JP2008066357A - Silicon single crystal wafer and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silicon single crystal wafer that is superior in TZDB (Time Zero Dielectric Breakdown) characteristics and TDDB (Time Dependent Dielectric Breakdown) characteristics in a wafer surface layer area as a device fabrication area, and is less varied in BMD density in the wafer surface, and also to provide a method of manufacturing the same. <P>SOLUTION: The silicon single crystal wafer grown by CZ method is doped with nitrogen, and its entire surface is N- area. The non-defective rate of those with TZDB and TDDB characteristics is 90% or more, and the maximum value of BMD density in the wafer surface after gettering heat treatment or device heating treatment is 50 times or less its minimum value. When the silicon single crystal wafer is grown by the CZ method, it is pulled up under such a condition that the crystal entire surface becomes an N- area while it is being doped with nitrogen with a concentration of ≥5×10<SP>11</SP>atoms/cm<SP>3</SP>and ≤3×10<SP>13</SP>atoms/cm<SP>3</SP>, and oxygen with a concentration of ≥8 ppma and <13 ppma (JEIDA), so as to manufacture the silicon single crystal wafer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a silicon single crystal wafer used as a substrate for a semiconductor device such as a memory or a CPU, and a method for manufacturing the silicon single crystal wafer, and in particular, a silicon single crystal wafer having a defect-free surface layer used in the most advanced field. And a method for producing a silicon single crystal wafer.

  In recent years, with the miniaturization of elements accompanying higher integration of semiconductor circuits such as DRAMs, quality requirements for silicon single crystals produced by the Czochralski method (hereinafter sometimes abbreviated as CZ method) as the substrate Is getting higher. In particular, there are defects due to single crystal growth that degrade oxide breakdown voltage characteristics and device characteristics called Grown-in defects such as FPD, LSTD, and COP, and reduction in density and size is regarded as important. Yes.

  In describing these defects, first, a vacancy-type point defect called vacancy (hereinafter sometimes abbreviated as V) incorporated in a silicon single crystal, and interstitial-silicon (interstitial-Si, hereinafter). What is generally known is a factor that determines the concentration of each interstitial silicon point defect called “I” (sometimes abbreviated as “I”).

  In a silicon single crystal, the V-region is a vacancy, that is, a region having many recesses and holes generated due to a shortage of silicon atoms, and the I-region is generated by the presence of extra silicon atoms. A neutral region (Neutral region, hereinafter referred to as an N-region) that has a shortage of atoms and no (or few) atoms between the V-region and the I-region. May be abbreviated). The grow-in defects (FPD, LSTD, COP, etc.) occur only when V or I is in a supersaturated state. It has been found that it does not exist as a defect.

  It is known that the concentration of both point defects is determined from the relationship between the crystal pulling rate (growth rate) in the CZ method and the temperature gradient G in the vicinity of the solid-liquid interface in the crystal. In addition, in the N-region between the V-region and the I-region, the presence of a ring-like defect called OSF (Oxidation Induced Stacking Fault) has been confirmed.

  When these defects due to crystal growth are classified, depending on the diameter of the grown crystal, for example, when the growth rate is relatively high, such as about 0.6 mm / min or more, void-type point defects are aggregated. Grown-in defects such as FPD, LSTD, and COP, which are considered to be present, are present at high density throughout the crystal diameter direction, and a region where these defects exist is called a V-rich region. Further, when the growth rate is 0.6 mm / min or less, the OSF ring described above is generated from the periphery of the crystal as the growth rate is reduced, and L / D that is considered to be caused by a dislocation loop outside the ring. Defects (Large Dislocation: abbreviations for interstitial dislocation loops, LSEPD, LFPD, etc.) are present at a low density, and a region where these defects are present is called an I-rich region. Furthermore, when the growth rate is lowered to about 0.4 mm / min or less, the OSF ring aggregates and disappears at the center of the wafer, and the entire surface becomes an I-rich region.

Further, an N-region in which there is no vacancy-induced FPD, LSTD, COP, dislocation loop-induced LSEPD, LFPD, or even OSF outside the OSF ring between the V-rich region and the I-rich region recently. The presence of has been discovered. This region is outside the OSF ring, and when oxygen precipitation heat treatment is performed and the contrast of the precipitation is confirmed by X-ray observation or the like, there is almost no oxygen precipitation and is so rich that LSEPD and LFPD are formed. It is not the I-rich region side.
Further, it is confirmed that there are no defects caused by vacancies or dislocation loops inside the OSF ring, and there is an N-region in which no OSF exists.

In the normal method, these N-regions exist obliquely with respect to the growth axis direction when the growth rate is lowered, and therefore exist only in a part of the wafer plane.
In this N-region, in the Boronkov theory (Non-Patent Document 1), the parameter F / G, which is the ratio of the pulling rate (F) and the crystal-liquid-liquid interface axial temperature gradient (G), determines the total concentration of point defects. It is said that it will be decided. Considering this, since the pulling speed should be constant in the plane, since G has a distribution in the plane, for example, at a certain pulling speed, the center is the V-rich region and the N-region is sandwiched around it. Only crystals that would be in the I-rich region were obtained.

  Therefore, recently, when the distribution of G in the plane has been improved, the N-region that has existed only at an angle, for example, when the pulling-up speed F is gradually lowered, the N-region is lateralized at a certain pulling speed. Crystals spread over the entire surface can be manufactured. Further, in order to expand the crystal of the entire N-region in the length direction, it can be achieved to some extent if the pulling rate is maintained while the N-region is expanded laterally. Also, considering that G changes as the crystal grows, if it is corrected and the pulling speed is adjusted so that F / G is constant, the entire surface N- The area crystal can be enlarged.

  However, such a wafer is characterized in that oxygen precipitation is likely to occur on the V-rich side and oxygen precipitation is unlikely to occur on the I-rich side even in the N region where no defect is detected. Therefore, when a wafer is cut out from such a crystal, a portion where oxygen precipitation is likely to occur and a portion where it is difficult to occur are mixed in the wafer surface, and the density of BMD observed after device heat treatment or the like varies greatly. There was a problem.

In addition, when the N-region, which is an extremely low defect region as described above, is to be manufactured over the entire crystal, the pulling rate control range to be the N-region is narrow, and the in-furnace structure of the crystal growth apparatus (hot Zone (HZ) is also limited, and it has been difficult to stably expand the N-region in the axial direction of the crystal.
Therefore, the yield of manufacturing the crystal which is the entire N-region is low, and it is difficult to guarantee the quality of the crystal.

  On the other hand, Patent Document 1 shows that by doping nitrogen, the N-region is widened and easily controlled, and an N-region can be easily obtained. -A method for improving the controllability of the region is disclosed. In addition, in the wafers cut out from the N-region obtained in this way, it is reported that the yield rate of TZDB (Time Zero Dielectric Breakdown) and TDDB (Time Dependent Dielectric Breakdown) of the oxide film breakdown voltage characteristics is high. As a result of further trials by the present inventors, it has been found that even if TZDB is actually good, a TDDB defect may occur.

  In addition, even in the annealed wafer disclosed in Patent Document 2 and the silicon wafer disclosed in Patent Document 3, a defect may occur in the TDDB characteristics.

JP 2000-53497 A Japanese Patent Laid-Open No. 2005-159028 JP-A-11-195565 V. V. Voronkov; Journal of Crystal Growth, 59 (1982) 625-643.

  The present invention has been made in view of the above problems, and is a silicon single crystal wafer having excellent TZDB characteristics and TDDB characteristics of a wafer surface layer region, which is a device manufacturing region, and a small variation in BMD density in the wafer surface. An object of the present invention is to provide a method for producing a silicon single crystal wafer. In particular, an object is to provide a silicon single crystal wafer having a uniform and sufficient BMD formed in the wafer bulk region and having an excellent IG capability.

  In order to achieve the above object, the present invention is a silicon single crystal wafer grown by the Czochralski method, which is doped with nitrogen and has an entire N-region, and has TZDB characteristics and TDDB characteristics. The non-defective rate is 90% or more, and the ratio (maximum value / minimum value) between the maximum value and the minimum value of BMD density in the wafer surface after gettering heat treatment or device heat treatment is 50 times or less. A silicon single crystal wafer is provided.

As described above, the silicon single crystal wafer of the present invention is doped with nitrogen so that the entire surface of the wafer is in the N-region, the non-defective rate of both the TZDB characteristic and the TDDB characteristic is 90% or more, and the gettering is performed. Since the ratio (maximum value / minimum value) of the maximum and minimum values of BMD density in the wafer surface after heat treatment or device heat treatment is 50 times or less, there is no crystal defect in the wafer surface layer region, which is the device fabrication region, and oxidation Excellent film breakdown voltage characteristics, and even in the N-region, variation in BMD density in the wafer surface after gettering heat treatment or device heat treatment is small and uniform, and effectively prevents wafer deformation due to heat treatment. This is a silicon single crystal wafer that can be used.
Here, the non-defective product ratio of the TZDB characteristic and the TDDB characteristic indicates the non-defective product ratio of the cells formed in the wafer, and is hereinafter simply expressed as the non-defective product ratio of the TZDB characteristic and the TDDB characteristic.

The silicon single crystal wafer preferably has an oxygen concentration of 8 ppma to less than 13 ppma (JEIDA).
Thus, if the oxygen concentration is 8 ppma or more, the BMD inside the wafer can be made to have a sufficient density by heat treatment such as a device manufacturing process, and a silicon single crystal wafer having gettering ability can be obtained. If it is less than 13 ppma (JEIDA), not only the TZDB characteristics but also the TDDB characteristics can be more than 90% acceptable.

At this time, it is desirable that the doped nitrogen concentration is 5 × 10 ¹¹ atoms / cm ³ or more and 3 × 10 ¹³ atoms / cm ³ or less (Claim 3).
Thus, if the doped nitrogen concentration is 5 × 10 ¹¹ atoms / cm ³ or more, the precipitation of oxygen is promoted in a heat treatment such as a device manufacturing process, and the BMD inside the wafer can be made to have a sufficient density. It is possible to obtain a silicon single crystal wafer having a gettering capability, and if it is 3 × 10 ¹³ atoms / cm ³ or less, not only the TZDB characteristic but also the TDDB characteristic has a non-defective rate of 90%. % Or more.

Furthermore, it is preferable that the BMD density inside the wafer after the gettering heat treatment or device heat treatment is 1 × 10 ⁷ pieces / cm ³ or more.
As described above, when the BMD density inside the wafer after the gettering heat treatment or device heat treatment is 1 × 10 ⁷ pieces / cm ³ or more, a silicon single body having a sufficient BMD density and having a high gettering ability is obtained. It can be a crystal wafer.

  Here, gettering heat treatment is a general term for heat treatment performed after processing a grown silicon single crystal rod into a wafer and before entering a device process, and device heat treatment is a gettering heat treatment. Regardless of the presence or absence of other treatments, this is a general term for heat treatment performed in the device manufacturing process or simulation heat treatment that is simplified.

Further, the silicon single crystal wafer may be one in which oxygen precipitates on the surface layer of the wafer are dissolved by heat treatment.
In the nitrogen-doped crystal, nitrogen has an effect of promoting oxygen precipitation by acting with vacancy. For this reason, oxygen precipitation nuclei are easily formed during crystal growth, and oxygen precipitates may be formed depending on conditions. If this oxygen precipitate appears on the surface layer when the wafer is cut out from the crystal, the electrical characteristics may be deteriorated. For this reason, by applying heat treatment, oxygen precipitates on the surface layer can be dissolved, and a wafer with higher quality can be obtained.

Further, according to the present invention, when growing a silicon single crystal by the Czochralski method, nitrogen having a concentration of 5 × 10 ¹¹ atoms / cm ³ or more and 3 × 10 ¹³ atoms / cm ³ or less, and 8 ppma or more and less than 13 ppma (JEIDA A method for producing a silicon single crystal wafer is provided, wherein the entire surface of the crystal is pulled up in an N-region while doping oxygen at a concentration of (5).

Thus, when growing a silicon single crystal by the Czochralski method, nitrogen having a concentration of 5 × 10 ¹¹ atoms / cm ³ or more and 3 × 10 ¹³ atoms / cm ³ or less, and 8 ppma or more and less than 13 ppma (JEIDA). If the entire surface of the crystal is pulled up in an N-region while doping oxygen at a concentration, a silicon single crystal wafer obtained from this silicon single crystal can have the nitrogen concentration and oxygen concentration. Thereby, after gettering heat treatment or device heat treatment, a silicon single crystal wafer having a high-density BMD inside the wafer and having sufficient gettering ability can be obtained. Furthermore, it is possible to obtain a silicon single crystal wafer having no crystal defects in the surface layer region, excellent TZDB characteristics and TDDB characteristics, and having a uniform BMD density variation within the wafer surface, so that deformation is suppressed. Is possible.

Further, the silicon single crystal wafer obtained by the above method can be subjected to heat treatment at 1000 to 1300 ° C. for 10 seconds to 1 hour to dissolve oxygen precipitates on the surface layer of the wafer.
By applying such heat treatment to the wafer and dissolving oxygen precipitates on the wafer surface layer, the electrical characteristics are hardly deteriorated and a higher quality wafer can be obtained.

The heat treatment is preferably performed by a rapid heating / cooling device (claim 8).
As described above, the heat treatment is performed by a rapid heating / rapid cooling apparatus (hereinafter, also referred to as a RTA (Rapid Thermal Anneler) apparatus) in a range of several seconds to several hundred seconds of the wafer surface layer (for example, several nm from the wafer surface). Can be dissolved to a level at which there is no problem with the oxide film breakdown voltage characteristics, so it is effective for a few seconds to several hundreds of seconds without giving the wafer a long and harmful thermal history. Heat treatment can be applied.

  As described above, the silicon single crystal wafer and the silicon single crystal wafer manufacturing method of the present invention are of high quality with both excellent TZDB characteristics and TDDB characteristics, and the entire surface of the wafer is a device active layer in the wafer surface layer region. A silicon single crystal that can easily generate BMD in the interior relatively uniformly while preventing the metal contamination that occurs during device formation, even though it is an N-region that does not generate crystal defects that would degrade device characteristics if present. It is possible to provide a wafer.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.
In recent years, with the miniaturization of elements accompanying higher integration of semiconductor circuits, high quality has been required for silicon single crystal wafers that serve as substrates. Thus, as a low-cost defect-free wafer, a crystal having an N-region on the entire surface is often used.
However, in a wafer cut from the entire N-region crystal obtained by the conventional method, oxygen precipitation is likely to occur on the V-rich side and oxygen precipitation occurs on the I-rich side even in an N-region where no defects are detected. Since it has a feature that it is difficult to perform, there is a problem that the portion where oxygen precipitation is likely to occur and the portion where it is difficult to occur are mixed in the wafer surface, and the density of BMD observed after device heat treatment or the like varies greatly. . Such variations in BMD lead to wafer deformation.

  Further, in the conventional method, the margin for growing the entire N-region crystal is narrow, and the product yield is lowered. Therefore, for example, it has been proposed to dope nitrogen as in Patent Document 1, but when the present inventors investigated the silicon single crystal wafer obtained in Patent Document 1, the TZDB was good. Has also found that TDDB failure may occur. If there is a defect in the TDDB, a problem may occur in a recent state-of-the-art device, which is a problem to be improved.

  Further, in Patent Document 2, a silicon wafer manufactured from a silicon single crystal grown by the CZ method is subjected to heat treatment, and the entire wafer surface is an N-region, and in a region from the wafer surface to at least a depth of 5 μm. The non-defective product rate of the oxide film breakdown voltage characteristic is 95% or more, and the ratio (maximum value / minimum value) between the maximum value and the minimum value of the density of BMD in the wafer is 1 to 10. An annealed wafer and a method for manufacturing the same are disclosed.

  However, in this patent document 2, the evaluation of the oxide film breakdown voltage characteristic is only the TZDB characteristic, the TDDB characteristic is not evaluated, and the non-defective rate of the TDDB characteristic is 90% in the manufacturing method described in the example. % Have not been satisfied by the present inventors.

Patent Document 3 discloses a silicon wafer manufactured through a single crystal growth process using a CZ method and having a low-speed pulling condition in which the OSF ring is generated inside the outer peripheral portion of the pulling crystal or disappears at the central portion. Although a silicon wafer having a nitrogen concentration of 1 × 10 ¹³ atoms / cm ³ or more is disclosed, there is no description regarding TDDB characteristics. And in this patent document 3 and the said patent document 2, even if the TZDB characteristic is favorable, the problem that a defect may generate | occur | produce in a TDDB characteristic was not recognized.

And when the present inventors diligently researched about the silicon single crystal wafer regarding the oxide film breakdown voltage characteristic, especially the TDDB characteristic, as described above, only the conventional methods such as Patent Documents 1 to 3 described above were used. Thus, it has been found that it is not possible to reliably obtain an excellent quality wafer in which the yield ratio of both TZDB characteristics and TDDB characteristics is 90% or more.
Further, if the maximum value / minimum value of the BMD density in the wafer surface is 50 times or less, the variation in the BMD density is sufficiently suppressed, and the deformation of the wafer when subjected to heat treatment or the like is suppressed, warping, etc. Has been found to be able to be effectively prevented, and the present invention has been completed. The inventors of the present invention have found that the range of oxygen concentration and nitrogen concentration to be doped in a silicon single crystal wafer (silicon single crystal) is particularly important.

Hereinafter, the silicon single crystal wafer of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.
FIG. 1 schematically shows an example of the silicon single crystal wafer of the present invention. The silicon single crystal wafer 21 of the present invention shown in FIG. 1 is produced by slicing a silicon single crystal grown by the Czochralski method. This silicon single crystal wafer 21 is doped with nitrogen, and the entire surface of the wafer is an N-region. Further, heat treatment is performed, and oxygen precipitates in the wafer surface layer region 22 are dissolved.

In particular, the silicon single crystal wafer 21 of the present invention desirably has a doped nitrogen concentration of 3 × 10 ¹³ atoms / cm ³ or less. Thus, if the nitrogen concentration is 3 × 10 ¹³ atoms / cm ³ or less, the non-defective rate of both TZDB characteristics and TDDB characteristics can be more reliably 90% or more, and an extremely excellent oxide film Even if a device is fabricated in the wafer surface layer region 22, it becomes a wafer that does not deteriorate the device characteristics.

The nitrogen concentration in the silicon single crystal wafer 21 is desirably 5 × 10 ¹¹ atoms / cm ³ or more. By setting such a concentration range, the BMD density becomes sufficient inside the wafer after gettering heat treatment or device heat treatment, and a silicon single crystal wafer having gettering ability can be obtained.
In particular, the BMD density inside the wafer can be 1 × 10 ⁷ pieces / cm ³ or more. A wafer having such a relatively high density BMD inside can be provided with higher gettering capability.
Also, the oxygen concentration is preferably 8 ppma or more and less than 13 ppma (JEIDA). Similarly to the above, it can have sufficient BMD density and gettering ability after gettering heat treatment, etc., and has TZDB characteristics. And the non-defective product ratio of both the TDDB characteristics is excellent and high quality of 90% or more.

Further, in the silicon single crystal wafer 21 of the present invention shown in FIG. 1, the ratio (maximum value / minimum value) of the density maximum value and the minimum value in the wafer plane is related to the BMD 24 in the bulk region 23 after gettering heat treatment or device heat treatment. Value) is 50 times or less. That is, the BMD 24 is uniformly formed in the wafer surface, and the density variation of the BMD 24 is small. In particular, (maximum value / minimum value) may be 30 times or less. Therefore, in the bulk region, it is possible to obtain an excellent silicon single crystal wafer having a small gettering ability with little variation in the wafer plane.
Furthermore, since the density distribution of the BMD 24 is uniform, deformation such as warpage of the wafer due to this density variation can be effectively prevented.
Here, the BMD can be measured by an infrared tomograph (LST) after performing a heat treatment that simulates a device process of a total of 20 hours centered mainly at 800 ° C. between 750 ° C. and 950 ° C., for example. And the measurement position at this time is an area | region about 50-180 micrometers deep from the surface, for example from the place which entered 10 mm from the edge to a center part by 10 mm space | interval.

In the present invention, the non-defective product ratio of the TZDB is, for example, an oxide film withstand voltage of 8 MV / cm or more under room temperature conditions with an oxide film thickness of 25 nm, a gate area of 8 mm ² and a judgment current value of 1 mA / cm ^3. The ratio of what becomes.
The non-defective product ratio of the TDDB is, for example, a gate oxide film thickness of 25 nm, a gate area of 4 mm ² , a stress current value of 0.01 A / cm ² , and a room temperature of 5 C / cm ² or more under the conditions of room temperature. Indicates the percentage of things.

If oxygen precipitates exist on the wafer surface layer, heat treatment may be applied to the wafer to dissolve the oxygen precipitates on the wafer surface layer.
In this way, if the oxygen precipitates on the surface of the wafer are dissolved, it is possible to obtain a higher quality wafer without deteriorating electrical characteristics.

  As described above, the silicon single crystal wafer 21 of the present invention shown in FIG. 1 has very few crystal defects in the wafer surface layer region 22 and is excellent in both TZDB characteristics and TDDB characteristics. After the device heat treatment, the BMD 24 having a sufficient and uniform density in the bulk region 23 is obtained. For this reason, uniform gettering ability can be provided within the wafer surface, and deformation such as warpage is very unlikely to occur in the wafer.

The silicon single crystal wafer 21 of the present invention as described above can be obtained by, for example, a method for producing a silicon single crystal wafer of the present invention described later. Hereinafter, an example of the manufacturing method will be described in detail.
First, a single crystal pulling apparatus that can be used when pulling a silicon single crystal by the CZ method in the method for producing a silicon single crystal wafer of the present invention will be described.

The single crystal pulling device 18 shown in FIG. 2 includes crucibles 5 and 6 for storing the raw material melt 4, a heater 7 for heating and melting the polycrystalline silicon raw material, and the like provided in the main chamber 1. A pulling mechanism (not shown) for pulling up the grown single crystal is provided on the upper portion of the pulling chamber 2 connected to the main chamber 1.
A pulling wire 16 is unwound from a pulling mechanism attached to the upper part of the pulling chamber 2, and a seed holder and a seed crystal 17 are attached to the tip of the pulling wire 16. Then, the single crystal rod 3 is formed below the seed crystal 17 by winding the pulling wire 16 by a pulling mechanism.

The crucibles 5 and 6 are composed of a quartz crucible 5 on the inside and a graphite crucible 6 for supporting the quartz crucible 5 on the outside. These crucibles 5 and 6 are supported on a crucible rotating shaft that can be rotated and raised by a rotation drive mechanism (not shown) attached to the lower part of the single crystal pulling device 18.
Further, a heat insulating member 8 is provided outside the heater 7 disposed around the crucibles 5 and 6.
Further, a gas inlet 10 and a gas outlet 9 are provided inside the chambers 1 and 2 so that argon gas or the like can be introduced into the chambers 1 and 2 and discharged.

And the cooling cylinder 11 is extended | stretched toward the raw material melt surface from the at least ceiling part of the main chamber 1 so that the single crystal rod 3 being pulled up may be surrounded. A cooling medium is introduced into the cooling cylinder 11 from the cooling medium inlet 12 so that the cooling cylinder 11 can be forcibly cooled.
Further, a cooling auxiliary member 13 and a heat shielding member 14 are provided to cool the single crystal rod 3 by blocking the radiant heat from the heater 7 between the vicinity of the melt surface and the cooling cylinder 11. Furthermore, a protective cover 15 is provided for preventing the raw material melt 4 that may be scattered when the raw material is melted from adhering to the cooling cylinder 11.

Thus, the single crystal pulling apparatus that can be used in the production method of the present invention can be the same as the conventional one.
In addition, a magnet (not shown) can be installed outside the main chamber 1 in the horizontal direction, thereby suppressing the convection of the raw material melt by applying a horizontal or vertical magnetic field to the raw material melt 4. In addition, a single crystal pulling apparatus based on the so-called MCZ method that can achieve stable growth of a single crystal can be used.

FIG. 3 shows an example of an apparatus that can rapidly heat and cool a silicon single crystal wafer obtained by slicing a silicon single crystal obtained by the single crystal pulling apparatus.
The rapid heating / rapid cooling apparatus 32 in FIG. 3 has a chamber 33 made of quartz, and heats the silicon single crystal wafer 31 in the chamber 33. Heating is performed by a heating lamp 34 disposed so as to surround the chamber 33 from above, below, left and right. The heating lamps 34 can control power supplied independently.

On the gas exhaust side, an auto shutter 35 is provided to block the outside air. The auto shutter 35 is provided with a wafer insertion port (not shown) configured to be opened and closed by a gate valve. Further, the auto shutter 35 is provided with a gas exhaust port 30 so that the furnace atmosphere can be adjusted.
The silicon single crystal wafer 31 is disposed on a three-point support portion 37 formed on the quartz tray 36. A quartz buffer 38 is provided on the gas inlet side of the tray 36, and the introduced gas can be prevented from directly hitting the silicon single crystal wafer 31.
The chamber 33 is provided with a temperature measurement special window (not shown), and the pyrometer 39 installed outside the chamber 33 can measure the temperature of the silicon single crystal wafer 31 through the special window.
As described above, the RTA apparatus that can be used in the present invention can be the same as the conventional one.

Hereinafter, an example of the procedure of the method for producing a silicon single crystal wafer of the present invention will be described.
In the production method of the present invention, when growing a silicon single crystal by the Czochralski method, nitrogen having a concentration of 5 × 10 ¹¹ atoms / cm ³ or more and 3 × 10 ¹³ atoms / cm ³ or less, and 8 ppma or more and less than 13 ppma ( JEIDA) is doped with oxygen at a concentration so that the entire surface of the crystal becomes an N-region. First, a method for growing a silicon single crystal whose entire surface is an N-region will be described. If such an entire N-region crystal can be grown, the cut wafer becomes an N-region having a low defect on the entire wafer surface.
As described above, it is necessary to control to a certain F / G in order to obtain an entire N-region crystal. However, even if an attempt is made to expand the N-region over the entire crystal, it is difficult to expand the N-region in the axial direction of the crystal because the control range of the pulling rate that becomes the N-region is narrow. Therefore, as in the present invention, by doping nitrogen, the N-region can be expanded, the single crystal growth conditions can be easily controlled, and the N-region can be easily obtained.

As described above, for example, a single crystal pulling apparatus as shown in FIG. 2 can be used to pull a silicon single crystal in which the entire crystal surface is an N-region and is doped with nitrogen or oxygen. As described above, in the manufacturing method of the present invention, nitrogen is doped at a concentration of 5 × 10 ¹¹ atoms / cm ³ or more and 3 × 10 ¹³ atoms / cm ³ or less, and oxygen is a concentration of 8 ppma or more and less than 13 ppma (JEIDA). Dope with.
As a nitrogen doping method, for example, nitride is put in a quartz crucible in advance, nitride is introduced into a silicon melt, or the atmosphere gas is an atmosphere containing nitrogen, and the amount of nitride or nitrogen gas By adjusting the concentration or the introduction time, the amount of doping in the crystal can be controlled, and doping can be performed within the above range.
Also, for example, the oxygen concentration in the silicon single crystal is adjusted within the above range by adjusting the rotation speed of the crystal when pulling, the rotation speed of the crucible, the temperature distribution in the furnace, the gas pressure in the chamber, etc. And can be doped.
In this case, when growing the crystal by the CZ method, a magnetic field may be applied to the silicon melt.

In this way, when gettering heat treatment or device heat treatment is performed on a wafer cut from this silicon single crystal by doping nitrogen at a concentration of 5 × 10 ¹¹ atoms / cm ³ or more, BMD formed inside the wafer The silicon single crystal serving as a wafer having a sufficient gettering capability can be manufactured at a density of 1 × 10 ⁷ pieces / cm ³ or more.
Further, by doping nitrogen at a concentration of 3 × 10 ¹³ atoms / cm ³ or less, a silicon single crystal wafer having excellent oxide film withstand voltage characteristics in which the yield rate of both TZDB characteristics and TDDB characteristics is 90% or more, respectively. It can be.

Further, by setting the oxygen concentration to 8 ppma or more (JEIDA), the wafer has a BMD density of 1 × 10 ⁷ pieces / cm ³ or more after the gettering heat treatment or the like, and a wafer having sufficient gettering ability. The silicon single crystal wafer can be obtained, and by making it less than 13 ppma (JEIDA), not only the TZDB characteristic but also the TDDB characteristic can be an excellent quality silicon single crystal wafer with a yield rate of 90% or more. Can be manufactured.

Further, by pulling up the silicon single crystal in the above concentration range, a BMD density of 1 × 10 ⁷ pieces / cm ³ or more can be obtained at any location in the wafer surface after gettering heat treatment, etc. A silicon single crystal wafer can be manufactured in which the ratio between the value and the minimum value is 50 times or less, and further 30 times or less. As described above, since the variation in the BMD density in the wafer surface is extremely small, an excellent silicon single crystal wafer having uniform gettering ability can be obtained. It is possible to provide a silicon single crystal wafer that can effectively prevent the occurrence of the above.

In addition, in the silicon single crystal wafer obtained as described above, for example, when oxygen precipitates are present on the surface layer of the crystal, the oxygen on the surface layer of the wafer can be obtained by performing heat treatment at 1000 to 1300 ° C. for 10 seconds to 1 hour. It is good to dissolve the precipitate. By doing so, it is possible to prevent the occurrence of an adverse effect of oxygen precipitates such as abnormal oxygen precipitation on the wafer surface, and to obtain a wafer having very few crystal defects.
Further, since nitrogen is contained in the bulk region of the wafer, the precipitation of oxygen is promoted, and a wafer having sufficient gettering ability can be manufactured.
At this time, the atmosphere in which the heat treatment is performed is preferably argon and / or hydrogen gas. If nitrogen and / or oxygen gas is further contained, surface roughness of the wafer surface can be prevented.

  At this time, it is preferable to dissolve the oxygen precipitates on the extreme surface layer to a level at which there is no problem in the oxide film breakdown voltage characteristics by using an RTA apparatus as shown in FIG. If heat treatment is performed using an RTA apparatus, heating and cooling in the heat treatment are performed in a few seconds to several hundred seconds, so a short time of a few seconds to several hundred seconds without giving a harmful long-term heat history to the wafer. An effective heat treatment can be performed.

For example, using the RTA apparatus shown in FIG. 3, rapid heating is performed at a heating rate of 5 ° C./sec or more in an argon and / or hydrogen atmosphere, and the desired temperature of about 1000 to 1300 ° C. is held for 1 to 60 seconds. Thereafter, RTP treatment can be performed which rapidly cools at a temperature lowering rate of 5 ° C./sec or more.
By successively introducing the wafers into the furnace and continuously performing the heat treatment, it is possible to efficiently and effectively heat the wafer.
At this time, it is more preferable that nitrogen and / or oxygen gas is contained because surface roughness of the wafer surface can be prevented.

  In the silicon single crystal wafer of the present invention and the method for producing a silicon single crystal wafer, the wafer diameter is not particularly limited. For example, it can be applied to a wafer having a large diameter of 200 mm or more, further 300 mm or more. A silicon single crystal wafer having a uniform in-plane characteristic can be obtained in response to the demand for a diameter.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to this.
(Examples 1-7)
A single crystal pulling apparatus shown in FIG. 2 was used to charge a raw material polycrystalline silicon and a silicon wafer with a nitride film into a quartz crucible having a diameter of 24 inches (60 cm) to pull a silicon single crystal having a diameter of 8 inches (200 mm). The nitrogen concentration to be doped was controlled by the thickness of the nitride film. The crucible can be moved up and down in the direction of the crystal growth axis. The crucible is raised so as to compensate for the lowering of the raw material melt that has decreased during crystal growth, and the height of the surface of the melt is kept constant while maintaining the height of the melt. Pulled up.
Further, a horizontal magnetic field was applied to the raw material melt, and the rotation speed of the crucible was controlled at 0.01 to 0.1 rpm to control the oxygen concentration. Further, the crystal pulling rate was changed in the range of 0.56 to 0.60 mm / min to grow the crystal in the entire N-region.
By appropriately adjusting the operating conditions such as these, the entire surface of the crystal becomes an N-region, and the nitrogen concentration and oxygen concentration doped in the silicon single crystal to be grown are controlled, and the grown silicon single crystal is The silicon single crystal wafer of the present invention having different nitrogen concentration and oxygen concentration was obtained by slicing. Table 1 shows the oxygen concentration, nitrogen concentration, TDDB characteristics described later, and BMD test results of each sample (Examples 1 to 7).

After subjecting the wafers of Examples 1 to 7 to non-stirring selective etching (removal allowance 25 μm, Seco etching), the surface was observed with a microscope. As a result, the flow pattern called FPD observed when there is a void defect due to vacancy or the etch pit observed when there is a transition cluster due to Interstitial-Si was not observed. In addition, this wafer was subjected to an OSF formation heat treatment in a wet O ₂ atmosphere at 1150 ° C. for 60 minutes, and then subjected to selective etching (removal allowance: 7 μm, NIT solution). When the presence or absence of OSF was confirmed with a microscope, OSF was observed. There wasn't.
Thus, it can be seen that a silicon single crystal wafer having an entire N-region is obtained. Moreover, the nitrogen-doped wafer could be easily obtained in a wide range of pulling speeds that can be controlled and easily obtained in the N-region.

Next, as a result of forming an oxide film with a thickness of 25 nm on the same wafer and investigating the electrical characteristics of this oxide film, the non-defective rate of both TZDB characteristics and TDDB characteristics is 90% or more in any of the wafers of the present invention. Thus, it was found that the film has excellent oxide film pressure resistance characteristics.
FIG. 4 shows the result. In FIG. 4, the case where the non-defective product rate of the TDDB characteristic is less than 90% is indicated by x, and the case where it is 90% or more is indicated by ●.

In addition, each similar wafer was subjected to heat treatment simulating a device process. That is, a total of 20 hours of heat treatment was performed between 750 ° C. and 950 ° C. mainly at 800 ° C. After this heat treatment, the in-plane distribution of BMD was evaluated using an infrared scattering tomograph (MO441 manufactured by Mitsui Kinzoku Co., Ltd.). As a result, every wafer was able to achieve 1 × 10 ⁷ pieces / cm ³ over the entire surface of the wafer. That is, it has been found that a wafer having sufficient gettering ability can be obtained.

  Furthermore, it can be seen that the ratio between the maximum value and the minimum value of BMD is 50 times or less as shown in Table 1. As described above, since the silicon single crystal wafer has a uniform BMD density in the wafer plane, it can exhibit a uniform gettering ability in the plane, and the wafer caused by non-uniform BMD density distribution. Generation | occurrence | production of curvature etc. can be prevented effectively.

(Comparative Examples 1-6, Reference Example)
A silicon single crystal wafer was obtained by pulling and slicing a silicon single crystal in the same manner as in Example 1 except that the nitrogen concentration and oxygen concentration to be doped were changed as shown in Table 1 (Table 1, Comparative Example 1). To 6, Reference Example).
At this time, the operating conditions were adjusted by the thickness of the nitride film (Non-dope is thickness 0) and the crucible rotation so that the nitrogen concentration and oxygen concentration shown in Table 1 were obtained.

  These wafers were examined for the presence of FPD, etch pits, and OSF in the same manner as in the Examples, but none were observed. Thus, it can be seen that a silicon single crystal wafer having an entire N-region was obtained.

Moreover, about Comparative Examples 1-5, ie, when oxygen concentration is 13 ppma or more, or nitrogen concentration exceeds 3 * 10 < ¹³ > atoms / cm < ³ >, BMD investigated similarly to Example 1. In both cases, a density of 1 × 10 ⁷ pieces / cm ³ was achieved over the entire surface of the wafer, and the maximum / minimum values were also suppressed to 50 times or less.

  However, regarding the same wafer, the TZDB characteristic and the TDDB characteristic were investigated in the same manner as in Example 1. As a result, the non-defective product ratio of the TZDB characteristic was 90% or more, but the TDDB characteristic was less than 90%. I found out that As described above, when there is a defect in the TDDB characteristic as described above, the state-of-the-art device is defective.

On the other hand, in the case of Comparative Example 6 in which the nitrogen concentration is less than 5 × 10 ¹¹ atoms / cm ³ , the minimum value of BMD is 2 × 10 ⁵ pieces / cm ³ or less, and the maximum value / minimum value is 500 times or more. It has become. Thus, if the distribution of BMD density is non-uniform, warpage or the like is likely to occur during heat treatment. In addition, the gettering ability becomes non-uniform in the wafer surface and the gettering ability becomes insufficient.
In the case of the reference example having an oxygen concentration of less than 8 ppma, the maximum / minimum value of BMD is 2 × 10 ⁵ pieces / cm ³ or less, the BMD density is extremely low, and the IG capability is insufficient in the first place. End up.
The non-defective product ratios of the TZDB characteristic and the TDDB characteristic were both 90% or more.

(Comparative Examples 7 to 10)
A silicon single crystal wafer was obtained by pulling and slicing a silicon single crystal in the same manner as in Example 1 except that nitrogen was not doped and the oxygen concentration was changed as shown in Table 1 (Table 1, comparison). Examples 7 to 10). The nitrogen concentration at this time was below the detection limit.

  These wafers were examined for the presence of FPD, etch pits, and OSF in the same manner as in the Examples, but none were observed. Thus, it can be seen that a silicon single crystal wafer having an entire N-region was obtained.

BMD was investigated in the same manner as in Example 1. As a result, although 1 × 10 ⁷ pieces / cm ³ was partially achieved in the wafer surface, the wafer was able to achieve this over the entire wafer surface. There was no. Therefore, it was apparent that the gettering ability was insufficient. Then, the maximum / minimum value of the BMD density is 50 times or more, and the gettering ability becomes non-uniform in the wafer plane. Further, the wafer is easily warped by heat treatment or the like.
The non-defective product ratios of the TZDB characteristic and the TDDB characteristic were both 90% or more.

(Example 8)
A silicon single crystal wafer is manufactured in the same manner as in Example 1, and the wafer is heat-treated using the RTA apparatus shown in FIG. 3 to dissolve oxygen precipitates on the wafer surface layer and to form BMD inside the wafer. And gettering ability.
The heat treatment conditions were rapid heating and rapid cooling heat treatment at 1200 ° C. for 10 seconds in a mixed atmosphere of argon and hydrogen.

When this silicon single crystal wafer was tested in the same manner as in Example 1, no FPD, etch pits, or OSF were observed on the surface layer of the wafer, and abnormal oxygen precipitation due to the harmful effects of nitrogen was observed. It was found that a sufficient defect-free layer was obtained.
In addition, an excellent silicon single crystal wafer having a sufficient gettering capability was obtained because BMD was uniformly formed at 1 × 10 ⁷ pieces / cm ³ or more inside. Even when the wafer was subjected to the heat treatment, deformation such as warping was not observed on this wafer.

  Examples 1 to 8 and Comparative Examples 1 to 10 for the 200 mm diameter silicon single crystal wafer as described above were subjected to the same experiment as the reference example for the 300 mm diameter silicon single crystal wafer. In both cases, almost the same results were obtained as when the diameter was 200 mm.

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

It is a conceptual diagram showing typically the silicon single crystal wafer of the present invention. It is the schematic which shows an example of the single crystal pulling apparatus which can be used for the manufacturing method of the silicon single crystal wafer of this invention. It is the schematic which shows an example of the RTA apparatus which can be used for the manufacturing method of the silicon single crystal wafer of this invention. It is a figure which shows the result of the nitrogen concentration, oxygen concentration, and TDDB characteristic in the silicon single crystal wafer of an Example, a comparative example, and a reference example.

Explanation of symbols

1 ... main chamber, 2 ... pulling chamber, 3 ... single crystal rod (silicon single crystal),
4 ... Raw material melt, 5 ... Quartz crucible, 6 ... Graphite crucible, 7 ... Heater,
8 ... heat insulating member, 9 ... gas outlet, 10 ... gas inlet,
11 ... Cooling cylinder, 12 ... Cooling medium inlet, 13 ... Cooling auxiliary member,
14 ... Heat shield member, 15 ... Protective cover, 16 ... Wire, 17 ... Seed crystal,
18 ... Single crystal pulling device,
21, 31 ... silicon single crystal wafer, 22 ... surface layer region, 23 ... bulk region,
24 ... BMD,
30 ... Gas exhaust port, 32 ... Rapid heating / cooling device, 33 ... Chamber,
34 ... heating lamp, 35 ... auto shutter, 36 ... tray,
37 ... support part, 38 ... buffer, 39 ... pyrometer.

Claims (8)

  A silicon single crystal wafer grown by the Czochralski method, which is doped with nitrogen and has an entire N-region, has a good product ratio of TZDB characteristics and TDDB characteristics of 90% or more, and is subjected to gettering heat treatment or A silicon single crystal wafer characterized in that the ratio (maximum value / minimum value) between the maximum value and the minimum value of the BMD density in the wafer surface after device heat treatment is 50 times or less.   The silicon single crystal wafer according to claim 1, wherein the silicon single crystal wafer has an oxygen concentration of 8 ppma or more and less than 13 ppma (JEIDA). ^3. The silicon single crystal wafer according to claim 1, wherein the concentration of the doped nitrogen is 5 × 10 ¹¹ atoms / cm ³ or more and 3 × 10 ¹³ atoms / cm ³ or less. 4. The silicon single body according to claim 1, wherein a BMD density inside the wafer after the gettering heat treatment or device heat treatment is 1 × 10 ⁷ pieces / cm ³ or more. 5. Crystal wafer.   The silicon single crystal wafer according to any one of claims 1 to 4, wherein an oxygen precipitate on a surface layer of the wafer is dissolved by heat treatment. When growing a silicon single crystal by the Czochralski method, nitrogen having a concentration of 5 × 10 ¹¹ atoms / cm ³ or more and 3 × 10 ¹³ atoms / cm ³ or less and oxygen having a concentration of 8 ppma or more and less than 13 ppma (JEIDA) A method for producing a silicon single crystal wafer, wherein the entire surface of the crystal is pulled up under N-region while doping.   A silicon single crystal wafer obtained by subjecting a silicon single crystal wafer obtained by the method according to claim 6 to a heat treatment at 1000 to 1300 ° C. for 10 seconds to 1 hour to dissolve oxygen precipitates on the surface layer of the wafer. Manufacturing method. The method for producing a silicon single crystal wafer according to claim 7, wherein the heat treatment is performed by a rapid heating / cooling apparatus.

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