JP2021092485A - Method for evaluating metal impurities on silicon substrate surface - Google Patents

Abstract

To provide a method for performing TXRF analysis with high sensitivity while keeping position information of metal impurities on a silicon substrate surface.SOLUTION: A method for evaluating metal impurities on a silicon substrate surface, comprises: bring vapor 3 generated from acid mixture solution 2 into contact with the silicon substrate surface for 15 to 30 minutes to decompose the vapor phase of the silicon substrate surface, wherein the acid mixture solution contains 10.0 to 15.0 mass% of hydrogen fluoride, 19.0 to 23.0 mass% of hydrogen peroxide, and 1.5 to 3.2 mass% of hydrogen chloride; and evaluating metal impurities on the silicon substrate surface after the vapor phase decomposition by the total reflection fluorescent X-ray analysis method.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for analyzing metal impurities on the surface of a silicon substrate, and particularly to total internal reflection fluorescent X-ray analysis.

Wafer cleanliness control is important in the semiconductor device manufacturing process, and WSA (Wafer Surface Analysis) is used as a wafer surface impurity analysis method. In WSA, acid vapor is exposed to the wafer surface, the natural oxide film on the wafer surface is dissolved, and then the wafer surface is scanned with an acid solution to recover impurities on the wafer surface including the natural oxide film and induce the recovered acid solution. It is measured by an inductively coupled plasma mass spectrometer or the like. This method is characterized in that high-sensitivity analysis can be performed by recovering and concentrating impurities on the wafer surface, but has a drawback that the position information of impurities on the wafer surface is lost.

On the other hand, as a method capable of easily analyzing wafer surface impurities, there is a total reflection X-Ray Fluorescence analysis method (hereinafter referred to as "TXRF method"). The TXRF method is a method capable of detecting impurities on the wafer surface with high sensitivity by exciting the wafer surface impurities with X-rays incident under total reflection conditions and detecting the generated fluorescent X-rays. FIG. 10 shows a principle diagram of the TXRF method. The TXRF method is non-destructive and can analyze the in-plane distribution of impurities, which is effective in detecting local contamination. On the other hand, there is also a problem that the detection sensitivity is inferior to that of chemical analysis such as WSA.

Therefore, in recent years, the TXRF method has been made more sensitive by combining the WSA and the TXRF method, drying the acid solution from which impurities have been recovered on the wafer, and performing TXRF analysis on the drying marks. However, there is a drawback that the position information of impurities, which is an advantage of the TXRF method, is lost. Therefore, the wafer surface is gas-phase decomposed and then dried to aggregate the impurities on the wafer surface into particles (FIG. 11), and TXRF analysis is performed in that state to maintain the position information of the impurities in the wafer surface. As it is, a method utilizing the effect of increasing the detection intensity is also performed (Patent Document 1). FIG. 12 shows a flow chart of the gas phase decomposition-TXRF method.

The TXRF method is an analysis method that utilizes the fact that total reflection occurs when X-rays are incident at an extremely shallow angle equal to or less than the critical angle, and can excite only impurities on the wafer surface. Therefore, it is a high-sensitivity analysis method capable of suppressing the influence of scattering of incident X-rays and background rise due to fluorescent X-rays from a substrate. Further, in order to further increase the sensitivity of the TXRF method, in order to increase the sensitivity while maintaining the position information of impurities in the wafer surface, as described in Patent Document 1, the wafer surface is dried after vapor phase decomposition. By doing so, it is effective to agglomerate the wafer surface impurities into particles and increase the scattered X-ray dose from the particles. However, Patent Document 1 defines only HF as the gas in the gas phase decomposition, and does not show the relationship between the gas phase decomposition time and the X-ray intensity of TXRF before and after the gas phase decomposition.

Japanese Patent No. 3690484

As described above, the vapor phase decomposition conditions for changing the morphology of wafer surface impurities into particles are generally hydrofluoric acid (HF aqueous solution), but up to the optimum values for concentration and vapor phase decomposition time. Was not mentioned. For this reason, it has been found that proper gas phase decomposition is not performed, and the morphological change into particles becomes insufficient, and as a result, it becomes a problem that the variation increases. In particular, the tendency is remarkable for elements such as Cu, which have a lower ionization tendency than silicon.

The present invention has been made to solve the above problems, and by providing appropriate gas phase decomposition conditions for changing the morphology into particles by gas phase decomposition, the positions of metal impurities on the surface of the silicon substrate are provided. It is an object of the present invention to provide a method for performing TXRF analysis with high sensitivity while preserving information.

The present invention has been made to achieve the above object, and is a method for evaluating metal impurities on the surface of a silicon substrate, in which 10.0 to 15.0% by mass of hydrogen peroxide and 19.0 to 19.0 to 19.0 to 15.0% by mass of hydrogen peroxide are used. Steam generated from an acid mixed solution containing 23.0% by mass of hydrogen peroxide and 1.5 to 3.2% by mass of hydrogen chloride is brought into contact with the surface of the silicon substrate for 15 to 30 minutes to bring the surface of the silicon substrate into contact with the surface of the silicon substrate. Provided is a method for evaluating metal impurities on the surface of a silicon substrate, which performs gas phase decomposition and evaluates the metal impurities on the surface of the silicon substrate after the vapor phase decomposition by a total reflection fluorescent X-ray analysis method.

According to such a method for evaluating metal impurities on the surface of a silicon substrate, highly sensitive TXRF analysis can be performed while maintaining position accuracy.

At this time, in the vapor phase decomposition, the acid mixed solution is injected into a container having an opening at the upper part, the silicon substrate is installed so as to cover the opening, and the surface of the silicon substrate is evaluated for metal impurities. A closed space is formed between the container and the acid mixed solution, and the vapor generated from the acid mixed solution is used to vapor-phase decompose the surface of the silicon substrate facing the closed space. Metal impurities on the surface of the silicon substrate. It can be an evaluation method.

This makes it possible to perform highly sensitive TXRF analysis with higher position accuracy more easily.

As described above, according to the method for evaluating metal impurities on the surface of a silicon substrate of the present invention, it is possible to perform TXRF analysis with high position accuracy and high sensitivity.

An example of the gas phase decomposition treatment in the metal impurity evaluation method according to the present invention is shown. The relationship between the gas phase decomposition time and the X-ray intensity increase ratio (Ratio) of Cr, Fe, Ni, and Cu before and after the gas phase decomposition is shown. The relationship between the gas phase decomposition time and the lower limit of TXRF detection is shown. The X-ray intensity increase ratios (Ratio) of Cr, Fe, Ni, and Cu before and after gas phase decomposition in Comparative Example 1 and Comparative Example 2 are shown. The lower limit value of TXRF detection before gas phase decomposition in Comparative Example 1 and Comparative Example 2 is shown. The lower limit value of TXRF detection after gas phase decomposition in Comparative Example 1 and Comparative Example 2 is shown. The X-ray intensity increase ratio (Ratio) before and after the gas phase decomposition in Comparative Examples 1 to 9 and Examples 1 to 3 is shown. The lower limit of detection of each element to be analyzed before gas phase decomposition in Comparative Examples 1 to 9 and Examples 1 to 3 is shown. The lower limit of detection of each element to be analyzed after gas phase decomposition in Comparative Examples 1 to 9 and Examples 1 to 3 is shown. The principle diagram of the TXRF method is shown. The explanatory diagram of the morphological change into particles in the process of vapor phase decomposition-drying is shown. The flow chart of the gas phase decomposition-TXRF method is shown.

Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

As described above, there has been a demand for a method of performing TXRF analysis with high sensitivity while maintaining the position information of metal impurities on the surface of the silicon substrate.

As a result of diligent studies on the above problems, the present inventor changes the morphology of an acid mixed solution containing hydrofluoric acid, hydrogen peroxide solution, and hydrochloric acid into particles suitable for TXRF analysis during gas phase decomposition. Was found to affect. Further, the concentrations of hydrogen fluoride (HF), hydrogen peroxide (H ₂ O ₂ ), and hydrogen chloride (HCl) in the acid mixed solution should be set to a specific concentration and a specific gas phase decomposition time. Therefore, it has been found that TXRF analysis can be performed with higher sensitivity than before while maintaining the position information of metal impurities on the surface of the silicon substrate.

The present inventor is a method for evaluating metal impurities on the surface of a silicon substrate, which comprises 10.0 to 15.0% by mass of hydrogen fluoride, 19.0 to 23.0% by mass of hydrogen peroxide, and 1 .The vapor generated from the acid mixed solution containing 5 to 3.2% by mass of hydrogen peroxide is brought into contact with the surface of the silicon substrate for 15 to 30 minutes to perform gas phase decomposition on the surface of the silicon substrate, and after the vapor phase decomposition. By the metal impurity evaluation method on the surface of the silicon substrate, which evaluates the metal impurities on the surface of the silicon substrate by the total reflection fluorescent X-ray analysis method, the X-ray intensity increase ratio of Cu by TXRF analysis before and after the gas phase decomposition is the chemical solution for the gas phase decomposition. It is higher than the X-ray intensity increase ratio by TXRF analysis when using only hydrofluoric acid (HF 50% by mass) or when using an acid mixed solution of hydrofluoric acid and hydrogen peroxide solution, which is 5 times or more. The present invention has been completed by finding that the detection sensitivity can be improved.

Hereinafter, description will be made with reference to the drawings.

In the metal impurity evaluation method according to the present invention, the surface of the silicon substrate on which TXRF analysis is to be performed is gas-phase decomposed, and then TXRF analysis is performed. At this time, in consideration of the contact efficiency between the steam and the surface of the silicon substrate during the gas phase decomposition, it is preferable to use the gas phase decomposition container 1 having an opening at the top as shown in FIG. The acid mixed solution 2 is injected into the gas phase decomposition container 1 having an opening at the upper part, the silicon substrate W is placed so as to cover the opening, and the surface of the silicon substrate W and the acid mixed solution 2 in the gas phase decomposition container 1 are provided. A closed space is formed between the two, and the surface of the silicon substrate W facing the closed space can be subjected to vapor phase decomposition treatment by the steam 3 generated from the acid mixed solution 2. If the gas phase decomposition process is performed in this way, it is possible to perform a highly sensitive TXRF analysis with higher position accuracy more easily. However, the method of vapor phase decomposition is not limited to this, and 10.0 to 15.0% by mass of hydrogen fluoride (HF) and 19.0 to 23.0% by mass of hydrogen peroxide are applied to the surface of the silicon substrate. (H ₂ O ₂ ) and steam generated from an acid mixed solution containing 1.5 to 3.2% by mass of hydrogen peroxide (HCl) are brought into contact with each other for 15 to 30 minutes to perform gas phase decomposition on the surface of the silicon substrate. Any method can be used as long as it can be done.

Further, the gas phase decomposition container may be heated by a heater or the like at the time of gas phase decomposition, or an infrared lamp or the like may be irradiated from the upper part of the silicon substrate, and the droplets aggregated on the surface of the silicon substrate become large during the gas phase decomposition. It is preferable not to go too far. In the example described below, the gas phase decomposition was carried out at room temperature (23 ° C.) under the condition that the heater or the like was not heated.

The present inventor is not limited to the case where the chemical solution of the steam source in the vapor phase decomposition is only hydrofluoric acid or the acid mixed solution of hydrofluoric acid + hydrochloric acid aqueous solution, but also hydrofluoric acid + excess. In the case of an acid mixed solution of hydrogen oxide water + hydrochloric acid, the change in X-ray intensity during the gas phase decomposition time was investigated. As a result, although details will be described later, the X-ray intensity of Cu after gas phase decomposition is higher than that before gas phase decomposition when only hydrofluoric acid is used or hydrofluoric acid + hydrogen chloride. In the case of an acid mixed solution of water, the increase was about 1.5 times, whereas it was 10.0 to 15.0% by mass of hydrogen fluoride (HF) and 19.0 to 23.0% by mass. It has been found that in the case of an acid mixed solution containing hydrofluoric acid (H ₂ O ₂ ) and 1.5 to 3.2% by mass of hydrogen chloride (HCl), an increase of up to about 7 times is observed. This is because the addition of hydrochloric acid to hydrofluoric acid + hydrogen peroxide solution increases the oxidation-reduction potential of water droplets aggregated on the surface of the silicon substrate and increases the oxidizing power. Therefore, in the case of hydrofluoric acid alone. It is probable that in the case of the acid mixed solution of hydrofluoric acid + hydrogen peroxide solution, Cu that was not ionized was ionized and aggregated in the same manner as other elements during drying. As a result, the incident X-rays slightly invade the inside of the aggregate (particles), and the fluorescent X-rays are emitted from the surface and the inside of the aggregate, so that it is considered that the X-ray detection intensity is increased.

In addition, the X-ray intensity increase ratio in the gas phase decomposition time reached the maximum in about 15 minutes as described later, but tended to decrease after 30 minutes. It is considered that this is because if the aggregates constituting the aggregate nuclei generated at the time of aggregation become too large, the influence of diffused reflection of X-rays on the surface of the aggregates increases, and the yield of X-rays to the detector decreases. ..

In particular, the hydrogen fluoride (HF) concentration is 10.0 to 11.0% by mass, the hydrogen peroxide (H ₂ O ₂ ) concentration is 21.9 to 22.1% by mass, and the hydrogen chloride (HCl) concentration is 2. It is preferable to use a mixed acid solution of 1 to 2.6% by mass. When such a mixed acid solution is used, the ratio of increase in X-ray intensity of Cu by TXRF analysis before and after gas phase decomposition is the case of a chemical solution containing only hydrofluoric acid (HF 50% by mass) or hydrofluoric acid +. In the case of an acid mixed solution of hydrofluoric acid solution, it is larger than the X-ray intensity increase ratio (Ratio) by TXRF analysis before and after gas phase decomposition, and is about 7 times. In addition, the gas phase decomposition time is 15 to 30 minutes, and the maximum effect is exhibited.

In FIG. 2, an acid mixed solution containing 10.7% by mass of hydrogen fluoride (HF) + 22.1% by mass of hydrogen peroxide (H ₂ O ₂ ) + 2.6% by mass of hydrogen chloride (HCl) was used. In the case of vapor phase decomposition, the relationship between the vapor phase decomposition time and the X-ray intensity increase ratio (Ratio) of Cr, Fe, Ni, and Cu before and after the vapor phase decomposition is shown. It was confirmed that the X-ray intensity ratio (Ratio) increases as the gas phase decomposition time increases, but the X-ray intensity increase ratio (Ratio) decreases when the gas phase decomposition time is 30 minutes or more. In other words, it was found that a high X-ray intensity ratio (Ratio) can be obtained if the gas phase decomposition time is 15 to 30 minutes.

Similarly, FIG. 3 shows an acid mixed solution containing 10.7% by mass of hydrogen fluoride (HF) + 22.1% by mass of hydrogen peroxide (H ₂ O ₂ ) + 2.6% by mass of hydrogen chloride (HCl). The relationship between the gas phase decomposition time and the TXRF detection lower limit value when the gas phase decomposition is performed using. It can be seen that the lower limit of detection also shows a low value in the gas phase decomposition time of 15 to 30 minutes, which has the highest X-ray intensity increase ratio. Therefore, by setting the gas phase decomposition time to 15 to 30 minutes, it is possible to perform TXRF analysis with high sensitivity.

As described above, 10.0 to 15.0% by mass of hydrogen fluoride (HF), 19.0 to 23.0% by mass of hydrogen peroxide (H ₂ O ₂ ), and 1.5 to 3.2 by mass. When vapor phase decomposition is performed for 15 to 30 minutes using steam generated from an acid mixed solution containing mass% hydrogen peroxide (HCl), high sensitivity is maintained while maintaining the position information of metal impurities on the surface of the silicon substrate. TXRF analysis can be performed at. On the other hand, under conditions outside the above range, it is difficult to perform TXRF analysis with high sensitivity because the X-ray intensity increase ratio of Cu is particularly low and the lower limit of detection is high.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but this does not limit the present invention.

In the following examples and comparative examples, comparisons were made using forced contaminated wafers. For the forced contamination wafer for this evaluation, a clean p-type silicon PW wafer with a diameter of 200 mm was used, and a 1000 ppm atomic absorption standard solution (Cr, Fe, Ni, Cu) manufactured by Kanto Chemical Co., Ltd. was appropriately diluted and Tama Chemical Co., Ltd. A solution prepared with an ultra-high purity ethanol (AA100) solvent was added dropwise to the center of the wafer in an amount of 20 μL, air-dried, and the content of each element in the added dropwise solution was 0.05 ng, 0.5 ng, 5 ng, and 50 ng. The wafer was prepared.

As the total internal reflection fluorescent X-ray analyzer, TREX630T manufactured by Technos was used. The analysis conditions were 40 kV, 40 mA, the X-ray incident angle was 0.05 degrees, and the measurement time was 300 seconds / point. In this evaluation (contrast between Examples and Comparative Examples), evaluation was performed by total reflection fluorescent X-ray analysis on the surface of the silicon substrate before and after gas phase decomposition.

The gas phase decomposition of the silicon wafer was performed using the gas phase decomposition container 1 shown in FIG. A chemical solution 2 serving as a vapor generation source is injected into the gas phase decomposition container 1, placed on the gas phase decomposition container 1 so that the PW surface, which is the surface of the silicon substrate W for metal impurity evaluation, faces downward, and the chemical solution 2 is used. The vapor phase was decomposed by sealing the steam 3 of the above.

(Comparative Example 1)
When 200 mL of STELLA CHEMIFA EL-grade hydrofluoric acid (50% by mass) is injected into the gas phase decomposition container 1 shown in FIG. 1, the PW surface is the surface of the silicon substrate W for metal impurity evaluation. The vapor phase decomposition was carried out by placing it on the gas phase decomposition container 1 so that the surface was facing downward and sealing the steam 3. The gas phase decomposition time was 15 minutes, and after the gas phase decomposition, natural drying was performed in a clean draft.

(Comparative Example 2)
An acid mixed solution in which Stella Chemifer's EL-grade hydrofluoric acid (50% by mass) and Santoku Kagaku's EL-grade hydrogen peroxide solution (31% by mass) are mixed 1: 1 as a chemical solution to be injected into the gas phase decomposition container. Gas phase decomposition was carried out in the same manner as in Comparative Example 1 except that the above was used.

FIG. 4 shows the X-ray intensity increase ratios (Ratio) of Cr, Fe, Ni, and Cu before and after gas phase decomposition in Comparative Example 1 and Comparative Example 2. This X-ray intensity increase ratio (Ratio) is calculated by (X-ray intensity after gas phase decomposition) / (X-ray intensity before gas phase decomposition), and is compared with the X-ray intensity before gas phase decomposition. It means how much the X-ray intensity of is increased. The X-ray intensities of Cr, Fe, and Ni after the gas phase decomposition of Comparative Example 1 are about 3 times that before the gas phase decomposition, and Cu is 1.4 times. On the other hand, the X-ray intensities of Cr, Fe, and Ni after the gas phase decomposition in Comparative Example 2 are 12 to 13 times higher than those before the gas phase decomposition, but Cu is 1.5 times, and the X-ray intensity of Cu is 1.5 times. There is almost no improvement effect.

Similarly, for Comparative Example 1 and Comparative Example 2, FIG. 5 shows the lower limit of TXRF detection before gas phase decomposition, and FIG. 6 shows the lower limit of TXRF detection after gas phase decomposition. Cr, Fe, and Ni with a large X-ray intensity increase ratio (Ratio) showed a certain effect of lowering the lower limit of detection, but Cu with a small X-ray intensity increase ratio (Ratio) did not show a decrease in the lower limit of detection. It was.

(Comparative Example 3)
An acid mixed solution in which Stella Chemifer's EL-grade hydrofluoric acid (50% by mass) and Santoku Kagaku's EL-grade hydrogen peroxide solution (31% by mass) are mixed at a ratio of 1: 3 as a chemical solution to be injected into the gas phase decomposition container. Gas phase decomposition was carried out in the same manner as in Comparative Examples 1 and 2 except that the above was used.

(Comparative Examples 4 to 9, Examples 1 to 3)
Similar to Comparative Examples 1 to 3, the vapor phase decomposition of the silicon wafer was performed using the vapor phase decomposition container 1 shown in FIG. As the chemical solution 2 to be injected into the gas phase decomposition container 1, Stella Chemifa EL grade hydrofluoric acid (50% by mass), Santoku Chemical EL grade hydrochloric acid solution (31% by mass), and Kanto Chemical EL grade EL grade. A total of 200 mL of an acid mixed solution in which hydrochloric acid (36% by mass) is mixed at the ratio shown in Table 1 is injected, and a gas phase decomposition container is provided so that the PW surface, which is the surface of the silicon substrate W for metal impurity evaluation, faces downward. The gas phase decomposition was carried out by placing on No. 1 _{and sealing the steam 3 containing HF + H 2} O _{2 + HCl.} The gas phase decomposition time was 15 minutes, and after the gas phase decomposition, natural drying was performed in a clean draft.

Table 1 shows the mixing ratios of the chemical solutions used in Comparative Examples 1 to 9 and Examples 1 to 3 (acid mixed solutions other than Comparative Example 1).

First, the X-ray intensity increase ratio (Ratio) before and after gas phase decomposition when various chemical solutions were used was calculated based on the evaluation result by the total reflection fluorescent X-ray analysis method on the surface of the silicon substrate. FIG. 7 shows the X-ray intensity increase ratios (Ratio) for Comparative Examples 1 to 9 and Examples 1 to 3. It can be seen that in all of Comparative Examples 1 to 9 and Examples 1 to 3, the X-ray intensity after the gas phase decomposition is higher than the X-ray intensity before the gas phase decomposition.

On the other hand, as in the examples, the concentration of hydrogen peroxide (HF) is 10.0 to 15.0% by mass, the concentration of hydrogen peroxide (H ₂ O ₂ ) is 19.0 to 23.0% by mass, and hydrogen chloride. The ratio of increase in X-ray intensity of Cu when gas phase decomposition was performed using an acid mixed solution having a concentration of (HCl) of 1.5 to 3.2% by mass is the hydrogen peroxide (HF) of Comparative Example 1. only (50 wt%) and higher than the X-ray intensity increasing ratio in the case of vapor phase decomposition with an acid mixture solution of hydrogen fluoride of Comparative example 2 (HF) and hydrogen peroxide (H 2 _{O 2),} 5 times or more It can be seen that it increases to. In particular, the concentration of hydrogen fluoride (HF) is 10.0 to 11.0% by mass, the concentration of hydrogen peroxide (H ₂ O ₂ ) is 21.9 to 22.1% by mass, and the concentration of hydrogen chloride (HCl). When vapor phase decomposition was performed using an acid mixed solution mixed so as to have a composition of 2.1 to 2.6% by mass (Example 3), the X-ray intensity increase ratio of Cu was about 7 times. It can be seen that it increases.

^{Further, the lower limit of detection (atoms / cm 2} ) of each analysis target element before gas phase decomposition in Examples 1-3 and Comparative Example 1-9 is shown in FIG. 8, and the detection of each analysis target element after gas phase decomposition is shown in FIG. The lower limit (atoms / cm ² ) is shown in FIG. From this result, it can be seen that the larger the X-ray intensity increase ratio (Ratio) before and after the gas phase decomposition, the lower the detection lower limit value. In particular, in Examples 1 to 3, it can be seen that a high X-ray intensity increase ratio and a low detection lower limit value can be obtained. That is, it is considered that the change in background intensity has almost no effect, and the increase in X-ray intensity is simply linked to the improvement of the lower limit of detection.

As described in detail above, 10.0 to 15.0% by mass of hydrogen fluoride (HF), 19.0 to 23.0% by mass of hydrogen chloride (H ₂ O ₂ ), and 1.5 to 15.0% by mass. When gas phase decomposition is performed for 15 to 30 minutes using steam generated from an acid mixed solution containing 3.2% by mass of hydrogen chloride (HCl), the X-ray intensity of Cu by TXRF analysis after gas phase decomposition The increase ratio is significantly higher than when hydrofluoric acid alone (HF 50% by mass) is used as the chemical solution for gas phase decomposition or when a mixed solution of hydrofluoric acid and hydrogen peroxide solution is used, which is 5 times or more. Increased to. In particular, the hydrogen fluoride (HF) concentration is 10.0 to 11.0% by mass, the hydrogen peroxide (H ₂ O ₂ ) concentration is 21.9 to 22.1% by mass, and the hydrogen chloride (HCl) concentration is 2. When gas phase decomposition is performed using a mixed acid solution of 1 to 2.6% by mass, the X-ray intensity increase ratio of Cu by TXRF analysis increases about 7 times, and the lower limit of detection of Cu is about 1/6. Improved to. In this way, it is possible to perform TXRF analysis with high sensitivity while maintaining the position information of metal impurities on the surface of the silicon substrate. On the other hand, under conditions outside the above range, it can be seen that it is difficult to perform TXRF analysis with high sensitivity because the X-ray intensity increase ratio of Cu is particularly low and the detection lower limit value is high.

The present invention is not limited to the above embodiment. The above-described embodiment is an example, and any object having substantially the same configuration as the technical idea described in the claims of the present invention and exhibiting the same effect and effect is the present invention. Is included in the technical scope of.

1 ... Gas phase decomposition container, 2 ... Chemical solution (mixed acid solution), 3 ... Steam, W ... Silicon substrate.

Claims (2)

This is a method for evaluating metal impurities on the surface of a silicon substrate.
It is generated from an acid mixed solution containing 10.0 to 15.0% by mass of hydrogen fluoride, 19.0 to 23.0% by mass of hydrogen peroxide, and 1.5 to 3.2% by mass of hydrogen chloride. The steam is brought into contact with the surface of the silicon substrate for 15 to 30 minutes to perform gas phase decomposition on the surface of the silicon substrate.
A method for evaluating metal impurities on the surface of a silicon substrate, which comprises evaluating the metal impurities on the surface of the silicon substrate after vapor phase decomposition by a total reflection fluorescent X-ray analysis method. In the gas phase decomposition, the acid mixed solution is injected into a container having an opening at the upper part, the silicon substrate is installed so as to cover the opening, and the surface of the silicon substrate and the inside of the container for evaluating metal impurities. The first aspect of the present invention is characterized in that a closed space is formed between the silicon substrate and the acid mixed solution, and the surface of the silicon substrate facing the closed space is subjected to gas phase decomposition treatment by the vapor generated from the acid mixed solution. The method for evaluating metal impurities on the surface of a silicon substrate according to the above method.

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