, about 2 × 10 ¹⁴atoms / cm^ThreeTona
Was. When the nitrogen concentration of the crystal was measured by SIMS,
Quantification was not possible, but nitrogen background
Increase of local nitrogen signal at twice the intensity of
Admitted.

5) Nitrogen in the melt of the raw material is 5 × 10 ¹⁷ a
toms / cm ³ was added, A crystal was grown at a pulling speed of 1mm / min. V / G at this time is 0.15 (mm ² /
° C min). As a result of measuring the nitrogen concentration of the crystal by SIMS, the nitrogen concentration in the crystal was about 5 × 10 ¹⁴ atoms /
cm ³ . At the time of this SIMS measurement, an increase in the nitrogen concentration that was locally increased twice or more with respect to the average nitrogen signal was observed.

6) Nitrogen in the melt of the raw material is 5 × 10 ¹⁷ a
toms / cm ³ was added, A crystal was grown at a pulling speed of 2mm / min. V / G at this time is 0.3 (mm ² / ° C.)
min). Result of nitrogen concentration in the crystal was measured by SIMS, the nitrogen concentration in the crystal is about 5 × 10 ¹⁴ atoms / c
m ³ . At the time of this SIMS measurement, an increase in the nitrogen concentration that was locally increased twice or more with respect to the average nitrogen signal was observed.

7) Nitrogen in the melt of the raw material is 5 × 10 ¹⁸ a
toms / cm ³ was added, A crystal was grown at a pulling speed of 1mm / min. V / G at this time is 0.15 (mm ² /
° C min). As a result of measuring the nitrogen concentration of the crystal by SIMS, the nitrogen concentration in the crystal was about 5 × 10 ¹⁵ atoms /
cm ³ . At the time of this SIMS measurement, an increase in the nitrogen concentration that was locally increased twice or more with respect to the average nitrogen signal was observed.

8) Nitrogen is added to the raw material melt at 2 × 10 ¹⁹ a
toms / cm ³ was added, A crystal was grown at a pulling speed of 1mm / min. The crystal was polycrystallized on the way, but a dislocation-free single crystal was obtained from the upper part of the ingot. As a result of measuring the nitrogen concentration of the crystal by SIMS, the nitrogen concentration in the crystal was about 1.5.
× 10 ¹⁶ atoms / cm ³ . Also this SIM
At the time of the S measurement, an increase in the nitrogen concentration which was locally increased twice or more with respect to the average nitrogen signal was observed.

The COP of a wafer prepared from each of the above crystals
Table 1 shows the measured densities.

(Example 1) Reference examples 5) and 7)
Was processed under the heat treatment conditions of the present invention. 8
After being inserted into the furnace at 00 ° C., the temperature was raised at 10 ° C./min after the insertion and maintained at 1100 ° C. for 8 hours, then lowered at −10 ° C./min, and the substrate was taken out at 800 ° C. As a gas used for the heat treatment, a gas produced by a purifier at a use point using argon gas supplied by a cold evaporator was used. The impurity concentration in the gas was 5 ppm or less. This gas was used as an atmosphere throughout the heat treatment. At the time of inserting the substrate, purging was performed by a purge box provided in front of the furnace, and after confirming that the atmosphere in front of the furnace in which the sample was on standby was an argon atmosphere with impurities of 5 ppm or less, the furnace port was opened and the substrate was opened. Was inserted.

The nitrogen concentration of the substrate thickness center after heat treatment was measured by SIMS and cleaving the substrate, about 5 × 10 ¹⁴
atoms / cm ³ .

In order to evaluate the quality of the DZ layer on the substrate surface after the heat treatment, a 25 nm oxide film was formed on each substrate surface after the heat treatment in a dry oxygen atmosphere at 1000 ° C., and the oxide film breakdown voltage was measured. The electrode used for the breakdown voltage measurement was a 20 mm ² polysilicon electrode, and the determination current was 1 μA. Table 3 shows the results. The percentage of oxide films showing so-called C-mode breakdown showing a breakdown voltage of 8 MV or more indicating the percentage of non-defective products is 99%, and almost all oxide films are non-defective products, which is much larger than 20% when no heat treatment is performed. Improvement was noted. Further, the ratio of those showing a withstand voltage of 11 MV or more at a judgment current of 100 mA was 95%.

Further, to examine the defect density after the heat treatment,
Create a substrate that has been subjected to the same heat treatment as above, and repeat the ammonia hydrogen peroxide solution cleaning to make the surface a total of 0.1 μm.
m, and the diameter is increased by 0.1 μm
The defect density was calculated from the above number of COPs. Table 2 shows the results
Shown in The COP density on the surface after the heat treatment was 14 / wafer, and was about 0.1 / cm ² . Furthermore, the number of COPs was 14 / wafer even when the ammonia hydrogen peroxide water cleaning was repeated, and no increase in COP was observed. From this, it was found that the density of crystal defects having a diameter of 0.1 μm or more was less than 10 ³ / cm ³ .

In order to examine the density of defects in the DZ layer of the wafer, the surface of the substrate was polished by mirror polishing to 1 μm, and the COP was measured. 0.1 μm after mirror polishing
The above COP was 20 wafers / wafer, but the surface was reduced to 0.1 μm by repeating washing with aqueous ammonia and hydrogen peroxide.
When the COP of 0.1 μm or more was measured after m etching, the number was 25 / wafer, and the density of crystal defects of 0.1 μm or more in diameter conversion was about 3 × 10 ³ / cm ³ .

In order to measure the withstand voltage of the oxide film in the polished state of 1 μm, the withstand voltage of the oxide film was measured in the same manner as described above. The ratio of the oxide film showing a withstand voltage of 8 MV or more at 1 μA was 95% and 99%, and 11% at a determination current of 100 mA.
The ratio of those showing a withstand voltage of MV or more was 92%.

In order to measure the density of the COP at a deeper place, mirror polishing was further performed for 2 μm (total 3 μm from the original surface), and the density of the COP of 0.1 μm or more was 20 / wafer. As described in the previous section, cleaning with ammonia and hydrogen peroxide is repeated, and after etching 0.1 μm, C
The OP was 70 / wafer when measured. From this, the density of crystal defects having a diameter of 0.1 μm or more in terms of a diameter of 3 μm below the surface was estimated to be 3 × 10 ⁴ / cm ³ .

In order to measure the defect density inside the substrate,
0.2 in terms of diameter at substrate thickness center by infrared tomography
When the density of defects having a size of μm or more was measured, 7 × 10⁶Pieces/
cm^Three And the defect density of 0.1 μm or more is more
Become. Defects at a depth of 0.1 μm from the surface of this substrate
Density is 10^ThreePieces / cm^ThreeLess than
It was found that the defect density was 1% or less as compared with.

This wafer did not show any other kind of defects such as stacking faults inside the substrate, and was confirmed to be a high quality silicon wafer.

Example 2 The wafer of Reference Example 6) was processed under the heat treatment conditions of the present invention. A heat treatment equivalent to the heat treatment of Example 1 was performed on the wafer prepared from the crystal of Reference Example 6). After the heat treatment, the substrate was cleaved, and the nitrogen concentration at the center of the substrate thickness was measured by SIMS to be about 5 × 10 ¹⁴ atoms.
s / cm ³ .

Similarly, the surface of the wafer subjected to the heat treatment was treated with a.
When COPs of 1 μm or more were measured (Table 2), 12
The number of wafers was about 0.1 / cm ² . Repeat the washing with ammonia and hydrogen peroxide solution to make the surface 0.1μ
The number did not change even when the measurement was performed after m etching, and the number was 12 / wafer. From this, the density of crystal defects of 0.1 μm or more in terms of the diameter of the wafer surface due to the heat treatment is 1%.
It was found to be less than × 10 ³ pieces / cm ³ .

The breakdown voltage of the oxide film after the heat treatment was examined in the same manner as in Example 1 (Table 3). As a result, the ratio of 8 MV or more at a judgment current of 1 μA was 99%, and the breakdown voltage of 11 MV or more was shown at a judgment current of 100 mA. The proportion was 95%.

To examine the density of defects in the DZ layer of this wafer, the surface of this substrate was polished by mirror polishing to 1 μm, and the COP was measured. 0.1 μm after mirror polishing
The above COP was 10 wafers / wafer, but the surface was reduced to 0.1 μm by repeating washing with aqueous ammonia and hydrogen peroxide.
After etching, the number of COPs of 0.1 μm or more is 10 / wafer, and the density of crystal defects of 0.1 μm or more in terms of diameter is 1 × 10 ³ / wafer even in the region of 1 μm.
cm ³ .

When the oxide film breakdown voltage in the state of 1 μm polishing was examined, the ratio of 8 MV or more at a decision current of 1 μA was 99%, and the ratio of those showing a breakdown voltage of 11 MV or more at a decision current of 100 mA was 95%. . From this, it was found that the state of the crystal at the depth of 1 μm was almost the same as the outermost surface after the heat treatment from the viewpoint of the oxide film breakdown voltage.

Further, in order to examine the state of the defect inside the DZ, a further 2 μm (3 μm from the initial surface) was obtained by mirror polishing.
m) was polished, and the measured COP of 0.1 μm or more after polishing was 16 / wafer. Repeating the washing with an aqueous solution of ammonia and hydrogen peroxide and etching the surface to 0.1 μm, the measurement is 21 / wafer, which is 0.1 in terms of diameter.
The density of crystal defects of μm or more was estimated to be 3 × 10 ³ / cm ³ . The oxide film breakdown voltage is 8 at a judgment current of 1 μA.
The ratio of MV or higher was 95%, and the ratio of those showing a withstand voltage of 11 MV or higher at a judgment current of 100 mA was 90%. Therefore, as compared with the result of Example 1, it was shown that the defects can be eliminated deeper from the surface by increasing the pulling speed during crystal growth.

In order to measure the defect density inside the substrate,
0.2 in terms of diameter at substrate thickness center by infrared tomography
When the density of the defects of μm or more was measured, it was 9 × 10⁶Pieces/
cm^Three And the defect density of 0.1 μm or more is more
Become. Defects at a depth of 0.1 μm from the surface of this substrate
Density is 1 × 10^ThreePieces / cm^ThreeLess than the substrate
It was found that the defect density was 1% or less as compared with the inside.

It should be noted that, as in Example 1, no other kinds of defects such as stacking faults were found inside the substrate as in Example 1, and it was confirmed that the wafer was a high quality silicon wafer.

(Reference Example 9) Prepared from the crystal of Reference Example 6)
Inserted silicon substrate into furnace at 800 ° C.
After raising the temperature at 1100 ° C and holding at 1100 ° C for 8 hours,
The temperature was lowered at 10 ° C./min, and the substrate was taken out at 800 ° C.
However, unlike the first embodiment, the heat treatment atmosphere after the insertion is changed to
An argon atmosphere containing 5% oxygen was used. Base after heat treatment
The nitrogen concentration at the center of the thickness of the plate was measured in the same manner as in Example 1.
Roller about 5 × 10¹⁴atoms / cm ^ThreeMet.

In order to evaluate the quality of the DZ layer on the substrate surface after the heat treatment, the oxide film breakdown voltage was measured in the same manner as described above (Table 3). 90%, which was inferior to the case of heat treatment in the non-oxidizing atmosphere described in Example 1. In addition, one showing a withstand voltage of 11 MV or more at a judgment current of 100 mA is 1
7%.

In order to examine the COP of 0.1 μm or more after the heat treatment, a substrate which was subjected to the same heat treatment as above was prepared again. The COP density on the surface after the heat treatment was about 6000 / wafer, and was 40 / cm ² . Further, the surface is reduced to 0. 0 by repeating washing with ammonia hydrogen peroxide solution.
Even if a COP of 0.1 μm or more is measured after the etching of 1 μm, the increase in the COP is within the range of the error, and the defect is considered to have almost disappeared. It was not possible to determine the exact COP volume density for the COP.

As described above, since crystal defect marks are generated on the surface of the substrate which has been subjected to the heat treatment in the atmosphere containing oxygen,
It turns out that sufficient quality cannot be secured.

(Example 3) The substrate obtained in Reference Example 9 was heat treated to remove 1 μm of the surface in order to remove surface defect marks.
A mirror-polished substrate was prepared. 0.1 after polishing
The number of COPs of μm or more was 14 / wafer, and was about 0.1 / cm ² . Further, the washing with ammonia hydrogen peroxide was repeated in the same manner to measure the volume density of COP.
10 was ³ / cm ³ (Table 2). The breakdown voltage of the oxide film formed on the wafer after polishing by 1 μm was examined (Table 3).
The ratio of 8 MV or more at a judgment current of 1 μA is 95%, 100
90% were those with 11 MV or more in mA.

In order to examine the defect distribution in the depth direction of the substrate polished 1 μm after this heat treatment, the surface was further polished by 1 μm (total 2 μm from the substrate surface before the heat treatment).
Polishing). When the density of crystal defects having a diameter of 0.1 μm or more in terms of the diameter of this substrate was measured by repeated washing with aqueous ammonia and hydrogen peroxide, it was 9 × 10 ³ / cm ³ . When the breakdown voltage of the oxide film was examined, the ratio of 8 MV or more at a judgment current of 1 μA was 90%, and the ratio of 11 MV or more at 100 mA was 85%.

In order to measure the defect density inside the substrate,
0.2 in terms of diameter at substrate thickness center by infrared tomography
When the density of the defects of μm or more was measured, it was 9 × 10⁶Pieces/
cm^Three And the defect density of 0.1 μm or more is more
Become. Defects at a depth of 0.1 μm from the surface of this substrate
Density is 1 × 10^ThreePieces / cm^ThreeFrom the inside of the board
It was found that the defect density was 1% or less as compared with.

From the above results, the wafer after heat treatment was 1 μm.
By removing the COP on the surface by polishing,
Calculated that the density of crystal defects of 0.1 μm or more is 1 × 10^FourPieces/
cm ^ThreeC) where the depth of the defect-free layer is 1 μm or more
It turns out that Eha can be created.

Further, this wafer did not show any other kind of defects such as stacking faults inside the substrate, and was confirmed to be a high quality silicon wafer.

Reference Example 10 The substrate of Example 3
After polishing by μm (3 μm from the surface of the substrate before heat treatment), similarly, the density of crystal defects having a diameter of 0.1 μm or more was measured to be 7 × 10 ⁵ / cm ³ (Table 2). The ratio of 8 MV or more at a current of 1 μA is 75%, 100%
30% was obtained at 11 MV or more in mA (Table 3), and it was also found that the property was deteriorated when excessive polishing was performed.

Comparative Example 1 The oxide film breakdown voltage characteristics of the crystal of the reference example were evaluated in the same manner as described above. Table 4 shows the results.

(Comparative Example 2) The crystals of Reference Examples 1) and 2) were subjected to the heat treatment of Example 1 to obtain a surface and a depth of 1 μm.
Tables 5 and 6 show the measurement results of the COP density of μm and the withstand voltage of the oxide film. In each case, the density of crystal defects having a diameter of 0.1 μm or more in terms of diameter at a depth of 1 μm is 1 × 10 ⁴ / c.
m ³ , and the value of the oxide film breakdown voltage is lower than that of the example.

(Comparative Example 3) The crystal of Reference Example 8) was subjected to the heat treatment of Example 1, and the surface and the depth of 1 μm and 3 μm of C
Tables 5 and 6 show the measurement results of the OP density and the oxide film breakdown voltage. A COP density of 0.1 μm or more in terms of diameter is within the scope of the present invention, and although the oxide film breakdown voltage is almost the same as in Example 1, a diameter of about 10 μm generated inside the crystal is obtained.
Stacking faults protrude from the inside of the substrate to the surface, the surface density of crystal defects with a diameter of 0.1 μm or more on the substrate surface is 5 / cm ² , and a crystal with a diameter of 0.1 μm or more up to a depth of 1 μm. The volume density of defects is 5 × 10
^{It was 4} wafers / cm ³ , making the substrate unsuitable for device fabrication.

(Example 4) The crystals of Reference Examples 3) and 4) were subjected to the heat treatment of Example 1 and the results of measuring the surface and COP densities of 1 μm and 3 μm in depth and oxide film breakdown voltage are shown in Tables 7 and 8. Show. After the heat treatment, the substrate was cleaved and the nitrogen concentration at the center of the substrate thickness was measured by SIMS. However, nitrogen could not be quantified in any of Reference Examples 3) and 4). However,
At a signal intensity more than twice the background signal intensity, a local increase in the nitrogen signal was observed.

[0068]

[Table 1]

[0069]

[Table 2]

[0070]

[Table 3]

[0071]

[Table 4]

[0072]

[Table 5]

[0073]

[Table 6]

[0074]

[Table 7]

[0075]

[Table 8]

[0076]

The silicon semiconductor substrate of the present invention has very few crystal defects in the device formation region, so that the yield of semiconductor devices formed on the substrate can be improved,
Since the reliability is also improved, there is an effect that the productivity is improved and the cost is reduced in the device creation process.

Further, according to the method for manufacturing a silicon semiconductor substrate of the present invention, vacancy defects in the silicon semiconductor substrate can be effectively eliminated, and the size of the oxygen precipitate is small, so that the method is simple. Since it can be easily eliminated by heat treatment, it has become possible to manufacture a silicon semiconductor substrate having a high-quality single-crystal surface layer required for manufacturing a semiconductor device with high productivity.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Hikaru Sakamoto 3-35-1, Ida, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Technology Development Division of Nippon Steel Corporation (72) Inventor Katsuhiko Nakai Ida, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture 3-35-1 New Nippon Steel Corporation Technology Development Division (72) Inventor Taizo Hoshino 3434 Shimada, Hikari-shi, Yamaguchi Prefecture Nittetsu Electronics Co., Ltd.

Claims (9)

[Claims] 1. A silicon semiconductor substrate obtained from a silicon single crystal grown by a Czochralski method or a magnetic field application Czochralski method, wherein at least a region from the substrate surface to a depth of 1 μm has a diameter of 0.1 μm. A silicon semiconductor substrate, wherein the density of the above crystal defects is 10 ⁴ / cm ³ or less. 2. The method according to claim 1, wherein the nitrogen content at the center of the thickness of the silicon semiconductor substrate is 1 × 10 ¹³ atoms / cm ³ or more and 1 × 1.
2. The silicon semiconductor substrate according to claim 1, wherein said silicon semiconductor substrate is at most 0 ¹⁶ atoms / cm ³ . 3. The silicon semiconductor substrate has a nitrogen content of 1 ×.
A local concentration portion due to nitrogen segregation that has a signal intensity of 10 ¹⁶ atoms / cm ³ or less and the signal intensity of the substrate measured by secondary ion mass spectrometry is at least twice the average signal intensity. Item 2. The silicon semiconductor substrate according to Item 1. 4. The method according to claim 1, wherein the nitrogen content at the center of the thickness of the silicon semiconductor substrate is not less than 1 × 10 ¹³ atoms / cm ^{3 and not} more than 1 × 1.
A local concentration portion due to nitrogen segregation, which has a signal intensity of 0 ¹⁶ atoms / cm ³ or less, and a nitrogen concentration in the substrate measured by secondary ion mass spectrometry is twice or more the average signal intensity. Item 2. The silicon semiconductor substrate according to Item 1. 5. A silicon semiconductor substrate obtained from a silicon single crystal grown by a Czochralski method or a Czochralski method applying a magnetic field, having a density distribution in which crystal defects decrease from the center of the substrate thickness toward the surface. The surface density of crystal defects having a diameter of 0.1 μm or more on the substrate surface is 1 / cm ² or less, and a depth of 0.1 μm or less from the substrate surface.
The volume density of crystal defects of 0.1 μm or more in terms of diameter in μm is 1% or less as compared with the center of the substrate thickness, and the nitrogen content at the center of the substrate thickness is 1 × 10 ¹³ atoms.
/ Cm ³ or more and 1 × 10 ¹⁶ atoms / cm ³ or less. 6. 1 × 10 ¹⁶ atoms / cm ³ or more.
A silicon semiconductor substrate obtained from a silicon single crystal grown by a Czochralski method or a Czochralski method with the application of a magnetic field using a silicon melt containing nitrogen of 5 × 10 ¹⁹ atoms / cm ³ or less is heated at 1000 ° C. to 1300 ° C. A method for manufacturing a silicon semiconductor substrate, comprising performing heat treatment at the following temperature for at least one hour. 7. When growing a silicon single crystal by the Czochralski method or the Czochralski method with a magnetic field applied, the pulling speed is set to V (mm / min) and the melting point of silicon is increased by 13%.
When the average value of the temperature gradient in the crystal in the pulling axis direction in the temperature range up to 00 ° C. is G (° C./mm), V / G ≧
7. The method for manufacturing a silicon semiconductor substrate according to claim 6, wherein the silicon semiconductor substrate is grown under a condition satisfying 0.2 (mm ² / ° C. min). 8. The method according to claim 6, wherein the heat treatment is performed in a non-oxidizing gas atmosphere. 9. Oxygen is contained in an amount of 0.01 vol% or more and 100 vol.
8. The method for manufacturing a silicon semiconductor substrate according to claim 6, wherein after heat-treating in a gas atmosphere containing 1% or less, the substrate surface is further polished from 0.5 μm to 1.0 μm to make the substrate surface a mirror surface. .