JPH08274104A - Semiconductor substrate and its manufacture - Google Patents

Abstract

PURPOSE: To reduce deterioration of mechanical strength and failed devices by decreasing oxygen deposit. CONSTITUTION: In a method for manufacturing a semiconductor substrate where an area near the surface of the semiconductor is made flawless, a process for introducing the semiconductor substrate into a reducing atmosphere, inert gas, or mixed gas, a process for increasing the temperature of the reducing atmosphere, inert gas, or the mixed gas from 700 to 900 deg.C within 60 minutes, and a process for performing heat treatment at least at a temperature of 1,100 deg.C for 30 minutes are provided, thus reducing the occurrence of dislocation in the semiconductor substrate due to distortion and the stress caused by high- temperature heat treatment.

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 a method for manufacturing the same, and more particularly, by controlling oxygen precipitates formed on the semiconductor substrate, it is possible to reduce device defects and improve the manufacturing yield. And a method for manufacturing the same.

[0002]

2. Description of the Related Art When manufacturing a semiconductor substrate, in order to improve the quality, a high purity and defect-free material is required. However, metal impurities such as iron and copper may be mixed into the semiconductor substrate during the manufacturing process of the semiconductor device. Due to this mixture, a device defect occurs and the manufacturing yield decreases, so it is necessary to remove metal impurities. As a method for removing the metal impurities from the vicinity of the surface of the semiconductor substrate, an internal gettering method (Intrinsic Gette
ring: hereinafter referred to as IG method) is known. This IG
The method uses oxygen precipitates (Bulk Micro Defect: BMD) such as precipitation of interstitial oxygen existing in the silicon semiconductor substrate, and attracts metal impurities existing near the surface of the semiconductor substrate by this BMD. , A method of removing metal impurities near the surface.

Generally, in order to apply a semiconductor substrate that has been subjected to the above-mentioned IG processing (hereinafter referred to as an IG substrate) to a MOS device or the like, the vicinity of the surface is subjected to a defect-free treatment (Denuded Zon).
e treatment: hereinafter referred to as DZ treatment) is used. This DZ treatment removes oxygen in the vicinity of the surface by outward diffusion of oxygen by high temperature treatment in an oxidizing atmosphere.

However, since this DZ treatment is performed in an oxidizing atmosphere and at a high temperature (about 1200 ° C.), the oxygen concentration near the surface cannot be reduced to about 4 × 10 ¹⁷ [atoms / cm ³ ] or less. . Therefore, oxygen remains near the surface, and it is difficult to achieve perfect defect-free.

Therefore, a method is known in which a DZ process is performed by performing a high temperature heat treatment in a reducing atmosphere such as hydrogen or an inert gas atmosphere such as Ar. In this method, the oxygen concentration near the substrate surface is low due to the non-oxidizing atmosphere (the oxygen concentration on the surface is about 1 × 10 ¹⁷ [atoms / c]
m ³ ] or less). Therefore, it is possible to perform the defect-free treatment of the surface layer of the substrate, which is better than the DZ treatment in the oxidizing atmosphere, by the high temperature heat treatment without forming the oxide film.

[0006]

However, when high-temperature heat treatment is performed by the conventional DZ treatment with a reducing atmosphere and an inert gas, oxygen precipitates are generated by the reaction of Si + 2O −> SiO ₂ . The generated oxygen precipitate expands in volume about twice as much as before the reaction. Therefore, when an oxygen precipitate having a certain density in the crystal is generated, the volume expansion of the oxide precipitate causes the entire area to expand. This expansion depends on the amount of oxygen precipitates contained. That is, as shown in FIG.
The volume expansion amount is different depending on the volume expansion amount in the region from the surface layer to 10 [μm] and the content of the oxygen precipitate 3 in the region from the surface layer 10 [μm] to 60 [μm]. Due to the difference in the volume expansion amount, the semiconductor substrate is distorted, and the stress of the high temperature heat treatment causes dislocations, resulting in a decrease in the yield due to the occurrence of device defects.

Further, the lower end of the device active area (surface layer 2 μm
To a depth of 10 μm), a small amount of residual oxygen precipitates may be a cause of device failure such as junction leak failure.

The present invention has been made in view of the above circumstances. An object of the present invention is to reduce oxygen precipitates to reduce deterioration of mechanical strength and to reduce device defects. And to provide a manufacturing method thereof.

[0009]

In order to achieve the above-mentioned object, a feature of the first invention is that in a method for manufacturing a semiconductor substrate in which the vicinity of the surface of the semiconductor substrate is made defect-free, a reducing atmosphere, an inert gas and , Or 110 in a mixed gas of these
When performing heat treatment for 30 minutes or longer at a temperature of 0 ° C. or higher, 70
It is characterized in that the passage time of the temperature rising process from 0 ° C. to 900 ° C. is within 60 minutes.

Here, preferably 700 to 900 ° C.
Generation of oxygen precipitates can be further reduced by setting the passage time of the temperature rising process to 40 minutes or less.

A second aspect of the present invention is a method of manufacturing a semiconductor substrate, which makes the vicinity of the surface of the semiconductor substrate defect-free, wherein the semiconductor substrate is placed in a reducing atmosphere, an inert gas, or a mixed gas thereof. Introducing step in gas to be introduced, temperature raising step of raising the reducing atmosphere, inert gas, or a mixed gas of these gases within a period of 60 minutes from 700 ° C to 900 ° C, and a temperature of 1100 ° C or higher. In 3
And a heat treatment step of performing heat treatment for 0 minutes or more.

Here, it is preferable to use hydrogen for the reducing atmosphere because the generation of oxygen precipitates can be reduced and the distortion of the semiconductor substrate can be suppressed.

Further, the use of argon as the inert gas is preferable in that the generation of oxygen precipitates can be reduced and the distortion of the semiconductor substrate can be suppressed. Further, the oxygen concentration of the semiconductor substrate is 12 × 10 ¹⁷ [atoms / cm ³ ] to 18 × 10 ¹⁷ [atoms / cm ³ ], which reduces the generation of oxygen precipitates and suppresses the distortion of the semiconductor substrate. It is preferable in that it can be obtained.

The third aspect of the present invention is that the surface layer 10
The density of oxygen precipitates from [μm] to 60 [μm] is 5 × 10 ^6.
A semiconductor substrate having a size of [cm ⁻³ ] or more and 5 × 10 ⁹ [cm ⁻³ ] or less is used.

[0015]

According to the first and second aspects of the present invention, the temperature range from 700 ° C. to 9 °
Make the passage time of the temperature rising process to 00 ° C within 60 minutes 11
By performing the heat treatment at 00 ° C. or higher, the time in the temperature region where the oxygen precipitates are likely to grow is shortened, whereby the density of the oxygen precipitates can be reduced.

According to the third invention, the surface layer 10 [μ
The density of oxygen precipitates in the depth from m] to 60 [μm] is 5 ×
It is not less than 10 ⁶ [cm ⁻³ ] and not more than 5 × 10 ⁹ [cm ⁻³ ]. As a result, the surface layer 1 can be obtained without impairing the gettering ability.
DZ layer up to 0 [μm] and surface layer 10 [μm] to 60 [μm]
It is possible to suppress the amount of strain due to the difference in the expansion amount of each layer due to the difference in the density of oxygen precipitates of the layers up to [m] below a certain limit, and to prevent the occurrence of dislocation due to stress during the subsequent high temperature heat treatment.

[0017]

Embodiments of a semiconductor substrate and a method of manufacturing the same according to the present invention will be described with reference to the drawings.

Example 1 In this example, a CZ wafer (N type (10
0), oxygen density [Oi] = 16 × 10 ¹⁷ [atoms / cm ³ ], 150mmφ,
The specific resistance is 1 to 60 Ωcm). This CZ wafer was placed on the top of the boat and placed in an N ₂ atmosphere (Ar,
Ne, Kr, Xe may be used) 700 ° C (650 ° C to 9
It was introduced into the furnace at 00 ° C). At that time, it took 10 minutes until the introduction of the board into the furnace was completed. After that, it took 15 minutes to replace with hydrogen.

Next, the temperature rising time from 700 ° C. to 900 ° C. is used as a parameter, and its value is 10 minutes, 15 minutes,
It was set to 20 minutes, 30 minutes, 35 minutes, and 40 minutes. Then, the temperature was raised to 1200 ° C. (1100 ° C. to 1400 ° C. may be used) under the same conditions, and heat treatment was performed for 1 hour. Under such conditions, the oxygen precipitates in the surface layer 10 [μm] and the oxygen precipitate density in the surface layer 10 [μm] to 60 [μm] were evaluated by an infrared scattering tomograph (IR tomograph). The evaluation result is shown in FIG. Figure 2 shows the horizontal axis from 700 ° C to 9
The total time at 00 ° C. (hydrogen replacement time 15 minutes + temperature rising time) and the horizontal axis show the BMD density.

As shown in the figure, from the surface layer 10 [μm] to 60
At [μm], the total time from 700 ℃ to 900 ℃ is 60
It can be seen that if it is less than or equal to minutes, it is within 5 × 10 ⁹ [cm ⁻³ ]. Here, if the lower limit value is set to 5 × 10 ⁶ [cm ⁻³ ] or less, the gettering ability is reduced, so 5 × 10 ⁶ [cm
^-3 ] Need to be above. The density of oxygen precipitates in the surface layer 10 [μm] was 1.8 × 10 ⁶ [cm ⁻³ ] at a total time of 60 minutes from 700 ° C. to 900 ° C.

As described above, in this embodiment, the oxygen precipitate density in the surface layer 10 [μm] and the oxygen precipitate density in the surface layer 10 [μm] to 60 [μm] were changed by the total time from 700 ° C. to 900 ° C. It was found that the oxygen precipitate density increased as the total time changed. Therefore, if the total time from 700 ° C. to 900 ° C. is 60 minutes or less (more preferably 40 minutes or less), the density of oxygen precipitates in the surface layer 10 [μm] is set to 2 × 10 ⁶ [cm ⁻³ ] or less. I was able to.

As described above, in this embodiment, the growth of the oxygen precipitates is suppressed by shortening the total time from 700 ° C. to 900 ° C. at which the oxygen precipitates are most likely to grow. ] It is possible to reduce the difference between the volume expansion amount in the region up to [] and the volume expansion amount in the region from the surface layer 10 [μm] to 60 [μm].

Embodiment 2 Next, in this embodiment, a CZ wafer is used as a semiconductor substrate similarly to the embodiment 1, and the CZ wafer is placed on the top of the boat and placed in an N ₂ atmosphere (Ar, Ne, Kr, The furnace was introduced at 700 ° C. (650 ° C. to 900 ° C.). At that time, it took 10 minutes until the introduction of the board into the furnace was completed.

Next, the time required for hydrogen substitution is used as a parameter, and its value is 5 minutes, 10 minutes, 20 minutes, 3
It was set to 0 minutes, 40 minutes, and 60 minutes. After that, 700 ℃ to 9
The temperature is raised to 00 ° C in 20 minutes, the temperature is raised to 1200 ° C under the same conditions, and the heat treatment is performed for 1 hour.
m] and the oxygen precipitate density in the surface layer 10 [μm] to 60 [μm] were evaluated by IR tomography. The evaluation result is shown in FIG. In FIG. 3, the horizontal axis shows the total time from 700 ° C. to 900 ° C., and the horizontal axis shows the BMD density.

Total time from 700 ° C to 900 ° C is 6
If it is 0 minutes (hydrogen replacement time 40 minutes + temperature rising time 20 minutes) or less, the density of oxygen precipitates in the surface layer 10 [μm] to 60 [μm] is 5 × 10 ⁶ [cm ⁻³ ] to 5 × 10 5. It was within ⁹ [cm ^-3 ]. Further, the surface layer 10 [μm] was 2 × 10 ⁶ [cm ⁻³ ] or less if it was 60 minutes or less.

Example 3 Next, using the same wafer as that evaluated in Example 2, a semiconductor device having a trench structure was manufactured. Then, evaluation was performed by etching with an optical microscope and SEM. The result is shown in FIG. As shown in FIG. 4, when the density of oxygen precipitates in the surface layer 10 [μm] to 60 [μm] was 5 × 10 ⁹ [cm ⁻³ ] or less, almost no defects were observed. Here, the reason why defects are generated when the oxygen precipitate density is 5 × 10 ⁹ [cm ⁻³ ] or more is that the strain accompanying the generation of individual oxygen precipitates increases as the precipitate density increases, and When the oxygen precipitation density is high, it is considered that defects (dislocations) were generated due to the thermal stress applied by the high temperature heat treatment.

On the other hand, when the density of oxygen precipitates in the surface layer of 10 [μm] to 60 [μm] is 5 × 10 ⁶ [cm ⁻³ ] or less, the gettering ability is lowered, so that the gettering ability is sufficiently increased. Oxygen precipitation density is 5 × 10 ⁶
It must be at least [cm ^-3 ].

As described above, in this embodiment, if the density of oxygen precipitates is set to 5 × 10 ⁹ [cm ⁻³ ] or less, the defect generation rate can be reduced. Further, in order to fully exert the gettering ability, it is necessary that the oxygen precipitation density is 5 × 10 ⁶ [cm ⁻³ ] or more. From the above, by setting the oxygen precipitate density in the surface layer 10 [μm] to 60 [μm] of the semiconductor substrate to 5 × 10 ⁶ [cm ⁻³ ] or more and 5 × 10 ⁹ [cm ⁻³ ] or less, the semiconductor substrate can be obtained. Since strain and generation of dislocations due to stress of high temperature heat treatment can be reduced,
The yield can be improved.

Embodiment 4 Next, in the present embodiment, as parameters of oxygen concentration contained in the semiconductor substrate, 11, 12, 13, 15, 16.
Using 5,18 × 10 ¹⁷ [atoms / cm ³ ], heat treatment was performed in the same manner as in Example 1, and oxygen precipitation in the surface layer 60 [μm] of 700 ° C. to 900 ° C. transit time of 40 minutes and 65 minutes was performed. The material density was evaluated by an IR tomograph. The evaluation result is shown in FIG. From FIG. 5, when the passage time from 700 ° C. to 900 ° C. is 65 minutes, the oxygen concentration is 12 × 10 ¹⁷ [atoms /
cm ³ ], and oxygen concentration 13 × 10 ¹⁷ [atoms / cm ³ ], the oxygen precipitate density increased rapidly, and the oxygen concentration 16
The density of oxygen precipitates was 5 × 10 ⁹ [cm ⁻³ ] or more at × 10 ¹⁷ [atoms / cm ³ ]. Next, 700 ° C to 900 ° C
When the passage time is 40 minutes, the oxygen concentration is 12-18 × 10 ¹⁷
[atoms / cm ³ ], the density of oxygen precipitates is 5 × 10 ⁶ [c
It is within m ⁻³ ] to 5 × 10 ⁹ [cm ⁻³ ].

On the other hand, the oxygen concentration is 11 × 10 ¹⁷ [atoms / cm
³ ], the oxygen precipitation density was 5 × 10 ⁶ regardless of the passage time.
[cm ^-3 ] or less. Oxygen precipitation density is 5 × 10 ⁶
In the case of [cm ^-3 ] or less, the gettering ability will be deteriorated. Therefore, in order to fully exert the gettering ability, it is necessary that the oxygen concentration is 12 × 10 ¹⁷ [atoms / cm ³ ] or more. Is.

As described above, in this embodiment, generally, the higher the oxygen concentration, the higher the density of oxygen precipitates.
When the passage time at 0 ° C is 40 minutes, the oxygen concentration is 12 to
It was found that the oxygen precipitate density was within 5 × 10 ⁶ [cm ⁻³ ] to 5 × 10 ⁹ [cm ⁻³ ] in the case of 18 × 10 ¹⁷ [atoms / cm ³ ]. Therefore, the oxygen concentration is 12 to 18 × 10 ^17.
By setting it within the range of [atoms / cm ³ ], the density of oxygen precipitates can be reduced, so that strain in the semiconductor substrate, and generation of dislocation due to stress of high temperature heat treatment can be reduced, The yield can be improved.

[0032]

As described above, according to the present invention, near-perfect defect-free layers can be formed near the surface of a semiconductor substrate used for a semiconductor device by IG treatment in a conventional oxygen atmosphere. can do.

Further, at a temperature of 1100 ° C. or higher in gas, 3
When performing heat treatment for 0 minutes or more, the temperature rises from 700 ° C to 9 ° C.
By keeping the passage time at 00 ° C within 60 minutes, the growth of oxygen precipitates is suppressed, and as a result, 10 [μ
The volume expansion of the area up to m] and the surface layer 10 [μm] to 60
Since the difference in the volume expansion amount in the region up to [μm] can be reduced, it is possible to prevent the occurrence of dislocation due to stress in the subsequent high temperature heat treatment.

Furthermore, the density of oxygen precipitates in the region from the surface layer 10 [μm] to 60 [μm] of the semiconductor substrate is 5 × 10 ^6.
The volume expansion amount in the region from the surface layer to 10 [μm] and the volume expansion amount in the region from the surface layer 10 [μm] to 60 [μm] can be controlled by setting [cm ⁻³ ] to 5 × 10 ⁹ [cm ⁻³ ] or less. Since the difference in the volume expansion amount can be reduced, it is possible to prevent the occurrence of dislocation due to stress in the subsequent high temperature heat treatment.

[Brief description of drawings]

FIG. 1 is a flowchart showing steps of a method for manufacturing a semiconductor substrate according to the present invention.

FIG. 2 shows oxygen precipitates in the surface layer 10 [μm] and the surface layer 10 with the temperature rising time from 700 ° C. to 900 ° C. as a parameter.
It is a chart showing the result of having evaluated the oxygen precipitate density from [μm] to 60 [μm] by an IR tomograph.

FIG. 3 shows oxygen precipitates in the surface layer 10 [μm] and the surface layer 10 [μm] with the time required for hydrogen substitution as a parameter.
2 is a chart showing the results of evaluation by oxygen tomography of the density of oxygen precipitates from 1 to 60 [μm].

FIG. 4 is a table showing the defect occurrence rate of semiconductor devices according to the density of oxygen precipitates in the surface layer 10 [μm] to 60 [μm].

FIG. 5 is a chart showing the results of evaluating the oxygen precipitate density of the surface layer 60 [μm] of the passage time of 40 minutes and 65 minutes by an IR tomograph as a parameter of the oxygen concentration contained in the semiconductor substrate. .

FIG. 6 is a view showing a cross section of a semiconductor substrate.

[Explanation of symbols]

 1 Semiconductor substrate 3 Oxygen precipitate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihiko Saito 72 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Stock Company Toshiba Horikawa-cho Factory

Claims (6)

[Claims] 1. A method for manufacturing a semiconductor substrate in which the vicinity of the surface of the semiconductor substrate is made defect-free, and heat treatment is performed at a temperature of 1100 ° C. or more for 30 minutes or more in a reducing atmosphere, an inert gas, or a mixed gas thereof. At this time, the manufacturing time of the semiconductor substrate is characterized in that the passage time of the temperature rising process from 700 ° C. to 900 ° C. is within 60 minutes. 2. A method of manufacturing a semiconductor substrate, in which the vicinity of the surface of the semiconductor substrate is made defect-free, and a gas introducing step of introducing the semiconductor substrate into a reducing atmosphere, an inert gas, or a mixed gas thereof, A temperature raising step of raising the passing time from 700 ° C. to 900 ° C. within 60 minutes for the reducing atmosphere, the inert gas or a mixed gas thereof, and a heat treatment for 30 minutes or more at a temperature of 1100 ° C. or more A method of manufacturing a semiconductor device, comprising: performing a heat treatment step. 3. The method of manufacturing a semiconductor substrate according to claim 1, wherein hydrogen is used in the reducing atmosphere. 4. The method of manufacturing a semiconductor substrate according to claim 1, wherein argon is used as the inert gas. 5. The oxygen concentration of the semiconductor substrate is 12 × 10.
^The method for producing a semiconductor substrate according to claim 1 or 2, wherein the amount is from ¹⁷ [atoms / cm ³ ] to 18 × 10 ¹⁷ [atoms / cm ³ ]. 6. The oxygen precipitate density in the surface layer 10 [μm] to 60 [μm] is 5 × 10 ⁶ [cm ⁻³ ] or more and 5 × 10 ⁹ [c].
m ^-3 ] or less, The semiconductor substrate characterized by the above-mentioned.