JPH11349394A - Nitrogen-doped silicon single crystal wafer having low defect density and it production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a nitrogen-doped silicon single crystal wafer in high productivity by excluding dislocation cluster while remaining excess interstitial silicon atoms over the whole surface or a part of crystal. SOLUTION: A silicon single crystal is grown by Czochralski process by pulling up the crystal while doping the crystal with nitrogen under a condition to hold excess interstitial silicon atoms over the whole area of a part of the crystal. The distribution of defect is shifted to the high-speed side of the pull-up speed and the generation of dislocation cluster ordinarily occuring at an I-rich region is prevented by this process. Accordingly, the controlling tolerance is widened and the control becomes easy when the crystal is pulled up in a region having I-rich region over the whole surface or a part of the crystal and a silicon single crystal having extremely low defect density and free from dislocation cluster even in an I-rich region can be produced in high productivity. Preferably, the amount of doped nitrogen is >=1×10<14> atoms/cm<3> and the oxygen concentration in the crystal is <=1×10<18> 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 single crystal wafer having few crystal defects and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, along with the miniaturization of elements accompanying the high integration of semiconductor circuits such as DRAMs, a silicon single crystal produced by the Czochralski method (hereinafter abbreviated as CZ method) serving as a substrate has been developed. Quality requirements are increasing. In particular, the grown-in (Gr.) Of FPD, LSTD, COP, etc.
There is a defect called “own-in” defect, which is caused by single crystal growth and deteriorates the withstand voltage characteristic of an oxide film and the characteristics of a device, and reduction in the density and size of the defect is regarded as important.

In explaining these defects, first, vacancy (Va) incorporated into a silicon single crystal is used.
vacancy (hereinafter sometimes abbreviated as V) and interstitial silicon point defect called interstitial-Si (hereinafter sometimes abbreviated as I), respectively. What is generally known about factors that determine the concentration in which is taken up will be explained.

In a silicon single crystal, the V region is defined as V
area, which is a region where there are many recesses and holes generated due to lack of silicon atoms.
This is a region in which dislocations and extra silicon atoms are lumped due to the presence of extra silicon atoms, and between the V region and the I region, there is no (small) neutral (less or less) atoms. Neutral (hereinafter sometimes abbreviated as N)). And, the above-mentioned grown-in defect (FPD, LSTD, CO
P, etc.) are generated only when V and I are supersaturated, and it has been found that even if there is a slight bias of atoms, they do not exist as defects if they are not more than saturated.

[0005] The concentration of these two point defects is determined by the relationship between the crystal pulling rate (growth rate) in the CZ method and the temperature gradient G near the solid-liquid interface in the crystal, and is near the boundary between the V region and the I region. Is OSF (oxidation induced stacking fault, Oxidati
on Induced Stacking Foul
The presence of a ring-shaped defect called t) has been confirmed.

[0006] When these defects caused by crystal growth are classified,
For example, when the growth rate is relatively high, such as about 0.6 mm / min or more, grown-in defects such as FPDs, LSTDs, and COPs, which are considered to be caused by voids in which vacancy-type point defects are aggregated, are formed over the entire area in the crystal diameter direction. A region that exists at high density and has these defects is called a V-rich region.
When the growth rate is 0.6 mm / min or less, the above-mentioned OSF ring is generated from the periphery of the crystal due to the decrease in the growth rate, and the L / D is considered to be caused by dislocation loops outside the ring. (Large Dislocati
on: abbreviation for interstitial dislocation loop, LSEPD, LFPD
Etc .: these are also called dislocation clusters) at low density, and the region where these defects are present is called an I-rich region. Further, the growth rate is set to 0.4 mm /
When the speed is reduced to about min or less, the OSF ring aggregates at the center of the wafer and disappears, and the entire surface becomes an I-rich region.

[0007] Recently, a region called an N region outside the OSF ring between the V-rich region and the I-rich region,
It has been discovered that there are regions where neither vacancy-induced FPD, LSTD, or COP nor dislocation loop-induced LSEPD, LFPD exist. This area is outside the OSF ring,
When an oxygen precipitation heat treatment is performed and the contrast of the precipitation is confirmed by X-ray observation or the like, an I-rich region where there is almost no oxygen precipitation and is not rich enough to form dislocation clusters such as LSEPD and LFPD. Side.

In the usual method, the N-region exists obliquely with respect to the direction of the growth axis when the growth rate is reduced. Therefore, the N-region exists only partially in the wafer plane. For this N-region, the Bornkov theory (VVor
onkov; Journal of Crystal
Growth, 59 (1982) 625 to 643), argues that the parameter F / G, which is the ratio of the pulling rate (F) to the temperature gradient (G) in the axial direction of the crystal-solid interface, determines the total concentration of point defects. I have. Considering this, the pulling speed should be constant in the plane, so that G has a distribution in the plane. For example, at a certain pulling speed, the center is located around the N- region in the V-rich region. And I-
Only a crystal that could be a rich region was obtained.

Therefore, recently, the distribution of G in the plane has been improved,
When the N- region existing only obliquely is pulled up, for example, while gradually lowering the pulling speed F, a crystal in which the N- region spreads over the entire horizontal surface at a certain pulling speed can be manufactured. Further, in order to enlarge the crystal of this entire N-region in the length direction, it can be achieved to some extent by pulling while maintaining the pulling speed when the N-region spreads laterally. Also, considering that G changes as the crystal grows, it is corrected and the pulling speed is adjusted so that F / G is kept constant. The crystal serving as a region can be enlarged. This whole N-region crystal has no grown-in defect at all, and has good oxide film breakdown voltage characteristics.

In addition to the above, there is a slow cooling method as a defect reduction method currently performed. This is because, at a relatively high pulling rate, the crystal is pulled in a region called a V-rich region in which vacancies are excessively present, and a temperature band of 1150 to 1080 ° C. In this method, the density of defects is reduced by lengthening the transit time, thereby improving the oxide film breakdown voltage characteristics.

Further, there is a method in which the crystal is pulled in a region where interstitial silicon is excessively present, called an I-rich region, by lowering the pulling speed. According to this method, almost no COP or the like exists. Also, the oxide film withstand voltage characteristics are good. Further, conventionally, a method of doping nitrogen into a V-rich crystal has been performed, and a crystal with extremely small FPD and COP has been manufactured.

[0012]

However, the entire N
In the case where a very low defect region such as a region is to be spread over the entire crystal and the pulling speed F is to be increased, the temperature gradient G in the solid-liquid interface axial direction of the crystal is determined according to Bornkov's theory. However, since it is necessary to make G uniform in the lateral direction of the crystal, and there is a limit in the in-furnace structure (hot zone: HZ) of the crystal growth apparatus, it is necessary to increase the growth rate. There was a limit. Further, the control range of the pulling speed, which is the N-region, is narrow, and it is difficult to expand the N-region in the axial direction of the crystal, which is not suitable for mass production.

Further, it has been confirmed that the V-rich region slow cooling method increases the size of the defect even if the density of the defect is reduced, and has not been a fundamental solution. Furthermore, it is known that a large dislocation loop (dislocation cluster) exists in the I-rich crystal, and it is known that a current leaks through the dislocation in a device, and the device does not function as a PN junction. . Further, when compared at the same oxygen concentration, oxygen precipitation is less likely to occur than the V-rich crystal, and the gettering ability is insufficient.

At first glance, a crystal grown by ordinary CZ method doped with nitrogen (most of V-rich crystals) does not show any grown-in defects, but when evaluated in detail, nitrogen has an effect of suppressing the aggregation of defects. However, it was confirmed that a large number of small defects existed in high density. Further, the oxide film breakdown voltage measurement of this crystal was not so good.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has an extremely low defect density over the entire surface of an I-rich crystal under a high-speed, wide control range and easily controllable manufacturing condition. Accordingly, it is an object of the present invention to obtain a silicon single crystal wafer by the CZ method comprising an I-rich region in which dislocation clusters are eliminated, while maintaining high productivity.

[0016]

Means for Solving the Problems The present invention has been made to achieve the above object, and the invention described in claim 1 of the present invention is directed to a silicon single crystal grown by the Czochralski method. This is a silicon single crystal wafer characterized in that interstitial silicon is excessively present on the entire surface or in a part of the crystal, but dislocation clusters are eliminated.

According to a second aspect of the present invention, there is provided a silicon single crystal wafer grown by the Czochralski method, wherein nitrogen is doped and interstitial silicon is excessively present on the entire surface of the crystal or a partial region thereof. A silicon single crystal wafer characterized by the following.

A third aspect of the present invention is a silicon single crystal wafer grown by the Czochralski method, wherein nitrogen is doped and excess interstitial silicon is present on the entire surface or a part of the crystal. However, this is a silicon single crystal wafer characterized by eliminating dislocation clusters.

According to a fourth aspect of the present invention, there is provided the silicon single crystal wafer according to the first to third aspects, wherein the vacancy-type defects are eliminated from the entire surface of the crystal. it can.

In this case, the concentration of the doped nitrogen is set to 1 × 10 ¹⁴ atoms / cm ³ or more, and the concentration of oxygen in the crystal is set to 1 × 10 atoms / cm ^3.
It can be ¹⁸ atoms / cm ³ or less.

According to a seventh aspect of the present invention, there is provided the silicon single crystal wafer according to any one of the second to sixth aspects, wherein nitrogen on the surface of the wafer is reduced by heat treatment. It is something that is spread.

The method of manufacturing a silicon single crystal wafer is as described in claim 8 of the present invention.
A method for producing a silicon single crystal wafer, comprising: growing a silicon single crystal by the Czochralski method while doping with nitrogen and pulling the silicon single crystal under conditions in which interstitial silicon is excessive in the entire surface or in a part of the crystal. It is.

When the crystal is pulled while doping with nitrogen as described above, the defect distribution shifts to a higher pulling speed, and dislocation clusters that would occur in the I-rich region are eliminated. Therefore, if the crystal is pulled in a region where the entire surface or a part thereof is an I-rich region, an ultra-low defect silicon single crystal which has a wide control range, is easy to control, and excludes dislocation clusters while being an I-rich region. Wafers can be manufactured while maintaining high productivity.

Further, according to the ninth aspect of the present invention, when growing a silicon single crystal by the Czochralski method, the interstitial silicon becomes excessive over the entire surface or a part of the region while doping with nitrogen, and A method for producing a silicon single crystal wafer, characterized in that the silicon single crystal wafer is pulled up under conditions that do not cause vacancy defects on the entire surface. By doing so, the so-called V-rich region where vacancy-type defects exist or O
Since the formation of the SF ring is eliminated, the crystal can be easily pulled in a region where the entire surface or a part is the I-rich region.

In addition, according to the present invention, when growing a silicon single crystal by the Czochralski method, the pulling rate is set to F [mm / min] and the temperature is set to 1400 ° C. from the melting point of silicon. When the average value of the temperature gradient in the crystal in the direction of the pulling axis is expressed by G [° C./mm], the distance D [mm] from the center of the crystal to the periphery of the crystal is represented by the horizontal axis, and F /
When pulling a crystal in an I-rich region of a defect distribution diagram showing a defect distribution with the value of G [mm ² / ° C. · min] as a vertical axis, the crystal is pulled while doping with nitrogen. This is a method for producing a silicon single crystal wafer.

As described above, based on the defect distribution diagram of FIG. 1 obtained by analyzing the results of the experiments and investigations, the crystal pulling speed F and the crystal pulling speed F are adjusted so as to be within the I-rich region while doping with nitrogen. If the crystal is pulled by controlling the average value G of the temperature gradient in the crystal in the pulling axis direction between the melting point of silicon and 1400 ° C., the pulling speed shifts to a higher speed side and dislocation clusters are eliminated. Therefore, if pulling is performed under the conditions for manufacturing an I-rich region crystal while doping with nitrogen, the width of control is wide, control is easy, and pulling can be performed at a relatively high speed. A crystal wafer can be manufactured.

That is, according to this method, an interstitial silicon is excessively present on the entire surface of the crystal or in a part of the region, but a silicon single crystal wafer from which dislocation clusters are eliminated or nitrogen is doped, and Alternatively, a silicon single crystal wafer or nitrogen that is excessively present in some regions is doped with nitrogen, and interstitial silicon is excessively present in the entire crystal surface or in some regions, but dislocation clusters are eliminated. A silicon single crystal wafer can be manufactured. These silicon single crystal wafers are excellent in oxide film breakdown voltage characteristics, and have such characteristics that leakage-type failure does not occur.

In this case, as described in claim 11,
When growing a crystal by the Czochralski method, it is desirable to apply a magnetic field. Thus, the so-called MC
According to the Z method, the pulling speed shifts to a higher speed side in synergy with the effect of nitrogen doping. Therefore, if the pull-up is performed under the conditions for manufacturing the I-rich region crystal while applying a magnetic field and doping with nitrogen, the control range is wide, the control is easy, the pulling speed is increased, and the productivity is maintained. A low-defect silicon single crystal wafer can be manufactured.

As described in claim 12, it is preferable that the concentration of nitrogen to be doped is 1 × 10 ¹⁴ atoms / cm ³ or more. This reduces the formation of dislocation clusters in the I-rich crystal by 1 × 10
^This is because it is desirable to set it to ¹⁴ atoms / cm ³ or more.

Further, as described in claim 13, it is preferable that the oxygen concentration in the crystal is 1 × 10 ¹⁸ atoms / cm ³ or less. As described above, when the oxygen content is low, the formation of crystal defects can be further suppressed, and abnormal oxygen precipitation during heat treatment can be reduced.

Next, according to a fourteenth aspect of the present invention, a silicon single crystal wafer obtained by the method according to the eighth to thirteenth aspects is subjected to a heat treatment to remove nitrogen on the wafer surface. This is a method for manufacturing a silicon single crystal wafer to be diffused. By doing so, there is no nitrogen on the wafer surface, and abnormal oxygen precipitation can be prevented. Further, since nitrogen is contained in the bulk portion of the wafer, the precipitation of oxygen is promoted, and a wafer having a sufficient intrinsic gettering effect (IG effect) can be manufactured.

In this case, as described in claim 15,
The heat treatment is performed by a rapid heating / rapid cooling device [hereinafter, RTA
(Rapid Thermal Anneler) device]. This apparatus is a single-wafer type automatic continuous heat treatment apparatus, and performs heating and cooling before and after the heat treatment in several seconds to several hundred seconds. Effective heat treatment for a short time of 100 seconds can be performed.

Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto. Prior to the explanation, each term will be explained in advance. 1) FPD (Flow Pattern Defec)
t) means that a wafer is cut out from a silicon single crystal rod after growth, the strained layer on the surface is removed by etching with a mixed solution of hydrofluoric acid and nitric acid, and then K ₂ Cr ₂ O ₇ , hydrofluoric acid and water are mixed. Pits and ripples are produced by etching the surface with the liquid (Secco etching). This ripple pattern is called FPD, and the higher the FPD density in the wafer surface, the more the failure of the oxide film breakdown voltage increases (JP-A-4-19234).
No. 5).

2) SEPD (Secco Etch P)
it Defect) is the same as Secco as FPD
When etching is performed, a flow pattern (flow pat)
The one with tern) is called FPD, and the one without flow pattern is called SEPD. Among them, a large SEPD (LSEPD) of 10 μm or more is considered to be caused by a dislocation cluster. When a dislocation cluster exists in a device, a current leaks through the dislocation and the device does not function as a PN junction.

3) LSTD (Laser Scatte)
In “Ring Tomography Defect”, a wafer is cut out from a silicon single crystal rod after growth, and a strained layer on the surface is removed by etching with a mixed solution of hydrofluoric acid and nitric acid, and then the wafer is cleaved. By irradiating infrared light from the cleavage plane and detecting light emitted from the wafer surface, scattered light due to defects existing in the wafer can be detected. The scatterers observed here have already been reported in academic societies and the like, and are regarded as oxygen precipitates (JJAP Vol. 32, P3679, 19).
93). Recent studies have also reported that it is an octahedral void.

4) COP (Crystal Origin)
A “nated particle” is a defect that causes deterioration of the oxide film breakdown voltage at the center of the wafer, and
The defect that becomes FPD in the co-etch is SC-1 cleaning (N
In the case of washing with a mixed solution of H ₄ OH: H ₂ O ₂ : H ₂ O = 1: 1: 10), it works as a selective etching solution and becomes COP. The diameter of the pit is 1 μm or less and is examined by a light scattering method.

5) L / D (Large Disloca)
tion: abbreviation for interstitial dislocation loop)
D, LFPD, etc., which are considered to be caused by dislocation loops, are also called dislocation clusters or giant dislocation loops. LSEPD is the SEPD
Among them, those having a size of 10 μm or more are referred to. Also, LF
PD refers to the above-mentioned FPD having a large size of the tip pit of 10 μm or more, which is also considered as a dislocation cluster caused by a dislocation loop.

The present inventors have previously disclosed in Japanese Patent Application No. 9-19994.
As proposed in No. 5, a detailed investigation was made on the vicinity of the boundary between the V region and the I region with respect to silicon single crystal growth by the CZ method.
The number of D, LSTD, COP is extremely small, and LSEPD
It has been found that there is a neutral region (N-region) that does not exist.

Therefore, it was conceived that if the N- region could be spread over the entire surface of the wafer, the point defects could be greatly reduced, and in the relationship between the growth (pulling) speed and the temperature gradient, the following conditions were obtained: Since the pulling speed is almost constant, the main factor that determines the concentration distribution of point defects in the plane is the temperature gradient. In other words, it is a problem that there is a difference in the temperature gradient in the axial direction in the wafer plane, and if this difference can be reduced, it is found that the difference in the concentration of point defects in the wafer plane can be reduced. The difference between the temperature gradient Gc and the temperature gradient Ge around the crystal is represented by ΔG = (Ge−Gc) ≦ 5 ° C./cm
If the pulling speed is adjusted by controlling the temperature in the furnace so as to obtain a defect-free wafer in which the entire surface of the wafer is composed of an N region, it has become possible to obtain a wafer without defects. However, in this method, there is a limit in the structure of HZ, and there is a limit in increasing the growth rate.

On the other hand, when doping with a light element impurity such as nitrogen, the influence of the impurity on the growth-in defect distribution is as follows. Are reported to be less likely to occur. In addition, it has been pointed out that doping nitrogen into a silicon single crystal suppresses the aggregation of atomic vacancies in silicon and lowers the crystal defect density (T. Abe and H. Takeno, Mat. Res. Soc. .S
ymp.Proc.Vol.262,3,1992).

Therefore, for nitrogen doping, a crystal pulling apparatus having a normal furnace structure having a large ΔG, which is the difference in temperature gradient between the center of the crystal and the periphery of the crystal, is used. As a result of investigation, the following findings were newly obtained, and various conditions were established to complete the present invention.

That is, it has been found that the doping with nitrogen shifts the pulling speed related to the defect distribution to the high-speed side and eliminates dislocation clusters that would be generated in the I-rich region. This is because the crystal is grown by changing the pulling rate while doping with nitrogen, a wafer is cut out from the obtained single crystal rod, glow-in defects are measured, and thermal oxidation treatment is performed to determine whether or not OSF rings are generated. It was found as a result of checking. The defect distribution diagrams of FIGS. 1 and 5 were created based on the results.

FIG. 1 shows the distribution of defective crystals when a silicon single crystal having a diameter of 6 inches and a nitrogen doping amount was set at 1 × 10 ¹⁴ atoms / cm ³ while the pulling speed was lowered. The directional position is shown on the horizontal axis, and the F / G value is shown on the vertical axis. As is clear from FIG. 1, the boundary excluding the V-rich region is 0.237 mm ² / ° C. * between the center of the crystal and a position up to about 50 mm from the center.
It gradually rises from min and is on the line where the F / G value is increased from this position to the outer periphery. Also, N-region / I-
Although the boundary with the rich region is not clear in the case of nitrogen doping, ΔG is large, so that the entire surface does not become the N-region as shown in FIG. 5 and a part of the periphery is an I-rich region. That is, as described in FIG. 1, the radial direction of one wafer, that is, the crystal follows the F / G line shown by the broken line. Therefore, in order to maximize the use of a region in which the whole or a part of the wafer is an I-rich region excluding the V-rich region, 0.237 mm ²
/ ° C · min or less.

FIG. 5 shows the distribution of defective crystals when a silicon single crystal having a diameter of 6 inches and a nitrogen doping amount is set to 1 × 10 ¹⁴ atoms / cm ³ when the pulling rate is lowered while the pulling rate is low. The directional position is shown on the horizontal axis, and the pulling speed is shown on the vertical axis. From Figure 5, the pulling speed is 0.84
mm / min or less (in FIG. 1, the F / G value is 0.237 mm
² / ° C./min or less), the V-rich region is reduced. It was confirmed that no dislocation cluster was present in the outer I-rich region. The boundary line of the N-region / I-rich region (see FIG. 6) that appears when the substrate is pulled without normal nitrogen doping could not be confirmed in the case of nitrogen doping. When the HZ is used, when the V-rich region is reduced, the periphery thereof seems to be an I-rich region. Also, no pits such as extremely small COPs exist, and the oxide breakdown voltage characteristic of this wafer is 10% in C-mode non-defective rate.
It was 0%.

In this example, the pulling speed at which the V-rich region disappears and the entire surface or a part of the region becomes the I-rich region is 0.84 mm / min or less, and the pulling speed in the case of no nitrogen doping is 0.8 mm / min. Compared with 6 mm / min or less (see FIG. 6), it can be seen that the speed is increased by about 40%. Moreover, dislocation clusters originally occurring in this region were not detected. The reason why the N − region is formed in the outer peripheral portion of the crystal pulled under such conditions is that interstitial silicon diffuses outward in a cooling process after the crystal growth.
Since there is no need to consider ΔG, if the crystal is quenched as quickly as possible and HZ having a large G is used and the defect distribution shift effect of nitrogen doping is used, the speed can be further increased. Therefore, if the wafer is pulled under the conditions for manufacturing the I-rich region while doping with nitrogen, the wafer which is an I-rich region on the entire surface or a part of the region and has extremely low defects, particularly, a wafer having no dislocation clusters can be easily and quickly formed. It can be manufactured, and yield and productivity can be improved and cost can be reduced.

In the present invention, a silicon single crystal rod doped with nitrogen by the CZ method may be grown by a known method, for example, as described in Japanese Patent Application Laid-Open No. 60-251190. That is, the CZ method is a method in which a seed crystal is brought into contact with a melt of a polycrystalline silicon raw material contained in a quartz crucible, and is slowly pulled up while rotating to grow a silicon single crystal rod having a desired diameter. By pulling nitride in a quartz crucible in advance, putting nitride in a silicon melt, or setting the atmosphere gas to an atmosphere containing nitrogen, nitrogen can be doped into the pulled crystal. . At this time, the doping amount in the crystal can be controlled by adjusting the amount of the nitride, the concentration of the nitrogen gas, the introduction time, and the like. As described above, when a single crystal rod is grown by the CZ method, the generation of crystal defects introduced during crystal growth can be suppressed by doping with nitrogen.

In this case, a magnetic field may be applied when growing the crystal by the CZ method. Thus, the so-called M
According to the CZ method, the pulling speed shifts to a higher speed side in synergy with the effect of nitrogen doping. As the magnetic field applied to the silicon melt, a horizontal magnetic field, a vertical magnetic field, a cusp magnetic field, or the like is used. This is because the strength of the applied magnetic field is preferably 2000 G or more, and more preferably 3000 G or more, and if it is less than 2000 G, the effect of applying the magnetic field is small. Therefore, by pulling up under the conditions for manufacturing the I-rich region crystal while applying a magnetic field and doping with nitrogen, a silicon single crystal having a very low defect width with a wide control range, easy control and high productivity can be maintained. Wafers can be manufactured.

In the present invention, the doping amount of nitrogen is 1 × 1
It is preferably at least 0 ¹⁴ atoms / cm ³ . In this case, if a little nitrogen is doped, the pulling speed shifts to a high speed side, and the effect of nitrogen doping is very large, and it is found that the effect is linear with respect to the doping amount. By setting it to 1 × 10 ¹⁴ atoms / cm ³ or more, the effect of suppressing the formation of crystal defects was large, and dislocation clusters could be eliminated.

The oxygen concentration in the crystal is 1 × 10 ¹⁸ at.
oms / cm ³ or less. As described above, if the oxygen content is low, the formation of crystal defects can be further suppressed, and abnormal oxygen precipitation during heat treatment can be prevented.

As described above, the interstitial silicon is excessively present on the entire surface or a part of the crystal, but a silicon single crystal wafer from which dislocation clusters are eliminated, or doped with nitrogen, and Silicon single crystal wafers with excessive interstitial silicon in the region or silicon doped with nitrogen, and interstitial silicon excessive in the whole surface or in some regions but dislocation clusters eliminated Wafers can be manufactured stably with high productivity.

In this case, the excess nitrogen in the crystal may be obtained by subjecting a silicon single crystal wafer obtained by nitrogen doping to a heat treatment to outwardly diffuse nitrogen on the wafer surface. In this way, a wafer having extremely few crystal defects on the wafer surface can be obtained. Also,
Since nitrogen is contained in the bulk portion of the wafer, precipitation of oxygen is promoted, and a wafer having a sufficient IG effect (intrinsic gettering effect) can be manufactured.

As a specific heat treatment condition for outwardly diffusing nitrogen on the wafer surface, the heat treatment is preferably performed at a temperature of 900 ° C. to the melting point of silicon or lower. By performing the heat treatment in such a temperature range, nitrogen in the wafer surface layer can be sufficiently diffused outward, and oxygen can also be diffused outward at the same time, so that defects caused by oxygen precipitates in the surface layer can be reduced. This is because generation can be almost completely prevented. On the other hand, in the bulk portion, oxygen precipitates can be grown by the above-described heat treatment.
A wafer having the G effect can be obtained. In particular, in the present invention, in the bulk portion, the precipitation of oxygen is promoted by the presence of nitrogen, so that the IG effect is high.
G effect can be exhibited.

In this case, it is desirable that the heat treatment is performed by a rapid heating / rapid cooling device. This device is a so-called R
It is called a TA device and is a single-wafer type automatic continuous heat treatment device.Because heating and cooling before and after heat treatment are performed in a few seconds to several hundred seconds, without giving a long-term heat history with harmful effects to the wafer, An effective heat treatment for a short time of several seconds to several hundred seconds can be performed.

The heat treatment for diffusing nitrogen on the wafer surface outward is preferably performed in an atmosphere of oxygen, hydrogen, argon or a mixture of these. By performing heat treatment in such a gas atmosphere, without forming a harmful surface film on the silicon wafer,
It is possible to efficiently diffuse nitrogen outward. In particular, it is more preferable to perform the high-temperature heat treatment in a reducing atmosphere such as an atmosphere of hydrogen, argon, or a mixture thereof because crystal defects on the wafer surface are easily eliminated.

Thus, the CZ doped with nitrogen is
A silicon single crystal wafer according to the present invention, wherein nitrogen on the surface of the silicon single crystal wafer is diffused outward by heat treatment.

[0056]

Embodiments of the present invention will be described below in detail with reference to the drawings. First, a configuration example of a single crystal pulling apparatus using the CZ method used in the present invention will be described with reference to FIG. As shown in FIG. 3, the single crystal pulling apparatus 30 includes a pulling chamber 31, a crucible 32 provided in the pulling chamber 31, a heater 34 disposed around the crucible 32, and a crucible for rotating the crucible 32. Holding shaft 33
And its rotation mechanism (not shown), and a silicon seed crystal 5.
, A wire 7 for pulling up the seed chuck 6, and a winding mechanism (not shown) for rotating or winding the wire 7. Crucible 32
Is provided with a quartz crucible on the side for containing the silicon melt (hot water) 2 inside, and a graphite crucible on the outside thereof. A heat insulating material 3 is provided around the outside of the heater 34.
5 are arranged. Also, spraying cooling gas,
A cylindrical cooling device (not shown) that blocks the radiant heat to cool the single crystal may be provided. Separately, recently, a magnet (not shown) is installed outside the pulling chamber 31 in the horizontal direction, and a magnetic field in the horizontal direction or the vertical direction is applied to the silicon melt 2 to suppress the convection of the melt and obtain a single crystal. In many cases, a so-called MCZ method is used to achieve stable growth.

Next, a method of growing a single crystal using the above-described single crystal pulling apparatus 30 will be described. First, a high-purity polycrystalline silicon material is melted in a crucible 32 at a melting point (about 1420 °).
C) Heat to melt above. At this time, for example, a silicon wafer with a nitride film is charged in order to dope nitrogen. Next, by unwinding the wire 7, the tip of the seed crystal 5 is brought into contact with or immersed substantially in the center of the surface of the melt 2.
Thereafter, the crucible holding shaft 33 is rotated in an appropriate direction, and at the same time, the wound seed crystal 5 is pulled up while rotating the wire 7, thereby starting single crystal growth. Since then
By appropriately adjusting the pulling speed and the temperature, a substantially cylindrical nitrogen-doped single crystal rod 1 can be obtained.

Next, the obtained nitrogen-containing silicon single crystal rod is sliced, and the wafer obtained by subjecting the wafer to a predetermined wafer processing is subjected to a heat treatment to diffuse nitrogen on the wafer surface outward. In the present invention, a device capable of rapid heating / cooling is used for this heat treatment. This R
Examples of the TA device include a device such as a lamp heater using heat radiation. Other commercially available devices such as SHS-2800 manufactured by AST are not particularly complicated and expensive.

FIG. 4 shows an example of the RTA apparatus used in the present invention. The heat treatment apparatus 20 shown in FIG. 4 has a bell jar 21 made of, for example, silicon carbide or quartz, and heats a wafer in the bell jar 21. The heating is performed by heaters 22 and 22 ′ arranged to surround the bell jar 21. The heater is divided in the vertical direction, so that the power supplied independently can be controlled. Of course, the heating method is not limited to this, and may be a so-called radiant heating or high-frequency heating method. Heater 22,2
A housing 23 for shielding heat is arranged outside 2 '.

A water cooling chamber 24 and a base plate 25 are disposed below the furnace, and seal the inside of the bell jar 21 from the outside air. The silicon wafer 28 is held on a stage 27, and the stage 27 is attached to the upper end of a support shaft 26 which can be moved up and down by a motor 29. The water cooling chamber 24 is provided with a wafer insertion port (not shown) that can be opened and closed by a gate valve so that the wafer can be taken in and out of the furnace from the lateral direction. Further, the base plate 25 is provided with a gas inlet and an outlet, so that the gas atmosphere in the furnace can be adjusted.

The heat treatment for rapidly heating and rapidly cooling the nitrogen-containing silicon wafer by the above-described heat treatment apparatus 20 is performed as follows. First, the heaters 22 and 2
The inside of the bell jar 21 is heated to a desired temperature of, for example, 900 ° C. to the melting point of silicon by 2 ′, and is maintained at that temperature. If the supply power is controlled independently for each of the divided heaters, a temperature distribution can be provided in the bell jar 21 along the height direction. Therefore, the processing temperature of the wafer can be determined by the position of the stage 27, that is, the insertion amount of the support shaft 26 into the furnace. As the heat treatment atmosphere, oxygen, hydrogen, argon, or a mixed gas thereof is used.

When the inside of the bell jar 21 is maintained at the desired temperature, the wafer is inserted from the insertion port of the water cooling chamber 24 by a wafer handling device (not shown) disposed adjacent to the heat treatment device 20 and is made to stand by at the lowermost position. A wafer is placed on the stage 27, for example, via a SiC boat. At this time, since the water-cooling chamber 24 and the base plate 25 are water-cooled, the temperature of the wafer does not rise at this position.

When the mounting of the wafer on the stage 27 is completed, the support shaft 2 is immediately driven by the motor 29.
6 into the furnace, the stage 27
The temperature is raised to a desired temperature position from 0 ° C. to the melting point of silicon, and a high-temperature heat treatment is applied to the silicon wafer on the stage. In this case, the movement from the lower end position of the stage in the water cooling chamber 24 to the desired temperature position takes, for example, only about 20 seconds, so that the wafer is rapidly heated.

Then, the stage 27 is moved to a desired temperature position.
By stopping for a predetermined time (several seconds to several hundred seconds), the wafer can be subjected to high-temperature heat treatment for the stop time. After the predetermined time has elapsed and the high-temperature heat treatment has been completed, the stage 27 is lowered by immediately pulling out the support shaft 26 from the furnace by the motor 29 to lower the water-cooling chamber 24.
At the lower end position. This lowering operation can be performed, for example, in about 20 seconds. The wafer on stage 27
Since the water cooling chamber 24 and the base plate 25 are water-cooled, they are rapidly cooled. Finally, the heat treatment is completed by taking out the wafer with a wafer handling device. Further, when there is a wafer to be heat-treated, the temperature of the heat treatment apparatus 20 is not lowered, so that the wafers can be charged one after another to perform the heat treatment continuously.

[0065]

EXAMPLES Hereinafter, specific embodiments of the present invention will be described with reference to examples, but the present invention is not limited to these. (Embodiment) A 20-inch quartz crucible is charged with 60 kg of raw material polycrystalline silicon using a pulling apparatus 30 shown in FIG. 3, and a silicon single crystal rod having a diameter of 6 inches and an orientation of <100> is pulled at an average pulling rate of 1.20 to 1.20. Pulling was carried out while lowering to 0.40 mm / min.
cm). The temperature of the silicon melt was about 1420 ° C., the furnace structure (HZ) was a normal one, and no special consideration was given to the temperature gradient in the crystal axis direction. Nitrogen doping amount is 1 × 10 ¹⁴
atoms / cm ³ and the oxygen concentration is 7 to 10 ppm
a (JEIDA). And the pulling speed is 1.0
0.3 mm / min (F / G value at the center of the crystal is 0.2
82 to 0.084 mm ² / ° C. · min) and pulled up.

A wafer is cut out from the obtained single crystal rod and mirror-finished to produce a mirror-finished silicon single crystal wafer, and a grown-in defect (FPD, LEP (L
SEP, LFPD)). In addition, thermal oxidation treatment was performed to check for the occurrence of an OSF ring. Based on the results, the defect distribution diagrams of FIGS. 5 and 1 were created. FIG.
From V- at a pulling speed of 0.84 mm / min or less (F / G value of 0.237 mm ² / ° C · min or less in FIG. 1).
It can be seen that the rich area has been reduced. It was confirmed that no dislocation cluster was present in the outer I-rich region. N-region / I-rich region boundary that appears when pulling up without normal nitrogen doping (see FIG. 6)
Could not be confirmed in the case of nitrogen doping. Also, no pits such as extremely small COPs were present, and the oxide film breakdown voltage characteristic of this wafer was 100% in terms of the C-mode non-defective rate.

(Comparative Example) As a comparative example, pulling was performed under exactly the same conditions as in the example except that the pulling was performed while lowering the pulling speed to 0.7 to 0.4 mm / min without nitrogen doping. As a result, the defect distribution diagrams shown in FIGS. 6 and 2 were obtained. As is clear from FIG. 6, in order to reduce the V-rich region, the pulling speed was as low as 0.6 mm / min (F / G: 0.157 mm ² / ° C. · min in FIG. 2). . Moreover, dislocation clusters were detected in this region.

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, in the above embodiment, the diameter 6
The case of growing an inch silicon single crystal has been described by way of example, but the present invention is not limited to this, and the crystal is grown while doping with nitrogen while pulling up under the condition that the interstitial silicon is excessive on the entire surface of the crystal. Can be applied to a silicon single crystal having a diameter of 8 to 16 inches or more.

[0070]

As described above, according to the present invention,
When the crystal is pulled under the condition that the interstitial silicon becomes excessive over the entire surface of the crystal while doping with nitrogen, the pulling speed of the I-rich region can be shifted to a higher speed side, and the dislocation clusters in the I-rich region can be shifted. And a very low defect crystal can be stably manufactured with high productivity and high yield. Furthermore, by subjecting this crystal to heat treatment, nitrogen diffuses outward in the vicinity of the surface, and oxygen precipitates sufficiently in the bulk for gettering by nitrogen, and a silicon single crystal wafer with excellent oxide film breakdown voltage characteristics can be produced with high productivity. And can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a distribution diagram of various defects in a nitrogen-doped silicon single crystal of the present invention, where the horizontal axis represents the radial position of the crystal and the vertical axis represents the F / G value.

FIG. 2 is a diagram illustrating various defect distributions in a case where a horizontal axis represents a radial position of a crystal in a crystal and a vertical axis represents an F / G value in a conventional pulling method.

FIG. 3 is a schematic explanatory view of a single crystal pulling apparatus by a CZ method used in the present invention.

FIG. 4 is a schematic explanatory view showing one example of a rapid heating / rapid cooling device used in the present invention.

FIG. 5 is a diagram showing various defect distributions in a nitrogen single crystal of silicon of the present invention, where the horizontal axis represents the radial position of the crystal and the vertical axis represents the pulling rate.

FIG. 6 is a diagram showing various defect distributions in a case where a horizontal axis represents a radial position of a crystal in a crystal and a vertical axis represents a pulling speed in a conventional pulling method.

[Explanation of symbols]

1 ... grown single crystal rod, 2 ... silicon melt, 3 ... hot surface, 4 ...
Solid-liquid interface, 5: seed crystal, 6: seed chuck, 7: wire, 30: single crystal pulling device, 31: pulling chamber, 32 ...
Crucible, 33: crucible holding shaft, 34: heater, 35: heat insulating material. 20: heat treatment apparatus, 21: bell jar, 22, 2
2 ': heater, 23: housing, 24: water cooling chamber, 25: base plate, 26: support shaft, 27
... stage, 28 ... silicon wafer, 29 ... motor.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Shozo Muraoka 2-3-1-1, Isobe, Annaka-shi, Gunma Prefecture Semiconductor Isobe Laboratory, Shin-Etsu Semiconductor Co., Ltd.

Claims (15)

[Claims] 1. A silicon single crystal wafer grown by the Czochralski method, wherein interstitial silicon is excessively present on the entire surface of the crystal or in a part of the crystal, but dislocation clusters are excluded. Silicon single crystal wafer. 2. A silicon single crystal wafer grown by the Czochralski method, wherein the wafer is doped with nitrogen.
A silicon single crystal wafer characterized in that interstitial silicon is excessively present on the entire surface or a part of the crystal. 3. A silicon single crystal wafer grown by the Czochralski method, wherein the wafer is doped with nitrogen.
A silicon single crystal wafer characterized in that interstitial silicon is excessively present on the entire surface or in a part of the crystal, but dislocation clusters are eliminated. 4. The silicon single crystal wafer according to claim 1, wherein vacancy-type defects are eliminated from the entire surface of the crystal. 5. The method according to claim 1, wherein said doped nitrogen concentration is 1 × 10 ^14.
a silicon single crystal wafer according to any one of claims 2 to 4, characterized in that it is atoms / cm ³ or more. 6. The oxygen concentration in the crystal is 1 × 10 ¹⁸ atoms.
/ Cm ³ or less, the silicon single crystal wafer according to any one of claims 1 to 5, wherein 7. The silicon single crystal wafer according to claim 2, wherein nitrogen on the wafer surface is outwardly diffused by heat treatment. Single crystal wafer. 8. A method of growing a silicon single crystal by the Czochralski method, wherein the silicon single crystal is pulled under nitrogen under a condition that the interstitial silicon becomes excessive over the entire surface or a part of the crystal while doping with nitrogen. A method for producing a crystal wafer. 9. When growing a silicon single crystal by the Czochralski method, interstitial silicon is excessive in the entire crystal or in a part of the crystal while doping with nitrogen, and vacancy-type defects do not occur in the entire crystal. A method for producing a silicon single crystal wafer, wherein the wafer is pulled under conditions. 10. When growing a silicon single crystal by the Czochralski method, the pulling speed is set to F [mm / mi.
n], and the average value of the temperature gradient in the crystal in the pulling axis direction from the melting point of silicon to 1400 ° C. is represented by G [° C./mm]. When the crystal is pulled in the I-rich region of the defect distribution diagram showing the defect distribution with the value of F / G [mm ² / ° C. · min] as the axis and the value of F / G [mm ² / ° C. · min], the crystal is pulled while doping with nitrogen. A method for producing a silicon single crystal wafer, comprising: 11. The method of manufacturing a silicon single crystal wafer according to claim 8, wherein a magnetic field is applied when growing the crystal by the Czochralski method. 12. The nitrogen concentration for doping is 1 × 10 ^14.
The method for producing a silicon single crystal wafer according to any one of claims 8 to 11, wherein the density is set to atoms / cm ³ or more. 13. An oxygen concentration in a crystal of 1 × 10 ¹⁸ atoms.
13. The method for producing a silicon single crystal wafer according to claim 8, wherein the silicon single crystal wafer is set to s / cm ³ or less. 14. A silicon single crystal wafer obtained by the method according to any one of claims 8 to 13, wherein the silicon single crystal wafer is subjected to heat treatment to diffuse nitrogen on the wafer surface outward. A method for producing a single crystal wafer. 15. The method for producing a silicon single crystal wafer according to claim 14, wherein the heat treatment is performed by a rapid heating / cooling device.