KR20190135913A - Method for manufacturing silicon single crystal, epitaxial silicon wafer and silicon single crystal substrate - Google Patents

Abstract

The present invention relates to a low/defect-free crystalline silicon single crystal substrate which is promoted to be extracted by nitrogen doping, an epitaxial silicon wafer, and a method for manufacturing a silicon signal crystal, which can form sufficient BMD in a high-technology device process at low temperature and short time, and can manufacture a wafer having high gettering capability at high yield. The method for manufacturing a silicon signal crystal is a method for growing a silicon single crystal by raising a condition to have the entire crystal surface to be an N-region, by a czochralski technique, nitrogen is doped with a concentration of 2 × 10^13 to 3.2 × 10^14 atoms/cm^3, a ratio of a temperature gradient Gc of a crystal central part of the silicon single crystal in a rising axial direction to a temperature gradient Ge of a crystal peripheral part satisfies Ge / Gc > 1, and Ge / Gc is gradually increased as the concentration of nitrogen is increased by segregation during rising of the silicon single crystal.

Description

METHOD FOR MANUFACTURING SILICON SINGLE CRYSTAL, EPITAXIAL SILICON WAFER AND SILICON SINGLE CRYSTAL SUBSTRATE}

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

Recently, there are two major problems in semiconductor devices (Logic, NAND, DRAM, etc.) in which miniaturization proceeds.

One is that even a very small defect near the wafer surface can be a cause of device defects. Therefore, a high quality wafer with few or no defects must be manufactured in the vicinity of the surface serving as the device operating area.

In addition, due to the low temperature and short time process, the BMD (Bulk Micro Defect), which becomes a gettering site of impurity metal, which has been sufficiently formed in the device process in the past, is difficult to be formed, and the yield of the device is lowered. It is a factor.

In order to satisfy the requirement for defects near the wafer surface of the former, V-rich region having COP (Crystal Originated Particle) originating from the public, or R-OSF region in which oxidative organic layer defects occur in a ring phase during thermal oxidation, A low / defect-free silicon single crystal substrate fabricated in the N (Neutral) region which does not include any of the dislocation loops or dislocation cutters due to inter-grating silicon, or an epitaxial silicon wafer which forms a defect free layer on the substrate, There is an anneal wafer.

Among these, in the annealing wafer, there is a problem that the post-treatment time required for forming the defect-free layer is long, which is unsuitable for mass supply and likely to be expensive.

Epitaxial silicon wafers can form a defect free layer with a relatively short post-process, but at an additional cost compared to silicon single crystal substrates of low / defective crystals.

In addition, in epitaxial silicon wafers, it is common to use high-productivity V-rich crystals grown by crystal growth at a higher speed than low / defective crystals in order to offset the additional cost of post-processing.

It is known that nitrogen dope is effective to increase the BMD that becomes the gettering site of the impurity metal. However, in the nitrogen-doped V-rich crystals, the BMD density reduction due to the R-OSF region, the EP defects, and the EP defects due to the plate- or rod-like COP when doped with a high nitrogen atom concentration are observed at the outer peripheral portion of the wafer. This may be a problem.

In order to avoid this, there is a method in which the crystal is grown thicker than the product diameter and the portion corresponding to the R-OSF is removed by cylindrical grinding, but it takes grinding loss, the cost of grinding, and time. As another method, there is a method of using an N-region crystal containing no R-OSF, but it is difficult to obtain a crystal containing no R-OSF by doping nitrogen.

Next, the influence of the low temperature and short time process accompanying refinement | miniaturization of the latter is demonstrated.

For the operation (source / drain current) of the MOSFET, a required amount of capacitance of the gate insulating film (= dielectric film dielectric constant x gate area / insulation film thickness) must be ensured. As a result of the miniaturization of the semiconductor device, the gate length is shortened and the gate area is reduced to compensate for the thinning of the gate insulating film.

For this reason, 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 becomes an important factor for the reliability of device operation. As a result, the various heat treatments in the device process are reduced in temperature and time, thereby achieving uniform film thickness and film quality of the gate insulating film.

However, as a disadvantage of low temperature and short time of the device process, conventionally, BMD, which is a gettering site of impurity metal, is sufficiently formed in the substrate in the device process, whereas in the low temperature and short time device process, BMD There is little formation, the gettering ability with respect to an impurity metal is reduced, and it may become a deterioration factor of a device yield.

In view of such a problem, there is a need for a wafer capable of forming a BMD more easily than in the prior art in a low-temperature and short-time device process and obtaining a high gettering capability even in a low-temperature and short-term device process.

In order to form a sufficient BMD in the low-temperature and short-term device process, as shown in Patent Literature 1, the coagulation is suppressed by nitrogen dope, and thermally before the device process by promoting the formation of precipitation nuclei by the remaining excess pores. It is known that a method of increasing stable (large size) precipitation nuclei is effective.

However, in the epitaxial silicon wafer using the nitrogen-doped V-rich crystal described above for the substrate, the plate shape when the nitrogen-doped BMD density decrease due to the R-OSF region, the EP defect, and the high concentration of the nitrogen-doped V-rich crystal were used. EP defects due to the COP of the rods may be a problem.

Japanese Patent Application Laid-Open No. 2001-139396 Japanese Patent Laid-Open No. 2000-53497 Japanese Patent Laid-Open No. H11-79889 Japanese Patent Application Laid-Open No. 2000-178099 WO2002 / 000969 Japanese Patent Laid-Open No. 2000-16897 Japanese Patent Application Laid-Open No. 2000-159595 Japanese Patent Publication No. 2008-66357 Japanese Patent Publication No. 2007-70132 Japanese Patent Application Laid-Open No. 2016-13957

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is an advanced low-temperature / short-time device in a low / defective crystalline silicon single crystal substrate in which precipitation (BMD formation) is promoted by nitrogen doping and an epitaxial silicon wafer using the same for a substrate. It is an object of the present invention to provide a method for producing a silicon single crystal that enables sufficient BMD formation even in a process and enables the production of a wafer having high gettering capability in a high yield.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, this invention raises | generates a silicon single crystal by pulling up on the conditions that the whole crystal surface becomes an N-region by Czochralski method. × 10 ¹³ atoms / cm ³ at least 3.2 × 10 ¹⁴ atoms / cm ³ is doped in a concentration of up to the ratio of the temperature gradient Ge of the temperature gradient Gc and crystal periphery (crystal outer peripheral portion) of the central decision of the pulling axis direction of the silicon single crystal Is Ge / Gc> 1, and the Ge / Gc is gradually increased with increasing nitrogen concentration due to segregation during pulling up of the silicon single crystal, thereby providing a method for producing a silicon single crystal.

In the silicon single crystal manufacturing method, by dope nitrogen at a high concentration, the precipitate nuclei of a large size which are thermally stable are increased, and crystal growth is achieved while achieving a high BMD formation ability (gettering ability) even in a low temperature and short time device process. By modifying and adjusting the defect distribution change caused by the high concentration of nitrogen due to heavy segregation, it is possible to produce a silicon single crystal that avoids the R-OSF region even in a nitrogen concentration range having a large crystal total length.

At this time, the Ge / Gc is adjusted to control the gap between the heat shield and the liquid level of the raw material melt disposed directly on the raw material melt in the quartz crucible, and the position of the heater arranged to surround the quartz crucible is used to determine the location of the raw material melt. Any one or two of lowering the liquid level, lowering the magnetic field strength of the magnetic field application device disposed outside the main chamber of the silicon single crystal production device, and lowering the position of the magnetic field application device. It is preferable to perform by the above combination.

According to the Ge / Gc adjustment method, since the manufacturing apparatus is not greatly changed, Ge / Gc can be easily adjusted.

At this time, when the Ge / Gc is adjusted by controlling the gap between the heat shield and the liquid surface of the raw material melt, the heat under the condition that the entire crystal surface becomes the N-region when the nitrogen is not doped. When the distance between the shield and the liquid level of the raw material melt is D, the interval D 'between the heat shield and the liquid level of the raw material melt when nitrogen is doped is D' / D = 0.94-nitrogen concentration depending on the nitrogen concentration. It is preferable to change it so that it becomes D 'calculated | required from / (2.41 * ¹⁰ <^15> ).

According to the Ge / Gc adjustment method, the Ge / Gc can be adjusted simply and accurately according to the nitrogen concentration, so that the Ge / Gc can be adjusted more easily by adjusting the gap between the heat shield and the liquid level of the raw material melt. Become.

At this time, when the calculated D 'is larger than 20 mm, the Ge / Gc is adjusted by setting the distance between the heat shield and the liquid level of the raw material melt to the calculated D', and the obtained D 'becomes 20 mm or less. The gap between the heat shield and the liquid level of the raw material melt is set to 20 mm, and further, the position of the heater disposed to surround the quartz crucible is lowered with respect to the liquid level of the raw material melt. It is preferable to adjust the Ge / Gc by any one or a combination of two or more of weakening the magnetic field strength of the magnetic field applying device disposed outside the main chamber, and lowering the position of the magnetic field applying device. .

In such a method for producing a silicon single crystal, the gap between the heat shield and the liquid level of the raw material melt does not become too narrow. Thus, the silicon single crystal can be produced without disturbing the pulling of the silicon single crystal by the heat shield.

In addition, the present invention is an epitaxial silicon wafer in which the entire crystal surface has an epitaxial layer on a silicon single crystal substrate having an N-region, wherein nitrogen is contained in the silicon single crystal substrate at 2 × 10 ¹³ atoms / cm ³ or more and 3.2 × 10. The number of defects doped at a concentration of ¹⁴ atoms / cm ³ or less, and the number of defects having a size of 28 nm or more was 2 / sheet or less as the total substrate average in a silicon single crystal block of 10 cm or more, and the heat treatment was performed at 800 ° C, 3hr + 1000 ° C and 2hr An epitaxial silicon wafer is provided, characterized in that a BMD of 45 nm or more in average size detected afterwards 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 defects, and EP defects due to plate- or rod-shaped COP when nitrogen-doped at a high concentration.

Moreover, this invention is the silicon single crystal board | substrate of the whole crystal surface which has a mirror-polished surface as N-region, and nitrogen dope in concentration of 2 * 10 <^13> atoms / cm <^3> or more and 3.2 * 10 <^14> atoms / cm <^3> or less The yield of TDDB characteristics is 90% or more, and the number of defects having a size of 45 nm or more is 2 / sheet or less as the total substrate average in a silicon single crystal block of 10 cm or more, and the heat treatment is performed at 800 ° C, 3hr + 1000 ° C, and 2hr. After that, a BMD having an average size of 45 nm or more detected and a density of 1 × 10 ⁸ / cm ³ or more are provided.

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.

According to the method for producing the silicon single crystal of the present invention, by doping nitrogen at a high concentration, the precipitated nucleus of a large size that is thermally stable is increased, while achieving a high BMD formation ability (gettering capability) even in a low temperature and short time device process, By modifying and adjusting the defect distribution change caused by high concentration of nitrogen due to segregation during crystal growth, it is possible to produce a silicon single crystal that avoids the R-OSF region even in a nitrogen concentration range having a large crystal total length.

Further, the epitaxial silicon wafer of the present invention is free of BMD density reduction due to the R-OSF region, EP defects, and EP defects due to plate- or rod-shaped COP due to high nitrogen concentration. In addition, with 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.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows an example of the manufacturing apparatus of the silicon single crystal by the Czochralski method which can be used for this invention.
Fig. 2 is a defect distribution diagram in the pulling axial direction of a silicon single crystal in which the silicon single crystal is the horizontal axis of the silicon single crystal when the silicon single crystal is manufactured under the pulling conditions of Comparative Example 1, Comparative Example 2 and Example 1; .
3 is an EP defect distribution diagram showing a result of defect evaluation of an epitaxial wafer in Comparative Example 3. FIG.
4 is an EP defect distribution diagram showing a result of defect evaluation of the epitaxial wafer in Comparative Example 4. FIG.
FIG. 5 is an EP defect distribution diagram showing a result of defect evaluation of an epitaxial wafer in Example 2. FIG.
It is a figure which shows the result of TDDB characteristic evaluation of the silicon single crystal substrate in the comparative example 5.
It is a figure which shows the result of TDDB characteristic evaluation of the silicon single crystal substrate in the comparative example 6.
It is a figure which shows the result of TDDB characteristic evaluation of the silicon single crystal substrate in Example 3. FIG.

EMBODIMENT OF THE INVENTION Hereinafter, although this invention is demonstrated in detail as an example of embodiment with reference to drawings, this invention is not limited to this.

On the other hand, the present inventors describe the method for producing the silicon single crystal, the epitaxial silicon wafer, and the silicon single crystal substrate of the present invention while describing the contents of the consideration and experiment until the present invention is devised.

As described above, in an epitaxial silicon wafer using a nitrogen-doped V-rich crystal for a substrate, the density of BMD due to the R-OSF region, EP defects, and nitrogen doping at a high concentration in the outer peripheral portion of the wafer In some cases, EP defects due to plate- or rod-shaped COPs may be a problem.

On the other hand, the inventors of the present invention have the R-OSF region as long as it is a silicon single crystal substrate of low / defective crystal manufactured in nitrogen doped N (Neutral) region as described in Patent Document 2 or an epitaxial silicon wafer using the same for the substrate. While solving the problem of lowering the BMD density due to the problem, it was thought that both the increase of thermally stable (large size) precipitation nuclei due to nitrogen doping and the low / no defect requirement of the wafer surface layer device operating area could be achieved.

However, based on this idea, when the inventors made the low / integrity crystals in the N-region by the Czochralski method during the intensive study, they did not carry out nitrogen doping. In this case, it was difficult to avoid the R-OSF region and faced a problem of a very low yield in one crystal.

Specifically, in the production of low / integrity crystals in the N-region that is not doped with nitrogen, a growth method for avoiding the R-OSF region and extracting the N-region at high yield in the entire axial length of the crystal growth. Even when using (Patent Documents 3 to 7), when nitrogen is doped, the production of low / defect-free crystals in the N-region in which R-OSF is avoided only in a part of the range where the nitrogen concentration is low in the total length of the crystal growth axis direction Could.

Further, as shown in Patent Document 8 relating to the production of low / defect-free crystals in the N-region doped with nitrogen, a 3 × 10 ¹³ atoms which makes it possible to provide a wafer having excellent TDDB characteristics and a small BMD density gap. Nitrogen concentrations below / cm ³ are insufficient to increase thermally stable (large sized) precipitation nuclei prior to the device process, and for high BMD density (gettering capability) in advanced low temperature, short time device processes. It did not satisfy the demand.

In addition, when the nitrogen concentration is set to a high nitrogen concentration of 3 × 10 ¹³ atoms / cm ³ or more sufficient to increase the thermally stable (large size) precipitation nuclei before the device process, the crystal center portion as described in Patent Document 2 Even when the difference between the temperature gradient Gc and the temperature gradient Ge of the crystal peripheral portion is ΔG = Ge-Gc ≦ 5 ° C./cm, as described in Patent Literature 9, the pulling rate according to the nitrogen concentration change due to segregation during crystal growth is described. R-OSF region is more likely to occur in the outer peripheral portion of the wafer even if the adjustment is made. If the crystal growth rate is lowered to avoid this, the number of BMDs in the wafer center portion decreases, resulting in uneven in-plane BMD density (gettering ability). In some cases, however, there has been a problem that the wafer center portion has an I-rich region having a dislocation loop or dislocation classifier.

In the face of these problems, the inventors have intensively studied, and as a result, in the production of low / defect-free crystals in the N-region doped with nitrogen, the defect region in the crystal periphery (crystal outer periphery) may depend on the nitrogen concentration. It was found that a change occurred.

Next, the change of the defect area | region in the crystal periphery part with nitrogen concentration is demonstrated concretely.

The change in the defect distribution due to factors other than the thermal environment of the crystal can be understood as being caused by outward diffusion of point defects, as described in Patent Document 10. In the crystal periphery, the influence of outward diffusion of point defects such as silicon and pores between the lattice is increased, and the outward diffusion of the pore reduces the residual pore concentration at the periphery of the crystal. However, when nitrogen is doped at a high concentration, the outward diffusion of the vacancy is suppressed by the formation of a pair of nitrogen and vacancy (NV pair).

For this reason, when nitrogen is doped as compared with the case where nitrogen is not doped, as the concentration of nitrogen increases, the residual porosity of the crystal periphery increases, and the defect region of the crystal periphery shifts toward the R-OSF region.

The inventors of the present invention found that, when a nitrogen-doped low-defect crystal is produced in an N-region, an R-OSF region tends to occur at the outer peripheral portion of the wafer, and the crystal growth rate is lowered to avoid it. This decreases the BMD of the surface and causes inhomogeneity of the in-plane BMD density (gettering ability), but in some cases, causes the problem of I-rich regions with dislocation loops or dislocation cutters at the wafer center. The effect of suppressing the outward diffusion of the vacancy was found from 2 × 10 ¹³ atoms / cm ^3, and when it became 3 × 10 ¹³ atoms / cm ³ or more, it was found that the level seriously affected the crystal yield.

The present invention has been completed by the inventors' intensive studies in this way, and the nitrogen segregation in a low / defect-free silicon single crystal substrate produced in the N-region of nitrogen dope and an epitaxial silicon wafer using the same for a substrate By growing crystals of silicon single crystals in consideration of the influence, and using the grown silicon single crystals to produce a silicon single crystal substrate and an epitaxial silicon wafer using the same, the problems caused by the R-OSF region are completely eliminated. It has been found that both the increase in thermally stable (large size) precipitation nuclei and low / defect-free requirements of the wafer surface layer device operating area are made possible, thereby reaching the present invention.

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

The present invention is a method of growing a silicon single crystal by pulling it under the condition that the entire crystal surface becomes an N-region by the Czochralski method. When growing a silicon single crystal, nitrogen is 2 × 10 ¹³ atoms / cm ³ or more 3.2 × 10 ¹⁴ atoms / cm ³ is doped with less nitrogen concentration, and the ratio of the temperature gradient Ge of the temperature gradient Gc and determining the peripheral portion of the crystal center of the pulling axis direction of the silicon single crystal so that the Ge / Gc> 1, Ge / Gc It is a method for producing a silicon single crystal, characterized in that gradually increasing as the concentration of nitrogen due to segregation at the time of pulling up the silicon single crystal. Here, the crystal peripheral portion is appropriately determined within an area of approximately 1/3 or less of the diameter from the outer peripheral end of the silicon single crystal.

In the silicon single crystal manufacturing method, by dope nitrogen at a high concentration, the precipitate nuclei of a large size which are thermally stable are increased, and crystal growth is achieved while achieving a high BMD formation ability (gettering ability) even in a low temperature and short time device process. By modifying and adjusting the defect distribution change caused by the high concentration of nitrogen due to segregation in the silicon, it is possible to produce a silicon single crystal which avoids the R-OSF region even in a nitrogen concentration range having a large crystal total length.

In addition, by using the silicon single crystal manufactured by the method for producing a silicon single crystal of the present invention, there is no harm due to the R-OSF region caused by doping at a high nitrogen concentration in the silicon single crystal substrate and the epitaxial silicon wafer using the same. Therefore, a wafer having a high BMD forming ability (gettering capability) can be obtained with a high yield even in a low temperature and short time device process.

When the temperature distribution during the crystal growth is adjusted so that the N-region is obtained in the entire crystal length and the entire surface when the nitrogen is not doped, the nitrogen dope amount is adjusted to a nitrogen concentration smaller than 2 x 10 ¹³ atoms / cm ³ . In this case, the influence on the defect distribution is slight, and 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 are rarely a problem.

However, when the nitrogen concentration is 3 × 10 ¹³ atoms / cm ³ , the effect on the defect distribution is observed, and the deterioration of the TDDB characteristics in the state of using the silicon single crystal substrate, or the EP in the epitaxial silicon wafer using the silicon single crystal substrate. Defect occurs. In addition, as described in Patent Document 9, even if the pulling speed is adjusted according to the nitrogen concentration (slowing speed is adjusted as the nitrogen concentration is increased), the nitrogen concentration is sufficient for low temperature and short time heat treatment used in an advanced device process. Density cannot be obtained.

A nitrogen concentration of 3 × 10 ¹³ atoms / cm ³ or more is effective for obtaining a sufficient BMD density by low temperature and short time heat treatment used in an advanced device process, but especially in a state where a defect distribution change is large in the crystal periphery and a silicon single crystal substrate is used. Further deterioration of the TDDB characteristics and the occurrence of EP defects in the epitaxial silicon wafer are weighted. In this nitrogen concentration range, it cannot be sufficiently improved by adjusting the pulling rate slowly with respect to the increase in nitrogen concentration of Patent Document 9, and the TDDB characteristics and epitaxial silicon wafer in the case of using a silicon single crystal wafer in the crystal outer peripheral portion If the pulling speed is lowered until the EP defects can be improved, the BMD of the wafer center portion decreases, resulting in non-uniformity of the in-plane BMD density (gettering ability), but in some cases, the potential loop or dislocation at the wafer center portion. EP defects occur in the center of the I-rich region with the cutter.

At nitrogen concentrations of 6 × 10 ¹³ atoms / cm ³ or more, it is more preferable to obtain a sufficient BMD density by low temperature and short time heat treatment used in advanced device processes, but the variation of defect distribution in the periphery of crystals is further increased, and the silicon single crystal substrate is used. The deterioration of TDDB characteristics in the state and the occurrence of EP defects in epitaxial silicon wafers using a silicon single crystal substrate are further increased. In this nitrogen concentration range, it cannot be sufficiently improved by adjusting the pulling speed slowly with respect to the nitrogen concentration increase of Patent Document 9, and using the TDDB characteristic or the silicon single crystal substrate in the state of using the silicon single crystal substrate in the crystal peripheral portion If the pulling speed is slowed down until the occurrence of EP defects in the epitaxial silicon wafer can be improved, the entire surface N-region cannot be maintained, and the wafer center portion becomes an I-rich region having a dislocation loop or dislocation classifier. EP defects occur at the center of the core.

According to the method for producing a silicon single crystal of the present invention, a silicon single crystal is produced by using a silicon single crystal manufactured to an optimum nitrogen concentration of 3.2 × 10 ¹⁴ atoms / cm ³ to obtain a sufficient BMD density by low temperature and short time heat treatment used in an advanced device process. The TDDB characteristic at the time of manufacturing a board | substrate is favorable, and the wafer which does not produce EP defect in the state which set it as the epitaxial silicon wafer using this silicon single crystal board | substrate can be obtained.

In the present invention, for example, a silicon single crystal manufacturing apparatus 14 as shown in FIG. 1, which can be grown by raising the silicon single crystal by the Czochralski method under conditions where the entire crystal surface becomes an N-region. A single crystal manufacturing apparatus is used. Although the silicon single crystal manufacturing apparatus is described with reference to FIG. 1, the single crystal manufacturing apparatus which can be used in this invention is not limited to this.

The external appearance of the silicon single crystal manufacturing apparatus 14 shown in FIG. 1 is comprised by the main chamber 1 and the pulling chamber 2 which communicates with this. Inside the main chamber 1, a graphite crucible 6 and a quartz crucible 5 are provided. The heater 7 is provided so that the graphite crucible 6 and the quartz crucible 5 may be enclosed, and the raw material polycrystalline polycrystal accommodated in the quartz crucible 5 is melted by the heater 7 to become the raw material melt 4. Moreover, the heat insulating member 8 is provided and the influence of the radiant heat from the heater 7 to the main chamber 1 etc. is prevented.

On the melt surface of the raw material melt 4, the heat shield 12 is disposed facing the melt surface at a predetermined interval 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 out from the raw material melt 4. The crucible is capable of lifting in the axial direction of crystal growth, and by raising the crucible during growth to compensate for the lowering of the liquid melt of the raw material melt 4 in which the growth of the single crystal proceeds, the height of the melt surface of the raw material melt 4 is approximately constant. Is maintained.

In addition, an inert gas such as argon gas is introduced from the gas inlet 10 as a purge gas at the time of single crystal growth, and passes between the single crystal rod 3 and the gas rectifying cylinder 11 during pulling, and then the heat shield body. It passes between the melt surface of the 12 and the raw material melt 4, and is discharged | emitted 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 the valve, the pressure in the chamber during the pulling is controlled.

In addition, in growing a crystal by the CZ method, a magnetic field may be applied by the magnetic field applying device 13.

Here, the temperature gradient Gc of the crystal center portion in the pulling axis direction of the silicon single crystal and the temperature gradient Ge of the crystal periphery portion are Ge / Gc> 1, and Ge / Gc is the concentration of nitrogen due to segregation during the pulling of the silicon single crystal. As you increase, explain why you can increase it slowly.

As the concentration of nitrogen increases due to segregation, NV pair formation increases, decreasing the outward diffusion of vacancy to the outer surface of the crystal and increasing the residual vacancy concentration around the crystal. Shift to the defective area.

As long as the defect region around the crystal shifts to the vacancy dominant side due to segregation of nitrogen, the residual Vacancy concentration around the crystal is larger than the residual Vacancy concentration of the crystal center to r / 2 (where r is the radius of the silicon single crystal). The non-uniformity of the BMD distribution or the shift from the N-region of the defective region to the R-OSF region occurs in the outer peripheral portion.

In order to avoid this, it is effective to adjust the amount by which the amount of residual Vacancy is increased around the crystal due to the effect of NV pair formation to the amount of Vacancy intake of the high liquid interface.

That is, the amount of Vacancy blown in the crystal periphery portion is made smaller than the amount of Vacancy blown in the portion other than the crystal periphery of the solid-state interface.

As to the incorporation of point defects in silicon single crystal growth, boronkov's theory is widely known, and the concentration of point defects is determined depending on the growth rate V of the silicon single crystal and the ratio V / G of the temperature gradient G near the interface.

With respect to V / G where the vacancy concentration and the interstitial-Si concentration are antagonistic, a large V / G increases the Vacancy concentration at the liquid-liquid interface, and a small V-G increases the interstial-Si concentration at the solid-liquid interface.

For this reason, the V / Ge of the crystal periphery is set to be smaller than the V / Gc of the center in advance as much as the residual Vacancy increases around the crystal due to the effect of NV pair formation. In other words,

V / Gc> V / Ge

Shall be.

During normal single crystal growth, the growth rate V in the plane perpendicular to the crystal growth axis direction is the same from the crystal center to the crystal periphery, so it is effective to set 1 / Gc> 1 / Ge and Ge / Gc> 1, and the nitrogen concentration is effective. As it increases, the amount of residual Vacancy in the crystal periphery increases due to the effect of NV pair formation, thereby making it possible to offset Ge / Gc gradually. At this time, if Ge / Gc is 1.2 or less, it is preferable because the entire surface of the wafer can be made more sure.

The adjustment of Ge / Gc is performed by controlling a gap between the heat shield 12 disposed directly above the raw material melt in the quartz crucible 5 and the liquid level of the raw material melt, and a heater arranged to surround the quartz crucible 5 ( 7) lowering the position of the raw material melt relative to the liquid level, weakening the magnetic field strength of the magnetic field applying device 13 disposed outside the main chamber 1 of the silicon single crystal manufacturing apparatus, 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 thereof. According to the Ge / Gc adjustment method, since the manufacturing apparatus is not greatly changed, it is possible to easily adjust Ge / Gc.

The reason why Ge / Gc is increased by this Ge / Gc adjustment method is explained.

There are two methods of increasing Ge / Gc, a method of increasing Ge and a method of decreasing Gc.

In order to increase Ge, it is effective to reduce heat radiation (heat supply by radiation) to the crystal side portion of the upper portion of the solid-liquid interface. As a specific method, the heater 7 for heating the heat source disposed outside the graphite crucible 6 by narrowing the gap between the heat shield 12 immediately above the raw material melt 4 and the liquid level of the raw material melt 4. A method of shielding part of the heat radiation from the heat sink, and a method of reducing the heat radiation to the upper part of the solid-liquid interface by arranging the heater 7 for heating the heat source lower than the liquid surface position of the raw material melt 4.

On the other hand, the Ge changes slightly due to the heat conduction of the furnace gas and the convective heat transfer due to the flow of the gas.However, the heat radiation is dominant in the silicon single crystal manufacturing environment by the CZ method, which is mainly a room temperature environment of melting temperature of 1420 ° C or higher. Control becomes important.

The method of decreasing Gc lowers the height of the solid-liquid interface (warm temperature, such as melting point), and becomes a method of relieving the temperature gradient with the upper portion of the solid-liquid interface, and weakens the suppression of the melt convection under the crystal growth interface by the magnetic field, The latent heat of coagulation generated during crystal growth can be easily removed from convection. When the latent heat of coagulation is removed by convection, the height of the solid-liquid interface is lowered by heat balance as compared with the case where it is not. At this time, since the hot line such as the melting point of the outermost part of the crystal always leads to the surface of the raw material melt 4, the Gc becomes selectively small.

As a method of weakening the suppression of the melt convection under the crystal growth interface by the magnetic field, there is a method of weakening the magnetic field strength when the magnetic field positions remain the same. In the case where the magnetic field strength is fixed, there is a method in which the magnetic field position is far 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, although the solid-liquid interface can be reduced by weakening the crystal rotation, a method of weakening the magnetic field strength of the solid-liquid interface is preferable because it leads to unevenness of the dopant concentration and the oxygen concentration in the surface. .

In addition, when Ge / Gc is adjusted by controlling the interval between the liquid level of the heat shield 12 and the raw material melt 4, the heat under the condition that the entire crystal surface becomes the N-region when nitrogen is not doped. When the gap between the shielding body 12 and the raw material melt 4 is set to D, the gap between the heat shield 12 and the raw material melt 4 when the nitrogen is doped is determined according to the nitrogen concentration. It is preferable to change so that it becomes D 'calculated | required from /D=0.94-nitrogen concentration / (2.41 * ¹⁰ <^15> ).

According to the Ge / Gc adjustment method, the Ge / Gc can be adjusted by adjusting the gap between the heat shield 12 and the raw material melt 4 in accordance with the nitrogen concentration. It becomes possible to adjust.

How did you derive this D 'relationship?

First, as the distance D between the heat shield 12 immediately above the raw material melt 4 from which the N-region is obtained from the entire surface and the melt, when nitrogen is not doped, 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 , 3-3.2 × 10 ¹⁴ atoms / cm ³ In the silicon single crystal block, defect regions V-rich, R-OSF region, Nv region, Ni region, and I- A rich region was included, and a sample parallel to the crystal growth axis direction was cut out from the obtained silicon single crystal block, and subjected to a heat treatment at 800 ° C. 4hr + 1000 ° C. for 16hr in a wet oxidation atmosphere, and subjected to X-ray topography (XRT). The change of defect distribution by nitrogen concentration was investigated.

Second, at each nitrogen concentration, the raw material from which the gap between the heat shield 12 and the raw material melt 4 directly above the raw material melt 4 and the liquid level is changed, and an N-region distribution equivalent to the case where no nitrogen is doped is obtained. The distance D 'between the heat shield 12 immediately above the melt 4 and the liquid level of the raw material melt 4 was determined.

Third, the relational expression of the change of the ratio of the gap D 'and the ratio of the gap D between the heat shield 12 and the raw material melt 4 to the nitrogen concentration was determined by the least square method, and D' / D = 0.94-nitrogen concentration / (2.41 × 10 ¹⁵ ) was obtained.

When the calculated D 'is larger than 20 mm, Ge / Gc is adjusted by setting the distance between the heat shield 12 and the liquid level of the raw material melt 4 to be D', and when the calculated D 'becomes 20 mm or less, The distance between the shield surface 12 and the liquid level of the raw material melt 4 is 20 mm, and the position of the heater 7 arranged to surround the quartz crucible 5 is lowered relative to the liquid level of the raw material melt 4. Weakening the magnetic field strength of the magnetic field applying device 13 disposed 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.

According to the method for producing a silicon single crystal, when the gap between the heat shield 12 and the liquid level of the raw material melt 4 is narrowed to 20 mm or less, the silicon single crystal is brought into contact with the raw material melt 4 by, for example. The silicon single crystal can be manufactured without disturbing the impression of.

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 having an N-region on its entire crystal surface, wherein the silicon single crystal substrate has nitrogen of 2 × 10 ¹³ atoms / cm ³ or more. Number of defects doped with a nitrogen concentration of 3.2 x 10 ¹⁴ atoms / cm ³ or less and a size of 28 nm or more is 2 / sheet or less (0 / sheet or more and 2 / sheet or less) as the total substrate average in a silicon single crystal block of 10cm or more. And an average size of 45 nm or more of BMD detected after a heat treatment of 800 ° C., 3 hr + 1000 ° C., and 2 hr is a density of 1 × 10 ⁸ / cm ³ or more. At this time, if BMD is a density of 1x10 <^10> / cm <^3> or less, since BMD density becomes moderate and wafer curvature etc. do not become a problem, it is preferable.

With such an epitaxial silicon wafer, there is no decrease in BMD density due to the R-OSF region, EP defects, and EP defects due to plate- or rod-shaped COP due to high concentration of nitrogen dope. Moreover, sufficient BMD density is formed by heat processing of 800 degreeC, 3hr + 1000 degreeC, and 2hr, and it becomes an epitaxial silicon wafer with uniform in-plane BMD quality.

In addition, according to the method of the present invention, the entire surface of the crystal having the mirror-polished surface is a silicon single crystal substrate having an N-region, wherein nitrogen is 2 × 10 ¹³ atoms / cm ³ or more and 3.2 × 10 ¹⁴ atoms / cm ³ or less Number of defects doped at a concentration, yield of TDDB characteristics of 90% or more, and size of 45 nm or more is 2 / sheet or less (0 / sheet or more, 2 / sheet or less) as the total substrate average in a silicon single crystal block of 10 cm or more. And a BMD having an average size of 45 nm or more detected after the heat treatment at 800 ° C., 3 hr + 1000 ° C., and 2 hrs has a density of 1 × 10 ⁸ / cm ³ or more. At this time, if the BMD is 1 × ¹⁰ 10 / cm ³ or less dense, it becomes suitable for the BMD density, it is preferable because it is such as wafer warpage is not a problem.

With such a silicon single crystal substrate, there is no decrease in the BMD density attributable to the R-OSF region, and the TDDB characteristics are good. Moreover, sufficient BMD density is formed by heat processing of 800 degreeC, 3hr + 1000 degreeC, and 2hr, and it becomes a silicon single crystal substrate with uniform in-plane BMD quality.

Example

Hereinafter, although an Example and a comparative example are given and this invention is concretely demonstrated, this invention is not limited to these.

(Comparative Example 1)

410 kg of raw material was melted in a 32 inch (812.8 mm) crucible without being doped with nitrogen, and crystals having a diameter of 300 mm were produced under a magnetic field application of 4000 g. At this time, the gap (50mm) between the heat shield directly above the raw material melt and the raw material melt, the position of the heater, and the position of the magnetic field applying device are adjusted, so that the N (Neutral) region is obtained in the entire surface over the entire crystal length. The temperature distribution was adjusted. Under this condition, the pulling speed is gradually decreased during the linear motion growth, and the defect regions V-rich, R-OSF region, Nv region, Ni region, and I-rich region (V-rich to I-rich region) in the silicon single crystal block are gradually reduced. Area), a sample parallel to the crystal growth axis direction is cut out from the obtained silicon single crystal block, and subjected to a heat treatment at 800 ° C. 4hr + 1000 ° C. for 16hr in a wet oxidation atmosphere, and subjected to defects by XRT (X-ray Topography). The distribution was evaluated.

(Comparative Example 2)

In the silicon single crystal block by doping nitrogen and gradually decreasing the pulling speed during the linear growth in the gap (50 mm), heater position, magnetic field position, and magnetic field strength between the heat shield directly on the raw material melt and the raw material melt as in Comparative Example 1. A defect distribution evaluation silicon single crystal block containing each region of I-rich was prepared from V-rich. The nitrogen concentration is 2 × 10 ¹³ atoms / cm ³ level (nitrogen concentration 2 × 10 ¹³ -2.2 × 10 ¹³ atoms / cm ^{3 in} silicon single crystal block), 3 × 10 ¹³ atoms / cm ³ level (nitrogen in silicon single crystal block) Concentration 3 × 10 ¹³ -3.2 × 10 ¹³ atoms / cm ³ ), 6 × 10 ¹³ atoms / cm ³ level (nitrogen concentration 6 × 10 ¹³ -6.2 × 10 ¹³ atoms / cm ^{3 in} silicon single crystal block), 3 × 10 Each silicon single crystal block was produced at a level of ¹⁴ atoms / cm ³ (nitrogen concentration in silicon single crystal block 3 × 10 ¹⁴ -3.2 × 10 ¹⁴ atoms / cm ³ ), and the defect distribution at each nitrogen concentration was compared. And evaluated in the same manner.

(Example 1)

It carried out similarly to the comparative example 2 except having set D 'calculated | required from D' / D = 0.94-nitrogen concentration / 2.41 * ¹⁰ < ¹⁵ >, and the space | interval of the heat shield body directly above a raw material melt. By varying the gap between the heat shield directly above the raw material melt and the liquid level of the raw material melt, the temperature gradient Gc of the crystal center in the pulling axis direction of the silicon single crystal and the temperature gradient Ge of the crystal periphery are made Ge / Gc> 1. Ge / Gc was gradually increased with increasing nitrogen concentration due to segregation during pulling up of the silicon single crystal. Where D is 50 mm. The gap between the heat shield directly above the raw material melt and the liquid level of the raw material melt is set to D '= 46.6 mm (D') at the level of 2 × 10 ¹³ atoms / cm ³ (nitrogen concentration 2-2.2 × 10 ¹³ atoms / cm ^{3 in the} silicon single crystal block). ^{/D=0.932), 3 × 10 13 atoms} / cm 3 levels (in the nitrogen concentration of the silicon single crystal block ^{3-3.2 × 10 13 atoms / cm 3} ) D '= 46.3mm (D' / D = 0.926), 6 × At the 10 ¹³ atoms / cm ³ level (nitrogen concentration 6-6.2 × 10 ¹³ atoms / cm ^{3 in the} silicon single crystal block), D '= 45.8 mm (D' / D = 0.916) and 3 × 10 ¹⁴ atoms / cm ³ levels ( At a nitrogen concentration of 3-3.2 × 10 ¹⁴ atoms / cm ³ in a silicon single crystal block, a silicon single crystal block was produced with D '= 40.8 mm (D' / D = 0.816), and the heat shielding body immediately above the raw material melt at each nitrogen concentration. And defect distribution when the gap between the liquid level of the raw material melt and the raw material melt were adjusted. The change of the space | interval of the heat shield body directly above a raw material melt and the liquid level of a raw material melt was implemented according to the change of the height position of a crucible.

Fig. 2 shows a defect distribution diagram in the pulling axial direction of a silicon single crystal in which the silicon single crystal is the horizontal position of the silicon single crystal when the silicon single crystal is manufactured under the pulling conditions of Comparative Example 1, Comparative Example 2 and Example 1. Indicates.

For Comparative Example 1, the defect distribution of Comparative Example 2 which was doped with nitrogen was 2 × 10 ¹³ atoms / cm ³ level of nitrogen, 3 × 10 ¹³ atoms / cm ³ level, and 6 × 10 ¹³ atoms / cm ³ level. , At 3x10 ¹⁴ atoms / cm ³ , the outward diffusion of the vacancies during crystal growth is reduced by the formation of a pair of nitrogen and vacancies as the concentration of nitrogen increases. The defect area is shifted to the vacancy dominant side (high V / G side), and the R-OSF area is changed to a sag distribution at the outer peripheral part.

In such a defect distribution, when manufacturing a wafer, a defect region with a large difference in residual Vacancy concentration in the plane is mixed (R-OSF region + R / 2-center portion Nv region of outer peripheral portion, Nv region + R / 2-center portion of outer peripheral portion). Even if the Ni region, the R-OSF region of the outer peripheral portion + the Nv region of the R / 2 portion + the Ni region of the center portion) or the Nv region in the entire in-plane, the wafer outer periphery increases the residual Vacancy. As a result, the in-plane BMD (Bulk Micro Defect) density after 800 ° C, 3hr + 1000 ° C, and 2hr heat treatment is significantly different, and the device yield decreases due to lack of gettering capability in the low BMD region in the wafer surface. It is such a factor.

In contrast, in Example 1 of the present invention, the defect distribution change (defect region on the outer circumferential side shifts to the Vacancy dominant side and the R-OSF region changes on the sag distribution on the outer circumferential side) with increasing nitrogen concentration is corrected. When the wafer is fabricated, the entire surface in the wafer surface can be made into a uniform defect area, so that the BMD density in the wafer surface is uniformly controlled after a low temperature, a short time, for example, 800 ° C, 3hr + 1000 ° C, and 2hr heat treatment can do. In addition, in terms of device yield and wafer, the TDDB characteristics in the silicon single crystal substrate state due to the mixed R-OSF region and the EP defect in the case where the manufactured silicon single crystal substrate is used for the epitaxial silicon wafer substrate can also be suppressed. Yield is good.

In addition, nitrogen is gradually concentrated due to segregation phenomenon (equilibrium segregation coefficient of 7 × 10 ⁻⁴ ) during crystal growth, and therefore, it is gradually concentrated to increase the yield. The invention becomes very effective.

[Quality Change of Epitaxial Silicon Wafer (Quality Trend in One Silicon Single Crystal)]

Next, the yield of an epitaxial wafer will be described in detail with reference to the effect obtained when the present invention is applied to actual product manufacturing.

(Comparative Example 3)

A 410 kg raw material was melted in a 32 inch (812.8 mm) crucible, and crystallization of 300 mm in diameter was performed under a magnetic field of 4000 g. Adjust the heater position and the position of the magnetic field application device during crystal growth so that the gap between the heat shield directly above the raw material melt and the liquid surface of the raw material melt is 50 mm over the entire length of the crystal when nitrogen is not doped. Under one condition, in the linear motion product collecting section, nitrogen non-dope (Comparative Example 3-1), nitrogen concentration of 2 × 10 ¹³ -6 × 10 ¹³ atoms / cm ³ (Comparative Example 3-2), 1 × 10 Three crystals are produced so as to have a nitrogen concentration of ¹⁴ -3.2 x 10 ¹⁴ atoms / cm ³ (Comparative Example 3-3), and a silicon single crystal substrate is produced from the obtained crystals, and is used as an epitaxial silicon wafer substrate. The silicon wafer was manufactured. For defect evaluation of epitaxial silicon wafers, defects detected at 28 nm or more in Oblique mode were evaluated using SP3 manufactured by KLA Tencor. In addition, the BMD density of 30 nm or more was measured by the infrared scattering method after heat-processing the produced epitaxial wafer at 800 degreeC, 3hr + 1000 degreeC, and 2hr.

(Comparative Example 4)

As the gap between the heat shield directly above the raw material melt and the liquid level of the raw material melt is 50 mm, as described in Patent Literature 9, the pulling speed is adjusted according to the nitrogen concentration (the pulling speed is slowed down to increase the nitrogen concentration). Other than the same thing as the comparative example 3-2 (comparative example 4-1), and the same as the comparative example 3-3 (comparative example 4-2), similarly to the comparative example 3, an epitaxial silicon wafer was manufactured, The defect evaluation was performed. In addition, the BMD density of 30 nm or more was measured by the infrared scattering method after heat-processing the produced epitaxial wafer at 800 degreeC, 3hr + 1000 degreeC, and 2hr.

(Example 2)

The distance D '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} ). Example ^{2-1, 2 × 10 13 -6 × 10} 13 with a nitrogen concentration of atoms / cm ^3, the determination in the segregation of the nitrogen in the Tail side from koncheuk determined to offset the effect of the nitrogen segregation foster According to the nitrogen concentration change, D '= 46.6mm to 45.8mm, except that the gap between the heat shield directly on the raw material melt and the liquid level of the raw material melt was adjusted to be the same as in Comparative Example 4-1. Comparative Example 4- with a nitrogen concentration of 1 × 10 ¹⁴ -3.2 × 10 ¹⁴ atoms / cm ³ except that the gap between the heat shield directly above the raw material melt and the liquid level of the raw material melt was adjusted to D '= 44.9 mm to 40.3 mm. It was set as the same as 2, and similarly to the comparative example 3, the epitaxial wafer was manufactured and defect evaluation was performed. In addition, the BMD density of 30 nm or more was measured by the infrared scattering method after heat-processing the produced epitaxial wafer at 800 degreeC, 3hr + 1000 degreeC, and 2hr. By changing the gap between the heat shield directly above the raw material melt and the liquid level of the raw material melt in this manner, the temperature gradient Gc of the crystal center in the pulling axis direction of the silicon single crystal and the temperature gradient Ge of the crystal periphery are made Ge / Gc> 1. Ge / Gc was gradually increased with increasing nitrogen concentration due to segregation during pulling up of the silicon single crystal.

3, 4, and 5 are EP defect distribution diagrams showing the results of defect evaluation of the epitaxial wafers in Comparative Example 3, Comparative Example 4, and Example 2, respectively. In high-end devices with high process costs, even if several defects per wafer, a defective chip caused by this becomes a big problem.

In Comparative Example 3, the occurrence of EP defects is rarely a problem up to a nitrogen concentration of 2 × 10 ¹³ atoms / cm ³ , but a 3 × that is high enough to increase thermally stable (large sized) precipitation nuclei. When the nitrogen concentration was 10 ¹³ atoms / cm ³ , EP defects were observed. Further, at 3 × 10 ¹³ atoms / cm ³ or more having a high nitrogen concentration, the EP defects increase with the increase of the nitrogen concentration, and the level is unbearable for use in high-end devices with high process cost. In Comparative Examples 3-1, 3-2, and 3-3, the BMD densities of the epitaxial silicon wafers after heat treatment at 800 ° C, 3hr + 1000 ° C, and 2hr were 1-3x10 ⁷ and 1, respectively. -2x10 <^8> and 2.5-15 * 10 <^8> / cm <^3> . At a nitrogen concentration of 2 × 10 ¹³ atoms / cm ³ or more, a BMD density of 45 nm or more of an average size of 45 nm or more, which is considered to have sufficient gettering capability in advanced devices, could be made 1 × 10 ⁸ or more.

In Comparative Example 4, although the improvement effect is shown by lowering the pulling rate with respect to the increase in the nitrogen concentration, the nitrogen concentration of 6 × 10 ¹³ atoms / cm ³ or more is more preferable for obtaining a sufficient BMD density by low temperature and short time heat treatment used in an advanced device process. EP defects start to increase, and at nitrogen 1 × 10 ¹⁴ atoms / cm ³ or more, the level is not suitable for use in advanced devices. Furthermore, when the pulling speed is lowered, when the heat treatment is performed at 800 ° C., 3 hr + 1000 ° C., and 2 hr, the BMD of the wafer center portion decreases, causing unevenness of in-plane BMD density (gettering capacity). In some cases, an I-rich region having a dislocation loop or dislocation classer at the center of the wafer, and an EP defect occurred at the center portion, it was impossible to completely suppress the EP defect only by adjusting the pulling rate with respect to the nitrogen concentration. In Comparative Examples 4-1 and 4-2, the BMD densities of the epitaxial silicon wafers after heat treatment at 800 ° C, 3hr + 1000 ° C, and 2hr were 1-2 × 10 ⁸ , and 2.5-15, respectively. X10 ⁸ / cm ³ . At a nitrogen concentration of 2 × 10 ¹³ atoms / cm ³ or more, a BMD density of 45 nm or more of an average size of 45 nm or more, which is considered to have sufficient gettering capability in advanced devices, could be made 1 × 10 ⁸ or more.

On the other hand, in Example 2, EP defects can be suppressed to a favorable level up to nitrogen concentration of 3.2x10 <^14> atoms / cm <^3> . As a result, the defect at 28 nm or more is a very good defect level of 2 / sheet or less as the total substrate average in a silicon single crystal block of 10 cm or more, and an epitaxial silicon wafer having fewer defects than Comparative Examples 3 and 4 can be obtained. 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 a nitrogen concentration of 2 × 10 ¹³ atoms / cm ³ or more, which is considered to have sufficient gettering capability in advanced devices, can be set to 1 × 10 ⁸ / cm ³ or more. On the other hand, since the EP defect generation attributable to the precipitate may occur at a nitrogen concentration of 3.5 × 10 ¹⁴ atoms / cm ³ , the nitrogen concentration is preferably 3.2 × 10 ¹⁴ atoms / cm ³ or less.

Thus, by using the present invention, an epitaxial silicon wafer having a good EP defect level is very high in the crystal total length even in a high nitrogen concentration condition where high gettering capability can be expected in an advanced low temperature and short time device process. It becomes possible to manufacture in yield.

[Quality Change of Silicon Single Crystal Substrate (Quality Trend in One Silicon Single Crystal)]

Next, the yield of the silicon single crystal substrate will be described in detail with reference to the effect obtained when the present invention is applied to actual product manufacturing.

(Comparative Example 5)

A 410 kg raw material was melted in a 32 inch (812.8 mm) crucible, and crystallization of 300 mm in diameter was performed under a magnetic field of 4000 g. The position of the heater and the magnetic field applying device during crystal growth so that the N (Nututral) region is obtained over the entire length of the crystal when the nitrogen is not doped, and the gap between the heat shield directly above the raw material melt and the liquid surface of the raw material melt is 50 mm. Under the condition of adjusting, the nonlinear dope (Comparative Example 5-1), nitrogen concentration of 2 × 10 ¹³ -6 × 10 ¹³ atoms / cm ³ (Comparative Example 5-2), 1 Three crystals were produced so as to have a nitrogen concentration (Comparative Example 5-3) of × 10 ¹⁴ -3.2 × 10 ¹⁴ atoms / cm ³ , a silicon single crystal substrate was produced from the obtained crystals, and the TDDB characteristics were evaluated. In addition, in order to evaluate the defect of a silicon single crystal substrate, the defect detected by 45 nm or more in Oblique mode was evaluated using SP3 by KLA Tencor. In addition, the BMD density of 30 nm or more was measured by the infrared scattering method after heat processing of the produced silicon single crystal board | substrate at 800 degreeC, 3hr + 1000 degreeC, and 2hr.

(Comparative Example 6)

As described in Patent Literature 9, the pulling speed was adjusted according to the nitrogen concentration (slowing the speed of the nitrogen concentration increase) as described in Patent Literature 9, with the gap between the heat shield directly above the raw material melt and the liquid level of the raw material melt being 50 mm. Is the same as Comparative Example 5-2 (Comparative Example 6-1) and the same as Comparative Example 5-3 (Comparative Example 6-2), and the TDDB characteristics and defects of the silicon single crystal substrate manufactured in the same manner as Comparative Example 5 Was evaluated. In addition, the BMD density of 30 nm or more was measured by the infrared scattering method after heat processing of the produced silicon single crystal board | substrate at 800 degreeC, 3hr + 1000 degreeC, and 2hr.

(Example 3)

The gap between the heat shield and the liquid level of the raw material melt immediately above the raw material melt was taken as D 'obtained from D' / D = 0.94-nitrogen concentration / (2.41 × ^{10 15} ). Example ^{3-1, 2 × 10 13 -6 × 10} 13 with a nitrogen concentration of atoms / cm ^3, the determination in the segregation of the nitrogen in the Tail side from koncheuk determined to offset the effect of the nitrogen segregation foster Example 3-2 was carried out in the same manner as in Comparative Example 6-1 except that the gap between the heat shield directly above the raw material melt and the liquid level of the raw material melt was adjusted to D '= 46.6 mm to 45.8 mm in accordance with the nitrogen concentration change. Comparative Example 6- except that the gap between the heat shield directly above the raw material melt and the liquid level of the raw material melt was adjusted to a nitrogen concentration of 1 × 10 ¹⁴ -3.2 × 10 ¹⁴ atoms / cm ³ at D '= 44.9 mm to 40.3 mm. It was set as the same as 2, and similarly to the comparative example 5, the silicon single crystal board | substrate was produced and TDDB characteristic and the defect were evaluated. In addition, the BMD density of 30 nm or more was measured by the infrared scattering method after heat processing of the produced silicon single crystal board | substrate at 800 degreeC, 3hr + 1000 degreeC, and 2hr. By changing the gap between the heat shield directly above the raw material melt and the liquid level of the raw material melt in this manner, the temperature gradient Gc of the crystal center in the pulling axis direction of the silicon single crystal and the temperature gradient Ge of the crystal periphery are made Ge / Gc> 1. Ge / Gc was gradually increased with increasing nitrogen concentration due to segregation during pulling up of the silicon single crystal.

6, 7, and 8 are figures which show the result of TDDB characteristic evaluation of the silicon single crystal substrate in Comparative Example 5, Comparative Example 6, and Example 3, respectively.

6, 7, and 8, the gray cell is a TDDB defective point. The TDDB defect defect is related to the EP defect source, and has the same result as the evaluation (FIGS. 3, 4, and 5) of the EP defects of Comparative Example 3, Comparative Example 4, and Example 2. In the comparative example 5, TDDB defects gradually increase with nitrogen concentration of 3x10 <^13> atoms / cm <^3> or more as nitrogen concentration increases. The yield of the TDDB characteristic in the comparative example 5 was 99.7-99.3, 99.3-69.2, and 50.7-14.7% in the comparative example 5-1, the comparative example 5-2, and the comparative example 5-3, respectively. In Comparative Examples 5-1, 5-2, and 5-3, the defects at 45 nm or more are 1-2, 1.8-158, and 73- in the total substrate mean in the silicon single crystal block of 10 cm or more. 1250 / sheet. In Comparative Examples 5-1, 5-2, and 5-3, the BMD densities of the silicon single crystal substrates after heat treatment at 800 ° C, 3hr + 1000 ° C, and 2hr were 1-3x10 ⁷ and 1-, respectively. 2 * 10 <^8> and 2.5-15 * 10 <^8> / cm <^3> . At a nitrogen concentration of 2 × 10 ¹³ atoms / cm ³ or more, a BMD density of 45 nm or more in average size, which is expected to have sufficient gettering capability in advanced devices, could be set to 1 × 10 ⁸ or more.

In Comparative Example 6, similarly to the tendency of the EP defects, the improvement effect was observed in Comparative Example 5, but it could not be completely improved, and TDDB defects increased and worsened from a nitrogen concentration of 6 × 10 ¹³ atoms / cm ³ or more. . The yield of the TDDB characteristic in the comparative example 6 was 99.7-87.3 and 69.9-51.7% in the comparative example 6-1 and the comparative example 6-2, respectively. In addition, the defect in 45 nm or more in Comparative Example 6-1 and Comparative Example 6-2 was 1-57 piece / sheet, and 160-364 piece / sheet in the total board average in a silicon single crystal block of 10 cm or more. In Comparative Examples 6-1 and 6-2, the BMD densities of the silicon single crystal substrates after heat treatment at 800 ° C, 3hr + 1000 ° C, and 2hr were 1-2 × 10 ⁸ , and 2.5-15 ×, respectively. 10 ⁸ / cm ³ . At a nitrogen concentration of 2 × 10 ¹³ atoms / cm ³ or more, a BMD density of 45 nm or more of an average size of 45 nm or more, which is considered to have sufficient gettering capability in advanced devices, could be made 1 × 10 ⁸ or more.

In contrast, in Example 3, TDDB defects can be suppressed up to a nitrogen concentration of 3.2 × 10 ¹⁴ atoms / cm ³ . The yield of the TDDB characteristic in Example ³ was 99.7-99.3%, respectively in the range of nitrogen concentration 2-3.2x10 <^14> atoms / cm <^3> in Example 3-1 and Example 3-2. In addition, the defect in 45 nm or more in Example 3-1 and Example 3-2 was 1-1.9, and 1.2-2 piece / sheet by the total board average in a silicon single crystal block of 10 cm or more. In addition, in Example 3-1 and Example 3-2, the BMD density of the silicon single crystal substrate after heat treatment at 800 ° C, 3hr + 1000 ° C, and 2hr was 1-2x10 ⁸ , and 2.5-15x, respectively. 10 ⁸ / cm ³ . At a nitrogen concentration of 2 × 10 ¹³ atoms / cm ³ or more, a BMD density of 45 nm or more in average size, which is considered to have sufficient gettering capability in advanced devices, can be 1 × 10 ⁸ or more.

Thus, by using the present invention, a silicon single crystal substrate having an excellent defect level without increasing TDDB defects even under high nitrogen concentration conditions in which high gettering capability can be expected in an advanced low temperature and short time device process, It is possible to produce a very high yield in the total crystal length.

As described above, when the present invention is used, the nitrogen concentration of 3 × 10 ¹³ atoms / cm ³ to 3.2 × 10 ¹⁴ atoms / cm ³ , which is optimal for obtaining sufficient BMD density by low temperature and short time heat treatment used in an advanced device process, A wafer having a good TDDB characteristic in a state where the silicon single crystal substrate is used and no EP defect occurrence in the epitaxial silicon wafer can be obtained.

In addition, this invention is not limited to the said embodiment. The said embodiment is an illustration, Any thing which has a structure substantially the same as the technical idea described in the claim of this invention, and shows the same effect is included in the technical scope of this invention.

1: main chamber
2: impression chamber
3: single crystal rod
4: raw material melt
5: quartz crucible
6: graphite crucible
7: heater
8: insulation
9: gas outlet
10: gas inlet
11: gas rectifier
12: heat shield
13: Magnetic field applying device
14: apparatus for manufacturing silicon single crystal

Claims (6)

As a method of growing a silicon single crystal by the Czochralski method, the whole surface of the crystal is pulled under the condition of forming an N-region,
When growing the silicon single crystal, nitrogen is doped at a 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 of the crystal center portion in the pulling axis direction of the silicon single crystal to the temperature gradient Ge of the crystal peripheral portion is such that Ge / Gc >
The Ge / Gc is gradually increased as the nitrogen concentration increases due to segregation during pulling up of the silicon single crystal. The method of claim 1,
The Ge / Gc adjustment is performed by controlling the gap between the heat shield disposed directly above the raw material melt in the quartz crucible and the liquid level of the raw material melt, and the position of the heater disposed to surround the quartz crucible at the liquid level of the raw material melt. Lowering the magnetic field strength of the magnetic field application device disposed outside the main chamber of the silicon single crystal production apparatus, and lowering the position of the magnetic field application device, or a combination of two or more of them. A method for producing a silicon single crystal, characterized by the above. The method of claim 2,
When the Ge / Gc is adjusted by controlling the gap between the heat shield and the liquid surface of the raw material melt, the heat shield and the raw material under the condition that the entire crystal surface becomes the N-region when the nitrogen is not doped. When the liquid level of the melt is set to D, the interval between the heat shield and the liquid level of the raw material melt in the case of doping nitrogen is D '/ D = 0.94-nitrogen concentration / (2.41 × ^{10 15} depending on the nitrogen concentration. A method for producing a silicon single crystal, characterized by changing so as to be D 'obtained from. The method of claim 3,
When the calculated D 'is larger than 20 mm, the Ge / Gc is adjusted by setting the distance between the heat shield and the liquid level of the raw material melt to the calculated D', and when the calculated D 'becomes 20 mm or less, the 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 disposed to surround the quartz crucible is lowered with respect to the liquid level of the raw material melt. The silicon single crystal is characterized in that the Ge / Gc is adjusted by any one or a combination of two or more of weakening the magnetic field strength of the magnetic field application device disposed on the outside and lowering the position of the magnetic field application device. Manufacturing method. A silicon epitaxial wafer having an epitaxial layer on a silicon single crystal substrate having an N-region crystal surface,
Nitrogen is doped to the said silicon single crystal board in the density | concentration of 2 * 10 <^13> atoms / cm <^3> or more and 3.2 * 10 <^14> atoms / cm <^3> ,
The entire substrate average in the above number of defects greater than the size is 28nm 10cm silicon single crystal block 2 / a sheet or less, the average size of 45nm or more BMD is detected after a heat treatment at 800 ℃, 3hr + 1000 ℃, 2hr 1 × 10 8 An epitaxial silicon wafer, characterized by a density of at least / cm ³ . The whole crystal surface having the mirror polished surface is an N-region silicon single crystal substrate,
Nitrogen is doped at a concentration of 2 × 10 ¹³ atoms / cm ³ or more and 3.2 × 10 ¹⁴ atoms / cm ³ or less,
The yield of TDDB characteristic is 90% or more, the number of defects of size 45nm or more is 2 / sheet or less as the total substrate average in 10cm or more silicon single crystal block, and it is detected after heat treatment at 800 ℃, 3hr + 1000 ℃, 2hr A silicon single crystal substrate, wherein a BMD having an average size of 45 nm or more is 1 × 10 ⁸ / cm ³ or more.

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