JP2024003336A - Semiconductor wafer impurity measurement method and impurity measurement jig - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor wafer impurity measurement method and an impurity measurement jig that can accurately measure the impurity concentration of a semiconductor wafer in analyzing impurities contained in the semiconductor wafer.

SOLUTION: A semiconductor wafer impurity measurement method includes the steps of: creating a first test piece SL1 from which a main surface of a semiconductor wafer W is not removed and a second test piece SL2 from which a part of the main surface of the semiconductor wafer W is removed to a predetermined depth in a thickness direction; performing gas phase decomposition on the first test piece and the second test piece in a closed space; dissolving the first test piece and the second test piece that have been subjected to gas phase decomposition to form respective liquid samples; performing mass spectrometry on each of the two liquid samples; and measuring the impurity concentration from a difference between the mass spectrometry results for the two liquid samples.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a semiconductor wafer impurity measurement method and an impurity measurement jig for measuring the concentration of metal impurities contained in a semiconductor wafer such as a silicon wafer.

Conventionally, in quality control of silicon wafers and crystals, metal impurities contained in silicon wafers have been measured and analyzed using an atomic absorption spectrophotometer, an ICP emission spectrometer, or an ICP mass spectrometer.
For example, when evaluating the depth analysis of metal impurities contained in a silicon wafer, the surface layer is removed by etching and the metal impurities contained in that part is measured.

Patent Document 1 (Japanese Unexamined Patent Publication No. 7-333121) discloses an analysis sample container (evaporation dish) in which a silicon analysis sample (silicon wafer sample) is placed in a closed container constituting a closed space system, and the sample. After storing the decomposition solution (mixed acid of hydrofluoric acid and nitric acid) in an isolated state without contacting each other, the sealed container is heated to decompose and sublimate (vapor phase decomposition) the siliceous analysis sample, It is described that the residue in the analysis sample container is collected and analyzed.

Further, Patent Document 2 (Japanese Patent Application Laid-open No. 2007-208198) discloses that the main surface of a semiconductor substrate is masked with a protective plate having an opening, the opening of the protective plate is filled with an etching solution, and the surface of the semiconductor substrate is An impurity analysis method is disclosed that includes a first step of etching the etching solution, and a second step of collecting the etching solution (liquid phase decomposition) and analyzing impurities in the surface layer of the semiconductor substrate.

Japanese Patent Application Publication No. 7-333121 Japanese Patent Application Publication No. 2007-208198

When performing gas phase decomposition of a sample using a sample decomposition solution (mixed acid of hydrofluoric acid and nitric acid) in a closed container as disclosed in Patent Document 1, decomposition residues of the sample are unlikely to remain; If it remains, there is a problem that the detection sensitivity decreases.
Further, when performing liquid phase decomposition using an etching solution as disclosed in Patent Document 2, metal impurities contained in the acid solution remain in the sample solution, resulting in a problem in that detection accuracy deteriorates.

The present invention has been made under the above circumstances, and provides a semiconductor wafer impurity measurement method and impurity measurement tool that can accurately measure the impurity concentration of a semiconductor wafer in the analysis of impurities contained in the semiconductor wafer. The purpose is to provide ingredients.

A method for measuring impurities in a semiconductor wafer according to the present invention, which has been made to solve the above problems, includes: an upper jig provided with a plurality of first openings formed with the same area in the surface direction and penetrating in the thickness direction; sandwiching the semiconductor wafer between a lower jig provided with a plurality of second apertures formed to match the position of the first aperture and penetrating in the thickness direction; and one of the plurality of first apertures. a step of removing a part of the main surface of the semiconductor wafer facing the first opening in the thickness direction; arranging the lower jig with the openings aligned; arranging the upper jig and the lower jig sandwiching the semiconductor wafer in a closed container together with the evaporation dish; a sample decomposition solution is poured into the container, and the semiconductor wafer facing the first opening is subjected to vapor phase decomposition by heating the closed container; , performing mass spectrometry measurements on a first liquid sample in which the main surface of the semiconductor wafer is not etched, and a second liquid sample in which a part of the main surface of the semiconductor wafer is removed by etching; , calculating the concentration of impurities in the surface layer of the semiconductor wafer removed by etching based on the difference between the measurement results of the second liquid sample.

Alternatively, the method for measuring impurities in a semiconductor wafer according to the present invention, which has been made in order to solve the above problems, includes: , sandwiching the semiconductor wafer between a lower jig provided with a plurality of second apertures formed to match the positions of the first apertures and penetrating in the thickness direction; filling one of the plurality of first openings with an etching solution and removing a part of the main surface of the semiconductor wafer facing the first opening by a first depth in the thickness direction; an evaporation dish having a plurality of bottomed holes; arranging the lower jig above with the plurality of second openings aligned; and placing the upper jig and the lower jig sandwiching the semiconductor wafer in a sealed container together with the evaporation dish. placing a sample decomposition solution in the bottom of the sealed container, heating the sealed container to perform vapor phase decomposition of the semiconductor wafer facing the first opening; a first liquid sample formed from a sample collected in , in which a portion of the main surface of the semiconductor wafer is removed by a first depth; and a first liquid sample in which a portion of the main surface of the semiconductor wafer is removed by a second depth; and calculating the concentration of impurities in the surface layer of the semiconductor wafer based on the difference between the measurement results of the first and second liquid samples. It has particular characteristics.

According to such a method, since there is no need to cleave the semiconductor wafer, metal impurities can be easily measured.
Furthermore, since the semiconductor wafer is subjected to gas phase decomposition, it is not affected by impurities contained in the chemical solution, and detection sensitivity can be improved compared to an analysis method using liquid phase decomposition. In addition, since gas phase decomposition is performed in a closed space, no decomposition residue remains, and two samples obtained from the same semiconductor wafer are subjected to gas phase decomposition in the same processing space and under the same conditions, resulting in highly accurate measurement results. can be obtained. Furthermore, the depth to be measured can be arbitrarily set by adjusting the amount removed by etching.

Further, the impurity measuring jig according to the present invention, which was made to solve the above problem, is used in the method for measuring impurities in semiconductor wafers, and is placed in a closed container in which a sample decomposition solution is placed in the bottom. , an impurity measuring jig used for vapor phase decomposition of semiconductor wafers, comprising: an upper jig having a plurality of first openings formed with the same area in the surface direction and penetrating in the thickness direction; a lower jig that is formed to match the position of the first opening and has a plurality of second openings penetrating in the thickness direction, and that sandwiches the semiconductor wafer between the lower jig and the upper jig; and an evaporation dish having a plurality of bottomed holes formed in accordance with the positions, and the first opening of the upper jig is used for forming a sample etched to an arbitrary depth on the semiconductor wafer. and is used for vapor phase decomposition of the semiconductor wafer facing the first opening by volatilization of the sample decomposition solution, and the vapor phase decomposed sample is collected into the bottomed hole of the evaporation dish. has.

Alternatively, the method for measuring impurities in a semiconductor wafer according to the present invention, which has been made in order to solve the above problems, is a method for measuring impurities in a semiconductor wafer, which analyzes impurities contained in the semiconductor wafer. A first test piece that has not been removed, and a second test piece that has the same area as the first test piece and that has a part of the main surface of the semiconductor wafer removed to a predetermined depth in the thickness direction. a step of performing gas phase decomposition on the first test piece and the second test piece in a closed space; and a step of performing gas phase decomposition on the first test piece and the second test piece. and a step of forming a liquid sample by using the two liquid samples as a solution, a step of performing mass spectrometry on each of the two liquid samples, and a step of measuring the impurity concentration from the difference between the mass spectrometry results for the two liquid samples. It is characterized by comprising the following.

According to such a method, since the test piece is subjected to gas phase decomposition, it is not affected by impurities contained in the chemical solution, and detection sensitivity can be improved compared to an analysis method using liquid phase decomposition. In addition, since the test piece is subjected to vapor phase decomposition in a closed space, it is difficult to leave decomposition residues, and two samples obtained from the same semiconductor wafer are subjected to vapor phase decomposition in the same processing space and under the same conditions, which improves accuracy. High measurement results can be obtained. Furthermore, the depth to be measured can be arbitrarily set by adjusting the amount removed by etching.

Alternatively, the method for measuring impurities in a semiconductor wafer according to the present invention, which has been made in order to solve the above problems, is a method for measuring impurities in a semiconductor wafer, which analyzes impurities contained in the semiconductor wafer. a first test piece in which a part of the main surface of the semiconductor wafer is removed in the thickness direction by a first depth; creating a second test piece from which only a second depth has been removed; performing gas phase decomposition on the first test piece and the second test piece in a closed space; A step of converting the first test piece and the second test piece into a solution and making each into a liquid sample, performing mass spectrometry on each of the two liquid samples, and mass spectrometry on the two liquid samples. and measuring the impurity concentration from the difference between the results.

According to such a method, the concentration of metal impurities in an arbitrary depth range can be measured by etching the two samples to arbitrary different positions.

According to the present invention, it is possible to provide a semiconductor wafer impurity measurement method and an impurity measurement jig that can accurately measure the impurity concentration of the semiconductor wafer in analyzing impurities contained in the semiconductor wafer.

FIG. 1 is a schematic cross-sectional view of a processing container used in a first embodiment of the method for measuring impurities in semiconductor wafers according to the present invention. FIG. 2 is a flowchart showing the flow of the first embodiment of the method for measuring impurities in semiconductor wafers of the present invention. FIG. 3 is a flowchart showing the flow of the second embodiment of the method for measuring impurities in semiconductor wafers of the present invention. FIG. 4 is a schematic cross-sectional view of a semiconductor wafer for explaining the second embodiment of the method for measuring impurities in a semiconductor wafer of the present invention. FIG. 5 is a schematic cross-sectional view of a processing container used for gas phase decomposition of a sample in the second embodiment of the method for measuring impurities in semiconductor wafers of the present invention. FIG. 6 is a flowchart showing the flow of the third embodiment of the method for measuring impurities in semiconductor wafers of the present invention. FIG. 7 is a schematic cross-sectional view of a semiconductor wafer for explaining the third embodiment of the method for measuring impurities in a semiconductor wafer of the present invention. FIG. 8 is a bar graph showing the results of the example.

Hereinafter, a method for measuring impurities in a semiconductor wafer and a jig for measuring impurities according to the present invention will be described with reference to the drawings. However, this embodiment will be described as an example of the present invention, and the present invention is not limited thereto. Furthermore, although this embodiment will be described using a silicon wafer, it is not limited to a silicon wafer, and may be a semiconductor wafer such as a SiC wafer or a GaN wafer. The method for measuring impurities in semiconductor wafers described below is for analyzing metal impurities contained in the surface layer of a silicon wafer.

First, a first embodiment of a method for measuring impurities in a semiconductor wafer according to the present invention will be described. In the first embodiment of the method for measuring impurities in semiconductor wafers according to the present invention, a processing container 20 shown in FIG. 1 is used.
The processing container 20 shown in FIG. 1 includes a lower outer cylindrical tube 21 which has an internal space and is open at the top, and a lower outer cylindrical tube 21 which is open at the bottom and whose lower end inner circumferential portion is screwed, for example, to the upper end outer circumferential portion of the lower outer cylindrical tube 21. The upper outer cylindrical tube 22 is fitted with the upper outer cylindrical tube 22. At the center of the bottom of the lower outer cylindrical tube 21, a mounting table 21a is arranged.
An evaporation dish 23 having a plurality of bottomed holes 23a is placed on the mounting table 21a, and a wafer jig 30 is placed on this evaporation dish 23 (evaporation plate 23). The dish 23 and the wafer jig 30 constitute the impurity measuring jig of the present invention).

The wafer jig 30 includes a lower jig 31 and an upper jig 32, and is configured to sandwich the silicon wafer W therebetween. Further, in the lower jig 31 and the upper jig 32, a plurality of openings 31a (first openings) are formed to vertically penetrate and have the same area in accordance with the position of the bottomed hole 23a of the evaporating dish 23. , 32a (second openings) are formed respectively.

FIG. 2 is a flowchart showing the flow of the first embodiment of the method for measuring impurities in semiconductor wafers according to the present invention.
First, the silicon wafer W is sandwiched between the wafer jigs 30, and a mixed acid of hydrofluoric acid and nitric acid is dropped from the plurality of openings 32a of the upper jig 32 to perform etching. At this time, for example, a mixed acid of hydrofluoric acid and nitric acid is poured (dropped) into each of the two openings 32a, and the depth of etching in the area corresponding to each of the two openings 32a is set to an arbitrary depth that is different from each other. (Step St1 in FIG. 2).

Next, as shown in FIG. 1, the wafer jig 30 holding the silicon wafer W therebetween is placed on the evaporation dish 23 in the processing container 20 (step St2 in FIG. 2). At this time, the openings 31a and 32a of the wafer jig 30 are aligned with the bottomed hole 23a of the evaporation dish 23.
In addition, a mixed solution 2 of hydrofluoric acid and nitric acid (sample decomposition solution) is put in the bottom of the lower outer cylindrical tube 21, and the processing container 20 is heated for 48 hours on a hot plate 10 at 150° C., and the gas phase is heated. A decomposition process is performed (step St3 in FIG. 2). That is, the mixed liquid 2 of hydrofluoric acid and nitric acid (HF+HNO ₃ ) is volatilized, and the vaporized gas phase of HF+HNO ₃ comes into contact with the upper surface of the silicon wafer W through the opening 32 a of the wafer jig 30 . The silicon (Si) substance of the silicon wafer W sublimates as hydrofluorosilicic acid (H ₂ SiF ₆ ) or silicon tetrafluoride (SiF ₄ ). The sublimated hydrofluorosilicic acid (H ₂ SiF ₆ ) and silicon tetrafluoride (SiF ₄ ) are absorbed into the mixed solution 2 of hydrofluoric acid and nitric acid (HF+HNO ₃ ), and are absorbed into the plurality of bottomed holes of the evaporating dish 23. Metal impurities remain in each of 23a.

Subsequently, the evaporating dish 23 is taken out and heated on a 150° C. hot plate until dry, and 1 ml of 1% nitric acid is poured into each bottomed hole 23a to a constant volume (Step St4 in FIG. 2).
Then, each constant volume solution (first liquid sample, second liquid sample) in each bottomed hole 23a is measured by ICP-MS or the like, and for example, the measured value of the constant volume solution in any two bottomed holes 23a is measured. Based on the difference in etching, the metal impurity concentration in the wafer surface layer corresponding to the etching difference is evaluated (step St5 in FIG. 2).

As described above, according to the first embodiment of the present invention, there is no need to cleave the silicon wafer W, so that metal impurities can be easily measured. Furthermore, since the silicon wafer is partially subjected to gas phase decomposition, it is not affected by impurities contained in the chemical solution, and detection sensitivity can be improved compared to an analysis method using liquid phase decomposition. Furthermore, the measurement depth can be set arbitrarily by adjusting the amount removed by etching.

In the first embodiment, gas phase decomposition is performed on regions with different etching depths, and the metal impurity concentration is determined from the difference between the measured values of these two samples. However, it is not limited to that form.
For example, the unetched region and the etched region may be subjected to vapor phase decomposition, and the metal impurity concentration may be determined from the difference between the measured values of these two samples.

Next, a second embodiment of the method for measuring impurities in a semiconductor wafer according to the present invention will be described.
FIG. 3 is a flowchart showing the flow of the second embodiment of the method for measuring impurities in semiconductor wafers of the present invention. FIG. 4 is a schematic cross-sectional view of a semiconductor wafer for explaining the second embodiment of the method for measuring impurities in a semiconductor wafer of the present invention.

First, on the main surface W1 of a silicon wafer W having a thickness T shown in FIG. 4(a), a partial region Ar1 is formed to an arbitrary depth y1 by etching as shown in FIG. 4(b). 3 step S1). For example, a mixed acid of hydrofluoric acid and nitric acid is used for etching.
Next, as shown in FIG. 4(c), the silicon wafer W is cleaved, and as shown in FIG. 4(d), an unetched test piece SL1 (first test piece) and an etched test piece SL2 ( A second test piece) is prepared (step S2 in FIG. 3). The test piece SL1 and the test piece SL2 have the same area in the wafer surface direction.

Note that the order of step S1 and step S2 may be reversed. That is, before performing the etching in step S1, the silicon wafer W is cleaved to take out the test pieces SL1 and SL2, and the main surface W1 side of the test piece SL2 is etched with, for example, a mixed acid of hydrofluoric acid and nitric acid. The depth portion may be removed. Even in this manner, it is possible to create a test piece SL2 from which the depth portion to be measured has been removed and a test piece SL1 from which the depth portion to be measured has not been removed.

Next, the two test pieces SL1 and SL2 are placed in the evaporation dishes 5 of FIG. 5, respectively, and these evaporation dishes 5 are placed in the processing container 1 (step S3 of FIG. 3). A mixed solution 2 of hydrofluoric acid and nitric acid is put into the bottom of the processing container 1, and the processing container 1 is heated, for example, on a hot plate 10 at 150° C. for 48 hours (step S4 in FIG. 3). Thereby, the test pieces SL1 and SL2 are subjected to gas phase decomposition. That is, the mixed solution 2 of hydrofluoric acid and nitric acid (HF+HNO ₃ ) is volatilized, and the vaporized gas phase of HF+HNO ₃ comes into contact with the silicon wafer test pieces SL1 and SL2. The silicon (Si) of the test pieces SL1 and SL2 sublimates as hydrofluorosilicic acid (H ₂ SiF ₆ ) and silicon tetrafluoride (SiF ₄ ). The sublimed hydrofluorosilicic acid (H ₂ SiF ₆ ) and silicon tetrafluoride (SiF ₄ ) are absorbed by the mixture 2 of hydrofluoric acid and nitric acid (HF+HNO ₃ ), and metal impurities remain in the evaporating dish 5. do.

Subsequently, the evaporating dish 5 is heated on a hot plate at 150° C. until dry, and 1 ml of 1% nitric acid is added thereto to give a constant volume (step S5 in FIG. 3).
The constant volume solutions of test piece SL1 and test piece SL2 are each subjected to mass spectrometry using ICP-MS, etc., and the concentration of metal impurities in the surface layer portion that has been removed by etching is determined from the difference between the measured values of test piece SL1 and test piece SL2. (Step S6 in FIG. 3).

As described above, according to the second embodiment of the present invention, since the test pieces SL1 and SL2 are subjected to gas phase decomposition, they are not affected by impurities contained in the chemical solution, and compared to an analysis method using liquid phase decomposition, Detection sensitivity can be improved. In addition, because the gas phase decomposition of the test pieces SL1 and SL2 is performed in a closed space, it is difficult to leave decomposition residues, and the gas phase decomposition of the samples SL1 and SL2 obtained from the same silicon wafer W is performed in the same processing space and under the same conditions. Therefore, highly accurate measurement results can be obtained. Furthermore, the depth to be measured can be arbitrarily set by adjusting the amount removed by etching.

Regarding the impurity measurement method described above, in order to remove contamination caused by the cleavage operation, both sides of the test pieces SL1 and SL2 may be etched to the same extent after cleavage, for example, with a mixed acid of hydrofluoric acid and nitric acid.

Next, a third embodiment of the method for measuring impurities in a semiconductor wafer according to the present invention will be described.
FIG. 6 is a flowchart showing the flow of the third embodiment of the method for measuring impurities in semiconductor wafers of the present invention. FIG. 7 is a schematic cross-sectional view of a semiconductor wafer for explaining the third embodiment of the method for measuring impurities in a semiconductor wafer of the present invention.

First, as shown in FIG. 7(b), a partial region Ar2 is formed at an arbitrary depth y3 by etching on the main surface W1 of a silicon wafer W having a thickness T shown in FIG. 7(a). A region Ar3 different from Ar2 is formed by etching to a depth y4 that is deeper than the depth y3 (step Sp1 in FIG. 6). For example, a mixed acid of hydrofluoric acid and nitric acid is used for etching.
Next, as shown in FIG. 7(c), the silicon wafer W is cleaved, and as shown in FIG. 7(d), a test piece SL3 (first test piece) etched to a depth of y3 and a test piece SL3 (first test piece) etched to a depth of y4 are obtained. An etched test piece SL4 (second test piece) is created (step Sp2 in FIG. 6). The test piece SL1 and the test piece SL2 have the same area in the wafer surface direction.

Note that the order of step Sp1 and step Sp2 may be reversed. That is, before performing the etching in step Sp1, the silicon wafer W is cleaved to take out the test pieces SL3 and SL4, the main surface W1 side of the test piece SL3 is etched to a depth y1, and the main surface W1 side of the test piece SL4 is etched. may be etched to a depth of y4. Even in this manner, it is possible to create test pieces SL3 and SL4 from which the depth portion to be measured has been removed.

Next, similarly to the first embodiment, the two test pieces SL3 and SL4 are respectively placed in the evaporation dishes 5 shown in FIG. 5, and these evaporation dishes 5 are placed in the processing container 1 (step Sp3 in FIG. 6). . A mixed solution 2 of hydrofluoric acid and nitric acid is put into the bottom of the processing container 1, and the processing container 1 is heated, for example, on a hot plate 10 at 150° C. for 48 hours (step Sp4 in FIG. 6). Thereby, the test pieces SL3 and SL4 are subjected to gas phase decomposition. That is, the mixed solution 2 of hydrofluoric acid and nitric acid (HF+HNO ₃ ) is volatilized, and the vaporized gas phase of HF+HNO ₃ comes into contact with the silicon wafer test pieces SL3 and SL4. The silicon (Si) of test pieces SL3 and SL4 sublimates as hydrofluorosilicic acid (H ₂ SiF ₆ ) and silicon tetrafluoride (SiF ₄ ). The sublimed hydrofluorosilicic acid (H ₂ SiF ₆ ) and silicon tetrafluoride (SiF ₄ ) are absorbed by the mixture 2 of hydrofluoric acid and nitric acid (HF+HNO ₃ ), and metal impurities remain in the evaporating dish 5. do.

Subsequently, the evaporating dish 5 is heated on a hot plate at 150° C. until dry, and 1 ml of 1% nitric acid is added thereto to give a constant volume (step Sp5 in FIG. 6).
Then, the fixed volume solutions of test piece SL3 and test piece SL4 are subjected to mass spectrometry using ICP-MS, etc., and the concentration of metal impurities in the surface layer portion that has been removed by etching is determined from the difference between the measured values of test piece SL3 and test piece SL4. (Step Sp6 in FIG. 6).

As described above, according to the third embodiment of the present invention, by setting the etching depths of the samples SL3 and SL4 to arbitrary different positions, it is possible to measure the concentration of metal impurities in an arbitrary depth range. can.
In addition, as in the second embodiment, since the test pieces SL3 and SL4 are subjected to gas phase decomposition, they are not affected by impurities contained in the chemical solution, and detection sensitivity is improved compared to an analysis method using liquid phase decomposition. be able to. In addition, since the test pieces SL3 and SL4 are subjected to vapor phase decomposition in a closed space, it is difficult to leave decomposition residues, and samples SL3 and SL4 obtained from the same silicon wafer W are subjected to vapor phase decomposition in the same processing space and under the same conditions. Therefore, highly accurate measurement results can be obtained.

The method for measuring impurities in semiconductor wafers and the jig for measuring impurities according to the present invention will be further explained based on Examples.

(Example 1)
In Example 1, 3 ml of a solution containing 38% hydrofluoric acid and 68% nitric acid mixed at a volume ratio of 1:4 was dropped on a part of the main surface of a silicon wafer, which was a sample, to coat the surface of the wafer. The part was etched for 2 minutes (performed twice in total).
Thereafter, the silicon wafer was cleaved, and about 1 g each of a test piece of the etched portion (thickness: 505 μm) and a test piece of the unetched portion (thickness: 775 μm) were prepared.
Both test pieces were placed in each evaporation dish 5 of the processing container 1 shown in FIG. 5, and a liquid mixture consisting of 150 ml of 38% hydrofluoric acid and 50 ml of 68% nitric acid was placed in the bottom of the processing container 1.
Next, gas phase decomposition was performed by heating the processing container 1 on a hot plate 10 at 150° C. for 48 hours.
Thereafter, the evaporating dish 5 was taken out and heated on a hot plate at 150° C. until dry, and 1 ml of 1% nitric acid was added thereto to give a constant volume. Metal impurities in the fixed volume solution were measured by ICP-MS.
The results of Example 1 are shown in Table 1. Table 1 shows the measurement results for Fe, Na, and Mg.

As shown in Table 1, 5.8E11 of Fe, 9.0E10 of Na, and 1.6E12 atoms/ ^cm3 of Mg were detected in the etched test piece, and 5.8E11 of Fe was detected in the unetched test piece. 2E11, Na was detected at 2.4E11, and Mg was detected at 2.9E12 atoms/ ^cm3 .
The metal impurity concentration of the portion removed by etching was calculated from the metal impurity concentration and thickness of each test piece using the following formula 1. Fe was 3.9E11atoms/cm ³ , Na was 5.4E11atoms/cm ³ , Mg was 5.2E12atoms/ ^cm3 .

(Formula 1)
Metal impurity concentration in the etched removed area =
((metal impurity concentration of test piece A) x (thickness of test piece A) - (metal impurity concentration of test piece B) x (thickness of test piece B)) / ((thickness of test piece A) - (Thickness of test piece B))

(Example 2)
In Example 2, a silicon wafer as a sample is sandwiched between the wafer jigs 30 shown in FIG. 3 ml of the mixed solution was added dropwise, and the surface layer of the wafer was etched for 2 minutes (this was carried out twice in total).
Thereafter, a mixed solution consisting of 150 ml of 38% hydrofluoric acid and 50 ml of 68% nitric acid was poured into the bottom of the lower outer tube 21, and the evaporation dish 23 and wafer jig 30 were installed so as not to come into contact with the mixed solution.
Next, gas phase decomposition was performed by heating the processing container 20 on a 150° C. hot plate 10 for 48 hours.
Thereafter, the evaporating dish 23 was taken out and heated on a hot plate at 150° C. until dry, and 1 ml of 1% nitric acid was added thereto to give a constant volume. Metal impurities in the fixed volume solution were measured by ICP-MS.
The results of Example 2 are shown in Table 2. Table 2 shows the measurement results for Fe, Na, and Mg.

As shown in Table 2, 5.8E11 of Fe, 9.0E10 of Na, and 4.0E10 atoms/ ^cm3 of Mg were detected in the etched test piece, and 5.8E11 of Fe was detected in the unetched test piece. 2E11, Na was detected at 9.0E10, and Mg was detected at 4.0E10 atoms/ ^cm3 .
The metal impurity concentration of the portion removed by etching was calculated from the metal impurity concentration and thickness of each test piece using the above formula 1, and it was found that Fe was 3.9E11 atoms/cm ³ , Na was 9.0E10 atoms/cm ³ , and Mg was 4.0E10atoms/ ^cm3 .

(Comparative example 1)
In Comparative Example 1, 3 ml of a solution containing 38% hydrofluoric acid and 68% nitric acid mixed at a volume ratio of 1:4 was dropped onto a silicon wafer as a sample, and the surface layer of the wafer was etched for 2 minutes. (Conducted twice in total).
The etching solution was collected, and with 5 ml of 20% hydrochloric acid added thereto, it was poured into an evaporating dish. Thereafter, the evaporating dish was heated on a hot plate at 150° C. until dry, and 1 ml of 1% nitric acid was added thereto to give a constant volume.
Then, the metal impurity concentration of the fixed volume solution was measured by ICP-MS. As a result of Comparative Example 1, 1.0E13 atoms/cm3 of Fe, 1.0E13 Na, and 1.0E13 atoms/ ^cm3 of Mg were detected.

The results of Examples 1 and 2 and Comparative Example 1 are shown in the bar graph of FIG.
As shown in FIG. 8, compared to Examples 1 and 2, the metal impurity concentration in Comparative Example 1 was much higher. This is considered to be due to the measurement of metal impurities contained in the chemical solution. Therefore, it was confirmed that according to the present invention, highly accurate measurement of impurity concentration is possible.

20 Processing container 21 Lower outer tube 22 Upper outer tube 23 Evaporation dish (impurity measurement jig)
23a Bottomed hole 30 Wafer jig (impurity measurement jig)
31 Upper jig 31a Opening 32 Lower jig 32a Opening SL1 Test piece SL2 Test piece SL3 Test piece SL4 Test piece W Silicon wafer (semiconductor wafer)

Claims (5)

an upper jig including a plurality of first openings formed with the same area in the surface direction and penetrating in the thickness direction; and a plurality of second openings formed in accordance with the position of the first openings and penetrating in the thickness direction. sandwiching a semiconductor wafer between a lower jig having an opening;
filling one of the plurality of first openings with an etching solution and removing a part of the main surface of the semiconductor wafer facing the first opening in the thickness direction;
arranging the lower jig on an evaporating dish having a plurality of bottomed holes, aligning the plurality of second openings;
The upper jig and the lower jig sandwiching the semiconductor wafer are placed together with the evaporation dish in a closed container, a sample decomposition solution is put in the bottom of the closed container, and the closed container is heated to vapor phase decomposition of the semiconductor wafer facing the first opening;
A first liquid sample formed from the sample collected in the evaporation dish by the vapor phase decomposition, in which the main surface of the semiconductor wafer is not etched, and a second liquid sample, in which the main surface of the semiconductor wafer is partially removed by etching. performing mass spectrometry measurements on the liquid sample;
calculating the concentration of impurities in the surface layer of the semiconductor wafer removed by etching based on the difference between the measurement results of the first and second liquid samples;
A method for measuring impurities in a semiconductor wafer, comprising: an upper jig including a plurality of first openings formed with the same area in the surface direction and penetrating in the thickness direction; and a plurality of second openings formed in accordance with the position of the first openings and penetrating in the thickness direction. sandwiching a semiconductor wafer between a lower jig having an opening;
filling one of the plurality of first openings with an etching solution, and removing a part of the main surface of the semiconductor wafer facing the first opening by a first depth in the thickness direction;
filling another one of the plurality of first openings with an etching solution, and removing a part of the main surface of the semiconductor wafer facing the first opening by a second depth in the thickness direction;
arranging the lower jig on an evaporating dish having a plurality of bottomed holes, aligning the plurality of second openings;
The upper jig and the lower jig sandwiching the semiconductor wafer are placed together with the evaporation dish in a closed container, a sample decomposition solution is put in the bottom of the closed container, and the closed container is heated to vapor phase decomposition of the semiconductor wafer facing the first opening;
a first liquid sample formed from the sample collected in the evaporation dish by the vapor phase decomposition, from which a portion of the main surface of the semiconductor wafer is removed by a first depth; and a portion of the main surface of the semiconductor wafer. a second liquid sample from which the liquid sample has been removed to a second depth;
Calculating the concentration of impurities in the surface layer of the semiconductor wafer based on the difference between the measurement results of the first and second liquid samples;
A method for measuring impurities in a semiconductor wafer, comprising: An impurity measuring jig used in the method for measuring impurities in a semiconductor wafer according to claim 1 or 2, disposed in a closed container containing a sample decomposition solution at the bottom, and used for vapor phase decomposition of the semiconductor wafer. And,
an upper jig comprising a plurality of first openings formed with the same area in the surface direction and penetrating in the thickness direction;
a lower jig having a plurality of second openings formed in accordance with the positions of the plurality of first openings and penetrating in the thickness direction, and sandwiching the semiconductor wafer between the lower jig and the upper jig;
an evaporation dish having a plurality of bottomed holes formed in accordance with the position of the second opening,
The first opening of the upper jig is used to form a sample etched to an arbitrary depth on the semiconductor wafer, and the semiconductor wafer facing the first opening is used to form a sample etched to an arbitrary depth. 1. A jig for measuring impurities, which is used for vapor phase decomposition of wafers, and wherein a sample subjected to vapor phase decomposition is collected into a bottomed hole of the evaporation dish. A semiconductor wafer impurity measurement method for analyzing impurities contained in a semiconductor wafer, the method comprising:
A first test piece from which the main surface of the semiconductor wafer has not been removed; and a first test piece having the same area as the first test piece, where a part of the main surface of the semiconductor wafer is removed to a predetermined depth in the thickness direction. creating a second test piece,
performing gas phase decomposition on the first test piece and the second test piece in a closed space;
forming a solution of the first test piece and the second test piece that have been subjected to gas phase decomposition to form respective liquid samples;
performing mass spectrometry on each of the two liquid samples;
Measuring the impurity concentration from the difference between the mass spectrometry results for the two liquid samples;
A method for measuring impurities in a semiconductor wafer, comprising: A semiconductor wafer impurity measurement method for analyzing impurities contained in a semiconductor wafer, the method comprising:
A first test piece obtained by removing a part of the main surface of the semiconductor wafer by a first depth in the thickness direction, and a first test piece having the same area as the first test piece and a part of the main surface of the semiconductor wafer. and a second test piece in which the portion is removed by a second depth in the thickness direction;
performing gas phase decomposition on the first test piece and the second test piece in a closed space;
A step in which the first test piece and the second test piece subjected to gas phase decomposition are made into a solution and each becomes a liquid sample;
performing mass spectrometry on each of the two liquid samples;
Measuring the impurity concentration from the difference between the mass spectrometry results for the two liquid samples;
A method for measuring impurities in a semiconductor wafer, comprising:

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