JP7400663B2 - Evaluation method of hydrogen concentration in silicon single crystal substrate - Google Patents

Description

The present invention relates to a method for evaluating hydrogen concentration in a silicon single crystal substrate.

Silicon single crystal substrates are widely used as substrates for semiconductor devices. Hydrogen is introduced into the silicon single crystal substrate during various steps in the silicon single crystal substrate manufacturing process and semiconductor device manufacturing process (for example, cleaning process, chemical etching process, plasma etching process, sputtering process, etc.). It has been known.

Hydrogen introduced into the silicon single crystal substrate inactivates pre-contained dopants, reacts with pre-contained light element impurities such as carbon and oxygen to form donors, and It combines with dangling bonds and changes their electronic state. For this reason, when hydrogen is introduced into a silicon single crystal substrate, it affects the electrical characteristics of a semiconductor device, and therefore it is important to evaluate the concentration of hydrogen introduced into a silicon single crystal substrate.

Secondary ion mass spectrometry (SIMS) is an example of a method for measuring the hydrogen concentration in a silicon single crystal substrate. In SIMS, the type and concentration of elements contained in a sample are measured by irradiating the sample surface with primary ions in a vacuum and mass spectrometry the secondary ions released from the sample. Furthermore, SIMS makes it possible to measure the depth distribution of elements by using sputtering of the sample surface by primary ions. When measuring the distribution of hydrogen concentration in the depth direction by SIMS, the lower detection limit of hydrogen concentration is about 1×10 ¹⁶ atoms/cm ³ .

Furthermore, in Patent Document 1, a hydrogen-doped crystal with a known hydrogen concentration and a silicon crystal to be measured are heat-treated under the same conditions to generate a thermal donor, and the thermal donor concentration is compared between these crystals. A method is disclosed in which the hydrogen concentration of a hydrogen-doped crystal having the same donor concentration as that of a silicon crystal to be measured is used as a measured value of the hydrogen concentration of a silicon crystal to be measured.

Japanese Patent Application Publication No. 07-066256

As mentioned above, since hydrogen introduced into a silicon single crystal substrate affects the electrical characteristics of a semiconductor device, it is important to evaluate the concentration of hydrogen introduced in various steps.

However, the conventional secondary ion mass spectrometry method described above has a problem of low sensitivity to hydrogen concentration.

Furthermore, the technique disclosed in Patent Document 1 has a problem in that preparation of a hydrogen-doped crystal and heat treatment for generating a thermal donor require time and cost. Furthermore, in order to generate a thermal donor by heat treatment, the hydrogen-doped crystal and the silicon crystal to be measured must contain oxygen at a high concentration, which poses a problem in that the specifications of the silicon crystal are limited.

The present invention has been made in view of the problems of the prior art described above, and an object of the present invention is to provide a method that can easily and highly sensitively evaluate the concentration of hydrogen introduced into a silicon single crystal substrate. shall be.

In order to achieve the above object, the present invention provides a method for evaluating hydrogen concentration in a silicon single crystal substrate, comprising:
a step of preparing a target silicon single crystal substrate;
evaluating the hydrogen concentration in the target silicon single crystal substrate by measuring the distribution of carrier concentration change in the depth direction with respect to the target silicon single crystal substrate. A method for evaluating hydrogen concentration in a silicon single crystal substrate is provided.

Hydrogen introduced during the manufacturing process of silicon single crystal substrates inactivates dopants and generates donors without additional heat treatment, so hydrogen is introduced into carriers in the region of the silicon single crystal substrate where hydrogen is introduced. Concentration changes. Therefore, by measuring the distribution of the change in carrier concentration in the depth direction for the target silicon single crystal substrate as described above, it is possible to determine the hydrogen concentration in the silicon single crystal substrate of the product and the evaluation target. The hydrogen concentration introduced in the hydrogen introduction step can be easily evaluated with high sensitivity.

At this time, in the step of evaluating the hydrogen concentration, the distribution of the measured carrier concentration variation in the depth direction can be evaluated as the distribution of the hydrogen concentration in the target silicon single crystal substrate.

As described above, in the method for evaluating hydrogen concentration in a silicon single crystal substrate of the present invention, the distribution of the measured carrier concentration change in the depth direction is directly used as the distribution of hydrogen concentration in the target silicon single crystal substrate. can be evaluated.

At this time, it is preferable to prepare a silicon single crystal substrate with a dopant concentration of 1×10 ¹⁴ atoms/cm ³ or less as the target silicon single crystal substrate, and a silicon single crystal substrate with a dopant concentration of 7×10 ¹² atoms/cm ³ or less. More preferably, a silicon single crystal substrate is prepared.

In this way, if the dopant concentration of the target silicon single crystal substrate is 1×10 ¹⁴ atoms/cm ³ or less, more preferably 7×10 ¹² atoms/cm ³ or less, the dopant concentration in the silicon single crystal substrate is Since the concentration of the dopant is low, changes in carrier concentration due to hydrogen introduced during the manufacturing process can be evaluated with high sensitivity, and as a result, the hydrogen concentration introduced during the manufacturing process can be evaluated with high sensitivity. .

At this time, the step of preparing the target silicon single crystal substrate includes:
a substep of preparing a silicon single crystal substrate;
a substep of removing hydrogen contained in the prepared silicon single crystal substrate by subjecting the prepared silicon single crystal substrate to heat treatment at 250° C. or higher in an atmosphere other than hydrogen;
a substep of introducing hydrogen into the heat-treated silicon single crystal substrate,
The target silicon single crystal substrate can be prepared.

By subjecting the silicon single crystal substrate to heat treatment at 250°C or higher in an atmosphere other than hydrogen, hydrogen pre-contained in the silicon single crystal substrate can be effectively diffused and removed. Hydrogen introduced only in the substep in which hydrogen is introduced can be evaluated with high sensitivity.

Further, at this time, the sub-step of introducing hydrogen may include one or more of a cleaning process, a chemical etching process, a plasma etching process, and a sputtering process.

When these steps are performed on a silicon single crystal substrate, hydrogen can be introduced into the silicon single crystal substrate, so the concentration of hydrogen introduced in these steps can be evaluated with high sensitivity.

Further, at this time, as the silicon single crystal substrate to be prepared, one whose conductivity type is P type can be prepared.

If the conductivity type of the silicon single crystal substrate is P type, it is possible to evaluate with high sensitivity the change in carrier concentration due to hydrogen introduced into the silicon single crystal substrate during the manufacturing process. The hydrogen concentration can be evaluated with high sensitivity.

In the step of evaluating the hydrogen concentration, the distribution of the amount of change in the carrier concentration in the depth direction can be measured using a spreading resistance measurement method.

To measure the distribution of the amount of change in carrier concentration in the depth direction, for example, a commonly used spreading resistance measurement method can be used. In this way, since the amount of change in carrier concentration can be easily evaluated with high sensitivity using a commonly used measurement method, the hydrogen concentration in a silicon single crystal substrate can be evaluated easily and with high sensitivity.

As described above, according to the method for evaluating hydrogen concentration in a silicon single crystal substrate of the present invention, a silicon single crystal substrate of a product or a silicon single crystal substrate after undergoing a process in which hydrogen to be evaluated is introduced. On the other hand, by measuring the distribution of the change in carrier concentration in the silicon single crystal substrate in the depth direction, the hydrogen concentration of the silicon single crystal substrate of the product or the silicon single crystal substrate introduced in the process to be evaluated can be evaluated. Therefore, hydrogen concentration can be easily evaluated with high sensitivity compared to conventional techniques which have low sensitivity to hydrogen concentration and are laborious and costly. That is, according to the present invention, it is possible to provide a method that allows the concentration of hydrogen introduced into a silicon single crystal substrate to be easily evaluated with high sensitivity.

As described above, by easily and highly sensitively evaluating the hydrogen concentration according to the present invention, it is possible to quantitatively evaluate the hydrogen concentration introduced in each step in the manufacturing of silicon single crystal substrates and semiconductor devices as products. In addition, since it is possible to quantitatively evaluate changes in the concentration of hydrogen introduced when changing process conditions, it is useful when controlling the concentration of hydrogen introduced in each process to prevent or improve the electrical characteristics of semiconductor devices. It is valid.

FIG. 2 is a diagram showing a flow of a method for evaluating hydrogen concentration in a silicon single crystal substrate according to the present invention. FIG. 2 is a diagram showing a flow of an example of a method for evaluating hydrogen concentration in a silicon single crystal substrate according to the present invention. 3 is a diagram showing the distribution of resistivity in the depth direction measured in Example 1. FIG. 3 is a diagram showing the distribution of carrier concentration in the depth direction measured in Example 1. FIG. FIG. 3 is a diagram showing the distribution in the depth direction of the amount of change in carrier concentration measured in Example 1. 3 is a diagram showing the distribution of resistivity in the depth direction measured in Example 2. FIG. 3 is a diagram showing the distribution of carrier concentration in the depth direction measured in Example 2. FIG. 3 is a diagram showing a distribution in the depth direction of the amount of change in carrier concentration measured in Example 2. FIG. FIG. 7 is a diagram showing the distribution of resistivity in the depth direction measured in Example 3. FIG. 7 is a diagram showing the distribution of carrier concentration in the depth direction measured in Example 3. FIG. 7 is a diagram showing the distribution in the depth direction of the amount of change in carrier concentration measured in Example 3. FIG. 7 is a diagram showing the distribution of resistivity in the depth direction measured in Example 4. FIG. 7 is a diagram showing the distribution of carrier concentration in the depth direction measured in Example 4. FIG. 7 is a diagram showing the distribution in the depth direction of the amount of change in carrier concentration measured in Example 4. FIG. 7 is a diagram showing the distribution of hydrogen concentration in the depth direction measured in a comparative example.

As described above, the conventional techniques have problems such as low sensitivity to hydrogen concentration and the need to generate thermal donors by preparing and heat-treating hydrogen-doped crystals, which is time consuming and costly.

Therefore, there has been a need to develop a method that can easily and highly sensitively evaluate the concentration of hydrogen introduced into a silicon single crystal substrate.

Therefore, the inventors of the present invention have conducted intensive studies on a method that can more easily and highly sensitively evaluate the hydrogen concentration in a silicon single crystal substrate, and found that the amount of change in carrier concentration in the depth direction with respect to a silicon single crystal substrate is We have discovered that by evaluating the hydrogen concentration in the silicon single crystal substrate by measuring the distribution of , completed the present invention.

That is, the present invention is a method for evaluating hydrogen concentration in a silicon single crystal substrate, comprising:
a step of preparing a target silicon single crystal substrate;
evaluating the hydrogen concentration in the target silicon single crystal substrate by measuring the distribution of carrier concentration change in the depth direction with respect to the target silicon single crystal substrate. This is a characteristic method for evaluating hydrogen concentration in a silicon single crystal substrate.

Hereinafter, the method for evaluating hydrogen concentration in a silicon single crystal substrate according to the present invention will be explained in more detail with reference to FIG.

As shown in FIG. 1, the method for evaluating hydrogen concentration in a silicon single crystal substrate of the present invention includes step S1 of preparing a target silicon single crystal substrate, and evaluating the hydrogen concentration in the target silicon single crystal substrate. step S2. Each step will be explained in more detail below.

[Step S1 of preparing a target silicon single crystal substrate]
First, a step (first step, S1 in FIG. 1) of preparing a target silicon single crystal substrate is performed. The method of preparing the target silicon single crystal substrate is not particularly limited in the present invention. For example, a silicon wafer is cut from a silicon single crystal grown by the floating zone method (FZ method) or Czochralski method (CZ method), and after chemical etching is performed on the silicon wafer to remove cutting damage, the silicon wafer is machined. By performing chemical polishing, the target silicon single crystal substrate can be prepared.

Step S1 of preparing a target silicon single crystal substrate may include substeps _SA , _SB , and _SC shown in FIG. 2, for example. Each substep will be explained below.

First, substep _SA is performed to prepare a silicon single crystal substrate. The silicon single crystal substrate here can be prepared, for example, by the method described above.

Next, a sub-step S _B is performed in which hydrogen contained in the silicon single crystal substrate prepared above is removed by subjecting the silicon single crystal substrate prepared above to heat treatment at 250° C. or higher in an atmosphere other than hydrogen. conduct.

The upper limit of the heat treatment temperature is not particularly limited in the present invention, but can be 400°C or less. By setting the heat treatment temperature to 400°C or less, even if the prepared silicon single crystal substrate contains a high concentration of oxygen, it is possible to suppress the generation of thermal donors and oxygen precipitates. It is possible to suppress metal contamination, which becomes more pronounced as the temperature increases.

The heat treatment time can be, for example, 10 minutes or more and 60 minutes or less. By setting the heat treatment time to, for example, 10 minutes or more and 60 minutes or less, hydrogen pre-contained in the silicon single crystal substrate can be effectively diffused and removed, and the heat treatment time is longer, making it more efficient. You can avoid losing it.

Further, the atmosphere for the heat treatment does not need to be an atmosphere intentionally containing hydrogen, and may be, for example, the atmosphere, or may be nitrogen, argon, or a mixed gas thereof. If a thick oxide film or the like is formed on the silicon single crystal substrate, the film can be removed by hydrofluoric acid treatment or the like before heat treatment.

In this manner, by subjecting the prepared silicon single crystal substrate to heat treatment at 250° C. or higher in an atmosphere other than hydrogen, it is possible to diffuse and remove hydrogen previously contained in the prepared silicon single crystal substrate. As a result, the concentration of hydrogen introduced only in the subsequent sub-step _SC can be easily and highly sensitively evaluated without being influenced by hydrogen previously contained in the prepared silicon single crystal substrate.

Next, a substep _SC is performed in which hydrogen is introduced into the silicon single crystal substrate that has been subjected to the heat treatment.

The substep _SC in which hydrogen is introduced is a substep to be evaluated in the subsequent step of evaluating the hydrogen concentration.

The substep _SC in which hydrogen is introduced is not particularly limited, but may include one or more of a cleaning process, a chemical etching process, a plasma etching process, and a sputtering process.

When these steps are performed on a silicon single crystal substrate, hydrogen can be introduced into the silicon single crystal substrate, so the concentration of hydrogen that can be introduced in these steps can be evaluated with high sensitivity.

In the example shown in FIG. 2, step S1 of preparing a target silicon single crystal substrate includes the above substeps S _A to S _C to prepare a target silicon single crystal substrate.

In this way, if you want to evaluate the concentration of hydrogen introduced in a specific step in which hydrogen is introduced, perform the substeps S _A to S _C described above to evaluate the Preferably, a single crystal substrate is prepared.

In the example shown in FIG. 2, after heat treatment is applied to the silicon single crystal substrate in substep _SB for removing hydrogen, and before performing the process to be evaluated in substep _SC for introducing hydrogen, It is preferable to avoid performing processes such as cleaning on the silicon single crystal substrate. This is to avoid hydrogen being introduced into the silicon single crystal substrate by steps other than the substep _{SC in which hydrogen is introduced after the substep SB in} which hydrogen is removed.

Alternatively, even if a process in which a specific hydrogen is introduced is to be evaluated and the concentration of hydrogen introduced in that process is to be evaluated, step S1 of preparing the target silicon single crystal substrate may be performed by removing the hydrogen. The sub-step _SB may not be included.

Note that the method for evaluating the hydrogen concentration in a silicon single crystal substrate of the present invention is applicable not only to the aspect in which the individual steps in which hydrogen is introduced as described above are subject to evaluation, but also to the method in which the hydrogen concentration in the silicon single crystal substrate of the product is evaluated. It also includes aspects of evaluating. Therefore, step S1 of preparing the target silicon single crystal substrate does not need to include the substep _SB of removing hydrogen and the substep _SC of introducing hydrogen.

[Step S2 of evaluating the hydrogen concentration in the target silicon single crystal substrate]
Next, step S2 is performed to evaluate the hydrogen concentration in the target silicon single crystal substrate prepared in step S1 (second step).

In the following, when the evaluation target is a process in which a specific hydrogen is introduced, that is, as shown in FIG. 2, substep S _A of preparing a silicon single crystal substrate, substep S _B of removing hydrogen, and hydrogen Step S2 for evaluating the hydrogen concentration when a target silicon single crystal substrate is prepared in step S1 including the introduced substep _SC will be described.

As explained earlier, in this example, the step of introducing hydrogen to be evaluated, that is, the substep _SC in which hydrogen is introduced, is performed on the silicon single crystal substrate that has been heat-treated in substep _SB . give At this time, hydrogen is introduced from the surface of the silicon single crystal substrate, and the introduced hydrogen inactivates dopants previously included in the silicon single crystal substrate or generates new donors. As a result, the carrier concentration changes in the region of the silicon single crystal substrate into which hydrogen is introduced.

In step S2 for evaluating the hydrogen concentration in this example, the distribution in the depth direction of the amount of change in carrier concentration is measured in the silicon single crystal substrate after substep _SC in which hydrogen is introduced.

The method for measuring the amount of change in carrier concentration is not particularly limited, and for example, a spreading resistance measurement method (SR method) can be used.

For example, in the SR method, two probes are brought into contact with the polished surface of a sample diagonally polished, and the spreading resistance between the probes is measured. ), calculate the resistivity from the measured spreading resistance using a calibration curve, and further calculate the carrier concentration from the resistivity calculated above based on the existing relationship between resistivity and carrier concentration. , obtain the distribution of carrier concentration in the depth direction.

Next, from the carrier concentration (Nc(x)) at each depth x and the carrier concentration (Nc(Bulk)) in the matrix (deep region where the carrier concentration is approximately constant), we calculate the change in carrier concentration at each depth x. Find the quantity (ΔNc(x)).

Here, if the conductivity type at each depth after the substep _SC in which hydrogen is introduced is the same as the conductivity type before the substep _SC in which hydrogen is introduced, the carrier concentration (Nc The absolute value of the value obtained by subtracting the carrier concentration (Nc (Bulk)) in the matrix from (x)) is calculated, and the amount of change in carrier concentration at each depth ) |).

In addition, if the conductivity type at each depth after substep _SC in which hydrogen is introduced is different from the conductivity type before substep _SC in which hydrogen is introduced, the carrier concentration (Nc( x)) and the carrier concentration (Nc (Bulk)) in the matrix is calculated, and the amount of change in carrier concentration at each depth x (ΔNc (x) = Nc (x) + Nc (Bulk)) is determined.

If the temperature applied to the silicon single crystal substrate in the substep S _C in which hydrogen is introduced is high, the introduced hydrogen may diffuse into a deep region, and the carrier concentration may change throughout the depth direction of the silicon single crystal substrate. . In such a case, the amount of change in carrier concentration is determined by using the carrier concentration in the silicon single crystal substrate before substep _SC in which hydrogen is introduced as the carrier concentration in the matrix.

Hydrogen introduced into the silicon single crystal substrate inactivates dopants that may be previously included in the silicon single crystal substrate. Further, hydrogen itself may act as a donor, or may react with a light element contained in advance to generate a donor. As a result, when hydrogen is introduced into the silicon single crystal substrate, the carrier concentration in the region where hydrogen is introduced changes. It is believed that one hydrogen is involved in the deactivation of one dopant, and one hydrogen is involved in the generation of one donor. On the other hand, there are cases where the introduced hydrogen reacts with a light element previously included to form an electrically inactive composite.

For this reason, the amount of change in carrier concentration measured after the substep _SC in which hydrogen is introduced is based on the fact that the shallow electrically active levels of the hydrogen introduced into the silicon single crystal substrate are inactivated. It is related to the concentration of hydrogen that has formed a shallow level and the concentration of hydrogen that has generated a shallow level.

Therefore, for example, in step S2 for evaluating the hydrogen concentration, the distribution of the measured change in carrier concentration in the depth direction can be directly evaluated as the distribution of hydrogen concentration in the target silicon single crystal substrate.

When the conductivity type of the silicon single crystal substrate into which hydrogen is introduced in substep _SC is P type, when the dopant previously contained in the silicon single crystal substrate is inactivated, the P type carrier concentration decreases, When a new donor is generated, as the donor concentration increases, the P-type carrier concentration decreases due to carrier compensation, and then the N-type carrier concentration increases. From this, the amount of change in carrier concentration (ΔNc(x)) determined by the above equation is the concentration of hydrogen that inactivated the electrically active shallow level and the concentration of hydrogen that generated the shallow level. is the sum of Here, the lower the dopant concentration (carrier concentration in the matrix) pre-contained in the silicon single crystal substrate, the smaller the amount of change in carrier concentration can be detected, so the hydrogen concentration can be evaluated with higher sensitivity. .

On the other hand, if the conductivity type of the silicon single crystal substrate into which hydrogen is introduced in substep _SC is N type, when the pre-contained dopants are inactivated, the N type carrier concentration decreases and new donors are generated. When this happens, the N-type carrier concentration increases. From this, the amount of change in carrier concentration (ΔNc(x)) determined by the above equation is the concentration of hydrogen that inactivated the electrically active shallow level and the concentration of hydrogen that generated the shallow level. The difference is Therefore, when the conductivity type of the silicon single crystal substrate is N type, the concentration of introduced hydrogen is evaluated to be lower than when it is P type. However, the hydrogen concentration is important for the electrical characteristics of semiconductor devices. This difference between P-type and N-type can be ignored in terms of evaluating the amount of change due to the introduction of . Here, the lower the dopant concentration (carrier concentration in the matrix) pre-contained in the silicon single crystal substrate, the smaller the effect of decrease in carrier concentration due to dopant inactivation, and the lower the concentration of dopants that are pre-contained in the silicon single crystal substrate, the lower the effect of decrease in carrier concentration due to dopant inactivation, and the lower the Since a small amount of change in carrier concentration can be detected, hydrogen concentration can be evaluated with higher sensitivity.

As explained above, the lower the dopant concentration (matrix carrier concentration) contained in advance in the target silicon single crystal substrate, the more sensitive the hydrogen concentration can be evaluated. For example, it is preferable to prepare a silicon single crystal substrate with a dopant concentration of 1×10 ¹⁴ atoms/cm ³ or less as the target silicon single crystal substrate, and a silicon single crystal substrate with a dopant concentration of 7×10 ¹² atoms/cm ³ or less. More preferably, a crystal substrate is prepared.

In this way, changes in carrier concentration are observed for the target silicon single crystal substrate prepared by performing substep S _C in which hydrogen is introduced into the silicon single crystal substrate heat treated in sub step S _B. By measuring the distribution of the amount in the depth direction, the concentration of hydrogen introduced in the process to be evaluated can be easily evaluated with high sensitivity.

Furthermore, if the conductivity type of the silicon single crystal substrate prepared in sub-step S _A is P type, it is possible to evaluate with high sensitivity the change in carrier concentration due to hydrogen introduced in the manufacturing process, and as a result, The hydrogen concentration introduced can be evaluated with high sensitivity.

As mentioned earlier, the present invention includes not only an aspect in which the individual steps in which hydrogen is introduced as described above are subject to evaluation, but also an aspect in which the hydrogen concentration in a silicon single crystal substrate of a product is evaluated. . In the aspect of evaluating the hydrogen concentration in the silicon single crystal substrate of the product, the distribution of the change in carrier concentration in the depth direction is measured for the silicon single crystal substrate of the product using the same procedure as explained above. By doing so, the hydrogen concentration in the silicon single crystal substrate of the product can be easily evaluated with high sensitivity.

According to the evaluation method of the present invention, even if the hydrogen concentration of the target silicon single crystal substrate is so low that it cannot be measured by SIMS, it can be easily and easily measured. It becomes possible to evaluate with high sensitivity.

Hereinafter, the present invention will be specifically explained using Examples and Comparative Examples, but the present invention is not limited thereto.

In the Examples and Comparative Examples shown below, the substep in which hydrogen is introduced (corresponding to substep _SC in FIG. 2) is generally used in the manufacturing process of silicon single crystal substrates and the manufacturing process of semiconductor devices. After performing an SC-1 wash (NH ₄ OH/H ₂ O ₂ /H ₂ O), an SC-2 wash (HCl/H ₂ O ₂ /H ₂ O) was performed. The reason why the above-mentioned cleaning process was selected as the sub-step _SC in which hydrogen is introduced is that the concentration of hydrogen introduced in the cleaning process is considered to be lower than the concentration of hydrogen introduced in other etching processes and sputtering processes. This is because the effects of the present invention can be more effectively demonstrated compared to the conventional method of measuring hydrogen concentration using SIMS, which has low sensitivity to hydrogen concentration.

(Example 1)
In Example 1, the concentration of hydrogen introduced into a silicon single crystal substrate was evaluated using an example of the method for evaluating hydrogen concentration in a silicon single crystal substrate according to the present invention according to the following procedure.

First, a substep of preparing a silicon single crystal substrate was performed.
As the silicon single crystal substrate, a CZ silicon single crystal substrate produced from a silicon single crystal grown by the CZ method was prepared. The prepared silicon single crystal substrate has a diameter of 200 mm, a crystal plane orientation of (100), a conductivity type of P type (boron doped), a boron concentration of approximately 1×10 ¹⁴ atoms/cm ³ , and an oxygen concentration of approximately 12 ppma (JEIDA). Met.

Next, a substep of introducing hydrogen was performed on the prepared silicon single crystal substrate.

Here, specifically, as a step in which hydrogen is introduced, SC-1 cleaning (NH ₄ OH/H ₂ O ₂ /H ₂ O) is performed at approximately 75°C for approximately 8 minutes, followed by SC-2 cleaning. (HCl/H ₂ O ₂ /H ₂ O) at about 80° C. for about 2 minutes.

Step S1 (FIG. 1) of preparing a target silicon single crystal substrate was performed by performing both the substep of preparing the silicon single crystal substrate and the substep of introducing hydrogen.

Next, with respect to the silicon single crystal substrate after performing the substep of introducing hydrogen, the distribution of the change in carrier concentration in the depth direction is measured using the following procedure, and the hydrogen concentration in the silicon single crystal substrate is measured. Step S2 (FIG. 1) was performed to evaluate.

First, the surface of the silicon single crystal substrate was subjected to angle polishing after the substep of introducing hydrogen was performed. Regarding the angle-polished silicon single crystal substrate, the spreading resistance from the surface to a depth of approximately 30 μm and the distribution of conductivity type in the depth direction were measured using the SR measurement method.

Next, by determining the resistivity from the spreading resistance at each measured depth, the distribution of resistivity in the depth direction shown in FIG. 3 was obtained. In the results shown in FIG. 3, the conductivity type was P type at any depth.

Next, based on the known relationship between resistivity and carrier concentration in the case of P-type, the carrier concentration is determined from the resistivity calculated above to obtain the carrier concentration distribution in the depth direction shown in FIG. Ta. The results in FIG. 4 show that the carrier concentration decreases in a region from the surface to a depth of approximately 6 μm.

Next, in the results shown in FIG. 4, the average value (1.1×10 ¹⁴ /cm ³ ) of the carrier concentration at a depth of about 25 to 30 μm is taken as the carrier concentration in the matrix (Nc (Bulk)), and each measured depth is The absolute value of the value obtained by subtracting the carrier concentration in the matrix from the carrier concentration in the matrix (Nc(x)) was determined. These absolute values are plotted as the amount of change in carrier concentration at each depth x (ΔNc(x)=|Nc(x)−Nc(Bulk)|), and the amount of change in carrier concentration at the depth shown in FIG. The distribution in the horizontal direction was obtained.

From the results shown in Figure 5, the amount of change in carrier concentration is approximately 1×10 ¹⁴ /cm ³ near the surface, decreases as the depth increases, and reaches the detection limit (approximately 5×10 ¹² /cm 3 ) at a depth of approximately 6 μm. ³ ). From this, in this example, the sum of the concentration of hydrogen that inactivated the electrically active shallow level and the concentration of hydrogen that generated the shallow level is approximately 1×10 ¹⁴ atoms/in the vicinity of the surface. cm ³ , the sum of these concentrations decreased as the depth increased, and it was found that the distribution in the depth direction was about 5×10 ¹² atoms/cm ³ at a depth of about 6 μm.

(Example 2)
In Example 2, the concentration of hydrogen introduced into a silicon single crystal substrate was evaluated using an example of the method for evaluating the hydrogen concentration in a silicon single crystal substrate according to the present invention according to the following procedure.

First, a substep of preparing a silicon single crystal substrate was performed.
As a silicon single crystal substrate, an FZ silicon single crystal substrate produced from a silicon single crystal grown by the FZ method was prepared. The prepared silicon single crystal substrate has a diameter of 200 mm, a crystal plane orientation of (100), a conductivity type of P type (boron doped), a boron concentration of approximately 5×10 ¹² atoms/cm ³ , and an oxygen concentration of approximately 0.2 ppma ( JEIDA). That is, in Example 2, a silicon single crystal substrate having a lower dopant concentration than that in Example 1 was used.

Next, a substep of introducing hydrogen was performed on the prepared silicon single crystal substrate under the same conditions as in Example 1.

Step S1 (FIG. 1) of preparing a target silicon single crystal substrate was performed by performing both the substep of preparing the silicon single crystal substrate and the substep of introducing hydrogen.

Next, with respect to the silicon single crystal substrate after the sub-step in which hydrogen is introduced, the depth distribution of the carrier concentration change is measured using the following procedure, and the hydrogen concentration in the silicon single crystal substrate is determined. Evaluation step S2 (FIG. 1) was performed.

First, the surface of the silicon single crystal substrate was subjected to angle polishing after the substep of introducing hydrogen was performed. Regarding the angle-polished silicon single crystal substrate, the spreading resistance and conductivity type distribution in the depth direction were measured from the surface to a depth of approximately 30 μm using the SR measurement method.

Next, by determining the resistivity from the spreading resistance at each measured depth, the distribution of resistivity in the depth direction shown in FIG. 6 was obtained. In the results shown in FIG. 6, the conductivity type at each depth is N type in the region from 0 to about 8 μm deep (marked △ in FIG. 6), and P type in the region deeper than about 8 μm (marked ○ in FIG. 6). Met.

Next, the carrier concentration in the depth direction shown in FIG. We obtained the distribution of From the results in Figure 7, the P-type carrier (hole) concentration (marked with a circle in Figure 7) decreases from a depth of approximately 20 μm to approximately 8 μm, and the N-type carrier (electron) concentration (marked with a circle in Figure 7) decreases from a depth of approximately 8 μm to the surface. It can be seen that the number (△ mark in 7) is increasing.

Next, in the results of FIG. 7, the average value (4.5×10 ¹² /cm ³ ) of the carrier concentration at a depth of about 25 to 30 μm is taken as the carrier concentration in the matrix (Nc (Bulk)), and the carrier concentration at a depth of about 0 to about In the 8 μm N-type region, the sum of the carrier concentration (Nc(x)) at each measured depth x and the carrier concentration in the matrix (ΔNc(x) = Nc(x) + Nc(Bulk)) is I asked for it. In addition, in the P-type region deeper than about 8 μm in depth, the value obtained by subtracting the carrier concentration in the matrix from the carrier concentration (Nc(x)) at each measured depth x (ΔNc(x) = |Nc(x) - The absolute value of Nc(Bulk) |) was determined. The values obtained as described above were plotted as the amount of change in carrier concentration at each depth x, and the distribution of the amount of change in carrier concentration in the depth direction shown in FIG. 8 was obtained.

The circled region in FIG. 8 is a region of high resistance near the PN junction, and the amount of change in carrier concentration is discontinuous because the measurement accuracy of resistivity is low.

From the results in FIG. 8, the amount of change in carrier concentration is approximately 2×10 ¹³ /cm ³ near the surface, decreases as the depth increases, and reaches the lower detection limit (approximately 1×10 ¹¹ /cm 3 ) at a depth of approximately 20 μm. ³ ). Therefore, in this example, the sum of the concentration of hydrogen that inactivated the electrically active shallow level and the concentration of hydrogen that generated the shallow level is approximately 2×10 ¹³ atoms/in the vicinity of the surface. cm ³ , the sum of these concentrations decreased as the depth increased, and it was found that the distribution in the depth direction was about 1×10 ¹¹ atoms/cm ³ at a depth of about 20 μm.

Furthermore, from a comparison between FIG. 8 of this Example 2 and FIG. 5 of Example 1, it is found that in Example 2, the dopant concentration contained in advance in the silicon single crystal substrate is lower, and hydrogen is introduced in the sub-step where hydrogen is introduced. It can be seen that the hydrogen concentration can be evaluated with higher sensitivity.

(Example 3)
In Example 3, the concentration of hydrogen introduced into a silicon single crystal substrate was evaluated using an example of the method for evaluating the hydrogen concentration in a silicon single crystal substrate of the present invention as shown in FIG.

First, a silicon single-crystal substrate was prepared in step S1 of preparing a silicon single-crystal substrate, which included a sub-step _SB in which the silicon single-crystal substrate was subjected to heat treatment at 250° C. or higher in an atmosphere other than hydrogen.

In the sub-step S _A of preparing a silicon single crystal substrate, a CZ silicon single crystal substrate produced from a silicon single crystal grown by the CZ method was prepared as the silicon single crystal substrate. The prepared silicon single crystal substrate has a diameter of 200 mm, a crystal plane orientation of (100), a conductivity type of P type (boron doped), a boron concentration of approximately 5×10 ¹² atoms/cm ³ , and an oxygen concentration of approximately 5 ppma (JEIDA). Met.

Subsequently, a sub-step _SB was performed in which the prepared silicon single crystal substrate was subjected to heat treatment to remove hydrogen contained in the prepared silicon single crystal substrate. The heat treatment temperature was 250°C, the time was 10 minutes, and the atmosphere was air.

Next, the heat-treated silicon single crystal substrate was subjected to sub-step _SC in which hydrogen was introduced under the same conditions as in Example 1.

Next, with respect to the silicon single crystal substrate after performing the sub-step _SC in which hydrogen is introduced, the distribution of carrier concentration change in the depth direction is measured using the following procedure. Step S2 was performed to evaluate the hydrogen concentration.

First, the surface of the silicon single crystal substrate was subjected to angle polishing after the sub-step _SC in which hydrogen was introduced. Regarding the angle-polished silicon single crystal substrate, the spreading resistance and conductivity type distribution in the depth direction from the surface to a depth of approximately 30 μm were measured using the SR measurement method.

Next, by determining the resistivity from the spreading resistance at each measured depth, the distribution of resistivity in the depth direction shown in FIG. 9 was obtained. In the results shown in FIG. 9, the conductivity type was P type at any depth.

Next, based on the known relationship between resistivity and carrier concentration in the case of P type, the carrier concentration is determined from the resistivity calculated above to obtain the carrier concentration distribution in the depth direction shown in FIG. Ta. The results in FIG. 10 show that the carrier concentration decreases in a region from the surface to a depth of about 20 μm.

Next, in the results shown in FIG. 10, the average value (4.8×10 ¹² /cm ³ ) of the carrier concentration at a depth of approximately 25 to 30 μm is taken as the carrier concentration in the matrix (Nc (Bulk)), and each measured depth is The absolute value of the value obtained by subtracting the carrier concentration in the matrix from the carrier concentration in the matrix (Nc(x)) was determined. The absolute value of this is plotted as the amount of change in carrier concentration at each depth x (ΔNc(x)=|Nc(x)−Nc(Bulk)|), and the amount of change in carrier concentration shown in FIG. The distribution in the horizontal direction was obtained.

From the results shown in Figure 11, the amount of change in carrier concentration is about 2 x 10 ¹² /cm ³ near the surface, increases from near the surface to a depth of about 6 μm, and then decreases as the depth increases. It was found that the lower limit of detection (about 1×10 ¹¹ /cm ³ ) was reached at about 20 μm. From this, in this example, the sum of the concentration of hydrogen that inactivated the electrically active shallow level and the concentration of hydrogen that generated the shallow level was approximately 2×10 ¹² atoms/ cm ³ , increases from near the surface to a depth of approximately 6 μm, and then decreases as the depth increases, resulting in a distribution in the depth direction of approximately 1 × 10 ¹¹ atoms/cm ³ at a depth of approximately 20 μm. I found out that there is.

(Example 4)
In Example 4, the concentration of hydrogen introduced into a silicon single crystal substrate was evaluated using an example of the method for evaluating the hydrogen concentration in a silicon single crystal substrate of the present invention according to the following procedure.

First, a substep of preparing a silicon single crystal substrate was performed.
A CZ silicon single crystal substrate manufactured from a silicon single crystal grown by the CZ method was prepared as a silicon single crystal substrate. The prepared silicon single crystal substrate has a diameter of 200 mm, a crystal plane orientation of (100), a conductivity type of N type (phosphorous doped), a phosphorus concentration of approximately 7×10 ¹² atoms/cm ³ , and an oxygen concentration of approximately 3 ppma (JEIDA). Met.

Next, a substep of introducing hydrogen was performed on the prepared silicon single crystal substrate under the same conditions as in Example 1.

Step S1 (FIG. 1) of preparing a target silicon single crystal substrate was performed by performing both the substep of preparing the silicon single crystal substrate and the substep of introducing hydrogen.

Next, with respect to the silicon single crystal substrate after the sub-step in which hydrogen is introduced, the depth distribution of the carrier concentration change is measured using the following procedure, and the hydrogen concentration in the silicon single crystal substrate is determined. Evaluation step S2 (FIG. 1) was performed.

First, the surface of the silicon single crystal substrate was subjected to angle polishing after the substep of introducing hydrogen was performed. Regarding the angle-polished silicon single crystal substrate, the spreading resistance and conductivity type depth distribution were measured from the surface to a depth of approximately 30 μm using the SR measurement method.

Next, by determining the resistivity from the spreading resistance at each measured depth, the distribution of resistivity in the depth direction shown in FIG. 12 was obtained. In the results shown in FIG. 12, the conductivity type was N type at any depth.

Next, based on the known relationship between resistivity and carrier concentration in the case of N type, the carrier concentration is determined from the resistivity calculated above to obtain the carrier concentration distribution in the depth direction shown in FIG. Ta. The results in FIG. 13 show that the carrier concentration increases in the region from the surface to a depth of approximately 25 μm.

Next, in the results shown in FIG. 13, the average value (6.9×10 ¹² /cm ³ ) of the carrier concentration at a depth of about 25 to 30 μm is taken as the carrier concentration in the matrix (Nc (Bulk)), and each measured depth is The absolute value of the value obtained by subtracting the carrier concentration in the matrix from the carrier concentration in the matrix (Nc(x)) was determined. The obtained absolute value is plotted as the amount of change in carrier concentration at each depth x (ΔNc(x)=|Nc(x)−Nc(Bulk)|), and the depth of the amount of change in carrier concentration shown in FIG. The distribution in the direction was obtained.

From the results in FIG. 14, the amount of change in carrier concentration is approximately 5×10 ¹² /cm ³ near the surface, decreases as the depth increases, and reaches the detection limit (approximately 1×10 ¹¹ /cm ) at a depth of approximately 25 μm. ³ ). From this, in this example, the difference between the concentration of hydrogen that inactivated the electrically active shallow level and the concentration of hydrogen that generated the shallow level was approximately 5×10 ¹² atoms/cm near the surface. ³ , it was found that this difference in concentration decreases as the depth increases, resulting in a distribution in the depth direction of about 1×10 ¹¹ atoms/cm ³ at a depth of about 25 μm.

As shown in the above examples, the method for evaluating the hydrogen concentration in a silicon single crystal substrate of the present invention quantitatively evaluates the hydrogen concentration introduced in, for example, a cleaning process used in the manufacture of silicon single crystal substrates and semiconductor devices. In addition, it is possible to quantitatively evaluate changes in the concentration of hydrogen introduced when changing process conditions, so the concentration of hydrogen introduced in each process can be evaluated in order to prevent or improve the electrical characteristics of semiconductor devices. This is effective when controlling

In addition, as shown in the above examples, the detection lower limit of hydrogen concentration in the method for evaluating hydrogen concentration in a silicon single crystal substrate of the present invention is determined in advance by the detection limit of the hydrogen concentration in the silicon single crystal substrate prepared in the above example. The dopant concentration is at least 1/20 or less of the dopant concentration. Therefore, if the dopant concentration pre-contained in the silicon single crystal substrate is at least 2×10 ¹⁷ atoms/cm ³ or less, the detection limit of the conventional technology is higher than that of SIMS, which has a detection limit of about 1×10 ¹⁶ atoms/cm ^3. Hydrogen concentration can be evaluated with sensitivity.

In addition, when the concentration of introduced hydrogen is low as in the cleaning step shown in the example, it is preferable that the dopant concentration of the silicon single crystal substrate is 1×10 ¹⁴ atoms/cm ³ or less; More preferably, it is 7×10 ¹² atoms/cm ³ or less.

(Comparative example)
In the comparative example, the hydrogen concentration was evaluated by SIMS, which is a conventional technique, without using the method for evaluating the hydrogen concentration in a silicon single crystal substrate of the present invention as shown in FIG.

First, an FZ silicon single crystal substrate made from a silicon single crystal grown by the FZ method was prepared. The diameter of the prepared FZ silicon single crystal substrate was 200 mm, the crystal plane orientation was (100), the conductivity type was P type (boron doped), the boron concentration was approximately 5×10 ¹² atoms/cm ³ , and the oxygen concentration was approximately 0.2 ppma ( JEIDA). That is, a silicon single crystal substrate similar to that prepared in Example 2 was prepared.

Next, the prepared silicon single crystal substrate was subjected to a sub-step of introducing hydrogen under the same conditions as in Example 1.

Next, the distribution of hydrogen concentration in the depth direction from the surface to a depth of about 30 μm was measured by SIMS for the silicon single crystal substrate subjected to the substep of introducing hydrogen. The results are shown in FIG.

From the results in Figure 15, the hydrogen concentration is at the lower limit of detection (approximately 1×10 ¹⁶ atoms/cm ³ ) at any depth, making it possible to evaluate the concentration of hydrogen introduced in the substep where hydrogen is introduced. There wasn't.

As detailed above, in the comparative example, the method for evaluating the hydrogen concentration in a silicon single crystal substrate of the present invention was not used, and the lower limit of detection was approximately 1×10 ¹⁶ atoms/cm ³ , so hydrogen was not introduced. It was not possible to evaluate the concentration of hydrogen introduced in the substep.

On the other hand, in Examples 1 to 4 using the method for evaluating the hydrogen concentration in a silicon single crystal substrate of the present invention, it is possible to easily and highly sensitively evaluate the concentration of hydrogen introduced in the substep in which hydrogen is introduced. did it.

Note that the present invention is not limited to the above embodiments. The above-mentioned embodiments are illustrative, and any embodiment that has substantially the same configuration as the technical idea stated in the claims of the present invention and has similar effects is the present invention. covered within the technical scope of.

Claims (8)

A method for evaluating hydrogen concentration in a silicon single crystal substrate, the method comprising:
a step of preparing a target silicon single crystal substrate;
evaluating the hydrogen concentration in the target silicon single crystal substrate by measuring the distribution of carrier concentration change in the depth direction with respect to the target silicon single crystal substrate ,
A method for evaluating hydrogen concentration in a silicon single crystal substrate , wherein the amount of change in the carrier concentration is determined from the carrier concentration at each depth and the carrier concentration in the matrix . Claim 1, wherein in the step of evaluating the hydrogen concentration, a distribution in the depth direction of the amount of change in the measured carrier concentration is evaluated as a distribution of the hydrogen concentration in the target silicon single crystal substrate. A method for evaluating hydrogen concentration in a silicon single crystal substrate described in . The silicon single crystal substrate according to claim 1 or 2, wherein a silicon single crystal substrate having a dopant concentration of 1×10 ¹⁴ atoms/cm ^{3 or} less is prepared as the target silicon single crystal substrate. Method for evaluating hydrogen concentration. The hydrogen concentration in the silicon single crystal substrate according to claim 3, wherein a silicon single crystal substrate having a dopant concentration of 7×10 ¹² atoms/cm ³ or less is prepared as the target silicon single crystal substrate. Evaluation method. The step of preparing the target silicon single crystal substrate includes:
a substep of preparing a silicon single crystal substrate;
a substep of removing hydrogen contained in the prepared silicon single crystal substrate by subjecting the prepared silicon single crystal substrate to heat treatment at 250° C. or higher in an atmosphere other than hydrogen;
a substep of introducing hydrogen into the heat-treated silicon single crystal substrate,
The method for evaluating hydrogen concentration in a silicon single crystal substrate according to any one of claims 1 to 4, characterized in that the target silicon single crystal substrate is prepared. In a silicon single crystal substrate according to claim 5, the sub-step of introducing hydrogen includes one or more of a cleaning process, a chemical etching process, a plasma etching process, and a sputtering process. Method for evaluating hydrogen concentration. 7. The method for evaluating hydrogen concentration in a silicon single crystal substrate according to claim 5 or 6, wherein the silicon single crystal substrate to be prepared has a conductivity type of P type. 8. The silicon single crystal according to claim 1, wherein in the step of evaluating the hydrogen concentration, a spreading resistance measurement method is used to measure the distribution of the amount of change in the carrier concentration in the depth direction. Method for evaluating hydrogen concentration in a substrate.

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