JPH05308076A - Oxygen precipitation method of silicon wafer - Google Patents

Abstract

(57) [Summary] [Objective] Regarding the oxygen precipitation method of a silicon wafer in which oxygen is precipitated inside the silicon wafer manufactured by the Czochralski method, even a silicon wafer with a low oxygen concentration can be sufficiently processed with a short practical treatment time. An object of the present invention is to provide a method for oxygen precipitation of a silicon wafer capable of forming an amount of oxygen precipitate. [Structure] A silicon wafer is heated in a temperature range of about 1000 to 1200 ° C. to perform an outward diffusion heat treatment for diffusing surface oxygen outward, and then a low temperature heat treatment in a temperature range of about 300 to 600 ° C. Is performed in a crystal containing hydrogen or an atmosphere containing hydrogen. After this low temperature heat treatment, heat treatment at about 600 to 900 ° C. is performed to form oxygen precipitation nuclei, and subsequently high temperature heat treatment at about 900 to 1100 ° C. is performed to grow oxygen precipitates.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for precipitating oxygen in a silicon wafer produced by the Czochralski method, for example.

[0002]

2. Description of the Related Art Silicon wafers used as various semiconductor device substrates are manufactured by slicing a cylindrical silicon single crystal ingot by the Czochralski method. Since a silicon wafer as it is cut from an ingot contains a large amount of oxygen as an impurity, it is used as a substrate for a semiconductor device by performing heat treatment to remove oxygen from the surface layer of the silicon wafer and to precipitate oxygen inside the silicon wafer. Intrinsic gettering (I) which forms a substance and traps heavy metal impurities mixed in in a semiconductor device manufacturing process by an internal oxygen precipitate so that the heavy metal impurities are not mixed in a device active region of a surface layer (I
G) Technology is drawing attention.

In the conventional method for depositing oxygen on a silicon wafer, as shown in FIG. 1 (a), a cut silicon wafer is heated to a high temperature of about 1000 to 1200 ° C. to diffuse oxygen in the surface layer outward. After that, in a nitrogen or oxygen atmosphere, about 600 to form a precipitation nucleus of oxygen.
The heat treatment was performed at ˜900 ° C., and subsequently, the high temperature heat treatment was performed at about 900˜1150 ° C. to grow oxygen precipitates.

Along with the high integration of semiconductor devices formed on a silicon wafer, there is an increasing demand for the integrity of the DZ (dennoted zone) layer on the surface of the silicon wafer, which is the element active region. The oxygen concentration of the silicon single crystal needs to be lowered in order to reduce defects that are the main defects in the DZ layer and are caused by oxygen that causes a leak current.

[0005]

However, in the case of a silicon single crystal having a low oxygen concentration, it is difficult to form a sufficient oxygen precipitate inside the silicon wafer by the conventional oxygen precipitation method for a silicon wafer. There was a problem that the Trinsic gettering technology could not be utilized.

In order to solve such a problem, the inventor of the present application has proposed a method for depositing oxygen on a silicon wafer as shown in FIG. 1 (b). With this method, about 1000-1
After performing the outward diffusion heat treatment for heating the high temperature of 200 ° C. to diffuse the oxygen of the surface layer outward for about 90 minutes, before performing the heat treatment at about 600 to 900 ° C. for forming oxygen precipitation nuclei,
By performing a low temperature heat treatment for heating at a low temperature of about 400 to 600 ° C. for about 90 minutes, the formation of oxygen precipitation nuclei in the subsequent heat treatment step is promoted and sufficient oxygen precipitates are formed. ..

However, even this proposed method for oxygen precipitation of a silicon wafer is not sufficient in the case of a silicon single crystal having a low oxygen concentration, and it is difficult to form a sufficient amount of oxygen precipitates by heat treatment for a short time. There was a problem that. An object of the present invention is to provide an oxygen precipitation method for a silicon wafer, which can form a sufficient amount of oxygen precipitates in a short treatment time even with a silicon wafer having a low oxygen concentration.

[0008]

In the method of oxygen precipitation of a silicon wafer according to the present invention, a silicon wafer having a thickness of about 1000 is used.
˜1200 ° C., and after performing an outward diffusion heat treatment for diffusing the oxygen in the surface layer outward, about 300 to 60 ° C.
The low temperature heat treatment in the temperature range of 0 ° C. is performed in a crystal containing at least hydrogen or an atmosphere containing hydrogen.
After this low-temperature heat treatment, heat treatment at about 600 to 900 ° C. is performed to form oxygen precipitation nuclei, and subsequently high temperature heat treatment at about 900 to 1150 ° C. is performed to grow oxygen precipitates.

Further, in the method for depositing oxygen on a silicon wafer according to the present invention, hydrogen may be contained in the crystal at least during the low temperature heat treatment step, and hydrogen may be added at any time before the low temperature heat treatment step. .. For example,
Hydrogen may be added in the outward diffusion heat treatment step. Also, between the outward diffusion heat treatment step and the low temperature heat treatment step, about 30
A hydrogenation step of adding hydrogen within a temperature range of 0 to 1250 ° C may be newly provided. Further, hydrogen may be added during the low temperature heat treatment step.

[0010]

According to the present invention, the outward direction for diffusing oxygen outward
Oxygen precipitation heat treatment to precipitate oxygen after the diffusion heat treatment process
The low temperature heat treatment process performed before the process
Since it was carried out in an atmosphere containing hydrogen,
Even if it is a silicon wafer whose discharge is promoted and oxygen concentration is low,
A short treatment time can form a sufficient amount of oxygen precipitates.
You can In particular, it has been difficult to form oxygen precipitates in the past.
Was supposed to be n ⁺Type silicon single crystal wafer
Oxygen precipitates can be formed. Also, the strength of the crystal
Forming a wide DZ layer that can increase the degree
Will be possible.

[0011]

[Comparative Example 1] Comparative Example 1 is a conventional method for depositing oxygen on a silicon wafer. As shown in FIG.
After the silicon wafer is heated to a high temperature of about 1100 ° C. and an outward diffusion heat treatment for diffusing the oxygen in the surface layer outward is performed for about 90 minutes, a heat treatment at a temperature of about 650 ° C. in a nitrogen or oxygen atmosphere is performed for about 360 minutes. I went for a minute. After that, about 2 ℃ /
Min, about 3 ° C./min, or about 4 ° C./min, the temperature was raised, and heat treatment was performed at a temperature of about 1100 ° C. for about 30 minutes to form oxygen precipitates inside the silicon wafer.

The amount of oxygen precipitates deposited by the oxygen precipitation method for the silicon wafer of Comparative Example 1 was measured. In this measurement, a heat treatment at a temperature of about 1000 ° C. for about 180 minutes was added to clarify the difference in the amount of oxygen precipitation.
The measurement results are shown in FIG. The measurement point located in the lower right part of FIG. The total heat treatment time (excluding the additional heat treatment for 180 minutes) was about 615 minutes, and the oxygen precipitation amount was about 3.0 × 10 ¹⁷ cm ⁻³ .

The gettering ability was measured when the silicon wafer manufactured by the oxygen precipitation method of the silicon wafer of Comparative Example 1 (excluding the additional heat treatment for 180 minutes) was forcibly contaminated with Fe (iron). The surface contamination amount of Fe is 3.2 × 10 ¹³ cm ^-2 . The gettering ability is the difference between the Fe concentration of the CZ-As crystal (as-produced by the Czochralski method) or FZ-As crystal (as-produced by the floating zone method) and the conventional IG crystal. ..

Since the residual Fe concentration in the silicon wafer (process in which the total heat treatment time was 615 minutes) by the oxygen precipitation method of the silicon wafer of Comparative Example 1 (conventional IG) was about 2 × 10 ¹³ cm ^-3 , gettering was performed. Ability is Fe
It was about 1 × 10 ¹³ cm ⁻³ in terms of concentration. [Comparative Example 2] Comparative Example 2 is a proposed method for oxygen precipitation of a silicon wafer. As shown in FIG. 1 (b), a silicon wafer was heated to a high temperature of about 1100 ° C. to perform outward diffusion heat treatment for diffusing oxygen in the surface layer outward for about 90 minutes, and then in a nitrogen or oxygen atmosphere. A low temperature heat treatment was performed at a temperature of about 500 ° C. Then, the temperature was raised at a gradient of about 10 ° C./min, and heat treatment was performed at a temperature of about 700 ° C. for about 30 to 150 minutes to form oxygen precipitation nuclei inside the silicon wafer. Then about 2 ° C / min, about 3 ° C / min, or about 4 ° C
The temperature was raised at a gradient of / min and heat treatment was performed at a temperature of about 1100 ° C. for about 30 minutes to form oxygen precipitates inside the silicon wafer.

The amount of oxygen precipitates deposited by the oxygen precipitation method for the silicon wafer of Comparative Example 2 was measured. In this measurement, a heat treatment at a temperature of about 1000 ° C. for about 180 minutes was added to clarify the difference in the amount of oxygen precipitation.
The measurement results are shown in FIG. The measurement point ◯ is a measurement point when the temperature was raised at a temperature gradient of about 2 ° C./min when the heat treatment at about 700 ° C. was changed to the heat treatment at about 1100 ° C.
Is for a temperature gradient of about 3 ° C / min, and the measurement point □ is about 4
This is the case with a temperature gradient of ° C / min.

As is clear from FIG. 2, the oxygen precipitation amount increases as the total heat treatment time (excluding the additional heat treatment for 180 minutes) increases, but the oxygen precipitation amount saturates when the total heat treatment time is about 450 minutes. is doing. Although the amount of oxygen precipitation increased in a shorter time than in Comparative Example 1, the total heat treatment time was still required to be long. The silicon wafer manufactured by the oxygen precipitation method of the silicon wafer of Comparative Example 2 (excluding the additional heat treatment for 180 minutes) was forcibly Fe.
The gettering ability when polluted by (iron) was measured. The surface contamination amount of Fe is 3.2 × 10 ¹³ cm ^-2 .
Fe concentration of CZ-As crystal and FZ-As crystal (about 3 × 1
The difference between 0 ¹⁴ cm ⁻³ ) and the Fe concentration of the low temperature IG is the gettering ability.

The residual Fe concentration in the silicon wafer according to the oxygen precipitation method of the silicon wafer of Comparative Example 2 (process in which the total heat treatment time was 615 minutes) was about 7 × 10 ¹³ c.
Since it was m ⁻³ , the gettering ability was about 2 × 10 ¹⁴ cm ⁻³ in terms of Fe concentration. Compared to Comparative Example 1, the gettering ability is increased in terms of Fe concentration, but the total heat treatment time requires a long time of about 615 minutes. Example 1 In order to confirm the basic effect of the present invention,
Samples were prepared by three kinds of processes as shown in FIG.

In the first process, the wafer was heat-treated at 700 ° C. for 20 hours without any pretreatment, and then 1
Heat treatment at 000 ° C. for 10 hours. This is a conventional IG process. In the second process, 425 ° C for the wafer
Or after heat treatment at 454 ° C or 500 ° C for 60 minutes, heat treatment at 700 ° C for 20 hours, then 1000 ° C
Heat treatment for 10 hours. This is a low temperature IG process.

In the third process, 1 is applied to the wafer.
The crystal is doped with hydrogen by heat treatment in a hydrogen atmosphere at 200 ° C. for 25 minutes. After that, hydrogen is frozen in the crystal by quenching. Then, after heat treatment at 425 ° C. or 454 ° C. or 500 ° C. for 60 minutes, heat treatment is performed at 700 ° C. for 20 hours, and subsequently, heat treatment is performed at 1000 ° C. for 10 hours. This is a hydrogen low temperature IG process.

As shown in FIG. 5, in the low temperature hydrogen IG, the amount of precipitated oxygen is very large. This effect is caused by the presence of hydrogen in the crystal. This means 425 ° C or 45
It can be seen by comparing the thermal donor concentrations after heat treatment at 4 ° C. or 500 ° C. for 60 minutes. FIG. 6 shows the relationship between the heat treatment temperature and the thermal donor concentration. It can be seen that a large amount of thermal donors are formed in the crystal doped with hydrogen as compared with the crystal containing no hydrogen. This phenomenon is known to occur as a result of enhanced diffusion of oxygen. Therefore, it was confirmed that hydrogen was doped in the crystal by this method.

In consideration of the above-mentioned phenomenon, a practical FIG.
The effect was investigated by the process of the example as in (c).
The method for depositing oxygen on a silicon wafer according to this embodiment is shown in FIG.
As shown in (c), the silicon wafer is heated to about 1100 ° C.
After performing the outward diffusion heat treatment for diffusing the oxygen on the surface to the outside by heating for 90 minutes in an atmosphere in which nitrogen and hydrogen are mixed at a volume ratio of 1: 1, in an atmosphere of nitrogen or oxygen. Then, the low temperature heat treatment was performed at a temperature of about 500 ° C. After that, the temperature is increased with a gradient of about 10 ° C./minute,
Heat treatment at a temperature of about 700 ° C. for about 30 to 150 minutes,
Oxygen precipitation nuclei were formed inside the silicon wafer. Then, the temperature is raised at a gradient of about 2 ° C./min, about 3 ° C./min, or about 4 ° C./min, and heat treatment is performed at a temperature of about 1100 ° C. for about 30 minutes to form oxygen precipitates inside the silicon wafer. did.

The amount of oxygen precipitates deposited by the silicon wafer oxygen precipitation method of this example was measured. In this measurement, a heat treatment at a temperature of about 1000 ° C. for about 180 minutes is added to clarify the difference in the amount of oxygen precipitation. The measurement results are shown in FIG. The measurement point ● is about 2 ° C when transitioning from about 700 ° C heat treatment to about 1100 ° C heat treatment.
The measurement point is a case where the temperature gradient is increased at a temperature gradient of 1 / min, the measurement point ▲ is a case where the temperature gradient is about 3 ° C./minute, and the measurement point 1 is a case where the temperature gradient is about 4 ° C./minute.

As is clear from FIG. 2, the oxygen precipitation amount increases as the total heat treatment time (excluding the additional heat treatment for 180 minutes) increases, but the oxygen precipitation amount becomes saturated when the total heat treatment time is about 300 minutes. is doing. It can be seen that the amount of oxygen precipitation is dramatically increased as compared with Comparative Example 1, and the total heat treatment time is shortened as compared with Comparative Example 2.

The gettering ability when the silicon wafer (excluding the additional heat treatment for 180 minutes) manufactured by the oxygen precipitation method of the silicon wafer of this example was forcibly contaminated with Fe (iron) was measured. Fe contamination amount is 3.2
It is × 10 ¹³ cm ^-2 . The gettering ability is the difference between the Fe concentration of the CZ-As crystal and the FZ-As crystal (about 3 × 10 ¹⁴ cm ⁻³ ) and the Fe concentration of the low temperature hydrogen IG.

The Fe residual concentration in the silicon wafer according to the oxygen precipitation method for the silicon wafer of this embodiment (process in which the total heat treatment time was 360 minutes) was about 5 × 10 ¹³ c.
Since it was m ⁻³ , the gettering ability was about 2.5 × 10 ¹⁴ cm ⁻³ in terms of Fe concentration. Compared to Comparative Example 1, the gettering ability is dramatically higher than that of Comparative Example 2.
Gettering ability is further increasing. Moreover, the total heat treatment time is drastically shortened to about 360 minutes.

The same applies to the case of doping deuterium, tritium or helium instead of hydrogen in this embodiment. [Example 2] By using the method according to the present invention, a wide DZ layer can be formed, and a wafer with high crystal strength can be manufactured. Examples are shown below.

In this embodiment, oxygen outward diffusion treatment is not performed. The thickness of the wafer is 1 mm. The wafer is heat-treated in a hydrogen atmosphere at 1200 ° C. for 25 minutes to dope the crystal with hydrogen, and then the crystal is cooled to 600 ° C. at a temperature gradient of 2 ° C./minute. Since hydrogen has a large diffusion coefficient, it diffuses outward from the crystal surface during cooling. By utilizing this effect, hydrogen can be frozen only inside the wafer as shown in FIG. 7 (a).

As is clear from FIG. 5, the heat treatment at 425 ° C. does not cause the precipitation of oxygen in the crystal containing no hydrogen. Therefore, oxygen does not precipitate in the region of the wafer surface where hydrogen diffuses outward and the hydrogen concentration is low, but oxygen does occur in the region where hydrogen remains inside the wafer. Therefore, as shown in FIG.
A wafer having a wide DZ layer in which oxygen is precipitated only inside is manufactured. On the other hand, in a normal IG wafer, oxygen is precipitated on the entire wafer as shown in FIG. 7 (c).

As shown in FIG. 7 (b), in a wafer in which oxygen is precipitated only inside, the concentration of residual interstitial oxygen is high, and therefore the crystal strength is expected to increase. The result of confirming this effect is shown in FIG. 425 ℃ in hydrogen low temperature IG so that the micro defect density of the defect part becomes the same
After heat treatment at 700 ° C. for 20 hours and heat treatment at 1000 ° C. for 10 hours after heat treatment at 60 ° C. for 6 hours, for crystals not doped with hydrogen, after heat treatment at 425 ° C. for 60 minutes,
Heat treatment at 00 ° C. for 20 hours and heat treatment at 1000 ° C. for 15 hours are added.

A scratch was put on the surface of a 4-inch wafer with a diamond pen, and then the wafer was inserted into a temperature atmosphere of 1100 ° C. at a speed of 5 cm / min.
The wafer was pulled out from the temperature atmosphere of 0 ° C. at a rate of 5 cm / min, and this insertion / drawing was repeated 10 times. The distribution of dislocations generated from scratches is shown in FIG. Figure 8
8A is the case of the hydrogen low temperature IG of the embodiment, and FIG.
(B) is a case of low temperature IG. Hydrogen low temperature I of this example
In G, the dislocation region is narrower and the crystal strength is stronger than in low temperature IG.

Also in this embodiment, deuterium, tritium or helium may be doped instead of hydrogen. [Embodiment 3] An oxygen precipitation method for a silicon wafer according to this embodiment will be described with reference to FIGS.

First, the silicon wafer is heated to a high temperature of about 1100 ° C. to perform outward diffusion heat treatment for diffusing oxygen in the surface layer outward for about 90 minutes, and then, as shown in FIG. Hydrogen, deuterium, or tritium is added by ion implantation from the surface of the wafer opposite to the element formation surface. After that, the heat treatment was switched to a heat treatment in an atmosphere of nitrogen or oxygen, and a low temperature heat treatment at a temperature of about 500 ° C. was performed. After that, the temperature is increased with a gradient of about 10 ° C./minute,
Heat treatment at a temperature of about 700 ° C. for about 30 to 150 minutes,
Oxygen precipitation nuclei were formed inside the silicon wafer. Then, the temperature is raised at a gradient of about 2 ° C./min, about 3 ° C./min, or about 4 ° C./min, and heat treatment is performed at a temperature of about 1100 ° C. for about 30 minutes to form oxygen precipitates inside the silicon wafer. did.

In this example, as shown in FIG. 10A, hydrogen, deuterium, or tritium was ion-implanted from the surface of the silicon wafer opposite to the element formation surface.
As shown in 0 (b), hydrogen atoms or molecules can be frozen only near the surface of the surface of the silicon wafer opposite to the element formation surface. Therefore, as a result of the oxygen precipitation treatment, as shown in FIG. 10C, oxygen precipitation nuclei were formed only near the surface of the surface of the silicon wafer opposite to the element formation surface.

In this embodiment, helium may be doped instead of hydrogen, deuterium or tritium. [Embodiment 4] An oxygen precipitation method for a silicon wafer according to this embodiment will be described with reference to FIGS.

First, a silicon wafer is heated to a high temperature of about 1100 ° C. to perform outward diffusion heat treatment for diffusing oxygen in the surface layer outward for about 90 minutes in a nitrogen atmosphere, and then, as shown in FIG. Alternatively, hydrogen is added from the surface of the silicon wafer opposite to the element formation surface by plasma of deuterium or tritium. After that, the heat treatment was switched to a heat treatment in an atmosphere of nitrogen or oxygen, and a low temperature heat treatment at a temperature of about 500 ° C. was performed. Then, the temperature was raised at a gradient of about 10 ° C./min, and heat treatment was performed at a temperature of about 700 ° C. for about 30 to 150 minutes to form oxygen precipitation nuclei inside the silicon wafer. Then, the temperature is raised at a gradient of about 2 ° C./min, about 3 ° C./min, or about 4 ° C./min, and heat treatment is performed at a temperature of about 1100 ° C. for about 30 minutes to form oxygen precipitates inside the silicon wafer. did.

In this embodiment, as shown in FIG. 11A, a silicon oxide film is formed on the element formation surface of the silicon wafer.
It is placed in a plasma atmosphere of hydrogen, deuterium, or tritium while being covered with a protective film such as a silicon nitride film. Hydrogen is added from the surface of the silicon wafer, which is not covered with the protective film, opposite to the element formation surface. As a result, FIG.
As shown in (b), hydrogen atoms or molecules can be frozen only near the surface of the surface of the silicon wafer opposite to the element formation surface. Therefore, as a result of the oxygen precipitation treatment, as shown in FIG. 11C, oxygen precipitation nuclei were formed only near the surface of the surface of the silicon wafer opposite to the element formation surface.

In this embodiment, helium may be doped instead of hydrogen, deuterium or tritium.

[0038]

As described above, according to the present invention, the low temperature heat treatment step performed after the outward diffusion heat treatment step of diffusing oxygen outwardly and before the oxygen precipitation heat treatment step of precipitating oxygen contains hydrogen. Since it is carried out in an atmosphere containing crystals or hydrogen, the precipitation of oxygen is promoted, and a silicon wafer having a low oxygen concentration can form a sufficient amount of oxygen precipitates by a practically short treatment time. .. In particular, it is possible to form a sufficient amount of oxygen precipitates on an n ⁺ type silicon single crystal wafer, which has been conventionally considered to be difficult to form oxygen precipitates. Further, according to the present invention, the time required for the oxygen precipitation heat treatment step can be significantly shortened, so that the productivity can be dramatically improved. Further, by using the method according to the present invention, it is possible to manufacture a wafer having high crystal strength. It also becomes possible to form a wide DZ layer.

[Brief description of drawings]

FIG. 1 is a diagram showing a heat treatment process (Comparative Example 1, Comparative Example 2, Example 1) of an oxygen precipitation method for a silicon wafer according to the present invention.

FIG. 2 is a graph showing the relationship between the total heat treatment time and the oxygen precipitation amount according to the oxygen precipitation method for a silicon wafer of the present invention.

FIG. 3 is a graph showing the Fe gettering ability of a silicon wafer treated by the oxygen precipitation method for a silicon wafer of the present invention.

FIG. 4 is a diagram showing a heat treatment process of an oxygen precipitation method for a silicon wafer according to the present invention.

FIG. 5 is a graph showing the relationship between the heat treatment temperature of a silicon wafer treated by the oxygen precipitation method for a silicon wafer of the present invention and the oxygen precipitation amount.

FIG. 6 is a graph showing the relationship between the heat treatment temperature and the thermal donor concentration of a silicon wafer treated by the oxygen deposition method for a silicon wafer of the present invention.

FIG. 7 is a diagram showing a hydrogen concentration distribution and a defect density distribution in a silicon wafer treated by the method for depositing oxygen on a silicon wafer according to the present invention (Example 1).

FIG. 8 is a diagram for explaining the crystal strength of a silicon wafer treated by the oxygen precipitation method for a silicon wafer of the present invention.

FIG. 9 is a diagram showing a heat treatment process (Examples 3 and 4) of the oxygen precipitation method for a silicon wafer according to the present invention.

FIG. 10 is a diagram showing a hydrogen concentration distribution and a defect density distribution in a silicon wafer treated by the method for depositing oxygen on a silicon wafer of the present invention (Example 3).

FIG. 11 is a diagram showing a hydrogen concentration distribution and a defect density distribution in a silicon wafer treated by the method for depositing oxygen on a silicon wafer according to the present invention (Example 4).

Claims (9)

[Claims] 1. An outward diffusion heat treatment step of heating a silicon wafer to outwardly diffuse oxygen contained in a surface layer, a low temperature heat treatment step of heating the silicon wafer at a low temperature of 300 to 600 ° C., and the silicon. Wafer 60
An oxygen precipitation heat treatment step of heating oxygen within a temperature range of 0 to 1150 ° C. to precipitate oxygen, and in the oxygen precipitation method of a silicon wafer in which oxygen is precipitated inside the silicon wafer, the low temperature heat treatment step A method for precipitating oxygen in a silicon wafer, which is performed in an atmosphere containing crystals or hydrogen. 2. The oxygen precipitation method for a silicon wafer according to claim 1, wherein hydrogen is added in the outward diffusion heat treatment step. 3. The method for depositing oxygen on a silicon wafer according to claim 1, wherein between the outward diffusion heat treatment step and the low temperature heat treatment step,
A method for precipitating oxygen on a silicon wafer, comprising a hydrogenation step of adding hydrogen within a temperature range of 300 to 1250 ° C. 4. The oxygen precipitation method for a silicon wafer according to claim 1, wherein hydrogen is added in the low temperature heat treatment step. 5. The method for depositing oxygen on a silicon wafer according to claim 2, wherein hydrogen is added only from the surface of the silicon wafer opposite to the element formation surface. Oxygen precipitation method. 6. The method for depositing oxygen on a silicon wafer according to claim 5, wherein hydrogen is added by ion-implanting hydrogen only to the surface of the silicon wafer opposite to the element formation surface. Oxygen precipitation method. 7. The method for precipitating oxygen of a silicon wafer according to claim 5, wherein the element formation surface of the silicon wafer is treated with hydrogen plasma while being covered with a protective film, so that hydrogen is formed only on the side opposite to the element formation surface. A method for precipitating oxygen in a silicon wafer, which comprises adding 8. The oxygen precipitation method for a silicon wafer according to claim 2, wherein deuterium or tritium is added instead of hydrogen. 9. The oxygen precipitation method for a silicon wafer according to claim 2, wherein helium is added instead of hydrogen.