JP2010040587A - Method of manufacturing silicon wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicon wafer manufacturing method capable of improving Grown-in defect reduction power while suppressing occurrence of slip during rapid heating / cooling heat treatment.
SOLUTION: A silicon wafer manufactured from a silicon single crystal ingot grown by the Czochralski method has a maximum reached temperature (T in an oxidizing gas atmosphere having an oxygen gas partial pressure of 20% to 100%. ₁ ) Perform rapid heating / cooling heat treatment at 1300 ° C to 1380 ° C [Selection] Fig. 2

Description

  The present invention relates to a method for manufacturing a silicon wafer used for a substrate of a semiconductor device.

  With the recent high integration of semiconductor devices, quality requirements for silicon wafers used as substrates have become severe. In particular, there is a strong demand for reducing grown-in defects in the device active region of silicon wafers.

  The grown-in defects include, for example, aggregates of supersaturated vacancy point defects called COP (Crystal Originated Particles) and LSTD (Laser Scattering Tomography Defects), and OSF (Oxidation Induced Fracture). There are oxygen precipitates such as OSF nuclei and BMD nuclei to be (Balk Micro Defect), and supersaturated interstitial silicon type point defect aggregates called dislocation clusters.

  Among these, the interstitial silicon-type point defect aggregates (transition clusters) can be prevented by adjusting the pulling conditions during pulling of the single crystal. It is very difficult to prevent the collection and the generation of oxygen precipitates.

  In addition, when the oxygen precipitate is present in a bulk region other than the device active region, it is effective because it has a gettering effect on heavy metals and the like, but the oxygen precipitate exists in the device active region. In this case, it is not preferable because it causes a decrease in device yield.

  Various techniques have been disclosed as methods for reducing such grown-in defects.

  For example, when growing a silicon single crystal by the Czochralski method, by controlling the pulling conditions (pulling speed V, intra-crystal temperature gradient G), a silicon single crystal wafer having no Grown-in defects on the entire surface can be obtained. A manufacturing technique is disclosed (for example, Patent Document 1).

  In addition, by forming an epitaxial layer on the surface of a silicon wafer produced from a CZ silicon single crystal grown so as to control the carbon concentration, nitrogen concentration, and oxygen concentration in the silicon wafer to predetermined values, excellent crystallinity and A technique capable of obtaining an epitaxial wafer having IG capability is disclosed (for example, Patent Document 2).

  In addition, a technique for preventing the generation of defects in a wafer by heat-treating a silicon wafer in a temperature region of 1050 ° C. or higher in an atmosphere of hydrogen, argon, or a mixture thereof is disclosed (for example, Patent Document 3).

  Furthermore, in recent years, as a technique for easily producing a silicon wafer having a very low defect in the surface layer of the wafer with high productivity, a technique for subjecting a silicon wafer to a rapid thermal process (RTP: Rapid Thermal Process) is known. It has been.

  For example, a silicon wafer cut out from a perfect region including a region where a ring-shaped oxidation-induced stacking fault occurs (a region where an interstitial silicon type point defect aggregate and a hole type point defect aggregate do not exist) By applying heat treatment such as rapid heating / cooling in an atmosphere of argon or a mixed gas thereof, there are defects due to residual crystal defects centered on OSF and the like, and defects due to residual processing due to mechanical processing such as polishing. A technique capable of obtaining a silicon wafer that is reduced and has excellent GOI characteristics is disclosed (for example, Patent Document 4).

  In addition, the silicon wafer is exposed to an oxygen-containing atmosphere at least temporarily, and the heat treatment is performed at a temperature selected so as to satisfy a predetermined inequality, so that COPs are not contained over a major portion of the wafer thickness. A technique capable of obtaining a silicon wafer is disclosed (for example, Patent Document 5).

Furthermore, a silicon substrate manufactured by the Czochralski method is made to have a maximum holding temperature of 1125 ° C. or higher and a melting point of silicon or lower and a holding time of 5 seconds or longer in a 100% nitrogen or 100% oxygen or mixed atmosphere of oxygen and nitrogen. After performing the heat treatment, it has the desired oxygen precipitation characteristics without controlling the oxygen concentration in the silicon substrate produced by the CZ method by rapidly cooling from the maximum holding temperature at a cooling rate of 8 ° C./second or more. A technique capable of obtaining a silicon substrate is disclosed (for example, Patent Document 6).
Japanese Patent Laid-Open No. 08-330316 JP 2006-188423 A JP 2002-231726 A JP 2003-224130 A JP 2003-297840 A JP 2000-31150 A

  However, the technique described in Patent Document 1 has a problem that a Grown-in defect occurs due to a slight change in the pulling condition, and therefore, it is very difficult to control the pulling condition.

  Further, the technique for forming an epitaxial layer described in Patent Document 2 has a problem that the cost is very high, and the epitaxial layer is formed to a thickness of, for example, 5 μm or more in order to form a device active region. It was necessary, and the productivity was very poor and the cost was high.

  In addition, the heat treatment technique described in Patent Document 3 is not preferable because the heat treatment time is long, so that the productivity is poor and the slip easily occurs during the heat treatment.

  In addition, the rapid heating / cooling heat treatment technique described in Patent Document 4 uses a perfect region in which an interstitial silicon type point defect aggregate and a hole type point defect aggregate do not exist as the silicon wafer before the processing. Because of this premise, there is a limit to the reduction of grown-in defects in rapid heating / cooling heat treatment.

  In addition, the rapid heating / cooling heat treatment technique described in Patent Document 5 uses a silicon wafer obtained from a single crystal controlled so that extremely small COP is generated at a high concentration as a starting material for the heat treatment. Similarly, there is a limit to the reduction of Grown-in defects in the rapid heating / cooling thermal process.

  In addition, the rapid heating / cooling heat treatment technique described in Patent Document 6 aims to obtain a silicon substrate having desired oxygen precipitation characteristics without controlling the oxygen concentration in the silicon substrate manufactured by the CZ method. However, it was not intended to reduce Grown-in defects in the device active region of the silicon wafer.

  The present invention has been made in view of the above-described circumstances, and a silicon wafer manufacturing method capable of improving the reduction of Grown-in defects while suppressing the occurrence of slip during rapid heating / cooling heat treatment. The purpose is to provide.

  The method for producing a silicon wafer according to the present invention includes an oxidizing gas atmosphere having an oxygen gas partial pressure of 20% to 100% with respect to a silicon wafer produced from a silicon single crystal ingot grown by the Czochralski method. Among these, rapid heating / cooling heat treatment is performed at a maximum temperature of 1300 ° C. to 1380 ° C.

  By providing such a configuration, it is possible to improve the Grown-in defect reduction power while suppressing the occurrence of slip during the rapid heating / cooling heat treatment.

  The maximum temperature reached is preferably 1350 ° C. or higher and 1380 ° C. or lower.

  By providing such a configuration, it is possible to further improve the ability to reduce Grown-in defects while suppressing the occurrence of slip during the rapid heating / cooling heat treatment.

The film thickness variation in the wafer surface of the silicon oxide film formed by the rapid heating / cooling heat treatment is such that the maximum value of the film thickness is t _OX max, the minimum value of the film thickness is t _OX min, When the average value is t _OX ave, the ratio calculated by (t _OX max−t _OX min) / (t _OX ave) is preferably within 1.5%.

  By providing such a configuration, it is possible to further suppress the occurrence of slip during the rapid heating / cooling heat treatment.

  Aggregates of supersaturated vacancy-type point defects existing in at least the device active region of the silicon wafer before the rapid heating / cooling heat treatment have a maximum size in terms of the diameter of a sphere having the same volume as the aggregate. It is preferable that it is 180 nm or less.

  By providing such a configuration, aggregates of supersaturated hole-type point defects generated by the rapid heating / cooling heat treatment can be surely eliminated.

  The silicon single crystal ingot is preferably grown without nitrogen doping.

  By providing such a configuration, the size and density of the grown-in defects in the axial direction of the grown silicon single crystal ingot can be stabilized.

The solid solution oxygen concentration in the silicon single crystal ingot is preferably in the range of 5 × 10 ¹⁷ atoms / cm ^{3 to} 1.3 × 10 ¹⁸ atoms / cm ³ .

  By providing such a configuration, it is possible to obtain a silicon wafer having a relatively large reduction rate of the LSTD density in the rapid heating / rapid cooling heat treatment and a high oxygen precipitate density.

  It is preferable to polish the surface of the silicon wafer subjected to the rapid heating / cooling heat treatment.

  With such a configuration, even when COP remains near the surface of the wafer, a high-quality silicon wafer with few grown-in defects can be easily manufactured.

  By applying the rapid heating / rapid cooling heat treatment, agglomerates of supersaturated vacancy-type point defects and oxygen precipitates existing in at least the device active region of the silicon wafer are eliminated to form a DZ layer, and the DZ layer is formed. It is preferable to introduce solid solution oxygen into the layer.

  By providing such a configuration, since the solid solution oxygen concentration in the DZ layer becomes high, the dislocations generated by the stress are pinned by the solid solution oxygen, so that the extension of dislocations can be suppressed.

  The present invention provides a method for producing a silicon wafer that can improve the reduction of Grown-in defects while suppressing the occurrence of slip during rapid heating / cooling heat treatment. Therefore, a high-quality silicon wafer with high productivity, low cost and few grown-in defects can be manufactured.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an outline of an example of an RTP apparatus used in the method for producing a silicon wafer of the present invention.

  As shown in FIG. 1, the RTP apparatus 10 used in the method for producing a silicon wafer of the present invention is separated from the reaction tube 20 provided with the atmospheric gas inlet 20 a and the atmospheric gas outlet 20 b and at the upper part of the reaction tube 20. And a plurality of lamps 30 arranged in the manner described above, and a wafer support 40 that supports the wafer W in the reaction space 25 in the reaction tube 20. The wafer support unit 40 includes an annular susceptor 40a that directly supports the wafer W, and a stage 40b that supports the susceptor 40a. The reaction tube 20 is made of, for example, quartz. The lamp 30 is composed of, for example, a halogen lamp. The susceptor 40a is made of silicon, for example. The stage 40b is made of, for example, quartz.

  When performing rapid heating / cooling heat treatment (RTP: Rapid Thermal Process) on the wafer W using the RTP apparatus 10 shown in FIG. 1, the wafer W is introduced from a wafer introduction port (not shown) provided in the reaction tube 20. Is introduced into the reaction space 25, the wafer W is supported on the susceptor 40a of the wafer support portion 40, an atmospheric gas to be described later is introduced from the atmospheric gas inlet 20a, and the surface of the wafer W is irradiated with the lamp 30 by lamp irradiation. It is done by doing. The temperature control in the reaction space 25 in the RTP apparatus 10 is performed by adjusting the average temperature in the wafer surface in the wafer radial direction below the wafer W by a plurality of radiation thermometers 50 embedded in the stage 40b of the wafer support 40. Based on the measured temperature, the plurality of halogen lamps 30 are controlled (individual ON-OFF control of each lamp, emission intensity control of emitted light, etc.).

  Next, the manufacturing method of the silicon wafer of this invention is demonstrated.

  The method for producing a silicon wafer according to the present invention includes an oxidizing gas atmosphere having an oxygen gas partial pressure of 20% to 100% with respect to a silicon wafer produced from a silicon single crystal ingot grown by the Czochralski method. Among them, rapid heating / cooling heat treatment is performed at a maximum temperature of 1300 ° C. to 1380 ° C.

  The silicon single crystal ingot is grown by the Czochralski method by a known method.

  That is, the polycrystalline silicon filled in the quartz crucible is heated to form a silicon melt, the seed crystal is brought into contact with the silicon melt from above the liquid surface, and the seed crystal and the quartz crucible are pulled up while rotating to a desired diameter. A silicon single crystal ingot is manufactured by expanding the diameter and growing the straight body portion.

  The silicon single crystal ingot thus obtained is processed into a silicon wafer by a known method.

  That is, after a silicon single crystal ingot is sliced into a wafer shape with an inner peripheral blade or a wire saw, a silicon wafer is manufactured through processing steps such as chamfering, lapping, etching, and polishing of the outer peripheral portion. Note that the processing steps described here are exemplary, and the present invention is not limited to this processing step.

  Next, rapid heating / cooling heat treatment is performed on the manufactured silicon wafer at an ultimate temperature of 1300 ° C. to 1380 ° C. in an oxidizing gas atmosphere having an oxygen gas partial pressure of 20% to 100%. .

  The rapid heating / cooling heat treatment is performed using, for example, an RTP apparatus 10 as shown in FIG. 1 and using an oxidizing gas atmosphere having an oxygen gas partial pressure of 20% or more and 100% or less as an atmosphere gas. Note that the oxygen gas partial pressure referred to here refers to the oxygen gas partial pressure in the mixed gas (atmosphere gas) supplied to the reaction tube 20 when described with reference to FIG.

  Thus, by using an oxidizing gas atmosphere having an oxygen gas partial pressure of 20% or more and 100% or less as the atmosphere gas, the ability to reduce grown-in defects in rapid heating / cooling heat treatment can be greatly improved. .

  Note that when the oxygen gas partial pressure in the oxidizing gas atmosphere is less than 20%, the LSTD density reducing power in the rapid heating / rapid cooling heat treatment is extremely reduced, which is not preferable.

  The oxidizing gas atmosphere here refers to a mixed gas or oxygen 100% gas containing an oxygen gas partial pressure of 20% or more and less than 100%. Of these, the gas other than the oxygen gas in the mixed gas is preferably an inert gas.

  When nitrogen gas is used as a gas other than the oxygen gas, a nitride film is formed on the surface of the silicon wafer in the rapid heating / cooling heat treatment, and a new etching process is added to remove the nitride film. This is not preferable because the number of steps increases. When hydrogen gas is used as a gas other than the oxygen gas, a mixed gas of oxygen and hydrogen is not preferable because there is a risk of explosion.

  As the inert gas, it is mainly preferable to use argon gas. By using argon gas, good rapid heating / cooling heat treatment can be performed without causing the above-mentioned problems.

  FIG. 2 is an explanatory view showing an example of a temperature process in the rapid heating / cooling heat treatment.

  The rapid heating / cooling heat treatment is performed by, for example, a temperature process as shown in FIG. 2 using an RTP apparatus 10 as shown in FIG.

That is, the manufactured silicon wafer is placed in the reaction tube 20 of the RTP apparatus 10 at a desired temperature T ₀ (for example, 500 ° C.), and an oxygen gas partial pressure is 20% or more and 100% or less. in the middle, until the desired maximum temperature _T 1 (1300 ° C. or higher 1380 ° C. or less), a desired heating rate DerutaTu (e.g., 75 ° C. / sec) was heated, in a desired maximum temperature _{T 1,} the desired Hold time t (for example, 15 sec). Thereafter, the temperature is lowered to a desired temperature T ₀ (eg, 500 ° C.) at a desired temperature drop rate ΔTd (eg, 25 ° C./sec), and then the silicon wafer is taken out from the reaction tube 20.

That is, rapid thermal heat treatment as referred to herein refers to a heat treatment with rapid heating rate DerutaTu, a temperature process including a short retention time t and a fast cooling rate ΔTd at the maximum temperature T _1.

  The high temperature increase rate ΔTu referred to here is preferably 10 ° C./sec or more, the short holding time t is preferably 1 sec or more and 60 sec or less, and the high temperature decrease rate ΔTd is Preferably, it means 10 ° C./sec or more. Thus, rapid heating / cooling heat treatment with high productivity can be realized.

As described above, the maximum temperature T ₁ is preferably 1300 ° C. or higher and 1380 ° C. or lower.

As described above, the maximum temperature T ₁ referred to in the present application is the in-wafer 9 in the wafer radial direction below the wafer W when the wafer W is installed in the RTP apparatus 10 as shown in FIG. The average temperature of a point.

As described above, by setting the maximum temperature T ₁ to 1300 ° C. or higher and 1380 ° C. or lower, it is possible to improve the reduction of Grown-in defects while suppressing the occurrence of slip during the rapid heating / cooling heat treatment. it can.

The best case reached temperature T ₁ is less than 1300 ° C. is not preferable because the reduction force of LSTD density in rapid thermal heat treatment is lowered. Further, when the maximum temperature T ₁ exceeds 1380 ° C., a large slip is generated in the silicon wafer subjected to the rapid heating / cooling heat treatment, which is not preferable. Further, if the maximum temperature T ₁ exceeds 1380 ° C., there is a problem in durability as an RTP apparatus, so that the deterioration of the RTP apparatus is accelerated and eventually the device characteristics of the silicon wafer are deteriorated. It is not preferable.

  As described above, since the method for manufacturing a silicon wafer according to the present invention has the above-described configuration, it is possible to improve the reduction of Grown-in defects while suppressing the occurrence of slip during rapid heating / cooling heat treatment. Can be made. Therefore, a high-quality silicon wafer with high productivity, low cost and few grown-in defects can be manufactured.

  Next, the mechanism by which the LSTD density according to the present invention is reduced will be considered. FIG. 3 is a conceptual diagram for explaining a mechanism for reducing the LSTD density according to the present invention.

When the rapid heating of the rapid heating / cooling heat treatment is performed in an oxidizing gas atmosphere having a high oxygen partial pressure of 20% or more as in the present invention, the surface of the silicon wafer is oxidized and suddenly enters the silicon wafer. Oxygen (O ₂ ) and Interstitial-Si (hereinafter referred to as “i-Si”) are introduced (FIG. 3A). After that, during the high temperature treatment, oxygen contained in the inner wall oxide film formed on the inner wall of the COP is dissolved in the silicon wafer and is generated as solid solution oxygen (Oi) in the wafer (FIG. 3B). The inner wall oxide film of the COP is removed by the generation of the dissolved oxygen (Oi), and the COP disappears by filling the i-Si introduced into the COP from which the inner wall oxide film has been removed, so-called DZ (Detented Zone). ) Layer is formed (FIG. 3C). Although not shown, the oxygen precipitates present in the DZ layer disappear with the disappearance of the COP.

  Note that the solid solution oxygen remains in the formed DZ layer (FIG. 3C). Accordingly, since the concentration of dissolved oxygen in the DZ layer is increased, dislocations generated by stress from the back surface of the wafer or the like are pinned by the dissolved oxygen, and therefore, the extension of dislocations can be suppressed.

  In addition, since the DZ layer becomes supersaturated with interstitial silicon due to the introduction of interstitial silicon, in the heat treatment after the rapid heating / cooling heat treatment (for example, heat treatment in the device process), dissolved oxygen is present in the DZ layer. Reprecipitation can be prevented.

  In the silicon wafer manufacturing method according to the present invention, COP may remain near the surface of the wafer. FIG. 4 is a conceptual diagram for explaining the mechanism in which the COP in the vicinity of the wafer surface remains in the mechanism for reducing the LSTD density according to the present invention.

  When rapid heating / cooling heat treatment is performed in an oxidizing gas atmosphere having a high oxygen partial pressure of 20% or more as in the present invention, the vicinity of the surface of the wafer is in an oxygen supersaturated state. Therefore, oxygen contained in the inner wall oxide film formed on the inner wall of the COP generated near the surface is hardly dissolved in the wafer. Therefore, the COP inner wall oxide film formed in the vicinity of the wafer surface remains, and the introduced i-Si is not buried inside the COP in which the remaining inner wall oxide film is formed. In some cases, the COP cannot be eliminated (FIGS. 4A to 4C).

  In such a case, a high-quality silicon wafer with few grown-in defects can be easily manufactured by removing the COP remaining in the vicinity of the surface of the wafer by polishing.

  Note that this polishing may be performed only by the finish polishing that is a well-known technique, or may be performed by using a combination of secondary polishing and finish polishing that are well-known techniques.

The maximum temperature T ₁ is more preferably 1350 ° C. or higher and 1380 ° C. or lower.

  By providing such a configuration, it is possible to further improve the ability to reduce Grown-in defects while suppressing the occurrence of slip during the rapid heating / cooling heat treatment. Details will be described later in Examples.

The film thickness variation in the wafer surface of the silicon oxide film formed by the rapid heating / cooling heat treatment is such that the maximum value of the film thickness is t _OX max, the minimum value of the film thickness is t _OX min, When the average value is t _OX ave, the ratio calculated by (t _OX max−t _OX min) / (t _OX ave) is preferably within 1.5%.

  By providing such a configuration, it is possible to further suppress the occurrence of slip during the rapid heating / cooling heat treatment.

  The film thickness ratio can be calculated by measuring the film thickness of a silicon oxide film formed on the surface of a silicon wafer subjected to rapid heating / cooling heat treatment using an ellipsometry method. Further, the control of the ratio of the film thickness will be described with reference to the RTP apparatus 10 shown in FIG. 1. For example, the control of the light emission intensity) and the flow rate of the atmospheric gas.

  Aggregates of supersaturated vacancy-type point defects existing in at least the device active region of the silicon wafer before the rapid heating / cooling heat treatment have a maximum size in terms of the diameter of a sphere having the same volume as the aggregate. It is preferable that it is 180 nm or less.

  By providing such a configuration, aggregates of supersaturated hole-type point defects generated by the rapid heating / cooling heat treatment can be surely eliminated.

  In order to reduce the supersaturated vacancy-type point defect aggregates generated during the growth of the silicon single crystal ingot to be equal to or smaller than the above-described size, it can be achieved by performing nitrogen doping treatment. Such nitrogen doping treatment can be performed, for example, by filling together a silicon wafer on which a silicon nitride film is formed when filling a quartz crucible with polycrystalline silicon.

  However, such nitrogen doping treatment tends to gradually increase the doping amount of nitrogen from the upper part to the lower part of the straight body part of the grown silicon single crystal ingot. In such a case, the size and density of the grown-in defects in the axial direction of the grown silicon single crystal ingot are not uniform. As a result, the size and density of the grown-in defects vary in the axial direction of the silicon single crystal ingot. Accordingly, the quality of the silicon wafer obtained by processing the silicon single crystal ingot and performing the rapid heating / cooling heat treatment described above varies greatly between lots, that is, within the silicon single crystal ingot.

  In addition, since the ability to reduce the grown-in defects in the rapid heating / rapid cooling heat treatment according to the present invention has been improved, supersaturated vacancies can be obtained without performing such nitrogen doping treatment, that is, by nitrogen doping treatment. Even if the agglomerates of mold point defects are not reduced, these can be reduced by rapid heating / cooling heat treatment, which is a subsequent process.

  Therefore, in the method for producing a silicon wafer according to the present invention having the rapid heating / cooling heat treatment described above, even if the silicon single crystal ingot is grown with nitrogen non-doping, the supersaturation generated during the growth of the silicon single crystal is not caused. Agglomerates of vacancy-type point defects can be reduced, and variation in the size and density of grown-in defects in the axial direction of the silicon single crystal ingot can also be stabilized.

  In addition, by growing silicon single crystal ingots with nitrogen non-doping, supersaturated vacancy type point defects with a size that is difficult to eliminate by the rapid heating / cooling heat treatment described above (those exceeding 180 nm at the maximum) When aggregates are generated, it is performed in combination with nitrogen non-doping and high-speed pulling to reduce the size of supersaturated vacancy-type point defect aggregates to the extent that they can be eliminated by the rapid heating / cooling heat treatment described above. can do. The high speed pulling here means an average of 1.2 mm / min or more when manufacturing a silicon wafer having a diameter of 300 mm, and an average of 1.8 mm / min when manufacturing a silicon wafer having a diameter of 200 mm. It means more than min.

It is preferred dissolved oxygen concentration in the silicon single crystal ingot is in the range of 5 × ¹⁰ 17 atoms / cm ³ or more 1.3 × ¹⁰ 18 atoms / cm ³ or less.
In addition, the solid solution oxygen concentration in this specification is a value obtained from a conversion factor based on the 1970-1979 edition Old ASTM standard.

  At present, with the purpose of correcting the solid solution limit surface roughness of nitrogen as described above, the LSTD density reduction rate in the rapid heating / cooling heat treatment is relatively large due to the provision of such a configuration. A silicon wafer having a high material density can be obtained.

  Next, the effects of the present invention will be specifically described by way of examples, but the present invention is not limited to the following examples.

Example 1
By CZ method, P-type, crystal plane orientation (001), dissolved oxygen concentration [Oi] 1.2 × 10 ¹⁸ atoms / cm ³ (calculated from conversion factor by Old ASTM), resistance 23-25 Ω / cm A silicon single crystal ingot was produced.

  At this time, nitrogen doping treatment is performed by introducing a silicon wafer coated with a silicon nitride film, the pulling speed is adjusted to 1.2 mm / min on average, and dislocation clusters are not generated during the growth of the silicon single crystal. The pulling-up speed V and the temperature gradient G in the crystal axis direction at 1300 ° C. were controlled, and the pulling was performed while controlling V / G.

  Next, the obtained silicon single crystal ingot was cut into a wafer shape with a wire saw and subjected to bevel processing, lapping, etching, and polishing, and a double-side polished silicon wafer having a diameter of 300 mm was produced.

Next, several samples of the produced silicon wafer were sampled in the same lot, and the grown-in defect on the device surface of the sampled silicon wafer was determined as AFM.
Observation was carried out with an atomic force microscope (Atomic Force Microscope). The maximum value in terms of the diameter of a sphere having the same volume as the observed Grown-in defect was measured. As a result, the maximum value of the COP size measured in this example was 100 nm.

Next, using the RTP apparatus 10 as shown in FIG. 1, the silicon wafer produced was subjected to rapid heating / cooling heat treatment. In the present embodiment, among the temperature processes shown in FIG. 2, T ₀ : 500 ° C., ΔTu: 75 ° C./sec, t: 15 sec, ΔTd: 25 ° C./sec are common conditions, and T ₁ is 1250 ° C. to 1400 ° C. And the atmospheric gas is a mixed gas of Ar and oxygen, and the partial pressure of oxygen gas in this mixed gas is 0% (Ar 100% gas), 10%, 20%, 30%, 40%, 100 % (Oxygen 100% gas) and rapid heating / cooling heat treatment was performed, respectively. The temperature at this time is an average of nine points in the wafer surface in the wafer radial direction below the wafer W measured by a plurality of radiation thermometers 50 embedded in the stage 40b of the wafer support 40 as shown in FIG. Temperature.

  Next, the LSTD density and the slip length were measured on the silicon wafer subjected to the rapid heating / cooling heat treatment. The LSTD density was measured by using MO601 manufactured by Raytex Co., Ltd., adjusting the laser wavelength to 680 nm and the penetration depth to 5 μm. The slip length was measured by X-ray topography (XRT300, 400 diffraction) manufactured by Rigaku Corporation.

FIG. 5 is a result diagram showing the LSTD density and the occurrence state of the total slip length under each condition after the rapid heating / cooling heat treatment in Example 1. The horizontal axis is the RTP treatment temperature (° C.), the first vertical axis (left side of the vertical axis) is LSTD density (pieces / cm ^2), a second vertical axis (right side of the vertical axis) is the total slip length (Mm). The total slip length here refers to the total value of the lengths of all the slips obtained by measuring the entire wafer by X-ray topography, measuring the length of each of the plurality of slips confirmed on the entire wafer. In addition, each point plotted in FIG. 5 is: ◆ is oxygen partial pressure 0%, □ is oxygen partial pressure 10%, Δ is oxygen partial pressure 20%, ○ is oxygen partial pressure 30%, and ▲ is oxygen partial pressure 40 % And ■ are plot data representing the LSTD density with respect to the RTP treatment temperature under each atmospheric gas condition with an oxygen partial pressure of 100%, and x is a plot data of the total slip length generated when the oxygen partial pressure is 20%. It is.

  As shown in FIG. 5, when the oxygen partial pressure is 20% or more, it can be confirmed that the LSTD density is significantly reduced as compared with the case where the oxygen partial pressure is 10% or less. In addition, it is confirmed that the LSTD density is greatly reduced at 1300 ° C. or higher at the RTP processing temperature, and that the LSTD density is stabilized at a considerably low density at 1350 ° C. or higher. Further, the total slip length tends to increase slightly up to 1380 ° C., but it can be confirmed that the total slip length greatly increases when it exceeds 1380 ° C. The plot data of the total slip length is obtained when the oxygen partial pressure is 20%. However, since the same tendency was observed under other conditions, the other conditions are omitted in FIG. .

  From the above, as shown in FIG. 5, the conditions under which the reduction in the LSTD density is large and the effect of suppressing the occurrence of slip are as follows: the oxygen partial pressure is 20% or more and 100% or less, and the RTP treatment temperature is It can be confirmed that the temperature is 1300 ° C. or higher and 1380 ° C. or lower, preferably 1350 ° C. or higher and 1380 ° C. or lower.

(Example 2)
By CZ method, P-type, crystal plane orientation (001), dissolved oxygen concentration [Oi] 1.0 × 10 ¹⁸ atoms / cm ³ (calculated from conversion factor by Old ASTM), resistance 28-30 Ω / cm There were others, and a silicon wafer having a diameter of 300 mm polished on both sides was produced in the same manner as in Example 1.

Next, several samples of the produced silicon wafer were sampled in the same lot, and the grown-in defect on the device surface of the sampled silicon wafer was determined as AFM.
Observation was carried out with an atomic force microscope (Atomic Force Microscope). The maximum value in terms of the diameter of a sphere having the same volume as the observed Grown-in defect was measured. As a result, the maximum value of the COP size measured in this example was 100 nm.

Next, using the RTP apparatus 10 as shown in FIG. 1, the silicon wafer produced was subjected to rapid heating / cooling heat treatment. In the present embodiment, among the temperature processes shown in FIG. 2, T ₀ : 500 ° C., ΔTu: 75 ° C./sec, t: 15 sec, ΔTd: 25 ° C./sec, atmospheric gas: oxygen gas 100% are common conditions, the _{T 1, 1300 ℃, 1350 ℃} , in three conditions of 1380 ° C., after rapid thermal heat treatment, as the film thickness variation of the oxide film formed on the wafer surface changes, adjusting the processing conditions for each sample Then, rapid heating / cooling heat treatment was performed.

Next, the thickness variation and the slip length of the oxide film formed by the rapid heating / rapid cooling heat treatment were measured on the silicon wafer subjected to the rapid heating / cooling heat treatment. The film thickness variation is performed by the ellipsometry method using AutoELIII made by Rudolf Research, and the measurement position is 40 mm from the wafer center (distance 0 mm) and from the wafer center toward the radial direction of the wafer, as shown in FIG. A total of nine points of 75 mm, 110 mm, and 145 mm are measured, and a maximum value t _OX max, a minimum value t _OX min, and an average value t _OX ave of the nine-point measurement are calculated, and (t _OX max−t _OX The ratio calculated by (min) / (t _OX ave), that is, the film thickness variation was calculated. The slip length was measured by X-ray tomography manufactured by Rigaku Corporation in the same manner as in Example 1.

  FIG. 7 is a result diagram showing the occurrence of slip length with respect to film thickness variation after the rapid heating / cooling heat treatment according to the second embodiment. The horizontal axis represents the thickness variation (%) of the oxide film, and the vertical axis represents the total slip length (mm) at that time. In addition, each point plotted in FIG. 7 is 1300 ° C. for □, 1350 ° C. for □, and 1380 ° C. for Δ.

  As shown in FIG. 7, it can be confirmed that the total slip length tends to increase as the film thickness variation in the wafer surface increases. Moreover, when temperature rises, the tendency for total slip length to also increase can be confirmed. In addition, as shown in FIG. 7, when the film thickness variation is 1.5% or less, the occurrence of the total slip length is slight and it can be confirmed that it is more preferable.

(Example 3)
According to CZ method, P type, crystal plane orientation (001), resistance 23 to 25 Ω / cm, and solid solution oxygen concentration is 0.3 × 10 ¹⁸ atoms / cm ^{3 to} 1.5 × 10 ¹⁸ atoms / cm Each of the silicon single crystal ingots shaken in the range of ³ was prepared, and the other methods were the same as in Example 1 to prepare a silicon wafer having a diameter of 300 mm that was polished on both sides with different solid solution oxygen concentrations.

  The solid solution oxygen concentration at this time is a value measured by FTIR (Fourier Transform Infrared Spectrometer: QS-612 manufactured by Accent Optical Technology).

  Next, several silicon wafers were sampled in the same lot, and the grown-in defects on the device surface of the sampled silicon wafers were observed with an AFM (Atomic Force Microscope). The maximum value in terms of the diameter of a sphere having the same volume as the observed Grown-in defect was measured. As a result, the maximum value of the COP size measured in this example was 100 nm.

Next, using the RTP apparatus 10 as shown in FIG. 1, the silicon wafer produced was subjected to rapid heating / cooling heat treatment. In the present embodiment, among the temperature processes shown in FIG. 2, T ₀ : 500 ° C., ΔTu: 75 ° C./sec, t: 15 sec, ΔTd: 25 ° C./sec, atmospheric gas: oxygen gas 100% are common conditions, T ₁ and 1300 ° C., in two conditions of 1350 ° C., was rapid thermal heat treatment solution oxygen concentration is about each of the different samples. In addition, the LSTD density of the surface of the silicon wafer before the rapid heating / cooling heat treatment is measured in advance, and the silicon wafer is subjected to a numbering process so that it can be handled one-to-one after the rapid heating / cooling heat treatment. A rapid cooling heat treatment was performed.

  Next, the LSTD density was measured for the silicon wafer subjected to the rapid heating / cooling heat treatment, and the decrease rate (LSTD after the rapid heating / cooling heat treatment was determined from the change in the LSTD density before and after the rapid heating / cooling heat treatment. Density / LSTD density before rapid heating / cooling heat treatment) was calculated. Moreover, the oxygen precipitate density was measured. As in Example 1, the LSTD density before and after the rapid heating / cooling heat treatment was measured by using MO601 manufactured by Raytex Co., Ltd., adjusting the laser wavelength to 680 nm and the penetration depth to 5 μm. The oxygen precipitate density was measured by IR tomography (MO411 manufactured by Raytex). Prior to the IR tomography sample evaluation, after heat treatment at 800 ° C. for 4 hours in an oxygen 100% gas atmosphere as an oxygen precipitation heat treatment, at 1000 ° C. in the same gas atmosphere (oxygen 100% gas). Heat treatment was performed for 16 hours.

  FIG. 8 is a result chart showing the LSTD density reduction rate and the oxygen precipitate density with respect to the solid solution oxygen concentration of the silicon wafer according to Example 3.

In FIG. 8, the horizontal axis is the solid solution oxygen concentration (× 10 ¹⁸ atoms / cm ³ ), the first vertical axis (the vertical axis on the left side of the paper) is the LSTD density reduction rate (%), and the second vertical axis (the paper surface). The right vertical axis) is the oxygen precipitate density (/ cm ³ ). Each plotted point in FIG. 8 is a plot corresponding to the LSTD density reduction rate for each solute oxygen concentration at 1300 ° C., and ■ is the LSTD density reduction rate for each solute oxygen concentration at 1350 ° C. Is a plot corresponding to the oxygen precipitate density for each solute oxygen concentration at 1300 ° C., and □ is a plot corresponding to the oxygen precipitate density for each solute oxygen concentration at 1350 ° C. It is.

As shown in FIG. 8, it can be confirmed that the LSTD density reduction rate tends to decrease as the solute oxygen concentration of the silicon wafer increases. In particular, when the concentration of dissolved oxygen exceeds 1.3 × 10 ¹⁸ atoms / cm ³ , the tendency is remarkable. This is because the inner wall oxide film of the COP is difficult to disappear because of the large amount of oxygen in the silicon wafer. However, when the concentration of dissolved oxygen in the silicon wafer is small, the oxygen precipitation nuclei are reduced, and it is considered that the precipitation density after the rapid heating / cooling heat treatment or the oxygen precipitation heat treatment decreases. In particular, as shown in FIG. 8, the tendency is remarkable when the dissolved oxygen concentration is less than 0.5 × 10 ¹⁸ atoms / cm ³ .

Further, as shown in FIG. 8, when the concentration of dissolved oxygen in the silicon wafer increases, the density of oxygen precipitates tends to increase, and the concentration of dissolved oxygen is 0.7 × 10 ¹⁸ atoms / cm ³ or more. The increasing trend is made uniform. Accordingly, from the viewpoint of oxygen precipitate density, the solid solution oxygen concentration of the silicon wafer is more preferably 0.7 × 10 ¹⁸ atoms / cm ³ or more.

From the above, in the range where the LSTD density reduction rate is relatively large and the oxygen precipitate density is high, the solid solution oxygen concentration of the silicon wafer is 0.5 × 10 ¹⁸ atoms / cm ³ or more 1.3 as shown in FIG. The range is not more than × 10 ¹⁸ atoms / cm ³ , more preferably not less than 0.7 × 10 ¹⁸ atoms / cm ^{3 and not} more than 1.3 × 10 ¹⁸ atoms / cm ³ . By setting it as this range, it can be seen that the LSTD density reduction rate is relatively large and the oxygen precipitate density is high, which is more preferable.

Example 4
In Example 1, each sample subjected to rapid heating / cooling heat treatment at an oxygen partial pressure of 20% to 100% and RTP treatment temperatures of 1300 ° C., 1330 ° C., 1350 ° C. and 1380 ° C. will be described in Example 3. Oxygen precipitation heat treatment (heat treatment at 800 ° C. for 4 hours in a 100% oxygen gas atmosphere followed by heat treatment at 1000 ° C. for 16 hours in the same gas atmosphere (oxygen 100% gas)) and then obtained. The sample was evaluated for oxygen precipitate density, and this was designated as Example 4. The oxygen precipitate density was evaluated by BMD manufactured by Raytex.
An analyzer system MO411 was used in the region from the wafer surface to a depth of 50 μm. This oxygen precipitation heat treatment was assumed to be a heat treatment in a so-called device process.

  As a comparative example in Example 4, in Example 1, the oxygen partial pressure is 0% and 10%, and the RTP treatment temperatures are 1300 ° C, 1330 ° C, 1350 ° C, and 1380 ° C, and rapid heating and rapid cooling are performed. The sample subjected to the heat treatment was also subjected to the same oxygen precipitation heat treatment to evaluate the oxygen precipitate density.

  As a result, it was found that the lower the oxygen partial pressure and the lower the RTP treatment temperature, the higher the oxygen precipitate density. That is, the sample taken as a comparative example had a higher oxygen precipitate density than that of Example 4. This is considered to be because the higher the oxygen partial pressure and the higher the RTP treatment temperature, the higher the interstitial silicon concentration and the higher the degree of supersaturation, thereby suppressing oxygen precipitation due to oxygen precipitation heat treatment. .

  From the above results, the silicon wafer manufactured using the method for manufacturing a silicon wafer according to the present invention has dissolved oxygen in the DZ layer in the heat treatment after the rapid heating / rapid cooling heat treatment (for example, heat treatment in the device process). It is thought that reprecipitation can be prevented.

It is sectional drawing which shows the outline | summary of an example of the RTP apparatus used for the manufacturing method of the silicon wafer of this invention. It is explanatory drawing which shows an example of the temperature process in rapid heating / rapid cooling heat processing. It is a conceptual diagram for demonstrating the mechanism by which the LSTD density concerning this invention is reduced. It is a conceptual diagram for demonstrating the mechanism in which COP of the surface vicinity of a wafer remains in the mechanism in which the LSTD density concerning this invention is reduced. It is a result figure showing the generation | occurrence | production condition of the LSTD density and each slip length in each condition after the rapid heating and rapid cooling heat processing in Example 1. FIG. It is a conceptual diagram for demonstrating the measurement point at the time of calculating the film thickness variation of the oxide film in Example 2. FIG. It is a result figure showing the generation | occurrence | production state of the slip length with respect to the film thickness variation after the rapid heating / rapid cooling heat processing concerning Example 2. FIG. It is a result figure showing the LSTD density decreasing rate with respect to the solid solution oxygen concentration of the silicon wafer concerning Example 3, and an oxygen precipitate density.

Explanation of symbols

10 RTP device 20 Reaction tube 30 Lamp 40 Wafer support

Claims (8)

  Maximum temperature reached 1300 ° C or higher and 1380 ° C or lower in an oxidizing gas atmosphere where the partial pressure of oxygen gas is 20% or more and 100% or less with respect to a silicon wafer manufactured from a silicon single crystal ingot grown by the Czochralski method A method of manufacturing a silicon wafer, characterized by performing a rapid heating / cooling heat treatment.   The method for producing a silicon wafer according to claim 1, wherein the maximum temperature reached is 1350 ° C. or higher and 1380 ° C. or lower. The film thickness variation in the wafer surface of the silicon oxide film formed by the rapid heating / cooling heat treatment is such that the maximum value of the film thickness is t _OX max, the minimum value of the film thickness is t _OX min, The ratio calculated by (t _OX max-t _OX min) / (t _OX ave) when the average value is t _OX ave is 1.5% or less. Silicon wafer manufacturing method.   Aggregates of supersaturated vacancy-type point defects existing in at least the device active region of the silicon wafer before the rapid heating / cooling heat treatment have a maximum size in terms of the diameter of a sphere having the same volume as the aggregate. The method for producing a silicon wafer according to any one of claims 1 to 3, wherein the thickness is 180 nm or less.   The method for producing a silicon wafer according to claim 1, wherein the silicon single crystal ingot is grown by nitrogen non-doping. The solid solution oxygen concentration in the silicon single crystal ingot is in the range of 5 × 10 ¹⁷ atoms / cm ³ or more and 1.3 × 10 ¹⁸ atoms / cm ³ or less. 2. A method for producing a silicon wafer according to item 1.   The method of manufacturing a silicon wafer according to claim 1, wherein a surface of the silicon wafer subjected to the rapid heating / cooling heat treatment is polished. By applying the rapid heating / rapid cooling heat treatment, agglomerates of supersaturated vacancy-type point defects and oxygen precipitates existing in at least the device active region of the silicon wafer are eliminated to form a DZ layer, and the DZ layer is formed. 8. The method for producing a silicon wafer according to claim 1, wherein solid solution oxygen is introduced into the layer.