JP2018041755A - Deterioration evaluation method and method of manufacturing silicon material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new method for evaluating deterioration of a member having the carbon-containing surface used in a manufacturing process of a silicon material.SOLUTION: Disclosed is a deterioration evaluation method for a member used in a manufacturing process of a silicon material. The member has the carbon containing surface. The deterioration evaluation method includes the steps of: performing DLTS measurement for a silicon material manufactured using an evaluation target member; and evaluating the degree of the deterioration of the member on the basis of the peak intensity of a carbon-related level in the DLTS spectrum obtained by measurement.SELECTED DRAWING: None

Description

  The present invention relates to a member deterioration evaluation method used in a silicon material manufacturing process and a silicon material manufacturing method.

  In the manufacturing process of a silicon material such as a silicon wafer and a silicon single crystal ingot, a member having a carbon-containing surface is used in various processes. For example, a member in which a base material is coated with silicon carbide is used as a susceptor on which a silicon wafer is placed in a heat treatment furnace, a member for a pulling device used for growing a silicon single crystal ingot, etc. 1 and 2).

JP 2000-327461 A Japanese Patent Laid-Open No. 11-240780

  A silicon wafer used as a semiconductor substrate is always required to reduce impurity contamination that causes deterioration in device characteristics. In recent years, attention has been paid to carbon as an impurity contained in a silicon wafer, and it has been studied to reduce carbon contamination of the silicon wafer. In this regard, when a member having a carbon-containing surface as described above deteriorates, carbon released from the member adheres to or mixes into the silicon material, thereby causing contamination of the silicon wafer. For example, deterioration of the susceptor may cause carbon to adhere to the silicon wafer. In addition, mixing of carbon into the silicon single crystal ingot due to deterioration of the constituent members of the pulling apparatus may cause contamination of the silicon wafer cut out from the silicon single crystal ingot. Further, for example, in the case of a member having a carbon-containing film on a base material, when the deterioration becomes severe, the base material is exposed due to partial omission of the film (referred to as pinholes) or cracks (referred to as cracks). Not only the base material components may also cause contamination of the silicon material. Therefore, it is possible to evaluate the deterioration of a member having a carbon-containing surface used in the manufacturing process of silicon material, and to replace or repair the member before severe deterioration occurs, so that high-quality silicon with less impurity contamination from the manufacturing process. Desirable for stable supply of wafers.

  Therefore, an object of the present invention is to provide a new method for evaluating the deterioration of a member having a carbon-containing surface used in the production process of a silicon material.

  In the course of studying to achieve the above object, the present inventors have found that the progress of deterioration of a member having a carbon-containing surface and the amount of carbon contamination of the silicon material produced using this member I guessed there was a correlation. Under such inference, the present inventors have a member having a carbon-containing surface based on a measurement result obtained by a measurement method capable of quantitatively evaluating carbon contamination of a silicon material manufactured using a member subjected to degradation evaluation. In order to evaluate the deterioration of the material, intensive study was repeated. As a result, it came to pay attention to DLTS method (Deep-Level Transient Spectroscopy). The DLTS method is known as a method for evaluating metal contamination of a silicon material in the field of manufacturing a silicon material such as a silicon wafer, but the possibility of qualitative analysis is mainly studied for carbon. On the other hand, the present inventors obtained a new finding that has not been known so far that a correlation is seen between the measurement result obtained by the DLTS method and the deterioration of the member having a carbon-containing surface, Based on this finding, the present invention has been completed.

That is, one embodiment of the present invention is
A member deterioration evaluation method (hereinafter, also simply referred to as “degradation evaluation method”) used in a manufacturing process of a silicon material,
The member has a carbon-containing surface;
Performing a DLTS measurement on a silicon material manufactured using the evaluation target member; and
Evaluating the degree of deterioration of the member based on the peak intensity of carbon-related levels in the DLTS spectrum obtained by the measurement,
Deterioration evaluation method including
About.

  In one aspect, the deterioration evaluation method sets the threshold value of the peak intensity in advance, and if the peak intensity obtained by the measurement exceeds the threshold value, the evaluation target member needs to be replaced or repaired. Determining.

  In one aspect, the member is a member having a carbon-containing coating, and the surface of the coating is the carbon-containing surface.

  In one embodiment, the member has a carbon-containing coating on the base material, and the base material is a sintered body.

  In one aspect, the sintered body is graphite.

  In one aspect | mode, the said carbon containing film is a carbon containing vapor deposition film.

  In one aspect | mode, the said carbon containing vapor deposition film is a silicon carbide vapor deposition film.

  In one aspect, the deterioration evaluation method includes introducing a hydrogen atom into a measurement sample cut out from a silicon material manufactured using a member to be evaluated, and irradiating the measurement sample into which the hydrogen atom has been introduced with an electron beam. Subjecting to the DLTS measurement without processing.

  In one embodiment, introduction of hydrogen atoms into the measurement sample is performed by immersing the measurement sample in hydrofluoric acid.

  In one aspect, the silicon material is a silicon wafer.

  In one aspect, the member is a susceptor disposed in a heat treatment furnace.

A further aspect of the invention provides:
A silicon material manufacturing method for manufacturing a plurality of silicon materials in a silicon material manufacturing process,
The manufacturing process of the silicon material includes a process using a member having a carbon-containing surface,
Evaluating deterioration of the member by the deterioration evaluation method using at least one silicon material manufactured in the manufacturing process of the silicon material; and
As a result of the evaluation, when it is determined that the deterioration of the member exceeds an allowable level, the silicon material is manufactured in the manufacturing process of the silicon material after replacing or repairing the member,
A method for producing a silicon material,
About.

  According to one embodiment of the present invention, it is possible to evaluate deterioration of a member having a carbon-containing surface used in a manufacturing process of a silicon material. Based on the result of such evaluation, by replacing or repairing a member having a carbon-containing surface in the manufacturing process of the silicon material, it is possible to stably supply a silicon material in which contamination caused by the member having a carbon-containing surface is reduced. It becomes possible.

The evaluation result obtained in Example 1 is shown. 3 is a DLTS spectrum obtained for a silicon epitaxial wafer in Example 2. 3 is a DLTS spectrum obtained for a silicon epitaxial wafer in Example 2.

[Degradation evaluation method]
The deterioration evaluation method of the present invention is a member deterioration evaluation method used in a silicon material manufacturing process, wherein the member has a carbon-containing surface, and DLTS measurement is performed on a silicon material manufactured using the evaluation target member. And evaluating the degree of deterioration of the member based on the peak intensity of the carbon-related level in the DLTS spectrum obtained by the measurement.
Hereinafter, the deterioration evaluation method will be described in more detail.

<Member to be evaluated>
The member to be evaluated by the deterioration evaluation method is a member having a carbon-containing surface used in the manufacturing process of the silicon material. Examples of the member include a wafer placing member such as a susceptor on which a silicon wafer is placed in a heat treatment furnace and a heat treatment boat. Examples of the heat treatment furnace in which such a member is disposed include an epitaxial growth furnace for performing epitaxial growth (vapor phase growth) for forming an epitaxial layer of a silicon epitaxial wafer, and an annealing furnace for performing annealing for manufacturing an annealed wafer. it can. Moreover, as said member, the structural members of heat processing furnaces, such as a core tube in a heat processing furnace, and a soaking | uniform-heating tube, can also be mentioned. The member may be a holding member for holding the silicon wafer in the manufacturing process of the silicon wafer, a transfer member for transferring, or a polishing member such as a lap plate used in the polishing process of the silicon wafer. Furthermore, the structural member of the ion implantation apparatus which ion-implants to a silicon wafer can also be mentioned. Moreover, the said member can also be a member (for example, member for pulling apparatuses) used for manufacture of the silicon single crystal ingot which cuts out a wafer-shaped silicon wafer.

  The member has a carbon-containing surface. As one aspect of the member, a member having a carbon-containing film on a base material and the surface of the carbon-containing film being the carbon-containing surface can be exemplified. In addition, as one aspect of the above member, a member in which the entire member is made of a carbon-containing material can be exemplified. When a member having such a carbon-containing surface is deteriorated due to repeated use or the like, carbon released from the member due to deterioration adheres to or mixes into the silicon material, thereby causing carbon contamination of the silicon material. In addition, when a member having a carbon-containing film is severely deteriorated, a partial loss (pinhole) or crack (crack) of the film occurs and the base material is exposed. It may cause contamination of the silicon material. According to the deterioration evaluation method of the present invention, the degree of deterioration due to such contamination can be evaluated based on the measurement result of DLTS measurement. Details of the evaluation will be described later.

  In any of the above-described members, the state of carbon contained in the carbon-containing surface is not limited. The carbon contained in the carbon-containing surface may be crystalline carbon or amorphous carbon (that is, glassy carbon). The carbon-containing surface may contain crystalline carbon and glassy carbon. Moreover, the carbon content of the carbon-containing surface is not particularly limited. In the member having a carbon-containing film on the base material, which is one embodiment of the above member, the carbon-containing film is a variety of carbon-containing films formed on the base material by a known film forming method such as vapor deposition or thermal decomposition. be able to. For example, a silicon carbide (SiC) vapor deposition film is mentioned as a carbon containing vapor deposition film. The silicon carbide vapor deposition film can be formed on the base material by vapor deposition using silicon carbide as a vapor deposition source. Since the silicon carbide vapor deposition film is excellent in heat resistance, durability and the like, it is preferable as a film that plays a role of effectively reducing contamination of the silicon material from the base material. Examples of the vapor deposition method include known methods such as a CVD (chemical vapor deposition) method and a vacuum vapor deposition method. For example, as a method of forming a carbon-containing film (glass-like carbon film) by coating a base material with glassy carbon, the resin is heated to high temperature after impregnating the base material with resin or coating the base material with resin. And carbonizing the carbon-containing film formed on the base material by vapor deposition or the like. The thickness of the carbon-containing coating is, for example, about 1 μm to 200 μm, but is not limited to the above range.

  The base material having the carbon-containing film may be made of a carbon-containing material or a material not containing carbon. The member made of a carbon-containing material is preferably a sintered body from the viewpoint of heat resistance, durability, and the like. The sintered body is a solid material obtained by heating and solidifying powder at a temperature lower than the melting point. Examples of the sintered body include graphite (carbon sintered body), silicon carbide (SiC) sintered body, and the like. In general, the sintered body often contains impurities such as metals and impurities derived from the sintering aid, which are inevitably mixed from the raw material or the manufacturing process. Graphite and silicon carbide sintered bodies are carbon-containing materials, but the above impurities other than carbon can also cause contamination of silicon materials. According to the deterioration evaluation method of the present invention, it is possible to replace or repair the member before contamination due to such impurities occurs. Details will be described later.

  The description regarding said base material can be referred to about the member which the whole member which is one aspect | mode of the said member consists of a carbon containing material.

<DLTS measurement>
(Silicon material to be measured)
In order to evaluate the degree of deterioration of the member having the carbon-containing surface described above, in the deterioration evaluation method of the present invention, DLTS measurement is performed on the silicon material manufactured using the member. The silicon material for performing the DLTS measurement may be n-type or p-type. Further, the dopant concentration (that is, resistivity), oxygen concentration, etc. are not limited. One embodiment of the silicon material is a wafer-shaped silicon material, that is, a silicon wafer. The silicon wafer may be a silicon single crystal wafer (so-called bare wafer) or a wafer having one or more layers on the bare wafer. Specific examples of the one or more layers include an epitaxial layer. However, the silicon material to be measured is not limited to a silicon wafer. For example, the silicon material to be measured may include a silicon single crystal ingot or a part of the ingot.

(Preprocessing)
DLTS measurement can usually be performed on a sample element produced by forming a semiconductor junction (Schottky junction or pn junction) on a silicon sample obtained by cutting out a part of the silicon material. In general, it is preferable that the surface of a sample subjected to DLTS measurement has high smoothness. Accordingly, the silicon material before cutting out the silicon sample or the silicon sample obtained by cutting out the silicon material can be optionally subjected to polishing for improving surface smoothness. The polishing process preferably includes a mirror polishing process. For example, when the silicon material to be measured is a silicon single crystal ingot or a part of an ingot, it is preferable to prepare a sample element after polishing a silicon sample cut out from the silicon material. It is more preferable to produce it. As the polishing process, a known polishing process applied to a silicon wafer such as a mirror polishing process can be performed. When the silicon material to be measured is a silicon wafer, the silicon wafer is usually obtained through a polishing process such as a mirror polishing process. Therefore, the surface of a silicon sample cut out from a silicon wafer usually has high smoothness even without polishing.

  It is preferable to perform a pretreatment for activating the carbon-related levels in the silicon band gap on the silicon sample before the preparation of the sample element. As one aspect of such pretreatment, electron beam irradiation treatment can be given. The present inventors have newly found that the density of carbon-related levels in the band gap of silicon activated by irradiating a silicon sample with an electron beam has a correlation with the carbon concentration in the silicon sample. . This point was newly found by the present inventors. By utilizing this correlation, the carbon concentration in the silicon wafer can be quantitatively evaluated. For the electron beam irradiation treatment, a known technique relating to DLTS measurement can be applied.

  One embodiment of the pretreatment includes introduction of hydrogen atoms. Regarding the introduction of hydrogen atoms, the present inventors have found that the density of carbon-related levels in the band gap of silicon activated by introducing hydrogen atoms into a silicon sample has a correlation with the carbon concentration in the silicon sample. I found a new thing. This point was also newly found by the present inventors. By utilizing this correlation, the carbon concentration in the silicon sample can be quantitatively evaluated. The silicon sample after introduction of hydrogen atoms is preferably subjected to DLTS measurement without performing electron beam irradiation treatment. Electron beam irradiation processing has a long lead time, requires large-scale equipment, increases costs, requires heat treatment for protective oxide film preparation and recovery processing in addition to the electron beam irradiation process, and increases the number of processes. Since there is a problem in terms, it is preferable to perform DLTS measurement without electron beam irradiation treatment. The term “without performing electron beam irradiation treatment” in the present invention and the present specification means that the silicon sample is not actively irradiated with an electron beam under sunlight, illumination, or the like. Inevitable electron beam irradiation is allowed.

  The introduction of hydrogen atoms may be performed by a dry process (dry process) or by a wet process (wet process, that is, use of a solution). For example, introduction of hydrogen atoms by dry treatment can be performed by an ion implantation method, hydrogen plasma, or the like. Note that the introduction of hydrogen atoms in the present invention and the present specification includes an embodiment in which hydrogen atoms are introduced in an ion or plasma state.

  Hydrogen atoms can be introduced by wet treatment by bringing a silicon sample into contact with the solution (for example, by immersion). The solution used here may be an acid solution or a base solution as long as it is a solution containing hydrogen atoms in either an ionized state (ion) or a salt state. Examples of the acid solution include hydrofluoric acid, a mixed solution of hydrofluoric acid and nitric acid (hydrofluoric nitric acid), a mixed solution of sulfuric acid and hydrogen peroxide, a mixed solution of hydrochloric acid and hydrogen peroxide, and the like. Examples of the base solution include a sodium hydroxide solution, a potassium hydroxide solution, a mixed solution of ammonia water and hydrogen peroxide, and the like. The various solutions are preferably aqueous solutions (solutions containing water), and more preferably aqueous solutions. The acid concentration of the acid solution and the base concentration of the base solution are not particularly limited. As an example, introduction of hydrogen atoms by hydrofluoric acid can be performed by immersing a silicon sample or a silicon material to be measured for cutting out the silicon sample in 1 to 25 mass% hydrofluoric acid for 1 to 10 minutes. After immersion, the sample to be measured may be subjected to post-treatment such as washing and drying as necessary.

(Specific aspects of DLTS measurement)
After the pretreatment described above, DLTS measurement of the silicon sample can be performed. DLTS measurement can be performed by a known method. Usually, the measurement is performed by the following method. A semiconductor junction (Schottky junction or pn junction) is formed on one surface of a silicon sample, and an ohmic layer is formed on the other surface to produce a sample element (diode). The transient response of the capacitance (capacitance) of the sample element is measured by periodically applying a voltage while performing a temperature sweep. The voltage is normally applied by alternately and periodically applying a reverse voltage for forming a depletion layer and a weak voltage in the vicinity of 0 V for capturing carriers in the depletion layer. By plotting the DLTS signal against temperature, a DLTS spectrum can be obtained. By fitting the DLTS spectrum obtained as the sum of the peaks detected by the DLTS measurement by a known method, the DLTS spectrum of the carbon-related level (trap level) used for evaluation can be separated.

  As a carbon-related level. One or more of the trap levels generally known as carbon related levels can be employed. Further, as the carbon-related levels, one or more trap levels selected from the group consisting of Ec (the energy at the bottom of the conduction band) -0.10 eV, Ec-0.13 eV, and Ec-0.15 eV may be used. it can. In particular, when the pretreatment is performed by introducing hydrogen atoms, it is preferable to use one or more trap levels selected from the group consisting of these three trap levels as the carbon-related levels. These trap levels can be activated without introducing an electron beam by introducing hydrogen atoms, and the density (that is, the peak intensity of the DLTS spectrum) has a correlation with the carbon concentration in the silicon sample. This is because it became clear as a result of their earnest examination. For example, in a DLTS measurement at a frequency of 250 Hz, the trap level density of Ec-0.10 eV is a peak near 76K, the trap level density of Ec-0.13 eV is a peak near 87K, and the trap level of Ec-0.15 eV. The unit density can be measured based on the peak intensity (DLTS signal intensity) of the peak near 101K. The peak used for evaluation of the degree of deterioration is, for example, at least one of the above three peaks, and two or three peaks may be used. Usually, it can be determined that the carbon concentration in the silicon sample is higher as the peak intensity (DLTS signal intensity) is higher when compared at the same trap level density. Therefore, it can be determined that the carbon concentration in the silicon sample is higher as the peak intensity of the DLTS spectrum at the trap level separated by the fitting process is larger. From the viewpoint of measuring the carbon concentration with higher accuracy, it is preferable to evaluate the degree of deterioration based on the evaluation result at Ec-0.13 eV and / or Ec-0.15 eV.

  As one aspect of the evaluation of the degree of deterioration, it can be determined that the degree of deterioration of the member to be evaluated is more severe as the peak intensity of the DLTS spectrum of the carbon-related level used for evaluation is larger. In one aspect, the amount of carbon liberated from the member increases as the deterioration of the member progresses, and it is considered that the carbon contamination concentration of the silicon material manufactured using the member increases. In this case, when the peak intensity exceeds a preset threshold, it can be determined that the member to be evaluated is replaced or repaired. Thus, it is possible to prevent the silicon material from being seriously contaminated by the member having the carbon-containing surface.

  In another aspect, the DLTS measurement is performed on a plurality of silicon materials manufactured by repeatedly using the member to be evaluated, and the peak intensity of the carbon-related level increases from the increase in the number of use times and the cumulative use time. It can also be determined that the deterioration of the member to be evaluated is severe when it starts to decrease. For example, in a member having a carbon-containing film on a base material, the reason is not clear, but at the initial stage of deterioration of the member, the deterioration of the carbon-containing film proceeds to increase the amount of liberated carbon, and the deterioration of the carbon-containing film proceeds This is because the amount of liberated carbon may turn to decrease as the process proceeds further. Before and after such a decrease, it is considered that pinholes and / or cracks are generated in the carbon-containing coating, and contamination derived from the base material may occur in the silicon material. Considering the above points, DLTS measurement is performed on multiple silicon wafers manufactured by repeatedly using the evaluation target member. If the peak intensity exceeds a preset threshold value, the evaluation target member is replaced or repaired. By determining, the member to be evaluated can be replaced or repaired before the amount of liberated carbon changes from increasing to decreasing, that is, before contamination derived from the base material occurs. Thus, it is possible to prevent the contamination derived from the base material. In another aspect, the peak of a contaminant element other than the carbon-related level appears in the DLTS spectrum, or the peak intensity derived from a contaminant element other than the carbon-related level exceeds a preset threshold value. It can also be determined that the member to be evaluated requires replacement or repair.

  In each of the above aspects, the threshold value for determining that the member to be evaluated needs to be replaced or repaired is not particularly limited, and should be set according to the use of the product wafer, the quality required for the product wafer, etc. Can do. Further, the member to be evaluated can be repaired by re-deposition of a carbon-containing film.

[Manufacturing method of silicon material]
According to still another aspect of the present invention, there is provided a silicon material manufacturing method (hereinafter, also simply referred to as “manufacturing method”) for manufacturing a plurality of silicon materials in the silicon material manufacturing process. Evaluation of deterioration of the member by the deterioration evaluation method using at least one silicon material produced in the production process of the silicon material, including treatment using a member having a carbon-containing surface; and As a result, when it is determined that the deterioration of the member exceeds an allowable level, the present invention relates to a method for manufacturing a silicon material, which includes manufacturing the silicon material in the manufacturing process of the silicon material after replacing or repairing the member.

  As a manufacturing process of the silicon material in the manufacturing method, a known process can be adopted without any limitation as a manufacturing process of the silicon material used for various applications. As an example, a step of growing a silicon single crystal ingot by the Czochralski method (CZ method) can be mentioned, and a silicon wafer is cut out from the grown ingot, and the cut silicon wafer is subjected to various processing (heat treatment, polishing, A silicon wafer can be manufactured by subjecting it to mechanical processing such as grinding, ion implantation processing, and cleaning processing. These manufacturing processes include processing using a member having a carbon-containing surface. A specific example of such processing is as described above. In the manufacturing method, the degree of deterioration of the member having the carbon-containing surface is determined by the deterioration evaluation method described in detail above using at least one of the silicon materials manufactured through the treatment using the member having the carbon-containing surface. To evaluate. As a result of the evaluation, when it is determined that the deterioration of the member exceeds the allowable level, the production of the silicon material is resumed after replacing or repairing the member. In this way, it is possible to stably supply a high-quality silicon material in which contamination due to a member having a carbon-containing surface is reduced. The allowable level is not particularly limited as in the case of the threshold value, and can be set according to the use of the product wafer, the quality required for the product wafer, and the like.

  Below, the present invention will be further explained based on examples. However, the present invention is not limited to the embodiment shown in the examples.

[Example 1]
A plurality of silicon wafers (diameter 200 mm, n-type, resistivity 0.01 Ω · cm) were cut out from a silicon single crystal ingot grown by the CZ method. A plurality of silicon epitaxial wafers were prepared by placing a plurality of cut silicon wafers on a susceptor in an epitaxial growth furnace and performing epitaxial growth to form an epitaxial layer (resistivity: 25 Ω · cm). Each silicon epitaxial wafer is manufactured using the same susceptor in the same epitaxial growth furnace, but the accumulated use time of the susceptor is different. The susceptor has a silicon carbide vapor deposition film (CVD-SiC film) having a thickness of about 120 μm on a graphite base material.

A silicon sample for DLTS measurement was cut out from each silicon epitaxial wafer. By sequentially performing the following (A), (B) and (C) on the cut silicon sample, a Schottky junction is formed on one surface of each silicon sample, and an ohmic layer (Ga layer) is formed on the other surface. The sample element was fabricated by forming. Hydrogen atoms are introduced into the silicon sample by the following process (A) (wet process).
(A) Soaked in 5% by mass hydrofluoric acid for 5 minutes, then washed with water for 10 minutes. (B) Formation of Schottky electrode (Au electrode) by vacuum deposition on the epitaxial layer.

A reverse voltage for forming a depletion layer and a pulse voltage for trapping carriers in the depletion layer alternately and periodically at the Schottky junction of the sample element (diode) manufactured by performing the above processes (A) to (C) Applied. The transient response of the capacitance (capacitance) generated in response to the voltage was measured.
The above voltage application and capacity measurement were performed while sweeping the sample temperature in a predetermined temperature range. DLTS signal intensity ΔC was plotted against temperature to obtain a DLTS spectrum. The measurement frequency was 250 Hz. In the measurement, the silicon sample and the sample element were not irradiated with an electron beam.
The DLTS spectrum obtained for each silicon epitaxial wafer was subjected to a fitting process (Ture shape fitting process) using a program manufactured by SEMILAB,
Ec-0.10 eV trap level (peak position: temperature 76K),
Ec-0.13 eV trap level (peak position: temperature 87K), and Ec-0.15 eV trap level (peak position: temperature 101K),
Separated into DLTS spectra. In the following, the DLTS spectrum of the trap level of Ec-0.10 eV is represented by E1 Fit. , Ec-0.13 eV trap level DLTS spectrum of E2 Fit. , Ec-0.15 eV trap level DLTS spectrum of E3 Fit. Call it.
As an example, the E3 Fit. FIG. 1 shows a graph in which the peak intensity of the DLTS spectrum is plotted against the cumulative usage time of the susceptor used. In FIG. 1 and the drawings to be described later, the units a. u. Means an arbitrary unit.
As shown in FIG. 1, the peak intensity value tended to increase as the cumulative usage time of the susceptor increased. From this result, it can be determined that the carbon concentration of the silicon epitaxial wafer tends to increase as the cumulative use time of the susceptor increases. It is considered that the carbon carbide vapor deposition film deteriorates due to the repeated deterioration of the susceptor and carbon is liberated, and the carbon liberation amount increases as the deterioration progresses, and the carbon contamination concentration of the silicon epitaxial wafer increases. Therefore, by setting a threshold value for the peak intensity required as described above, when the peak intensity exceeds the threshold value, the susceptor of the epitaxial growth furnace is replaced or the silicon carbide vapor deposition film of the susceptor is re-deposited. Etc. can be repaired. By determining the replacement or repair time of the susceptor in this way, it becomes possible to reduce carbon contamination of the silicon epitaxial wafer due to deterioration of the susceptor.

  The above includes E3 Fit. In this example, the degree of deterioration of the susceptor was evaluated using E1 Fit. And / or E2 Fit. Can also be used to evaluate the degree of deterioration of the susceptor. According to the study by the present inventors, among the above three carbon-related levels, the Ec-0.13 eV DLTS spectrum has a sharper peak shape and tends to be suitable for quantification of a smaller amount of carbon. The DLTS spectrum of Ec-0.15 eV tended to be more highly correlated with the carbon concentration.

[Example 2]
A plurality of silicon epitaxial wafers were produced by repeatedly using the susceptor used in Example 1.
A silicon sample for DLTS measurement was cut out from each produced silicon epitaxial wafer. By sequentially performing (A), (B) and (C) on the cut silicon sample, a Schottky junction is formed on one surface of each silicon sample, and an ohmic layer (Ga layer) is formed on the other surface. The sample element was fabricated by forming.
DLTS measurement was performed on the sample element (diode) manufactured by performing the processes (A) to (C) by the same method as in Example 1.
DLTS spectrum obtained for each silicon epitaxial wafer, using a program manufactured by SEMILAB,
Ec-0.08 eV trap level a (Ti related level),
Trap level b (carbon-related level) of Ec-0.15 eV,
Trap level c (Ti related level) of Ec−0.27 eV,
Fitting treatment (Ture shape fitting treatment) was performed. It is known in the literature that the trap levels a and c are Ti related levels.

Table 1 shows the peak intensities of the three trap levels obtained for two silicon epitaxial wafers (hereinafter referred to as wafers A and B) having different accumulated usage times of the used susceptors. The peak intensity is represented by a relative value where the peak intensity of the trap level b (carbon-related level) of the silicon epitaxial wafer A is 1.0.
FIG. 2 is a DLTS spectrum obtained by fitting the trap level b (carbon-related level) of the wafer A. FIG. 3 is a DLTS spectrum obtained by fitting the three trap levels of the wafer B.

In Example 1 above, the peak intensity of the trap level b (E3 Fit.) Tended to increase as the cumulative use time of the susceptor increased.
On the other hand, in Example 2 in which the cumulative use time of the susceptor is longer than that in Example 1, the peak intensity of trap level 2 (E3 Fit.) Changed from increasing to decreasing as shown in Table 1, and Ti related Levels were also detected. Ti is considered to be an impurity contained in the graphite of the base material of the susceptor. In such a case, for example, when the peak intensity of the carbon-related level has changed from an increase to a decrease, the silicon epitaxial wafer to be manufactured is prevented from being severely contaminated by replacing or repairing the susceptor. be able to. Alternatively, by setting a threshold in advance such as performing a preliminary experiment so that replacement or repair is performed before the peak intensity of the carbon-related level changes from increasing to decreasing, there is no Ti contamination or Ti contamination is extremely low. A small number of silicon epitaxial wafers can be stably supplied.

  The present invention is useful in the field of manufacturing various silicon materials such as silicon wafers.

Claims (13)

A method for evaluating deterioration of a member used in a manufacturing process of a silicon material,
The member has a carbon-containing surface;
Performing a DLTS measurement on a silicon material manufactured using the evaluation target member; and
Evaluating the degree of deterioration of the member based on the peak intensity of the carbon-related levels in the DLTS spectrum obtained by the measurement,
The deterioration evaluation method comprising: The deterioration evaluation method according to claim 1, wherein the evaluation is performed by determining that the degree of deterioration of the member is more severe as the peak intensity is higher. Presetting a peak intensity threshold; and
When the peak intensity obtained by the measurement exceeds the threshold value, the evaluation target member is determined to require replacement or repair;
The deterioration evaluation method according to claim 2, comprising: The deterioration evaluation method according to claim 1, wherein the member is a member having a carbon-containing coating, and the surface of the coating is the carbon-containing surface. The deterioration evaluation method according to claim 4, wherein the member has the carbon-containing film on a base material, and the base material is a sintered body. The deterioration evaluation method according to claim 5, wherein the sintered body is graphite. The deterioration evaluation method according to claim 4, wherein the carbon-containing film is a carbon-containing vapor-deposited film. The deterioration evaluation method according to claim 7, wherein the carbon-containing vapor deposition film is a silicon carbide vapor deposition film. Introducing hydrogen atoms into a measurement sample cut out from a silicon wafer manufactured using a member to be evaluated, and subjecting the measurement sample into which the hydrogen atoms have been introduced to the DLTS measurement without performing electron beam irradiation treatment about,
The deterioration evaluation method according to claim 1, comprising: The deterioration evaluation method according to claim 9, comprising introducing hydrogen atoms into the measurement sample by immersing the measurement sample in hydrofluoric acid. The deterioration evaluation method according to claim 1, wherein the silicon material is a silicon wafer. The deterioration evaluation method according to claim 1, wherein the member is a susceptor disposed in a heat treatment furnace. A silicon material manufacturing method for manufacturing a plurality of silicon materials in a silicon material manufacturing process,
The manufacturing process of the silicon material includes a process using a member having a carbon-containing surface,
Evaluating deterioration of the member by the method according to any one of claims 1 to 12, using at least one silicon material produced in the production process of the silicon material; and
As a result of the evaluation, when it is determined that the deterioration of the member exceeds an allowable level, the silicon material is manufactured in the manufacturing process of the silicon material after replacing or repairing the member;
The manufacturing method of the said silicon material containing.