JP2009021623A - Method of manufacturing silicon wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silicon wafer which secures a sufficient denude zone near the surface of the wafer and has a defect distribution so controlled as to obtain a sufficient gettering effect within a bulk region of the wafer. <P>SOLUTION: In the silicon wafer, a concentration profile of an oxygen deposit from the front surface to the rear surface wherein an active region of a semiconductor element is formed has a first peak and a second peak at predetermined depths from the front surface and the rear surface, respectively. In regions of the silicon wafer before reaching the first peak and the second peak from the front surface and the rear surface, respectively, there are denude zones formed. In the bulk region between the first peak and the second peak, the concentration profile of the oxygen deposit is convex downward. Thus, the silicon wafer has a controlled distribution of the oxygen deposit characterized by the concentration profile. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a silicon wafer with controlled defect distribution, its manufacturing process and a Czochralski puller for the production of single crystal silicon ingots for the formation of these wafers. In particular, the present invention relates to a heat treatment process for controlling the distribution of nucleation centers of oxygen precipitates serving as a gettering site, and a wafer preparation process for performing this process.

  Single crystal silicon, which is a starting material for manufacturing a semiconductor element, is generally formed into a cylindrical ingot by a crystal growth method called a Czochralski (CZ) method. The ingot-shaped single crystal silicon is manufactured as a wafer through a wafer ring process such as cutting, etching, cleaning, and polishing. The Czochralski method is to perform crystal growth while bringing a single crystal seed crystal into contact with a silicon melt and then slowly pulling it up. Since the silicon melt is contained in a quartz crucible, it contains various impurities, particularly oxygen. At the temperature of the silicon melt, oxygen penetrates into the crystal lattice until it reaches a concentration determined by the solubility of oxygen in silicon corresponding to the temperature of the melt and the actual separation factor of oxygen in solid-phased silicon. To do. Thus, the concentration of oxygen that has penetrated into the silicon ingot during crystal growth is a typical temperature during the fabrication of subsequent integrated circuits, which is much greater than the oxygen solubility in solid phase silicon corresponding to this temperature. On the other hand, as the crystal grows and cools, the solubility of oxygen in the crystal drops sharply, resulting in supersaturation of oxygen in the cooled ingot, which are void-like crystals called D-defects. Defects are formed in the ingot.

  Such a D-defect causes a pit-like COP (Crystal Originated Precipitate) having a {111} plane on the wafer surface through a wafer ring process such as ingot cutting, polishing, and cleaning. In addition, these are gradually increased by the cleaning and oxidation processes repeatedly performed during the fabrication of the subsequent integrated circuit elements, and the number thereof is increased rapidly. FIG. 1 is a view showing a cross section of a conventional MOS transistor. Referring to this, when the COP on the wafer surface exists in the active region of the semiconductor element, for example, in the channel region between the source region 12 and the drain region 14 formed near the surface of the silicon substrate 10, the gate electrode 18 In addition, the gate insulating film 16 that electrically insulates the silicon substrate 10 is broken, and in addition, the refresh characteristics of the memory element are also deteriorated. Further, when such a COP on the wafer surface exists in the field oxide film that separates the active region of the semiconductor element, impurity ions implanted during the ion implantation process penetrate into the bulk region below the field oxide film, and as a result. In this case, poor element isolation due to channeling is caused.

  On the other hand, oxygen precipitates formed in the bulk region of the wafer (10a in FIG. 1) by the subsequent heat treatment act as a leakage current source, but are intrinsic capable of trapping undesirable metal contaminants during subsequent semiconductor device fabrication. Also acts as a gettering site. Therefore, if the oxygen concentration in the ingot is sufficiently high, the amount of oxygen precipitates that are intrinsic gettering sites will increase and the gettering performance will be improved. On the other hand, if the oxygen concentration is not sufficient, oxygen precipitation will occur. No object is formed and gettering performance is lost. For this reason, it is necessary to adjust so that an appropriate amount of oxygen precipitates is distributed in the bulk region of the wafer.

  On the other hand, oxygen precipitates are distributed as a whole from the front surface to the back surface of a wafer that has been ingot-grown by a conventional general method and that has been subjected to wafer ringing. In particular, oxygen-related defects, that is, voids, COPs, dislocations, stacking faults, oxygen precipitates, etc., from the front surface of the wafer where the active region of the semiconductor device is formed to a certain depth (10b in FIG. 1) A de-nude zone 10b layer that does not exist must be secured. However, the wafer manufactured by the conventional method has a problem that oxygen precipitates are distributed to the vicinity of the surface and this acts as a leakage current source.

  Therefore, in order to form intrinsic gettering in the bulk region of the wafer while securing a sufficient denuded zone near the surface of the wafer, a high oxygen concentration, for example, an initial oxygen concentration of 13 ppma (parts per million) has been conventionally used. atom) or higher wafers are subjected to a low temperature-high temperature-low temperature heat treatment for a long time, thereby forming oxygen precipitates in the bulk region of the wafer and decomposing oxygen precipitates in the vicinity of the wafer surface. Techniques for securing nude zones have been used. FIG. 2 is a graph showing a concentration profile of oxygen precipitates from the front surface to the back surface of a semiconductor wafer heat-treated by such a conventional technique.

  According to FIG. 2, it is possible to achieve both intrinsic gettering in the bulk region and securing a sufficient denuded zone near the wafer surface by the conventional technique. However, since the heat treatment process is performed for a long time at a high temperature, the wafer characteristics are deteriorated, for example, slippage and sintering distortion occur, and the cost is increased. Also, in this case, metal contaminants trapped by oxygen precipitates in the bulk region, particularly iron (Fe), etc., are released again toward the denuded zone on the wafer surface by a subsequent process, and this is a source of leakage. There is a problem of acting as.

FIG. 3 is a graph showing an extracted concentration profile of oxygen precipitates formed by another conventional method disclosed in FIG. 1A of Patent Document 1. That is, FIG. 3 shows a concentration profile according to the wafer depth of oxygen precipitates formed by performing a rapid thermal processing (RTA) step in a nitrogen atmosphere and then performing the thermal processing. However, as is apparent from FIG. 3, this method can hardly obtain a denuded zone from the surface of the wafer, and there is almost no oxygen precipitate in the bulk region, so that a sufficient gettering effect can be obtained. Absent.
US Pat. No. 5,401,669

SUMMARY OF THE INVENTION An object of the present invention is to provide a silicon wafer having a defect distribution controlled so as to obtain a sufficient gettering effect in a bulk region of the wafer while a sufficient denuded zone is secured near the surface of the wafer. That is.

  Another object of the present invention is to provide a silicon wafer manufacturing method capable of controlling a defect distribution so as to obtain a sufficient gettering effect in the bulk region of the wafer while a sufficient denuded zone is secured in the vicinity of the wafer surface. Is to provide.

  Still another object of the present invention is to provide a Czochralski puller for manufacturing a single crystal silicon ingot capable of rapid cooling to manufacture a silicon wafer according to the present invention.

The method for producing a silicon wafer of the present invention comprises preparing a silicon wafer,
Oxygen precipitates grow during the heat treatment subsequent to the rapid heat treatment by performing rapid heat treatment on the wafer surface in a mixed gas atmosphere of a gas having a vacancy injection effect and a gas having an interstitial silicon injection effect. A nucleation center that serves as a place to generate is generated, and a concentration profile of the nucleation center generated from the front surface to the back surface of the wafer is generated at a predetermined depth from the front surface and the back surface, respectively. Showing a peak, maintained below the critical value before reaching the first peak and the second peak respectively from the front surface and the back surface, and making the concentration profile of the nucleation center concave in the bulk region between the first peak and the second peak And a rapid heat treatment step,
The step of preparing the silicon wafer includes
High enough to prevent interstitial agglomeration, but low enough ingot pulling speed profile to limit vacancy agglomeration along the ingot axial direction into the vacancy-rich region. Pulling the ingot from the object,
Cutting the ingot in the radial direction to solve the above-mentioned problems.
The present invention provides a step of preparing a silicon wafer;
Oxygen precipitates grow during the heat treatment subsequent to the rapid heat treatment by performing rapid heat treatment on the wafer surface in a mixed gas atmosphere of a gas having a vacancy injection effect and a gas having an interstitial silicon injection effect. A nucleation center that serves as a place to generate is generated, and a concentration profile of the nucleation center generated from the front surface to the back surface of the wafer is generated at a predetermined depth from the front surface and the back surface, respectively. Showing a peak, maintained below the critical value before reaching the first peak and the second peak respectively from the front surface and the back surface, and making the concentration profile of the nucleation center concave in the bulk region between the first peak and the second peak And a rapid heat treatment step,
The step of preparing the silicon wafer includes
Its central bakery-rich region containing vacancy agglomerates and a defect-free region between said vacancy-rich region and wafer edge including interstitial point defects but no vacancy agglomerates and interstitial agglomerates Pulling the ingot from the silicon melt in the hot zone furnace with a pulling speed profile of the ingot producing a semi-perfect wafer with
Cutting the ingot in the radial direction to solve the above-mentioned problems.
The present invention provides a step of preparing a silicon wafer;
Oxygen precipitates grow during the heat treatment subsequent to the rapid heat treatment by performing rapid heat treatment on the wafer surface in a mixed gas atmosphere of a gas having a vacancy injection effect and a gas having an interstitial silicon injection effect. A nucleation center that serves as a place to generate is generated, and a concentration profile of the nucleation center generated from the front surface to the back surface of the wafer is generated at a predetermined depth from the front surface and the back surface, respectively. Showing a peak, maintained below the critical value before reaching the first peak and the second peak respectively from the front surface and the back surface, and making the concentration profile of the nucleation center concave in the bulk region between the first peak and the second peak And a rapid heat treatment step,
The step of preparing the silicon wafer includes
Pulling the ingot from the silicon melt in the hot zone furnace at a sufficiently high ingot pulling speed profile to prevent interstitial agglomeration but low enough to prevent bakery agglomeration;
Cutting the ingot in the radial direction to solve the above-mentioned problems.
The present invention provides a step of preparing a silicon wafer;
Oxygen precipitates grow during the heat treatment subsequent to the rapid heat treatment by performing rapid heat treatment on the wafer surface in a mixed gas atmosphere of a gas having a vacancy injection effect and a gas having an interstitial silicon injection effect. A nucleation center that serves as a place to generate is generated, and a concentration profile of the nucleation center generated from the front surface to the back surface of the wafer is generated at a predetermined depth from the front surface and the back surface, respectively. Showing a peak, maintained below the critical value before reaching the first peak and the second peak respectively from the front surface and the back surface, and making the concentration profile of the nucleation center concave in the bulk region between the first peak and the second peak And a rapid heat treatment step,
The step of preparing the silicon wafer includes
Pulling the ingot from the silicon melt in the hot zone furnace with a pulling speed profile of the ingot that produces perfect wafers that contain point defects but no interstitial and vacancy agglomerates;
Cutting the ingot in the radial direction to solve the above-mentioned problems.
The present invention provides a step of preparing a silicon wafer;
Oxygen precipitates grow during the heat treatment subsequent to the rapid heat treatment by performing rapid heat treatment on the wafer surface in a mixed gas atmosphere of a gas having a vacancy injection effect and a gas having an interstitial silicon injection effect. A nucleation center that serves as a place to generate is generated, and a concentration profile of the nucleation center generated from the front surface to the back surface of the wafer is generated at a predetermined depth from the front surface and the back surface, respectively. Showing a peak, maintained below the critical value before reaching the first peak and the second peak respectively from the front surface and the back surface, and making the concentration profile of the nucleation center concave in the bulk region between the first peak and the second peak And a rapid heat treatment step,
The step of preparing the silicon wafer includes
Pulling up the ingot from the silicon melt in the hot zone furnace with a sufficiently high ingot pulling speed profile so that the bakery agglomerate can form entirely along the radial direction of the ingot without forming interstitial agglomerates;
Cutting the ingot in the radial direction to solve the above-mentioned problems.
In the present invention, after the ingot is pulled up, the size of the bakery agglomerate formed in the silicon wafer can be formed to 0.2 μm or less.
In the present invention, after the ingot is pulled up, the size of the vacancy agglomerate formed in the silicon wafer can be preferably 0.2 μm or less.
According to the present invention, in the step of pulling up the ingot, the cooling rate of the central axis of the ingot within the temperature range of the ingot growth step may be at least 1.4 ° K / min.
In the step of pulling up the ingot, the pulling speed of the ingot may be in a range of 0.5 to 1.0 mm / min.

A silicon wafer having a controlled oxygen precipitate distribution which is the first invention related to the present invention is a step of preparing a silicon wafer;
Oxygen precipitates grow during the heat treatment subsequent to the rapid heat treatment by performing rapid heat treatment on the wafer surface in a mixed gas atmosphere of a gas having a vacancy injection effect and a gas having an interstitial silicon injection effect. A nucleation center that serves as a place to generate is generated, and a concentration profile of the nucleation center generated from the front surface to the back surface of the wafer is generated at a predetermined depth from the front surface and the back surface, respectively. Showing a peak, maintained below the critical value before reaching the first peak and the second peak respectively from the front surface and the back surface, and making the concentration profile of the nucleation center concave in the bulk region between the first peak and the second peak A rapid heat treatment stage,
By the subsequent heat treatment after the rapid heat treatment step,
The concentration profile of oxygen precipitates from the front surface to the back surface of the silicon wafer on which the active region of the semiconductor device is formed shows a first peak and a second peak at a predetermined depth from the front surface and the back surface, respectively. The denuded zone was formed before reaching the first peak and the second peak, and the concentration profile of the oxygen precipitate was made concave in the bulk region between the first peak and the second peak.
According to the present invention, the concentration profile of oxygen precipitates from the front surface to the back surface of a silicon wafer on which an active region of a semiconductor device is formed shows a first peak and a second peak at a predetermined depth from the front surface and the back surface, respectively. And a denuded zone is formed before reaching the first peak and the second peak from the back surface, respectively, and the concentration profile of oxygen precipitates is concave in the bulk region between the first peak and the second peak,
The depth of the denuded zone is controlled to be 10 μm to 40 μm from the wafer surface, thereby solving the above problem.
According to the present invention, the concentration profile of oxygen precipitates from the front surface to the back surface of a silicon wafer on which an active region of a semiconductor device is formed shows a first peak and a second peak at a predetermined depth from the front surface and the back surface, respectively. And a denuded zone is formed before reaching the first peak and the second peak from the back surface, respectively, and the concentration profile of oxygen precipitates is concave in the bulk region between the first peak and the second peak,
The depths of the first peak and the second peak are about 100 μm from the surface of the wafer, thereby solving the above problem.
According to the present invention, the concentration profile of oxygen precipitates from the front surface to the back surface of a silicon wafer on which an active region of a semiconductor device is formed shows a first peak and a second peak at a predetermined depth from the front surface and the back surface, respectively. And a denuded zone is formed before reaching the first peak and the second peak from the back surface, respectively, and the concentration profile of oxygen precipitates is concave in the bulk region between the first peak and the second peak,
The above problem has been solved by making the concentration of oxygen precipitates at the first peak and the second peak at least four times the concentration of oxygen precipitates in the bulk region.
In the present invention, the concentration profile of the oxygen precipitates may be symmetric about the center of the silicon wafer.
According to the present invention, the depth of the denuded zone can be ensured in the range of 20 μm to 40 μm from the surface of the wafer.
According to the present invention, the depth of the denuded zone can be ensured from the surface of the wafer to the vicinity of 30 μm.
In the present invention, the concentration of oxygen precipitates at the first peak and the second peak may be at least 1 × 10 ⁹ / cm ³ or more.
In the present invention, the concentration of oxygen precipitates in the bulk region between the first peak and the second peak may be at least 1 × 10 ⁸ / cm ³ or more.
In the present invention, COP may further exist only in the bulk region between the first peak and the second peak.
The method for producing a silicon wafer according to the second invention related to the present invention comprises the steps of preparing a silicon wafer,
Oxygen precipitates grow during the heat treatment subsequent to the rapid heat treatment by performing rapid heat treatment on the wafer surface in a mixed gas atmosphere of a gas having a vacancy injection effect and a gas having an interstitial silicon injection effect. A nucleation center that serves as a place to generate is generated, and a concentration profile of the nucleation center generated from the front surface to the back surface of the wafer is generated at a predetermined depth from the front surface and the back surface, respectively. Showing a peak, maintained below the critical value before reaching the first peak and the second peak respectively from the front surface and the back surface, and making the concentration profile of the nucleation center concave in the bulk region between the first peak and the second peak And a rapid heat treatment step,
The step of preparing the silicon wafer includes
High enough to prevent interstitial agglomeration, but low enough ingot pulling speed profile to limit vacancy agglomeration along the ingot axial direction into the vacancy-rich region. Pulling the ingot from the object,
Cutting the ingot in the radial direction to solve the above-mentioned problems.
The present invention provides a step of preparing a silicon wafer;
Oxygen precipitates grow during the heat treatment subsequent to the rapid heat treatment by performing rapid heat treatment on the wafer surface in a mixed gas atmosphere of a gas having a vacancy injection effect and a gas having an interstitial silicon injection effect. A nucleation center that serves as a place to generate is generated, and a concentration profile of the nucleation center generated from the front surface to the back surface of the wafer is generated at a predetermined depth from the front surface and the back surface, respectively. Showing a peak, maintained below the critical value before reaching the first peak and the second peak respectively from the front surface and the back surface, and making the concentration profile of the nucleation center concave in the bulk region between the first peak and the second peak And a rapid heat treatment step,
The step of preparing the silicon wafer includes
Its central bakery-rich region containing vacancy agglomerates and a defect-free region between said vacancy-rich region and wafer edge including interstitial point defects but no vacancy agglomerates and interstitial agglomerates Pulling the ingot from the silicon melt in the hot zone furnace with a pulling speed profile of the ingot producing a semi-perfect wafer with
Cutting the ingot in the radial direction to solve the above-mentioned problems.
The present invention provides a step of preparing a silicon wafer;
Oxygen precipitates grow during the heat treatment subsequent to the rapid heat treatment by performing rapid heat treatment on the wafer surface in a mixed gas atmosphere of a gas having a vacancy injection effect and a gas having an interstitial silicon injection effect. A nucleation center that serves as a place to generate is generated, and a concentration profile of the nucleation center generated from the front surface to the back surface of the wafer is generated at a predetermined depth from the front surface and the back surface, respectively. Showing a peak, maintained below the critical value before reaching the first peak and the second peak respectively from the front surface and the back surface, and making the concentration profile of the nucleation center concave in the bulk region between the first peak and the second peak And a rapid heat treatment step,
The step of preparing the silicon wafer includes
Pulling the ingot from the silicon melt in the hot zone furnace at a sufficiently high ingot pulling speed profile to prevent interstitial agglomeration but low enough to prevent bakery agglomeration;
Cutting the ingot in the radial direction to solve the above-mentioned problems.
The present invention provides a step of preparing a silicon wafer;
Oxygen precipitates grow during the heat treatment subsequent to the rapid heat treatment by performing rapid heat treatment on the wafer surface in a mixed gas atmosphere of a gas having a vacancy injection effect and a gas having an interstitial silicon injection effect. A nucleation center that serves as a place to generate is generated, and a concentration profile of the nucleation center generated from the front surface to the back surface of the wafer is generated at a predetermined depth from the front surface and the back surface, respectively. Showing a peak, maintained below the critical value before reaching the first peak and the second peak respectively from the front surface and the back surface, and making the concentration profile of the nucleation center concave in the bulk region between the first peak and the second peak And a rapid heat treatment step,
The step of preparing the silicon wafer includes
Pulling the ingot from the silicon melt in the hot zone furnace with a pulling speed profile of the ingot that produces perfect wafers that contain point defects but no interstitial and vacancy agglomerates;
Cutting the ingot in the radial direction to solve the above-mentioned problems.
The present invention provides a step of preparing a silicon wafer;
Oxygen precipitates grow during the heat treatment subsequent to the rapid heat treatment by performing rapid heat treatment on the wafer surface in a mixed gas atmosphere of a gas having a vacancy injection effect and a gas having an interstitial silicon injection effect. A nucleation center that serves as a place to generate is generated, and a concentration profile of the nucleation center generated from the front surface to the back surface of the wafer is generated at a predetermined depth from the front surface and the back surface, respectively. Showing a peak, maintained below the critical value before reaching the first peak and the second peak respectively from the front surface and the back surface, and making the concentration profile of the nucleation center concave in the bulk region between the first peak and the second peak And a rapid heat treatment step,
The step of preparing the silicon wafer includes
Pulling up the ingot from the silicon melt in the hot zone furnace with a sufficiently high ingot pulling speed profile so that the bakery agglomerate can form entirely along the radial direction of the ingot without forming interstitial agglomerates;
Cutting the ingot in the radial direction to solve the above-mentioned problems.
In the present invention, after the ingot is pulled up, the size of the vacancy agglomerate formed in the silicon wafer can be formed to 0.2 μm or less.
In the present invention, after the ingot is pulled up, the size of the vacancy agglomerate formed in the silicon wafer can be preferably 0.2 μm or less.
According to the present invention, in the step of pulling up the ingot, the cooling rate of the central axis of the ingot within the temperature range of the ingot growth step may be at least 1.4 ° K / min.
In the present invention, in the step of pulling up the ingot, the pulling speed of the ingot may be in the range of 0.5 to 1.0 mm / min.
A method for producing a silicon wafer according to a third invention related to the present invention includes a crystal growth step of forming an ingot using a Czochralski puller,
A cutting step that is performed after the crystal growth step and cuts the ingot into a wafer;
Etching step that is performed after the cutting step and cuts each cut wafer and etches the surface;
Performed after the etching step, a first cleaning step for the wafer surface;
A donor keying step performed after the first cleaning step;
A polishing step that is performed after the donor keying step and polishes the front surface of the wafer on which the semiconductor element is formed; a second cleaning step;
And a wafer packaging process performed after the second cleaning process,
The heat treatment in the donor keying step follows the rapid heat treatment by performing the rapid heat treatment on the wafer surface in a mixed gas atmosphere of a gas having a vacancy implantation effect and a gas having an interstitial silicon implantation effect. A nucleation center that serves as a place where oxygen precipitates grow during the heat treatment is generated, and a concentration profile of the nucleation center from the front surface to the back surface of the wafer generated thereby is a predetermined depth from the front surface and the back surface. In the bulk region between the first peak and the second peak, respectively, and is maintained below the critical value before reaching the first peak and the second peak from the front and back, respectively. The above-mentioned problem has been solved by being a rapid heat treatment step in which the concentration profile of the formation center is concave.
In the present invention, the mixed gas may be nitrogen gas + argon gas.
In the present invention, the mixed gas may be nitrogen gas + hydrogen gas.
In the present invention, the rapid thermal treatment step may include rapid cooling of at least 30 ° C./second or more.
In the present invention, the rapid thermal processing step may be performed at a temperature of at least 1150 ° C.
In the present invention, the rapid thermal processing step may be performed for at least 5 seconds.
In the present invention, the rapid thermal processing step may be performed at a temperature of at least 1150 ° C. for 30 seconds or more.
In the present invention, the rapid thermal processing step may be performed at a temperature of 1250 ° C. or more for 10 seconds or more.
The present invention provides a step of preparing a silicon wafer;
Comprising the aforementioned rapid thermal processing step,
The step of preparing the silicon wafer includes
High enough to prevent interstitial agglomeration, but low enough ingot pulling speed profile to limit vacancy agglomeration along the ingot axial direction into the vacancy-rich region. Pulling the ingot from the object,
Cutting the ingot in a radial direction.
The present invention provides a step of preparing a silicon wafer;
Comprising the aforementioned rapid thermal processing step,
The step of preparing the silicon wafer includes
Its central bakery-rich region containing vacancy agglomerates and a defect-free region between said vacancy-rich region and wafer edge including interstitial point defects but no vacancy agglomerates and interstitial agglomerates Pulling the ingot from the silicon melt in the hot zone furnace with a pulling speed profile of the ingot producing a semi-perfect wafer with
Cutting the ingot in a radial direction.
The present invention provides a step of preparing a silicon wafer;
Comprising the aforementioned rapid thermal processing step,
The step of preparing the silicon wafer includes
Pulling the ingot from the silicon melt in the hot zone furnace at a sufficiently high ingot pulling speed profile to prevent interstitial agglomeration but low enough to prevent bakery agglomeration;
Cutting the ingot in a radial direction.
The present invention provides a step of preparing a silicon wafer;
Comprising the aforementioned rapid thermal processing step,
The step of preparing the silicon wafer includes
Pulling the ingot from the silicon melt in the hot zone furnace with a pulling speed profile of the ingot that produces perfect wafers that contain point defects but no interstitial and vacancy agglomerates;
Cutting the ingot in a radial direction.
The present invention provides a step of preparing a silicon wafer;
Comprising the aforementioned rapid thermal processing step,
The step of preparing the silicon wafer includes
Pulling up the ingot from the silicon melt in the hot zone furnace with a sufficiently high ingot pulling speed profile so that the bakery agglomerate can form entirely along the radial direction of the ingot without forming interstitial agglomerates;
Cutting the ingot in a radial direction.
In the present invention, after the ingot is pulled up, the size of the vacancy agglomerate formed in the silicon wafer can be formed to 0.2 μm or less.
In the present invention, after the ingot is pulled up, the size of the vacancy agglomerate formed in the silicon wafer can be preferably 0.2 μm or less.
According to the present invention, in the step of pulling up the ingot, the cooling rate of the central axis of the ingot within the temperature range of the ingot growth step may be at least 1.4 ° K / min.
In the present invention, in the step of pulling up the ingot, the pulling speed of the ingot may be in the range of 0.5 to 1.0 mm / min.
The Czochralski puller according to the fourth invention related to the present invention includes a sealed body,
A crucible in the sealed body for storing the silicon melt;
A seed holder in the sealed body adjacent to the crucible;
A heater in the sealed body surrounding the crucible;
An internal heat shield housing wall that is vertical, an external heat shield housing wall that is spaced apart from and perpendicular to the internal heat shield housing, and connects between the internal heat shield housing wall and the external heat shield housing wall and in an outward direction A ring-shaped heat-insulating housing that includes a heat-insulating housing lid body that is inclined upward, and an inner heat-insulating housing wall and an outer heat-insulating housing wall that are connected to each other and includes a heat-insulating housing bottom that is inclined downward in an outward direction;
The above-mentioned problem has been solved by comprising a support member arranged so as to support the heat shield housing in the crucible.
According to the present invention, the ring-shaped heat shield housing can be filled with a heat absorbing material capable of absorbing heat.
The present invention may further include a cylindrical cooling jacket that extends downward from the upper side of the sealing body so that the seed holder can be pulled up.
The present invention may further include a heat shield plate that surrounds the pulled up ingot between the heat shield housing lid of the heat shield housing and the cooling jacket.
The present invention further includes means for pulling up the single crystal silicon ingot from the silicon melt by pulling up the seed holder from the crucible, the single crystal silicon ingot having an ingot shaft and a cylindrical edge, and The melt and the ingot are separated by an ingot-melt interface, and the cooling rate of the ingot is changed from the temperature of the ingot shaft at the ingot-melt interface to the temperature at which the temperature of the ingot shaft corresponds to the growth stage of the ingot. The inclination angle of the bottom of the heat shield housing so as to be at least 1.4 ° K / min, the distance from the ingot to the internal heat shield housing wall, the distance from the crucible to the external heat shield housing wall, and the heat shield plate A sequence of can be selected.
In the present invention, the heat shield housing may be made of carbon ferrite.

  In order to achieve the object of the present invention, the silicon wafer according to the first aspect of the present invention has a constant vertical distribution of oxygen precipitates which are intrinsic gettering sites. That is, the concentration profile of oxygen precipitates from the front surface to the back surface of the silicon wafer where the active region of the semiconductor element is formed shows a first peak and a second peak at a predetermined depth from the front surface and the back surface of the wafer, respectively. A denuded zone is formed before reaching the first and second peaks from the front and back surfaces of the wafer, respectively. The concentration profile of oxygen precipitates in the bulk region of the wafer between the first peak and the second peak is concave.

  Preferably, the concentration profile of the oxygen precipitates is symmetric with respect to the center of the silicon wafer, and the depth of the denuded zone is 20 μm to 40 μm from the surface of the wafer so that an active region of a semiconductor device can be sufficiently formed. Secured in the range. There are no crystal defects related to oxygen in the denuded zone, and in addition to oxygen precipitates, void-shaped D-defects having a certain size and concentration can further exist in the bulk region.

The concentration of oxygen precipitates at the first peak and the second peak is at least 1 × 10 ⁹ / cm ³ or more, and the concentration of oxygen precipitates in the bulk region between the first peak and the second peak Is preferably at least 1 × 10 ⁸ / cm ³ or more from the viewpoint of gettering metal contaminants.

  In order to achieve the above-mentioned object, the silicon wafer according to the second aspect of the present invention is a nucleation center of an oxygen precipitate that obtains a concentration profile of the oxygen precipitate of the first aspect by a subsequent heat treatment, for example, A first peak and a second peak are respectively shown at a predetermined depth from the front surface and the back surface of the silicon wafer so that the concentration profile of the vacancy is similar to the concentration profile of the oxygen precipitate. The vacancy concentration profile before reaching the first peak and the second peak from the front surface and the back surface, respectively, is maintained below a critical value, and the vacancy concentration profile in the bulk region between the first peak and the second peak is concave. is there.

  In order to achieve the object of the present invention, according to the present invention, a step of preparing a silicon wafer, a gas having a vacancy injection effect on the wafer surface and a gas having an interstitial silicon injection effect are provided. A nucleation center that serves as a place where oxygen precipitates grow during the subsequent heat treatment in a mixed gas atmosphere, and a concentration profile of the nucleation center from the front surface to the back surface of the wafer. Shows a first peak and a second peak at a predetermined depth from the front surface and the back surface, respectively, and is maintained below a critical value before reaching the first peak and the second peak from the front surface and the back surface, respectively. And a rapid heat treatment step for making the concentration profile of the nucleation center concave in the bulk region between the second peaks. Method for producing Eha is provided.

  After the rapid thermal processing step, the concentration profile of the oxygen precipitates from the front surface to the back surface of the wafer is changed to a first peak and a second peak at a predetermined depth from the front surface and the back surface by the subsequent heat processing step in the semiconductor device manufacturing step. A denuded zone is formed before reaching the first peak and the second peak from the front surface and the back surface, respectively, and the concentration profile of oxygen precipitates in the bulk region between the first peak and the second peak is concave. is there.

  As the mixed gas, nitrogen gas + argon gas or nitrogen gas + hydrogen gas is used, and the mixing ratio and flow rate of the mixed gas, the temperature rise rate in the rapid heat treatment stage, the heat treatment temperature, the heat treatment time, the temperature drop rate, etc. To adjust the peak value of the first peak and the second peak of the oxygen precipitate and the concentration value of the bulk region, or the depth of the denuded zone.

  On the other hand, the silicon wafer to which the rapid thermal processing step of the present invention is applied is sufficiently high to prevent interstitial agglomeration, but restricts the vacancy agglomeration within the vacancy-rich region along the axial direction of the ingot. It can be provided from an ingot pulled from the silicon melt in the hot zone furnace with a sufficiently low ingot pulling profile.

  Other silicon wafers to which the rapid thermal processing step of the present invention is applied are hot zone furnaces with an ingot pulling speed profile that is high enough to prevent interstitial agglomeration but low enough to prevent vacancy agglomeration. It can also be provided from a silicon ingot pulled up from the silicon melt inside.

  Still another silicon wafer to which the rapid thermal processing step of the present invention is applied has a sufficiently high ingot so that the bakery agglomerate is formed entirely along the radial direction of the ingot without forming an interstitial agglomerate. It can also be provided from an ingot pulled from the silicon melt in the hot zone furnace with a pulling rate profile.

  Furthermore, in order to achieve the object of the present invention, according to the present invention, a sealed body, a crucible in the sealed body for storing silicon melt, a seed holder in the sealed body adjacent to the crucible, A heater in the sealed body surrounding the crucible, an internal heat shield housing wall that is vertical, an external heat shield housing wall that is spaced and perpendicular to the internal heat shield housing, the internal heat shield housing wall and the external heat shield A heat shield housing lid that is connected to the housing wall and inclined upward in the outward direction, and a heat shield that connects the internal heat shield housing wall and the external heat shield housing wall and that is inclined downward in the outward direction. A ring-shaped heat shield housing including a housing bottom; and a support member arranged to support the heat shield housing in the crucible CZ puller for growing single crystal silicon ingot comprising is provided.

  And further comprising means for pulling up the single crystal silicon ingot from the silicon melt by pulling up the seed holder from the crucible, the single crystal silicon ingot having an ingot shaft and a cylindrical edge, and the silicon melt and The ingot is separated by an ingot-melt boundary, and the cooling rate of the ingot is at least 1. from the temperature of the ingot axis at the ingot-melt boundary to the temperature at which the temperature of the ingot axis corresponds to the growth stage of the ingot. The inclination angle of the bottom of the heat shielding housing, the distance from the ingot to the inner heat shielding housing wall, the distance from the crucible to the outer heat shielding housing wall, and the arrangement of the heat shielding plates so as to be 4 ° K / min or more. You can choose.

  According to the present invention, a peak value is obtained at a certain depth from the surface by performing rapid thermal processing in a gas atmosphere in which a gas having an interstitial injection effect and a gas having a vacancy injection effect are appropriately mixed on the wafer surface. Since the double-peak oxygen precipitate nucleation center having the above can be formed, a stable oxygen precipitate concentration profile can be secured by the subsequent heat treatment.

  Further, according to the present invention, since the rapid thermal processing is performed in the gas atmosphere having the interstitial injection effect on the surface of the wafer, even if the wafer contains void-shaped D-defects, On the other hand, the decomposition of the D-defect occurs, and as a result, a clean active region of the semiconductor element can be secured.

  Further, according to the Czochralski puller of the present invention, the ingot can be rapidly cooled, so that voids that can be generated during the formation of the ingot can be reduced. Therefore, when the rapid heat treatment of the present invention is performed, voids of a predetermined size exist in the bulk region within the wafer, but these voids can be decomposed in the denuded zone.

  According to the present invention, it is possible to form a silicon wafer in which a denuded zone is sufficiently secured in the vicinity of the wafer surface and oxygen precipitates are distributed so that a sufficient gettering effect can be obtained in the bulk region of the wafer. .

  Further, a sufficient denuded zone is secured in the vicinity of the wafer surface, and the defect distribution can be freely controlled so that a sufficient gettering effect is obtained in the bulk region of the wafer. In addition, when the puller of the present invention is used, the ingot to be grown can be rapidly cooled, so that the void in the ingot can be reduced.

  The present invention will be described in detail by way of preferred embodiments. However, the present invention is not limited to these embodiments, and ordinary knowledge in this field is within the scope of the technical idea of the present invention. Various modifications are possible for the person who has it.

  The following embodiments are merely examples of the present invention, and various modifications may be made within the spirit of the present invention. In particular, the temperature, time, cooling rate, gas mixing ratio, and the like of the rapid heat treatment process can be set in various ways, and various puller structures are possible even at the wafer preparation stage.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Preparation of a silicon wafer product in which the idea of the invention is more concentrated, a “heat treatment stage for the wafer” on the result of the rapid heat treatment process and the subsequent heat treatment in the manufacturing process of the silicon wafer, and a wafer to which the present invention is applied The steps and the “wafer preparation step” for the apparatus will be described sequentially.

[Heat treatment for wafers]
FIG. 4 is a diagram schematically illustrating a concentration profile of oxygen precipitates on a silicon wafer to be formed according to an embodiment of the present invention. As shown in FIG. 2 and FIG. 3, according to the present invention, compared to the concentration profile of oxygen precipitates in a silicon wafer formed by a conventional technique, the wafer has a certain depth from the front and back surfaces of the wafer. The reaching denuded zone is sufficiently secured, and a double peak having the maximum peak value is formed at the boundary between each denuded zone and the bulk region. In addition, the concentration of oxygen precipitates in the bulk region between the double peaks exists to such an extent that the gettering effect of the metal contaminant can be sufficiently exhibited.

  FIG. 5 is a time chart of an RTA process performed according to an embodiment of the present invention. As the RTA equipment to which the present invention is applied, an ordinary commercialized equipment can be used. Hereinafter, a rapid thermal process in the RTA equipment will be examined. First, a silicon wafer to which the present invention is applied is brought into an RTA equipment maintained at, for example, about 700 ° C. and waited (I). Next, the temperature in the RTA equipment is rapidly increased, for example, to 1250 ° C. at a rate of 50 ° C./min (II). Next, the temperature of 1250 ° C. is maintained for a certain time, for example, 10 seconds (III). Next, the temperature is rapidly cooled to a standby temperature at a rate of 33 ° C./min (IV). Next, the wafer is unloaded (V). By performing the rapid heat treatment as shown in FIG. 5, oxygen precipitate nucleation centers having a controlled distribution are obtained. On the other hand, as described in the explanation of FIG. 11, voids or COPs existing on the surface of the wafer are obtained. The decomposition effect is obtained.

  Although the temperature conditions shown in FIG. 5 exemplarily illustrate an embodiment of the present invention, as will be described later, in the present invention, the type of atmospheric gas for rapid thermal processing, the flow rate of the atmospheric gas, The mixing ratio, the rate of temperature increase until the rapid heat treatment stage, the annealing temperature and annealing time in the rapid heat treatment stage, the temperature decrease rate from the rapid heat treatment stage (that is, the cooling rate), etc. act as important factors. The rapid heat treatment in the present invention is performed at a temperature of at least 1150 ° C. or more for at least 5 seconds. For example, heat treatment is performed at 1150 ° C. for at least about 30 seconds, and heat treatment is performed at 1250 ° C. for at least about 5 seconds to 10 seconds. On the other hand, the cooling rate is at least 30 ° C./second or more.

  As a gas for performing the rapid thermal processing of the present invention, basically, a gas having a vacancy injection effect on the surface of the wafer exposed to the gas atmosphere during the rapid thermal processing and an interstitial silicon injection effect on the surface of the wafer. It is possible to use a mixed gas obtained by mixing gases having a certain ratio. In this embodiment, nitrogen gas is used as a representative example of a gas having a bakery injection effect, and argon gas and hydrogen gas are used as representative examples of a gas having an interstitial silicon injection effect.

  FIG. 6 is a diagram showing concentration profiles of point defects of baked silicon and interstitial silicon after performing the RTA process of FIG. 5 in a nitrogen gas atmosphere, and FIG. 7 is a diagram in an argon gas atmosphere. FIG. 5 is a diagram showing a concentration profile of point defects after performing the RTA process 5. FIG. 8 is a diagram showing a concentration profile of point defects after the RTA process of FIG. 5 is performed in a hydrogen gas atmosphere.

  6 to 8, the circled number 1 is the concentration profile of the vacancy point defect after the RTA process of FIG. 5 is performed under an inert gas atmosphere, and the circled number 2 is a graph of FIG. 5 is the concentration profile of the interstitial point defect after the RTA process is performed, and the circled numeral 3 is the concentration profile of the bakery point defect after the RTA process of FIG.

  It can be seen that the concentration of vacancy point defects after performing the RTA process in an inert gas atmosphere is low on the front and back surfaces of the wafer and rises in the vicinity of the bulk region of the wafer. Generally, when the temperature is rapidly increased up to (a) in FIG. 5 in an inert gas atmosphere, the equilibrium concentration corresponding to the temperature of the vacancy existing as a point defect in the wafer increases. At this time, since the mobility of vacancy is low in the bulk region of the wafer, the vacancy concentration is kept lower than the equilibrium concentration. On the other hand, since the movement of vacancy is active in the surface area of the wafer, the equilibrium concentration is maintained almost the same. Conversely, interstitial silicon increases in vacancy concentration as temperature rises rapidly, and at the same time, the equilibrium concentration corresponding to that temperature decreases due to Frenkel recombination. At this time, the interstitial existing in the bulk region of the wafer is maintained at a higher concentration than the equilibrium concentration because of its low mobility as in the case of the vacancy, but is close to the equilibrium concentration on the surface of the wafer as in the case of the vacancy.

  Next, when the temperature in (a) is maintained for a certain period of time until it reaches (b) in FIG. 5, diffusion occurs so that both vacancy and interstitial are maintained at equilibrium concentrations. Next, when this temperature is rapidly cooled to (c), the interstitial point defect with a large diffusion coefficient becomes the same as the new equilibrium concentration corresponding to the lowered temperature, but in the case of a vacancy with a small diffusion coefficient, it is supersaturated in the wafer. Is done. At this time, the supersaturation degree is large in the bulk region of the wafer, whereas the mobility of the vacancy is large in the vicinity of the wafer surface, so that it immediately approaches a new equilibrium concentration corresponding to the lowered temperature.

  For this reason, as shown in FIGS. 6 to 8, the vacancy concentration profile after the rapid heat treatment of FIG. 5 is performed in an inert gas atmosphere.

On the other hand, as shown in FIG. 6, when the RTA process of FIG. 5 is performed in a nitrogen gas atmosphere, the nitrogen gas and baked silicon that have penetrated deeply into the bulk region of the wafer are recombined to form a small volume silicon nitride (Si _In order to form ₃ N ₄ ), the concentration of vacancy is lowered. On the other hand, a vacancy injection effect occurs near the surface of the wafer, and the concentration of vacancy increases. For this reason, the vacancy concentration profile under an inert gas atmosphere has a shape opposite to the circled number 1.

  On the other hand, as shown in FIGS. 7 and 8, when the RTA process of FIG. 5 is performed in an argon gas or hydrogen gas atmosphere, the concentration of bakery decreases over the entire wafer due to the interstitial silicon implantation effect. Especially, near the surface of the wafer, the recombination of vacancy silicon and interstitial silicon occurs abruptly due to the interstitial silicon injection effect, and the vacancy concentration is maintained at a specific critical value that is the equilibrium concentration at the corresponding temperature. .

  On the other hand, in the embodiment of the present invention, the RTA process of FIG. 5 is performed in an atmosphere of nitrogen gas and argon gas, or a mixed gas of nitrogen gas and hydrogen gas. By combining the vacancy concentration profiles of FIG. 8, the vacancy concentration profiles in these mixed gas atmospheres can be found. As shown in FIG. 9, the vacancy concentration profile under such a mixed gas atmosphere shows a first peak and a second peak at a predetermined depth from the front and back surfaces of the silicon wafer, respectively. It can be seen that before reaching the first peak and the second peak, it is maintained below a certain critical value, that is, below the equilibrium concentration at the corresponding temperature. The concentration profile of vacancy in the bulk region between the first peak and the second peak has a raised shape.

  Here, the vacancy concentration profile as shown in FIG. 9 is obtained because the RTA process of FIG. 5 is performed in a mixed gas atmosphere of a gas having a vacancy silicon injection effect and a gas having an interstitial silicon injection effect. is there. Comparing the concentration profile of vacancy silicon due to the vesicle silicon injection effect under nitrogen gas and the concentration profile of interstitial silicon due to the interstitial silicon injection effect under argon gas or hydrogen gas on a logarithmic scale, The vacancy silicon concentration profile from the front and back surfaces of the wafer to the bulk region is less steep than the interstitial silicon concentration profile. However, this becomes steep above a certain depth from the wafer surface. Therefore, the denuded zone is formed in the vicinity of the surface within a certain depth from the front and back of the wafer, where interstitial silicon is recombined with vacancy silicon and vacancy silicon is specified. Is maintained below the critical value of, i.e., the equilibrium concentration at the temperature. This is the position at which the difference between the concentration value of the vacancy silicon and the concentration value of the interstitial silicon becomes the maximum after the concentration of the vacancy silicon rapidly increases above the equilibrium concentration value while deviating from the denuded zone, that is, A peak (a first peak and a second peak) is formed where the vacancy silicon concentration profile is steeper than the interstitial silicon concentration profile. Next, the concentration of the baked silicon gradually decreases toward the bulk region, and as a result, the concentration profile of the baked silicon between the first peak and the second peak becomes a raised shape.

  On the other hand, vacancy point defects in the wafer are formed as oxygen precipitates by heat treatment repeatedly performed during the manufacture of subsequent semiconductor elements. That is, the vacancy point defect becomes a nucleation center of oxygen precipitates formed by the subsequent heat treatment. Accordingly, when the bakery concentration is high, the concentration of oxygen precipitates formed is also high. For this reason, the shape of the oxygen precipitate concentration profile can be easily inferred through the vacancy concentration profile in the wafer.

There is the following relationship between the vacancy concentration and the oxygen precipitates.
Si (silicon substrate) + xO _i + yV _Si ⇔SiO ₂ (oxygen precipitate) + Si _I (interstitial silicon) + σ

Here, if the concentration of baked silicon V _Si and the initial oxygen concentration O _i are high, the reaction proceeds to the right side, and as a result, the concentration of oxygen precipitates increases. Here, σ is a constant.

  On the other hand, in the embodiment of the present invention, heat treatment was performed after the RTA process of FIG. 5 was completed, and the formation state of oxygen precipitates was measured. Here, in general, the heat treatment is set in a manner similar to the condition in which oxygen precipitates are formed in consideration of the heat treatment step repeatedly performed during the manufacture of the semiconductor element. In this embodiment, for comparison, after the RTA process of FIG. 5 was performed, all wafers were heat-treated in a nitrogen atmosphere for 4 hours at a temperature of 800 ° C. and for 16 hours at a temperature of 1600 ° C. .

  In order to investigate the influence of the mixed gas used in the present invention, the flow rate and the mixing ratio of the mixed gas used during the RTA process of FIG. 5 were changed. FIG. 9 is a schematic diagram showing a vacancy concentration profile after performing the RTA process of FIG. 5 while changing the mixing ratio in an atmosphere of nitrogen gas and argon mixed gas, and FIG. 31 shows the flow rate of the argon and nitrogen mixed gas. FIG. 32 is a graph showing changes in the concentration of oxygen precipitates at the peak due to the mixing ratio of the argon and nitrogen mixed gas.

  In FIG. 9, (a) shows the case where the mixing ratio of nitrogen gas and argon gas is 7: 3, (b) shows the case where it is 5: 5, and (c) is the opposite of (a). Represents the case of 3: 7. Here, it can be seen that as the mixing ratio of nitrogen gas increases, the peak of the vacancy concentration profile gradually moves toward the wafer surface, and the concentration value at the peak also increases. On the other hand, it can be seen that as the mixing ratio of nitrogen gas increases, the denuded zone in which oxygen precipitates are not formed by the subsequent heat treatment also decreases rapidly.

  FIG. 31 shows a mixture of argon and nitrogen under the same conditions as the RTA process of FIG. 5, that is, a temperature increase rate of 50 ° C./second, an annealing temperature of 1250 ° C., an annealing time of 10 seconds, and a temperature decrease rate of 33 ° C./second. The RTA process is performed while changing the gas flow rate to 1/1, 2/2, 3/3, 4/4, and 5/5 liters / minute, and then heat treatment in a nitrogen atmosphere is performed at 800 ° C. for 4 hours. It shows the measurement of the concentration of oxygen precipitates at the peak after 16 hours at 1600 ° C. Here, it can be seen that the concentration of oxygen precipitates increases as the flow rate of the mixed gas increases.

  FIG. 32 shows an argon / nitrogen gas mixing ratio of 3/1, 2.5 / 1.5, 2/2, 1.5 / 2.5 under the same conditions as the RTA process of FIG. Perform RTA process while changing to 1/3 liter / min, then measure oxygen precipitate concentration at peak after heat treatment at 800 ° C for 4 hours and 1600 ° C for 16 hours under nitrogen gas atmosphere It is shown. Here, it can be seen that the concentration of oxygen precipitates increases as the mixing ratio of nitrogen gas increases at the same mixed gas flow rate (4 liters / minute).

  In the present invention, the process conditions of the RTA process, that is, the ratio and flow rate of the mixed gas, the temperature increase rate, the annealing temperature and time, and the temperature decrease rate can be adjusted in various ways. The size of the bakery concentration value in the region, the vacancy concentration value in the bulk region, the size of the denuded zone, and the like are considered.

FIG. 33 is a graph showing changes in the concentration of oxygen precipitates at the peak after performing the RTA process of FIG. 5 while changing the temperature increase rate according to an embodiment of the present invention. Other process conditions were kept constant for comparison. That is, the mixing ratio of nitrogen gas and argon gas was set to 5: 5, the annealing temperature for rapid thermal processing was set to 1250 ° C., the annealing time was set to 10 seconds, and the temperature decrease rate was set to 33 ° C./second. Further, as described above, the subsequent heat treatment was performed on all wafers at 800 ° C. for 4 hours and at 1600 ° C. for 16 hours in a nitrogen atmosphere. The results are shown in Table 1 below.

  As apparent from FIG. 33 and Table 1, the concentration of oxygen precipitates at the peak is not greatly affected by the rate of temperature increase.

FIG. 34 is a graph obtained by measuring the concentration change of oxygen precipitates at the peak after performing the RTA process of FIG. 5 while changing the heat treatment time according to an embodiment of the present invention. Other process conditions were kept constant for comparison. That is, the mixing ratio of nitrogen gas and argon gas was set to 5: 5, the temperature increase rate was set to 50 ° C./second, the annealing temperature for rapid thermal processing was set to 1250 ° C., and the temperature decrease rate was set to 33 ° C./second. Further, as described above, the subsequent heat treatment was performed on all wafers at 800 ° C. for 4 hours and at 1600 ° C. for 16 hours in a nitrogen atmosphere. The results are shown in Table 2 below.

As apparent from FIG. 34 and Table 2, the concentration of oxygen precipitates at the peak is not greatly affected by the annealing time. In order to make the concentration of oxygen precipitates at the peak at least 10 ⁹ / cm ³ , the annealing time of the present invention must be performed for at least 5 seconds.

FIG. 35 is a graph obtained by measuring the concentration change of oxygen precipitates at the peak after performing the RTA process of FIG. 5 while changing the heat treatment temperature according to an embodiment of the present invention. Other process conditions were kept constant for comparison. That is, the mixing ratio of nitrogen gas and argon gas was set to 5: 5, the temperature increase rate was set to 50 ° C./second, the annealing time for rapid heat treatment was set to 10 ° C., and the temperature decrease rate was set to 33 ° C./second. Further, as described above, the subsequent heat treatment was performed on all wafers at 800 ° C. for 4 hours and at 1600 ° C. for 16 hours in a nitrogen atmosphere. The results are shown in Table 2 below.

As is clear from FIG. 35 and Table 3, the concentration of oxygen precipitates at the peak is not greatly affected by the annealing temperature. In order to make the concentration of oxygen precipitates at the peak at least 10 ⁹ / cm ³ , the annealing temperature of the present invention must be at least 1250 ° C. However, the annealing temperature and annealing time are closely related to the concentration of oxygen precipitates. When considering the results of FIG. 34, in order to obtain the same oxygen precipitate concentration, the annealing time can be relatively short when the annealing temperature is high, and conversely, the annealing time is relatively low when the annealing temperature is low. Can be long.

FIG. 36 is a graph obtained by measuring the concentration change of oxygen precipitates at the peak after performing the RTA process of FIG. 5 while changing the temperature decrease rate according to an embodiment of the present invention. Other process conditions were made constant for comparison. That is, the mixing ratio of nitrogen gas and argon gas was set to 5: 5, the rate of temperature increase was set to 50 ° C./second, the annealing temperature for rapid thermal processing was set to 1250 ° C., and the annealing time was set to 10 seconds. Further, as described above, the subsequent heat treatment was performed on all wafers at 800 ° C. for 4 hours and at 1600 ° C. for 16 hours in a nitrogen atmosphere. The results are shown in Table 4 below.

  As is clear from FIG. 36 and Table 4, the concentration of oxygen precipitates at the peak is not greatly affected by the temperature decrease rate. Moreover, it turns out that the density | concentration of the oxygen precipitate in a peak increases a little as the temperature fall rate becomes large.

  FIG. 10 shows a concentration profile of oxygen precipitates at the time of heat treatment after the RTA process according to an embodiment of the present invention. In FIG. 10, a circled number 1 is a nitrogen gas atmosphere, a circled number 2 is a mixed gas atmosphere of nitrogen gas and argon gas, a circled number 3 is a mixed gas atmosphere of nitrogen gas and hydrogen gas, and a circled number 4 is argon gas. The atmosphere and the circled number 5 are concentration profiles of oxygen precipitates formed by performing the RTA process of FIG. 5 in a hydrogen gas atmosphere and then performing a heat treatment.

For comparison, rapid thermal processing was performed at a temperature of 1250 ° C. for 10 seconds, and the subsequent thermal processing was performed at 800 ° C. for 4 hours and 1600 ° C. for 16 hours in a nitrogen atmosphere as described above. I went there. The results are shown in Table 5 below.

  FIG. 11 is a diagram for explaining the COP decomposition process in the vicinity of the surface of the silicon wafer as the RTA process of FIG. 5 is performed under an argon gas atmosphere. Generally, the COP formed during ingot growth by the Czochralski method is a cracked octahedral void, and a silicon oxide film 22 is formed on the inner wall side of the void 20. Under the atmosphere of a gas having an interstitial silicon injection effect on the wafer surface during the RTA process of FIG. 5, such as argon gas or hydrogen gas, a phenomenon occurs in which COP near the surface is decomposed.

The decomposition mechanism will be described in more detail. As the cooling progresses, the initial oxygen concentration O _i contained in the ingot is excessively foamed beyond the solubility at the cooling temperature. Accordingly, even in the wafer, the initial oxygen concentration is excessively bubbled above the solubility curve having a constant concentration (S in FIG. 11). However, on the wafer surface, the initial oxygen concentration is increased by the diffusion to the wafer surface. 11 S) or less. For this reason, in the bulk region of the wafer, the excessively bubbled initial oxygen is supplied into the void 20 to form the silicon oxide film 22, whereas the vicinity of the wafer surface (that is, the solubility line and the initial oxygen concentration line) At a depth of less than or equal to the intersection “T”), the initial oxygen concentration is below the solubility line, so that oxygen is released from the silicon oxide film 20 in the void 20 and silicon is contained in the void due to the interstitial silicon implantation effect. While being supplied, the void gradually becomes smaller and eventually disappears.

  Due to the COP decomposition effect, as described later, the range of wafers to which the rapid thermal process according to the present invention is applied is further expanded. Further, as shown in Table 5, hydrogen gas is more effective for decomposition of COP than argon gas.

  12 to 16 are photographs showing the distribution of oxygen precipitates formed by performing the RTA process of FIG. 5 for each case of FIG. 10 and then performing a heat treatment process. 12 shows a case where nitrogen gas is used, FIG. 13 shows a case where argon gas is used, FIG. 14 shows a case where hydrogen gas is used, and FIG. 15 shows a mixed gas of nitrogen gas and argon gas. FIG. 16 shows a case where a mixed gas of nitrogen gas and hydrogen gas is used. In each figure, the left side is the front side of the wafer, and the right side is the back side of the wafer.

  17 to 21 show the depth of the denuded zone in the vicinity of the front surface of the wafer without oxygen precipitates formed by performing the RTA process of FIG. 5 for each case of FIG. 10 and then performing a heat treatment. It is the photograph shown. 17 shows a case where nitrogen gas is used, FIG. 18 shows a case where argon gas is used, FIG. 19 shows a case where hydrogen gas is used, and FIG. 20 shows a mixed gas of nitrogen gas and argon gas. FIG. 21 shows a case where a mixed gas of nitrogen gas and hydrogen gas is used. As apparent from Table 5, when nitrogen gas is used, a denuded zone is hardly secured.

  22A to 24B are diagrams showing the shape of the COP in the as-grown state and the changed shape after the RTA process of FIG. 5 is performed. In particular, FIGS. 22A and 22B show the case where the RTA process is performed in a nitrogen gas atmosphere, and FIGS. 23A and 23B show the case where the RTA process is performed in a mixed gas atmosphere of nitrogen gas and argon gas. 24A and 24B show the case where the RTA process is performed in a mixed gas atmosphere of nitrogen gas and hydrogen gas. As is apparent from Table 5, COP decomposition does not occur in a nitrogen atmosphere, whereas COP decomposition often occurs in a mixed gas atmosphere of argon gas and hydrogen gas. In particular, it can be seen that COP is completely decomposed in an atmosphere of hydrogen gas. Therefore, it can be seen that if the COP is reduced in the as-grown state, the COP is completely decomposed during the rapid heat treatment of FIG.

[Wafer preparation]
The present invention relates to controlling the distribution of oxygen precipitates formed by the subsequent heat treatment by performing the rapid heat treatment of FIG. 5 on the silicon wafer. The steps that can be performed and the preparation of the wafer to be applied will be described.

  FIG. 25 is a process procedure diagram illustrating a process of preparing a silicon wafer according to an embodiment of the present invention, and particularly illustrates a general wafer ring process after crystal growth (S10). A general semiconductor wafering method is described in Chapter 1 of the textbook “Silicon Processing for the VLSI Era, Volume 1, Process Technology” created by S. Wolf and RN Tauber in 1986. It is disclosed in detail on pages 1-35. Referring to FIG. 25, when the wafer ringing process of the semiconductor wafer is briefly examined, after the crystal growth process (S10) for forming the ingot using the Czochralski puller, the cutting process for cutting the ingot into a wafer ( S12) is performed. Next, an etching step (S14) is performed in which each cut ingot is rounded or the surface is etched. Next, after the first cleaning process (S16) is performed on the surface, a donor keying process (S18) is performed. Next, a polishing process (S20) and a second cleaning process (S22) for polishing the front surface of the wafer on which the semiconductor elements are formed are performed, and finally a wafer packaging process (S24) is performed.

  The RTA process of FIG. 5 of the present invention is performed in the donor keying step (S18). Of course, the heat treatment step of the present invention may be performed separately, but it is preferably performed in the donor keying step from the viewpoint of cost saving. In general, donor keying refers to the fact that oxygen contained in a silicon ingot exists in the form of ions during the manufacture of a subsequent semiconductor device and may act as a donor for implanted ions. In order to prevent this, it refers to a process in which heat treatment is performed in advance during wafer ring to form oxygen precipitates. This is typically done at 700 ° C. for 30 seconds using RTA equipment.

  FIG. 27 is a schematic view showing a conventional Czochralski puller as an apparatus for performing the crystal growth step (S10). Referring to this, the Czochralski puller 100 includes a furnace, a crystal pulling mechanism, an environmental controller, and a control system using a computer. The Czochralski puller is generally called a hot zone. The hot zone also includes a heater 104, a quartz crucible 106, a graphite susceptor 108, and a rotating shaft 110 that rotates in a first direction 112 as shown.

  The jacket or cooling port 132 is cooled by external cooling means such as cooling. A heat shield 114 provides additional heat distribution. Also, the heating pack 102 is filled with a heat absorbing material 116 and provides additional heat distribution.

  As shown, the crystal pulling mechanism includes a crystal pulling shaft 120 that is rotatable in a second direction 122 that is opposite to the first direction 112. The crystal pulling shaft 120 includes a crystal holder 120a at its end. The crystal holder 120 a holds the seed crystal 124 and is pulled up from the melt 126 in the crucible 106 to form an ingot 128.

  The environmental control system includes a chamber seal 130, a cooling jacket 132, and other flow controllers and evacuation systems not shown. A computer based control system is used to control the heater, puller and other electrical and mechanical elements.

  In order to grow a single crystal silicon ingot, the seed crystal 124 comes into contact with the silicon melt 126 and is gradually pulled up in the axial direction (upper side). The cooling and solidification of the silicon melt 126 as single crystal silicon occurs at the boundary 131 between the ingot 128 and the melt 126. As shown in FIG. 27, the boundary 131 is raised with respect to the melt 126.

  On the other hand, silicon wafers that can obtain the concentration profile of oxygen precipitates controlled as shown in FIG. 4 using the rapid thermal processing process according to the present invention can be roughly classified into three types. That is, a defect-free perfect wafer in which interstitial agglomerates and vacancy agglomerates are not formed over the entire radial direction of the wafer, and vacancy agglomerates are formed only in a vacancy-rich region within a certain radius from the center of the wafer. The semi-perfect wafer where no interstitial agglomeration and vacancy agglomerate exist outside the bakery region, and the wafer where there is no interstitial agglomeration over the entire wafer and only the vacancy agglomeration exists. It is. However, the wafer to which the present invention is applied is not necessarily limited to this, and any wafer that can apply the principle of the present invention can be applied. That is, as described above, the present invention is to perform the RTA process of FIG. 5 on a predetermined silicon wafer and then perform a heat treatment to obtain a concentration profile of oxygen precipitates as shown in FIG. In addition, the COP may be a silicon wafer that exists in the bulk region of the wafer but does not exist in the denuded zone.

  In order to prevent defects in silicon wafers, various studies have been conducted to produce high-purity ingots during crystal growth. In particular, techniques for controlling the seed crystal pulling rate and the temperature gradient in the hot zone structure are well known. "The Mechanizm ofSwirl Defects Formation in Silicon" by Volonkov [Journal of Crystal Growth, Vol. 59, 1982, pp. 625-643] discloses a technique relating to the control of the ingot pulling speed (V) and the temperature gradient (G) at the contact surface of the ingot-melt. Presented at the Second International Symposium on Advanced Science and Technology of Silicon Material, which was applied by this inventor and was held by the inventor from November 25 to 29, 1996 for improved science and technology. According to the published paper “Effect of Crystal Defects on Devices Characteristics”, if the ratio of V to G (hereinafter referred to as V / G) is above a critical point, a vacancy-rich region is formed. An interstitial-rich region is formed.

FIG. 26 is a conceptual diagram showing a relative point defect distribution and V / G relationship in a silicon ingot. Referring to this, when V / G is equal to or higher than the critical point (V / G ^* ) during ingot growth, a vacancy-rich region is formed, and when V / G is equal to or higher than the critical vacancy concentration (Cv ^* ), a vacancy agglomerate is formed. When the critical interstitial concentration (CI ^* ) is exceeded, an interstitial agglomeration is formed. In FIG. 26, (V / G) _B ^* represents a B-band boundary that is a ring related to interstitial silicon, and (V / G) _P ^* represents O.D. S. It represents the boundary of the P-band that is the F-ring.

The wafer to which the present invention is applied corresponds to a defect-free perfect wafer in which V / G exists between the B-band and P-band during ingot growth, a semi-perfect wafer including the P-band, and a critical vacancy concentration. Yes (V / G) ^{* A} wafer or the like in which a vacancy agglomerate is formed over the entire wafer.

  On the other hand, regarding perfect wafers and semi-perfect wafers to which the present invention is applied, U.S. patent application Ser. No. 08 / 989,591 filed by the present inventor and the corresponding CIP application No. 09 / 320,210. And 09 / 320,102. In addition, this is a reference combined with the application, and a detailed description thereof is omitted.

  FIG. 28 is a schematic view showing the Czochralski puller invented by the present inventor and disclosed in the CIP application, and is an improvement of the heat shield 214 compared to FIG. Referring to FIG. 28, the Czochralski puller 200 includes a furnace, a crystal pulling mechanism, an environmental controller, and a control system using a computer. The hot zone furnace includes a heater 204, a crucible 206, a susceptor 208, and a rotating shaft 210 that rotates in a first direction 212 as shown. A cooling jacket 232 and a heat shield 214 provide additional heat distribution. Also, the heating pack 202 is filled with a heat absorbing material 216 to provide additional heat distribution.

  As shown, the crystal pulling mechanism includes a crystal pulling shaft 220 that is rotatable in a second direction 222 that is opposite to the first direction 212. The crystal pulling shaft 220 includes a crystal holder 220a at its end. The crystal holder 220 a holds the seed crystal 224 and is pulled up from the melt 226 in the crucible 206 to form an ingot 228.

  The environmental control system includes a chamber seal 230, a cooling jacket 232, and other flow controllers and evacuation systems not shown. A computer based control system is used to control the heater, puller and other electrical and mechanical elements. In order to grow a single crystal silicon ingot, the seed crystal 224 comes into contact with the silicon melt 226 and is gradually pulled up in the axial direction (upper side). Cooling and solidification of the silicon melt 226 as single crystal silicon occurs at the boundary 231 between the ingot 228 and the melt 226. This further includes a heat shield housing 234 as compared with FIG. 27, so that the V / G can be adjusted more accurately.

  FIG. 29 is a schematic view showing an improved Czochralski puller according to an embodiment of the present invention, and FIG. 30 shows an improved main part thereof. Here, the description of the same components as those in FIG. 28 is omitted. That is, as shown in FIG. 30, the improvement is that the shape of the heat shut-off housing 300 is changed and a heat shut-off valve 360 is further provided. The heat shield housing 300 has a trapezoidal shape rotated by 90 °, and includes a vertical inner heat shield housing wall 310 and an outer heat shield housing wall 330, and a space between the inner heat shield housing wall 310 and the outer heat shield housing wall 330. A heat shield housing lid 340 that is inclined upward in the outward direction and connects between the internal heat shield housing wall 310 and the external heat shield housing wall 330 and includes a heat shield housing bottom 320 that is inclined downward in the outward direction. It has a ring shape.

  The ring-shaped heat shield housing 300 is filled with a heat absorbing material capable of absorbing heat, and the heat shield housing 300 is made of carbon ferrite.

  A heat shield plate 360 is provided between the heat shield housing cover 340 and the cooling jacket 232 of the heat shield housing 300 to surround the ingot to be pulled up. The heat shield housing 300 is attached to the heating pack 202 by a support member 350. Fixed to the upper side.

  The structure of the Czochralski puller shown in FIG. 29 can basically increase the cooling rate of the grown ingot. In general, the size of the void in the crystal-grown ingot is proportional to the square root of the initial vacancy concentration formed at the contact surface between the silicon melt and the ingot, but inversely proportional to the square root of the cooling rate of the ingot. To do. On the other hand, as described with reference to FIG. 11, if the void existing in the ingot is formed below a certain size, even if the void is formed in the ingot during crystal growth, the rapid heat treatment process of the present invention is used. There are no voids in the nude zone.

  Therefore, in order to reduce the void formed in the ingot according to the object of the present invention, it is necessary to increase the cooling rate of the ingot. On the other hand, when the cooling rate of the ingot increases, the temperature gradient (Gc) increases along the central axis of the ingot to be pulled up. When V / G is set to a constant value so as to have a predetermined defect distribution, the ingot pulling rate is increased. Also gets higher.

  In the present invention, the temperature of the ingot shaft is at least 1.4 ° until the temperature of the ingot shaft reaches a certain temperature corresponding to the growth stage of the ingot from the temperature of the ingot shaft at the ingot-melt boundary. k / min or more, the lengths “a” and “c” of the inner heat shielding housing wall 310 and the outer heat shielding housing wall 330 of the heat shielding housing 300, the inclination angle β of the heat shielding housing lid 340, Inclination angle α of heat insulation housing bottom 320, distance “d” from ingot 228 to internal heat insulation housing wall 310, distance “f” from crucible 206 to external heat insulation housing wall 330, internal heat insulation housing wall The distance “e” from 310 to the external heat isolation housing wall 330 and the arrangement of the heat isolation valves 360 are selected.

  In the puller of FIG. 29, since the cooling rate of the ingot to be grown is large, the pulling rate can be extremely high, for example, about 0.50 mm / min to 1.00 mm / min. As a result, the productivity of the ingot is improved. The In addition, it is possible to further secure a process margin when growing an ingot for the perfect wafer or semi-perfect wafer manufactured in FIG.

It is sectional drawing which showed the structure of the conventional MOS transistor formed in the surface vicinity of a silicon wafer. It is the figure which showed the density | concentration profile of the oxygen precipitate with respect to the conventional silicon wafer. It is the figure which showed the density | concentration profile of the oxygen precipitate with respect to the other conventional silicon wafer. FIG. 3 is a diagram schematically illustrating a concentration profile of oxygen precipitates on a silicon wafer according to an embodiment of the present invention. It is a time chart of the RTA process performed by one Embodiment of this invention. It is the figure which showed the density | concentration profile of the point defect after performing the RTA process of FIG. 5 in nitrogen gas atmosphere. It is the figure which showed the density | concentration profile of the point defect after performing the RTA process of FIG. 5 in argon gas atmosphere. It is the figure which showed the density | concentration profile of the point defect after performing the RTA process of FIG. 5 in hydrogen gas atmosphere. It is the figure which showed the bakery density | concentration profile after performing the RTA process of FIG. 5, changing mixing ratio in the mixed gas atmosphere of nitrogen gas and argon gas. FIG. 5 is a diagram showing a concentration profile of oxygen precipitates by a subsequent heat treatment after performing an RTA process according to the present invention. It is a figure for demonstrating the decomposition | disassembly process of COP in the surface vicinity of a silicon wafer according to performing the RTA process of FIG. 5 in argon gas atmosphere. 6 is a photograph showing a distribution of oxygen precipitates formed by subsequent heat treatment after performing the RTA process of FIG. 5 under a nitrogen gas atmosphere. 6 is a photograph showing a distribution of oxygen precipitates formed by subsequent heat treatment after performing the RTA process of FIG. 5 in an argon gas atmosphere. 6 is a photograph showing a distribution of oxygen precipitates formed by subsequent heat treatment after performing the RTA process of FIG. 5 in a hydrogen gas atmosphere. 6 is a photograph showing a distribution of oxygen precipitates formed by subsequent heat treatment after performing the RTA process of FIG. 5 in a mixed gas atmosphere of nitrogen gas and argon gas. 6 is a photograph showing a distribution of oxygen precipitates formed by subsequent heat treatment after performing the RTA process of FIG. 5 in a mixed gas atmosphere of nitrogen gas and hydrogen gas. 6 is a photograph showing the depth of a denuded zone formed by subsequent heat treatment after performing the RTA process of FIG. 5 in a nitrogen gas atmosphere. 6 is a photograph showing the depth of a denuded zone formed by subsequent heat treatment after performing the RTA process of FIG. 5 in an argon gas atmosphere. 6 is a photograph showing the depth of a denuded zone formed by subsequent heat treatment after performing the RTA process of FIG. 5 in a hydrogen gas atmosphere. FIG. 6 is a photograph showing the depth of a denuded zone formed by a subsequent subsequent heat treatment after performing the RTA process of FIG. 5 in a mixed gas atmosphere of nitrogen gas and argon gas. 6 is a photograph showing the depth of a denuded zone formed by subsequent heat treatment after performing the RTA process of FIG. 5 in a mixed gas atmosphere of nitrogen gas and hydrogen gas. 22A is a photograph showing the shape of the COP in the as-grown state, and FIG. 22B is a photograph showing the changed shape after the RTA process of FIG. 5 is performed in a nitrogen gas atmosphere. . 23A is a photograph showing the shape of the COP in the as-grown state, and FIG. 23B is a changed shape after the RTA process of FIG. 5 is performed in a mixed gas atmosphere of nitrogen gas and argon gas. It is the photograph which showed. FIG. 24A is a photograph showing the shape of the COP in the as-grown state, and FIG. 24B is a changed shape after the RTA process of FIG. 5 is performed in a mixed gas atmosphere of nitrogen gas and hydrogen gas. It is the photograph which showed. It is the process sequence figure showing the process course by one embodiment of the present invention. It is the conceptual diagram which showed the relative point defect distribution and V / G relationship in a silicon ingot. It is the schematic which showed the conventional Czochralski puller. It is the schematic which showed the conventional Czochralski puller invented by this inventor. 1 is a schematic diagram illustrating a Czochralski puller improved according to an embodiment of the present invention. It is the figure which showed the principal part of the Czochralski puller of FIG. It is the graph which measured the density | concentration change of the oxygen precipitate in the peak after performing the RTA process of FIG. 5, changing the flow volume of nitrogen gas and argon gas by one Embodiment of this invention. It is the graph which measured the density | concentration change of the oxygen precipitate in the peak after performing the RTA process of FIG. 5, changing the mixing ratio of nitrogen gas and argon gas by one Embodiment of this invention. It is the graph which measured the density | concentration change of the oxygen precipitate in the peak after performing the RTA process of FIG. 5, changing the temperature increase rate by one Embodiment of this invention. It is the graph which measured the density | concentration change of the oxygen precipitate in the peak after performing the RTA process of FIG. 5, changing heat processing time by one Embodiment of this invention. It is the graph which measured the density | concentration change of the oxygen precipitate in the peak after performing the RTA process of FIG. 5, changing heat processing temperature by one Embodiment of this invention. It is the graph which measured the density | concentration change of the oxygen precipitate in the peak after performing the RTA process of FIG. 5, changing the temperature fall rate by one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Silicon substrate 10a Bulk region 10b Denuded zone 12 Source region 14 Drain region 16 Gate insulating film 18 Gate electrode 20 Void 22 Silicon oxide film 100, 200 Czochralski puller 102, 202 Heat pack 104, 204 Heater 106, 206 Crucible 108 , 208 Susceptor 110, 210 Rotating shaft 112, 212 First direction 114, 214 Heat shield 116, 216 Heat absorbing material 120, 220 Crystal pulling shaft 120 a, 220 a Crystal holder 122, 222 Second direction 124, 224 Seed crystal 126, 226 Melt 128, 228 Ingot 130, 230 Chamber seal 131, 231 Ingot-melt interface 132, 232 Cooling jacket 234, 300 Heat shield housing 310 Internal heat shield housing wall 20 heat shield housing bottom 330 outer heat shield housing wall 340 thermal shield housing lid 350 supporting member 360 thermal shut-off valve

Claims (9)

Preparing a silicon wafer;
Oxygen precipitates grow during the heat treatment subsequent to the rapid heat treatment by performing rapid heat treatment on the wafer surface in a mixed gas atmosphere of a gas having a vacancy injection effect and a gas having an interstitial silicon injection effect. A nucleation center that serves as a place to generate is generated, and a concentration profile of the nucleation center generated from the front surface to the back surface of the wafer is generated at a predetermined depth from the front surface and the back surface, respectively. Showing a peak, maintained below the critical value before reaching the first peak and the second peak respectively from the front surface and the back surface, and making the concentration profile of the nucleation center concave in the bulk region between the first peak and the second peak And a rapid heat treatment step,
The step of preparing the silicon wafer includes
High enough to prevent interstitial agglomeration, but low enough ingot pulling speed profile to limit vacancy agglomeration along the ingot axial direction into the vacancy-rich region. Pulling the ingot from the object,
And a step of cutting the ingot in a radial direction. Preparing a silicon wafer;
Oxygen precipitates grow during the heat treatment subsequent to the rapid heat treatment by performing rapid heat treatment on the wafer surface in a mixed gas atmosphere of a gas having a vacancy injection effect and a gas having an interstitial silicon injection effect. A nucleation center that serves as a place to generate is generated, and a concentration profile of the nucleation center generated from the front surface to the back surface of the wafer is generated at a predetermined depth from the front surface and the back surface, respectively. Showing a peak, maintained below the critical value before reaching the first peak and the second peak respectively from the front surface and the back surface, and making the concentration profile of the nucleation center concave in the bulk region between the first peak and the second peak And a rapid heat treatment step,
The step of preparing the silicon wafer includes
Its central bakery-rich region containing vacancy agglomerates and a defect-free region between said vacancy-rich region and wafer edge including interstitial point defects but no vacancy agglomerates and interstitial agglomerates Pulling the ingot from the silicon melt in the hot zone furnace with a pulling speed profile of the ingot producing a semi-perfect wafer with
And a step of cutting the ingot in a radial direction. Preparing a silicon wafer;
Oxygen precipitates grow during the heat treatment subsequent to the rapid heat treatment by performing rapid heat treatment on the wafer surface in a mixed gas atmosphere of a gas having a vacancy injection effect and a gas having an interstitial silicon injection effect. A nucleation center that serves as a place to generate is generated, and a concentration profile of the nucleation center generated from the front surface to the back surface of the wafer is generated at a predetermined depth from the front surface and the back surface, respectively. Showing a peak, maintained below the critical value before reaching the first peak and the second peak respectively from the front surface and the back surface, and making the concentration profile of the nucleation center concave in the bulk region between the first peak and the second peak And a rapid heat treatment step,
The step of preparing the silicon wafer includes
Pulling the ingot from the silicon melt in the hot zone furnace at a sufficiently high ingot pulling speed profile to prevent interstitial agglomeration but low enough to prevent bakery agglomeration;
And a step of cutting the ingot in a radial direction. Preparing a silicon wafer;
Oxygen precipitates grow during the heat treatment subsequent to the rapid heat treatment by performing rapid heat treatment on the wafer surface in a mixed gas atmosphere of a gas having a vacancy injection effect and a gas having an interstitial silicon injection effect. A nucleation center that serves as a place to generate is generated, and a concentration profile of the nucleation center generated from the front surface to the back surface of the wafer is generated at a predetermined depth from the front surface and the back surface, respectively. Showing a peak, maintained below the critical value before reaching the first peak and the second peak respectively from the front surface and the back surface, and making the concentration profile of the nucleation center concave in the bulk region between the first peak and the second peak And a rapid heat treatment step,
The step of preparing the silicon wafer includes
Pulling the ingot from the silicon melt in the hot zone furnace with a pulling speed profile of the ingot that produces perfect wafers that contain point defects but no interstitial and vacancy agglomerates;
And a step of cutting the ingot in a radial direction. Preparing a silicon wafer;
Oxygen precipitates grow during the heat treatment subsequent to the rapid heat treatment by performing rapid heat treatment on the wafer surface in a mixed gas atmosphere of a gas having a vacancy injection effect and a gas having an interstitial silicon injection effect. A nucleation center that serves as a place to generate is generated, and a concentration profile of the nucleation center generated from the front surface to the back surface of the wafer is generated at a predetermined depth from the front surface and the back surface, respectively. Showing a peak, maintained below the critical value before reaching the first peak and the second peak respectively from the front surface and the back surface, and making the concentration profile of the nucleation center concave in the bulk region between the first peak and the second peak And a rapid heat treatment step,
The step of preparing the silicon wafer includes
Pulling up the ingot from the silicon melt in the hot zone furnace with a sufficiently high ingot pulling speed profile so that the bakery agglomerate can form entirely along the radial direction of the ingot without forming interstitial agglomerates;
And a step of cutting the ingot in a radial direction. 6. The method for producing a silicon wafer according to claim 1, wherein the size of bakery agglomerates formed in the silicon wafer is raised to 0.2 [mu] m or less after the ingot is pulled up. The method for producing a silicon wafer according to claim 1, 2 or 5, wherein after the ingot is pulled up, a size of a vacancy agglomerate formed in the silicon wafer is preferably 0.2 μm or less. . 6. The method according to claim 1, 2, or 5, wherein, in the step of pulling up the ingot, a cooling rate of a central axis of the ingot within a temperature range of a growth stage of the ingot is at least 1.4 ° K / min. Silicon wafer manufacturing method. The method for manufacturing a silicon wafer according to claim 1, 2 or 5, wherein in the step of pulling up the ingot, a pulling speed of the ingot is in a range of 0.5 to 1.0 mm / min.