JPH088263A - Semiconductor substrate - Google Patents

Abstract

(57) [Summary] [Structure] In addition to having an oxygen concentration of 10 × 10 ¹⁷ pieces / cm ³ , an area of 10 × 10 ¹⁷ pieces / cm ^{3 in} the region 10c from the back surface 10b to about half the thickness of the substrate. A semiconductor substrate containing a concentration of carbon. [Effect] Since the oxygen content is small, the DZ layer can be formed in the region from the surface 10a to about 1/2 of the thickness t of the semiconductor substrate 10 without performing the high temperature heat treatment, resulting in the formation of pits and oxide film. It is possible to prevent the occurrence of breakdown voltage failure. On the other hand, a free volume can be formed in the C-containing region of a predetermined concentration, and the oxygen precipitation reaction can proceed even if the oxygen concentration is low. Therefore, during the heat treatment at about 1000 ° C. for about 16 hours, which is performed during LSI manufacturing, oxygen precipitates can be simultaneously formed in the region from the back surface 10b to about ½ of the thickness t of the semiconductor substrate 10. IG layers can be formed by generating defects. Therefore, even if the semiconductor substrate 10 is contaminated by Fe, F
The e can be adsorbed to the IG layer, the occurrence of stacking faults can be prevented, and as a result, the increase in leak current due to stacking faults can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor substrate, and more particularly to a single crystal silicon (Si) semiconductor substrate used as a substrate for forming an integrated circuit such as an LSI.

[0002]

2. Description of the Related Art Most of semiconductor substrates used as substrates for forming integrated circuits such as LSIs are called the Czochralski method (CZ method) in which a Si melt filled in a quartz crucible is pulled up while rotating. It is manufactured from single crystal Si formed by the pulling method.

When single crystal Si is grown using such a CZ method, the quartz crucible itself dissolves in the Si melt and elutes oxygen, and this oxygen is generally introduced from the solid-liquid interface into the Si ingot ( 15 to 20) × 10 ¹⁷ particles / cm ³ is taken in.

On the other hand, for example, at 1000 ° C. which is a typical heat treatment temperature during LSI manufacturing, the solid solubility of oxygen in single crystal Si is about 3 × 10 ¹⁷ pieces / cm ³ , and even below 1000 ° C. Therefore, single crystal Si
The oxygen contained therein is always in a supersaturated state. For this reason, oxygen is precipitated in the single crystal Si semiconductor substrate (hereinafter simply referred to as a semiconductor substrate) during the heat treatment in the LSI manufacturing, and changes into a SiO _x structure. Then, the volume may expand and strain may occur around this, and when the strain occurs, minute defects such as dislocation loops and crystal defects occur.

When these minute defects exist within a range of several μm from the surface of the semiconductor substrate (active region of the LSI element), the breakdown voltage of the oxide film is lowered, leak current is generated, etc.
It is harmful to LSI. On the other hand, when present only inside the semiconductor substrate sufficiently distant from the surface, the microdefects adsorb heavy metal contaminants such as Fe (iron), Ni (nickel), and Cu (copper), and The so-called gettering action of removing from the active region of the device works, which is useful in manufacturing a high-quality LSI.

For the above reason, the oxygen concentration is (15-2
0) × 10 ¹⁷ pieces / cm ³ of the semiconductor substrate, the defect-free layer (hereinafter, referred to as D
Z (Denuded Zone) layer is formed, and a defect layer (hereinafter referred to as IG) in which the minute defects are present inside is formed.
A heat treatment for forming (Intrinsic gettering) layer is performed. Specifically, for example, the semiconductor substrate is heat-treated in a nitrogen atmosphere at 1100 to 1200 ° C. for about 4 hours to diffuse oxygen outward to reduce the oxygen concentration near the surface (formation of DZ layer), Then, heat treatment is performed in a nitrogen atmosphere at about 700 ° C. for about 4 hours to generate the oxygen precipitates at a high density inside the semiconductor substrate. After that, during the oxidation treatment at about 1000 ° C. for about 16 hours in an oxygen atmosphere during LSI manufacturing, the microdefects are generated from the oxygen precipitates (IG layer formation).

By the way, the oxygen concentration is (15 to 20) × 1
In the semiconductor substrate of 0 ¹⁷ pieces / cm ³ , there is a problem that the oxygen precipitate is generated when the ingot is pulled up because the concentration of oxygen content is high. In order to solve this problem, the oxygen concentration is (5-15) × 10
Semiconductor substrates having a low oxygen concentration controlled in the range of ¹⁷ / cm ³ are beginning to be used.

The oxygen concentration is (10 to 15) × 10 ¹⁷
Using a semiconductor substrate having a number of pieces / cm ³ , carbon is added at a location of 3 to 5 μm from the surface side by ion implantation to 4 × 10
A method has been proposed in which ¹⁶ pieces / cm ^{3 are} implanted and then heat treatment is performed to diffuse oxygen in the vicinity of the surface outward (Japanese Patent Laid-Open No. HEI 3).
-84931). By this method, a DZ layer without oxygen precipitates or micro defects is formed on the surface of the semiconductor substrate, while an IG layer with oxygen precipitates or micro defects is formed at a carbon injection position.

[0009]

In the above-mentioned semiconductor substrate having an oxygen concentration of (5 to 15) × 10 ¹⁷ pieces / cm ³ , the oxygen content is low, so that it is difficult to generate oxygen precipitates, and therefore IG There is a problem that it is difficult to form a layer. As a result, Fe, Ni, C are produced during the manufacture of the LSI.
When a semiconductor substrate is contaminated by a heavy metal such as u, these heavy metals form a stacking fault on the surface of the semiconductor substrate without being adsorbed by the IG layer, and this stacking fault causes a problem such as an increase in leak current. there were.

Further, the above-mentioned oxygen concentration is (15 to 20).
In the case of a semiconductor substrate having a density of × 10 ¹⁷ pieces / cm ³ , the oxygen content is high, and oxygen precipitates are often generated when the ingot is pulled up, and strain is generated around this. There was a problem that the dielectric strength of the oxide film formed was poor. Further, in such a semiconductor substrate having a high oxygen concentration, oxygen is diffused outward to form the DZ layer in the vicinity of the surface of the semiconductor substrate, and therefore the above-mentioned high temperature heat treatment at 1100 to 1200 ° C. is required. During this heat treatment, since the surface of the semiconductor substrate is easily contaminated by the trace amount of the heavy metal contained in the heat treatment furnace, the heavy metal serves as a nucleus to form a pit near the surface of the semiconductor substrate. There is also a problem that a breakdown voltage failure occurs.

Further, in the above method of implanting C from the surface of the semiconductor substrate having an oxygen concentration of (10 to 15) × 10 ¹⁷ pieces / cm ³ and then thermally treating and diffusing oxygen outward, Since the implantation concentration is low, there is a possibility that oxygen precipitates may be deposited in the vicinity of the surface of the semiconductor substrate, which makes it difficult to form the DZ layer. Further, if heat treatment is performed to prevent this, there is a problem that the pits are generated and the breakdown voltage of the oxide film is deteriorated.

The present invention has been made in view of the above problems and has an oxygen concentration of (5 to 15) × 10 ¹⁷ pieces / cm ^3.
The IG layer can be formed inside the semiconductor substrate, and even when the semiconductor substrate is contaminated by the heavy metal, these heavy metals can be adsorbed to the IG layer. An object of the present invention is to provide a semiconductor substrate that can prevent an increase in leak current.

The oxygen concentration is (15 to 20) × 10 ¹⁷
The DZ layer can be formed in the vicinity of the surface of the semiconductor substrate having the number of pieces / cm ³ without performing high-temperature heat treatment, and heavy metal contamination during heat treatment can be prevented. As a result, pit formation and oxide film formation can be prevented. It is an object of the present invention to provide a semiconductor substrate capable of preventing the occurrence of the withstand voltage failure.

[0014]

To achieve the above object, a semiconductor substrate according to the present invention has an oxygen concentration of 5 × 10 ¹⁷ to
A semiconductor substrate having a density of 15 × 10 ¹⁷ pieces / cm ³ and having a thickness of 2/3 or less from the back surface of the semiconductor substrate.
It is characterized by containing carbon at a concentration of ¹⁷ to 10 ¹⁸ carbons / cm ³ (1).

The semiconductor substrate according to the present invention is a semiconductor substrate having an oxygen concentration of 15 × 10 ^{17 to} 20 × 10 ¹⁷ pieces / cm ³ and has a thickness of 2/3 or less from the surface of the semiconductor substrate. In addition, it is characterized by containing carbon at a concentration of 10 ¹⁷ to 10 ¹⁸ carbons / cm ³ (2).

[0016]

When C (carbon) is implanted into a semiconductor substrate having an oxygen concentration of (5 to 15) × 10 ¹⁷ pieces / cm ³ by an ion implantation method or the like, the C is changed to Si as shown in the following formula 1. It is displaced in position to form free volume 3 / 2V and SiC.

[0017]

[Equation 1]

When the free volume 3 / 2V exists,
As shown in Equation 2 below, oxygen in the semiconductor substrate is Si
Reacts with oxygen precipitates (eg SiO ₂ ) and interstitial Si
(I) and are formed.

[0019]

[Equation 2]

That is, when a predetermined concentration of C is present, SiC is formed in the semiconductor substrate in this existing region, a free volume of 3/2 V is formed accordingly, and the reaction shown in the equation 2 proceeds to the right. , Oxygen concentration is (5-15) x 10 ¹⁷ pieces / c
Even in the case of m ³ , oxygen precipitates will be formed. Then, strain is likely to be generated around this, and when this strain is generated, micro defects are generated, and as a result, the IG layer is formed in the C-containing region of the semiconductor substrate.

When the C concentration is less than 10 ¹⁷ pieces / cm ³ , the amount of free volume 3/2 V formed is small, so that the oxygen precipitates are hardly formed, while when the C concentration exceeds 10 ¹⁸ pieces / cm ^3. , C are also present in interstitial positions and easily diffuse, and as a result, the oxygen precipitates and the minute defects may be formed even near the surface of the semiconductor substrate.

The oxygen concentration is (15 to 20) × 10 ¹⁷
Since the semiconductor substrate having the number of pieces / cm ³ has a high oxygen content, oxygen precipitates have already been formed at the time of pulling up the ingot. Also in this case, when C having a predetermined concentration is injected into the semiconductor substrate, SiC is formed in the existing region as shown in the above-mentioned equation 1, and accordingly, the free volume 3
/ 2V will be formed. Then this free volume 3
/ 2V relaxes the strain generated around the oxygen precipitates and prevents the generation of dislocations and stacking faults. As a result, DZ
A layer will be formed.

According to the semiconductor substrate (1) having the above structure, the semiconductor substrate has an oxygen concentration of 5 × 10 ¹⁷ to 15 × 10 ¹⁷ pieces / cm ³ , and the thickness is 2/3 from the back surface of the semiconductor substrate. Within the following range, C with a concentration of 10 ¹⁷ to 10 ¹⁸ pieces / cm ³
And the oxygen concentration is low, about 1/3 or more of the thickness of the semiconductor substrate from the surface can be obtained without performing high temperature (oxygen outward diffusion) heat treatment at 1100 to 1200 ° C. for about 4 hours in a nitrogen atmosphere. Thus, the DZ layer can be formed in the regions up to, and as a result, the occurrence of pits and the withstand voltage failure of the oxide film can be prevented. On the other hand, a free volume of 3 / 2V is formed in the C-containing region of a predetermined concentration, and the oxygen precipitation reaction can be advanced even with a low oxygen concentration. Therefore LS
I At the time of the surface oxidation treatment at about 1000 ° C. for about 16 hours in the oxygen atmosphere during manufacturing, oxygen precipitates can be simultaneously formed in the region from the back surface to ⅔ or less of the thickness of the semiconductor substrate. A defect can be generated to form the IG layer. Therefore, even when the semiconductor substrate is contaminated by heavy metal, the heavy metal can be adsorbed to the IG layer to prevent the occurrence of stacking faults, and as a result, increase in leakage current due to the occurrence of stacking faults can be prevented. It can be planned.

According to the semiconductor substrate (2) having the above structure, the oxygen concentration is 15 × 10 ^{17 to} 20 × 10 ¹⁷ pieces / cm ^3.
The oxygen content is high, and oxygen precipitates have already been formed at the time of pulling up the ingot. When a predetermined concentration of C is injected from the surface under such a condition, a free volume of 3 / 2V is formed in the C existing region, so that the strain generated around the oxygen precipitates is reduced to the free volume of 3 / 2V. Will certainly be alleviated. Therefore, the occurrence of dislocations and stacking faults can be prevented and the DZ layer can be formed without performing high-temperature heat treatment, and as a result, the occurrence of pits and the withstand voltage defect of the oxide film can be prevented.

[0025]

EXAMPLES AND COMPARATIVE EXAMPLES Examples of semiconductor substrates according to the present invention will be described below with reference to the drawings. Figure 1 is a sectional view schematically showing an embodiment of a semiconductor substrate (1) according to the present invention, reference numeral 10 denotes a semiconductor substrate having an oxygen concentration of 10 × 10 ¹⁷ atoms / cm ^3. Thickness t of semiconductor substrate 10
Is about 640 μm, and 1 × 10 ¹⁷ C / cm ³ implanted by the ion implantation method is applied to the entire region 10c from the back surface 10b of the semiconductor substrate 10 to 300 μm (about 1/2 t).
It is contained at a concentration of (denominator is a unit volume of the injection region).
When manufacturing this product, 1100 to 12 in a nitrogen atmosphere
Heat treatment at 00 ° C for about 4 hours and about 700 in nitrogen atmosphere
No heat treatment is performed at 4 ° C. for about 4 hours.

Using the semiconductor substrate 10 of the embodiment (1) having the above-mentioned structure, about 100 semiconductor chips are manufactured at the time of manufacturing an LSI.
After heat treatment at 0 ° C. for about 16 hours, the amount of oxygen precipitation in the thickness direction was measured. The oxygen precipitation amount was obtained by measuring the interstitial oxygen concentration before and after the heat treatment by FTIR (Fourier transform infrared absorption method) and subtracting the value after the heat treatment from the value before the heat treatment. Further, as a comparative example, a conventional semiconductor substrate containing no C and having an oxygen concentration of 10 × 10 ¹⁷ pieces / cm ³ was used, and heat treatment was performed at about 1000 ° C. for about 16 hours as in Example (1). The amount of oxygen precipitation in the thickness direction after the application was measured. The measurement results are shown in FIGS.

As is clear from these measurement results, C
In the case of the comparative example containing no oxygen, the oxygen precipitation amount was as small as about 0.5 × 10 ¹⁷ pieces / cm ^{3 in the} entire thickness direction (FIG. 3). On the other hand, in the case of the example (1), the amount of oxygen precipitation from the surface 10a to about 300 μm is as small as about 0.5 × 10 ¹⁷ pieces / cm ³ and is about 300 μm.
From the back to the back surface 10b, about 6.5 × 10 ¹⁷ pieces / c
It was rapidly increasing to m ³ (Fig. 2).

Next, the semiconductor substrate 10 according to the embodiment (1).
And Fe from the surface 10a in a nitrogen atmosphere at about 90
Diffuse for 20 minutes at 0 ° C, and then about 110 in oxygen atmosphere.
The surface 10a after being subjected to an oxidation treatment at 0 ° C. for about 16 hours
The stacking fault density of was measured. The stacking fault density was determined by an observation method using an optical microscope after subjecting the surface 10a of the semiconductor substrate to selective etching. As a comparative example, the conventional oxygen concentration not containing C is (5 to 15) ×
Using a semiconductor substrate of 10 ¹⁷ pieces / cm ³ , the stacking fault density on the surface after Fe was diffused and subjected to an oxidation treatment was measured in the same manner as in Example (1). The measurement results are shown in FIG.

As is apparent from FIG. 4, in the case of the comparative example not containing C, the stacking fault density is about 500 /
cm ² was large, but on the other hand, in the case of Example (1), it was extremely small.

As is clear from these results, in the semiconductor substrate 10 according to the embodiment (1), since the oxygen content is small, a high temperature (oxygen outward diffusion) at 1100 to 1200 ° C. for about 4 hours in a nitrogen atmosphere. Surface 1 without heat treatment
The DZ layer can be formed in the region from 0a to about 1/2 of the thickness t of the semiconductor substrate 10, and as a result, it is possible to prevent the occurrence of pits and the breakdown voltage failure of the oxide film.
On the other hand, a free volume of 3/2 V can be formed in a C-containing region of a predetermined concentration, and the oxygen concentration is low, 10 × 10 ¹⁷ pieces / cm ³
In this case also, the oxygen precipitation reaction can proceed. Therefore, at the time of heat treatment at about 1000 ° C. for about 16 hours, which is performed at the time of manufacturing the LSI, the semiconductor substrate 1 is simultaneously removed from the back surface 10b.
Oxygen precipitates can be formed in a region up to about 1/2 of the thickness t of 0, and micro defects can be generated to form the IG layer. Therefore, the semiconductor substrate 1 is made of Fe or the like.
Even when 0 is contaminated, Fe or the like can be adsorbed to the IG layer, and stacking faults can be prevented from occurring.
As a result, it is possible to prevent an increase in leak current due to the occurrence of stacking faults.

In Example (1), the oxygen concentration was 10 ×.
The case of the semiconductor substrate 10 having 10 ¹⁷ pieces / cm ³ has been described, but in another embodiment, the oxygen concentration is 5 to 9 × 10 ^17.
Even in the case of the semiconductor substrate having the number of pieces / cm ³ , 11 to 15 × 10 ¹⁷ pieces / cm ³ , it is possible to obtain substantially the same effect as in the case of the embodiment (1).

In the embodiment (1), the C concentration is 1 × 10.
^{Although 17} pieces / cm ³ has been described, in another embodiment, C is 2 × 10 ¹⁷ pieces / cm ³ to 10 × 10 ¹⁷ pieces / c.
Even if it contains m ^3, it is possible to obtain substantially the same effect as that of the embodiment (1).

In the embodiment (1), the case where C is contained in the entire region 10c from the back surface 10b of the semiconductor substrate 10 to about 1/2 t has been described, but in another embodiment, as shown in FIG.
Whole area 1 from back surface 11b to about 2 / 3t shown in (a)
Even in the semiconductor substrate 11 containing C in 1c, the embodiment (1)
It is possible to obtain an effect similar to that of Also,
In the semiconductor substrate 12 containing C in the area 12c from the back surface 12b shown in FIG. 5 (b) to about 2/3 t, or in the vicinity area 13c of about 2/3 t shown in FIG. 5 (c). The semiconductor substrate 13 containing C, or the semiconductor substrate 14 containing C in the region 14c near the back surface 14b shown in FIG. 5D.
However, it is possible to obtain substantially the same effect as that of the embodiment (1).

FIG. 6 is a sectional view schematically showing an embodiment (2) of the semiconductor substrate according to the present invention, in which 20 shows a semiconductor substrate having an oxygen concentration of 20 × 10 ¹⁷ pieces / cm ^3. ing. The semiconductor substrate 20 has a thickness t of about 640 μm, and is 300 μm (about 1/100 μm from the surface 20a of the semiconductor substrate 20).
All regions 20c up to 2 t) contain C implanted by the ion implantation method at a concentration of 1 × 10 ¹⁷ C / cm ³ (denominator is a unit volume of the implanted region). When this product is manufactured, heat treatment at 1100 to 1200 ° C. for about 4 hours in a nitrogen atmosphere and heat treatment at about 700 ° C. for about 4 hours in a nitrogen atmosphere are not performed.

Using the semiconductor substrate 20 of the embodiment (2) having the above-mentioned structure, about 100 semiconductor devices are manufactured.
After heat treatment at 0 ° C. for about 16 hours, the pit generation state on the surface 20a was observed by an optical microscope. In Comparative Example (1), the oxygen concentration not containing C was 10 × 1.
For a conventional semiconductor substrate of 0 ¹⁷ pieces / cm ³ , heat treatment at 1100 to 1200 ° C. for about 4 hours in a nitrogen atmosphere, heat treatment at about 700 ° C. for about 4 hours in a nitrogen atmosphere, and about 10
The thing which heat-processed at 00 degreeC for about 16 hours was used.
The observation results are shown in FIGS. 7 and 8.

As is clear from these observation results, C
In the case of the comparative example which did not contain Pd, pits were generated at high density (FIG. 8), while in the case of Example (2), no pits were generated at all (FIG. 7).

Next, the semiconductor substrate 2 which has been subjected to the above heat treatment
0 from the surface 20a to about 1/2 t, and about 1/2 t
To the back surface 20b, the oxygen precipitates existing in the range from TE to TE
Observed at M. The observation results are shown in FIGS.

As is clear from these observation results, C
In the range from the front surface 20a containing about 20 to about 1/2 t, even if oxygen precipitates are formed, distortion and dislocation are not generated around this (a), while from about 1/2 t to the back surface 20b. Dislocations were generated around the oxygen precipitates formed in the range up to (b).

Further, using the semiconductor substrate 20, the surface 20
After a to Fe were diffused in a nitrogen atmosphere at about 900 ° C. for 20 minutes and further subjected to an oxidation treatment at about 1100 ° C. for about 16 hours in an oxygen atmosphere, the stacking fault density of the surface 20a was measured. In addition, regarding the comparative example (1) described above as a comparative example and the conventional semiconductor substrate having an oxygen concentration of 20 × 10 ¹⁷ pieces / cm ³ and not containing C, as in the case of the example (2), Fe Comparative example (2) in which oxidization treatment was performed by diffusing
And the one used. The measurement result is shown in FIG.

As is apparent from FIG. 10, Comparative Example (2)
No DZ layer is formed and the stacking fault density is about 20
Although the number was as high as 00 / cm ² , the stacking fault density was as low as about 7 / cm ^{2 in} Example (2), which is substantially the same as in Comparative Example (1) in which the DZ layer was formed.

As is clear from these results, even if the oxygen content is high and oxygen precipitates have already been formed at the time of pulling up the ingot, C of a predetermined concentration is generated from the surface 20a under such an oxygen precipitation state. If implanted, a free volume of 3 / 2V is formed in the C-existing region, so the strain generated around the oxygen precipitates can be relaxed by the free volume of 3 / 2V. Therefore, it is possible to prevent dislocations and stacking faults from occurring without forming a high temperature heat treatment to form the DZ layer, and as a result, it is possible to prevent pits and oxide film breakdown voltage defects.

In Example (2), the oxygen concentration was 20 ×.
The case of the semiconductor substrate 20 of 10 ¹⁷ pieces / cm ³ has been described, but in another embodiment, the oxygen concentration is 15 to 19 × 1.
Even in the case of a semiconductor substrate of 0 ¹⁷ pieces / cm ³ , it is possible to obtain substantially the same effect as in the case of the embodiment (2).

In the embodiment (2), the C concentration is 1 × 10.
^{Although the} content of ¹⁷ pieces / cm ³ is described, in another embodiment, the C concentration is 2 × 10 ¹⁷ pieces / cm ³ to 10 × 1.
0 also those ¹⁷ / cm ³ containing, it is possible to obtain substantially the same effect as that of Example (2).

In the second embodiment, the case where C is contained in the entire region 20c from the surface 20a of the semiconductor substrate 20 to about 1/2 t has been described, but in another embodiment, as shown in FIG.
The entire area 2 from the surface 21a shown in (a) to about 2/3 t
The semiconductor substrate 11 containing C in 1c, or FIG.
Even in the semiconductor substrate 22 containing C in the region 22c near the surface 22a shown in (b), it is possible to obtain substantially the same effect as that of the embodiment (1).

[0045]

As described above in detail, in the semiconductor substrate (1) according to the present invention, since the oxygen concentration is low, a high temperature (oxygen outward diffusion) at 1100 to 1200 ° C. for about 4 hours in a nitrogen atmosphere. The DZ layer can be formed in a region from the surface to approximately 1/3 or more of the thickness of the semiconductor substrate without heat treatment, and as a result, pits and oxide film withstand voltage defects can be prevented. You can On the other hand, a predetermined concentration of C
A free volume of 3 / 2V is formed in the containing region, and the oxygen precipitation reaction can proceed even at a low oxygen concentration. For this reason, 1 at 1000 ° C in an oxygen atmosphere, which is used during LSI manufacturing.
At the time of surface oxidation treatment for about 6 hours, oxygen precipitates can be simultaneously formed from the back surface to a region up to ⅔ of the thickness of the semiconductor substrate, and micro defects can be generated to form the IG layer. it can. Therefore, even when the semiconductor substrate is contaminated with heavy metal, the heavy metal can be adsorbed to the IG layer to prevent the occurrence of stacking faults, and as a result, to prevent an increase in leakage current due to the stacking faults. You can

Further, in the semiconductor substrate (2) according to the present invention, even if the oxygen content is high and oxygen precipitates are already formed at the time of pulling up the ingot, under such a condition the predetermined concentration from the surface is reached. If C is injected, a free volume of 3 / 2V is formed in the C-existing region, and the strain generated around the oxygen precipitates can be reliably relaxed by the free volume of 3 / 2V. Therefore, the occurrence of dislocations and stacking faults can be prevented and the DZ layer can be formed without performing high-temperature heat treatment, and as a result, pits and oxide film withstand voltage defects can be prevented.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing an embodiment (1) of a semiconductor substrate according to the present invention.

FIG. 2 is about 1000 for the semiconductor substrate of Example (1).
It is a curve figure showing the measurement result of the amount of oxygen precipitation of the thickness direction after heat-processing for about 16 hours at ° C.

FIG. 3 relates to a semiconductor substrate of a comparative example, and 1 at about 1000 ° C.
It is a curve figure showing the measurement result of the amount of oxygen precipitation of the thickness direction after heat-processing for about 6 hours.

FIG. 4 relates to the semiconductor substrates of Example (1) and Comparative Example, and measures the stacking fault density after Fe is diffused from the surface of the semiconductor substrate and further subjected to an oxidation treatment in an oxygen atmosphere at about 1000 ° C. for about 16 hours. It is the graph which showed the result.

FIG. 5 is a cross-sectional view schematically showing a semiconductor substrate of another embodiment, in which (a) shows C over the entire area from the back surface to about 2/3 t.
Containing C, (b) containing C in the range from the back surface to about 2/3 t, (c) containing C in the region around 2/3 t, (d) The figure shows that the area near the back surface contains C.

FIG. 6 is a sectional view schematically showing an embodiment (2) of the semiconductor substrate according to the present invention.

FIG. 7 is about 1000 for the semiconductor substrate of Example (2).
It is a figure at the time of observing a pit with an optical microscope after heat-processing at about 16 hours for about 16 hours.

FIG. 8 shows a semiconductor substrate of Comparative Example 11 in a nitrogen atmosphere.
Heat treatment for about 4 hours at 00 to 1200 ° C., heat treatment for about 4 hours at about 700 ° C. in a nitrogen atmosphere, and about 1
It is a figure when pits are observed with an optical microscope after heat-processing for about 16 hours at 000 ° C.

FIG. 9 is about 1000 for the semiconductor substrate of Example (2).
It is a figure at the time of observing with TEM after heat-processing about 16 hours at (degreeC), (a) is an oxygen precipitate which exists in the range from a surface to about 1/2 of thickness, (b) is a thickness. About 1 /
2 shows oxygen precipitates existing in the range from 2 to the back surface.

FIG. 10 is a graph showing the measurement results of stacking fault density for the semiconductor substrates of Example (1), Comparative example (1) and Comparative example (2).

FIG. 11 is a cross-sectional view schematically showing a semiconductor substrate of another example, (a) containing C in the entire region from the surface to about 2/3 t, (b) near the surface A region containing C is shown.

[Explanation of symbols]

 10 semiconductor substrate 10b back surface 10c C-containing region

Claims (2)

[Claims] 1. A oxygen concentration 5 × 10 ¹⁷ to 15 a semiconductor substrate is a × 10 ¹⁷ atoms / cm ^3, in the range thickness of 2/3 from the back surface of the semiconductor substrate, ^{1017 18} Individual/
A semiconductor substrate containing carbon at a concentration of cm ³ . 2. An oxygen concentration of 15 × 10 ^{17 to} 20 × 10 ¹⁷
A semiconductor substrate is a number / cm ^3, and characterized in that the range of less than or equal to the thickness of 2/3 from the surface of the semiconductor substrate and contains carbon at a concentration of ^{1017 18} / cm ³ Semiconductor substrate.