JP6927150B2 - Method for manufacturing silicon single crystal - Google Patents

Description

The present invention relates to a method for producing a silicon single crystal, an epitaxial silicon wafer, and a silicon single crystal substrate.

In recent years, semiconductor devices (Logic, NAND, DRAM, etc.) that have been miniaturized have two major problems.

One is that even extremely small defects near the wafer surface can cause device defects, so it is necessary to manufacture a high-quality wafer with few or no defects near the surface, which is the device operating region.

The other is the formation of BMD (Bulk Micro Defect), which is a gettering site for impurity metals, which was conventionally sufficiently formed during the device process due to the effect of the process becoming colder and shorter. It is difficult and causes a decrease in the yield of the device.

The former requirement for defects near the wafer surface is a V-rich region having a COP (Crystal Organized Particle) due to vacancies and an R-OSF region in which ring-shaped oxidation-induced stacking defects occur during thermal oxidation. Low / defect-free crystalline silicon single crystal substrates manufactured in the N (Neutral) region that do not contain any dislocation loops or dislocation clusters due to interstitial silicon, or epitaxial silicon wafers that form defect-free layers on the substrate. , There are annealed wafers.

Of these, the annealed wafer has a problem that the post-processing time required to form the defect-free layer is long, it is not suitable for mass supply, and the cost tends to be high.

The epitaxial silicon wafer can form a defect-free layer in a relatively short time after treatment, but it costs an additional cost as compared with a silicon single crystal substrate having a low / defect-free crystal.

Further, in the epitaxial silicon wafer, in order to offset the additional cost of post-processing, it is common to use a highly productive V-rich crystal in which the crystal is grown at a higher speed than the low / defect-free crystal.

Nitrogen doping is known to be effective in increasing BMD, which is a gettering site for impurity metals. However, in the nitrogen-doped V-rich crystal, it is caused by the decrease in BMD density due to the R-OSF region, EP defectation, and the plate-like or rod-like COP when doped at a high nitrogen atom concentration in the outer peripheral portion of the wafer. EP defects can be a problem.

In order to avoid this, there is a method of growing the crystal thicker than the product diameter and removing the portion corresponding to R-OSF by cylindrical grinding, but grinding loss, grinding cost, and time are required. Another method is to use crystals in the N- region that do not contain R-OSF, but it has been difficult to obtain crystals that do not contain R-OSF and have good yield by doping with nitrogen.

Next, the effect of the low-temperature, short-time process due to the latter miniaturization will be described.

For the operation of the MOSFET (source / drain current), the required amount of capacitance (= insulating film relative permittivity x gate area / insulating film thickness) of the gate insulating film must be secured. Therefore, the reduction in the gate area due to the shortening of the gate length due to the progress of miniaturization of the semiconductor device is compensated for by thinning the gate insulating film.

Therefore, in recent semiconductor devices, the gate insulating film has an extremely thin EOT (equivalent oxide film thickness) of about 0.5 nm, and the uniformity of the gate insulating film occupies an important factor for the reliability of device operation. It is supposed to be. Therefore, the film thickness and film quality of the gate insulating film are made uniform by shortening the temperature and time of various heat treatments in the device process.

However, as an adverse effect of lowering the temperature and shortening the time required for the device process, BMD, which is a gettering site for impurity metals, was sufficiently formed in the substrate during the device process, whereas it is low temperature and short. BMD formation is low during the time device process, and the gettering ability for impurity metals is reduced, which may cause a decrease in device yield.

Due to these problems, it is necessary to have a wafer that is easier to form BMD than before in a low-temperature, short-time device process at the tip and can obtain high gettering ability even during a low-temperature, short-time device process. It is said that.

In order to form a sufficient BMD during a low-temperature, short-time device process, as shown in Patent Document 1, vacancy aggregation is suppressed by nitrogen doping, and precipitation nucleation due to residual excess vacancy is formed. It is known that a method of increasing thermally stable (large size) precipitated nuclei by facilitation is effective before the device process.

However, in the epitaxial silicon wafer using the nitrogen-doped V-rich crystal described above as a substrate, the BMD density was lowered due to the R-OSF region, EP defects were formed, and nitrogen was doped at a high concentration on the outer peripheral portion of the wafer. EP defects due to plate-shaped or rod-shaped COP may be a problem.

Japanese Unexamined Patent Publication No. 2001-139396 Japanese Unexamined Patent Publication No. 2000-53497 Japanese Unexamined Patent Publication No. 11-79889 Japanese Unexamined Patent Publication No. 2000-178099 WO2002 / 000969 Japanese Unexamined Patent Publication No. 2000-16897 Japanese Unexamined Patent Publication No. 2000-159595 Japanese Unexamined Patent Publication No. 2008-66357 JP-A-2007-701132 Japanese Unexamined Patent Publication No. 2016-13957

The present invention has been made in view of the above problems, and in a low / defect-free crystalline silicon single crystal substrate in which precipitation (BMD formation) is promoted by nitrogen doping and an epitaxial silicon wafer using the substrate, the low temperature at the tip is used. -It is an object of the present invention to provide a method for producing a silicon single crystal, which enables sufficient BMD formation even in a short-time device process and can produce a wafer having a high gettering ability with a high yield.

In order to solve the above problems, the present invention is a method for growing a silicon single crystal by pulling it up under the condition that the entire surface of the crystal is in the N- region by the Czochralski method, and the silicon single crystal is grown. At that time, nitrogen was ^{doped at a nitrogen concentration of 2 × 10 13} atoms / cm ³ or more and 3.2 × 10 ¹⁴ atoms / cm ³ or less, and the temperature gradient Gc and the crystal at the center of the crystal in the pulling axis direction of the silicon single crystal. The ratio of the temperature gradient Ge of the peripheral portion (outer peripheral portion of the crystal) is set to Ge / Gc> 1, and the Ge / Gc is gradually increased according to the increase in nitrogen concentration due to segregation during pulling of the silicon single crystal. Provided is a method for producing a silicon single crystal, which is characterized in that the size of the silicon single crystal is increased.

In such a method for producing a silicon single crystal, by doping nitrogen at a high concentration, the number of thermally stable large-sized precipitated nuclei is increased, and high BMD is formed even in a low-temperature, short-time device process. Silicon that avoids the R-OSF region even in the wide nitrogen concentration range of the entire crystal length by correcting and adjusting the defect distribution change caused by the high nitrogen concentration due to segregation during crystal growth while achieving the ability (gettering ability). A single crystal can be produced.

At this time, the Ge / Gc is adjusted so as to control the distance between the heat shield arranged directly above the raw material melt in the quartz crucible and the liquid level of the raw material melt, and to surround the quartz crucible. The position of the heater is lowered with respect to the liquid level of the raw material melt, the magnetic field strength of the magnetic field applying device arranged outside the main chamber of the silicon single crystal manufacturing device is weakened, and the above. It is preferable to lower the position of the magnetic field applying device by any one or a combination of two or more.

With such an adjustment method of Ge / Gc, since the manufacturing apparatus is not significantly changed, it is possible to easily adjust Ge / Gc.

At this time, when the Ge / Gc is adjusted by controlling the distance between the heat shield and the liquid surface of the raw material melt, the entire surface of the crystal becomes an N-region when nitrogen is not doped. When the distance between the heat shield and the liquid level of the raw material melt under the conditions is D, the distance D'between the heat shield and the liquid level of the raw material melt when nitrogen is doped is set to nitrogen. It is preferable to change the concentration so that D'/ D = 0.94-nitrogen concentration / (2.41 × 10 ^{15) gives D'.}

In such a Ge / Gc adjusting method, Ge / Gc is adjusted simply and accurately by adjusting the distance between the heat shield and the liquid level of the raw material melt according to the nitrogen concentration. Therefore, Ge / Gc can be adjusted more easily.

At this time, when the obtained D'is larger than 20 mm, the Ge / Gc is adjusted by setting the distance between the heat shield and the liquid surface of the raw material melt to the obtained D'. When the obtained D'is 20 mm or less, the distance between the heat shield and the liquid surface of the raw material melt is set to 20 mm, and the position of the heater arranged so as to surround the quartz rut is set. Lowering the level of the raw material melt with respect to the liquid level, weakening the magnetic field strength of the magnetic field applying device arranged outside the main chamber of the silicon single crystal manufacturing device, and setting the position of the magnetic field applying device. It is preferable to adjust the Ge / Gc by lowering the Ge / Gc by any one or a combination of two or more.

With such a method for producing a silicon single crystal, the distance between the heat shield and the liquid surface of the raw material melt does not become too narrow, so that the heat shield does not prevent the silicon single crystal from being pulled up. Crystals can be produced.

Further, the present invention is an epitaxial silicon wafer having an epitaxial layer on a silicon single crystal substrate in which the entire surface of the crystal is in the N- region, and the silicon single crystal substrate contains 2 × 10 ¹³ atoms / cm ³ or more of nitrogen. It is doped with a nitrogen concentration of 2 × 10 ¹⁴ atoms / cm ³ or less, and the average number of all substrates in a silicon single crystal block having a size of 28 nm or more and a number of defects of 10 cm or more is 2 / sheet or less, at 800 ° C. Provided is an epitaxial silicon wafer characterized in that the BMD having an average size of 45 nm or more detected after heat treatment at 3 hr + 1000 ° C. and 2 hr has ^{a density of 1 × 10 8} / cm ^{3 or more.}

Such an epitaxial silicon wafer does not have BMD density reduction due to the R-OSF region, EP defects, and EP defects due to plate-shaped or rod-shaped COPs when nitrogen-doped at a high concentration. It becomes.

Further, in the present invention, the entire surface of the crystal having a mirror-polished surface is a silicon single crystal substrate in the N- region, and the nitrogen ^{content is 2 × 10 13} atoms / cm ³ or more and 3.2 × 10 ¹⁴ atoms / cm ³ It is doped with the following nitrogen concentration, the non-defective rate of TDDB characteristics is 90% or more, the number of defects of size 45 nm or more is 10 cm or more, and the average number of all substrates in a silicon single crystal block is 2 or less. Provided is a silicon single crystal substrate characterized in that the BMD having an average size of 45 nm or more detected after heat treatment at 800 ° C., 3 hr + 1000 ° C., and 2 hr has ^{a density of 1 × 10 8} / cm ^{3 or more.}

With such a silicon single crystal substrate, the TDDB characteristics are good without a decrease in BMD density due to the R-OSF region.

In the method for producing a silicon single crystal of the present invention, by doping nitrogen at a high concentration, the number of thermally stable large-sized precipitated nuclei is increased, and high BMD is formed even in a low-temperature, short-time device process. Silicon that avoids the R-OSF region even in the wide nitrogen concentration range of the entire crystal length by correcting and adjusting the defect distribution change caused by the high nitrogen concentration due to segregation during crystal growth while achieving the ability (gettering ability). A single crystal can be produced.
Further, the epitaxial silicon wafer of the present invention does not have BMD density decrease due to the R-OSF region, EP defect formation, and EP defect formation due to plate-shaped or rod-shaped COP due to nitrogen doping at a high concentration. It becomes. Further, in the case of the silicon single crystal substrate of the present invention, there is no decrease in BMD density due to the R-OSF region, and the TDDB characteristics are good.

It is a figure which shows an example of the silicon single crystal manufacturing apparatus by the Czochralski method which can be used in this invention. In the defect distribution diagram in the pulling axis direction of the silicon single crystal with the radial position of the silicon single crystal as the horizontal axis when the silicon single crystal is manufactured under the pulling conditions of Comparative Example 1, Comparative Example 2, and Example 1. be. It is a graph which shows the result of the defect evaluation of the epitaxial wafer in the comparative example 3. It is a graph which shows the result of the defect evaluation of the epitaxial wafer in the comparative example 4. It is a graph which shows the result of the defect evaluation of the epitaxial wafer in Example 2. It is a graph which shows the result of the TDDB characteristic evaluation of the silicon single crystal substrate in the comparative example 5. It is a graph which shows the result of the TDDB characteristic evaluation of the silicon single crystal substrate in the comparative example 6. It is a graph which shows the result of the TDDB characteristic evaluation of the silicon single crystal substrate in Example 3.

Hereinafter, the present invention will be described in detail with reference to the drawings as an example of an embodiment, but the present invention is not limited thereto.
The method for producing a silicon single crystal, an epitaxial silicon wafer, and a silicon single crystal substrate of the present invention will be described while also describing the contents of considerations and experiments leading up to the present invention finding the present invention. ..

As described above, in an epitaxial silicon wafer using a nitrogen-doped V-rich crystal as a substrate, when the BMD density is lowered due to the R-OSF region at the outer periphery of the wafer, EP defects are formed, and nitrogen is doped at a high concentration. EP defects due to plate-shaped or rod-shaped COPs may be a problem.

On the other hand, the present inventors have a low / defect-free silicon single crystal substrate manufactured in a nitrogen-doped N (Neutral) region as described in Patent Document 2, or epitaxial silicon using the same as the substrate. For wafers, while solving the problem of BMD density decrease due to the R-OSF region, the increase in thermally stable (large size) precipitated nuclei due to nitrogen doping and the low / defect-free requirement for the wafer surface device operating region. I thought that it was possible to achieve both.

However, based on this idea, while the present inventors are conducting diligent research, when nitrogen doping is performed to produce a low / defect-free crystal in the N- region by the Czochralski method, the total length in the crystal growth axis direction is used. In Japan, it was difficult to avoid the R-OSF region, and the problem was that the yield in a single crystal was extremely low.

Specifically, in the production of low / defect-free crystals in the N-region not doped with nitrogen, a growing method in which the N-region is collected at a high yield over the entire length in the crystal growth axis direction while avoiding the R-OSF region. Even when (Patent Documents 3 to 7) are used, when nitrogen is doped, the low / is low in the N- region in which R-OSF is avoided only in a part of the total length in the crystal growth axis direction where the nitrogen concentration is low. It was not possible to produce defect-free crystals.

Further, as shown in Patent Document 8 for the production of low / no-defect crystal of the nitrogen doped N- region, excellent TDDB characteristic, 3 × 10 ¹³ to be provided a small wafer of BMD density variation Nitrogen concentrations below atoms / cm ³ are not sufficient to increase thermally stable (large size) precipitated nuclei prior to the device process and have high BMD densities (getters) in the tip low temperature, short time device process. It did not meet the requirements for ring ability).

Further, it is described in Patent Document 2 that the nitrogen concentration is set to a high nitrogen concentration ^{of 3 × 10 13} atoms / cm ³ or more, which is sufficient to increase the thermally stable (large size) precipitated nuclei before the device process. As described above, even if the difference between the temperature gradient Gc at the center of the crystal and the temperature gradient Ge at the periphery of the crystal is ΔG = Ge−Gc ≦ 5 ° C./cm, the crystal is being grown as described in Patent Document 9. Even if the pulling rate is adjusted according to the change in nitrogen concentration due to segregation, the R-OSF region is likely to occur at the outer periphery of the wafer, and if the crystal growth rate is reduced to avoid this, the BMD at the center of the wafer There was a problem that the number decreased and the BMD density (gettering ability) in the plane became non-uniform, and in some cases, the I-rich region had dislocation loops and dislocation clusters in the center of the wafer. ..

Faced with these problems, as a result of diligent research by the present inventor, in the production of low / defect-free crystals in the nitrogen-doped N-region, the crystal peripheral portion (crystal outer peripheral portion) is determined according to the nitrogen concentration. ), It was found that the defect region changes.

Next, the change of the defect region in the peripheral portion of the crystal according to the nitrogen concentration will be specifically described.

Changes in the defect distribution due to factors other than the thermal environment of the crystal can be understood as being due to the outward diffusion of point defects, as described in Patent Document 10. In the peripheral portion of the crystal, the influence of the outward diffusion of point defects such as interstitial silicon and vacancies becomes large, and the outward diffusion of the vacancies has the effect of reducing the concentration of residual vacancies in the peripheral portion of the crystal. However, when nitrogen is doped at a high concentration, the outward diffusion of the pores is suppressed by the formation of a pair (NV pair) of the nitrogen and the pores.

Therefore, when nitrogen is doped as compared with the case where nitrogen is not doped, the concentration of residual pores in the peripheral portion of the crystal increases as the concentration of nitrogen increases, and the defect region in the peripheral portion of the crystal is on the R-OSF region side. Will shift to.

The present inventors tend to generate an R-OSF region on the outer peripheral portion of the wafer when a low / defect-free crystal in the N- region is produced by doping with nitrogen, and the crystals are used to avoid the R-OSF region. When the growth rate is lowered, the BMD at the center of the wafer decreases, causing in-plane BMD density (gettering ability) non-uniformity, and in some cases, I- having dislocation loops or dislocation clusters at the center of the wafer. It is the cause of the problem that it has become a rich region, and the effect of suppressing the outward diffusion of pores ^{is generally seen from the nitrogen concentration of 2 × 10 13} atoms / cm ^3, and when it becomes ^{3 × 10 13} atoms / cm ^{3 or more.} It was found that the level seriously affects the crystal yield.

The present invention has been completed by the diligent research of the present inventors in this way, and is a low / defect-free silicon single crystal substrate produced in the N- region of nitrogen doping and an epitaxial using the same as the substrate. In a silicon wafer, a silicon single crystal crystal is grown in consideration of the influence of nitrogen segregation, and the grown silicon single crystal is used to produce a silicon single crystal substrate and an epitaxial silicon wafer using the grown silicon single crystal. The problem caused by the R-OSF region can be completely solved, and it is possible to achieve both the increase of thermally stable (large size) precipitated nuclei due to nitrogen doping and the low / defect-free requirement of the wafer surface device operating region. The heading has reached the present invention.

First, the method for growing a silicon single crystal of the present invention will be described in detail.

The present invention is a method for growing a silicon single crystal by pulling it up under the condition that the entire surface of the crystal is in the N- region by the Czochralski method, and when growing the silicon single crystal, nitrogen is 2 × 10 ¹³ Dope with nitrogen concentration of atoms / cm ³ or more and 3.2 × 10 ¹⁴ atoms / cm ³ or less, and set the ratio of the temperature gradient Gc at the center of the crystal in the pulling axial direction of the silicon single crystal to the temperature gradient Ge at the periphery of the crystal. This is a method for producing a silicon single crystal, characterized in that / Gc> 1 and Ge / Gc is gradually increased in accordance with an increase in nitrogen concentration due to segregation during pulling of the silicon single crystal. Here, the peripheral portion of the crystal is appropriately determined within a region of approximately 1/3 or less of the diameter from the outer peripheral edge of the silicon single crystal.

In such a method for producing a silicon single crystal, by doping nitrogen at a high concentration, the number of thermally stable large-sized precipitated nuclei is increased, and high BMD is formed even in a low-temperature, short-time device process. Silicon that avoids the R-OSF region even in the wide nitrogen concentration range of the entire crystal length by correcting and adjusting the defect distribution change caused by the high nitrogen concentration due to segregation during crystal growth while achieving the ability (gettering ability). A single crystal can be produced.

Further, by using the silicon single crystal produced by the method for producing a silicon single crystal of the present invention, the R-OSF region is caused by doping with a high nitrogen concentration in the silicon single crystal substrate and the epitaxial silicon wafer using the silicon single crystal. It is possible to obtain a wafer having a high BMD forming ability (gettering ability) with a high yield even in a device process at a low temperature and for a short time.

Nitrogen under a condition that the temperature distribution is adjusted during crystal growth so as to obtain the N- region in the crystal length, end the entire surface when not doped, the nitrogen doping ^{amount, 2 × 10 13 atoms / cm} 3 less than the nitrogen concentration and In this case, the effect on the defect distribution is minor, and the TDDB characteristics in the state of using a silicon single crystal substrate and the occurrence of EP defects in an epitaxial silicon wafer using a silicon single crystal substrate are hardly problematic.

However, when ^{the nitrogen concentration is 3 × 10 13} atoms / cm ³ , the defect distribution is affected, the TDDB characteristics deteriorate in the state of using a silicon single crystal substrate, and the epitaxial silicon wafer using a silicon single crystal substrate is used. EP defects occur in. Further, as shown in Patent Document 9, even if the pulling speed is adjusted according to the nitrogen concentration (the pulling speed is adjusted to be slower according to the increase in the nitrogen concentration), this nitrogen concentration is used for the advanced device process. Sufficient BMD density cannot be obtained by low-temperature, short-time heat treatment.

A nitrogen concentration of 3 × 10 ¹³ atoms / cm ³ or more is effective for obtaining a sufficient BMD density by low-temperature, short-time heat treatment as used in advanced device processes, but defect distribution is particularly high in the periphery of the crystal. The change becomes large, and the TDDB characteristics in the state of being a silicon single crystal substrate are further deteriorated, and the occurrence of EP defects in the epitaxial silicon wafer becomes severe. In this nitrogen concentration range, it cannot be sufficiently improved by adjusting the pulling speed to be slower with respect to the increase in the nitrogen concentration of Patent Document 9, and the TDDB characteristics and epitaxials when a silicon single crystal wafer is formed on the outer periphery of the crystal. If the pulling speed is slowed down until the occurrence of EP defects on the silicon wafer can be improved, the BMD at the center of the wafer decreases, causing in-plane BMD density (gettering capacity) non-uniformity, and in some cases, the center of the wafer. In the I-rich region having dislocation loops and dislocation clusters, EP defects occur in the central part.

At a nitrogen concentration of 6 × 10 ¹³ atoms / cm ³ or more, it is more preferable to obtain a sufficient BMD density by low-temperature, short-time heat treatment as used in advanced device processes, but the change in defect distribution is particularly large in the periphery of the crystal. Therefore, the deterioration of the TDDB characteristics in the state of using the silicon single crystal substrate and the occurrence of EP defects in the epitaxial silicon wafer using the silicon single crystal substrate become more severe. In this nitrogen concentration range, it cannot be sufficiently improved by adjusting the pulling rate to be slower with respect to the increase in the nitrogen concentration of Patent Document 9, and the TDDB characteristics in the state of a silicon single crystal substrate in the peripheral portion of the crystal and When the pulling speed is slowed down until the EP defect generation in the epitaxial silicon wafer using the silicon single crystal substrate can be improved, the entire N- region can no longer be retained, and I has dislocation loops and dislocation clusters in the center of the wafer. It becomes a -rich region, and EP defects occur in the central part based on it.

According to the method for producing a silicon single crystal of the present invention, the optimum nitrogen concentration is 3.2 × 10 ¹⁴ atoms / cm ^{3 for obtaining a sufficient BMD density by low-temperature, short-time heat treatment as used in advanced device processes.} To obtain a wafer having good TDDB characteristics when a silicon single crystal substrate is manufactured using the manufactured silicon single crystal, and without EP defects occurring in the state of forming an epitaxial silicon wafer using this silicon single crystal substrate. Can be done.

In the present invention, for example, in the silicon single crystal manufacturing apparatus 14 as shown in FIG. 1, the silicon single crystal can be grown by pulling up the silicon single crystal under the condition that the entire surface of the crystal becomes the N- region by the Czochralski method. Use a possible silicon single crystal manufacturing device. Such a silicon single crystal manufacturing apparatus will be described with reference to FIG. 1, but the single crystal manufacturing apparatus that can be used in the present invention is not limited thereto.

The appearance of the silicon single crystal manufacturing apparatus 14 shown in FIG. 1 is composed of a main chamber 1 and a pulling chamber 2 communicating with the main chamber 1. A graphite crucible 6 and a quartz crucible 5 are installed inside the main chamber 1. A heater 7 is provided so as to surround the graphite crucible 6 and the quartz crucible 5, and the heater 7 melts the raw material silicon polycrystalline contained in the quartz crucible 5 to obtain the raw material melt 4. Further, a heat insulating member 8 is provided to prevent the influence of the radiant heat from the heater 7 on the main chamber 1 and the like.

On the melt surface of the raw material melt 4, heat shields 12 are arranged to face the melt surface at predetermined intervals to block radiant heat from the melt surface of the raw material melt 4. After immersing the seed crystal in this crucible, the rod-shaped single crystal rod 3 is pulled up from the raw material melt 4. The crucible can be raised and lowered in the direction of the crystal growth axis, and the crucible is raised during the growth so as to compensate for the decrease in the liquid level of the raw material melt 4 as the growth of the single crystal progresses, so that the raw material melt 4 The height of the melt surface is kept approximately constant.

Further, an inert gas such as argon gas is introduced as a purge gas during single crystal growth, passes between the single crystal rod 3 being pulled up and the gas rectifying cylinder 11, and then becomes a heat shield 12. It passes between the raw material melt 4 and the melt surface, and is discharged from the gas outlet 9. By controlling the flow rate of the gas to be introduced and the amount of gas discharged by the pump or valve, the pressure in the chamber being pulled up is controlled.

Further, when growing a crystal by the CZ method, a magnetic field may be applied by the magnetic field application device 13.

Here, why is the temperature gradient Gc at the center of the crystal and the temperature gradient Ge at the periphery of the crystal in the pulling axis direction of the silicon single crystal set to Ge / Gc> 1, and Ge / Gc is pulled up by the silicon single crystal. It is logically explained whether it should be gradually increased according to the increase in the nitrogen concentration due to the segregation at the time of.

As the nitrogen concentration increases due to segregation, NV pair formation increases, the outward diffusion of pores (vacancy) on the outer surface of the crystal decreases, and the residual vacuum concentration around the crystal increases, so that the concentration around the crystal increases. Shifts to the defect area where Vacancy predominates.

When the defect region around the crystal is shifted to the vacancy dominant side due to the segregation of nitrogen, the residual vacancy concentration around the crystal is from the crystal center to r / 2 (where r is the radius of the silicon single crystal). Due to the higher value, the BMD distribution becomes non-uniform, and the defect region on the outer peripheral portion shifts from the N- region to the R-OSF region.

In order to avoid this, it is effective to adjust the amount of residual vacancy around the crystal due to the influence of NV pair formation in advance by adjusting the vacancy uptake amount at the solid-liquid interface.

That is, the amount of vacancy taken up at the periphery of the crystal is smaller than the amount of vacancy taken up at the portion other than the periphery of the crystal at the solid-liquid interface.

Boronkov's theory is widely known regarding the incorporation of point defects in silicon single crystal growth, and the point defect concentration depends on the ratio V / G of the growth rate V of the silicon single crystal and the temperature gradient G near the interface. It is determined.

When the V / G is large, the vacancy concentration at the solid-liquid interface increases, and when the V / G is small, the interstitial-Si concentration at the solid-liquid interface increases. To increase.

Therefore, based on Boronkov's theory, the amount of residual vacancy around the crystal due to the influence of NV pair formation is set to be smaller than the central V / Gc in advance. That is,
V / Gc> V / Ge
And.

During steady single crystal growth, the growth rate V on the plane perpendicular to the crystal growth direction is the same from the center of the crystal to the periphery of the crystal, so 1 / Gc> 1 / Ge and Ge / Gc> 1. Is effective, and as the nitrogen concentration increases, the amount of residual vacancy increasing in the peripheral portion of the crystal due to the influence of NV pair formation can be offset by gradually increasing Ge / Gc.

The adjustment of Ge / Gc is to control the distance between the heat shield 12 arranged directly above the raw material melt in the quartz crucible 5 and the liquid level of the raw material melt, and is arranged so as to surround the quartz crucible 5. The position of the heater 7 is lowered with respect to the liquid level of the raw material melt, the magnetic field strength of the magnetic field applying device 13 arranged outside the main chamber 1 of the silicon single crystal manufacturing device is weakened, and , It is preferable to lower the position of the magnetic field applying device 13 by any one or a combination of two or more. With such an adjustment method of Ge / Gc, since the manufacturing apparatus is not significantly changed, it is possible to easily adjust Ge / Gc.

The reason why Ge / Gc is increased by such an adjustment method of Ge / Gc will be described.

There are two methods for increasing Ge / Gc, one is to increase Ge and the other is to decrease Gc.

In order to increase Ge, it is effective to reduce heat radiation (heat supply by radiation) to the crystal side surface portion above the solid-liquid interface. As a specific method thereof, the distance between the heat shield 12 directly above the raw material melt 4 and the liquid level of the raw material melt 4 is narrowed, and the heater 7 for heating the heat source arranged outside the graphite pot 6 is used. There is a method of shielding a part of the heat radiation of the above, and a method of arranging the heater 7 for heating the heat source lower than the liquid level position of the raw material melt 4 to reduce the heat radiation to the upper part of the solid-liquid interface.

Although Ge changes slightly due to heat conduction of gas in the furnace and convection heat transfer due to gas flow, heat radiation occurs in a silicon single crystal manufacturing environment by the CZ method, which is mainly in a high temperature environment with a melting point of 1420 ° C or higher. Control by heat transfer is important because the effect is dominant.

The method of reducing Gc is a method of lowering the height of the solid-liquid interface (melting point isotherm) and relaxing the temperature gradient with the upper part of the solid-liquid interface, weakening the suppression of melt convection at the lower part of the crystal growth interface by the magnetic field. , Makes it easier to remove the latent heat of solidification generated during crystal growth by convection. When the latent heat of solidification is removed by convection, the height of the solid-liquid interface is lowered by the heat balance as compared with the case where it is not. At this time, since the melting point isotherm at the outermost periphery of the crystal is always connected to the surface of the raw material melt 4, Gc is selectively reduced.

As a method of weakening the suppression of melt convection at the lower part of the crystal growth interface by a magnetic field, there is a method of weakening the magnetic field strength when the magnetic field positions are kept the same. Further, when the magnetic field strength is fixed, there is a method of separating the magnetic field position from the surface position of the raw material melt 4. When both the magnetic field position and the magnetic field strength can be changed, a method of weakening the magnetic field strength and a method of changing the magnetic field position may be combined.

As a method of lowering the height of the solid-liquid interface, the solid-liquid interface can also be lowered by weakening the crystal rotation, but since it leads to non-uniformity of the dopant concentration and the oxygen concentration in the plane, the magnetic field at the solid-liquid interface A method of weakening the strength is preferable.

Further, when the Ge / Gc is adjusted by controlling the distance between the heat shield 12 and the liquid level of the raw material melt 4, the heat under the condition that the entire surface of the crystal is in the N- region when nitrogen is not doped. When the distance between the shield 12 and the liquid level of the raw material melt 4 is D, the distance between the heat shield 12 and the liquid level of the raw material melt 4 when nitrogen is doped is set according to the nitrogen concentration. It is preferable to change the D'/ D = 0.94-nitrogen concentration / (2.41 × 10 ¹⁵ ) so as to obtain D'.

With such an adjustment method of Ge / Gc, the adjustment of Ge / Gc can be performed by adjusting the distance between the heat shield 12 and the liquid level of the raw material melt 4 according to the nitrogen concentration. Therefore, Ge / Gc can be adjusted more easily and accurately.

Describe how this relational expression of D'was derived.

First, when the distance D between the heat shield 12 and the melt directly above the raw material melt 4 from which the N- region can be obtained over the entire surface is not doped with nitrogen, nitrogen is 2-2.2 × 10 ¹³ , 3-. ^{3.2 × 10 13, 6-6.2 × 10} 13, 1-1.2 × 10 14, 1.5-1.7 × 10 14, 2.2-2.4 × 10 14, 3-3 defects for each case doped with nitrogen concentration of ^{.2 × 10 14 atoms / cm 3} , conditions other than nitrogen as the same, is gradually decreasing the pulling rate during straight body growth, the silicon single crystal block A sample parallel to the crystal growth axis direction was cut out from the obtained silicon single crystal block so as to include the region V-rich, R-OSF region, Nv region, Ni region, and I-rich region, and 800 ° C. in a wet oxidation atmosphere. Heat treatment was performed at 4 hr + 1000 ° C. for 16 hr, and the change in defect distribution depending on each nitrogen concentration was investigated by the X-ray topograph method (XRT).

Secondly, at each nitrogen concentration, the distance between the heat shield 12 directly above the raw material melt 4 and the liquid level of the raw material melt 4 is changed, and the distribution of the N- region equivalent to that in the case where nitrogen is not doped can be obtained. The distance D'between the heat shield 12 directly above the raw material melt 4 and the liquid level of the raw material melt 4 was determined.

Third, the relational expression of the change in the ratio of the interval D'and the interval D between the heat shield 12 and the liquid level of the raw material melt 4 with respect to the nitrogen concentration was obtained by the least squares method, and D'/ D = 0.94-. Nitrogen concentration / (2.41 × 10 ¹⁵ ) was obtained.

When the obtained D'is larger than 20 mm, Ge / Gc is adjusted by setting the distance between the heat shield 12 and the liquid surface of the raw material melt 4 as the obtained D', and the obtained D'is 20 mm. In the following cases, the distance between the heat shield 12 and the liquid surface of the raw material melt 4 is 20 mm, and the position of the heater 7 arranged so as to surround the quartz rut 5 is set to the liquid of the raw material melt 4. Lowering the surface, weakening the magnetic field strength of the magnetic field applying device 13 arranged outside the main chamber 1 of the silicon single crystal manufacturing device 14, and lowering the position of the magnetic field applying device 13. It is preferable to adjust the Ge / Gc by any one or a combination of two or more of them.

In such a method for producing a silicon single crystal, when the distance between the heat shield 12 and the liquid surface of the raw material melt 4 is as narrow as 20 mm or less, the heat shield 12 comes into contact with the raw material melt 4. It is possible to produce a silicon single crystal without hindering the pulling up of the silicon single crystal due to such factors.

According to the method of the present invention as described above, an epitaxial silicon wafer having an epitaxial layer on a silicon single crystal substrate in which the entire crystal surface is in the N- region, and nitrogen is 2 × 10 ¹³ atoms / cm on the silicon single crystal substrate. ³ or more 3.2 × 10 ¹⁴ atoms / cm Dopeed with ^{a nitrogen concentration of 3} or less, and the number of defects with a size of 28 nm or more is 2 or less on average for all substrates in a silicon single crystal block of 10 cm or more. , 800 ° C., 3 hr + 1000 ° C., 2 hr, an epitaxial silicon wafer characterized in that the BMD having an average size of 45 nm or more detected after the heat treatment has ^{a density of 1 × 10 8} / cm ^{3 or more.}

With such an epitaxial silicon wafer, there is no decrease in BMD density due to the R-OSF region, EP defect formation, and EP defect formation due to plate-shaped or rod-shaped COP due to nitrogen doping at a high concentration. .. Further, a sufficient BMD density is formed by heat treatment at 800 ° C., 3 hr + 1000 ° C., and 2 hr, and an epitaxial silicon wafer having uniform in-plane BMD quality is obtained.

Further, according to the method of the present invention, the entire surface of the crystal having a mirror-polished surface is a silicon single crystal substrate in the N- region, and the nitrogen ^{content is 2 × 10 13} atoms / cm ³ or more and 3.2 × 10 ¹⁴ atoms /. It is doped with a nitrogen concentration of cm ³ or less, the non-defective rate of TDDB characteristics is 90% or more, and the number of defects with a size of 45 nm or more is 10 cm or more. Provided is a silicon single crystal substrate characterized in that the BMD having an average size of 45 nm or more detected after heat treatment at 800 ° C., 3 hr + 1000 ° C., and 2 hr has ^{a density of 1 × 10 8} / cm ^{3 or more.} can do.

With such a silicon single crystal substrate, there is no decrease in BMD density due to the R-OSF region, and the TDDB characteristics are good. Further, a sufficient BMD density is formed by heat treatment at 800 ° C., 3 hr + 1000 ° C., and 2 hr, and a silicon single crystal substrate having uniform in-plane BMD quality is obtained.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

(Comparative Example 1)
A crystal having a diameter of 300 mm was produced by melting 410 kg of a raw material in a 32-inch (812.8 mm) crucible without doping with nitrogen and applying a magnetic field of 4000 G. At this time, the distance (50 mm) between the heat shield directly above the raw material melt and the raw material melt, the heater position, and the position of the magnetic field applying device are adjusted in advance to obtain an N (Neutral) region over the entire crystal length. The temperature distribution during crystal growth was adjusted as described above. Under this condition, the pulling speed is gradually reduced during straight body growth, and the defect region V-rich, R-OSF region, Nv region, Ni region, and I-rich region (from V-rich) are contained in the silicon single crystal block. A sample parallel to the crystal growth axis direction was cut out from the obtained silicon single crystal block so as to include each region of I-rich, and heat-treated at 800 ° C. 4 hr + 1000 ° C. 16 hr in a wet oxidation atmosphere, and XRT (X-ray topograph) was applied. The defect distribution was evaluated by the method).

(Comparative Example 2)
Nitrogen is doped in the distance (50 mm) between the heat shield directly above the raw material melt and the raw material melt, the heater position, the magnetic field position, and the magnetic field strength similar to those in Comparative Example 1, and the pulling speed is gradually increased during the straight body growth. A silicon single crystal block for evaluating defect distribution containing each region from V-rich to I-rich was produced in the silicon single crystal block. Nitrogen concentration is 2 × 10 ¹³ atoms / cm ³ levels (nitrogen concentration in silicon single crystal block 2 × 10 ¹³ -2.2 × 10 ¹³ atoms / cm ³ ), 3 × 10 ¹³ atoms / cm ³ levels (single silicon silicon). crystal block nitrogen concentration ^{3 × 10 13 -3.2 × 10 13} atoms / cm 3), 6 × 10 13 atoms / cm 3 levels (silicon single crystal block nitrogen concentration 6 × ^{10 13} -6.2 × ¹⁰ 13 atoms / ^cm 3), 3 × as ¹⁰ 14 atoms / cm ³ levels (nitrogen concentration in the silicon single crystal block ^{3 × 10 14 -3.2 × 10 14} atoms / cm 3), to produce respective silicon single crystal block , The defect distribution at each nitrogen concentration was evaluated in the same manner as in Comparative Example 1.

(Example 1)
Comparative Example 2 except that the distance between the heat shield directly above the raw material melt and the liquid level of the raw material melt was set to D' ^{obtained from D'/ D = 0.94-nitrogen concentration / 2.41 × 10 15.} It was carried out in the same manner as. By changing the distance between the heat shield directly above the raw material melt and the liquid level of the raw material melt in this way, the temperature gradient Gc at the center of the crystal and the temperature gradient Ge at the periphery of the crystal in the pulling axis direction of the silicon single crystal. Was set to Ge / Gc> 1, and Ge / Gc was gradually increased in accordance with the increase in nitrogen concentration due to segregation during pulling of the silicon single crystal. Here, D is 50 mm. The distance between the heat shield directly above the raw material melt and the liquid level of the raw material melt is 2 × 10 ¹³ atoms / cm at ³ levels (nitrogen concentration in the silicon single crystal block 2-2.2 × 10 ¹³ atoms / cm ³ ). D'= 46.6 mm (D'/ D = 0.932), 3 × 10 ¹³ atoms / cm ³ levels (nitrogen concentration in silicon single crystal block 3-3.2 × 10 ¹³ atoms / cm ³ ) = 46.3 mm (D'/ D = 0.926), 6 × 10 ¹³ atoms / cm ³ levels (nitrogen concentration in silicon single crystal block 6-6.2 × 10 ¹³ atoms / cm ³ ) D'= 45 At 0.8 mm (D'/ D = 0.916), 3 × 10 ¹⁴ atoms / cm ³ levels (nitrogen concentration in silicon single crystal block 3-3.2 × 10 ¹⁴ atoms / cm ³ ), D'= 40.8 mm A silicon single crystal block was produced as (D'/ D = 0.816), and the defect distribution when the distance between the heat shield directly above the raw material melt and the liquid level of the raw material melt was adjusted at each nitrogen concentration was evaluated. bottom. The distance between the heat shield directly above the raw material melt and the liquid level of the raw material melt was changed by changing the height position of the crucible.

FIG. 2 shows the pulling axis direction of the silicon single crystal with the radial position of the silicon single crystal as the horizontal axis when the silicon single crystal is manufactured under the pulling conditions of Comparative Example 1, Comparative Example 2, and Example 1. The defect distribution map is shown.

Compared to Comparative Example 1, the defect distribution of Comparative Example 2 doped with nitrogen was as follows: Nitrogen-doped amount 2 × 10 ¹³ atoms / cm ³ levels, 3 × 10 ¹³ atoms / cm ³ levels, 6 × 10 ¹³ atoms / cm ³ level 3 in the × ¹⁰ 14 atoms / cm ³ levels, respectively, since the out-diffusion of nitrogen and vacancy pairs (NV pair) vacancies during crystal growth by the formation (vacancy) decreases with the nitrogen concentration is increased, The defect region on the outer peripheral side of the crystal is shifted to the Vacancy dominant side (high V / G side), and the R-OSF region is changed to a sagging distribution on the outer peripheral portion.

In such a defect distribution, when a wafer is manufactured, defect regions having significantly different residual vacancy concentrations are mixed in the plane (R-OSF region in the outer peripheral portion + R / 2-Nv region in the central portion, Nv region in the outer peripheral portion). + R / 2-Ni region in the center, R-OSF region in the outer circumference + Nv region in the R / 2 + Ni region in the center) The number of vacancy will increase. Therefore, the in-plane BMD (Bulk Micro Defect) density after the heat treatment at 800 ° C., 3 hr + 1000 ° C., and 2 hr is significantly different, and the device yield due to insufficient gettering ability in the low BMD region in the wafer plane. It becomes a factor such as a decrease.

On the other hand, in Example 1 of the present invention, the defect distribution changes with the increase in nitrogen concentration (the defect region on the outer peripheral side of the crystal shifts to the Vacancy dominant side, and the R-OSF region changes to a sagging distribution on the outer peripheral portion). Since the entire surface of the wafer surface can be made into a uniform defect region when the wafer is manufactured, the BMD density in the wafer surface after heat treatment at a low temperature for a short time, for example, 800 ° C., 3 hr + 1000 ° C., and 2 hr. Can be controlled uniformly. In addition, device yield and wafers can be suppressed in that TDDB characteristics deteriorate in the state of a silicon single crystal substrate due to the mixture of R-OSF regions and EP defects can be suppressed when the manufactured silicon single crystal substrate is used as a substrate for an epitaxial silicon wafer. The yield is good.

In addition, nitrogen gradually increases in concentration as the crystal growth progresses due to the segregation phenomenon during crystal growth (equilibrium segregation coefficient 7 × 10 ^-4). The invention is very effective.

[Change in non-defective rate of epitaxial silicon wafer (quality transition in one silicon single crystal)]
Next, the effect obtained when the present invention is applied to actual product manufacturing will be described in detail by taking the non-defective rate of the epitaxial wafer as an example.

(Comparative Example 3)
410 kg of the raw material was melted in a 32 inch (812.8 mm) crucible, and a crystal having a diameter of 300 mm was produced under the application of a magnetic field of 4000 G. The distance between the heat shield directly above the raw material melt and the liquid level of the raw material melt is 50 mm, and the heater position and magnetic field are applied during crystal growth so that the N- region can be obtained over the entire length of the crystal when nitrogen is not doped. in the position adjusted condition of the apparatus, the straight body product collection unit, nitrogen doped (Comparative example 3-1), the nitrogen concentration of ^{2 × 10 13 -6 × 10 13} atoms / cm 3 ( Comparative example 3-2), 1 × ¹⁰ 14 -3.2 × ¹⁰ 14 and so as to three nitrogen concentration of atoms / cm ³ (Comparative example 3-3) performs a crystal production, to produce a silicon single crystal substrate from the obtained crystals, An epitaxial silicon wafer was manufactured by using it as a substrate for an epitaxial silicon wafer. In order to evaluate the defects of the epitaxial silicon wafer, SP3 manufactured by KLA Tencor was used to evaluate the defects detected at 28 nm or more in the Oblique mode. Further, the produced epitaxial wafer was heat-treated at 800 ° C., 3 hr + 1000 ° C., and 2 hr, and then the BMD density of 30 nm or more was measured by an infrared scattering method.

(Comparative Example 4)
While the distance between the heat shield directly above the raw material melt and the liquid level of the raw material melt remains 50 mm, the pulling speed is adjusted according to the nitrogen concentration as shown in Patent Document 9 (pulling with respect to the increase in nitrogen concentration). Except that the speed was adjusted to be slower), it was the same as Comparative Example 3-2 (Comparative Example 4-1) and the same as Comparative Example 3-3 (Comparative Example 4-2). Was manufactured and defect evaluation was performed. Further, the produced epitaxial wafer was heat-treated at 800 ° C., 3 hr + 1000 ° C., and 2 hr, and then the BMD density of 30 nm or more was measured by an infrared scattering method.

(Example 2)
The distance D'between the heat shield directly above the raw material melt and the liquid surface of the raw material melt was defined as D'obtained from ^{D'/ D = 0.94-nitrogen concentration / (2.41 × 10 15).} Examples 2-1, 2 × with nitrogen concentration of ^{10 13 -6 × 10 13 atoms /} cm 3, nitrogen segregation from the crystal cone side to offset the effects of nitrogen segregation during the growth of crystal with nitrogen at Tail side The same as in Comparative Example 4-1 except that the distance between the heat shield directly above the raw material melt and the liquid level of the raw material melt was adjusted from D'= 46.6 mm to 45.8 mm according to the change in concentration. 2-2, 1 × ¹⁰ 14 nitrogen concentration of ^{-3.2 × 10 14 atoms / cm 3} , D '= thermal shield and liquid material melt just above the raw material melt to 40.3mm from 44.9mm The same as in Comparative Example 4-2 except that the distance from the surface was adjusted, an epitaxial wafer was manufactured and defect evaluation was performed in the same manner as in Comparative Example 3. Further, the produced epitaxial wafer was heat-treated at 800 ° C., 3 hr + 1000 ° C., and 2 hr, and then the BMD density of 30 nm or more was measured by an infrared scattering method. By changing the distance between the heat shield directly above the raw material melt and the liquid level of the raw material melt in this way, the temperature gradient Gc at the center of the crystal and the temperature gradient Ge at the periphery of the crystal in the pulling axis direction of the silicon single crystal. Was set to Ge / Gc> 1, and Ge / Gc was gradually increased in accordance with the increase in nitrogen concentration due to segregation during pulling of the silicon single crystal.

FIGS. 3, 4, and 5 are graphs showing the results of defect evaluation of epitaxial wafers in Comparative Example 3, Comparative Example 4, and Example 2, respectively. In advanced devices with high process cost, even if there are only a few defects per wafer, the defective chips caused by them become a big problem.

In Comparative Example 3, ^{EP defects were hardly a problem up to a nitrogen concentration of 2 × 10 13} atoms / cm ³ , but the nitrogen concentration was high enough to increase the thermally stable (large size) precipitated nuclei. It becomes 3 × ¹⁰ 13 becomes nitrogen concentration of atoms / cm ³ when EP defects have come to be seen. Further, when the nitrogen concentration is 3 × 10 ¹³ atoms / cm ³ or more, EP defects increase as the nitrogen concentration increases, and the level is unbearable for use in advanced devices with high process cost. The BMD densities of the epitaxial silicon wafers after heat treatment at 800 ° C., 3 hr + 1000 ° C., and 2 hr in Comparative Examples 3-1, 3-2, and 3-3 were 1-3 × 10 ⁷ , 1-2 × 10, respectively. ^{It was 8} and 2.5-15 × 10 ⁸ / cm ³ . The average size 45nm or more BMD density appears to have a sufficient gettering capability tip device with nitrogen concentration 2 × ¹⁰ 13 atoms / cm ³ or more was possible to 1 × 10 ⁸ or more.

In Comparative Example 4, an improvement effect can be seen by lowering the pulling rate with respect to the increase in nitrogen concentration, but it is more preferable to obtain a sufficient BMD density by low-temperature, short-time heat treatment as used in the advanced device process6. EP defects began to increase from nitrogen concentrations of × 10 ¹³ atoms / cm ^{3 and above, and nitrogen 1 × 10 14} atoms / cm ^{3 and} above were not at levels suitable for use in advanced devices. Further, when the pulling speed is further lowered, the BMD at the center of the wafer decreases when the heat treatment is performed at 800 ° C., 3 hr + 1000 ° C., and 2 hr, resulting in non-uniformity of the in-plane BMD density (gettering ability). In some cases, the I-rich region has dislocation loops and dislocation clusters in the center of the wafer, causing EP defects in the center. Therefore, adjusting the pulling speed with respect to the nitrogen concentration is sufficient for EP defects. It was impossible to suppress. In Comparative Example 4-1, and, in 4-2, 800 ℃, 3hr + 1000 ℃, respectively BMD density of the epitaxial silicon wafer after the heat treatment of 2 hr 1-2 × 10 ^8, and, 2.5-15 × 10 It was ⁸ / cm ^3. The average size 45nm or more BMD density appears to have a sufficient gettering capability tip device with nitrogen concentration 2 × ¹⁰ 13 atoms / cm ³ or more was possible to 1 × 10 ⁸ or more.

In contrast, in Example 2, EP defect until the nitrogen concentration of 3.2 × ¹⁰ 14 atoms / cm ³ is able to be suppressed to a good level. As a result, the defects at 28 nm or more are extremely good defect levels of 2 or less on average for all the substrates in the silicon single crystal block of 10 cm or more, and the epitaxial silicon wafer has fewer defects than Comparative Examples 3 and 4. I was able to get. The BMD density of the epitaxial silicon wafer after heat treatment at 800 ° C., 3 hr + 1000 ° C., and 2 hr was 1-2 × 10 ⁸ / cm ³ in Example 2-1 and 2.5-5 × 10 ^{8 in Example 2-2.} The density of BMD with an average size of 45 nm or more, which is / cm ³ and is considered to have sufficient gettering ability in advanced devices at a nitrogen concentration of 2 × 10 ¹³ atoms / cm ^{3 or more, shall be 1 × 10 8} / cm ³ or more. I was able to. Since EP defects caused by precipitates may occur at a nitrogen concentration of 3.5 × 10 ¹⁴ atoms / cm ³ , it is desirable that ^{the nitrogen concentration be 3.2 × 10 14} atoms / cm ^{3 or less.}

As described above, according to the present invention, an epitaxial silicon wafer having a good EP defect level can be obtained in a very high crystal length even under high nitrogen concentration conditions where high gettering ability can be expected in a low-temperature, short-time device process at the tip. It becomes possible to manufacture by yield.

[Change in non-defective rate of silicon single crystal substrate (quality transition in one silicon single crystal)]
Next, the effects obtained when the present invention is applied to actual product manufacturing will be described in detail using the non-defective rate of the silicon single crystal substrate as an example.

(Comparative Example 5)
410 kg of the raw material was melted in a 32 inch (812.8 mm) crucible, and a crystal having a diameter of 300 mm was produced under the application of a magnetic field of 4000 G. The position of the heater during crystal growth so that the N (Neutral) region can be obtained over the entire length of the crystal when the distance between the heat shield directly above the raw material melt and the liquid level of the raw material melt is 50 mm and nitrogen is not doped. in the position adjusted condition of the magnetic field applying device, in straight body product collection unit, nitrogen doped (Comparative example ^{5-1), 2 × 10 13 -6} × 10 13 atoms / nitrogen concentration of cm ³ (Comparative example 5-2 ), 1 × ¹⁰ 14 -3.2 × such that the nitrogen concentration of ¹⁰ 14 atoms / cm ³ (Comparative example 5-3) performs three crystal production, producing a silicon single crystal substrate from the obtained crystals Then, the TDDB characteristics were evaluated. Further, in order to evaluate the defects of the silicon single crystal substrate, SP3 manufactured by KLA Tencor was used to evaluate the defects detected at 45 nm or more in the Oblique mode. Further, the prepared silicon single crystal substrate was heat-treated at 800 ° C., 3 hr + 1000 ° C., and 2 hr, and then the BMD density of 30 nm or more was measured by an infrared scattering method.

(Comparative Example 6)
While keeping the distance between the heat shield directly above the raw material melt and the liquid level of the raw material melt at 50 mm, the pulling speed is adjusted according to the nitrogen concentration as shown in Patent Document 9 (pulling with respect to the increase in nitrogen concentration). A single silicon produced in the same manner as in Comparative Example 5 as the same as Comparative Example 5-2 (Comparative Example 6-1) and the same as Comparative Example 5-3 (Comparative Example 6-2) except that the speed was adjusted to be slower). The TDDB characteristics and defects of the crystal substrate were evaluated. Further, the prepared silicon single crystal substrate was heat-treated at 800 ° C., 3 hr + 1000 ° C., and 2 hr, and then the BMD density of 30 nm or more was measured by an infrared scattering method.

(Example 3)
The distance between the heat shield directly above the raw material melt and the liquid level of the raw material melt was defined as D'obtained from ^{D'/ D = 0.94-nitrogen concentration / (2.41 × 10 15).} Examples 3-1, 2 × with nitrogen concentration of ^{10 13 -6 × 10 13 atoms /} cm 3, nitrogen segregation from the crystal cone side to offset the effects of nitrogen segregation during the growth of crystal with nitrogen at Tail side The same as in Comparative Example 6-1 except that the distance between the heat shield directly above the raw material melt and the liquid level of the raw material melt was adjusted from D'= 46.6 mm to 45.8 mm according to the change in concentration. 3-2, 1 × ¹⁰ 14 nitrogen concentration of ^{-3.2 × 10 14 atoms / cm 3} , D '= thermal shield and liquid material melt just above the raw material melt to 40.3mm from 44.9mm As in Comparative Example 6-2, a silicon single crystal substrate was produced and the TDDB characteristics and defects were evaluated in the same manner as in Comparative Example 5 except that the distance from the surface was adjusted. Further, the prepared silicon single crystal substrate was heat-treated at 800 ° C., 3 hr + 1000 ° C., and 2 hr, and then the BMD density of 30 nm or more was measured by an infrared scattering method. By changing the distance between the heat shield directly above the raw material melt and the liquid level of the raw material melt in this way, the temperature gradient Gc at the center of the crystal and the temperature gradient Ge at the periphery of the crystal in the pulling axis direction of the silicon single crystal. Was set to Ge / Gc> 1, and Ge / Gc was gradually increased in accordance with the increase in nitrogen concentration due to segregation during pulling of the silicon single crystal.

FIGS. 6, 7, and 8 are graphs showing the results of TDDB characteristic evaluation of the silicon single crystal substrate in Comparative Example 5, Comparative Example 6, and Example 3, respectively.

In FIGS. 6, 7, and 8, gray cells are TDDB defective parts. The TDDB defective defect and the EP defect source are related, and the results are the same as the evaluation of the EP defect in Comparative Example 3, Comparative Example 4, and Example 2 (FIGS. 3, 4, and 5). In Comparative Example 5, at ^{a nitrogen concentration of 3 × 10 13} atoms / cm ³ or more, TDDB defects gradually increased as the nitrogen concentration increased. The non-defective rate of TDDB characteristics in Comparative Example 5 was 99.7-99.3, 99.3-69.2, and 50 in Comparative Example 5-1 and Comparative Example 5-2 and 5-3, respectively. It was .7-14.7%. Further, in Comparative Examples 5-1, 5-2, and 5-3, the defects at 45 nm or more were 1-2, 1.8-158, and the average of all the substrates in the silicon single crystal block of 10 cm or more. , 73-1250 pieces / sheet. The BMD densities of the silicon single crystal substrates after heat treatment at 800 ° C., 3 hr + 1000 ° C., and 2 hr in Comparative Examples 5-1, 5-2, and 5-3 were 1-3 × 10 ⁷ , 1-2 ×, respectively. It was 10 ⁸ and 2.5-15 × 10 ⁸ / cm ³ . The average size 45nm or more BMD density appears to have a sufficient gettering capability tip device with nitrogen concentration 2 × ¹⁰ 13 atoms / cm ³ or more was possible to 1 × 10 ⁸ or more.

Similar to the tendency of EP defects, Comparative Example 6 also showed an improvement effect on Comparative Example 5, but could not be completely improved, and TDDB defects were observed from a nitrogen concentration of ^{6 × 10 13} atoms / cm ^{3 or more.} It will increase and worsen. The non-defective rate of TDDB characteristics in Comparative Example 6 was 99.7-87.3 and 69.9-51.7%, respectively, in Comparative Example 6-1 and Comparative Example 6-2. Further, the defects at 45 nm or more in Comparative Example 6-1 and Comparative Example 6-2 were 1-57 / sheet and 160-364 / sheet on average of all the substrates in the silicon single crystal block of 10 cm or more. there were. In Comparative Example 6-1, and, in 6-2, 800 ℃, 3hr + 1000 ℃, respectively BMD density of the silicon single crystal substrate after the heat treatment of 2 hr 1-2 × 10 ^8, and, 2.5-15 × It was 10 ⁸ / cm ³ . The average size 45nm or more BMD density appears to have a sufficient gettering capability tip device with nitrogen concentration 2 × ¹⁰ 13 atoms / cm ³ or more was possible to 1 × 10 ⁸ or more.

In contrast, in Example 3, and it is possible to suppress the TDDB failure until the nitrogen concentration of ^{3.2 × 10 14 atoms / cm 3} . The non-defective rate of TDDB characteristics in Example 3 was 99.7-99.3 in the range of ^{nitrogen concentration 2-3.2 × 10 14} atoms / cm ^{3 in Examples 3-1 and 3-2, respectively.} %Met. In addition, the defects at 45 nm or more in Examples 3-1 and 3-2 were 1-1.9 on average and 1.2-2 pieces / sheet on the average of all the substrates in the silicon single crystal block of 10 cm or more. Met. In Examples 3-1 and in Example 3-2, 800 ℃, 3hr + 1000 ℃, respectively BMD density of the silicon single crystal substrate after the heat treatment of 2 hr 1-2 × 10 ^8, and, 2.5-15 × It was 10 ⁸ / cm ³ . The average size 45nm or more BMD density appears to have a sufficient gettering capability tip device with nitrogen concentration 2 × ¹⁰ 13 atoms / cm ³ or more was possible to 1 × 10 ⁸ or more.

As described above, according to the present invention, there is no increase in TDDB defects even under high nitrogen concentration conditions where high gettering ability can be expected in the advanced low temperature and short time device process, and the silicon single crystal substrate has a good defect level. Can be produced with a very high yield in the entire crystal length.

^{As described above, according to the present invention, the optimum nitrogen concentration 3 × 10 13} atoms / cm ³ to 3.2 × for obtaining a sufficient BMD density by low-temperature, short-time heat treatment as used in advanced device processes. Up to 10 ¹⁴ atoms / cm ³ , it is possible to obtain a wafer having good TDDB characteristics in a silicon single crystal substrate and without EP defects occurring in an epitaxial silicon wafer.

The present invention is not limited to the above embodiment. The above embodiment is an example, and any one having substantially the same configuration as the technical idea described in the claims of the present invention and exhibiting the same effect and effect is the present invention. It is included in the technical scope of the invention.

1 ... Main chamber, 2 ... Pull-up chamber, 3 ... Single crystal rod,
4 ... Raw material melt, 5 ... Quartz crucible, 6 ... Graphite crucible, 7 ... Heater,
8 ... Insulation member, 9 ... Gas outlet, 10 ... Gas inlet, 11 ... Gas rectifier tube,
12 ... Heat shield, 13 ... Magnetic field application device, 14 ... Silicon single crystal manufacturing device.

Claims (4)

It is a method of growing a silicon single crystal by pulling it up under the condition that the entire surface of the crystal becomes a Neutral region by the Czochralski method.
When growing the silicon single crystal, nitrogen was doped at a nitrogen concentration of ^{2 × 10 13} atoms / cm ³ or more and 3.2 × 10 ¹⁴ atoms / cm ^{3 or less.}
The ratio of the temperature gradient Gc at the center of the crystal in the pull-up axis direction of the silicon single crystal to the temperature gradient Ge at the periphery of the crystal is set to Ge / Gc> 1.
A method for producing a silicon single crystal, which comprises gradually increasing the Ge / Gc in accordance with an increase in nitrogen concentration due to segregation during pulling of the silicon single crystal. The Ge / Gc is adjusted by controlling the distance between the heat shield arranged directly above the raw material melt in the quartz crucible and the liquid level of the raw material melt, and the heater arranged so as to surround the quartz crucible. The position of the raw material melt is lowered with respect to the liquid level of the raw material melt, the magnetic field strength of the magnetic field applying device arranged outside the main chamber of the silicon single crystal manufacturing device is weakened, and the magnetic field applying device is used. The method for producing a silicon single crystal according to claim 1, wherein the position of the silicon single crystal is lowered, which is performed by any one or a combination of two or more. When the Ge / Gc adjustment is performed by controlling the distance between the heat shield and the liquid level of the raw material melt, the heat shield under the condition that the entire surface of the crystal becomes a Neutral region when nitrogen is not doped. When the distance between the body and the liquid level of the raw material melt is D, the distance between the heat shield and the liquid level of the raw material melt when nitrogen is doped is set to D'depending on the nitrogen concentration. The method for producing a silicon single crystal according to claim 2, wherein the amount is changed so as to be D'obtained from / D = 0.94-nitrogen concentration / (2.41 × 10 ^15). When the determined D'is larger than 20 mm, the Ge / Gc is adjusted by setting the distance between the heat shield and the liquid surface of the raw material melt to the determined D', and the determination is made. When D'is 20 mm or less, the distance between the heat shield and the liquid level of the raw material melt is set to 20 mm, and the position of the heater arranged so as to surround the quartz ruts is set to the raw material melt. To lower the liquid level of the silicon single crystal, to weaken the magnetic field strength of the magnetic field applying device arranged outside the main chamber of the silicon single crystal manufacturing device, and to lower the position of the magnetic field applying device. The method for producing a silicon single crystal according to claim 3, wherein the Ge / Gc is adjusted by any one or a combination of two or more of them.

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