JP2000211995A - Silicon single crystal wafer and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enlarge the control region of defect-free layer depth and fine defect density of the inside in a CZ silicon wafer. SOLUTION: This silicon wafer is a silicon wafer which is obtained from a silicon single crystal rod grown by doping with nitrogen by CZ method, has 2-12 μm defect-free layer depth after gettering heat treatment and after device production and heat treatment of silicon wafer and 1×108 to 2×1010 defects/cm3 internal fine defect density after gettering heat treatment and after device production and heat treatment. This method for producing a silicon wafer comprises growing a silicon single crystal rod doped with nitrogen by CZ method while controlling a nitrogen concentration, an oxygen concentration and a cooling rate and processing the silicon single crystal rod into a wafer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for pulling a silicon single crystal by the Czochralski method (CZ method).
The present invention relates to a technique for producing a silicon single crystal wafer having a desired quality by doping with nitrogen and controlling the nitrogen concentration, the oxygen concentration, and the cooling rate to perform crystal growth.

[0002]

2. Description of the Related Art Wafers for manufacturing devices such as semiconductor integrated circuits are mainly manufactured by the Czochralski method (C
A silicon single crystal wafer grown by the Z method) is used. If a crystal defect exists in such a silicon single crystal wafer, a pattern defect or the like is caused at the time of manufacturing a semiconductor device. In particular, the pattern width in recent highly integrated devices is 0.3 μm
In the case of forming such a pattern, the presence of a crystal defect having a size of 0.1 μm may cause a pattern defect or the like at the time of forming such a pattern. Would.
Therefore, crystal defects existing in the silicon single crystal wafer must be reduced in size as much as possible.

In recent years, it has recently been reported that a silicon single crystal grown by the CZ method has a crystal defect called a Grown-in defect introduced during crystal growth. It is considered that the main cause of such crystal defects is a cluster of atomic vacancies that aggregate during the production of a single crystal or an oxygen precipitate that is an aggregate of oxygen atoms mixed in from a quartz crucible. If these crystal defects exist in the surface layer of the wafer on which the device is formed, they become harmful defects that degrade the device characteristics. Therefore, such crystal defects are reduced and the defect-free layer (DZ) having a sufficient depth is reduced. It is desirable to produce a wafer having () in the surface layer.

When heavy metal impurities such as Fe and Cu are present in the surface layer of a silicon single crystal wafer, device characteristics are degraded during device fabrication. Therefore, intrinsic gettering (IG) for depositing internal minute defects and removing heavy metal impurities as a gettering site in a bulk portion of a silicon wafer is important. In order to make this intrinsic gettering effective, it is necessary to form internal micro defects (BMD) of sufficient density in the bulk portion of the wafer. The term "internal micro defects" as used herein refers to oxygen precipitates present in the bulk and micro defects such as dislocations and stacking faults generated by oxygen precipitation.

[0005] In view of the above, in manufacturing a silicon semiconductor wafer, after the gettering heat treatment or the device process heat treatment, the depth of the defect-free layer on the surface of the wafer on which the device is to be manufactured and the inside of the wafer serving as the gettering site. The density of microdefects is an important factor.

The depth of the defect-free layer and the density of the internal minute defects are as follows:
It has been known that it depends on the oxygen concentration of the silicon single crystal grown by the CZ method or the cooling rate (growth rate) during the growth of the silicon single crystal. Therefore, conventionally, in order to control the depth of the defect-free layer and the density of the internal minute defects in the silicon wafer, the oxygen concentration and the cooling rate are mainly controlled.

[0007]

However, a silicon single crystal wafer obtained from a silicon single crystal rod grown by such a method of controlling the oxygen concentration and the cooling rate has a problem of crystal defects such as Grown-in defects. Because of the size,
The crystal defects could not be sufficiently eliminated by the subsequent gettering heat treatment or the like. As a result,
The depth of a defect-free layer of a conventional silicon single crystal wafer has been as shallow as about 0.5 μm at the maximum.

In the conventional method, 20 ppma (JEI
In the case of a wafer having a high oxygen concentration of about DA (standard of Japan Electronics Industry Development Association), the density of internal microdefects after heat treatment is a maximum of about 1 × 10 ¹⁰ / cm ³ , but oxygen-induced Since crystal defects remain, the yield of devices has been reduced. Further, in a wafer having an oxygen concentration of 9 to 17 ppma which is usually used for a device,
The density of internal microdefects after heat treatment is at most 1 × 10 ⁹
/ cm ³ , and the density of internal minute defects was insufficient to achieve a sufficient gettering effect. Therefore, there has been a problem that the yield of the device process is reduced due to heavy metal contamination on the wafer surface.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems, and in a silicon single crystal wafer manufactured by the CZ method, the controllable range of the defect-free layer depth and the internal fine defect density has been greatly expanded. And to obtain a high quality silicon single crystal wafer.

[0010]

According to a first aspect of the present invention, there is provided a silicon single crystal rod obtained by slicing a silicon single crystal rod grown by doping with nitrogen by the Czochralski method. A silicon single crystal wafer having a defect-free layer depth of 2 to 12 after a gettering heat treatment or a device manufacturing heat treatment of the silicon single crystal wafer.
μm, and the internal minute defect density after the gettering heat treatment or the device manufacturing heat treatment is 1 × 10 ⁸ to 2 × 1
A silicon single crystal wafer, which is a 0 ¹⁰ Quai / cm ^3.

The silicon single crystal wafer made of a silicon single crystal rod grown by doping with nitrogen by the Czochralski method has a defect-free layer depth of 2 to 12 μm after the gettering heat treatment or the device manufacturing heat treatment. so,
In addition, the internal minute defect density after the gettering heat treatment or the device manufacturing heat treatment is 1 × 10 ⁸ to 2 × 10 ¹⁰ pcs / cm.
³ , since control can be performed in a much wider range than a conventional silicon single crystal wafer, a silicon single crystal wafer having a wide device formation area and high gettering ability can be obtained.

Here, the gettering heat treatment is a general term for heat treatment performed after processing the grown silicon single crystal rod into a wafer and before entering a device process.
The purpose is to eliminate crystal defects near the surface mainly due to outward diffusion of impurity oxygen. The device heat treatment is a general term for heat treatment performed in a device manufacturing process after a gettering heat treatment and other processes are performed on a wafer.

In this case, as described in claim 2 of the present invention, the nitrogen concentration of the silicon single crystal wafer is 1 × 1.
It is preferable that the concentration be in the range of 0 ¹² to 1 × 10 ¹⁵ atoms / cm ³ . In order to reduce the size of the crystal defects and suppress the growth of the defects, it is desirable that the nitrogen concentration be 1 × 10 ¹⁰ atoms / cm ³ or more, so as not to hinder the single crystallization of the silicon single crystal. Is preferably not more than 5 × 10 ¹⁵ atoms / cm ^3, but this 1 × 10 ¹² to 1 × 10
^Since the nitrogen concentration in the range of ¹⁵ atoms / cm ³ is the most effective nitrogen concentration for suppressing the growth of crystal defects, if the nitrogen concentration of the wafer is within this range, it is necessary to sufficiently reduce the size of the crystal defects. And the depth of the defect-free layer after the gettering heat treatment can be increased.

In this case, as described in claim 3 of the present invention, the nitrogen concentration of the silicon single crystal wafer is 1 × 1.
More preferably, it is 0 ¹³ to 1 × 10 ¹⁴ atoms / cm ³ . If the nitrogen concentration is 1 × 10 ¹⁴ atoms / cm ³ or less,
After performing the gettering heat treatment or the device manufacturing heat treatment, the OSF nucleus can be more reliably eliminated, so that the characteristics of the device formed on such a wafer become more reliable. In addition, when epitaxial growth is performed on such a wafer surface, there is an advantage that along with the disappearance of the OSF, crystal defects such as stacking faults (SF) formed in the formed epitaxial layer can be significantly suppressed. On the other hand, if the nitrogen concentration 1 × 10 ¹³ atoms / cm ³ or more, the internal defect density after gettering heat treatment or device fabricating heat treatment is 1 × 10 ⁹ Ke / cm ³ or more can be surely obtained, even more A gettering effect can be expected.

In this case, as described in claim 4 of the present invention, the silicon single crystal wafer has an oxygen concentration of 9-1.
It is preferably 7 ppma. When the oxygen concentration of the silicon single crystal wafer falls within this range, the growth and formation of crystal defects can be further suppressed, and the formation of oxygen precipitates in the defect-free layer can also be prevented. On the other hand, in the bulk portion, oxygen precipitation is promoted by the presence of nitrogen, so that the IG effect can be sufficiently exhibited even at a low oxygen concentration of about 9 ppma, which is the lower limit of the above range.

In this case, as set forth in claim 5 of the present invention, the silicon single crystal rod is set at 1150 during crystal growth.
Cooling rate from 1.0 to 4.5 ° C to 1.0 to 4.5 ° C / m
It is preferably a single crystal rod grown while being controlled in the range of in. When the cooling rate from 1150 ° C. to 1080 ° C. after crystal growth is in the range of 1.0 to 4.5 ° C./min, crystal defects can be sufficiently reduced, and the defect-free layer depth after gettering heat treatment A silicon wafer having a thickness of 2 to 12 μm and an internal fine defect density of 1 × 10 ⁸ to 2 × 10 ¹⁰ chips / cm ³ can be manufactured. Further, if the cooling rate is in this range, it is not necessary to reduce the growth rate of the silicon single crystal so as to affect the productivity.

According to a sixth aspect of the present invention, in a method for manufacturing a silicon single crystal wafer, a silicon single crystal rod doped with nitrogen by the Czochralski method is provided with a nitrogen concentration, an oxygen concentration, and a cooling rate. And manufacturing the silicon single crystal wafer by slicing the silicon single crystal bar and processing it into a wafer.

As described above, by growing not only the oxygen concentration and the cooling rate but also the nitrogen doping amount and growing the silicon single crystal rod, the control range of the defect-free layer depth and the internal minute defect density is greatly increased. Enlarged, defect-free layer depth 2-12
μm and the density of internal minute defects is 1 × 10 ⁸ to 2 ×
A high-quality silicon single crystal wafer having a density of 10 ¹⁰ / cm ³ can be manufactured.

In this case, as described in claim 7 of the present invention, when growing a silicon single crystal rod doped with nitrogen by the Czochralski method, the concentration of nitrogen doped into the single crystal rod is 1 ×. 10 ¹² -1 × 10 ¹⁵ atoms / cm
It is preferable to control the ^3, as described in claim 8, the nitrogen concentration ^{1 × 10 13 ~1 × 10 14} atoms / cm 3
It is more preferable to control to. Further, as described in claim 9, the concentration of oxygen contained in the single crystal rod is 9 to 17 p.
pma, preferably 1150 ° C. at the time of crystal growth of the single crystal rod as described in claim 10.
Cooling rate from 1.0 to 4.5 ° C / min.
It is preferable to control within the range.

As described above, when growing a nitrogen-doped silicon single crystal rod, by controlling the nitrogen concentration, oxygen concentration and cooling rate within the above ranges, the depth of the defect-free layer is ensured to be 2 to 12 μm. And the internal minute defect density is 1
It is possible to manufacture a silicon single crystal wafer controlled at a rate of × 10 ^{8 to} 2 × 10 ¹⁰ pieces / cm ³ .

Hereinafter, the present invention will be described in more detail. According to the present invention, in addition to controlling the oxygen concentration and the cooling rate performed by the conventional method, by controlling the nitrogen concentration in the silicon single crystal, the defect-free layer depth and the internal minute defect density are controlled. Based on the finding that the range to be obtained can be greatly expanded, the inventor has conducted extensive research and completed the work.

Conventionally, the depth of a defect-free layer and the density of internal minute defects of a silicon wafer can be controlled only in an extremely narrow range. Here, FIG. 1 is a diagram showing the defect-free layer depth and the internal minute defect density of a silicon single crystal wafer at various parameter values such as oxygen concentration.

As shown in FIG. 1, even when the oxygen concentration is changed and the cooling rate is changed as in the conventional method, the depth of the defect-free layer and the density of the internal minute defects in a wafer having an oxygen concentration of 9 to 17 ppma are as follows. 0 to 0.5 μm, 8 × 1 each
0 ^6-1 it can be seen that can only be controlled within a narrow range such as × 10 ⁹ Ke / cm ^3.

This was due to the size of crystal defects, the size of oxygen precipitates, and the density thereof in the conventional method. FIG.
(A) and (b) are crystal defects in a silicon single crystal wafer,
FIG. 2 is a diagram schematically showing the appearance of oxygen precipitates, and FIG.
(B) is a diagram showing a state inside the wafer by a conventional manufacturing method. As shown in FIG. 2B, according to the conventional method, although the density of crystal defects is low and the number of defects is small, large-sized crystal defects are generated. This large crystal defect cannot be sufficiently removed by the subsequent gettering heat treatment or the like, which causes the depth of the defect-free layer to be reduced. Further, since the density of the oxygen precipitate in the wafer bulk portion is low and the size thereof is small, the gettering ability is low.

Therefore, the inventors of the present invention conceived of doping nitrogen and growing the silicon single crystal by the Czochralski method and controlling the amount thereof. FIG. 1 also shows the defect-free layer depth and the internal minute defect density at each parameter value of the silicon single crystal wafer of the present invention. From FIG. 1, the wafer of the present invention has a defect-free layer depth of 2 to 12 μm and an internal fine defect density of 1 × 10 ⁸ to 2 × 10 ¹⁰ .
It can be seen that control can be performed over a wide range of / cm ³ .

FIG. 2A shows the inside of the wafer of the present invention. As shown in FIG. 2A, according to the method of the present invention, although the density of crystal defects is high and the number of defects is large, crystal defects of small size are generated. Such small crystal defects can be easily erased by a subsequent gettering heat treatment or the like. Therefore, the depth of the defect-free layer can be significantly deeper than that of a conventional wafer. In addition, since a large amount of large-sized oxygen precipitates which are hardly dissolved by the gettering heat treatment precipitate in the bulk portion of the wafer, a much higher gettering effect can be obtained as compared with a conventional wafer.

The silicon single crystal wafer of the present invention has such properties because it is doped with an appropriately controlled amount of nitrogen. That is, it has been pointed out that doping nitrogen into a silicon single crystal suppresses the aggregation of atomic vacancies in silicon and reduces the size of crystal defects (T. Abe and H. Takeno, Mat. Res. Soc.Symp.Proc.Vol.2
62,3,1992). This effect is considered to be due to the transition of the process of aggregation of atomic vacancies from the formation of uniform nuclei to the formation of heterogeneous nuclei. Therefore, by doping nitrogen when growing a silicon single crystal by the CZ method, it is possible to obtain a silicon single crystal with a very small crystal defect size and a silicon single crystal wafer obtained by processing the same.

On the other hand, it is known that nitrogen atoms have the effect of promoting oxygen precipitation during crystal growth. (For example,
F. Shimura and RSHockett, Appl. Phys. Lett. 48, 224, 19
86). Therefore, by doping nitrogen in an appropriate amount, the density of oxygen precipitates in the wafer bulk portion can be increased, and the gettering ability of the silicon single crystal wafer can be significantly improved.

When nitrogen is doped into a silicon single crystal,
It is considered that the reason why the number of crystal defects introduced into silicon is reduced is that the aggregation process of atomic vacancies shifts from uniform nucleation to heterogeneous nucleation as described above. Therefore, the concentration of nitrogen to be doped is preferably set to 1 × 10 ¹⁰ atoms / cm ³ or more which causes sufficient heterogeneous nucleation.
In addition, 5 × 10 ¹⁵ at which is the solid solution limit in silicon single crystal
If it exceeds oms / cm ³ , single crystallization of the silicon single crystal itself may be hindered. Therefore, it is desirable not to exceed this concentration.

Further, the inventor of the present invention has conducted further studies and studies on the nitrogen concentration. As a result, the generation of crystal defects is suppressed, and the nitrogen concentration is effective for controlling the depth of the defect-free layer and the density of the internal minute defects. Is 1 × 10 ¹² to 1 × 10 ¹⁵ atom
s / cm ³ range. This is because, if the concentration of nitrogen to be doped is relatively high, in such a concentration range, the defect-free layer depth and the internal minute defect density can be easily controlled within the range of the wafer of the present invention.

In addition, the inventor of the present invention has continued his research on the nitrogen concentration. It is most effective to set the nitrogen concentration to 1 × 10 ¹³ to 1 × 10 ¹⁴ atoms / cm ^3. It has been found. The inventors of the present invention performed the following experiment to find the optimum value of the nitrogen concentration. (Experiment 1) First, a single crystal rod having a diameter of 8 inches, a P type (boron dope) and an orientation of <100> was pulled at a pulling speed of 1.0.
mm / min and 1.8 mm / min. At that time, the nitrogen concentration was 3 × 10 ¹² to 1 × 10 ¹⁵ at
The amount of the wafer with the silicon nitride film introduced into the raw material was adjusted so as to be oms / cm ³ . Then, the pulled silicon single crystal rod was processed to produce a silicon single crystal mirror-finished wafer. Each of the silicon single crystal mirror-surface wafers manufactured has a resistivity of about 10 Ω · cm and an oxygen concentration of 9 to 17 pp.
ma (JEIDA).

Next, these wafers were heated at 1100 ° C. for 6 hours.
OSF oxidation heat treatment for 0 min.
The width of the region was measured, and the measurement results are shown in FIG. FIG.
For example, the notation 1.0E + 13 on the horizontal axis is 1 × 10
¹³ means. From FIG. 3, the nitrogen concentration is 1 × 10
^It can be seen that at ¹⁴ atoms / cm ³ or less, the width of the region where OSF occurs is extremely reduced.

Further, another wafer manufactured under the same conditions as the wafer whose OSF was investigated was subjected to a heat treatment (800 ° C., 4 hours) (nitrogen atmosphere) at 800 ° C. for 4 hours without OSF oxidation.
Oxidation heat treatment was performed at 00 ° C. for 16 hours, and the internal minute defect density of the wafer was evaluated by the OPP method described later. As a result, the nitrogen concentration was found to reliably 1 × 10 ⁹ Ke / cm ³ or more bulk micro defect density is obtained in the 1 × 10 ¹³ atoms / cm ³ or more.

(Experiment 2) Nitrogen concentration is 1 × 10 ¹³ to 1 ×
Except for 10 ¹⁵ atoms / cm ³ , a silicon single crystal mirror surface wafer having the same specifications as in Experiment 1 was prepared, and as a gettering heat treatment, the temperature was increased at a rate of 6 ° C./min in a 100% hydrogen gas atmosphere, and at 1200 ° C. for 60 minutes. After being maintained, it was classified into those subjected to a heat treatment of cooling at 3 ° C./min and those not subjected to the heat treatment. Next, a silicon epitaxial growth of 15 μm thickness was performed on the surface of each wafer at 1090 ° C. using an epitaxial growth apparatus. And
The stacking fault (SF) density on the surface after the epitaxial growth was measured by SP1 (trade name, manufactured by KLA Tencor), and the results are shown in FIG. In FIG. 4, for example, the notation 1.0E + 13 on the horizontal axis means 1 × 10 ¹³ .

FIG. 4 shows that the nitrogen concentration was 1 × 10 ¹⁴ atoms / regardless of the pulling speed and the presence or absence of the gettering heat treatment.
cm ³ or less, the stacking fault (S
F) It can be seen that the density can be significantly reduced.

The above can be understood by summarizing the above experimental results. When a wafer doped with nitrogen is subjected to a gettering heat treatment or a device manufacturing heat treatment, most of the nuclei of OSF (oxidation-induced stacking faults) originally present on the wafer surface disappear, so that OSF is generated and the device characteristics are reduced. Has little effect on

However, when the nitrogen concentration is 1 × 10 ¹⁴ atoms / cm
If the value is ³ or less, even before the gettering heat treatment or the device manufacturing heat treatment, the number of OSF nuclei is extremely small, so that the region where OSF is generated can be almost completely eliminated over the entire surface of the wafer. Therefore, after the gettering heat treatment or the device manufacturing heat treatment is performed, the OSF nucleus can be more reliably eliminated, so that the characteristics of the device formed on such a wafer are more reliable. Become. OSF
The nucleus of the oxide film is described later in the oxide film breakdown voltage characteristic evaluation (TZDB, TDD).
B) is a defect that is not detected as a defect.

The nitrogen concentration is set to 1 × 10 ¹⁴ atoms / cm ³
In the following cases, when the OSF nuclei are eliminated and the epitaxial growth is performed on the wafer surface, the stacking fault (S) formed in the formed epitaxial layer is formed.
There is also an advantage that crystal defects such as F) can be significantly suppressed.

On the other hand, when the nitrogen concentration is 1 × 10 ¹³ atoms / cm ³
If it is above, since the internal defect density after the gettering heat treatment or the device manufacturing heat treatment is 1 × 10 ⁹ / cm ³ or more, a further gettering effect can be surely expected.

In order to control the defect-free layer depth and the internal minute defect density within the range of the wafer of the present invention,
It has been found that it is preferable to have an oxygen concentration in the range of 9 to 17 ppma. This means that when the oxygen concentration is 17 ppma or less, there is no danger that harmful oxygen precipitates are formed on the defect-free layer where the device is formed after wafer processing.
Conversely, by setting the content to 9 ppma or more, oxygen precipitates become insufficient, and there is no fear that the gettering effect is reduced or the crystal strength is reduced. Therefore, the oxygen concentration of the silicon single crystal wafer is preferably in the range of 9 to 17 ppma.

In order to control the defect-free layer depth and the internal minute defect density within the range of the wafer of the present invention, the inventor has set the cooling rate from 1150 ° C. to 1080 ° C. during crystal growth to 1.0 to 4 ° C. It has been found that it is preferable to control the temperature to 0.5 ° C./min. This is because the size of crystal defects is greatly affected by the transit time of the atomic vacancies in the aggregation temperature zone. If the cooling rate is increased to 1.0 ° C./min or more, the size of crystal defects can be reduced, and the cooling rate is 4.5 ° C./m
If it is not more than in, dislocation-free crystals can be grown.
Therefore, in order to control the wafer within the range of the present invention, it is preferable to control the cooling rate within the range of 1.0 to 4.5 ° C./min. In addition, it is only necessary to find a production condition under which a dislocation-free crystal can be produced even at a cooling rate of 4.5 ° C./min or more.

[0042]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a silicon single crystal rod doped with nitrogen by the CZ method may be grown by a known method described in, for example, Japanese Patent Application Laid-Open No. 60-251190. .

That is, in the CZ method, a seed crystal is brought into contact with a melt of a polycrystalline silicon raw material accommodated in a quartz crucible,
This is a method of growing a silicon single crystal rod of a desired diameter by slowly pulling it up while rotating it. The nitride is put in a quartz crucible in advance, the nitride is put into a silicon melt, or the atmosphere is By making the gas into an atmosphere containing nitrogen, nitrogen can be doped into the pulled crystal. At this time, by adjusting the amount of nitride, the concentration of nitrogen gas, the introduction time, etc.,
The doping amount in the crystal can be controlled. Thus the aforementioned ^{1 × 10 1 2 ~1 × 10} 15 atoms / cm 3 or 1
It is also easy to control the nitrogen concentration to a concentration of × 10 ¹³ to 1 × 10 ¹⁴ atoms / cm ³ .

As described above, according to the present invention, when growing a silicon single crystal rod doped with nitrogen by the CZ method, the oxygen concentration contained in the single crystal rod is adjusted to 9 to 17 pp.
It is preferable to control it within the range of ma. When growing a silicon single crystal rod, the method of lowering the concentration of oxygen contained in the silicon single crystal rod to the above range may be according to a conventionally used method. For example, the above oxygen concentration range can be easily set by means such as a decrease in the number of rotations of the crucible, an increase in the flow rate of the introduced gas, a decrease in the atmospheric pressure, and a control of the temperature distribution and convection of the silicon melt.

Further, as described above, in the present invention, when growing a silicon single crystal rod doped with nitrogen by the CZ method, the cooling rate during the crystal growth is controlled to 1.0 to 4.5 ° C./min. Is preferred. Actually, such a crystal production condition can be realized by, for example, a method of adjusting the crystal pulling speed to increase or decrease the crystal growth speed. Alternatively, an apparatus capable of cooling the crystal at an arbitrary cooling rate may be provided in the chamber of the CZ method silicon single crystal manufacturing apparatus. As such a cooling device, a device that can cool a crystal by spraying a cooling gas or a method of providing a water-cooling ring at a certain position on the melt surface so as to surround the crystal can be applied. In this case, by adjusting the cooling method and the pulling rate of the crystal, the cooling rate can be set within the above range.

Thus, a silicon single crystal rod doped with nitrogen at a desired concentration, containing oxygen at a desired concentration, and grown at a desired cooling rate in the CZ method can be obtained. This is sliced by a cutting device such as an inner peripheral blade slicer or a wire saw according to a usual method, and then processed into a silicon single crystal wafer through processes such as chamfering, lapping, etching, and polishing. Needless to say, these steps are merely listed as examples, and there may be various other steps such as washing, and the steps are appropriately changed and used according to the purpose, such as a change in the order of the steps or a partial omission.

Then, the silicon single crystal wafer thus obtained is subjected to a heat treatment in a subsequent gettering heat treatment and / or a device manufacturing heat treatment so that the defect-free layer has a depth of 2 to 12 μm and an internal minute defect. The silicon single crystal wafer of the present invention having a density of 1 × 10 ^{8 to} 2 × 10 ¹⁰ pieces / cm ³ can be obtained.
The silicon single crystal wafer of the present invention has a high degree of freedom in device fabrication because the defect-free layer, which is a device fabrication region, is deep, and has a high gettering ability, and thus has a high device yield.

[0048]

EXAMPLES The present invention will now be described specifically with reference to examples and comparative examples of the present invention, but the present invention is not limited to these examples. (Examples and Comparative Examples) The raw material polycrystalline silicon was charged into a quartz crucible having a diameter of 18 inches by the CZ method, and a diameter of 8 mm.
Twelve crystal bars of inch, P type, orientation <100>, and resistivity of 10 Ω · cm were pulled while changing the conditions of nitrogen doping amount, oxygen concentration and cooling rate.

The control of the nitrogen doping amount was performed by previously charging a silicon wafer having a predetermined amount of a silicon nitride film in the raw material. The oxygen concentration was controlled by controlling the crucible rotation during the lifting. The cooling rate was controlled by changing the pulling rate of the single crystal rod and changing the crystal growth rate.

A wafer was cut out from the obtained single crystal rod using a wire saw, chamfered, wrapped, etched and mirror-polished, and the conditions other than the nitrogen doping amount, oxygen concentration and cooling rate were almost the same. A plurality of 12 types of silicon single crystal mirror-surface wafers having a diameter of 8 inches were prepared.

The silicon single crystal wafer thus obtained was subjected to gettering heat treatment. In the gettering heat treatment in this case, the silicon single crystal wafer is heated to 1200 ° C. at a rate of 6 ° C./min and maintained at 1200 ° C. for 60 minutes in an atmosphere composed of 50% hydrogen and 50% argon. This was carried out by cooling at a cooling rate of 3 ° C./min.

Thereafter, the depths of the defect-free layers of these 12 types of silicon single crystal wafers were evaluated. For the evaluation of the depth of the defect-free layer, first, the surface was polished, and a wafer was prepared in which the polishing removal amount from the surface was changed. Then, the SC-1 mixed solution (aqueous ammonia (NH ₄ OH) and aqueous hydrogen peroxide (H ₂ O)
₂ ) and a 1: 1: 20 mixture of ultrapure water) to wash the wafer at a temperature of about 80 ° C. for 1 hour to obtain fine C.
OP is exposed, and the wafer surface is KLA / Tenco
With a SP1 particle measuring device manufactured by R Co., Ltd., the COP (Cr
ystal Originated Particle) was measured by counting the number of COPs. The polishing removal was performed every 1 μm to a depth of 12 μm.

The depth of the defect-free layer is the same as described above.
In the same way, the amount of polishing removed from the surface
The evaluation was also performed by evaluating the withstand voltage quality of the oxide film.
Evaluation of oxide film breakdown voltage quality is based on TZDB (Time Zero Dielec).
tric Breakdown) C-mode yield, specifically phosphorus doping
Polysilicon electrode (oxide film thickness 25 nm, electrode area 8 mm
²) Is prepared, and the judgment current value is 1 mA / cm.^TwoInsulation breakdown evaluated in
A wafer with a breakdown field of 8 MV / cm or more is regarded as a non-defective product.
C-mod is the percentage of non-defective products when 100 electrodes are measured.
e The ratio of non-defective products was determined.

Further, TDDB (Time Dependent Dielect)
ric Breakdown). This is a phosphorus-doped polysilicon electrode (oxide film thickness 25 nm,
An electrode area of 4 mm ² ) was prepared, and the stress current was 0.01 m.
A / cm ² is continuously flowed, and a material that causes dielectric breakdown when the charge amount is 25 C / cm ² or more is regarded as a non-defective product, and is taken as 100% in the wafer surface.
The non-defective rate when the electrodes were measured was defined as the γ-mode non-defective rate. Then, in the evaluation of both TZDB and TDDB, a case where the non-defective rate was 90% or more was determined to be a defect-free layer.

Thereafter, a heat treatment simulating a device heat treatment was applied to these 12 types of silicon single crystal wafers.
In this heat treatment, a silicon single crystal wafer is subjected to a heat treatment at 800 ° C. for 4 hours in a nitrogen atmosphere, and then to a temperature of 1000 ° C.
Was carried out for 16 hours.

Then, the internal minute defect density of these 12 types of silicon single crystal wafers was evaluated. The measurement of the internal minute defect density is based on OPP (Optical Precipitate Profile).
er) method. This OPP method is based on a normal ski type differential interference microscope. First, a laser beam emitted from a light source is separated by a polarizing prism into two beams of linearly polarized light that are orthogonal to each other and have a phase difference of 90 °. From. At this time, when one beam crosses the defect, a phase shift occurs, and a phase difference occurs with another beam. Defects are detected by detecting this phase difference with a polarization analyzer after passing through the back surface of the wafer.

Table 1 shows the measurement results thus obtained. Here, regarding the evaluation of the depth of the defect-free layer, the evaluation based on the number of COPs is that the defect-free layer is evaluated up to a depth where the number of COPs in the wafer surface is less than 100, and the evaluation based on the oxide film breakdown voltage is 90%. % Was evaluated as a defect-free layer.

[0058]

[Table 1]

From Table 1, it can be seen that the wafer prepared from the single crystal grown under controlled nitrogen concentration according to the present invention has a defect-free layer depth lower than the conventional wafer controlled only by oxygen concentration and cooling rate. It can be seen that the density and the density of internal minute defects are significantly improved. FIG. 1 shows the defect-free layer depth as a defect-free layer depth, which shows a lower value among the evaluations based on the number of COPs and the oxide film breakdown voltage. From FIG. 1, it can be seen that the controllable range of the defect-free layer depth and the density of the internal minute defect is much larger in the wafer according to the present invention of the example than in the conventional wafer of the comparative example.

The present invention is not limited to the above embodiment. The above embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the scope of the claims of the present invention. It is included in the technical scope of the invention.

For example, when growing a silicon single crystal rod doped with nitrogen by the Czochralski method in the present invention, it does not matter whether a magnetic field is applied to the melt or not. The Ralski method includes a so-called MCZ method in which a magnetic field is applied.

The above-described embodiment is merely an example of the gettering heat treatment or the device manufacturing heat treatment performed on the silicon single crystal wafer, and can be appropriately changed according to the specifications of the device to be manufactured.

[0063]

According to the present invention, gettering is achieved by growing a silicon single crystal rod doped with nitrogen by the Czochralski method and controlling the nitrogen concentration and oxygen concentration in the CZ crystal and the cooling rate during crystal growth. The depth of the defect-free layer after the heat treatment can be in the range of 2 to 12 μm, and the internal minute defect density after the gettering heat treatment or the device manufacturing heat treatment is as wide as 1 × 10 ⁸ to 2 × 10 ¹⁰ / cm ^3. It can be controlled in a range. Therefore, the silicon single crystal wafer of the present invention has a wide device fabrication area and a high gettering ability, and its industrial utility value is extremely high.

[Brief description of the drawings]

FIG. 1 is a diagram showing a defect-free layer depth and an internal minute defect density of a silicon single crystal wafer at various parameter values.

FIGS. 2A and 2B are diagrams schematically illustrating crystal defects and oxygen precipitates in a silicon single crystal wafer, wherein FIG. 2A is a diagram illustrating a state in a wafer according to the present invention, and FIG. () Is a diagram showing a state of the inside of the wafer of the wafer by the conventional manufacturing method.

FIG. 3 is a diagram showing the relationship between the nitrogen concentration of a silicon single crystal wafer and the width of an OSF region on the surface of the wafer.

FIG. 4 is a diagram showing the relationship between the nitrogen concentration of the wafer and the SF density of the wafer surface when epitaxial growth is performed on the surface of a silicon single crystal wafer.

Claims (10)

[Claims] 1. A silicon single crystal wafer obtained by slicing a silicon single crystal rod grown by doping with nitrogen by the Czochralski method, wherein the silicon single crystal wafer is subjected to a gettering heat treatment or a device manufacturing heat treatment. The depth of the defect-free layer after that is 2 to 12 μm, and the density of internal minute defects after the gettering heat treatment or the device manufacturing heat treatment is 1 × 10 ⁸ to 2 × 10 ¹⁰ / cm ^3. Silicon single crystal wafer. 2. The silicon single crystal wafer according to claim 1, wherein the nitrogen concentration of the silicon single crystal wafer is 1 × 10 ¹² to 1 × 10 ¹⁵ atoms / cm ³ . 3. The silicon single crystal wafer according to claim 1, wherein the nitrogen concentration of the silicon single crystal wafer is 1 × 10 ¹³ to 1 × 10 ¹⁴ atoms / cm ³ . 4. The silicon single crystal wafer according to claim 1, wherein the oxygen concentration of the silicon single crystal wafer is 9 to 17 ppma. 5. A cooling rate of the silicon single crystal rod from 1150 ° C. to 1080 ° C. during crystal growth is 1.0 to 1.0.
The silicon single crystal wafer according to any one of claims 1 to 4, wherein the silicon single crystal wafer is a single crystal rod grown at a controlled temperature of 4.5 ° C / min. 6. A method for producing a silicon single crystal wafer, comprising: growing a silicon single crystal rod doped with nitrogen by a Czochralski method while controlling a nitrogen concentration, an oxygen concentration, and a cooling rate; Slicing and processing into a wafer. 7. When growing a silicon single crystal rod doped with nitrogen by the Czochralski method, the concentration of nitrogen doped into the single crystal rod is 1 × 10 ¹² to 1 × 10 ^15.
7. The method for producing a silicon single crystal wafer according to claim 6, wherein the control is performed at atoms / cm ³ . 8. When growing a silicon single crystal rod doped with nitrogen by the Czochralski method, the concentration of nitrogen doped into the single crystal rod is 1 × 10 ¹³ to 1 × 10 ^14.
7. The method for producing a silicon single crystal wafer according to claim 6, wherein the control is performed at atoms / cm ³ . 9. The method according to claim 6, wherein when growing a silicon single crystal rod doped with nitrogen by the Czochralski method, the concentration of oxygen contained in the single crystal rod is controlled to 9 to 17 ppma. Or any one of claims 8 to
3. The method for producing a silicon single crystal wafer described in the section 1. 10. When growing a silicon single crystal rod doped with nitrogen by the Czochralski method, the cooling rate from 1150 ° C. to 1080 ° C. during the crystal growth of the single crystal rod is 1.0 to 4.0. The method for producing a silicon single crystal wafer according to any one of claims 6 to 9, wherein the control is performed within a range of 5 ° C / min.