JP2002184781A - Silicon wafer and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicon wafer which is most suitable as an integrated circuit of a semiconductor device having a controlled uniform boron concentration. SOLUTION: In the method for manufacturing a silicon wafer, the silicon wafer having boron doped therein is heat treated at a temperature of 1000 deg.C or more in an atmosphere of a mixture gas of hydrogen and diborane (B2H6) (1). It is desirable to set a mixture ratio of hydrogen in this atmosphere to diborane (B2H6) in a diborane (B2H6) mixture gas at 1% or more. In the silicon wafer obtained by the method (1) for manufacturing a silicon wafer, a difference in boron concentration between the outermost surface layer of the wafer and the central part thereof is set at 10% or less (2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method for manufacturing a silicon wafer used for forming an integrated circuit of a semiconductor device, and a silicon wafer manufactured therefrom.

[Detailed Description of the Invention]

2. Description of the Related Art A silicon single crystal used as an integrated circuit material for a semiconductor is mainly grown by the Czochralski method (hereinafter referred to as "CZ method"). The silicon wafer is cut into slices from the grown silicon single crystal and used for forming a highly integrated circuit for a semiconductor device.

In recent device processes, most of the causes of defects in highly integrated circuits are attributed to particles. In addition to the original particles, such as particles generated from the process apparatus alone or particles generated by performing an actual process, crystal defects introduced during the growth of a single crystal are also detected as particles. You.

Normally, in a wafer cut out of a silicon single crystal grown by the CZ method, several kinds of minute defects are formed in the plane, and these are crystal defects introduced during the growth of the single crystal. This is called a so-called Grown-in defect. Some of these Grown-in defects include COP
(Crystal Originated Particle), which is a defect related to a point defect (vacancy) and having a crystal defect based on an octahedral structure having a hollow inside.

[0005] Since this COP forms pits on the wafer surface by repeated cleaning after mirror polishing, COP
When the wafer in which P exists is observed with a surface inspection device, these pits are detected as particles. But C
OPs are clearly distinguished from the original particles because they have different generation factors and characteristics. In addition, COP
This causes not only deterioration of the gate film breakdown voltage characteristic of the MOS device, but also causes element isolation failure, which is a factor of deteriorating the electric characteristics of the device.

[0006] In particular, in recent years, with the rapid development of the integration density of semiconductor integrated circuit elements (devices),
Demands on silicon wafer quality are becoming more stringent, and there is a strong demand for reduction of Grown-in defects detected as particles. In order to respond to such demands, various proposals have been made on methods for reducing Grown-in defects in crystals.

[0007] For example, in Japanese Patent Application Laid-Open No.
A method has been proposed in which a single crystal wafer cut from a silicon single crystal grown by a method is heat-treated in a reducing atmosphere. In other words, according to this method, a wafer grown from a silicon single crystal grown at a growth rate of 0.6 mm / min or more by the CZ method and having a concentration of oxygen of 16 ppma or less and a high concentration of single-type COP is present. Against
By performing a high-temperature heat treatment in a hydrogen atmosphere or a mixed atmosphere of hydrogen and argon using a rapid heating / cooling device or the like, the COP on the wafer surface and the surface layer can be significantly reduced.

Japanese Patent Application Laid-Open No. Hei 10-98047 discloses a method in which the defect size is reduced by increasing the density of defects introduced into the crystal, and the reduction of crystal defects is promoted by a subsequent heat treatment. . Specifically, by doping nitrogen at a concentration of at least 1 × 10 ¹⁴ / cm ³ , the size distribution of Grown-in defects is advantageously shifted to miniaturization, and rare gas, oxygen, nitrogen, hydrogen, argon, or oxygen By performing a heat treatment of 1 hr or more at a temperature of 1000 ° C. in an atmosphere using a combination of
It is intended to reduce P.

It has been confirmed that any of the above-mentioned methods is effective for reducing the Grown-in defects in the crystal.

[0010]

SUMMARY OF THE INVENTION Silicon wafer P
As the type dopant, boron (B) is frequently used, and usually,
It is added in the range of 5 × 10 ¹⁴ / cm ³ to 2 × 10 ¹⁹ / cm ³ .
For a boron-doped wafer, its potential characteristics,
For example, it is necessary to control the boron concentration in order to ensure uniform resistance. As a method of controlling the boron concentration, there has been proposed a method of controlling the boron concentration of the surface layer of a silicon wafer containing boron based on the dependence of the out-diffusion of boron on a heat treatment (annealing) atmosphere (Japanese Patent Application Laid-Open No. 10-1998). No. 144697).

However, the proposed method has been developed to avoid the auto-doping phenomenon when forming an epitaxial layer on the wafer surface, and it has been proposed to use hydrogen in a hydrogen atmosphere or in a mixed atmosphere of hydrogen and argon. By performing heat treatment in a temperature range of 800 ° C. to 1300 ° C. in an atmosphere containing boron, boron is diffused outward from the wafer surface to reduce the boron concentration near the surface. Therefore, it is difficult to uniformly control the boron concentration when trying to homogenize the potential characteristics over the entire surface and all layers of the wafer, and this method cannot be adopted.

The above-described method for reducing the Grown-in defect is effective for reducing the COP, but does not consider the treatment of a silicon wafer containing boron. In other words, since the outward diffusion of boron depends on the heat treatment atmosphere, it is not possible to secure uniform wafer characteristics depending on the atmosphere used. Furthermore, according to the study of the present inventors, depending on the temperature conditions of the heat treatment, hydrogen or a hydrogen-containing atmosphere and an inert gas (argon) containing no hydrogen can be used.
It becomes clear that a change occurs in COP reduction and annihilation behavior.

The present invention has been made in view of the above-mentioned conventional problems. Even if a silicon wafer contains boron, the boron concentration can be controlled uniformly over the entire surface of the wafer. It is an object of the present invention to provide a method for manufacturing a silicon wafer and a silicon wafer capable of effectively reducing COP among -in defects.

[0014]

The gist of the present invention is the following (1) a method for manufacturing a silicon wafer and (2) a silicon wafer. (1) A method for producing a silicon wafer, wherein a silicon wafer doped with boron (B) is heat-treated at a temperature of 1000 ° C. or more in an atmosphere composed of a mixed gas of hydrogen and diborane (B ₂ H ₆ ). It is.

In the above-described method for manufacturing a silicon wafer, it is desirable that the mixing ratio of hydrogen and diborane in a mixed gas of diborane (B ₂ H ₆ ) constituting the atmosphere is 1% or more. (2) A silicon wafer obtained by the method for manufacturing a silicon wafer according to (1) above, wherein the difference between the boron concentration in the outermost layer of the wafer and the boron concentration in the center of the wafer is 10% or less of the boron concentration in the center of the wafer. A silicon wafer characterized by the following.

[0016]

DETAILED DESCRIPTION OF THE INVENTION In the method of the present invention, boron (B) is used.
Is heat-treated in a mixed gas atmosphere of hydrogen and diborane to prevent boron from diffusing outward from the wafer surface and prevent the boron concentration from lowering in the wafer surface layer. Is characterized by efficiently eliminating COP in the above. Hereinafter, the content of the present invention will be described step by step. First, the relationship between the COP reduction behavior and the heat treatment temperature will be described.

FIG. 1 shows that the initial concentration of boron is 1 × 10 ¹⁶ / cm ³
FIG. 9 is a diagram showing the results of measuring the number of COPs having a size of 0.083 μm or more existing in the depth direction of the wafer by performing a heat treatment on an 8 ″ φ silicon wafer at 1200 ° C. × 1 hr. Diborane mixed gas (B ₂ H ₆
10%), hydrogen gas, or argon gas. The number of COPs after the heat treatment was measured using a surface inspection device (trade name, Surfascan SP-1) manufactured by Tencor Co., Ltd., and polished in the depth direction of the wafer in increments of 5 μm. The number was measured.

As is apparent from FIG. 1, even when the heat treatment is performed in a mixed atmosphere of hydrogen and diborane, the COP can be reduced in the same manner as in the case where the heat treatment is performed in an atmosphere of hydrogen gas alone. Even in a heat treatment in an atmosphere, COP can be reduced almost in the same manner. Therefore, if the heat treatment was performed at a high temperature of 1200 ° C., no significant difference was observed in the COP reduction behavior due to the difference in the atmosphere gas.

However, if the heat treatment is performed at a low temperature, for example, 1100 ° C. or lower, the heat treatment performed in an atmosphere in which hydrogen is not mixed, such as an argon atmosphere, can reduce the COP more than the heat treatment performed in a hydrogen atmosphere. Becomes difficult.

FIG. 2 shows that the initial concentration of boron is 1 × 10 ¹⁶ / cm ³
FIG. 2 is a view showing the results of measuring the number of COPs having a size of 0.083 μm or more existing in the depth direction of the wafer by performing a heat treatment on an 8 ″ φ silicon wafer at 1100 ° C. × 1 Hr. The atmosphere of the heat treatment is hydrogen gas and diborane mixed gas (B ₂ H ₆ 10%), hydrogen gas or argon gas, and the number of COP after heat treatment is the same as above. Measured in the direction.

From the results shown in FIG. 2, even when the heat treatment is performed in a mixed atmosphere of hydrogen and diborane, the COP can be reduced in the same manner as in the case where the heat treatment is performed in an atmosphere containing only hydrogen gas. On the other hand, heat treatment in an argon gas atmosphere makes it difficult to reduce COP. That is,
Unlike the case of 1200 ℃ high temperature heat treatment, the processing temperature is 1000 ℃
When the temperature becomes as low as ~ 1100 ° C, C in an argon gas atmosphere
A remarkable difference in OP reduction behavior from that in an atmosphere of hydrogen alone or a mixed gas of hydrogen and diborane is observed.

From the results shown in FIGS. 1 and 2, it is predicted that the higher the heat treatment temperature or the longer the heat treatment time, the more desirable the COP is to be reduced.
The effective heat treatment conditions also differ depending on the target wafer. For example, in the case of a wafer manufactured from a crystal doped with nitrogen and having a reduced defect size (high-speed pulling speed: 2.0 mm / min or more) proposed in JP-A-10-98047, 1000 ° C. × It has been confirmed that the COP of the wafer surface layer can be eliminated even by heat treatment for 1 to 2 minutes. Therefore, in the method of the present invention, a heat treatment at a temperature of 1000 ° C. or more is targeted, and the treatment time is not particularly defined.

Normally, in the heat treatment in an argon gas atmosphere, boron atoms are not released from the wafer surface, but in the heat treatment in an atmosphere containing hydrogen, boron atoms are released into the atmosphere and the boron concentration on the wafer surface decreases. . It is presumed that this is because boron atoms on the wafer surface combine with hydrogen in the atmosphere and are mainly released into the atmosphere as B ₂ H ₆ . Therefore, as the heat treatment time becomes longer and the heat treatment temperature becomes higher, the boron release reaction is promoted, so that the boron concentration in the wafer surface layer decreases.

FIG. 3 shows that the initial concentration of boron is 1.4 × 10 ¹⁷ / cm
8 is a view showing the result of measuring the boron concentration profile in the depth direction of the wafer by heat-treating an 8 ″ φ silicon wafer at ³ ° C. at 1200 ° C. × 1 hr. As a heat treatment atmosphere, a mixed gas of hydrogen and diborane (B ₂ H ₆ 10%), hydrogen gas, or argon gas The boron concentration profile in the wafer search direction of 0 to 10 μm after the heat treatment is represented by SIMS (Secondary Ion Mass Spectroscop).
Measured in y).

As shown in FIG. 3, when the heat treatment is performed in an atmosphere of hydrogen gas alone, the boron concentration in the outermost layer of the wafer is reduced to about
Although it decreased by 90% or more, the boron concentration did not decrease in an argon gas atmosphere or a mixed atmosphere of hydrogen and diborane.

Next, when an atmosphere of a mixed gas of hydrogen and diborane is used, the concentration of diborane required to suppress the reaction of releasing boron from the wafer surface will be examined.

FIG. 4 shows that the initial concentration of boron is 1.4 × 10 ¹⁷ / cm
³ ) 8 "φ silicon wafer is heat-treated at 1200 ° C x 1 hr in a mixed gas atmosphere of hydrogen and diborane at each mixing ratio.
FIG. 5 is a diagram showing a result of measuring a profile of a boron concentration in a wafer depth direction. The diborane mixture ratio in the mixed gas atmosphere is set to three types of 0.1%, 1% and 10%, and the profile of the boron concentration in the wafer search direction is SIM.
S was measured.

As shown in FIG. 4, the diborane mixture ratio was 0.1
%, The boron concentration in the outermost layer of the wafer decreased by about 70% or more, but the diborane mixture ratio was 1%.
When the heat treatment was performed in an atmosphere of 10% and 10%, the boron concentration did not decrease.

As is clear from the results shown in FIGS. 3 and 4, when the heat treatment is performed in a mixed gas atmosphere of hydrogen and diborane, a compound of hydrogen and boron (mainly B ₂ H ₆ ) is actually contained in the atmosphere. Since it exists as a concentration, emission of boron atoms on the wafer surface is suppressed. At this time, the required diborane mixture ratio in the mixed gas atmosphere is set to 1%, and if a mixed gas atmosphere having a diborane mixture ratio higher than that is used, it is possible to prevent the boron concentration on the wafer surface from decreasing. .

In the silicon wafer of the present invention, the difference between the boron concentration in the outermost layer of the wafer and the boron concentration in the central portion of the wafer is suppressed to 10% or less, whereby the device characteristics can be further improved.

[0031]

According to the method for manufacturing a silicon wafer of the present invention, a wafer doped with boron (B) is subjected to a heat treatment in a mixed gas atmosphere of hydrogen and diborane.
Prevents the boron concentration from decreasing in the surface layer due to boron out-diffusion from the wafer surface, enables uniform control of the boron concentration over the entire wafer, and efficiently eliminates COP in the device active region of the wafer. Can be. This makes it possible to provide an optimal silicon wafer for an integrated circuit of a semiconductor device.

[Brief description of the drawings]

FIG. 1 8 ″ φ where the initial concentration of boron is 1 × 10 ¹⁶ / cm ³
Heat treatment of silicon wafer at 1200 ℃ × 1Hr, COP of 0.083μm or more existing in the depth direction of wafer
It is a figure showing the result of having measured the number.

FIG. 2 8 ″ φ where the initial concentration of boron is 1 × 10 ¹⁶ / cm ³
Heat treatment of silicon wafer at 1100 ℃ × 1Hr, COP of 0.083μm or more existing in the depth direction of wafer
It is a figure showing the result of having measured the number.

FIG. 3: 8 ″ φ in which the initial concentration of boron is 1 × 10 ¹⁶ / cm ³
FIG. 6 is a diagram showing the results of performing a heat treatment on a silicon wafer at 1200 ° C. × 1 Hr and measuring the boron concentration profile in the wafer depth direction.

FIG. 4: 8 ″ φ with an initial boron concentration of 1 × 10 ¹⁶ / cm ³
FIG. 4 is a diagram showing the results of performing a heat treatment on a silicon wafer at 1200 ° C. × 1 Hr in various hydrogen and diborane mixed gas atmospheres, and measuring the boron concentration profile in the wafer depth direction.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tatsumi Kusaba 2201 Kamida, Oita, Kihoku-gun, Kishima-gun, Saga Pref.

Claims (3)

[Claims] 1. A silicon wafer doped with boron (B) is heat-treated at a temperature of 1000 ° C. or more in an atmosphere composed of a mixed gas of hydrogen and diborane (B ₂ H ₆ ). Production method. 2. The method for producing a silicon wafer according to claim 1, wherein the mixing ratio of diborane (B ₂ H ₆ ) in the mixed gas constituting said atmosphere is 1% or more. 3. A silicon wafer obtained by the method according to claim 1, wherein the difference between the boron concentration in the outermost layer of the wafer and the boron concentration in the center of the wafer is 10% or less of the boron concentration in the center of the wafer. A silicon wafer, characterized in that: