JP2018148144A - Semiconductor epitaxial wafer manufacturing method, quality prediction method, and quality evaluation method - Google Patents

Abstract

A method for manufacturing a semiconductor epitaxial wafer having gettering ability and suppressing the occurrence of epitaxial defects is provided. Kind of ion, irradiation energy, dose amount, dose rate, irradiation angle, wafer temperature during irradiation, and thickness of a protective oxide film are used as ion implantation conditions, and based on at least one set of ion implantation conditions, dynamic Using a Monte Carlo method simulation, the three-dimensional concentration distribution of vacancies or interstitial elements that will be formed in a semiconductor wafer after ion implantation is calculated, and from the three-dimensional concentration distribution, the number of vacancies on the surface of the semiconductor wafer is calculated. Alternatively, the in-plane concentration distribution of interstitial elements is obtained, and based on this in-plane concentration distribution, ion implantation conditions that can suppress defects occurring in the epitaxial layer are determined. After implanting ions into the semiconductor wafer under the determined ion implantation conditions, an epitaxial layer is formed. [Selection drawing] Fig. 1

Description

  The present invention relates to a semiconductor epitaxial wafer manufacturing method, quality prediction method, and quality evaluation method.

  Metal contamination is a factor that degrades the characteristics of semiconductor devices. For example, in a back-illuminated solid-state imaging device, metal mixed in a semiconductor epitaxial wafer serving as the substrate of this device causes a dark current of the solid-state imaging device to increase and causes a defect called a white defect. The back-illuminated solid-state image sensor has a wiring layer, etc., placed below the sensor part, so that external light can be taken directly into the sensor and clearer images and videos can be taken even in dark places. In recent years, it has been widely used in mobile phones such as digital video cameras and smartphones. Therefore, it is desired to reduce white defect as much as possible.

  Metal contamination in the wafer occurs mainly in the manufacturing process of the semiconductor epitaxial wafer and the manufacturing process (device manufacturing process) of the solid-state imaging device. Metal contamination in the former semiconductor epitaxial wafer manufacturing process is caused by heavy metal particles from the components of the epitaxial growth furnace, or because the chlorine gas is used as the furnace gas during epitaxial growth, the piping material is corroded by metal. The thing by the heavy metal particle to generate | occur | produce is considered. In recent years, these metal contaminations have been improved to some extent by replacing the constituent materials of the epitaxial growth furnace with materials having excellent corrosion resistance, but are not sufficient. On the other hand, in the latter manufacturing process of the solid-state imaging device, there is a concern about heavy metal contamination of the semiconductor substrate during each process such as ion implantation, diffusion and oxidation heat treatment.

  In order to suppress such heavy metal contamination, there is a technique for forming a gettering site for capturing heavy metal in a semiconductor wafer. As one of the methods, there is known a method of implanting ions into a semiconductor wafer and then forming an epitaxial layer. In this method, the ion implantation region functions as a gettering site.

  Patent Document 1 discloses a first step of irradiating the surface of a semiconductor wafer with cluster ions to form a modified layer in which the constituent elements of the cluster ions are dissolved in the surface layer portion of the semiconductor wafer, and the semiconductor wafer. And a second step of forming an epitaxial layer on the modified layer. A method for manufacturing a semiconductor epitaxial wafer is described.

International Publication No. 2012/157162

  In order to increase the gettering capability of the modified layer formed by ion implantation, for example, in Patent Document 1, it is effective to increase the dose of cluster ions. However, if the dose amount is excessively large, many epitaxial defects are generated in the epitaxial layer formed thereafter. Patent Document 1 focuses only on the improvement of gettering capability and does not consider suppressing the occurrence of epitaxial defects, and there is room for improvement in this respect.

  In addition, the present inventors have recognized the following new technical problems. That is, it has been found that not only the dose amount but also the conditions such as ion species, irradiation energy, and beam current value affect the generation of epitaxial defects as the ion implantation conditions that affect the generation of epitaxial defects. Therefore, it has been recognized that it is necessary to develop a method for predicting or determining the ion implantation conditions that can suppress the generation of epitaxial defects in advance without trial and error without any guidance.

  In view of the above problems, an object of the present invention is to provide a method for manufacturing a semiconductor epitaxial wafer having gettering capability and suppressing the occurrence of epitaxial defects. It is another object of the present invention to provide a method for predicting the quality of an epitaxial layer of a semiconductor epitaxial wafer and a method for evaluating the quality of the epitaxial layer of a semiconductor epitaxial wafer.

  When the present inventors diligently studied to solve the above problems, the following knowledge was obtained.

  An experiment was conducted in which ions were implanted into a semiconductor wafer under various ion implantation conditions, and thereafter an epitaxial layer was formed to measure the density of epitaxial defects. Also, using the dynamic Monte Carlo simulation with each ion implantation condition as a parameter, the three-dimensional concentration distribution of vacancies that will be formed in the semiconductor wafer after ion implantation is calculated. The in-plane concentration distribution of vacancies on the surface of the semiconductor wafer was obtained. Then, it was found that there is a correlation between the in-plane concentration distribution of vacancies thus obtained and the actually measured density of epitaxial defects.

Specifically, ion species, irradiation energy, dose, dose rate (parameter corresponding to beam current value), irradiation angle, wafer temperature during irradiation, and protective oxide film thickness, which are ion implantation conditions used in the simulation No matter how many values of each of the above, in the obtained in-plane concentration distribution, there is a correlation between the area ratio of the region where the vacancy concentration is 2.0 × 10 ²² atoms / cm ³ or more and the measured density of epitaxial defects. there were. It was found that when the area ratio is 20% or less, the density of epitaxial defects can be suppressed to a low level of 0.02 pieces / cm ² or less.

The gist configuration of the present invention completed based on the above findings is as follows.
(1) a first step of implanting ions from the surface of a semiconductor wafer to form a modified layer in which the constituent elements of the ions are dissolved in the surface layer portion of the semiconductor wafer;
A second step of forming an epitaxial layer on the modified layer of the semiconductor wafer;
Have
Prior to the first step,
Dynamic Monte Carlo simulation is performed based on at least one set of ion implantation conditions, with ion species, irradiation energy, dose, dose rate, irradiation angle, wafer temperature during irradiation, and protective oxide film thickness as ion implantation conditions. And calculating a three-dimensional concentration distribution of vacancies or interstitial elements formed in the semiconductor wafer after ion implantation, and calculating the surface of the vacancies or interstitial elements on the surface of the semiconductor wafer from the three-dimensional concentration distribution. Obtaining the internal concentration distribution;
Determining ion implantation conditions capable of suppressing defects generated in the epitaxial layer based on the in-plane concentration distribution;
And performing the first step under the determined ion implantation conditions.

(2) In the determining step, in the obtained in-plane concentration distribution, an ion implantation condition in which an area ratio of a region where the concentration of vacancies or interstitial elements is 2.0 × 10 ²² atoms / cm ³ or more is 20% or less The method of manufacturing a semiconductor epitaxial wafer according to (1), wherein:

  (3) The method for producing a semiconductor epitaxial wafer according to (1) or (2) above, wherein the ions implanted in the first step are cluster ions.

(4) a first step of implanting ions from the surface of the semiconductor wafer to form a modified layer in which the constituent elements of the ions are dissolved in the surface layer portion of the semiconductor wafer;
A second step of forming an epitaxial layer on the modified layer of the semiconductor wafer;
When manufacturing a semiconductor epitaxial wafer by
Based on the ion species, irradiation energy, dose amount, dose rate, irradiation angle, wafer temperature during irradiation, and thickness of the protective oxide film in the first step, using dynamic Monte Carlo method simulation, Calculate the three-dimensional concentration distribution of vacancies or interstitial elements formed in the semiconductor wafer,
From the three-dimensional concentration distribution, obtain an in-plane concentration distribution of vacancies or interstitial elements on the surface of the semiconductor wafer,
A method for predicting the quality of a semiconductor epitaxial wafer, wherein the presence or density of defects occurring in the epitaxial layer is predicted based on the in-plane concentration distribution.

(5) In the obtained in-plane concentration distribution, if the area ratio of the region where the concentration of vacancies or interstitial elements is 2.0 × 10 ²² atoms / cm ³ or more is 20% or less, it occurs in the epitaxial layer The method for predicting the quality of a semiconductor epitaxial wafer according to (4) above, wherein the defect density is predicted to be 0.02 piece / cm ² or less.

  (6) The method for predicting the quality of a semiconductor epitaxial wafer according to (4) or (5) above, wherein the ions implanted in the first step are cluster ions.

(7) a first step of implanting ions from the surface of the semiconductor wafer to form a modified layer in which the constituent elements of the ions are dissolved in the surface layer portion of the semiconductor wafer;
A second step of forming an epitaxial layer on the modified layer of the semiconductor wafer;
Based on the ion species, irradiation energy, dose amount, dose rate, irradiation angle, wafer temperature during irradiation, and thickness of the protective oxide film in the first step, using dynamic Monte Carlo method simulation, A step of calculating a three-dimensional concentration distribution of vacancies or interstitial elements formed in a semiconductor wafer and obtaining an in-plane concentration distribution of vacancies or interstitial elements on the surface of the semiconductor wafer from the three-dimensional concentration distribution When,
Evaluating the quality of the epitaxial layer based on the in-plane concentration distribution;
A method for evaluating the quality of a semiconductor epitaxial wafer, comprising:

(8) If the area ratio of the region where the concentration of vacancies or interstitial elements is 2.0 × 10 ²² atoms / cm ³ or more in the obtained in-plane concentration distribution is 20% or less, the quality of the epitaxial layer The quality evaluation method for a semiconductor epitaxial wafer according to (7), wherein the quality is evaluated as acceptable.

  (9) The quality evaluation method for a semiconductor epitaxial wafer according to (7) or (8), wherein the ions implanted in the first step are cluster ions.

(10) a semiconductor wafer, a modified layer formed in a surface layer portion of the semiconductor wafer, in which an element of ions implanted into the semiconductor wafer is dissolved, an epitaxial layer on the modified layer, Have
In the surface of the semiconductor wafer, the area ratio of the region where the concentration of vacancies or interstitial elements is 2.0 × 10 ²² atoms / cm ³ or more is 20% or less,
A semiconductor epitaxial wafer, wherein a density of defects generated in the epitaxial layer is 0.02 piece / cm ² or less.

  (11) A solid-state imaging device is provided on the epitaxial layer of the semiconductor epitaxial wafer manufactured by the manufacturing method according to any one of (1) to (3) or the semiconductor epitaxial wafer according to (10). A method for manufacturing a solid-state imaging device, comprising: forming a solid-state imaging device.

  According to the method for producing a semiconductor epitaxial wafer of the present invention, a semiconductor epitaxial wafer having gettering capability and suppressing the occurrence of epitaxial defects can be obtained. In addition, according to the semiconductor epitaxial wafer quality prediction method and quality evaluation method of the present invention, the quality of the epitaxial layer can be predicted and evaluated.

The lower part of (A) to (D) is the three-dimensional vacancy concentration distribution calculated by the dynamic Monte Carlo method in each of Experimental Examples 1 to 4, and the upper part of (A) to (D) is the experimental example 1 to 4, respectively. 4 is an epitaxial defect map in FIG. The area ratio of the region where the vacancy concentration is 2.0 × 10 ²² atoms / cm ³ or more in the vacancy concentration distribution on the silicon wafer surface calculated using the dynamic Monte Carlo method based on Experimental Examples 1 to 18, and the epitaxial defect It is a graph which shows the relationship with the density of.

  First, the experiment that led to the completion of the present invention will be described.

(Experimental example 1)
An n-type silicon wafer (diameter: 300 mm, thickness: 725 μm, dopant: phosphorus, dopant concentration: 5.0 × 10 ¹⁴ atoms / cm ² ) obtained from a CZ single crystal silicon ingot was prepared. Next, using a cluster ion generator (manufactured by Nissin Ion Instruments Co., Ltd., model number: CLARIS), C ₃ H ₅ clusters are generated from cyclohexane, and the carbon dose is set to 1.0 × 10 ¹⁵ atoms / cm ² . Irradiated the surface of the silicon wafer to form a modified layer. The irradiation energy was 80 keV, the beam current value was 800 μA, the irradiation angle was 0 degree, the wafer temperature during irradiation was 25 ° C., and the thickness of the protective oxide film was 0.001 μm (natural oxide film).

  Carbon and hydrogen concentration profiles were measured by SIMS measurement. Since a steep peak was confirmed in the range of 200 nm from the surface of the silicon wafer, the modified layer could be identified.

Ion species at the time of ion implantation (3 carbon atoms, 5 hydrogen atoms), irradiation energy, carbon dose, dose rate (parameter corresponding to the beam current value), irradiation angle, wafer temperature at irradiation, and protective oxide film thickness The three-dimensional pore concentration distribution was calculated using a TCAD simulator Sentaurus Process (manufactured by Nippon Synopsys Godo Kaisha), which can calculate dynamic Monte Carlo (KMC) method simulation, using the thickness as a parameter. The results are shown in the lower part of FIG. The surface of this three-dimensional vacancy concentration distribution is the surface of the silicon wafer (the surface of the modified layer). In FIG. 1 (A), blue / light blue / green / black line / green / yellow / red are displayed in order from the smallest vacancy concentration, and the black line in the area displayed in green represents the vacancy concentration. The line is 2.0 × 10 ²² atoms / cm ³ . The same applies to FIGS. 1B to 1D. From FIG. 1A, in the in-plane vacancy concentration distribution on the surface of this silicon wafer, the area ratio of the region where the vacancy concentration is 2.0 × 10 ²² atoms / cm ³ or more was 0%.

After that, the silicon wafer is transferred into a single wafer epitaxial growth apparatus (Applied Materials Co., Ltd.) and subjected to a hydrogen baking process at a temperature of 1120 ° C for 30 seconds, and then hydrogen is used as a carrier gas and trichlorosilane as a source. A silicon epitaxial layer (thickness: 5 μm, dopant: phosphorus, dopant concentration: 1.0 × 10 ¹⁵ atoms / cm ³ ) is epitaxially grown on the modified layer of the silicon wafer by CVD at 1150 ° C. as a gas. Obtained.

  The surface of the silicon epitaxial layer of the epitaxial silicon wafer is measured in the Normal mode with Surfscan SP1 (manufactured by KLA-Tencor). Of those counted as LPD of 90 nm or more, those counted as LPD-N are epitaxial. It was defined as a defect. An epitaxial defect map on the wafer is shown in the upper part of FIG.

As described above, in the in-plane vacancy concentration distribution on the surface of the silicon wafer, when the area ratio of the region where the vacancy concentration is 2.0 × 10 ²² atoms / cm ³ or more is 0%, no epitaxial defect occurred. .

(Experimental example 2)
The same experiment as in Experimental Example 1 was performed except that the carbon dose was 2.0 × 10 ¹⁵ atoms / cm ² . The three-dimensional vacancy concentration is shown in the lower part of FIG. In the in-plane vacancy concentration distribution on the surface of the silicon wafer, the area ratio of the region where the vacancy concentration is 2.0 × 10 ²² atoms / cm ³ or more was 25%. From the epitaxial defect map shown in the upper part of FIG. 1B, the density of epitaxial defects was 0.0241 / cm ² .

(Experimental example 3)
An experiment similar to the experiment example 1 was performed except that the dose amount of carbon was set to 5.0 × 10 ¹⁵ atoms / cm ² . The three-dimensional vacancy concentration is shown in the lower part of FIG. In the in-plane vacancy concentration distribution on the surface of the silicon wafer, the area ratio of the region where the vacancy concentration is 2.0 × 10 ²² atoms / cm ³ or more was 90%. From the epitaxial defect map shown in the upper part of FIG. 1C, the density of epitaxial defects was 0.1150 / cm ² .

(Experimental example 4)
An experiment similar to the experiment example 1 was performed except that the dose amount of carbon was set to 1.0 × 10 ¹⁶ atoms / cm ² . The lower part of FIG. 1D shows a three-dimensional vacancy concentration distribution. In the in-plane vacancy concentration distribution on the surface of the silicon wafer, the area ratio of the region where the vacancy concentration is 2.0 × 10 ²² atoms / cm ³ or more was 100%. From the epitaxial defect map shown in the upper part of FIG. 1D, the density of epitaxial defects was 0.1410 / cm ² .

(Experimental Examples 5 to 18)
Table 1 shows the ion species, irradiation energy, carbon dose, beam current value, irradiation angle, wafer temperature at the time of irradiation, and the thickness of the protective oxide film. Table 1 also shows the area ratio of the region where the vacancy concentration is 2.0 × 10 ²² atoms / cm ³ or more in the vacancy concentration distribution on the silicon wafer surface calculated using the KMC method simulation and the measured density of epitaxial defects. Shown in Table 1 also shows information on the previous experimental examples 1 to 4. FIG. 2 shows the relationship between the area ratio of the region where the vacancy concentration is 2.0 × 10 ²² atoms / cm ³ or more and the density of epitaxial defects based on Experimental Examples 1 to 18.

As is apparent from Table 1 and FIG. 2, the area ratio of the region where the vacancy concentration in the vacancy concentration distribution on the silicon wafer surface calculated using the KMC method is 2.0 × 10 ²² atoms / cm ³ or more, and the actual measurement There was a correlation with the density of the formed epitaxial defects. When the area ratio was 20% or less, the density of epitaxial defects could be suppressed to a low level of 0.02 pieces / cm ² or less.

(Method of manufacturing semiconductor epitaxial wafer)
Based on the above experimental results, a method for manufacturing a semiconductor epitaxial wafer according to an embodiment of the present invention will be described. According to an embodiment of the present invention, there is provided a method for manufacturing a semiconductor epitaxial wafer, wherein ions are implanted from a surface of a semiconductor wafer to form a modified layer in which a constituent element of the ions is dissolved in a surface layer portion of the semiconductor wafer. And a second step of forming an epitaxial layer on the modified layer of the semiconductor wafer. The epitaxial layer becomes a device layer for manufacturing a semiconductor element such as a backside illumination type solid-state imaging element.

  Examples of semiconductor wafers include bulk single crystal wafers made of silicon and compound semiconductors (GaAs, GaN, SiC) and having no epitaxial layer on the surface. A bulk single crystal silicon wafer is used. In addition, a semiconductor wafer obtained by slicing a single crystal silicon ingot grown by the Czochralski method (CZ method) or the floating zone melting method (FZ method) with a wire saw or the like can be used. In order to obtain a higher gettering capability, carbon and / or nitrogen may be added to the semiconductor wafer. Furthermore, a predetermined concentration of an arbitrary dopant may be added to the semiconductor wafer to form a so-called n + type or p + type, or n− type or p− type substrate.

  Further, as the semiconductor wafer, an epitaxial semiconductor wafer in which a semiconductor epitaxial layer is formed on the surface of the bulk semiconductor wafer may be used. For example, an epitaxial silicon wafer in which a silicon epitaxial layer is formed on the surface of a bulk single crystal silicon wafer. The silicon epitaxial layer can be formed under general conditions by a CVD method. The thickness of the epitaxial layer is preferably in the range of 0.1 to 10 μm, and more preferably in the range of 0.2 to 5 μm.

  The ions to be implanted may be monomer ions or cluster ions. The modified layer formed as a result of ion implantation functions as a gettering layer. Here, the “cluster ion” means an ionized product in which a plurality of atoms or molecules are gathered to give a positive or negative charge to a cluster. A cluster is a massive group in which a plurality (usually about 2 to 2000) of atoms or molecules are bonded to each other. From the viewpoint of obtaining higher gettering capability, it is preferable to implant cluster ions. As the monomer ion generator or the cluster ion generator, a conventional apparatus can be used.

  Examples of the epitaxial layer formed on the modified layer include a silicon epitaxial layer, which can be formed under general conditions. For example, a source gas such as dichlorosilane or trichlorosilane is introduced into the chamber using hydrogen as a carrier gas, and the growth temperature varies depending on the source gas used, but the semiconductor is formed by CVD at a temperature in the range of about 1000 to 1200 ° C. It can be epitaxially grown on the wafer 10. The epitaxial layer preferably has a thickness in the range of 1 to 15 μm. If the thickness is less than 1 μm, the resistivity of the epitaxial layer may change due to the outward diffusion of the dopant from the semiconductor wafer. If the thickness exceeds 15 μm, the spectral sensitivity characteristics of the solid-state imaging device may be affected. Because there is.

Here, the feature of the present embodiment resides in a method of determining ion implantation conditions that can suppress the occurrence of epitaxial defects prior to the first step. If the ion implantation conditions of the experimental example in which the area ratio of the region where the vacancy concentration is 2.0 × 10 ²² atoms / cm ³ or more is 20% or less are adopted, the epitaxial defects are suppressed. It is certain that it can be done. However, this is not versatile, and it is important to predict and determine under what ion implantation conditions other than these conditions the epitaxial defects can be suppressed.

According to the above experimental results, the area ratio of the region where the vacancy concentration is 2.0 × 10 ²² atoms / cm ³ or more in the vacancy concentration distribution on the silicon wafer surface calculated using the KMC method, and the measured epitaxial defects There was a correlation with the density. Therefore, at least one set of ion implantation is performed using ion species, irradiation energy, dose, dose rate (parameter corresponding to the beam current value), irradiation angle, wafer temperature during irradiation, and protective oxide film thickness as ion implantation conditions. Based on the conditions, the KCM method simulation is used to calculate the three-dimensional concentration distribution of vacancies that will be formed in the semiconductor wafer after ion implantation, and from this three-dimensional concentration distribution, the vacancy on the surface of the semiconductor wafer is calculated. A step of obtaining an in-plane concentration distribution and a step of determining an ion implantation condition capable of suppressing defects generated in the epitaxial layer from the calculation result are performed, and the first step is performed under the determined ion implantation condition. Thereby, generation | occurrence | production of an epitaxial defect can be suppressed.

Specifically, the ion implantation conditions are preferably determined so that the area ratio of the region where the vacancy concentration is 2.0 × 10 ²² atoms / cm ³ or more in the acquired in-plane concentration distribution is 20% or less. As a result, the density of epitaxial defects can be suppressed to a low level of 0.02 / cm ² or less.

For example, when a three-dimensional vacancy concentration distribution is calculated using the KMC method for an arbitrary set of ion implantation conditions (parameter set) and the vacancy concentration distribution on the silicon wafer surface is acquired, the vacancy concentration is 2.0. If the area ratio of the region of × 10 ²² atoms / cm ³ or more is 20% or less, the ion implantation conditions can be adopted.

Alternatively, the three-dimensional vacancy concentration distribution is sequentially calculated using the KMC method for any plurality of ion implantation conditions (parameter sets), and the vacancy concentration distribution on the silicon wafer surface obtained from each three-dimensional vacancy concentration distribution. In this case, the ion implantation condition may be adopted when the ion implantation condition in which the area ratio of the region where the vacancy concentration is 2.0 × 10 ²² atoms / cm ³ or more is found to be 20% or less has been discovered.

Alternatively, the three-dimensional vacancy concentration distribution is calculated by using the KMC method for a plurality of arbitrary ion implantation conditions (parameter sets), and the vacancy concentration distribution on the silicon wafer surface is obtained from each three-dimensional vacancy concentration distribution. Then, one ion implantation condition is selected so that, in the vacancy concentration distribution on the silicon wafer surface, the area ratio of the region where the vacancy concentration is 2.0 × 10 ²² atoms / cm ³ or more is 20% or less. May be adopted.

  In the calculation of the pore concentration distribution by the KMC method, it is essential to use the above seven types of parameters as one parameter set. For ion species, enter the type and number of elements. The dose rate is a parameter corresponding to the beam current as the irradiation condition in the ion irradiation apparatus, and is input when calculating the hole concentration distribution by the KMC method in the present invention. The dose rate means the number of ions that collide per unit area per second. In an ion irradiation apparatus, as an irradiation condition corresponding to a dose rate, there is an index called a beam current value obtained by measuring a current generated by charge transfer with a substrate when ions collide, but the parameters used in the calculation of the KMC method are It is a dose rate.

  In the above experimental example, the calculation of the vacancy concentration distribution by the KMC method is M. Jaraiz, “Atomic Scale Simulations of Arsenic Ion Implantation and Annealing in Silicon” Mater. Res. Soc. Symp. Proc. 54, 532 (1998). The above-described program was carried out by KMC simulation of ion implantation using the model described in 1. In the present embodiment, it is necessary to use the KMC method instead of the Monte Carlo (MC) method. Thereby, the three-dimensional concentration distribution of vacancies can be calculated.

When calculating a plurality of sets of ion implantation conditions and searching for ion implantation conditions in which the area ratio of the region where the vacancy concentration is 2.0 × 10 ²² atoms / cm ³ or more is 20% or less, All may be performed as variables, or some of the parameters may be performed as constants. Considering the setting restrictions of the ion implantation system, the dose rate (parameter corresponding to the beam current value), the irradiation angle, the wafer temperature at the time of irradiation, and the thickness of the protective oxide film are relatively fixed among the seven parameters. It's easy to do. Therefore, constants are input as these four types of parameters, and variables are input as the parameters of the remaining ion species, irradiation energy, and dose, and three-dimensional emptying is performed using the KMC method for a plurality of sets of ion implantation conditions. The pore concentration distribution may be calculated. This facilitates the search for ion implantation conditions in which the area ratio of the region where the vacancy concentration is 2.0 × 10 ²² atoms / cm ³ or more is 20% or less. Of course, the type and number of parameters for inputting constants (fixed parameters) and parameters for inputting variables are not limited to the above.

  The vacancy concentration and the interstitial element concentration correspond one to one. This is because when one hole is generated, one interstitial element is generated. Therefore, instead of the three-dimensional vacancy concentration distribution, the three-dimensional concentration distribution of the interstitial elements is calculated, and the in-plane concentration distribution of the interstitial elements on the surface of the semiconductor wafer is obtained from the three-dimensional concentration distribution. Good.

  The ion implantation conditions in the first step are determined as described above, but generally fall within the following ranges.

  First, the irradiation element is not particularly limited as long as it contributes to gettering, and examples thereof include carbon, boron, phosphorus, and arsenic. However, from the viewpoint of obtaining higher gettering ability, the cluster ions preferably contain carbon as a constituent element. In addition, hydrogen, oxygen, fluorine, or the like may be included.

  Moreover, as an irradiation element, 2 or more types of elements containing carbon are more preferable. In particular, it is preferable to irradiate one or more dopant elements selected from the group consisting of boron, phosphorus, arsenic and antimony in addition to carbon. This is because the types of metals that can be efficiently gettered differ depending on the types of elements to be dissolved, so that a wider range of metal contamination can be dealt with by dissolving two or more elements in solid solutions. For example, in the case of carbon, nickel can be efficiently gettered, and in the case of boron, copper and iron can be efficiently gettered.

A compound to be ionized is not particularly limited, and ethane, methane, carbon dioxide (CO ₂ ), or the like can be used as a carbon source compound that can be ionized, and diborane, decaborane ( B ₁₀ H ₁₄ ) or the like can be used. For example, when a gas obtained by mixing dibenzyl and decaborane is used as a material gas, a hydrogen compound cluster in which carbon, boron and hydrogen are aggregated can be generated. If cyclohexane (C ₆ H ₁₂ ) is used as a material gas, cluster ions composed of carbon and hydrogen can be generated. As the carbon source compound, it is particularly preferable to use a cluster C _n H _m (3 ≦ n ≦ 16, 3 ≦ m ≦ 10) formed from pyrene (C ₁₆ H ₁₀ ), dibenzyl (C ₁₄ H ₁₄ ) or the like. This is because it is easy to control a small-sized cluster ion beam.

  As the compound to be ionized, a compound containing both carbon and the above dopant element is also preferable. This is because if such a compound is irradiated as cluster ions, both carbon and the dopant element can be dissolved in a single irradiation.

When cluster ions are implanted, the cluster size can be appropriately set to 2 to 100, preferably 60 or less, more preferably 50 or less. In the above experimental example, C ₃ H _{5 with} 8 cluster sizes is used. C ₅ H ₅ having a cluster size of 10 was used.

  The irradiation energy is generally in the range of 5 to 200 keV in both cases where monomer ions are implanted and cluster ions are implanted.

The ion dose can be adjusted by controlling the ion implantation time, and is generally in the range of 1.0 × 10 ^{13 to} 5.0 × 10 ¹⁵ atoms / cm ² . As in the above experimental example, when the ions to be implanted are only carbon and hydrogen, the dose used for calculating the three-dimensional vacancy concentration distribution is the dose amount of carbon. Thus, in the calculation in this embodiment, the dose amount of elements other than hydrogen is used. The reason for not considering the hydrogen dose is that in the formation of vacancies, the concentration of vacancies formed by elements other than carbon and hydrogen is two or more orders of magnitude higher than the concentration of vacancies formed by hydrogen. This is because the dose amount of elements other than carbon and hydrogen is more dominant in the formation of vacancies than the amount.

The beam current value is generally in the range of 100 μA to 3000 μA. The dose rate corresponding to this range is 1.0 × 10 ^{12 to} 5.0 × 10 ¹⁴ . Further, the irradiation angle of ions with respect to the wafer surface is generally in the range of -7.0 to 7.0 degrees.

  The wafer temperature during irradiation can be set to room temperature. Further, by making the temperature lower than 25 ° C., more preferably by setting it to 0 ° C. or less, higher gettering ability can be obtained. The wafer temperature during irradiation is preferably −200 ° C. or higher, more preferably −120 ° C. or higher.

  A protective oxide film may be formed on the surface of the semiconductor wafer before ion implantation, and the thickness thereof is not particularly limited, but can be 0 to 0.025 μm. When the protective oxide film is not intentionally formed, a value of 0.001 μm is input assuming a natural oxide film, and calculation by the KMC method is performed.

(Quality prediction method of semiconductor epitaxial wafer)
According to the above experimental results, it can be seen that the quality of the semiconductor epitaxial wafer can be predicted when the semiconductor epitaxial wafer is manufactured by the first step and the second step.

  The method for predicting the quality of a semiconductor epitaxial wafer according to the present embodiment uses the KCM method simulation based on the above-described seven types of conditions in the first step, and the void that will be formed on the semiconductor wafer after ion implantation. A three-dimensional concentration distribution of holes or interstitial elements is calculated, and from this three-dimensional concentration distribution, an in-plane concentration distribution of vacancies or interstitial elements on the surface of the semiconductor wafer is obtained, and based on this in-plane concentration distribution The presence or density of defects occurring in the epitaxial layer is predicted.

For example, in the obtained in-plane concentration distribution, if the area ratio of the region where the concentration of vacancies or interstitial elements is 2.0 × 10 ²² atoms / cm ³ or more is 20% or less, the density of defects generated in the epitaxial layer Can be estimated to be 0.02 pieces / cm ² or less.

(Quality evaluation method of semiconductor epitaxial wafer)
Moreover, according to the said experimental result, it turns out that the quality of the semiconductor epitaxial wafer manufactured by the said 1st process and the 2nd process can also be evaluated.

  The quality evaluation method of the semiconductor epitaxial wafer according to the present embodiment is based on the above-mentioned seven kinds of conditions in the first step, and the vacancies that would have been formed in the semiconductor wafer after ion implantation using the KCM method simulation. Alternatively, a process of calculating a three-dimensional concentration distribution of interstitial elements, obtaining an in-plane concentration distribution of vacancies or interstitial elements on the surface of the semiconductor wafer from the three-dimensional concentration distribution, and based on the in-plane concentration distribution And a step of evaluating the quality of the epitaxial layer.

For example, in the obtained in-plane concentration distribution, if the area ratio of the region where the concentration of vacancies or interstitial elements is 2.0 × 10 ²² atoms / cm ³ or more is 20% or less, the quality of the epitaxial layer is evaluated as acceptable. can do.

(Semiconductor epitaxial wafer)
The semiconductor epitaxial wafer of the present embodiment is a modified product obtained by solid solution of the semiconductor wafer obtained by the above manufacturing method and formed in the surface layer portion of the semiconductor wafer and ions implanted into the semiconductor wafer. And a epitaxial layer on the modified layer.

In the surface of the semiconductor wafer, the area ratio of the region where the concentration of vacancies or interstitial elements is 2.0 × 10 ²² atoms / cm ³ or more is 20% or less, and the density of defects generated in the epitaxial layer is It is characterized by 0.02 piece / cm ² or less.

  The conditions for manufacturing the epitaxial silicon wafer of the present embodiment are appropriately selected from the irradiation conditions such as dose, cluster type, acceleration voltage, and beam current value based on the cluster ion irradiation conditions employed in the above experimental example. That's fine.

(Method for manufacturing solid-state imaging device)
A method for manufacturing a solid-state imaging device according to an embodiment of the present invention includes forming a solid-state imaging device on a semiconductor epitaxial wafer manufactured by the above-described manufacturing method or the above-described semiconductor epitaxial wafer, that is, an epitaxial layer positioned on the surface of the semiconductor epitaxial wafer. It is characterized by doing. The solid-state imaging device obtained by this manufacturing method can sufficiently suppress the occurrence of white defect as compared with the conventional case.

The semiconductor epitaxial wafer manufactured, quality-predicted, or quality-evaluated by this invention can be used for manufacture of various semiconductor devices, such as a solid-state image sensor.

Claims (11)

A first step of implanting ions from the surface of the semiconductor wafer to form a modified layer in which the constituent elements of the ions are dissolved in the surface layer portion of the semiconductor wafer;
A second step of forming an epitaxial layer on the modified layer of the semiconductor wafer;
Have
Prior to the first step,
Dynamic Monte Carlo simulation is performed based on at least one set of ion implantation conditions, with ion species, irradiation energy, dose, dose rate, irradiation angle, wafer temperature during irradiation, and protective oxide film thickness as ion implantation conditions. And calculating a three-dimensional concentration distribution of vacancies or interstitial elements formed in the semiconductor wafer after ion implantation, and calculating the surface of the vacancies or interstitial elements on the surface of the semiconductor wafer from the three-dimensional concentration distribution. Obtaining the internal concentration distribution;
Determining ion implantation conditions capable of suppressing defects generated in the epitaxial layer based on the in-plane concentration distribution;
And performing the first step under the determined ion implantation conditions. In the determining step, in the acquired in-plane concentration distribution, ion implantation conditions are determined such that the area ratio of a region where the concentration of vacancies or interstitial elements is 2.0 × 10 ²² atoms / cm ³ or more is 20% or less. The manufacturing method of the semiconductor epitaxial wafer of Claim 1.   The method for producing a semiconductor epitaxial wafer according to claim 1, wherein the ions implanted in the first step are cluster ions. A first step of implanting ions from the surface of the semiconductor wafer to form a modified layer in which the constituent elements of the ions are dissolved in the surface layer portion of the semiconductor wafer;
A second step of forming an epitaxial layer on the modified layer of the semiconductor wafer;
When manufacturing a semiconductor epitaxial wafer by
Based on the ion species, irradiation energy, dose amount, dose rate, irradiation angle, wafer temperature during irradiation, and thickness of the protective oxide film in the first step, using dynamic Monte Carlo method simulation, Calculate the three-dimensional concentration distribution of vacancies or interstitial elements formed in the semiconductor wafer,
From the three-dimensional concentration distribution, obtain an in-plane concentration distribution of vacancies or interstitial elements on the surface of the semiconductor wafer,
A method for predicting the quality of a semiconductor epitaxial wafer, wherein the presence or density of defects occurring in the epitaxial layer is predicted based on the in-plane concentration distribution. In the obtained in-plane concentration distribution, if the area ratio of the region where the concentration of vacancies or interstitial elements is 2.0 × 10 ²² atoms / cm ³ or more is 20% or less, the density of defects generated in the epitaxial layer 5. The method for predicting the quality of a semiconductor epitaxial wafer according to claim 4, wherein the quality is predicted to be 0.02 pieces / cm ² or less.   The method for predicting the quality of a semiconductor epitaxial wafer according to claim 4 or 5, wherein the ions implanted in the first step are cluster ions. A first step of implanting ions from the surface of the semiconductor wafer to form a modified layer in which the constituent elements of the ions are dissolved in the surface layer portion of the semiconductor wafer;
A second step of forming an epitaxial layer on the modified layer of the semiconductor wafer;
Based on the ion species, irradiation energy, dose amount, dose rate, irradiation angle, wafer temperature during irradiation, and thickness of the protective oxide film in the first step, using dynamic Monte Carlo method simulation, A step of calculating a three-dimensional concentration distribution of vacancies or interstitial elements formed in a semiconductor wafer and obtaining an in-plane concentration distribution of vacancies or interstitial elements on the surface of the semiconductor wafer from the three-dimensional concentration distribution When,
Evaluating the quality of the epitaxial layer based on the in-plane concentration distribution;
A method for evaluating the quality of a semiconductor epitaxial wafer, comprising: In the obtained in-plane concentration distribution, if the area ratio of the region where the concentration of vacancies or interstitial elements is 2.0 × 10 ²² atoms / cm ³ or more is 20% or less, the quality of the epitaxial layer is evaluated as acceptable. The method for evaluating a quality of a semiconductor epitaxial wafer according to claim 7.   The quality evaluation method for a semiconductor epitaxial wafer according to claim 7 or 8, wherein the ions implanted in the first step are cluster ions. A semiconductor wafer, a modified layer formed on a surface layer portion of the semiconductor wafer, in which an element of ions implanted into the semiconductor wafer is dissolved, and an epitaxial layer on the modified layer; ,
In the surface of the semiconductor wafer, the area ratio of the region where the concentration of vacancies or interstitial elements is 2.0 × 10 ²² atoms / cm ³ or more is 20% or less,
A semiconductor epitaxial wafer, wherein a density of defects generated in the epitaxial layer is 0.02 piece / cm ² or less. A solid-state imaging device is formed on the epitaxial layer of the semiconductor epitaxial wafer manufactured by the manufacturing method according to claim 1 or the semiconductor epitaxial wafer according to claim 10. Manufacturing method of solid-state image sensor.