JP4826993B2 - Method for producing p-type silicon single crystal wafer - Google Patents

Description

  The present invention relates to a method of manufacturing a p-type silicon single crystal wafer that can effectively remove heavy metal impurities that adversely affect device operation, particularly Cu.

  As the density and integration of semiconductor devices increase, stabilization of semiconductor device operations is further desired. It is heavy metal impurities present in the silicon single crystal wafer and the semiconductor device that hinder this stabilization. For example, heavy metal impurities such as iron and copper, which enter the silicon single crystal wafer and the semiconductor device during the manufacturing process, precipitate as a solid solution or a compound at a lattice position or an interstitial position in Si. As a result, the formation and disappearance centers of minority carriers, the increase in the leakage current of the pn junction, the shortening of the excess carrier lifetime, and the like occur, and the electrical characteristics of the semiconductor device deteriorate.

  For example, in the MOS type memory device, the generated excess electrons or excess holes diffuse in the silicon substrate, so that the charge accumulated in the charge accumulation cell decreases, and when the accumulated charge becomes below the critical charge, The state of the memory cell is inverted from 1 to 0 and the stored information is lost.

  In the CCD, excess carriers generated from the generation / annihilation center are detected as signal charges in the same manner as excess carriers due to incident light. As a result, the excess carriers generated from the generation / annihilation center become an abnormally strong signal (white scratch), and the image quality is deteriorated.

  In the bipolar device, the generation / annihilation center increases the leakage current of the pn junction. In addition, since excess carriers generated in the base region are transmitted to the outside as an abnormal signal, inconveniences such as an increase in low-frequency noise occur. As described above, heavy metal impurity contamination causes deterioration of the electrical characteristics of the device and reduces the production yield of LSI. Conventionally, two countermeasures have been taken against such contaminants.

  One is to eliminate pollution sources as much as possible. Contamination sources include chemicals such as hydrofluoric acid, nitric acid, hydrochloric acid, hydrogen peroxide, ammonium fluoride, sulfuric acid, ultrapure water, dust in clean rooms, workers, resists, fine particles generated in various fine processing equipment, etc. There is no time for enumeration. The technology for improving the purity and reducing the particulate contamination has been developed as an ultra-cleaning technology.

  However, even if the development of ultra-clean technology such as the production environment of VLSI, the cleaning of materials used, and the reduction of contamination from production equipment is advanced, hundreds of VLSI manufacturing processes are perfectly managed with the required cleanliness. It is difficult. Contamination has been occurring with a certain probability statistically. In this way, contaminants are managed in all steps of the VLSI manufacturing process. However, there is a high possibility that contamination will occur with the increase in the number of manufacturing processes, and contamination in some processes is unavoidable. It is not.

  Another countermeasure is to remove contaminants such as heavy metal impurities from the active region of the device, that is, gettering. As a technique for forming a gettering region for performing the gettering, there are an IG (Internal Gettering) method and an EG (External Gettering) method.

  The IG method is a technique for precipitating oxygen atoms contained in a silicon single crystal produced by the CZ method, and gettering heavy metal impurities to the strain around the precipitate, for example, by low-temperature heat treatment at 650 ° C. to 750 ° C. After the formation of oxygen precipitation nuclei, oxygen is precipitated by high-temperature heat treatment at 1000 ° C. to 1100 ° C., and heavy metal impurities are gettered to the strain around the oxygen precipitate. Further, in order to prevent the formation of precipitates in the active region of the device in the vicinity of the surface, a high temperature heat treatment at about 1200 ° C. is often performed before the low temperature heat treatment. Usually, the low temperature heat treatment is performed in the wafer manufacturing process, and the high temperature heat treatment is performed in the VLSI manufacturing process.

On the other hand, the EG method includes a wafer backside damage gettering method and a so-called PBS (Poly Back Seal) method. In the wafer backside damage gettering method, mechanical strain is intentionally formed on the backside of the wafer. As a result, oxidation induced stacking faults are generated by the heat treatment in the wafer oxidation process with the mechanical strain as a nucleus, and heavy metal impurities are deposited there. The mechanical strain can be formed, for example, by spraying SiO ₂ fine powder on the back surface of the wafer. Since the oxidation-induced stacking fault grows most rapidly in the oxidation process at about 1100 ° C., this gettering needs to pass through a high-temperature heat treatment. The PBS method is a method in which a polycrystalline silicon film is formed on the back surface of a silicon single crystal wafer, and impurities are captured in the distortion of the polycrystalline grain boundary.

However, the gettering has the following problems. First, the wafer rear surface useless - Jigettaringu is for blowing SiO ₂ fine powder back surface of the wafer, elaborate SiO ₂ is about the wafer surface, there is a problem that contaminate the wafer surface which is an element formation region. Further, as the miniaturization of the VLSI progresses, the distance between the elements becomes shorter. Therefore, local doping for pn junction formation, Vth control, etc. by phosphorus, arsenic, boron, etc. is 1000 ° C. or less, for example, 800 It is necessary to perform low-temperature heat treatment at about 850 ° C. or high-speed heating / cooling for a short time of several seconds to several minutes even at 1000 ° C. or higher. However, wafer backside damage gettering requires high-temperature heat treatment of about 1000 ° C. or higher for growth of oxidation-induced stacking faults, and if this high-temperature heat treatment is not passed, gettering at a lower temperature is sufficient to remove contaminants. There was a problem that could not be removed.

  And in the situation where such low-temperature heat treatment and high-speed heating and cooling treatment in a short time of several seconds to several minutes even at 1000 ° C. or more have become the mainstream in the device manufacturing process, only the heavy metal impurities are moved to the trapping layer. EG methods such as wafer backside damage gettering and PBS method, which have insufficient diffusion time and require impurities to diffuse to the backside, are becoming disadvantageous. The IG method is advantageous over the EG method because it does not require long-distance diffusion, but it is difficult to form oxygen precipitates by low-temperature and short-time heat treatment. Techniques have been started to increase gettering capability by using a placed wafer. In fact, it has been confirmed that such wafers exhibit a higher heavy metal impurity gettering capability that is more stable than conventional wafers.

However, there are metal impurities in which the IG method is not very effective inside the p-type silicon single crystal wafer. As an example, copper (Cu) will be described as a model. Cu inside the p-type silicon single crystal wafer is in a solid solution with a positive charge, but when gettering is performed by the IG method, it forms a silicide precipitate called Cu ₃ Si around the oxygen precipitate. A high IG capability cannot be expected without changing and further collecting and growing Cu atoms in the silicide precipitate. The mechanism of changing not only Cu but also other metal impurity IGs from solid solution atoms to the form of precipitates is the same. Generally, the IG ability is determined by the growth rate of the target metal impurity precipitates. Good to say. However, in the case of Cu, since the silicide precipitate of Cu ₃ Si is also positively charged, even if a small Cu ₃ Si is formed, it is not possible to expect the growth of the precipitate that greatly contributes to enhancing the IG capability thereafter. . This is because repulsive force acts on both the solid solution Cu atom and the Cu ₃ Si silicide precipitate having the same charge. In such a case, an EG method such as PBS must be applied to Cu gettering.
JP-A-5-136153

  The present invention has been made in view of such problems, and a method for manufacturing a p-type silicon single crystal wafer capable of gettering heavy metal impurities that are difficult to getter by the IG method inside the p-type silicon single crystal wafer. The purpose is to provide.

  As a result of examining the gettering of heavy metal impurities existing inside the p-type silicon single crystal wafer, the present inventor has found that the heavy metal impurities and the silicide precipitates have the same type of charge inside the p-type silicon single crystal wafer. Even if an attempt is made to get the heavy metal impurity to the silicide precipitate of the heavy metal impurity trapped in the strain around the oxygen precipitate by the IG method, the silicide precipitate of the heavy metal impurity is caused by the repulsive force acting between the heavy metal impurity and the silicide precipitate. As a result, it was found that precipitation into the metal hardly progresses and that there is almost no gettering effect, particularly in the case of Cu. Further, the present inventor has found that these heavy metal impurities including Cu become neutral charges inside the n-type silicon single crystal wafer, and no repulsive force acts on the silicide precipitates. It was also found that precipitation progressed and a gettering effect was obtained. From these findings, heavy metal impurities inside the p-type silicon single crystal wafer that are hardly gettered even when the IG method is performed are obtained by oxygen precipitates formed inside the n-type silicon film formed on the back surface of the p-type silicon single crystal wafer. The present invention was completed by conceiving that it can be ringed.

  In order to solve the above-mentioned problems, the present p-type silicon single crystal wafer includes a p-type silicon single crystal wafer main body and an n-type silicon film formed on the back surface of the wafer main body, and the n-type silicon film has an internal structure. The oxygen precipitates are formed on the p-type silicon single crystal wafer main body, and the oxygen precipitates getter the metal impurities.

In this way, if an n-type silicon film is provided on the back surface of the p-type silicon single crystal wafer body and oxygen precipitates are formed inside the silicon film, heavy metal impurities that are difficult to getter inside the p-type silicon single crystal wafer body. However, it can be effectively removed from the device active region. As in the case described above, Cu is taken as an example. Inside the n-type silicon film, since Cu becomes a neutral charge and dissolves, the repulsive force that has hindered the growth of precipitates does not work. Easily deposits on silicide deposits such as Cu ₃ Si. Thereby, Cu is effectively and completely removed from the device active region.

  The n-type silicon film is preferably formed by an epitaxial growth method. The n-type silicon film may be formed by a CVD method. As described above, when epitaxial growth or CVD is used for forming the n-type silicon film, the n-type silicon film can be easily formed on the back surface of the p-type silicon single crystal wafer body while doping n-type impurities such as phosphorus, antimony, and arsenic. Since it can form, it is suitable.

  In this p-type silicon single crystal wafer, oxygen is ion-implanted into the n-type silicon film, and then the p-type silicon single crystal wafer with the n-type silicon film having the n-type silicon film formed on the back surface is subjected to heat treatment. It is preferable to form oxygen precipitates inside the n-type silicon film and the p-type silicon single crystal wafer. As described above, oxygen is ion-implanted into the n-type silicon film formed on the back surface of the p-type silicon single crystal wafer body, and the n-type silicon film-attached p-type silicon with the n-type silicon film formed on the back surface is formed. If oxygen precipitates are formed inside the n-type silicon film and the p-type silicon single crystal wafer body by heat-treating the single crystal wafer, the oxygen precipitates for gettering heavy metal impurities are formed in the p-type silicon single crystal wafer body. Since it is formed inside and inside the n-type silicon film, heavy metal impurities can be gettered more effectively.

  In the present p-type silicon single crystal wafer, a non-doped silicon film is grown on the back surface of the p-type silicon single crystal wafer body, and n-type impurities and oxygen are ion-implanted into the silicon film. An n-type silicon film is formed by heat-treating a p-type silicon single crystal wafer with a silicon film formed on the substrate, and oxygen precipitates are formed inside the n-type silicon film and the p-type silicon single crystal wafer body. May be. Furthermore, in the p-type silicon single crystal wafer of the present invention, a non-doped silicon film is grown on the back surface of the main body of the p-type silicon single crystal wafer, oxygen is ion-implanted into the silicon film, and n-type is formed on the silicon film surface. Then, an n-type silicon film is formed by heat-treating a p-type silicon single crystal wafer with a silicon film on which the n-type silicon film is formed on the back surface, and an n-type silicon film and the p-type silicon film are formed. Oxygen precipitates may be formed inside the silicon single crystal wafer body.

  In the present p-type silicon single crystal wafer, after the metal impurity is gettered inside the n-type silicon film, the n-type silicon film formed on the back surface of the p-type silicon single crystal wafer body is removed. Is preferred. In this way, removing the n-type silicon film gettered with the metal impurity can permanently remove the gettered metal impurity, which is the most ideal getter method.

  At this time, it is more effective that the metal impurity gettered inside the n-type silicon film is Cu. Conventionally, Cu, which is a high-speed diffusion species inside a silicon single crystal wafer, has a large diffusion coefficient, so that it easily diffuses to the element active region, and is one of the major factors that deteriorate the electrical characteristics of the semiconductor device formed in the element active region. It was one. As described above, if the n-type silicon film obtained by gettering Cu is removed, Cu can be completely removed from the p-type silicon single crystal wafer. Therefore, a p-type silicon single crystal wafer having a higher yield of semiconductor devices can be obtained. Can be provided. In this p-type silicon single crystal wafer, the n-type silicon film is on the back surface of the main body of the p-type silicon single crystal wafer, so it is farthest from the element active region, but Cu is the fastest diffusion species. Therefore, even in the low-temperature and short-time heat treatment step, the diffusion to the back surface is sufficiently possible and effective gettering can be performed.

The first aspect of the method for producing a p-type silicon single crystal wafer of the present invention is:
a step of preparing a p-type silicon single crystal wafer main body, a step of forming an n-type silicon film on the back surface of the p-type silicon single crystal wafer main body to form a p-type silicon single crystal wafer with an n-type silicon film, and the n-type Forming an oxygen precipitate inside the silicon film and the p-type silicon single crystal wafer main body, and forming a metal impurity inside the n-type silicon film and then forming the back surface of the p-type silicon single crystal wafer main body; Removing the n-type silicon film formed,
The step of growing the n-type silicon film on the back surface of the p-type silicon single crystal wafer body is a step of growing the n-type silicon single crystal film by an epitaxial process.
The step of forming the oxygen precipitate includes a step of ion-implanting oxygen into the n-type silicon film, and a heat treatment of the p-type silicon single crystal wafer with the n-type silicon film having the n-type silicon film formed on the back surface. And a process.
If it is the manufacturing method of such a p-type silicon single crystal wafer, this p-type silicon single crystal wafer can be manufactured easily.

  At this time, the step of forming the n-type silicon film is preferably an epitaxial step or a CVD step. Thus, if an epitaxial process or a CVD process is used as a process for forming an n-type silicon film, an n-type silicon film can be easily converted into a p-type silicon single crystal wafer while doping an n-type impurity such as phosphorus, antimony or arsenic. It can be formed on the back surface of the main body.

  As the step of forming the oxygen precipitates, a step of ion-implanting oxygen into the n-type silicon film, and a heat treatment of the p-type silicon single crystal wafer with the n-type silicon film having the n-type silicon film formed on the back surface are heat-treated. It is preferable to include a process. If such an oxygen precipitate formation step is included in the first aspect of the method for producing a p-type silicon single crystal wafer of the present invention, oxygen precipitates are present in both the n-type silicon film and the p-type silicon single crystal wafer body. As a result, Cu is not only gettered inside the n-type silicon film, but also other heavy metal impurities are gettered inside the p-type silicon single crystal wafer body. It can be removed from the device active region.

The second aspect of the method for producing a p-type silicon single crystal wafer of the present invention is:
a step of preparing a p-type silicon single crystal wafer main body, a step of growing a non-doped silicon film on the back surface of the p-type silicon single crystal wafer main body, a step of ion-implanting n-type impurities into the silicon film, and the silicon A step of ion-implanting oxygen into the film; and heat-treating a p-type silicon single crystal wafer with a silicon film on which the silicon film is formed on the back surface to form an n-type silicon film and the n-type silicon film and the p-type A step of forming oxygen precipitates inside the silicon single crystal wafer body; and the n-type silicon formed on the back surface of the p-type silicon single crystal wafer body after gettering metal impurities inside the n-type silicon film. Removing the film, and
The step of growing the non-doped silicon film on the back surface of the p-type silicon single crystal wafer body is a step of growing a silicon single crystal film by an epitaxial process.

The third aspect of the method for producing a p-type silicon single crystal wafer of the present invention is:
a step of preparing a p-type silicon single crystal wafer main body, a step of growing a non-doped silicon film on the back surface of the p-type silicon single crystal wafer main body, a step of ion-implanting oxygen into the silicon film, An n-type silicon film is formed by applying an n-type impurity on the surface, and heat-treating a p-type silicon single crystal wafer with a silicon film on which the silicon film is formed on the back surface, and the n-type silicon film and the p-type Forming an oxygen precipitate in the inside of the p-type silicon single crystal wafer main body; and, after gettering metal impurities in the n-type silicon film, the n-type formed on the back surface of the p-type silicon single crystal wafer main body. Removing the silicon film, and
The step of growing the non-doped silicon film on the back surface of the p-type silicon single crystal wafer body is a step of growing a silicon single crystal film by an epitaxial process.

  In the second and third aspects of the manufacturing method of the present invention, an epitaxial process or a CVD process can be applied as the process of growing the non-doped silicon film on the back surface of the p-type silicon single crystal wafer body.

Furthermore, in the first to third aspects of the manufacturing method of the present invention, the n-type silicon film formed on the back surface of the p-type silicon single crystal wafer after gettering metal impurities inside the n-type silicon film Since the step of removing is included, gettered metal impurities can be removed.

  With such a method of manufacturing a p-type silicon single crystal wafer, Cu that is most difficult to remove by the IG method can be easily gettered using oxygen precipitates inside the n-type silicon film, and the n-type silicon film By removing Cu, Cu can be completely removed.

  According to the present p-type silicon single crystal wafer, even the heavy metal impurities in the p-type silicon single crystal wafer, which are difficult to getter by the IG method, which has been increasingly important in recent years, are effectively gettered to activate the device. It can be removed from the area. In addition, the gettering in this p-type silicon single crystal wafer is not a segregation-type gettering such as a ring gettering but a relaxed precipitation type gettering, so that the p-type silicon single crystal wafer is heavily contaminated with heavy metal impurities. It can cope with heavy metal impurities. According to the manufacturing method of the present invention, the present p-type silicon single crystal wafer can be efficiently manufactured.

  Hereinafter, embodiments of the method for producing a p-type silicon single crystal wafer of the present invention will be described in more detail with reference to the accompanying drawings. However, various modifications other than the illustrated examples are possible without departing from the technical idea of the present invention. It goes without saying that it is possible. FIG. 1 is a cross-sectional explanatory view schematically showing an example of a manufacturing process of the p-type silicon single crystal wafer. FIG. 2 is a flowchart showing an example of the order of steps in the first aspect of the method of the present invention.

  In the present invention, first, a p-type silicon single crystal wafer body 10 is prepared [Step 100 in FIGS. 1A and 2]. The initial oxygen concentration, resistivity, crystal orientation and the like of the p-type silicon single crystal wafer main body 10 are not particularly specified, and the surface state of the p-type silicon single crystal wafer main body 10 is either the main surface polished or the front and back surfaces polished. However, the initial oxygen concentration needs to be higher than the concentration at which oxygen precipitates capable of gettering metal impurities can be formed.

  Then, an n-type silicon film 12 is formed on the back surface of the p-type silicon single crystal wafer body 10, that is, a p-type silicon single crystal wafer 10a with an n-type silicon film is formed [Step 102 in FIG. 1 (b) and FIG. ]. As a method for forming the n-type silicon film 12, an epitaxial growth method or a CVD method may be used. Further, the n-type dopant is introduced into the silicon film by flowing an n-type dopant gas together with the silicon growth gas during epitaxial growth or CVD growth. Alternatively, as will be described later, in epitaxial growth or CVD growth, a silicon film is grown undoped, then an n-type dopant is introduced into the silicon film by ion implantation, and heat treatment is performed to activate the n-type dopant in the silicon film. Alternatively, after applying an n-type dopant to the surface of the non-doped silicon film, the p-type silicon single crystal wafer with a silicon film may be heat treated to diffuse the n-type dopant into the non-doped silicon film.

  Next, an oxygen precipitate 14 is formed inside the n-type silicon film 12, and an oxygen precipitate 16 is formed inside the p-type silicon single crystal wafer body 10 [step 104 in FIG. 1 (c) and FIG. 2]. . In the epitaxial growth method and the CVD method, since hydrogen is used as a carrier gas for the silicon growth gas and the dopant gas, oxygen does not exist in the silicon film formed by these growth methods. Therefore, it is necessary to introduce oxygen into the n-type silicon film 12 after the growth. In order to introduce oxygen into the n-type silicon film 12, a method of ion-implanting oxygen into the n-type silicon film 12 is simple. In addition, even if the n-type silicon film 12 is thin, the ion implantation method is very advantageous because the range of ions to be implanted can be precisely controlled.

  Then, oxygen precipitation heat treatment is performed on the p-type silicon single crystal wafer 10a with the n-type silicon film having the n-type silicon film 12 into which oxygen is introduced on the back surface, whereby oxygen is precipitated inside the n-type silicon film 12. An object 14 can be formed. At this time, the atmosphere of the oxygen precipitate heat treatment is not particularly limited. Further, the heat treatment temperature and the heat treatment time are not particularly limited as long as oxygen precipitates that getter heavy metal impurities are sufficiently formed. Further, if this oxygen precipitate heat treatment is performed, oxygen precipitates 16 are also formed inside the p-type silicon single crystal wafer body 10.

  Note that the dopant and oxygen introduced into the silicon film by ion implantation must be activated by heat treatment, but this heat treatment may be combined with the oxygen precipitate heat treatment or may be performed separately. Also, the n-type dopant coating diffusion heat treatment is the same, and may be combined with the oxygen precipitate heat treatment or may be performed separately.

  Furthermore, when the silicon film is formed by the epitaxial growth method or the CVD method, either the dopant introduction step or the oxygen introduction step may be performed first, except when the dopant is introduced at the same time.

  As described above, the p-type silicon single crystal wafer 10b with the n-type silicon film having the n-type silicon film 12 manufactured by the oxygen precipitate treatment includes both the n-type silicon film 12 and the p-type silicon single crystal wafer body 10. Since the oxygen precipitates 14 and 16 are formed, heavy metal impurities can be effectively gettered. In particular, heavy metal impurities such as Cu that are difficult to getter with the oxygen precipitates 16 inside the p-type silicon single crystal wafer body 10 can be gettered into the oxygen precipitates 14 inside the n-type silicon film 12. .

  Further, the n-type silicon film 12 gettered with the heavy metal impurities is removed from the back surface of the p-type silicon single crystal wafer body 10 to produce the final p-type silicon single crystal wafer 10c. The gettered heavy metal impurities can be completely removed from the p-type silicon single crystal wafer 10c [FIG. 1 (d), step 106 in FIG. 2]. Note that there is no particular limitation on the method for removing the n-type silicon film 12, and it may be performed using a desired apparatus depending on the convenience of the apparatus and semiconductor device manufacturing process, such as polishing, grinding, wet etching, and dry etching. Good.

  As described above, in the first embodiment of the manufacturing method of the present invention shown in FIG. 2, oxygen precipitates are formed (step 104 in FIG. 2) by implanting oxygen ions into the n-type silicon film 12, FIG. 3 shows a flowchart showing step 104 of FIG. 2 as a more specific process, which can be realized by performing precipitation heat treatment. In FIG. 3, steps 100, 102, and 106 are the same as those in FIG. The oxygen precipitates in FIG. 3 are formed by injecting oxygen into the n-type silicon film (step 104a in FIG. 3) and forming oxygen precipitates by heat treatment of the p-type silicon single crystal wafer 10a with the n-type silicon film (FIG. 3). Step 104b).

  As described above, the n-type silicon film 12 may be formed by growing a non-doped silicon film, then introducing an n-type dopant into the silicon film by ion implantation, and performing a heat treatment for activating the dopant. After the n-type dopant is applied to the surface of the non-doped silicon film, the p-type silicon single crystal wafer with the silicon film may be heat-treated to diffuse the n-type dopant into the non-doped silicon film. Either the introduction step or the oxygen introduction step can be performed first. Other aspects of the method of the present invention will be described below with reference to the accompanying drawings.

  FIG. 4 is a flowchart showing an example of the process order of the second aspect of the manufacturing method of the present invention. Also in the second aspect of the manufacturing method of the present invention, first, a p-type silicon single crystal wafer body 10 is prepared (step 200 in FIG. 4). Next, a non-doped silicon film is formed on the back surface of the p-type silicon single crystal wafer body (step 202 in FIG. 4). Subsequently, n-type impurities are ion-implanted into the silicon film (step 204 in FIG. 4). Further, oxygen is ion-implanted into the silicon film (step 206 in FIG. 4). By heat-treating the p-type silicon single crystal wafer 10a with the silicon film, an n-type silicon film 12 is formed and oxygen precipitates 14 and 16 are formed inside the n-type silicon film 12 and the p-type silicon single crystal wafer body 10. Form (step 208 in FIG. 4). Further, as in the case described above, the n-type silicon film 12 gettered with heavy metal impurities is removed from the back surface of the p-type silicon single crystal wafer body 10 to produce the final p-type silicon single crystal wafer 10c (FIG. 4). Step 210).

  FIG. 5 is a flowchart showing an example of the process order of the third aspect of the manufacturing method of the present invention. In the third aspect of the manufacturing method of the present invention, the preparation of the p-type silicon single crystal wafer body 10 (step 300 in FIG. 5) and the formation of the non-doped silicon film (step 302 in FIG. 5) It is the same as that of the 2nd aspect. Next, oxygen is ion-implanted into the silicon film (step 304 in FIG. 5). Further, an n-type impurity is applied to the silicon film surface (step 306 in FIG. 5). The n-type silicon film 12 is formed by heat-treating the p-type silicon single crystal wafer 10a with the silicon film, and oxygen precipitates 14 and 16 are formed inside the n-type silicon film 12 and the p-type silicon single crystal wafer body 10. (Step 308 in FIG. 5). Further, the n-type silicon film 12 is removed from the back surface of the p-type silicon single crystal wafer body 10 to produce the final p-type silicon single crystal wafer 10c (step 310 in FIG. 5). In the flowcharts of FIGS. 4 and 5 described above, an epitaxial process or a CVD process is preferably used as the process of forming the non-doped silicon film on the back surface of the p-type silicon single crystal wafer body.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, it is needless to say that the following examples are illustrative and should not be construed as limiting.

Example 1
A crystal rod having a diameter of 6 inches, a p-type, an initial oxygen concentration of 14 ppma JEIDA, and an orientation <100> was pulled at a normal pulling rate (1.2 mm / min) by the CZ method. This crystal rod was processed into a wafer, and a phosphorus-added n-type silicon film having a thickness of 10 μm was formed on the back surface thereof by epitaxial growth.

Oxygen was ion-implanted into the back surface of the wafer, that is, the n-type silicon film, and oxygen was uniformly diffused by heat treatment at 1100 ° C. for 4 hours. Thereafter, heat treatment for oxygen precipitation at 700 ° C. for 8 hours and 1000 ° C. for 16 hours was performed to form oxygen precipitates in the back surface n-type silicon film. The oxygen precipitate density did not change between the surface layer of the front-side p-type silicon single crystal wafer main body and the n-type silicon film formed on the back surface of the wafer, and both were about 10 ⁹ cm ⁻³ .

Cu was applied to the surface layer side of the p-type silicon single crystal wafer thus produced at a concentration of 1 × 10 ¹³ cm ⁻² , and after a uniform diffusion heat treatment at 800 ° C. for 4 minutes, it was cooled to room temperature. Then, when the surface residual Cu density | concentration was measured with the total reflection X-ray fluorescence analysis method (TXRF method), Cu was below the detection minimum.

(Comparative Example 1)
A crystal rod having a diameter of 6 inches, a p-type, an initial oxygen concentration of 14 ppma JEIDA, and an orientation <100> was pulled at a normal pulling rate (1.2 mm / min) by the CZ method. This crystal rod was processed into a wafer, and a boron-added p-type silicon film having a thickness of 10 μm was formed on the back surface thereof by epitaxial growth.

Oxygen was ion-implanted into the back surface of the wafer, that is, the p-type silicon film, and oxygen was uniformly diffused by heat treatment at 1100 ° C. for 4 hours. Thereafter, heat treatment for oxygen precipitation at 700 ° C. for 8 hours and 1000 ° C. for 16 hours was performed to form oxygen precipitates in the p-type silicon film. The oxygen precipitate density was unchanged between the surface layer of the p-type silicon single crystal wafer and the p-type silicon film formed on the back surface of the wafer, and both were about 10 ⁹ cm ^-3 .

Cu was applied to the surface layer side of the p-type silicon single crystal wafer thus produced at a concentration of 1 × 10 ¹³ cm ⁻² , and after a uniform diffusion heat treatment at 800 ° C. for 4 minutes, it was cooled to room temperature. Then, when the surface residual Cu density | concentration was measured with the total reflection X-ray fluorescence analysis method (TXRF method), it was detected with the density | concentration of 10 ^{< 12} > cm ^<-2 >.

(Comparative Example 2)
A crystal rod having a diameter of 6 inches, a p-type, an initial oxygen concentration of 14 ppma JEIDA, and an orientation <100> was pulled at a normal pulling rate (1.2 mm / min) by the CZ method. The crystal rod was processed into a wafer and subjected to the same heat treatment as in Example 1. Specifically, three heat treatments of 1100 ° C., 4 hours, 700 ° C., 8 hours and 1000 ° C., 16 hours were performed. The density of oxygen precipitates was almost the same as that of the example, and was about 10 ⁹ cm ⁻³ .

Cu was applied to the surface side of the wafer thus produced at a concentration of 1 × 10 ¹³ cm ⁻² , and after 800 ° C. for 4 minutes of uniform diffusion heat treatment, it was cooled to room temperature. Then, when the surface residual Cu density | concentration was measured with the total reflection X-ray fluorescence analysis method (TXRF method), Cu was detected by the density | concentration of 10 ^{< 12} > cm ^<-2 >.

(Comparative Example 3)
A crystal rod having a diameter of 6 inches, a p-type, an initial oxygen concentration of 14 ppma JEIDA, and an orientation <100> was pulled at a normal pulling rate (1.2 mm / min) by the CZ method. This crystal rod is processed into a substrate wafer, but heat treatment as in Example 1 is not performed, and Cu is applied to the surface side of the wafer as it is at a concentration of 1 × 10 ¹³ cm ⁻² at 800 ° C. for 4 minutes. After the uniform diffusion heat treatment, it was cooled to room temperature. Thereafter, when the surface residual Cu concentration was measured by a total reflection fluorescent X-ray analysis method (TXRF method), Cu was detected at a concentration of about 10 ¹³ cm ⁻² , which was almost the same as the initial contamination amount.

  Thus, according to Example 1 and Comparative Examples 1 to 3, the n-type silicon film formed on the back surface of the p-type silicon single crystal wafer and the oxygen precipitate formed therein have a high IG capability for Cu. I understand that.

  The present invention is not limited to the above embodiment. The above embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope. For example, in the present invention, the epitaxial growth method and the CVD method are exemplified as the method for forming the n-type silicon film on the back surface of the p-type silicon single crystal wafer, but the present invention is not limited to this. For example, a method of bonding a p-type silicon single crystal wafer and an n-type silicon single crystal wafer and then polishing the n-type silicon single crystal wafer to form an n-type silicon film on the back surface of the wafer, so-called smart cut method A method of forming an n-type silicon film on the back surface of a p-type silicon single crystal wafer by performing the above is also included in the scope of the present invention. Further, after the p-type silicon single crystal wafer having the n-type silicon film on the back surface as in the present invention is manufactured, the removal of the n-type silicon film on the back surface is performed on the main surface of the p-type silicon single crystal wafer. May be performed before or after the formation.

It is sectional explanatory drawing which shows an example of the manufacturing process of this p-type silicon single crystal wafer typically, (a) is a p-type silicon single crystal wafer main body, (b) is a p-type silicon single crystal wafer with an n-type silicon film, (C) shows a p-type silicon single crystal wafer with an n-type silicon film on which oxygen precipitates are formed, and (d) shows a final p-type silicon single crystal wafer from which the n-type silicon film has been removed. It is a flowchart which shows an example of the process order of the 1st aspect of the manufacturing method of this invention. It is a flowchart which shows the other example of the process order of the 1st aspect of the manufacturing method of this invention. It is a flowchart which shows an example of the process order of the 2nd aspect of the manufacturing method of this invention. It is a flowchart which shows an example of the process order of the 3rd aspect of the manufacturing method of this invention.

Explanation of symbols

10: p-type silicon single crystal wafer body, 10a: p-type silicon single crystal wafer with n-type silicon film, 10b: p-type silicon single crystal wafer with n-type silicon film on which oxygen precipitates are formed, 10c: final p-type Silicon single crystal wafer, 12: n-type silicon film, 14, 16: oxygen precipitate.

Claims (3)

a step of preparing a p-type silicon single crystal wafer main body, a step of forming an n-type silicon film on the back surface of the p-type silicon single crystal wafer main body to form a p-type silicon single crystal wafer with an n-type silicon film, and the n-type Forming an oxygen precipitate inside the silicon film and the p-type silicon single crystal wafer main body, and forming a metal impurity inside the n-type silicon film and then forming the back surface of the p-type silicon single crystal wafer main body; Removing the n-type silicon film formed,
The step of growing the n-type silicon film on the back surface of the p-type silicon single crystal wafer body is a step of growing the n-type silicon single crystal film by an epitaxial process.
The step of forming the oxygen precipitate includes a step of ion-implanting oxygen into the n-type silicon film, and a heat treatment of the p-type silicon single crystal wafer with the n-type silicon film having the n-type silicon film formed on the back surface. And a process for producing a p-type silicon single crystal wafer. a step of preparing a p-type silicon single crystal wafer main body, a step of growing a non-doped silicon film on the back surface of the p-type silicon single crystal wafer main body, a step of ion-implanting n-type impurities into the silicon film, and the silicon A step of ion-implanting oxygen into the film; and heat-treating a p-type silicon single crystal wafer with a silicon film on which the silicon film is formed on the back surface to form an n-type silicon film and the n-type silicon film and the p-type A step of forming oxygen precipitates inside the silicon single crystal wafer body; and the n-type silicon formed on the back surface of the p-type silicon single crystal wafer body after gettering metal impurities inside the n-type silicon film. Removing the film, and
The method for producing a p-type silicon single crystal wafer, wherein the step of growing the non-doped silicon film on the back surface of the main body of the p-type silicon single crystal wafer is a step of growing a silicon single crystal film by an epitaxial process. a step of preparing a p-type silicon single crystal wafer main body, a step of growing a non-doped silicon film on the back surface of the p-type silicon single crystal wafer main body, a step of ion-implanting oxygen into the silicon film, An n-type silicon film is formed by applying an n-type impurity on the surface, and heat-treating a p-type silicon single crystal wafer with a silicon film on which the silicon film is formed on the back surface, and the n-type silicon film and the p-type Forming an oxygen precipitate in the inside of the p-type silicon single crystal wafer main body; and, after gettering metal impurities in the n-type silicon film, the n-type formed on the back surface of the p-type silicon single crystal wafer main body. Removing the silicon film, and
The method for producing a p-type silicon single crystal wafer, wherein the step of growing the non-doped silicon film on the back surface of the main body of the p-type silicon single crystal wafer is a step of growing a silicon single crystal film by an epitaxial process.

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