JP5283543B2 - Method for growing silicon single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method requiring no irradiation of a silicon single crystal with neutrons, relatively broadening the range of pulling speed of a single crystal and reducing fluctuation of the resistivity in a direction of the pulling axis and fluctuation of the in-plane resistivity in a radial direction of a silicon single crystal. <P>SOLUTION: After a silicon single crystal 11 containing an n-type dopant is pulled from a quartz crucible 13, the silicon single crystal 11 having interstitial oxygen concentration of not more than 6.0&times;10<SP>17</SP>atoms/cm<SP>3</SP>, and not more than 5% of fluctuation of the in-plane resistivity in the radial direction, a silicon raw material 52 is supplied to the crucible 13 and melted, and a new silicon single crystal 11 is pulled from the quartz crucible 13. Thus, a plurality of silicon single crystals 11 are grown. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method for growing a silicon single crystal by the Czochralski method for manufacturing a silicon wafer suitable for an insulated gate bipolar transistor, and a method for manufacturing a silicon wafer with reduced defects inside the wafer. .

  In recent years, development of an insulated gate bipolar transistor (hereinafter referred to as IGBT) has been promoted. IGBT is not an element that uses only the vicinity of the wafer surface (only in the radial direction of the wafer) like an LSI such as a memory, but also an element that uses the wafer thickness direction (wafer pull-up axis direction). Is affected by the bulk quality of the wafer. For this reason, it is necessary to reduce not only COP (Crystal Originated Particles) and oxygen precipitates existing in the wafer surface layer but also COP and oxygen precipitates inside the wafer.

Therefore, conventionally, when manufacturing such a silicon wafer for IGBT, a silicon single crystal has been grown by a floating zone method (hereinafter referred to as FZ method). However, the FZ method has a problem that it is difficult to increase the diameter of the wafer. In recent years, a silicon single crystal is pulled up by the Czochralski method (hereinafter referred to as CZ method), and this silicon single crystal is used for IGBT. Attempts have been made to manufacture silicon wafers. For example, Patent Document 1 discloses that a silicon single crystal is grown by a CZ method in a hydrogen gas atmosphere, COPs and dislocation clusters are excluded in the entire radial direction of the silicon single crystal, and the interstitial oxygen concentration in the silicon single crystal is 8. There is disclosed a silicon single crystal wafer for IGBT having a resistivity variation of 5% or less in a plane of a silicon wafer obtained by slicing the silicon single crystal of 5 × 10 ¹⁷ atoms / cm ³ or less. ing. In the silicon single crystal wafer for IGBT configured in this way, COP and dislocation clusters are eliminated in the entire radial direction of the silicon single crystal, so that it is suitable as a wafer for IGBT that is an element that uses the wafer in the vertical direction. is there. That is, since COP and dislocation clusters are eliminated in the entire radial direction of the silicon single crystal, COP is not taken into the gate oxide film when forming the gate oxide film on the wafer surface in the IGBT manufacturing process. (Gate Oxide Integrity: gate oxide film withstand voltage characteristic) is not deteriorated. Further, by eliminating dislocation clusters, leakage current in the integrated circuit can be prevented.

On the other hand, Patent Document 2 discloses a silicon wafer manufacturing method in which a silicon wafer obtained by slicing a silicon single crystal is heat-treated in an oxidizing atmosphere. In this manufacturing method, when the temperature at which the silicon wafer is heat-treated in an oxidizing atmosphere is T ° C. and the interstitial oxygen concentration of the silicon wafer is [Oi] atoms / cm ³ , the temperature T and the interstitial oxygen concentration [Oi] Is subjected to heat treatment so as to satisfy the following formula (A) .

[Oi] ≦ 2.123 × 10 ²¹ exp (−1.035 / k (T + 273)) (A)
In the above formula (A) , the interstitial oxygen concentration [Oi] is a value measured by the FT-IR method (ASTM F-121, 1979), and k is Boltzmann constant 8.617 × 10 ⁻⁵ eV / K. It is. As the silicon single crystal, a single crystal doped with phosphorus by neutron irradiation is used. In the silicon wafer thus manufactured, when the silicon wafer is heat-treated in an oxidizing atmosphere, if the heat-treatment temperature T is set so that the heat-treatment temperature T and the interstitial oxygen concentration [Oi] satisfy the above relationship, Interstitial silicon atoms generated on the surface of the silicon wafer diffuse into the silicon wafer and fill the COP that is a cavity, so that the COP can be extinguished from the shallow position to the deep position in the silicon wafer. Further, when a silicon single crystal is grown by the CZ method, the silicon single crystal is grown without doping a dopant such as phosphorus, and the grown silicon single crystal is irradiated with neutrons, so that the silicon single crystal is doped with phosphorus. Therefore, the specific resistance in the pulling axis direction of the silicon single crystal can be made uniform.

JP 2007-254274 A (Claim 1, paragraph [0015]) Republished patent WO2004 / 073057 (Claims 1 and 2, specification page 3, line 25 to page 4, line 8; specification page 4, line 14 to page 18, line 18)

  However, in the above-mentioned conventional silicon single crystal wafer for IGBT shown in Patent Document 1, the pulling rate allowed for obtaining a region free from glow-in defects is obtained by growing the silicon single crystal in a hydrogen gas atmosphere. In order to obtain a silicon single crystal free from glow-in defects in which the width (defect-free margin) is increased but COP and dislocation clusters are eliminated, the pulling rate is the same as in the conventional growth of a silicon single crystal in an argon gas atmosphere. Has to be slowed down, leading to a decrease in productivity. In addition, when a silicon single crystal is grown under a growth condition in which COP is generated in a hydrogen gas atmosphere, there is a problem that a giant cavity defect called a hydrogen defect is generated in the COP generation region.

  On the other hand, in the method for manufacturing a silicon wafer shown in the above-mentioned conventional patent document 2, when a silicon single crystal is grown by the CZ method, the silicon single crystal is grown without doping phosphorus or the like, By irradiating the silicon single crystal with neutrons, a silicon wafer having a uniform resistivity in the radial direction and the pulling axis direction of the single crystal can be obtained. Although such a neutron irradiation technique is an effective method for achieving a uniform dopant concentration, the neutron irradiation must be performed using a nuclear reactor such as a heavy water reactor, and such treatment can be performed. There are only a few institutions throughout the world. For this reason, when neutron irradiation is adopted, it is expected that a large number of product wafers cannot be manufactured industrially. In addition, a heat treatment is required to recover the irradiation damage introduced into the single crystal by neutron irradiation, which raises the manufacturing cost and that only a single crystal doped with phosphorus can be manufactured by neutron irradiation. There was also a point.

  Further, in the method for manufacturing a silicon wafer disclosed in the above-mentioned conventional patent document 2, the oxygen concentration in the silicon wafer and the subsequent oxidation are so satisfied that the relationship between the specific interstitial oxygen concentration and the specific oxidation heat treatment temperature is satisfied. By adjusting the heat treatment conditions, the COP can be extinguished not only on the surface layer of the wafer but also in the entire area of the wafer. However, when the size of the COP originally present in the single crystal is large or the density of the COP is high. However, there was a problem that COP could not be completely extinguished even by performing an oxidation heat treatment. For this reason, it is necessary to grow the silicon single crystal so that the size of the COP is reduced in the stage of growing the single crystal. Until now, as a technique for reducing the COP size in a single crystal, it is possible to reduce the size of the COP formed in the single crystal by promoting cooling at the stage of growing the single crystal and increasing the pulling rate. It is known that you can. On the other hand, in general, it is required to provide a wafer having a high resistivity as an IGBT wafer. However, when growing a single crystal for making such a wafer, a slight difference in the dopant concentration is caused by a single crystal to be grown. This causes a large change in the resistivity of the crystal. Therefore, if the high cooling rate and high speed pulling are performed in order to reduce the COP size, the solid-liquid interface shape between the single crystal and the melt becomes a shape that protrudes upward, so the radial direction of the single crystal. There is also a problem in that the dopant concentration of the material varies greatly.

Moreover, as a silicon single crystal wafer for IGBT, it is required to provide a silicon wafer in which the oxygen concentration is reduced as much as possible and the in-plane resistance distribution is uniform. As a technique for reducing the oxygen concentration in silicon single crystals, the amount of oxygen taken into the silicon melt from the quartz crucible has been reduced by applying a horizontal magnetic field to the silicon melt to slow the crucible rotation speed. It has been known that the interstitial oxygen concentration in the single crystal can be reduced. However, according to the experiments by the present inventors, the interstitial oxygen concentration is 6.0 × 10 ¹⁷ atoms / cm ³ or less simply by reducing the rotation speed of the crucible applying a horizontal magnetic field to the silicon melt. It has become clear that it is impossible to grow a silicon single crystal having a very low oxygen concentration. In addition, it is known that increasing the rotational speed of a silicon single crystal makes the dopant concentration (resistivity distribution) in the plane of the silicon single crystal uniform, but increasing the rotational speed of the single crystal increases the oxygen concentration. There is a problem. However, if the growth conditions are such that the shape of the solid-liquid interface between the single crystal and the silicon melt is flattened, the dopant concentration distribution in the radial direction of the single crystal does not deteriorate even if the rotation speed of the single crystal is reduced. It was found that the interstitial oxygen concentration can be further reduced.

  The object of the present invention is to irradiate the silicon single crystal with neutrons, and can relatively widen the pulling speed of the single crystal. Further, the resistivity in the pulling axis direction and the radial surface of the silicon single crystal. An object of the present invention is to provide a method for growing a silicon single crystal that can reduce variations in internal resistivity.

A first aspect of the present invention is to store a silicon melt in a quartz crucible housed in a chamber, and immerse the seed crystal in the silicon melt and pull it up while rotating to obtain a silicon single crystal from the seed crystal. In the method of growing a silicon single crystal that is pulled up, a horizontal magnetic field of 0.2 T or more is applied to the silicon melt in the quartz crucible, the rotation speed of the quartz crucible is 1.5 rpm or less, and the growing silicon single crystal The rotation speed is set to 7 rpm or less, and the pulling speed of the silicon single crystal is set to a pulling speed at which COP defects and dislocation clusters can be eliminated. From the quartz crucible, the interstitial oxygen concentration in the silicon single crystal is 6.0 × 10 ¹⁷ atoms / cm. ³ or less, including the n-type dopant variation Δρ plane resistivity in the radial direction of the silicon single crystal which is calculated from the following equation (1) is 5% or less After was pulled silicon single crystal to be, the same was pulled this silicon single-crystal silicon material in the quartz crucible by supplying melted and by Ru newly pulled another silicon single crystal from the quartz crucible, a plurality of It is characterized by growing a silicon single crystal.
Δρ = (maximum in-plane resistivity−minimum in-plane resistivity) / minimum in-plane resistivity × 100 (1)
However, in the formula (1), the maximum value of the in-plane resistivity and the minimum value of the in-plane resistivity are one in the wafer center on the radial straight line passing through the wafer center and two in the middle between the wafer center and the outer periphery. The maximum value and the minimum value of the in-plane resistivity measured at a total of five locations on the wafer outer periphery at two locations.

In the growth method according to the first aspect of the present invention, the silicon single crystal is pulled up from the silicon melt containing the n-type dopant using the CZ method, so that it is not necessary to irradiate the silicon single crystal with neutrons. As a result, there is a problem with phosphorus doping by neutron irradiation, that is, the productivity of single crystals that have been phosphorus doped by neutron irradiation is extremely low, and a sufficient amount cannot be supplied to the market, or damage recovery of single crystals by neutron irradiation is not possible. The problem of necessity can be solved. Further, after it was pulled silicon single crystal, another silicon single crystal silicon material is supplied and melted in the same quartz crucible was pulled up, with a silicon single crystal the same quality characteristics grown above the quartz crucible The silicon single crystal is newly pulled to grow a plurality of silicon single crystals, so-called multi-pulling. Thereby, a plurality of silicon single crystals with little variation in resistivity in the pulling axis direction can be pulled from the top to the bottom of the straight body portion of the silicon single crystal.

In addition , since a horizontal magnetic field was applied to the silicon melt, the rotational speed of the crucible was slowed, and the rotational speed of the single crystal was further slowed down, so that the concentration distribution of the n-type dopant in the radial direction of the single crystal was kept uniform, The interstitial oxygen concentration in the single crystal can be reduced.

It is a longitudinal section lineblock diagram of a growth device of a silicon single crystal of an embodiment of the present invention. The left half is a schematic diagram showing the generation behavior of crystal defects generated in a silicon single crystal grown in a hot zone with a fast cooling rate, and the right half is a single silicon grown in a hot zone suitable for growing a defect-free single crystal. It is a schematic diagram which shows the production | generation behavior of the crystal defect which generate | occur | produces in a crystal | crystallization. FIG. 4 is a graph showing the interstitial oxygen concentration in the silicon single crystal of Example 1. 4 is a diagram showing in-plane resistivity in the silicon single crystal of Example 1. FIG. FIG. 4 is a diagram showing variation in in-plane resistivity within the silicon single crystal of Example 1. It is a figure which shows the light scatterer (COP) generation | occurrence | production situation about the wafer of the reference example 2 and the comparative example 1. FIG. It is a figure which shows the yield of GOI measured about the wafer of the reference example 2 and the comparative example 1. FIG.

  Next, an embodiment for carrying out the present invention will be described based on the drawings. Although the apparatus used for this invention is not specifically limited, For example, the growing apparatus shown in FIG. 1 can be used. The apparatus for growing silicon single crystal 11 includes a main chamber 12 configured to be evacuated inside, and a quartz crucible 13 provided in the center of the chamber 12. The main chamber 12 is a cylindrical vacuum container. The quartz crucible 13 is placed on a graphite crucible, the upper end of a shaft 14 is connected to the bottom of the graphite crucible, and the lower end of the shaft 14 is driven to rotate and lift the quartz crucible 13 via the shaft 14. Means 16 are provided. Further, the outer peripheral surface of the quartz crucible 13 is surrounded by a cylindrical heater 17 at a predetermined interval from the outer peripheral surface of the quartz crucible 13. The outer peripheral surface of the heater 17 is surrounded by the cylindrical heat insulating cylinder 18 from the outer peripheral surface of the heater 17. Surrounded by a predetermined interval.

  On the other hand, a cylindrical pull chamber 19 having a smaller diameter than the main chamber 12 is connected to the upper end of the main chamber 12 so as to communicate with the inside. A pulling rotation means 20 is provided at the upper end of the pull chamber 19. The pulling rotation means 20 is configured to move up and down a pulling shaft 22 having a seed chuck 21 attached to the lower end, and to rotate the pulling shaft 22 about its axis. A seed crystal 23 is detachably attached to the seed chuck 21. After immersing the lower end of the seed crystal 22 in the silicon melt 15, the seed crystal 22 is rotated and pulled up by the pulling and rotating means 20, and the quartz crucible 13 is rotated and raised by the crucible driving means 16. The silicon single crystal 11 is pulled up and grown from the lower end of the seed crystal 23.

  In addition, this growth apparatus is provided with a raw material supply pipe 51 for supplying polycrystalline silicon raw material 52 to the quartz crucible 13 in order to supply the reduced silicon melt 15, and the silicon single crystal 11 is taken out from the growth apparatus. After that, the silicon melt 15 remaining in the quartz crucible 13 is supplied onto the liquid surface. The upper end side of the raw material supply pipe 51 is supported and suspended by a support means (not shown). As a result, pulling by multiple pulling is possible. In addition, although the raw material supply form which inserted the raw material supply pipe | tube 51 from the exterior of the growth apparatus was shown here, it is not limited to this, For example, inside the raw material supply apparatus which can open and close a bottom part in a growth apparatus Alternatively, the raw material may be supplied so as to be filled with the polycrystalline silicon raw material 52.

  An inert gas such as argon gas is circulated in the main chamber 12. One end of a gas supply pipe 24 is connected to the side wall of the pull chamber 19, and the other end of the gas supply pipe 24 is connected to a tank (not shown) that stores an inert gas. One end of a gas discharge pipe 26 is connected to the lower wall of the main chamber 12, and the other end of the gas discharge pipe 26 is connected to the suction port of the vacuum pump 27. The inert gas in the tank is introduced into the pull chamber 19 through the gas supply pipe 24, passes through the main chamber 12, and is then discharged from the main chamber 12 through the gas discharge pipe 26. . The gas supply pipe 24 and the exhaust pipe 26 are provided with first and second flow rate adjusting valves 41 and 42 for adjusting the flow rate of the inert gas flowing through these pipes, respectively.

  A heat shield 28 is provided in the main chamber 12 to block the irradiation of the radiant heat of the heater 17 to the outer peripheral surface of the silicon single crystal 11 and to rectify the inert gas. The heat shield 28 has a truncated cone-like cylinder that gradually decreases in diameter as it goes downward and surrounds the outer peripheral surface of the silicon single crystal 11 pulled up from the silicon melt 15 at a predetermined interval from the outer peripheral surface. 28a and a flange portion 28b that is connected to the upper edge of the cylindrical body 28a and projects outward in a substantially horizontal direction. In the heat shield 28, the flange portion 28b is placed on the heat retaining cylinder 18 via the ring plate 28c, so that the lower edge of the cylinder 28a is positioned above the surface of the silicon melt 15 with a predetermined gap. In this way, it is fixed in the main chamber 12. Further, the silicon melt 15 is configured to pull up the silicon single crystal 11 while applying a horizontal magnetic field 29. The horizontal magnetic field 29 causes the first and second coils 31 and 32 having the same coil diameter to be placed outward from the outer peripheral surface of the quartz crucible 13 at a predetermined distance in the horizontal direction and centered on the quartz crucible 13. It is arranged so as to oppose each other, and is generated by flowing currents in the same direction through these coils 31 and 32, respectively.

  A method for growing the silicon single crystal 11 using the apparatus configured as described above will be described. First, an n-type dopant such as P (phosphorus), As (arsenic), Sb (antimony) or the like is added before the silicon raw material is dissolved (or after the dissolution), and the silicon melt 15 contains the n-type dopant. Let The resistivity range of the silicon wafer required for IGBT is 10 Ωcm to 1000 Ωcm, and the content of the n-type dopant is adjusted so as to satisfy this resistivity range.

  Further, a horizontal magnetic field 29 is generated by flowing currents in the same direction through the first and second coils 31 and 32, respectively. The magnetic field strength of the horizontal magnetic field 29 is measured at the intersection of the surface of the silicon melt 15 and the central axis of the quartz crucible 13, and the first and second coils 31 so that the magnetic field strength is 0.2 T (Tesla) or more. , 32 is controlled. This is because if the magnetic field strength is less than 0.2 T, the effect of reducing the uptake of oxygen into the silicon single crystal 11 is diminished. However, if the magnetic field strength is excessively increased, the deterioration of the inner surface of the quartz crucible 13 may be promoted and the single crystal 11 may be dislocated. Therefore, the magnetic field strength is desirably 0.5 T or less.

The implementation of the embodiment of the present invention is a method for growing a silicon single crystal which COP defects and dislocation clusters are eliminated. FIG. 2 shows a case where the vertical axis is the ratio V / G where the pulling rate of the single crystal is V (mm / min) and the temperature gradient in the pulling axis direction near the solid-liquid interface is G (° C./min). It is a schematic diagram which shows the production | generation behavior of a crystal defect. In this embodiment, the pulling rate of the silicon single crystal is raised under conditions that allow COP defects and dislocation clusters to be eliminated, that is, growth conditions that become an A region or an A region and an OSF ring in FIG. Conditions other than the pulling speed and hot zone can be the same as the pulling conditions of the reference embodiment described later.

In this embodiment, since COP defects and dislocation clusters have already been eliminated in the grown silicon single crystal, the pulling speed is lower than in the reference embodiment described later, and the productivity of the silicon single crystal is high. However, although it is disadvantageous, there is an advantage that the subsequent oxidation heat treatment step can be omitted.

In the reference embodiment, a silicon single crystal including a COP defect generation region is grown. In this reference embodiment, the grown silicon single crystal contains COP defects having a predetermined size and density, and therefore, it is necessary to perform subsequent oxidation heat treatment. However, compared to the form of implementation of the present invention, it is possible to increase the pulling rate, which is advantageous in terms of productivity of the silicon single crystal.

  The COP defect contained in the grown silicon single crystal needs to have a size and density that can be eliminated in the subsequent heat treatment, and therefore needs to be in a desired pulling condition. For example, of the temperature gradient in the pulling axis direction of the single crystal 11 in the temperature range from the melting point to 1370 ° C. of the center of the silicon single crystal 11 to be grown, the temperature gradient at the center of the single crystal 11 is Gc. The silicon single crystal 11 is grown so that COP is generated under the condition satisfying the relationship of Gc / Ge ≧ 1, where Ge is the temperature gradient of the outer periphery of the substrate. By growing the silicon single crystal 11 so that COP is generated under the condition satisfying the relationship of Gc / Ge ≧ 1, the single crystal 11 having a small COP size and a low density can be obtained.

In FIG. 2, the hot zone A is raised under the condition that the temperature gradients Gc and Ge are Gc / Ge <1, and the hot zone B is the relationship that the temperature gradients Gc and Ge are Gc / Ge ≧ 1. It was pulled up under the conditions to satisfy. As shown in FIG. 2, when a single crystal is grown in the hot zone A, that is, a hot zone having a high cooling rate suitable for reducing the COP size by increasing the pulling rate, the size of the COP in the single crystal is reduced. However, the density will increase. Therefore, it becomes difficult to extinguish COP over the entire area in the radial direction and thickness direction of the wafer, that is, in the pulling axis direction, by the subsequent oxidation heat treatment. On the other hand, when a single crystal is grown in the hot zone B, the COP size in the silicon single crystal is smaller than that pulled in the hot zone A. In particular, in the region B surrounded by the two-dot chain line in FIG. 2, the COP size is small and the density is low, so that the COP can be extinguished over the entire area in the radial direction and the thickness direction of the wafer by the subsequent oxidation heat treatment. In this reference embodiment, the COP size and density in the silicon single crystal are increased under the condition that the region B in FIG. Specifically, the COP defects in the silicon single crystal pulled up under such conditions are preferably 100 nm or less in size and 3 × 10 ⁶ atoms / cm ³ or less in density.

The rotation speed of the quartz crucible 13 during the growth of the silicon single crystal 11 is set to 1.5 rpm or less, preferably 0.3 rpm or less. The rotation speed of the silicon single crystal 11 during the growth is preferably 7 rpm or less, more preferably Set to 5 rpm or less. Here, the rotation speed of the quartz crucible 13 is 1.5 rpm or less and the rotation speed of the silicon single crystal 11 is 7 rpm or less. The interstitial oxygen concentration of the silicon single crystal 11 is 6.0 × 10 ¹⁷ atoms / cm. ^This is because the variation of the in-plane resistivity in the radial direction in the silicon single crystal 11 is kept at 5% or less even when the silicon single crystal 11 is pulled up from the silicon melt 15 containing the n-type dopant. . Note that the lower limit of the rotational speed of the silicon single crystal 11 is desirably 0.5 rpm or more, and if it is slower than this, the silicon single crystal 11 is deformed or the in-plane resistivity distribution is deteriorated. Become. As described above, by satisfying the condition of Gc / Ge ≧ 1, the shape of the solid-liquid interface between the single crystal 11 and the silicon melt 15 is flattened, and in this state, the horizontal magnetic field 29 is applied to the silicon melt 15. Is applied, the rotation speed of the quartz crucible 13 is decreased, and the rotation speed of the single crystal 11 is further decreased, so that the concentration distribution of the n-type dopant in the radial direction of the single crystal 11 is kept uniform and the single crystal 11 The interstitial oxygen concentration can be reduced.

In the present invention, the silicon single crystal 11 is pulled by a multiple pulling method. In the pulling by this multiple pulling method, the resistivity of the single crystal 11 in the pulling axis direction is determined from the diameter of the single crystal 11 to be pulled, the target resistivity range, and the segregation coefficient of the n-type dopant added to the silicon melt 15. The length from the top to the bottom of the straight body portion of the single crystal 11 to be pulled up is set in advance so that the variation is not more than a predetermined value. And after pulling up the single crystal 11 to this preset length, a silicon raw material is supplied and melted in the same quartz crucible from the raw material supply pipe 51 provided in the growing apparatus, and the seed crystal 22 is again melted into the silicon melt 15. A plurality of silicon single crystals are grown by immersing them and pulling up another silicon single crystal from the same quartz crucible. Thereby, the single crystal 11 with less variation in resistivity in the pulling axis direction in the single crystal 11 can be grown.

  In order to manufacture a wafer for IGBT from the silicon single crystal 11 grown in this way, a silicon wafer obtained by slicing from the silicon single crystal 11 is subjected to 1100 to 1300 ° C. in an oxygen gas atmosphere, preferably Heating is performed to a predetermined temperature within a range of 1150 to 1200 ° C., and heat treatment is performed at this predetermined temperature for 2 to 5 hours, preferably 3 to 4 hours. As a result, the COP can be eliminated over the entire area in the radial direction and the thickness direction of the wafer. Here, the heat treatment holding temperature is limited to the range of 1100 to 1300 ° C. The COP is difficult to disappear when the temperature is lower than 1100 ° C., and when the temperature exceeds 1300 ° C., the thermal load applied to the wafer becomes excessive and slips on the wafer This is because dislocations occur. Furthermore, the holding time of the heat treatment is limited to the range of 2 to 5 hours because the COP cannot be sufficiently eliminated in less than 2 hours, and even if the heat treatment is carried out for more than 5 hours, the COP disappearance effect is not so much. Because it doesn't change. Thereby, the COP defect existing in the grown silicon single crystal can be eliminated over the entire area of the silicon wafer, and can be used as a wafer for IGBT.

  Next, examples of the present invention will be described in detail together with comparative examples.

<Example 1>
A silicon single crystal 11 was grown by the CZ method using the growth apparatus shown in FIG. Specifically, first, the diameter of the silicon single crystal 11 to be pulled is 210 mm, the target resistivity is 70 Ωcm, and the resistance in the pulling axis direction is determined from the segregation coefficient of phosphorus, which is an n-type dopant added to the silicon melt 15. The length from the top to the bottom of the straight body portion of the single crystal 11 to be pulled up was set to 700 mm in advance so that the variation in rate was 5% or less.

  Next, the silicon raw material was put into a quartz crucible 13 installed in the growth apparatus with an initial charge amount of 140 kg, and phosphorus was added as an n-type dopant for adjusting the resistivity and melted. A magnetic field strength of 0.3 T (Tesla) was applied to the silicon melt 15 by applying currents in the same direction to the first and second coils 31 and 32 of the growth apparatus.

Next, the seed crystal 23 is immersed in the silicon melt 15, the rotational speed of the seed crystal 23, that is, the rotational speed of the growing single crystal 11 is 5 rpm, and the rotational speed of the quartz crucible 13 is 0.1 rpm. The silicon single crystal 11 was grown by pulling up the seed crystal 23 while rotating it. At this time, V / G was set to a condition of 0.21 [mm ² / (min · ° C.)] so as to be an A region in FIG. The temperature gradient Gc at the center of the single crystal 11 and the temperature gradient Ge at the outer periphery of the single crystal 11 were set to Gc / Ge = 1.1.

  In this way, the silicon single crystal 11 having a length from the top to the bottom of the straight body portion of the single crystal 11 to be pulled up to 700 mm and free from COP defects and dislocation clusters was grown.

Subsequently, after the polycrystalline silicon raw material 52 is supplied from the raw material supply pipe 51 provided in the growing apparatus into the same quartz crucible 13 and melted, the same condition as above is applied, from the top to the bottom of the straight body part. By pulling up the 700 mm-long silicon single crystal 11 from the same quartz crucible 13, another silicon single crystal 11 was grown, and a total of three silicon single crystals 11 were grown.

<Evaluation 1>
For a total of three silicon single crystals grown according to Example 1, the presence or absence of COP defects, the presence or absence of cluster dislocations, the interstitial oxygen concentration (Oi) in the silicon single crystal, the in-plane resistivity in the radial direction, and the in-plane resistivity The variation (Δρ) was evaluated. Specifically, for each of the grown silicon single crystals, the above evaluation items were evaluated for each wafer cut out at a position of 100 mm, 300 mm, 500 mm, and 700 mm from the top of the straight body portion. The results are shown in the following Table 1 and FIGS. FIG. 4 is an evaluation of a silicon single crystal pulled up to the third. The state of COP generation was confirmed using an infrared scattering tomograph (Mitsui Metals Co., Ltd .: MO441). The interstitial oxygen concentration (Oi) is a value measured according to Fourier transform infrared spectrophotometry standardized by ASTM F-121 (1979). The in-plane resistivity variation ([Delta] [rho]) indicates a value [Delta] [rho] was calculated by the equation (1) follows from the wafer plane resistance ratio in the radial direction and the measurement.

Δρ = (maximum in-plane resistivity−minimum in-plane resistivity) / minimum in-plane resistivity × 100 (1)
As shown in FIG. 4, the in-plane resistivity in the radial direction is measured at one wafer center on the radial straight line passing through the cut silicon wafer center, two intermediate points between the wafer center and the outer periphery, and two wafer outer periphery locations. The maximum value of the in-plane resistivity and the minimum value of the in-plane resistivity in Equation (1) are the maximum value and the minimum value of these in-plane resistivities.

表１及び図３〜図５から明らかなように、育成されたシリコン単結晶は、直胴部トップからボトムまでＣＯＰ欠陥及び転位クラスタが排除されている。また、直胴部トップからボトムまでの格子間酸素濃度が６．０×１０¹⁷ａｔｏｍｓ／ｃｍ³以下である。更に、直胴部トップからボトムまでの径方向の面内抵抗率のバラツキが５％以下であり、径方向の面内抵抗率及び引上げ軸方向の抵抗率のバラツキが共に少ないことが判る。このことから、本発明の育成方法により育成されたシリコン単結晶は、ＩＧＢＴ用のシリコンウェーハの製造に好適であることが確認された。

As apparent from Table 1 and FIGS. 3 to 5, the grown silicon single crystal has COP defects and dislocation clusters eliminated from the top to the bottom of the straight body portion. Further, the interstitial oxygen concentration from the top to the bottom of the straight body is 6.0 × 10 ¹⁷ atoms / cm ³ or less. Furthermore, the variation in the in-plane resistivity in the radial direction from the top to the bottom of the straight body portion is 5% or less, and it can be seen that both the in-plane resistivity in the radial direction and the variation in the resistivity in the pulling axis direction are small. From this, it was confirmed that the silicon single crystal grown by the growing method of the present invention is suitable for manufacturing a silicon wafer for IGBT.

< Reference Example 1 >
A silicon single crystal 11 was grown by the CZ method using the growth apparatus shown in FIG. Specifically, first, the diameter of the silicon single crystal 11 to be pulled is 210 mm, the target resistivity is 70 Ωcm, and the resistance in the pulling axis direction is determined from the segregation coefficient of phosphorus, which is an n-type dopant added to the silicon melt 15. The length from the top to the bottom of the straight body portion of the single crystal 11 to be pulled up was set to 700 mm in advance so that the variation in rate was 5% or less.

  Next, the silicon raw material 15 was put into a quartz crucible 13 installed in the growth apparatus with an initial charge amount of 140 kg, and phosphorus was added and melted as an n-type dopant for adjusting the resistivity. A magnetic field strength of 0.3 T (Tesla) was applied to the silicon melt 15 by applying currents in the same direction to the first and second coils 31 and 32 of the growth apparatus.

Next, the seed crystal 23 is immersed in the silicon melt 15, the rotational speed of the seed crystal 23, that is, the rotational speed of the growing single crystal 11 is 5 rpm, and the rotational speed of the quartz crucible 13 is 0.1 rpm. While rotating, the seed crystal 23 was pulled up to grow the silicon single crystal 11. At this time, V / G was set to a condition of 0.23 to 0.33 [mm ² / (min · ° C.)] so as to be a region B in FIG. This V / G range was determined by heat transfer calculation. The temperature gradient Gc at the center of the single crystal 11 and the temperature gradient Ge at the outer periphery of the single crystal 11 were set to Gc / Ge = 1.12.

  In this way, the silicon single crystal 11 having a length from the top to the bottom of the straight body portion of the single crystal 11 to be pulled up to 700 mm and including COP defects was grown.

Subsequently, after the polycrystalline silicon raw material 52 is supplied from the raw material supply pipe 51 provided in the growing apparatus into the same quartz crucible 13 and melted, the same condition as above is applied, from the top to the bottom of the straight body part. By pulling up the 700 mm-long silicon single crystal 11 from the quartz crucible 13, another silicon single crystal 11 was grown, and a total of three silicon single crystals 11 were grown.

<Evaluation 2>
For a total of three silicon single crystals grown in Reference Example 1 , the size and density of COP defects, presence or absence of cluster dislocations, interstitial oxygen concentration (Oi) in the silicon single crystal, radial in-plane resistivity, in-plane Resistivity variation (Δρ) was evaluated. Specifically, for each of the grown silicon single crystals, the above evaluation items were evaluated for each wafer cut out at a position of 100 mm, 300 mm, 500 mm, and 700 mm from the top of the straight body portion. The results are shown in Table 1 below. In addition, the size and density of the COP defect were measured using an infrared scattering tomograph (Mitsui Metals Co., Ltd .: MO441). The interstitial oxygen concentration (Oi) is a value measured according to Fourier transform infrared spectrophotometry standardized by ASTM F-121 (1979). Further, regarding the variation (Δρ) of the in-plane resistivity, the value Δρ calculated in the same manner as in the evaluation 1 is shown.

表２から明らかなように、参考例１で育成されたシリコン単結晶内のＣＯＰは、直胴部トップからボトムまで、そのサイズが小さく、また密度も低いことが判る。また、直胴部トップからボトムまでの格子間酸素濃度が６．０×１０¹⁷ａｔｏｍｓ／ｃｍ³以下である。更に、直胴部トップからボトムまでの径方向の面内抵抗率のバラツキが５％以下であり、径方向の面内抵抗率及び引上げ軸方向の抵抗率のバラツキが共に少ないことが判る。このことから、本発明の育成方法により育成されたシリコン単結晶は、ＩＧＢＴ用のシリコンウェーハの製造に好適であることが確認された。

As is apparent from Table 2, the COP in the silicon single crystal grown in Reference Example 1 has a small size and a low density from the top to the bottom of the straight body. Further, the interstitial oxygen concentration from the top to the bottom of the straight body is 6.0 × 10 ¹⁷ atoms / cm ³ or less. Furthermore, the variation in the in-plane resistivity in the radial direction from the top to the bottom of the straight body portion is 5% or less, and it can be seen that both the in-plane resistivity in the radial direction and the variation in the resistivity in the pulling axis direction are small. From this, it was confirmed that the silicon single crystal grown by the growing method of the present invention is suitable for manufacturing a silicon wafer for IGBT.

< Reference Example 2 >
A silicon wafer cut from the silicon single crystal grown in Reference Example 1 (of the wafer cut from the third silicon single crystal, a wafer 300 mm from the top of the straight body) was subjected to an oxidation heat treatment as Reference Example 2 . . Specifically, heat treatment was performed in an atmosphere of 100% oxygen gas up to 1180 ° C. and maintained at this temperature for 3 hours.

<Comparative Example 1>
Comparative Example 1 was a wafer that was not subjected to an oxidation heat treatment on a silicon wafer cut out from the silicon single crystal grown in Reference Example 1 (of the wafer cut out from the third silicon single crystal, 300 mm from the top of the straight body). .

<Evaluation 3>
For the silicon wafer of Reference Example 2 , the presence or absence of COP defects and the yield of GOI were evaluated. The occurrence of COP was confirmed using an infrared scattering tomograph (MO601). Moreover, the yield of GOI was specifically determined by the TZDB (Time Zero Dielectric Breakdown) method. For the yield of GOI, a gate oxide film (oxide film) and an electrode are formed on a silicon wafer to form a MOS (Metal Oxide Semiconductor) structure, and then a voltage is applied to the electrode to break down the gate oxide film and break down. It was determined by measuring the voltage. Here, the dielectric breakdown of the gate oxide film occurred at the defective portion of the wafer. The specific measurement of the breakdown voltage of the gate oxide film by the TZDB method was performed as follows. First, a gate oxide film (SiO ₂ ) having a thickness of 25 nm was formed on the wafer surface. Next, a polysilicon electrode having a gate electrode area of 10 mm ² was formed on the gate oxide film. Further, a voltage was applied between the wafer and the polysilicon electrode by a step voltage application method, and finally a voltage having a judgment electric field strength of 11 MV / cm was applied. The measurement temperature was room temperature (25 ° C.). These results are shown in FIG. 6 and FIG.

As is apparent from FIGS. 6 and 7, it can be seen that the COP defect disappears and the GOI yield is improved to 100% by performing the acid heat treatment. Therefore, silicon grown by the growing method single crystal and silicon wafers produced by the manufacturing method of this, it was confirmed to be suitable for a silicon wafer for IGBT.

11 Silicon single crystal 12 Main chamber (chamber)
13 Quartz crucible 15 Silicon melt

Claims (1)

Silicon melt is stored in a quartz crucible housed in a chamber, and a seed crystal is immersed in this silicon melt and pulled up while rotating, thereby pulling and growing the silicon single crystal from the seed crystal. In the training method,
A horizontal magnetic field of 0.2 T or more is applied to the silicon melt in the quartz crucible, the rotation speed of the quartz crucible is 1.5 rpm or less, the rotation speed of the growing silicon single crystal is 7 rpm or less,
The pulling rate of the silicon single crystal is defined as a pulling rate that can eliminate COP defects and dislocation clusters.
From the quartz crucible, the interstitial oxygen concentration in the silicon single crystal is 6.0 × 10 ¹⁷ atoms / cm ³ or less, and the in-plane resistivity in the radial direction of the silicon single crystal calculated from the following formula (1) After pulling up a silicon single crystal containing an n-type dopant having a variation Δρ of 5% or less,
A silicon raw material is supplied and melted in the same quartz crucible where the silicon single crystal is pulled up, and a plurality of silicon single crystals are grown by pulling up another silicon single crystal from the quartz crucible. A method for growing a silicon single crystal characterized.
Δρ = (maximum in-plane resistivity−minimum in-plane resistivity) / minimum in-plane resistivity × 100 (1)
However, in the formula (1), the maximum value of the in-plane resistivity and the minimum value of the in-plane resistivity are one in the wafer center on the radial straight line passing through the wafer center and two in the middle between the wafer center and the outer periphery. The maximum value and the minimum value of the in-plane resistivity measured at a total of five locations on the wafer outer periphery at two locations.

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