JP2019206451A - Manufacturing method of silicon single crystal and epitaxial silicon wafer and silicon single crystal substrate - Google Patents

Abstract

To provide a manufacturing method of a silicon single crystal capable of sufficiently forming BMD in an advanced low temperature/short time device process and manufacturing a wafer having a high gettering capacity at a high yield in a low/no defect silicon single crystal substrate and an epitaxial silicon wafer of which precipitation is accelerated by nitrogen doping.SOLUTION: A manufacturing method of a silicon single crystal grows the silicon single crystal by Chokralsky method under a condition where a whole area of a crystal becomes N-region. Nitrogen is doped at a concentration of 2×10atoms/cmor more and 3.2×10atoms/cmor less. A ratio Ge/Gc is made to be Ge/Gc>1 where Gc is a temperature gradient at a crystal center part in a lifting axis direction of the silicon single crystal, and Ge is a temperature gradient at a crystal peripheral part. Ge/Gc is gradually increased according to an increase in nitrogen concentration due to segregation in lifting the silicon single crystal.SELECTED DRAWING: Figure 1

Description

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

  2. Description of the Related Art In recent years, semiconductor devices (Logic, NAND, DRAM, etc.) that are becoming finer have two major problems.

  One is that a very small defect in the vicinity of the wafer surface can cause a device failure, so that a high-quality wafer having few or no defects in the vicinity of the surface serving as a device operation region must be manufactured.

  The other is due to the fact that the process is becoming colder and shorter in time, and BMD (Bulk Micro Defect), which is a gettering site for impurity metals, which can be sufficiently formed during the device process has been formed. It is difficult to reduce the device yield.

  V-rich regions having COPs (Crystal Originated Particles) due to vacancies and R-OSF regions in which oxidation-induced stacking faults occur in a ring shape during thermal oxidation can satisfy the requirement for defects near the wafer surface. A low / defect-free silicon single crystal substrate manufactured in an N (Neutral) region containing neither dislocation loops or dislocation clusters due to interstitial silicon, or an epitaxial silicon wafer that forms a defect-free layer on the substrate There is an annealed wafer.

  Among these, the annealed wafer has a problem that the post-processing time required for forming the defect-free layer is long, and is unsuitable for mass supply and tends to be expensive.

  An epitaxial silicon wafer can be formed with a defect-free layer by a relatively short post-treatment, but requires an additional cost as compared with a low / defect-free crystal silicon single crystal substrate.

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

  Nitrogen doping is known to be effective in increasing BMD serving as impurity metal gettering sites. However, in a nitrogen-doped V-rich crystal, the BMD density is reduced due to the R-OSF region at the outer periphery of the wafer, EP defects are caused, and the plate-like or rod-like COP is doped when doped with a high nitrogen atom concentration. EP defect 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. However, it takes grinding loss, grinding cost and time. As another method, there is a method using an N-region crystal that does not contain R-OSF. However, it is difficult to obtain a crystal that does not contain R-OSF by doping nitrogen and has a good yield.

  Next, the influence of the low temperature and short time process accompanying the latter miniaturization will be described.

  For the operation (source / drain current) of the MOSFET, a necessary amount of capacitance of the gate insulating film (= insulating film relative dielectric constant × gate area / insulating film thickness) must be ensured. Therefore, the thinning of the gate insulating film compensates for the reduction in the gate area due to the miniaturization of the semiconductor device and the reduction in the gate area.

  Therefore, in recent semiconductor devices, the gate insulating film has an extremely thin EOT (equivalent oxide 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 reducing the temperature and time of various heat treatments in the device process.

  However, as a negative effect of the low temperature and short time of the device process, conventionally, the BMD serving as an impurity metal gettering site has been sufficiently formed in the substrate during the device process. In a time-consuming device process, the formation of BMD is small, and the gettering ability with respect to the impurity metal is reduced, which may cause a reduction in device yield.

  Because of these problems, it is necessary to have a wafer that is easier to form BMD in the low-temperature and short-time device process at the leading edge and that can obtain high gettering capability even in the low-temperature and 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, nucleation of vacancies is suppressed by nitrogen doping, and the formation of precipitation nuclei due to residual excess vacancies is performed. It is known that methods of increasing the number of thermally stable (large sized) precipitation nuclei by promotion prior to device processing are effective.

  However, in the epitaxial silicon wafer using the nitrogen-doped V-rich crystal described above as the substrate, the BMD density decreased due to the R-OSF region, the EP defect, and the nitrogen doping was performed at a high concentration at the outer periphery of the wafer. In some cases, the EP defect due to the plate-like or rod-like COP is a problem.

JP 2001-139396 A JP 2000-53497 A JP 11-79889 A JP 2000-178099 A WO2002 / 000969 JP 2000-16897 A JP 2000-159595 A JP 2008-66357 A JP 2007-70132 A JP 2016-13957 A

  The present invention has been made in view of the above problems, and 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 same in a low-temperature-free crystal silicon single crystal substrate. An object of the present invention is to provide a method for producing a silicon single crystal that can form a sufficient BMD even in a short-time device process and can produce a wafer having a high gettering capability with a high yield.

In order to solve the above-mentioned problems, the present invention is a method for growing a silicon single crystal by pulling up under the condition that the entire surface of the crystal becomes an N-region by the Czochralski method. At this time, nitrogen is 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 crystal at the center of the crystal in the pulling axis direction of the silicon single crystal The ratio of the temperature gradient Ge in the peripheral part (crystal outer peripheral part) is set to be Ge / Gc> 1, and the Ge / Gc is gradually increased according to the increase in nitrogen concentration due to segregation when the silicon single crystal is pulled. There is provided a method for producing a silicon single crystal characterized by being made large.

  With such a method for producing a silicon single crystal, high-concentration precipitation nuclei are increased by doping nitrogen at a high concentration, and high BMD formation can be achieved even in a low-temperature and short-time device process. Silicon that avoids the R-OSF region even in the nitrogen concentration range with a wide crystal length by correcting and adjusting the defect distribution change caused by nitrogen concentration increase due to segregation during crystal growth while achieving the capability (gettering capability) Single crystals can be produced.

  At this time, the Ge / Gc is adjusted so as to surround the quartz crucible by controlling the distance between the heat shield disposed immediately above the raw material melt in the quartz crucible and the liquid surface of the raw material melt. Lowering the position of the heater made with respect to the liquid surface of the raw material melt, weakening the magnetic field strength of the magnetic field application device disposed outside the main chamber of the silicon single crystal manufacturing device, and It is preferable that the position of the magnetic field application device be lowered by any one or a combination of two or more.

  With such a Ge / Gc adjustment method, the manufacturing apparatus is not significantly changed, and Ge / Gc can be easily adjusted.

At this time, when the Ge / Gc is adjusted by controlling the distance between the thermal shield and the liquid surface of the raw material melt, the entire crystal surface becomes an N-region when nitrogen is not doped. When the distance between the thermal shield and the liquid surface of the raw material melt in the conditions is D, the distance D ′ between the thermal shield and the liquid surface of the raw material melt when nitrogen is doped is defined as nitrogen. According to the concentration, it is preferable to change it so that D ′ is obtained from D ′ / D = 0.94−nitrogen concentration / (2.41 × 10 ¹⁵ ).

  With such a Ge / Gc adjustment method, Ge / Gc adjustment is performed by adjusting the distance between the heat shield and the liquid surface of the raw material melt according to the nitrogen concentration easily and accurately. 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 obtained D ′ as the distance between the thermal shield and the liquid surface of the raw material melt. When the obtained D ′ is 20 mm or less, the distance between the thermal shield and the liquid surface of the raw material melt is set to 20 mm, and the position of the heater disposed so as to surround the quartz crucible is Lowering the liquid surface of the raw material melt, weakening the magnetic field strength of the magnetic field application device disposed outside the main chamber of the silicon single crystal manufacturing device, and the position of the magnetic field application device Preferably, the Ge / Gc is adjusted by any one or a combination of two or more.

  With such a silicon single crystal manufacturing method, the distance between the heat shield and the liquid surface of the raw material melt does not become too narrow. Crystals can be produced.

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

  In such an epitaxial silicon wafer, there is no reduction in BMD density due to the R-OSF region, EP defect, and EP defect due to plate-like or rod-like COP when nitrogen is doped at a high concentration. It becomes.

Further, according to the present invention, the entire surface of the crystal having a mirror-polished surface is an N-region silicon single crystal substrate, and nitrogen 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 yield rate of TDDB characteristics is 90% or more, and the number of defects having a size of 45 nm or more is 10 cm or more, and the average of all substrates in the silicon single crystal block is 2 pieces / piece or less. Provided is a silicon single crystal substrate characterized in that 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 BMD density is not reduced due to the R-OSF region, and the TDDB characteristics are good.

In the method for producing a silicon single crystal of the present invention, high-concentration precipitation nuclei are increased by doping nitrogen at a high concentration, so that high BMD formation is achieved even in a low-temperature and short-time device process. Silicon that avoids the R-OSF region even in the nitrogen concentration range with a wide crystal length by correcting and adjusting the defect distribution change caused by nitrogen concentration increase due to segregation during crystal growth while achieving the capability (gettering capability) Single crystals can be produced.
Further, the epitaxial silicon wafer of the present invention has no BMD density reduction, EP defect caused by the R-OSF region, and EP defect caused by plate-like or rod-like COP caused by nitrogen doping at a high concentration. It becomes. In addition, if the silicon single crystal substrate of the present invention is used, the BMD density due to the R-OSF region is not lowered and the TDDB characteristics are good.

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. 3 is a defect distribution diagram in the pulling axis direction of a silicon single crystal when the silicon single crystal is manufactured under the pulling conditions of Comparative Example 1, Comparative Example 2 and Example 1 with the radial position of the silicon single crystal as a horizontal axis. is there. 10 is a graph showing the results of defect evaluation of an epitaxial wafer in Comparative Example 3. It is a graph which shows the result of the defect evaluation of the epitaxial wafer in the comparative example 4. 6 is a graph showing the results of defect evaluation of an epitaxial wafer in Example 2. 10 is a graph showing the results of TDDB characteristic evaluation of a silicon single crystal substrate in Comparative Example 5. 10 is a graph showing the results of TDDB characteristic evaluation of a silicon single crystal substrate in Comparative Example 6. 10 is a graph showing the results of TDDB characteristic evaluation of a silicon single crystal substrate in Example 3.

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

  As described above, in the epitaxial silicon wafer using the nitrogen-doped V-rich crystal as the substrate, the BMD density is lowered due to the R-OSF region at the outer periphery of the wafer, the EP defect is formed, and nitrogen doping is performed at a high concentration. In some cases, EP defect caused by the plate-like or rod-like COP becomes a problem.

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

  However, based on this idea, while the present inventors are diligently researching, when nitrogen doping is performed and a low / defect-free crystal is produced by the Czochralski method in the N-region, the total length in the crystal growth axis direction In this case, it was difficult to avoid the R-OSF region, and the yield in one crystal was extremely low.

  Specifically, in the production of a low / defect-free crystal in an N-region that is not doped with nitrogen, a growth method that avoids the R-OSF region and collects the N-region at a high yield along the entire length in the crystal growth axis Even when (Patent Documents 3 to 7) are used, when nitrogen is doped, the low / N in the N-region where R-OSF is avoided only in a part of the total length in the crystal growth axis direction where the nitrogen concentration is low. A defect-free crystal could not be produced.

Further, as shown in Patent Document 8 relating to the production of a low / defect-free crystal in an N-region doped with nitrogen, 3 × 10 ^{13 which} can provide a wafer with excellent TDDB characteristics and small variation in BMD density. A nitrogen concentration of atoms / cm ³ or less is insufficient to increase thermally stable (large size) precipitation nuclei before the device process, and a high BMD density (getter) in the low-temperature and short-time device process at the tip. It did not meet the demand for (ring ability).

Further, if the nitrogen concentration is set to a high nitrogen concentration of 3 × 10 ¹³ atoms / cm ³ or more sufficient to increase thermally stable (large size) precipitation nuclei before the device process, it is described in Patent Document 2. As shown in Patent Document 9, 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, Even if the pulling rate is adjusted according to the change in nitrogen concentration due to segregation, the R-OSF region is likely to be generated at the outer peripheral portion of the wafer. To avoid this, if the crystal growth rate is lowered, the BMD in the central portion of the wafer is reduced. As the number decreases, the in-plane BMD density (gettering ability) becomes non-uniform, and in some cases, it becomes an I-rich region having dislocation loops and dislocation clusters in the center of the wafer. A problem occurred.

  Faced with these problems, the present inventor has further intensively studied. As a result, in the production of low / defect-free crystals in the N-region doped with nitrogen, the crystal peripheral portion (crystal outer peripheral portion depends on the nitrogen concentration). ) Found that the defect area changed.

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

  The change 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 periphery of the crystal, the influence of outward diffusion of point defects such as interstitial silicon and vacancies increases, and the outward diffusion of vacancies has the effect of reducing the residual vacancy concentration in the periphery of the crystal. However, when nitrogen is doped at a high concentration, the outward diffusion of vacancies is suppressed by forming a pair of nitrogen and vacancies (NV pairs).

  Therefore, in the case where nitrogen is doped as compared with the case where nitrogen is not doped, the residual vacancy concentration in the crystal peripheral portion increases as the nitrogen concentration increases, and the defect region in the crystal peripheral portion becomes the R-OSF region side. It will shift to.

In order to avoid the R-OSF region, which is likely to occur in the outer peripheral portion of the wafer when the present inventors manufacture a low / defect-free crystal in the N-region by doping nitrogen. When the growth rate is lowered, the BMD at the center of the wafer is reduced and the in-plane BMD density (gettering ability) becomes non-uniform, and in some cases, I-having dislocation loops and dislocation clusters at the center of the wafer. This is the cause of the problem that has become the rich region. When the nitrogen concentration is approximately 2 × 10 ¹³ atoms / cm ³ , the effect of suppressing the outward diffusion of vacancies is observed, 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 thus been completed by the present inventors' extensive research, and is a low / defect-free silicon single crystal substrate manufactured in a nitrogen-doped N-region and an epitaxial using the same as the substrate. In the silicon wafer, crystal growth of the silicon single crystal considering the influence of nitrogen segregation is performed, and using this grown silicon single crystal, a silicon single crystal substrate and an epitaxial silicon wafer using the substrate are produced. The problem caused by the R-OSF region can be completely solved, and the increase of thermally stable (large size) precipitation nuclei by nitrogen doping and the low / defect-free requirement of the wafer surface layer device operating region can be achieved. The headline, the present invention has been reached.

  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 up under the condition that the entire crystal surface becomes an N-region by the Czochralski method. When growing the silicon single crystal, 2 × 10 ¹³ nitrogen is used. Doping is performed at a nitrogen concentration of atoms / cm ³ or more and 3.2 × 10 ¹⁴ atoms / cm ³ or less, and the ratio of the temperature gradient Gc at the center of the crystal in the pulling axis direction of the silicon single crystal to the temperature gradient Ge at the periphery of the crystal is expressed as Ge. / Gc> 1, and the method for producing a silicon single crystal is characterized in that 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 approximately 1/3 or less of the diameter from the outer peripheral edge of the silicon single crystal.

  With such a method for producing a silicon single crystal, high-concentration precipitation nuclei are increased by doping nitrogen at a high concentration, and high BMD formation can be achieved even in a low-temperature and short-time device process. Silicon that avoids the R-OSF region even in the nitrogen concentration range with a wide crystal length by correcting and adjusting the defect distribution change caused by nitrogen concentration increase due to segregation during crystal growth while achieving the capability (gettering capability) Single crystals can be produced.

  Further, by using the silicon single crystal manufactured by the method for manufacturing a silicon single crystal of the present invention, the silicon single crystal substrate and the epitaxial silicon wafer using the silicon single crystal substrate are doped with a high nitrogen concentration, resulting in the R-OSF region. Therefore, a wafer having a high BMD formation capability (gettering capability) can be obtained with a high yield even in a low-temperature and short-time device process.

Under the condition that the temperature distribution during crystal growth is adjusted so that the N-region can be obtained over the entire length of the crystal and the entire surface when not doped with nitrogen, the nitrogen doping amount is set to a nitrogen concentration smaller than 2 × 10 ¹³ atoms / cm ^3. In this case, the influence on the defect distribution is negligible, and the TDDB characteristics in a state where the silicon single crystal substrate is used and the generation of EP defects in the epitaxial silicon wafer using the silicon single crystal substrate are hardly a problem.

However, when the nitrogen concentration is 3 × 10 ¹³ atoms / cm ³ , the defect distribution is affected, and the TDDB characteristics deteriorate when the silicon single crystal substrate is used, or an epitaxial silicon wafer using the silicon single crystal substrate. In this case, an EP defect occurs. Further, as shown in Patent Document 9, even if the pulling rate is adjusted according to the nitrogen concentration (the pulling rate is adjusted slowly according to the increase in the nitrogen concentration), this nitrogen concentration is used for the advanced device process. A sufficient BMD density cannot be obtained by low-temperature and 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 and short-time heat treatment as used in the advanced device process. The change becomes large, and further deterioration of the TDDB characteristic in the state of the silicon single crystal substrate and generation of EP defects in the epitaxial silicon wafer become serious. In this nitrogen concentration range, it cannot be sufficiently improved by slowing the pulling rate with respect to the increase in nitrogen concentration in Patent Document 9, and the TDDB characteristics and epitaxial properties in the case of a silicon single crystal wafer in the outer periphery of the crystal. If the pulling speed is slowed down until EP defect generation on the silicon wafer can be improved, the BMD at the center of the wafer decreases, resulting in in-plane BMD density (gettering ability) non-uniformity, and in some cases the center of the wafer Thus, an I-rich region having a dislocation loop or a dislocation cluster is formed, and an EP defect occurs in the central portion.

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

With the silicon single crystal manufacturing method of the present invention, a nitrogen concentration of 3.2 × 10 ¹⁴ atoms / cm ³ is optimal for obtaining a sufficient BMD density by low-temperature and 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 no EP defects are generated in the state of using the silicon single crystal substrate as an epitaxial silicon wafer. Can do.

  In the present invention, for example, a silicon single crystal manufacturing apparatus 14 as shown in FIG. 1 can grow a silicon single crystal by pulling it up under the condition that the entire surface of the crystal becomes an N-region by the Czochralski method. A silicon single crystal manufacturing apparatus that can be used is used. 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 to this.

  The external appearance of the silicon single crystal manufacturing apparatus 14 shown in FIG. 1 includes 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 raw material silicon polycrystal accommodated in the quartz crucible 5 is melted by the heater 7 to form a raw material melt 4. Further, a heat insulating member 8 is provided to prevent the radiant heat from the heater 7 from affecting the main chamber 1 and the like.

  On the melt surface of the raw material melt 4, the heat shield 12 is disposed opposite to 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 the crucible, the rod-shaped single crystal rod 3 is pulled up from the raw material melt 4. The crucible can be moved up and down in the direction of the crystal growth axis, and the raw material melt 4 is raised by raising the crucible during the growth so as to compensate for the lowering of the liquid surface of the raw material melt 4 that has decreased as the growth of the single crystal proceeds. The height of the melt surface is kept approximately constant.

  Further, an inert gas such as argon gas is introduced from the gas inlet 10 as a purge gas during single crystal growth, and after passing between the single crystal rod 3 being pulled up and the gas rectifying cylinder 11, It passes between the melt surface of the raw material melt 4 and is discharged from the gas outlet 9. By controlling the flow rate of gas to be introduced and the amount of gas discharged by a 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 the temperature gradient Gc at the center of the crystal in the pulling axis direction of the silicon single crystal and the temperature gradient Ge at the periphery of the crystal are such that Ge / Gc> 1, and Ge / Gc is pulled up by the silicon single crystal. It will be logically explained whether it should be gradually increased as the nitrogen concentration increases due to segregation.

  As the nitrogen concentration increases due to segregation, the formation of NV pairs increases, the outward diffusion of vacancies to the outer surface of the crystal decreases, and the residual vacancy concentration around the crystal increases. Shifts to a defect dominant defect area.

  If 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 the residual vacancy concentration between the crystal center and r / 2 (where r is the radius of the silicon single crystal). Due to the fact that it is higher, the BMD distribution becomes non-uniform, and the defect region at the outer peripheral portion shifts from the N-region to the R-OSF region.

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

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

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

  In contrast to V / G where the vacancy concentration and the interstitial silicon (interstitial-Si) concentration antagonize, if V / G is large, the vacancy concentration at the solid-liquid interface increases, and if V / G is small, the interstitial-Si concentration at the solid-liquid interface is To increase.

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

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

  The Ge / Gc is adjusted by controlling the distance between the heat shield 12 disposed immediately above the raw material melt in the quartz crucible 5 and the liquid surface of the raw material melt, and surrounding the quartz crucible 5. Lowering the position of the heater 7 with respect to the liquid surface of the raw material melt, 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, and It is preferable that the position of the magnetic field application device 13 is lowered by any one or a combination of two or more. With such a Ge / Gc adjustment method, the manufacturing apparatus is not significantly changed, and Ge / Gc can be easily adjusted.

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

  There are two methods for increasing Ge / Gc: a method for increasing Ge and a method for decreasing Gc.

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

  Although Ge is slightly changed by heat conduction of the gas in the furnace and convective heat transfer due to the gas flow, in a silicon single crystal manufacturing environment by the CZ method mainly having a high temperature environment with a melting point of 1420 ° C. or higher, heat radiation Since the influence becomes dominant, control by thermal radiation is important.

  The method of reducing Gc reduces the height of the solid-liquid interface (melting point isotherm) and relaxes the temperature gradient with the upper part of the solid-liquid interface, and weakens the suppression of melt convection at the lower part of the crystal growth interface by a magnetic field. This makes it easy 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 reduced due to heat balance as compared to the case where it is not. At this time, since the melting point isotherm of the outermost peripheral part of the crystal is always connected to the surface of the raw material melt 4, Gc is selectively reduced.

  As a method of weakening suppression of melt convection below the crystal growth interface by a magnetic field, there is a method of weakening the magnetic field strength when the magnetic field position remains the same. 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 reducing the height of the solid-liquid interface, the solid-liquid interface can also be lowered by weakening the crystal rotation. However, since the in-plane dopant concentration and oxygen concentration are not uniform, the magnetic field at the solid-liquid interface part is reduced. A method of reducing the strength is preferred.

Further, when Ge / Gc is adjusted by controlling the distance between the thermal shield 12 and the liquid surface of the raw material melt 4, the heat under the condition that the entire crystal surface becomes an N− region when nitrogen is not doped. When the distance between the shield 12 and the liquid surface of the raw material melt 4 is D, the distance between the heat shield 12 and the liquid surface of the raw material melt 4 when doping nitrogen is determined according to the nitrogen concentration. It is preferable to change so that it may become D 'calculated | required from D' / D = 0.94-nitrogen concentration / (2.41 * ¹⁰ < ¹⁵ >).

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

  It is described how this D 'relational expression was derived.

First, as the distance D between the heat shield 12 and the melt directly above the raw material melt 4 that can obtain the N-region on the entire surface, when nitrogen is not doped, 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 In the case of doping with a nitrogen concentration of 2 × 10 ¹⁴ atoms / cm ³ , the conditions other than nitrogen were the same, and the pulling rate was gradually decreased during the growth of the straight body, so that there was a defect in the silicon single crystal block. A region V-rich, R-OSF region, Nv region, Ni region, and I-rich region were included, and a sample parallel to the crystal growth axis direction was cut out from the obtained silicon single crystal block and 800 ° C. in a wet oxidizing atmosphere. Heat treatment at 4 hr + 1000 ° C for 16 hr Applied, it was to investigate the changes in the defect distribution by each of the nitrogen concentration in the X-ray topography (XRT).

  Second, at each nitrogen concentration, the distance between the heat shield 12 immediately above the raw material melt 4 and the liquid surface of the raw material melt 4 is changed, and an N-region distribution equivalent to that obtained when nitrogen is not doped is obtained. The distance D ′ between the heat shield 12 immediately above the raw material melt 4 and the liquid surface of the raw material melt 4 was determined.

Third, a relational expression of a change in the ratio of the distance D ′ between the heat shield 12 and the liquid surface of the raw material melt 4 to the nitrogen concentration and the ratio of the distance D is obtained by the least square 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 thermal shield 12 and the liquid surface of the raw material melt 4 to obtain 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 crucible 5 is the liquid of the raw material melt 4. Lowering the surface, weakening the magnetic field strength of the magnetic field application device 13 disposed outside the main chamber 1 of the silicon single crystal production device 14, and lowering the position of the magnetic field application device 13. Preferably, the Ge / Gc is adjusted by any one of them or a combination of two or more thereof.

  With 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. Thus, the silicon single crystal can be manufactured without hindering the pulling of the silicon single crystal.

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 whose entire crystal surface is an N− region, and nitrogen is 2 × 10 ¹³ atoms / cm on the silicon single crystal substrate. ^{3 to} 3.2 × 10 ¹⁴ atoms / cm ³ doped with a nitrogen concentration of ³ or less, and the number of defects having a size of 28 nm or more is 10 cm or more. There is provided an epitaxial silicon wafer characterized in that 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 an epitaxial silicon wafer, there is no decrease in BMD density due to the R-OSF region, EP defect, and EP defect due to plate-like or rod-like 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 in-plane BMD quality becomes an epitaxial silicon wafer.

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 having an N− region, and nitrogen 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 yield 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, and the average number of all substrates in the silicon single crystal block is 2 pieces / piece or less. Provided is a silicon single crystal substrate characterized in that 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. In addition, 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 with uniform in-plane BMD quality is obtained.

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

(Comparative Example 1)
Without doping nitrogen, 410 kg of 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 4000 G magnetic field. At this time, an N (Neutral) region can be obtained over the entire length of the crystal by previously adjusting the distance (50 mm) between the heat shield immediately above the raw material melt and the raw material melt, the heater position, and the position of the magnetic field application device. Thus, the temperature distribution during crystal growth was adjusted. Under this condition, the pulling rate is gradually decreased during the growth of the cylinder, and the defect region V-rich, R-OSF region, Nv region, Ni region, I-rich region (from V-rich region) is formed 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 and subjected to a heat treatment at 800 ° C. for 4 hours + 1000 ° C. for 16 hours to obtain an XRT (X-ray topograph). Method) was used to evaluate the defect distribution.

(Comparative Example 2)
In the same manner as in Comparative Example 1, the distance between the heat shield immediately above the raw material melt and the raw material melt (50 mm), the heater position, the magnetic field position, and the magnetic field strength are doped with nitrogen, and the pulling rate is gradually increased during the growth of the straight body. The silicon single crystal block having defect distribution evaluation including each region from V-rich to I-rich in the silicon single crystal block was manufactured. Nitrogen concentration is 2 × 10 ¹³ atoms / cm ³ level (nitrogen concentration in silicon single crystal block 2 × 10 ¹³ −2.2 × 10 ¹³ atoms / cm ³ ), 3 × 10 ¹³ atoms / cm ³ level (silicon single crystal Nitrogen concentration in crystal block 3 × 10 ¹³ −3.2 × 10 ¹³ atoms / cm ³ ), 6 × 10 ¹³ atoms / cm ³ level (nitrogen concentration in silicon single crystal block 6 × 10 ¹³ −6.2 × 10 ¹³ atoms / cm ³ ), 3 × 10 ¹⁴ atoms / cm ³ level (nitrogen concentration in silicon single crystal block 3 × 10 ¹⁴ −3.2 × 10 ¹⁴ atoms / cm ³ ), each silicon single crystal block is manufactured. 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 immediately above the raw material melt and the liquid surface of the raw material melt was D ′ / D = 0.94−nitrogen concentration / 2.41 × 10 ¹⁵ It carried out like. By changing the distance between the heat shield just above the raw material melt and the liquid surface of the raw material melt in this way, the temperature gradient Gc at the center of the crystal in the pulling axis direction of the silicon single crystal and the temperature gradient Ge at the periphery of the crystal Ge / Gc> 1, and Ge / Gc was gradually increased as the nitrogen concentration increased due to segregation during pulling of the silicon single crystal. Here, D is 50 mm. The distance between the heat shield just above the raw material melt and the liquid surface of the raw material melt is 2 × 10 ¹³ atoms / cm ³ level (nitrogen concentration in silicon single crystal block: 2-2.2 × 10 ¹³ atoms / cm ³ ). At D ′ = 46.6 mm (D ′ / D = 0.932), 3 × 10 ¹³ atoms / cm ³ level (nitrogen concentration in silicon single crystal block: 3-3.2 × 10 ¹³ atoms / cm ³ ), D ′ = 46.3 mm (D ′ / D = 0.926), D ′ = 45 at 6 × 10 ¹³ atoms / cm ³ level (silicon single crystal block nitrogen concentration 6-6.2 × 10 ¹³ atoms / cm ³ ) 8 mm (D ′ / D = 0.916), 3 × 10 ¹⁴ atoms / cm ³ level (silicon single crystal block nitrogen concentration: 3-3.2 × 10 ¹⁴ atoms / cm ³ ), D ′ = 40.8 mm (D ′ / D = 0.8 16) A silicon single crystal block was manufactured, and the defect distribution when the distance between the heat shield directly above the raw material melt and the liquid surface of the raw material melt was adjusted at each nitrogen concentration was evaluated. The change between the heat shield just above the raw material melt and the liquid surface of the raw material melt was changed by changing the height position of the crucible.

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

Compared with Comparative Example 1, the defect distribution of Comparative Example 2 doped with nitrogen is as follows: nitrogen doping amount 2 × 10 ¹³ atoms / cm ³ level, 3 × 10 ¹³ atoms / cm ³ level, 6 × 10 ¹³ atoms / cm ³ At each of the 3 × 10 ¹⁴ atoms / cm ³ levels, the out-diffusion of vacancies during crystal growth decreases due to the formation of nitrogen / vacancy pairs (NV pairs) as the nitrogen concentration increases, 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 changes to a distribution that is sagging at the outer peripheral portion.

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

  On the other hand, in Example 1 of the present invention, the defect distribution change with increasing nitrogen concentration (the defect region on the crystal outer periphery side shifts to the vacancy dominant side, and the R-OSF region changes to a distribution that sags on the outer periphery) When the wafer is fabricated, the entire surface of the wafer can be made into a uniform defect region. Therefore, 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., 2 hr. Can be controlled uniformly. In addition, the device yield is reduced in that the TDDB characteristic deterioration in the silicon single crystal substrate state due to the mixture of the R-OSF regions and the EP defect when the manufactured silicon single crystal substrate is used for the epitaxial silicon wafer substrate can be suppressed. Yield is good.

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

[Change in non-defective rate of epitaxial silicon wafers (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 with reference to the non-defective product ratio of the epitaxial wafer.

(Comparative Example 3)
410 kg of 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. Heater position and magnetic field application during crystal growth so that an N-region can be obtained over the entire length of the crystal when nitrogen is not doped at an interval of 50 mm between the heat shield immediately above the raw material melt and the liquid surface of the raw material melt. In the condition where the position of the apparatus is adjusted, in the straight body product collecting part, nitrogen non-dope (Comparative Example 3-1), nitrogen concentration of 2 × 10 ¹³ -6 × 10 ¹³ atoms / cm ³ (Comparative Example 3-2), Three crystals were manufactured so as to have a nitrogen concentration of 1 × 10 ¹⁴ −3.2 × 10 ¹⁴ atoms / cm ³ (Comparative Example 3-3), and a silicon single crystal substrate was manufactured from the obtained crystals. An epitaxial silicon wafer was manufactured using it as a substrate for an epitaxial silicon wafer. In order to evaluate defects of the epitaxial silicon wafer, SP3 manufactured by KLA Tencor was used to evaluate defects detected at 28 nm or more in the Oblique mode. Moreover, the produced epitaxial wafer was subjected to a heat treatment at 800 ° C., 3 hr + 1000 ° C., and 2 hr, and then a BMD density of 30 nm or more was measured by an infrared scattering method.

(Comparative Example 4)
Adjust the pulling speed according to the nitrogen concentration as shown in Patent Document 9 with the distance between the heat shield just above the raw material melt and the liquid surface of the raw material melt being 50 mm (increase with increasing nitrogen concentration) The epitaxial silicon wafer is the same as Comparative Example 3-2 (Comparative Example 4-2) and Comparative Example 3-3 (Comparative Example 4-2) except that the speed is adjusted to be slower). Were manufactured and evaluated for defects. Moreover, the produced epitaxial wafer was subjected to a heat treatment at 800 ° C., 3 hr + 1000 ° C., and 2 hr, and then a BMD density of 30 nm or more was measured by an infrared scattering method.

(Example 2)
The distance D ′ between the heat shield immediately 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 ). Example 2-1 is a nitrogen concentration of 2 × 10 ¹³ -6 × 10 ¹³ atoms / cm ³ , and nitrogen in the segregation by nitrogen from the crystal cone side to the tail side to offset the influence of nitrogen segregation during crystal growth. The same as Comparative Example 4-1, except that the distance between the heat shield immediately 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 in accordance with the concentration change. 2-2 is a nitrogen concentration of 1 × 10 ¹⁴ −3.2 × 10 ¹⁴ atoms / cm ³ , and D ′ = 44.9 mm to 40.3 mm. Except for adjusting the distance to the surface, it was the same as Comparative Example 4-2, and an epitaxial wafer was manufactured and evaluated for defects similarly to Comparative Example 3. Moreover, the produced epitaxial wafer was subjected to a heat treatment at 800 ° C., 3 hr + 1000 ° C., and 2 hr, and then a BMD density of 30 nm or more was measured by an infrared scattering method. By changing the distance between the heat shield just above the raw material melt and the liquid surface of the raw material melt in this way, the temperature gradient Gc at the center of the crystal in the pulling axis direction of the silicon single crystal and the temperature gradient Ge at the periphery of the crystal Ge / Gc> 1, and Ge / Gc was gradually increased as the nitrogen concentration increased due to segregation during pulling of the silicon single crystal.

  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 costs, even if there are several defects per wafer, defective chips caused by such defects become a major problem.

In Comparative Example 3, EP defect generation hardly becomes a problem up to a nitrogen concentration of 2 × 10 ¹³ atoms / cm ³ , but a high nitrogen concentration sufficient to increase thermally stable (large size) precipitation nuclei is sufficient. When a nitrogen concentration of 3 × 10 ¹³ atoms / cm ³ is obtained, EP defects are generated. Further, when the nitrogen concentration is higher than 3 × 10 ¹³ atoms / cm ³ , EP defects increase as the nitrogen concentration increases, and the level is unbearable for use in advanced devices with high process costs. In Comparative Examples 3-1, 3-2, and 3-3, the BMD density of the epitaxial silicon wafer after the heat treatment at 800 ° C., 3 hr + 1000 ° C., and 2 hr was 1-3 × 10 ⁷ , 1-2 × 10 respectively. ⁸ and 2.5-15 × 10 ⁸ / cm ³ . The BMD density of an average size of 45 nm or more, which is considered to have sufficient gettering ability in the tip device at a nitrogen concentration of 2 × 10 ¹³ atoms / cm ³ or more, could be 1 × 10 ⁸ or more.

In Comparative Example 4, an improvement effect can be seen by lowering the pulling speed with respect to the increase in nitrogen concentration, but it is more preferable to obtain a sufficient BMD density by low-temperature and short-time heat treatment as used in advanced device processes. EP defects start to increase from a nitrogen concentration of × 10 ¹³ atoms / cm ³ or more, and at nitrogen of 1 × 10 ¹⁴ atoms / cm ³ or more, the level is not suitable for use in advanced devices. Furthermore, when the pulling rate is further lowered, when heat treatment is performed at 800 ° C., 3 hr + 1000 ° C., 2 hr, the BMD at the center of the wafer is reduced and the in-plane BMD density (gettering ability) is nonuniform. In some cases, an I-rich region having a dislocation loop or a dislocation cluster in the center of the wafer has resulted in an EP defect in the center. It was impossible to suppress. In Comparative Examples 4-1 and 4-2, the BMD densities of the epitaxial silicon wafers after the heat treatment at 800 ° C., 3 hr + 1000 ° C., and 2 hr are 1-2 × 10 ⁸ and 2.5-15 × 10 respectively. It was ⁸ / cm ³ . The BMD density of an average size of 45 nm or more, which is considered to have sufficient gettering ability in the tip device at a nitrogen concentration of 2 × 10 ¹³ atoms / cm ³ or more, could be 1 × 10 ⁸ or more.

On the other hand, in Example 2, EP defects can be suppressed to a good level up to a nitrogen concentration of 3.2 × 10 ¹⁴ atoms / cm ³ . As a result, the number of defects at 28 nm or more is an extremely good defect level of 2 pieces / piece or less on average for all substrates 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. Could get. Further, the BMD density of the epitaxial silicon wafer after the heat treatment at 800 ° C., 3 hr + 1000 ° C., 2 hr is 1-2 × 10 ⁸ / cm ³ in Example 2-1, and 2.5-5 × 10 ^{8 in} Example 2-2. / cm ³ and the density of the average size 45nm or more BMD and 1 × ¹⁰ 8 / cm ³ or more appears to have a sufficient gettering capability tip device with nitrogen concentration 2 × ¹⁰ 13 atoms / cm ³ or more I was able to. It should be noted that since the generation of EP defects due to precipitates may occur at a nitrogen concentration of 3.5 × 10 ¹⁴ atoms / cm ³ , the nitrogen concentration is desirably 3.2 × 10 ¹⁴ atoms / cm ³ or less.

  As described above, when the present invention is used, an epitaxial silicon wafer having a good EP defect level is very high in the entire crystal length even under a high nitrogen concentration condition where a high gettering capability can be expected in a low temperature / short time device process at the tip. It becomes possible to manufacture with a yield.

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

(Comparative Example 5)
410 kg of 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 heater position during crystal growth so that an N (Neutral) region can be obtained over the entire length of the crystal when nitrogen is not doped at a distance of 50 mm between the heat shield immediately above the raw material melt and the liquid surface of the raw material melt. Under the condition where the position of the magnetic field application device is adjusted, the nitrogen concentration of nitrogen non-doped (Comparative Example 5-1) and 2 × 10 ¹³ -6 × 10 ¹³ atoms / cm ³ (Comparative Example 5-2) ) Three crystals were manufactured so as to have a nitrogen concentration of 1 × 10 ¹⁴ −3.2 × 10 ¹⁴ atoms / cm ³ (Comparative Example 5-3), and a silicon single crystal substrate was manufactured from the obtained crystals The TDDB characteristics were evaluated. Further, for defect evaluation of the silicon single crystal substrate, SP3 manufactured by KLA Tencor was used to evaluate defects detected at 45 nm or more in the Oblique mode. In addition, the manufactured silicon single crystal substrate was heat-treated at 800 ° C., 3 hr + 1000 ° C., and 2 hr, and then a BMD density of 30 nm or more was measured by an infrared scattering method.

(Comparative Example 6)
Adjusting the pulling speed according to the nitrogen concentration as shown in Patent Document 9 with the distance between the heat shield just above the raw material melt and the liquid surface of the raw material melt adjusted to 50% (as the nitrogen concentration increases) Except that the speed was adjusted to be slower), the same silicon as manufactured in Comparative Example 5 was used as Comparative Example 5-2 (Comparative Example 6-1) and Comparative Example 5-3 (Comparative Example 6-2). The TDDB characteristics and defects of the crystal substrate were evaluated. In addition, the manufactured silicon single crystal substrate was heat-treated at 800 ° C., 3 hr + 1000 ° C., and 2 hr, and then a BMD density of 30 nm or more was measured by an infrared scattering method.

(Example 3)
The distance between the heat shield immediately 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 ). Example 3-1 has a nitrogen concentration of 2 × 10 ¹³ -6 × 10 ¹³ atoms / cm ³ and nitrogen in the segregation due to nitrogen from the crystal cone side to the tail side in order to offset the influence of nitrogen segregation during crystal growth. The same as Comparative Example 6-1 except that the distance between the heat shield immediately above the raw material melt and the liquid surface of the raw material melt was adjusted from D ′ = 46.6 mm to 45.8 mm in accordance with the change in concentration. 3-2 is a nitrogen concentration of 1 × 10 ¹⁴ −3.2 × 10 ¹⁴ atoms / cm ³ , and D ′ = 44.9 mm to 40.3 mm. A silicon single crystal substrate was manufactured in the same manner as in Comparative Example 5 except that the distance from the surface was adjusted, and the TDDB characteristics and defects were evaluated. In addition, the manufactured silicon single crystal substrate was heat-treated at 800 ° C., 3 hr + 1000 ° C., and 2 hr, and then a BMD density of 30 nm or more was measured by an infrared scattering method. By changing the distance between the heat shield just above the raw material melt and the liquid surface of the raw material melt in this way, the temperature gradient Gc at the center of the crystal in the pulling axis direction of the silicon single crystal and the temperature gradient Ge at the periphery of the crystal Ge / Gc> 1, and Ge / Gc was gradually increased as the nitrogen concentration increased due to segregation during pulling of the silicon single crystal.

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

In FIG. 6, 7, and 8, the gray cell is a TDDB defect location. The TDDB defect defect and the EP defect source are related to each other and have the same results 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, the TDDB defects gradually increase as the nitrogen concentration increases at a nitrogen concentration of 3 × 10 ¹³ atoms / cm ³ or more. The non-defective rate of the TDDB characteristic in Comparative Example 5 is 99.7-99.3, 99.3-69.2, and 50 in Comparative Example 5-1, Comparative Example 5-2, and Comparative Example 5-3, respectively. 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 on average for all substrates in a silicon single crystal block of 10 cm or more. 73-1250 pieces / 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., 3 hr + 1000 ° C., and 2 hr were 1-3 × 10 ⁷ , 1-2 ×, respectively. 10 ^8, and was 2.5-15 × ¹⁰ 8 / cm ^3. The BMD density of an average size of 45 nm or more, which is considered to have sufficient gettering ability in the tip device at a nitrogen concentration of 2 × 10 ¹³ atoms / cm ³ or more, could be 1 × 10 ⁸ or more.

In Comparative Example 6, as with the EP defect tendency, although an improvement effect is seen with respect to Comparative Example 5, it cannot be completely improved, and a TDDB defect is observed due to a nitrogen concentration of 6 × 10 ¹³ atoms / cm ³ or more. Increasing and getting worse. The non-defective rate of the TDDB characteristics in Comparative Example 6 was 99.7-87.3 and 69.9-51.7% in Comparative Example 6-1 and Comparative Example 6-2, respectively. Moreover, the defect in 45 nm or more in the comparative example 6-1 and the comparative example 6-2 is 1-57 piece / piece and 160-364 piece / sheet on the average of all the substrates in a silicon single crystal block of 10 cm or more. there were. In Comparative Examples 6-1 and 6-2, the BMD densities of the silicon single crystal substrates after the heat treatment at 800 ° C., 3 hr + 1000 ° C., and 2 hr are 1-2 × 10 ⁸ and 2.5-15 ×, respectively. It was 10 ⁸ / cm ³ . The BMD density of an average size of 45 nm or more, which is considered to have sufficient gettering ability in the tip device at a nitrogen concentration of 2 × 10 ¹³ atoms / cm ³ or more, could be 1 × 10 ⁸ or more.

On the other hand, in Example 3, the TDDB failure can be suppressed to a nitrogen concentration of 3.2 × 10 ¹⁴ atoms / cm ³ . The non-defective product ratio of the TDDB characteristic in Example 3 is 99.7-99.3 in Example 3-1 and Example 3-2, respectively, in the nitrogen concentration range of 2-3.2 × 10 ¹⁴ atoms / cm ^3. %Met. Moreover, the defect in 45 nm or more in Example 3-1 and Example 3-2 is 1-1.9 on the average of all the substrates in a silicon single crystal block of 10 cm or more, and 1.2-2 piece / sheet. Met. Further, the BMD densities of the silicon single crystal substrates after heat treatment at 800 ° C., 3 hr + 1000 ° C., and 2 hr in Example 3-1 and Example 3-2 are 1-2 × 10 ⁸ and 2.5-15 ×, respectively. It was 10 ⁸ / cm ³ . The BMD density of an average size of 45 nm or more, which is considered to have sufficient gettering ability in the tip device at a nitrogen concentration of 2 × 10 ¹³ atoms / cm ³ or more, could be 1 × 10 ⁸ or more.

  Thus, by using the present invention, a silicon single crystal substrate having a good defect level without increasing TDDB defects even under high nitrogen concentration conditions where high gettering capability can be expected in a low temperature / short time device process at the leading edge. Can be produced with a very high yield over the entire crystal length.

As described above, according to the present invention, a nitrogen concentration of 3 × 10 ¹³ atoms / cm ³ to 3.2 × optimal for obtaining a sufficient BMD density by a low-temperature and short-time heat treatment as used in the advanced device process is used. Up to 10 ¹⁴ atoms / cm ³ , it is possible to obtain a wafer that has good TDDB characteristics in a state where a silicon single crystal substrate is formed and that does not generate an EP defect in an epitaxial silicon wafer.

  In addition, this invention is not limited to the said embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

1 ... main chamber, 2 ... pulling chamber, 3 ... single crystal rod,
4 ... Raw material melt, 5 ... Quartz crucible, 6 ... Graphite crucible, 7 ... Heater,
8 ... heat insulating member, 9 ... gas outlet, 10 ... gas inlet, 11 ... gas rectifier,
DESCRIPTION OF SYMBOLS 12 ... Thermal shield, 13 ... Magnetic field application apparatus, 14 ... Manufacturing apparatus of a silicon single crystal.

Claims (6)

A method of growing a silicon single crystal by pulling up under the condition that the entire crystal surface becomes an N-region by the Czochralski method,
When growing the silicon single crystal, nitrogen is 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 pulling axis direction of the silicon single crystal to the temperature gradient Ge at the periphery of the crystal is such that Ge / Gc>1;
A method for producing a silicon single crystal, characterized in that the Ge / Gc is gradually increased in accordance with an increase in nitrogen concentration due to segregation when the silicon single crystal is pulled.   The adjustment of Ge / Gc is performed by controlling the distance between the heat shield disposed immediately above the raw material melt in the quartz crucible and the liquid surface of the raw material melt, and the heater disposed so as to surround the quartz crucible. Is lowered with respect to the liquid surface of the raw material melt, the magnetic field strength of the magnetic field applying device disposed outside the main chamber of the silicon single crystal manufacturing apparatus is reduced, and the magnetic field applying device The method for producing a silicon single crystal according to claim 1, wherein the position is lowered by any one or a combination of two or more. When the Ge / Gc is adjusted by controlling the distance between the thermal shield and the liquid surface of the raw material melt, the heat under the condition that the entire crystal surface becomes an N-region when not doped with nitrogen. When the distance between the shield and the liquid surface of the raw material melt is D, the distance between the heat shield and the liquid surface of the raw material melt when doping nitrogen is determined according to the nitrogen concentration. 3. The method for producing a silicon single crystal according to claim 2, wherein the value is changed so as to be D 'obtained from' /D=0.94-nitrogen concentration / (2.41 × 10 ¹⁵ ).   When the obtained D ′ is larger than 20 mm, the Ge / Gc is adjusted by setting the obtained D ′ as the distance between the thermal shield and the liquid surface of the raw material melt. When 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 heater disposed so as to surround the quartz crucible is positioned at the raw material melt. Lowering the liquid level, reducing the magnetic field strength of the magnetic field application device disposed outside the main chamber of the silicon single crystal manufacturing apparatus, and lowering the position of the magnetic field application 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 thereof. A silicon epitaxial wafer having an epitaxial layer on a silicon single crystal substrate whose entire crystal surface is an N-region,
The silicon single crystal substrate is doped with nitrogen at a nitrogen concentration of 2 × 10 ¹³ atoms / cm ³ or more and 3.2 × 10 ¹⁴ atoms / cm ³ or less,
BMD having an average size of 45 nm or more detected after heat treatment at 800 ° C., 3 hr + 1000 ° C., and 2 hr with an average of 2 or less on all substrates in a silicon single crystal block having a size of 28 nm or more and a size of 10 cm or more. Is an epitaxial silicon wafer characterized by having a density of 1 × 10 ⁸ / cm ³ or more. The entire surface of the crystal having a mirror-polished surface is an N-region silicon single crystal substrate,
Nitrogen is doped with a nitrogen concentration of 2 × 10 ¹³ atoms / cm ³ or more and 3.2 × 10 ¹⁴ atoms / cm ³ or less,
A non-defective product ratio of TDDB characteristics is 90% or more, and the number of defects having a size of 45 nm or more is 10 cm or more, and the average of all substrates in a silicon single crystal block is 2 pieces / piece or less. A silicon single crystal substrate characterized in that BMDs having an average size of 45 nm or more detected after being processed have a density of 1 × 10 ⁸ / cm ³ or more.

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