JP6988737B2 - Manufacturing method of silicon wafer and silicon wafer - Google Patents

Description

The present invention relates to a method for manufacturing a silicon wafer and a silicon wafer.

Silicon wafers are widely used as semiconductor substrates for manufacturing various semiconductor devices such as RF (radio frequency) devices, MOS devices, DRAMs, and NAND flash memories. In the so-called device process of manufacturing a semiconductor device using a silicon wafer, various heat treatments such as oxidation treatment, nitriding treatment, plasma etching, and impurity diffusion treatment are performed.

Oxygen present in silicon crystals is usually electrically neutral, but when a silicon wafer undergoes a relatively low temperature heat treatment of less than about 600 ° C. (hereinafter referred to as low temperature heat treatment), several to a dozen oxygen atoms are present. Are known to aggregate to form oxygen clusters in silicon crystals. These oxygen clusters are donors that emit electrons and are called thermal donors (TDs). The thermal donor electrically returns to neutral when it receives a high temperature heat treatment of about 650 ° C. or higher, and such a high temperature heat treatment is called a donor killer heat treatment (donor killer annealing).

Along with the low temperature heat treatment in the device process, even if the silicon wafer is subjected to the donor killer heat treatment, the thermal donor is generated again during the device process, so that the carrier concentration of the silicon wafer changes. As a result, the resistivity of the silicon wafer may change before and after the low temperature heat treatment in the device process, and in some cases, the conductive type may be inverted. For example, when a silicon wafer is a p-type wafer having a very high resistance, it can be inverted into an n-type wafer depending on the amount of thermal donors produced.

Therefore, conventionally, silicon wafers that can suppress the generation of thermal donors even when used in a device process have been studied. If the substrate oxygen concentration of the silicon wafer is low, it is more difficult to generate a thermal donor than in the case of a high oxygen concentration. Therefore, if the influence of the thermal donor is a concern, a silicon wafer with a low oxygen concentration has been used so far. I came.

Further, the applicant of the present application proposes a technique capable of suppressing the generation of a thermal donor even in a silicon wafer having a relatively high oxygen concentration in Patent Document 1. In Patent Document 1, a silicon wafer having a carbon concentration of 5 × 10 ¹⁵ to 1 × 10 ¹⁷ atoms / cm ³ is subjected to high-temperature heat treatment to form a DZ (Denuded Zone) layer on the surface layer of the wafer, and after the heat treatment. A method for manufacturing a silicon wafer having a residual oxygen concentration in the wafer of 10 × 10 ¹⁷ atoms / cm ^{3 or more is disclosed.}

In Patent Document 1, a silicon wafer is manufactured by performing a heat treatment at 1100 ° C. or higher and a relatively long time so that a DZ layer can be formed on a silicon wafer which is a high resistance substrate and is carbon-doped. When the silicon wafer thus produced is subjected to the low temperature heat treatment of the device process, the generation of thermal donors can be suppressed.

International Publication No. 2004/008521

As described above, by using the technique disclosed in Patent Document 1, it is possible to suppress the generation of thermal donors due to the low temperature heat treatment of the device process. However, the heat treatment for forming the DZ layer requires a high temperature and a long time (disclosed as about 1 to 5 hours in Patent Document 1), so that the production cost is high. Further, in Patent Document 1, since carbon doping is indispensable, the characteristics (board characteristics) of the silicon wafer are limited.

Therefore, the present invention can apply a silicon wafer capable of suppressing the amount of thermal donors generated even when subjected to low-temperature heat treatment in a device process to various substrate characteristics, and manufactures the silicon wafer with excellent production cost. The purpose is to provide a method that can be done. Further, an object of the present invention is to provide a silicon wafer capable of suppressing the amount of thermal donors generated even when subjected to the above low temperature heat treatment.

As a result of diligent studies by the present inventors in order to solve the above problems, a silicon wafer is subjected to rapid thermal oxidation treatment (RTO: Rapid Thermal Oxidation), and the growth conditions and cooling conditions of the thermal oxide film at that time are controlled. Was conceived. It is presumed that supersaturated interstitial silicon is generated in the silicon crystals of the silicon wafer by the rapid heat treatment and rapid cooling accompanying the RTO. Then, the present inventor has found that the supersaturated interstitial silicon can suppress the formation of a thermal donor by binding with the interstitial oxygen in the silicon crystal. The present invention is based on the above findings, and its gist structure is as follows.

(1) The first step of heat-treating the silicon wafer while forming a thermal oxide film on the surface of the silicon wafer by rapid thermal oxidation treatment in an oxidizing atmosphere.
Following the first step, the second step of cooling the silicon wafer on which the thermal oxide film is formed under the oxidizing atmosphere, and the second step.
A method for manufacturing a silicon wafer, which comprises a first step and a third step of removing the thermal oxide film formed through the second step.

(2) The relationship between the growth rate X (nm / s) of the thermal oxide film in the first step and the cooling rate Y (° C./s) in the second step is the following formula [1]:.
Y> 7.5 × X ^-1.38・ ・ ・ [1]
The method for manufacturing a silicon wafer according to (1), wherein the first step and the second step are performed so as to satisfy the above.

(3) The holding temperature after the temperature rise in the heat treatment in the first step is set to 1150 ° C. or higher and the silicon melting point or lower.
The method for manufacturing a silicon wafer according to (2) above, wherein the cooling rate Y in the second step is 20 ° C./s or more.

(4) The oxygen concentration of the silicon wafer before the first step is 1.0 × 10 ^{17 to} 15.0 × 10 ¹⁷ ASTM / cm ³ (ASTM F-121, 1979). The method for manufacturing a silicon wafer according to any one of 3).

(5) The oxygen concentration of the silicon wafer is 1.0 × 10 ^{17 to} 15.0 × 10 ¹⁷ ASTM / cm ³ (ASTM F-121, 1979).
The amount of thermal donor generated after heat-treating the silicon wafer at 350 ° C. for 32 hours in a nitrogen atmosphere is 8.0 × 10 ¹² cm ^-3 or more and 1.5 × 10 ¹³ cm ^-3 or less. A characteristic silicon wafer.

According to the present invention, a silicon wafer capable of suppressing the amount of thermal donors generated even when subjected to low-temperature heat treatment in a device process can be applied to various substrate characteristics and is manufactured with excellent production cost. Can provide a method that can be done. Further, according to the present invention, it is possible to provide a silicon wafer capable of suppressing the amount of thermal donors generated even when subjected to the above low temperature heat treatment.

It is a schematic sectional drawing explaining the manufacturing process of the manufacturing method according to one Embodiment of this invention, and the silicon wafer obtained by it. It is a graph which shows the thermal donor generation amount of each sample in an Example. It is a graph which shows the relationship between the growth rate X and the cooling rate Y of a thermal oxide film in an Example. It is a graph which shows the relationship between the interstitial silicon concentration of each sample in an Example, and the amount of thermal donor generation.

(Manufacturing method of silicon wafer)
The method for manufacturing a silicon wafer according to an embodiment of the present invention includes a first step of performing a donor killer heat treatment on the silicon wafer while forming a thermal oxide film on the surface of the silicon wafer by rapid thermal oxidation treatment in an oxidizing atmosphere. Following the first step, the second step of cooling the silicon wafer on which the thermal oxide film is formed in the oxidizing atmosphere, and the heat formed through the first step and the second step. It comprises a third step of removing the oxide film. Then, in the manufacturing method of the present invention, in order to control the growth rate of the thermal oxide film formed by the first step and the cooling rate of the cooling in the second step, the silicon wafer after the third step is heat-treated. It is possible to suppress the amount of thermal donors generated when the above is applied. Hereinafter, the details of each step of the first to third steps will be sequentially described with reference to steps A to D of FIG. The silicon wafers 10A to 10D, the thermal oxide film 20, the thermal donor TD, and the interstitial silicon Si _I in FIG. 1 are schematically shown for convenience of explanation. Therefore, these illustrations do not imply actual size ratios and concentrations.

<First step>
The first step will be described with reference to step A and step B in FIG. In the first step, the thermal oxide film 20 is formed on the surface of the silicon wafer 10A by a rapid thermal oxidation treatment (hereinafter, “RTO”) in an oxidizing atmosphere. A thermal oxide film 20 is formed on the silicon wafer 10A in step A, and becomes the silicon wafer 10B in step B. As will be described later, the thermal donor TD present in the silicon crystal of the silicon wafer 10A is heat-treated by the donor killer by the RTO in this step.

<< RTO >>
RTO can be performed by rapid heat treatment (RTA: Rapid Thermal Annealing) in an oxidizing atmosphere. The RTO can be performed using a general rapid heat treatment apparatus, and for example, Helious III manufactured by Mattoson and RTA-12000 manufactured by Advanced Riko Co., Ltd. are known. The oxidizing atmosphere for performing RTO is not particularly limited as long as a desired thermal oxide film can be obtained, but for example, an oxidizing atmosphere consisting only of oxygen can be used, and oxygen and an inert gas (argon and nitrogen) can be used. Etc.) may be used as a mixed gas atmosphere. The elevating temperature rate when performing RTO and the holding time after raising the temperature can be controlled by a rapid heat treatment apparatus for performing RTO.

<< Silicon wafer 10A before RTO >>
As the silicon wafer 10A, a single crystal silicon ingot sliced with a wire saw or the like can be used. The conductive type of the silicon wafer applicable to the present invention, its resistivity, and the oxygen concentration are not limited in any way. It can be applied to both p-type and n-type, and the resistivity is arbitrary from several mΩ · cm to several thousand Ω · cm. The resistivity referred to here is the resistivity after the donor killer treatment, and the resistivity is measured according to JIS H 0602: 1995 described later. The oxygen concentration can also be 1.0 × 10 ^{17 to} 15.0 × 10 ¹⁷ atoms / cm ³ (ASTM F-121, 1979, hereinafter the same standard for oxygen concentration is referred to). Since thermal donors are more likely to be generated as the oxygen concentration is higher, it is preferable to apply the present invention to a silicon wafer ^{having an oxygen concentration of 8.0 × 10 17} atoms / cm ^{3 or more, and further, 11.0 × 10} It is preferable to apply the present invention to a silicon wafer of ¹⁷ atoms / cm ^{3 or more.}

The method of the present invention is applied to a silicon wafer obtained from a single crystal silicon ingot grown by the Czochralski method (CZ method) or the magnetic field type MCZ method (Magnetic field applied Czochralski). Since there is almost no oxygen in the crystals of the single crystal silicon ingot grown by the FZ method (oxygen concentration ^{less than 1.0 × 10 17} atoms / cm ³ ), the thermal donor is not a problem.

A thermal donor TD is present in the crystal of the single crystal silicon ingot obtained by the CZ method or the MCZ method because the oxygen atom derived from the quartz crucible is dissolved. On the other hand, the RTO involves a high temperature heat treatment of 650 ° C. or higher, which is necessary for the donor killer heat treatment. Therefore, the heat treatment associated with the formation of the thermal oxide film 20 in this step also serves as the donor killer heat treatment of the thermal donor TD in the silicon crystal. Therefore, in the silicon wafer 10B that has undergone temperature rise and high temperature holding, the thermal donor TD existing in the silicon crystal of the silicon wafer 10A changes to a form that does not emit electrons such as an oxygen monomer.

<< Thermal Oxide Film >>
In the first step, the silicon crystals on the surface of the silicon wafer 10A are oxidized to form silicon oxide, whereby the thermal oxide film 20 is formed. The film thickness of the formed thermal oxide film 20 is usually about several nm to several tens of nm, although it depends on the rate of temperature rise, the holding temperature after the temperature rise and the holding time thereof. The holding temperature and the holding time after the temperature rise are dominant with respect to the growth rate and the film thickness of the thermal oxide film 20.

<Second step>
The second step will be described with reference to step B and step C in FIG. In the second step, following the first step, the silicon wafer 10B on which the thermal oxide film 20 is formed is cooled in an oxidizing atmosphere to obtain the silicon wafer 10C. The cooling rate at the time of cooling in the second step can be controlled by a rapid heat treatment apparatus for performing RTO, and is also called rapid cooling.

Since the rapid cooling is performed in an oxidizing atmosphere following the first step, the film thickness of the thermal oxide film 20 can be slightly increased. However, as described above, the growth of the thermal oxide film at the holding temperature and holding time after the temperature rise in the first step is dominant in the thickness of the thermal oxide film 20, and the thermal oxide film 20 that grows in the second step alone The film thickness is considered to be small.

<Third step>
The third step will be described with reference to step C and step D in FIG. In the third step, the thermal oxide film 20 on the surface of the silicon wafer 10C formed through the first step and the second step is removed to obtain a silicon wafer 10D. The silicon wafer 10D can be obtained by taking out the silicon wafer 10C from the rapid heat treatment apparatus and removing the thermal oxide film 20 by a general etching process using hydrofluoric acid (HF) or the like.

Here, in the manufacturing method of the present invention, in order to suppress the amount of thermal donors generated when the silicon wafer 10D after the third step is heat-treated, the thermal oxide film is formed by the first step. And the cooling in the second step are controlled respectively.

Although not bound by theory, the technical significance of the first step and the second step (steps A to C in FIG. 1) will be described together with the effects of the present invention. The present inventors consider the reason why the action and effect of the present invention can be obtained through experiments in which a silicon wafer is subjected to rapid thermal oxidation treatment (RTO) under various conditions as follows.

First, the thermal oxide film 20 begins to be formed on the surface of the silicon wafer 10A with rapid heating in an oxidizing atmosphere. At this time, the higher the growth rate of the thermal oxide film 20, the more interstitial silicon Si _I is injected from the thermal oxide film 20 into the silicon crystals in the silicon wafer 10B. The injected interstitial silicon Si _I diffuses outward from the front and back surfaces of the silicon wafer 10C to the thermal oxide film 20 as the temperature drops, but the larger the cooling rate, the smaller the diffusion amount of the _{interstitial silicon Si I.} Therefore, when rapidly cooled, the injected interstitial silicon Si _I remains in the crystal. In this way, the residual interstitial silicon Si _I is supersaturated in the silicon crystal of the silicon wafer 10D. In the silicon wafer 10D, _{even if the low temperature heat treatment in which the thermal donor is formed by the interstitial silicon Si I} is performed, the thermal donor is less likely to be generated due to the interaction with the interstitial oxygen and the like.

As described above, the silicon wafer 10D obtained according to the manufacturing method of the present invention can suppress the amount of thermal donors generated even if the silicon wafer 10D is subjected to the low temperature heat treatment in the device process.

Further, in the manufacturing method of the present invention, it is possible to suppress the amount of thermal donors generated without restrictions on the substrate characteristics such as oxygen concentration and carbon concentration of the silicon wafer 10A, or with almost no restrictions. Therefore, it is not necessary to reduce the oxygen concentration of the silicon wafer in order to control the resistivity, and even if the silicon wafer is reduced in oxygen, the degree can be significantly relaxed as compared with the prior art. Further, since the degree of hypoxia can be alleviated as described above, it is also advantageous in that it is possible to prevent a decrease in the wafer strength of the silicon wafer. In addition, since the oxygen concentration of the silicon wafer can be made high in the present invention, it is possible to generate an oxygen precipitate (BMD) in the silicon crystal. That is, the manufacturing method of the present invention is also advantageous in that a gettering ability by BMD generation can be imparted to a silicon wafer in which the amount of thermal donors generated is suppressed.

Further, since the production method of the present invention is rapid heating / cooling by RTO, heat treatment can be performed in an extremely short time as compared with the DZ treatment by the technique of Patent Document 1 described above, which is advantageous in terms of production cost. be.

Here, the relationship between the growth rate X (nm / s) of the thermal oxide film 20 in the first step and the cooling rate Y (° C./s) in the second step is the following formula [1] :.
Y> 7.5 × X ^-1.38・ ・ ・ [1]
It is preferable to carry out the first step and the second step so as to satisfy the above. By doing so, the present inventors have experimentally confirmed that the action and effect of the present invention can be obtained more reliably. When the growth rate X and the cooling rate Y satisfy the above formula [1], the interstitial silicon Si _I is injected during the thermal oxide film growth (first step) and the interstitial silicon during rapid cooling (second step). It is presumed that the outward diffusion of Si _{I can be controlled appropriately.}

Further, in order to obtain the growth rate X, it is preferable that the holding temperature after the temperature rise in the heat treatment in the first step is 1150 ° C. or higher and the silicon melting point or lower. In this case, _{in order to appropriately control the outward diffusion of the interstitial silicon Si I} , it is preferable that the cooling rate Y in the second step is 20 ° C./s or more. Although the melting point of silicon depends on the dopant concentration and the like, the melting point of silicon element is about 1410 ° C. under normal temperature and pressure.

Although typical embodiments of the manufacturing method according to the present invention have been described above, the present invention is not limited to these embodiments. Next, a silicon wafer according to an embodiment of the present invention will be described. The description of the contents overlapping with the embodiment of the manufacturing method will be omitted.

(Silicon wafer)
See step D in FIG. A silicon wafer 10D according to an embodiment of the present invention has a silicon wafer having an oxygen concentration of 1.0 × 10 ^{17 to} 15.0 × 10 ¹⁷ atoms / cm ³ (ASTM F-121, 1979). The amount of thermal donor generated after heat treatment at 350 ° C. for 32 hours in a nitrogen atmosphere is 8.0 × 10 ¹² cm ^-3 or more and 1.5 × 10 ¹³ cm ^-3 or less. A silicon wafer having a thermal donor generation amount at the above level can be realized for the first time by the above-mentioned method for manufacturing a silicon wafer of the present invention.

-The amount of thermal donors generated-
The amount of thermal donor generated in the present specification shall be quantified according to the following procedures (i) to (iv).

(I) First, the resistivity of the silicon wafer after the donor killer heat treatment is measured according to the "resistivity measuring method of silicon single crystal and silicon wafer by the four-probe method" specified in JIS H 0602: 1995. .. If a thermal oxide film is formed, the thermal oxide film is removed by etching or the like prior to the measurement. If the donor killer treatment has already been performed and then the heat treatment is not performed under the condition that a thermal donor is generated as in the first step in the manufacturing method of the present invention, it is necessary to perform the donor killer heat treatment again. No.

(Ii) Next, the silicon wafer whose resistivity has been measured is heat-treated in a nitrogen atmosphere at 350 ° C. for 32 hours to generate a thermal donor (hereinafter referred to as thermal donor generation heat treatment). This thermal donor generation heat treatment corresponds to a heat treatment simulating a relatively long-time low-temperature heat treatment in the device process.

(Iii) The resistivity of the silicon wafer after the thermal donor generation heat treatment is measured according to JIS H 0602: 1995 in the same manner as in (i) above.

(Iv) Based on the resistivity measured by (i) and (iii) above, the carrier concentration before and after the thermal donor generation heat treatment is obtained from the Irvine curve, and the difference in carrier concentration is the carrier generation amount due to the thermal donor (hereinafter). , Thermal donor generation amount).

Hereinafter, the method for manufacturing a silicon wafer of the present invention and the limitation of the silicon wafer of the present invention are not intended, but further specific embodiments of the silicon wafer applicable to the present invention will be described.

The plane orientation of the silicon wafer is arbitrary, and a wafer having a (100) plane may be used, or a wafer having a (110) plane may be used.

Further, the silicon wafer may be doped with a dopant such as boron (B), phosphorus (P), arsenic (As), antimony (Sb), and carbon (C) or nitrogen (N) in order to obtain desired characteristics. ) Etc. may be doped.

The diameter of the silicon wafer is not limited in any way. The present invention can be applied to a silicon wafer having a general diameter of 300 mm or 200 mm. Of course, the present invention can be applied to a silicon wafer having a diameter larger than 300 mm and a silicon wafer having a diameter smaller than 300 mm.

The term "silicon wafer" as used herein refers to a so-called "bulk" silicon wafer in which another layer such as an epitaxial layer or an insulating film made of silicon oxide is not formed on the surface. However, a natural oxide film formed with a film thickness of about several Å may be formed. Further, another layer such as an epitaxial layer may be separately formed on the silicon wafer obtained by the present invention to produce an epitaxial silicon wafer, or the wafer may be used as a support substrate or a substrate for an active layer of a bonded wafer. An SOI (Silicon on Insulator) wafer may be manufactured. The "bulk" silicon wafer that serves as the base substrate for such a wafer is the silicon wafer herein.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

Prior to the explanation of the sample preparation conditions, the measurement method in this example will be described.

-Film thickness of thermal oxide film-
Using a spectroscopic ellipsometer, the film thickness of the thermal oxide film on the surface of the silicon wafer after RTO was measured.

-Growth rate of thermal oxide film-
Since the growth of the thermal oxide film is dominant during the holding after raising the temperature to the maximum temperature at the time of RTO, thermal oxidation is performed based on the film thickness of the thermal oxide film and the holding time after the temperature rise at the time of RTO. The growth rate of the membrane was determined. The time during temperature rise until the holding temperature after temperature rise in rapid heating and the cooling time during rapid cooling are not used in calculating the growth rate of the thermal oxide film. The rate of temperature rise during RTO, the holding time after reaching the maximum temperature, and the cooling rate were controlled by a rapid heating / cooling device.

-The amount of thermal donors generated-
According to the above-mentioned procedures (i) to (iv), the amount of thermal donor generated after heat treatment at 350 ° C. for 32 hours under a nitrogen atmosphere was determined.

<Sample 1>
CZ method for P-type silicon single crystal ingot (resistivity after donor killer treatment: 10 Ω · cm) with a diameter of 300 mm, a plane orientation (100), and an oxygen concentration of 11 × 10 ¹⁷ atoms / cm ^{3 (ASTM F-121, 1979).} Raised by. By slicing the silicon single crystal ingot, a silicon wafer before RTO was produced.

Using the above-mentioned rapid heating / rapid cooling device, the obtained silicon wafer before RTO is subjected to RTO by rapid heating treatment and rapid cooling treatment that also serves as a donor killer heat treatment in an oxidizing atmosphere consisting of oxygen to form a thermal oxide film. Formed. The holding temperature after raising the temperature in the rapid heat treatment is 800 ° C., and the holding time is 240 seconds. The cooling rate Y was set to 50 ° C./sec.

The silicon wafer after RTO was taken out from the rapid heating / rapid cooling device, and the film thickness of the formed thermal oxide film was measured. At the same time, the growth rate X (nm / s) of the thermal oxide film was determined.

Then, the surface of the silicon wafer was etched with hydrofluoric acid (HF) to remove the thermal oxide film.

The silicon wafer after removing the oxide film was heat-treated at 350 ° C. for 32 hours in a nitrogen atmosphere, and the amount of thermal donors generated by the heat treatment was determined.

Table 1 shows the holding temperature by RTO, the holding time, the growth rate X of the thermal oxide film, and the cooling rate Y. Further, the graph of FIG. 2 shows the amount of thermal donor generated in sample 1.

<Samples 2 to 19>
Samples 2 to 19 were prepared in the same manner as in Sample 1 except that the holding temperature and holding time after raising the temperature by RTO and the cooling rate Y were as shown in Table 1. Further, the growth rate X of the thermal oxide film and the amount of thermal donor generated were determined in the same manner as in Sample 1. The graph of FIG. 2 shows the amount of thermal donors generated in Samples 2 to 19.

<Sample 20>
Using the same silicon wafer before RTO as in sample 1, this was introduced into a vertical furnace having an oxidizing atmosphere, and a donor killer heat treatment was performed at 650 ° C. for 30 minutes. After removing the formed oxide film in the same manner as in Sample 1, heat treatment was performed at 350 ° C. for 32 hours in a nitrogen atmosphere, and the amount of thermal donors generated by the heat treatment was determined. The graph of FIG. 2 shows the amount of thermal donor generated in the sample 20.

(Evaluation results and consideration)
It was confirmed from the graph of FIG. 2 that the amount of thermal donors generated in the samples 1 to 19 that had passed through the RTO was divided into a large level and a small level as compared with the amount of the sample 20 generated in the sample 20 corresponding to the conventional example by the heat treatment of the vertical furnace. To. Of these, the level at which the amount of thermal donors generated is small is about half that of the level at which the amount of thermal donors is large.

FIG. 3 shows a graph arranged by the growth rate X and the cooling rate Y of the thermal oxide film at the time of RTO according to the following criteria considering the amount of thermal donors generated, which corresponds to the amount of thermal donors generated less than that of sample 20.
◯: Thermal donor generation amount is 1.5 × 10 ¹³ cm ^-3 or less ×: Thermal donor generation amount is 1.5 × 10 ¹³ cm ^{-3 or} more

From the graph of FIG. 3, it can be seen that when the growth rate X of the thermal oxide film is fast and the cooling rate Y is fast, the amount of thermal donor generated is 1.5 × 10 ¹³ cm ^{-3 or less.} The curve equation Y = 7.5 × X ^{−1.38 in} FIG. 3 is a boundary line that separates the symbol ○ and the symbol × in FIG. That is, by performing RTO so that the growth rate X and the cooling rate Y ^{satisfy Y> 7.5 × X -1.38} , it is possible to surely suppress the amount of thermal donors generated after the subsequent heat treatment. Was confirmed. It was also confirmed that the amount of thermal donors generated after the heat treatment after RTO can be suppressed by controlling the growth rate X and the cooling rate Y of the thermal oxide film at the time of RTO, respectively.

(Calculation and consideration of interstitial silicon concentration)
Since it is difficult to directly measure the interstitial silicon concentration, the interstitial silicon concentration remaining in the above sample was calculated as follows. Specifically, for each of the above samples 1 to 6, 8, 13, 16 and 17, the silicon wafer is obtained by solving the diffusion equation in the thickness direction of the silicon wafer from the start of temperature rise to the cooling process in the RTO. The interstitial silicon concentration in the central part was determined. Steady values at arbitrary temperature and oxide film growth rate (Scott T. Dunham, J. Appl. Phys., 71 (1992) 685) were used as the boundary conditions for the interstitial silicon concentration on the front and back surfaces of the wafer. FIG. 4 shows the interstitial silicon concentrations of the samples 1 to 6, 8, 13, 16 and 17, and the amount of thermal donors produced after heat-treating these samples at 350 ° C. for 32 hours under a nitrogen atmosphere. Shows the relationship between.

From the graph of FIG. 4, the amount of thermal donors formed increases depending ^{on the interstitial silicon concentration up to 10 11} cm ^-3. On the other hand, ^{it is confirmed that when the interstitial silicon concentration exceeds 10 12} cm ^-3 , the amount of thermal donor generated decreases sharply. Therefore, based on the above calculation results, the heat treatment after RTO is performed by supersaturating the interstitial silicon concentration in the central portion of the silicon wafer in the thickness direction to 1 × 10 ¹² cm ^-3 or more, and further to 1 × 10 ¹³ cm ^{-3 or more.} It can be concluded that the amount of thermal donors generated can be suppressed.

According to the present invention, a silicon wafer capable of suppressing the amount of thermal donors generated even when subjected to low-temperature heat treatment in a device process can be applied to various substrate characteristics and is manufactured with excellent production cost. Can provide a method that can be done. Further, according to the present invention, it is possible to provide a silicon wafer capable of suppressing the amount of thermal donors generated even when subjected to the above low temperature heat treatment.

10A Silicon Wafer 10B Silicon Wafer 10C Silicon Wafer 10D Silicon Wafer 20 Thermal Oxide Film TD Thermal Donor Si _I Interstitial Silicon

Claims (3)

The first step of heat-treating the silicon wafer while forming a thermal oxide film on the surface of the silicon wafer by rapid thermal oxidation treatment in an oxidizing atmosphere.
Following the first step, the second step of cooling the silicon wafer on which the thermal oxide film is formed under the oxidizing atmosphere, and the second step.
A third step of removing the first step and the thermal oxide film formed through the second step, only including,
The first step is based on the relationship between the growth rate X (nm / s) of the thermal oxide film in the first step, the cooling rate Y (° C./s) in the second step, and the amount of thermal donor generated. In, the growth rate X (nm / s) of the thermal oxide film is controlled, and the cooling rate Y (° C./s) is controlled in the second step.
The relationship between the controlled growth rate X (nm / s) of the thermal oxide film in the first step and the controlled cooling rate Y (° C./s) in the second step is the following equation [1] :.
Y> 7.5 × X ^{-1. 3 8} ・ ・ ・ [1]
A method for manufacturing a silicon wafer, which is characterized by satisfying. The holding temperature after the temperature rise in the heat treatment in the first step is set to 1150 ° C. or higher and the silicon melting point or lower.
The method for manufacturing a silicon wafer according to claim 1 , wherein the cooling rate Y in the second step is 20 ° C./s or more. The invention according to claim 1 or 2 , wherein the oxygen concentration of the silicon wafer before the first step is 1.0 × 10 ^{17 to} 15.0 × 10 ¹⁷ ASTM / cm ³ (ASTM F-121, 1979). Manufacturing method of silicon wafer.

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