JPH0897220A - Manufacture of silicon epitaxial wafer, and silicon epitaxial wafer - Google Patents

Abstract

PURPOSE: To obtain a device active layer free from defect, realize high density BMD in a substrate part without IG treatment, and exhibit sufficient gettering effect, by setting the rate of temperature rise to be lower than or equal to a specified value, or maintaining the layer at an arbitrary temperature for a specified length of time, in a specified temperature range before growth. CONSTITUTION: An epitaxial wafer wherein Si single crystal is grown on an Si wafer, without giving thermal hysteresis at 800 deg.C or higher, at a growth temperature of 1050-1250 deg.C is manufactured. The Si wafer is manufactured from single crystal ingot manufactured by the Czochralski method, and the interstitial oxygen concentration [Oi] is lower than 1.80×10<18> atoms/cm<3> . In the temperature range of 800-1000 deg.C before growth, (1) the rate of temperature rise is set at 15 deg.C/min, or (2) an arbitrary temperature is maintained for 5-100min. Thereby the oxygen deposition density [BMD] in a substrate wafer is set as follows; [BMD] <=1×10<10> atoms/cm<3> and [BMD] >=exp 1,151×10<-17> ×[Oi]+1.151}atoms/cm<3> .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon wafer for semiconductor devices such as VLSI and a method for manufacturing the same.

[0002]

2. Description of the Related Art In a manufacturing process of a semiconductor device for VLSI, a semiconductor in which a minute amount of metal impurities mixed in a wafer and a minute defect existing in a device active region (about 10 μm in depth from the wafer surface) of the wafer are manufactured. This may cause deterioration of device characteristics and reliability. Therefore, various measures have been conventionally taken to reduce these metal impurities and minute defects as much as possible.

As a method of reducing metal impurities, there is a backside damage method (BSD method) in which a minute strain is provided on the back surface of a wafer by sandblasting or the like for capturing (gettering) metal impurities. A method of depositing polycrystalline silicon on the back surface of the wafer is also used.

As a measure against the latter, an epitaxial wafer having a vapor-grown single crystal silicon layer having no minute defects in the device active region is used. Furthermore, an intrinsic gettering method (IG method) has been developed to take measures against both. The IG method heat-treats a wafer at a high temperature to diffuse oxygen on the surface of the wafer outward to reduce interstitial oxygen, which serves as a nucleus for microdefects, and to reduce de defects that do not have microdefects in the device active region.
A nude zone (DZ layer) is formed. Further, the excessive interstitial oxygen contained in the deep region (bulk part) below the DZ layer is precipitated by the high temperature heat treatment, and a small amount of S
BMD represented by iO ₂ precipitate is generated. These BMDs exert strain on the silicon matrix in the bulk portion to induce secondary dislocations and stacking faults, and getter metal impurities.

In the IG method, a plurality of steps of heat treatment are carried out for the purpose of not being affected by the thermal history of the pulled single crystal silicon ingot and of utilizing a wafer having a wider oxygen concentration range. . First,
In the pre-heat treatment, heat treatment is performed at a high temperature (800 to 1200 ° C.) in an oxygen-containing inert gas atmosphere to diffuse oxygen outward from the wafer surface to reduce BMD nuclei that originally existed due to oxygen. ·Extinguish. Next, heat treatment at a low temperature (500 to 900 ° C.) in the middle stage in an oxygen atmosphere is performed to generate BMD nuclei in the bulk part. Finally, by heat treatment at medium temperature (up to 1000 ° C) in an oxygen atmosphere,
BMD nuclei are grown to generate and grow BMD.
Various ideas have been made for the heat treatment in the middle stage, and for example, isothermal annealing, multi-stage annealing from low temperature, ramping annealing from low temperature, etc. are typical.

In the above-mentioned IG method, the outward diffusion of oxygen due to the heat treatment in the preceding stage is not sufficient in practice, and minute oxygen precipitates (BMD etc.) may remain in the device active region. Further, since a plurality of heat treatment steps are required, practical application has not progressed so much due to workability problems and cost problems.

Recently, instead of the method requiring such multi-step heat treatment, 100% reducing gas or 100%
By performing high temperature heat treatment in an inert gas or a mixed gas atmosphere of a reducing gas and an inert gas, a DZ layer is formed on the wafer surface and a BMD is formed on the bulk portion, and an intrinsic gettering effect (IG effect) is provided. Wafer manufacturing methods are also used. The applicant of the present invention relates to the production methods thereof in JP-A-60-247935 and 61-61.
193458, JP-A-61-193459, JP-A-61-193456, JP-A-62-123098,
Patent applications such as JP-A-2-177541 are filed.

The mechanism of forming the wafer structure by the above heat treatment process can be estimated as follows. During the temperature raising process, the temperature rising rate is slow, so BMD in the bulk part
Growth of oxygen occurs simultaneously with the outward diffusion of oxygen in the surface layer, and the oxygen concentration in the surface layer decreases. After reaching the heat treatment temperature, outward diffusion of oxygen in the surface layer portion is further performed, and interstitial oxygen, which becomes BMD nuclei in the surface layer portion, decreases and BMD in the surface layer portion decreases.
Disappearance is accelerated. In the bulk portion, oxygen is diffused in the wafer due to the high temperature heat treatment, and BMD shrinkage occurs. However, since the amount of oxygen decrease is small, BMD disappears. During the temperature lowering process, since the temperature rising rate is slow, theoretically BMD growth also occurs in the wafer surface layer portion, but oxygen in the surface layer portion is reduced by outward diffusion, so BMD is not formed.
It becomes the Z layer. On the other hand, BMD growth / precipitation occurs again in the bulk portion.

It is understood that the BMD density of the bulk portion after the heat treatment depends on the initial oxygen concentration of the wafer, and that the BMD density of the bulk portion increases as the initial oxygen concentration increases. In particular, [Oi] is 1.6 × 10 ¹⁸ atoms / cm
If it is ³ or more, the BMD density is 10 ⁹ pieces / cm ³ or more.

Further, [Oi] is 1.55 × 10ato.
When heat-treating a silicon wafer of less than ms / cm ³ in a hydrogen atmosphere in the range of 1100 ° C. to 1300 ° C., the heating rate in the temperature range of 1000 ° C. to 1300 ° C. should be 5 to 10 ° C./min. The BMD density of the bulk part inside the wafer is [BMD] ≦ 1 × 1
0 ¹⁰ pieces / cm ³ , and [BMD] ≧ exp {1.151
Wafers of × 10 ^-17 × [Oi] +1.151} / cm ³ can be manufactured.

In recent years, in order to improve the characteristics of a highly integrated memory device or the like, a silicon wafer as a starting material is required to have a device active layer on the surface closer to a perfect defect-free and complicated. It is necessary and important to have a structure capable of gettering metal impurities that are mixed in during the device manufacturing process.

A typical epi-growth process consists of a sequence of temperature increase, hydrochloric acid etching, Si epi-growth and temperature decrease in a hydrogen atmosphere at atmospheric pressure. In order to increase the throughput and to reduce the slip and surface deviation of the wafer at the temperature increase, the temperature increase rate is set to 30 in the temperature range of 900 ° C. or higher.
C / min. However, at this time, the BMD is reduced and eliminated as described above.

Therefore, in the epitaxial wafer, the gettering effect cannot be expected unless the substrate wafer is subjected to the BSD or IG treatment as described above. The present invention has been made to solve the above problems. In an epitaxial wafer, a device active layer is formed more defect-free, and a substrate portion is formed with a high density of BMD without IG treatment. An object of the present invention is to provide a method for manufacturing a silicon epitaxial wafer capable of exhibiting a sufficient gettering effect, and such a silicon epitaxial wafer.

[0014]

The first invention of the present application is that the interstitial oxygen concentration [Oi] produced from a single crystal silicon ingot produced by the Czochralski method is 1.80 × 10 ¹⁸ atoms. In producing an epitaxial wafer in which a Si single crystal is grown at a growth temperature of 1050 to 1250 ° C. on a silicon wafer of less than 1 cm ³ / cm ³ without giving a thermal history of 800 ° C. or higher,
In the temperature range of 00 to 1000 ° C., (1) the temperature rising rate is set to 15 ° C./min or less, or (2) the temperature is kept at an arbitrary temperature for 5 to 100 min to obtain the oxygen precipitation density [BMD] inside the substrate wafer. ] Is [BMD] ≦ 1
× 10 ¹⁰ pieces / cm ³ , and [BMD] ≧ exp {1.1
The gist is a method for producing a silicon epitaxial wafer, which comprises producing an epitaxial wafer of 51 × 10 ⁻¹⁷ × [Oi] +1.151} / cm ³ .

The second invention of the present application is that the interstitial oxygen concentration [Oi] produced from a single crystal silicon ingot produced by the Czochralski method is 1.80 × 10 ^18.
800 ° C for silicon wafers less than atoms / cm ³
800-1000 ° C before growth without giving the above heat history
In the temperature range of (1), the heating rate is 15 ° C / min.
Or below (2) 5-100m at any temperature
The oxygen precipitation density [BMD] inside the substrate wafer, which is manufactured by holding in and growing a Si single crystal thereon at a growth temperature of 1050 to 1250 ° C., is [BMD] ≦ 1.
× 10 ¹⁰ pieces / cm ³ , and [BMD] ≧ exp {1.1
The gist is a silicon epitaxial wafer of 51 × 10 ⁻¹⁷ × [Oi] +1.151} / cm ³ .

The oxygen concentrations in this specification are all Ol.
d It is a value based on a conversion coefficient according to ASTM. Generally, the behavior of BMD during heat treatment of a wafer will be described.

According to the classical nucleation theory, BMD grows and contracts by attaching and desorbing supersaturated oxygen with oxygen clusters as uniform nuclei. Whether the BMD existing at a certain time grows, shrinks or disappears depends on the size of the BMD at that time and the critical nucleus radius determined by the temperature (and oxygen concentration) at that time. The critical nucleus radius depends on temperature, and the critical nucleus radius increases at higher temperatures. When the wafer is held at a certain temperature, the BM that has already grown larger than the critical nucleus radius at that temperature
D continues to grow, and BMD with a diameter smaller than the critical nucleus radius shrinks and disappears.

Based on the above findings and the above-mentioned findings in hydrogen treatment, the present inventors apply this to an epitaxial wafer manufacturing method to control the BMD of a substrate wafer portion, and are suitable for manufacturing highly integrated devices. The present invention has been accomplished by knowing that such a wafer can be manufactured.

The present invention is applied to the heat treatment of a silicon wafer produced from a silicon ingot produced by the ordinary Czochralski method and having a wafer of less than 1.80 × 10 ¹⁸ atoms / cm ³ .

During the temperature rising process of the epi growth process of the present invention,
Within the temperature range of 800 ° C to 1000 ° C, the heating rate is 1
It is necessary to set the temperature to 5 ° C./min or less, or to hold at any temperature within the above temperature range for 5 to 100 min.

In the range of 800 ° C to 1000 ° C,
If the heating rate is higher than 15 ° C./min, the above-mentioned increasing rate of the critical nucleus radius becomes higher than the growth rate of the already existing BMD at that temperature, and the heating process time becomes shorter. The difference between the critical nucleus radius and the diameter of the existing BMD becomes larger, and the BMD does not grow and heads for contraction.

As described above, BMD can be formed with a high density when the heating rate is set to 15 ° C./min or less. When the temperature is raised at the heating rate of the present invention, the size of the BMD is already larger than the critical nucleus radius at the epi growth temperature, so that the BMD grows.

Even when the temperature is raised at a normal rate of, for example, 30 ° C./min, by maintaining the temperature within the temperature range of 800 ° C. to 1000 ° C. for 5 to 100 minutes, BMD can be sufficiently grown at that temperature. As a result, the BMD already existing becomes larger than the size of the critical nucleus radius in the subsequent temperature raising process.
The MD does not go in the direction of reduction.

If the time is less than 5 minutes, the BMD does not grow to a sufficient size.
Is likely to shrink and disappear. Further, if it is carried out for more than 100 minutes, BMD grows large and a large number of precipitates occur, so that the width of the DZ layer becomes narrow, crystal transition occurs, or the mechanical strength deteriorates. May be adversely affected.

During the temperature lowering process, BMD has already grown on the substrate portion, and changing the temperature lowering rate has no significant effect. However, the rate of temperature decrease is preferably 2 to 300 ° C./min in view of productivity, quality of the wafer (preventing occurrence of slippage and surface roughness), structural problems of the furnace used, and the like.

By performing such an epi growth process, the initial oxygen concentration is 1.80 × 10 ¹⁸ atoms /
BMD density [BMD] ≦ 1 × 10 ¹⁰ pieces / cm ³ and [BMD] ≧ using a silicon wafer of less than cm ³
exp {1.151 × 10 ^-17 × [Oi] +1.15
1} wafers / cm ³ can be manufactured.

Such a wafer is indicated by the area A + B + C in the graph of FIG. Even if the substrate wafer having the above-mentioned initial oxygen concentration is not subjected to the IG treatment, there is no epitaxial wafer having a BMD density in the above-mentioned range within the above range, and it is provided by the present invention for the first time.

A more preferable range of BMD density is as follows.
When 1.55 × 10 ¹⁸ atoms / cm ³ ≧ [Oi], 1 × 10 ⁸ pieces / cm ³ ≦ [BMD] ≦ 1 × 10 ¹⁰ pieces / c
m ³ , [Oi]> 1.55 × 10 ¹⁸ atoms / cm ³
[BMD] ≧ exp {1.151 × 10 ⁻¹⁷ ×
[Oi] +1.151} / cm ³ (area B + in FIG. 1
C) and [BMD] ≦ 1 × 10 ¹⁰ pieces / cm
³ , and [BMD] ≧ exp {4.605 × 10 ⁻¹⁸ ×
[Oi] +12.434} / cm ³ (region C in FIG. 1). A wafer having a BMD density in this range has a sufficient gettering function.

[0029]

EXAMPLES Hereinafter, the wafers used for explaining the examples of the present invention were all silicon wafers cut out from a silicon ingot pulled up by the Czochralski method, manufactured by a usual method, and subjected to mirror finishing. These wafers are of N type, plane orientation (10
0), the specific resistance is 1 to 1000 Ω / cm, and [Oi] is 1.4.
It is 5 to 1.72 × 10 ¹⁸ atoms / cm ³ .

Epitaxial growth is carried out by a general-purpose cylinder type epitaxy apparatus.
Cl _{4 was used} , the growth temperature was 1150 ° C., and the epi film thickness was 20 μm. Example 1 Among the above wafers, [Oi] was 1.45 × 10 ¹⁸ at
800 ° C to 1150 ° C for oms / cm ³ wafers
The temperature rising rate in the range was 8.5 ° C./min. Example 2 Among the above wafers, [Oi] was 1.51 × 10 ¹⁸ at
800 ° C to 1150 ° C for oms / cm ³ wafers
The temperature rising rate in the range was set to 6.3 ° C./min. Example 3 Among the above wafers, [Oi] was 1.61 × 10 ¹⁸ at
800 ° C to 1000 ° C for oms / cm ³ wafers
Heating rate in the range of 10 ° C / min from 1000 ° C to 1
The rate of temperature rise in the range of 150 ° C was set to 15 ° C / min. Example 4 Among the above wafers, [Oi] was 1.61 × 10 ¹⁸ at
800 ° C to 1000 ° C for oms / cm ³ wafers
Heating rate in the range of 10 ° C / min from 1000 ° C to 1
The temperature rising rate in the range of 150 ° C was set to 20 ° C / min. Example 5 Among the above wafers, [Oi] was 1.70 × 10 ¹⁸ at
800 ° C to 1150 ° C for oms / cm ³ wafers
The temperature rising rate in the range was set to 3.8 ° C./min. Example 6 Among the above wafers, [Oi] was 1.61 × 10 ¹⁸ at
With a wafer of oms / cm ^3, the temperature rising rate up to 900 ° C. was 20 ° C./min, the temperature was held at 900 ° C. for 20 minutes, and the temperature rising rate in the range of 900 ° C. to 1150 ° C. was 20 ° C./min. Comparative Example 1 Among the above wafers, [Oi] was 1.70 × 10 ¹⁸ at
800 ° C to 1100 ° C for oms / cm ³ wafers
The heating rate in the range of 100 ° C./min and the heating rate in the range of 1100 ° C. to 1150 ° C. were 10 ° C./min. Comparative Example 2 Among the above wafers, [Oi] was 1.61 × 10 ¹⁸ at
800 ° C to 1150 ° C for oms / cm ³ wafers
The temperature rising rate in the range was set to 30 ° C./min. Comparative Example 3 Among the above wafers, [Oi] was 1.51 × 10 ¹⁸ at
800 ° C to 1150 ° C for oms / cm ³ wafers
The temperature rising rate in the range was set to 30 ° C./min. Comparative Example 4 Among the above wafers, [Oi] was 1.70 × 10 ¹⁸ at
800 ° C to 1150 ° C for oms / cm ³ wafers
The temperature rising rate in the range was set to 30 ° C / min. Comparative Example 5 Among the above wafers, [Oi] was 1.61 × 10 ¹⁸ at
With a wafer of oms / cm ^3, the temperature rising rate up to 900 ° C. was 20 ° C./min, the temperature was held at 900 ° C. for 3 minutes, and the temperature rising rate in the range of 900 ° C. to 1150 ° C. was 20 ° C./min. Comparative Example 6 Among the above wafers, [Oi] was 1.61 × 10 ¹⁸ at
With a wafer of oms / cm ^3, the temperature rising rate up to 900 ° C. is 20 ° C./min, and the temperature is kept at 900 ° C. for 120 minutes.
To 1150 ° C., the temperature rising rate was 20 ° C./min.

The densities of BMDs produced by the infrared tomography method were measured from the cross-section ((110) plane) of the heat-treated wafers of these Examples and Comparative Examples. The minimum detectable BMD size in the infrared tomography method used is 20 nm. This method depends on the measurement area
The detection limit of MD density is different. In this measurement, the measurement was performed in a rectangular parallelepiped region having a depth of 185 μm and a surface of 4 × 200 μm on the wafer surface. In this case, the BMD density measurement limit is 6.8 × 10 ⁶ pieces / cm ³ . The measurement results are shown in Tables 1 and 2 together with the heat treatment conditions. Further, FIG. 1 shows a graph showing the relationship between the initial oxygen concentration of the wafer and the BMD density.

[0032]

[Table 1]

[0033]

[Table 2]

As is clear from Tables 1 and 2 and FIG. 1, even if the substrate wafer of the present invention is not an IG processed epitaxial wafer, the BM is formed on the substrate portion.
D can have a high density. That is, the oxygen precipitate density [BMD] of the substrate portion is [BMD] ≦ 1 × 10 ¹⁰ particles / cm ³ , and [BMD] ≧ exp {1.151 × 10.
^-18 × [Oi] +1.151} wafers / cm ³ can be manufactured.

On the other hand, as can be understood from the comparative example, the epitaxial wafers under the conditions outside the scope of the present invention also have a large amount of BMD, but the BMD density formed becomes low in the wafer having a low oxygen concentration. I understand. In Comparative Examples 2 to 4, although the defect-free layer is formed, the BMD of the bulk portion inside the wafer has a low density, and there is a possibility that a sufficient gettering function cannot be achieved.

Further, in Comparative Example 5, since the holding time is short, it can be seen that the BMD density becomes low as in Comparative Example 2. In Comparative Example 6, the holding time is long and B
Since excessive precipitation / growth of MD occurs, the amount of precipitation is large,
Not enough DZ layer was formed. In addition, crystal transition has occurred.

Further, since the epitaxial wafer of the present invention is constituted as described above, the device active layer is defect-free, and the BMD is sufficiently formed on the substrate portion, so that the device having good characteristics can be obtained at a high yield. Can be manufactured well.

In the epi process of the present invention, it is preferable that the temperature raising process and the temperature lowering process are performed in the same gas atmosphere, but the composition of the atmosphere gas may be changed in each.

[0039]

According to the present invention, a BM can be formed even on an epitaxial wafer in which the substrate wafer is not IG processed.
Since the D density can be increased and as a result, the gettering function is sufficient, a highly integrated device having good characteristics can be manufactured with a high yield. Further, such a wafer can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between an initial oxygen concentration of a substrate wafer and a BMD density after an epi process.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Kenro Hayashi, 30 Soya, Hadano City, Kanagawa Prefecture Toshiba Ceramics Co., Ltd. Development Laboratory (72) Katsuhiro Chaki, 30 Soya, Hadano City, Kanagawa Toshiba R & D Co., Ltd. In-house (72) Inaichi Kashima, No. 30 Soya, Hadano-shi, Kanagawa Toshiba Ceramics Co., Ltd. Development Lab.

Claims (2)

[Claims] 1. A silicon wafer having an interstitial oxygen concentration [Oi] of less than 1.80 × 10 ¹⁸ atoms / cm ³ manufactured from a single crystal silicon ingot manufactured by the Czochralski method has a thermal history of 800 ° C. or higher. Without giving
In manufacturing an epitaxial wafer on which a Si single crystal was grown at a growth temperature of 1050 to 1250 ° C., in the temperature range of 800 to 1000 ° C. before the growth,
The oxygen precipitation density [BMD] inside the substrate wafer can be increased by (1) setting the temperature rising rate to 15 ° C./min or less, or (2) holding at an arbitrary temperature for 5 to 100 minutes.
[BMD] ≦ 1 × 10 ¹⁰ pieces / cm ³ , and [BMD] ≧
exp {1.151 × 10 ^-17 × [Oi] +1.15
A method for producing a silicon epitaxial wafer, which comprises producing an epitaxial wafer having 1} pieces / cm ³ . 2. A silicon wafer having an interstitial oxygen concentration [Oi] of less than 1.80 × 10 ¹⁸ atoms / cm ³ manufactured from a single crystal silicon ingot manufactured by the Czochralski method has a thermal history of 800 ° C. or higher. Without giving
In the temperature range of 800 to 1000 ° C. before growth,
(1) A temperature rising rate is set to 15 ° C./min or less, or (2) An arbitrary temperature is maintained for 5 to 100 minutes, and a Si single crystal is grown on the growth temperature at 1050 to 1250 ° C. In addition, the oxygen precipitation density [BMD] inside the substrate wafer is [BMD] ≦ 1 × 10 ¹⁰ pieces / cm ³ ,
And [BMD] ≧ exp {1.151 × 10 ⁻¹⁷ × [O
i] +1.151} / cm ³ of silicon epitaxial wafer.