JP2013115261A - Recovery method of impurity on semiconductor substrate surface and quantitative analysis method for impurity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recovery method of impurity on a semiconductor substrate surface, allowing contacting to etching liquid only by one surface of a semiconductor substrate, being the entire said surface, with no contamination of impurity from other than the semiconductor substrate, and to provide a quantitative analysis method of impurity on the semiconductor substrate surface which uses said recovery method of the impurity.SOLUTION: In the recovery method of impurity on a semiconductor substrate surface, an etching liquid 2 is added to a support container 1 which has a flat bottom surface, a semiconductor substrate 3 which is to be analysed is placed on it, and after being left out for a time period required for dissolving of a surface of the semiconductor substrate 3 in the etching liquid 2, the etching liquid 2 is recovered. With the assumption that a diameter of the semiconductor substrate 3 is X cm, the amount of etching liquid 2 that is added to the support container 1 is 2×(X/5)ml to 3×(X/2)ml, and a contact angle between the support container 1 and the etching liquid 2 is 65° or larger. The present invention also relates to the quantitative analysis method of impurity on the semiconductor substrate surface which uses the stated recovery method of impurity.

Description

  The present invention relates to a method for collecting impurities on the surface of a semiconductor substrate used for quantitative analysis of impurities contained in the vicinity of the surface of the semiconductor substrate, and a quantitative analysis method using this collection method.

  Impurities such as metals contained in the vicinity of the surface of the semiconductor substrate deteriorate the characteristics of the semiconductor device and reduce the yield of semiconductor device manufacturing. Therefore, measures to prevent contamination of the semiconductor substrate by impurities have become an important issue. In order to implement the countermeasure, it is necessary to analyze the impurities contained in the vicinity of the surface of the semiconductor substrate with ultra-high sensitivity.

  As an analysis method for impurities such as metals contained in the vicinity of the surface of a semiconductor substrate, an atomic absorption method (AAS), an inductively coupled plasma emission spectroscopy (ICP-OES), an inductively coupled plasma mass spectrometry (ICP-MS), etc. It has been known. In these analyses, a predetermined area on the surface of the semiconductor substrate is brought into contact with a liquid in which the semiconductor is soluble (etching liquid) to dissolve (etch) the semiconductor and impurities in the vicinity of the surface, and the liquid thus obtained is washed or the like. It collect | recovers and the sample solution of a measuring object is obtained.

  If the surface of a predetermined area in contact with the etching solution is the entire one surface (one side) of the semiconductor substrate, the area can be clearly grasped. Accordingly, various methods have been proposed for preparing a sample solution for quantitative analysis by bringing one whole surface of a semiconductor substrate into contact with an etching solution and dissolving it.

  For example, Patent Document 1 discloses a wafer that has a dent that is curved toward the center, and that contains an acid (etching solution) in an acid-resistant container having the same size as the wafer (semiconductor substrate), and is formed around the container. A method is described in which a wafer is placed on a step corresponding to the shape of the substrate and the acid is brought into contact with the wafer. Patent Document 2 discloses a method for bringing the surface of a silicon wafer (a type of semiconductor substrate) into contact with a chemical solution (etching solution) and providing an appropriate volume of dilute water (chemical solution) on a tray that is just large enough to contain a silicon wafer. A method is described in which a silicon wafer is gently placed so that the surface comes into contact with this dilute water. Further, in Patent Document 3, a recovery liquid (etching liquid) such as concentrated sulfuric acid is supplied to the surface of a semiconductor substrate, and a hydrophobic member is disposed so that the recovery liquid is sandwiched between the semiconductor substrate and the recovery liquid. Describes a method of widely contacting the semiconductor substrate with the semiconductor substrate.

JP-A-10-64966 JP 2001-77158 A JP 2011-82338 A

  However, the sample solution preparation methods described in Patent Document 1 and Patent Document 2 require a dedicated container having the same size and shape as the semiconductor substrate. Since the special container is required to be reused, impurities are easily mixed (contaminated) in the special container when it is reused. Therefore, it is necessary to clean and manage the dedicated container for keeping the container clean, and there is a problem that it takes time and effort for this purpose.

  Further, if the size of the semiconductor substrate is slightly different from that of the dedicated container, the acid flows around the back surface of the semiconductor substrate and dissolves the back surface. Even when the semiconductor substrate is chipped, acid flows around the back surface and dissolves the back surface. For accurate quantitative analysis, it is necessary to accurately grasp the area of the semiconductor substrate in contact with the etching solution, but if the back surface is dissolved, the area cannot be accurately grasped, and therefore accurate measurement cannot be performed. There is also a problem.

  Further, in the method described in Patent Document 3, the entire surface of the wafer cannot be uniformly contacted with the etching solution unless the range of the weight of the hydrophobic member and the amount and concentration of the etching solution are strictly limited. The problem that it is impossible, etc. arises and the problem that an exact measurement cannot be performed arises. In Patent Document 3, it is stated that heating at about 100 to 290 ° C. is preferable in order to promote dissolution of metal impurities in concentrated sulfuric acid. The balance between the amount and concentration of the etching solution is lost, and it becomes more difficult to etch the entire wafer surface.

  The present invention provides a method for recovering impurities on the surface of a semiconductor substrate in which only one surface (one surface) of the semiconductor substrate and the entire surface can be in contact with the etching solution and no impurities are contaminated (contamination) from other than the semiconductor substrate. This is the issue. The present invention also provides a method for quantitative analysis of impurities on the surface of a semiconductor substrate using the impurity recovery method.

  As a result of the study, the inventor has dropped a droplet amount of the etching solution on a support container having a flat bottom surface, and when the semiconductor substrate is placed on the droplet and floated, the droplet amount falls within a predetermined range. Then, it has been found that contact with the etching solution occurs on one side of the entire semiconductor substrate and only on one side. According to this method, a dedicated container having the same size as that of the semiconductor substrate is not required, and only one surface of the semiconductor substrate can be easily and entirely etched, and the solution dissolved by etching can be collected and analyzed. Thus, the present invention has been completed by finding that impurities can be analyzed quantitatively with high accuracy. That is, the said subject is achieved by the structure shown below.

According to the first aspect of the present invention, an etching solution is added to a support container having a flat bottom surface, a semiconductor substrate to be analyzed is placed thereon, and after being left for a time required for dissolution in the etching solution of the semiconductor substrate surface, A method for recovering an etching solution, wherein when the diameter of the semiconductor substrate is Xcm, the amount of the etching solution added to the support container is 2 × (X / 5) ² ml or more, 3 × (X / 2) ^A method for recovering impurities on the surface of a semiconductor substrate, wherein the contact angle is ² ml or less and the contact angle between a support container and an etching solution is 65 ° or more.

  The support container has a flat bottom surface so that contact between the bottom surface of the support container and the semiconductor substrate does not occur when a semiconductor substrate having a flat surface floats on the etching solution. In order to prevent the etching solution that floats off the semiconductor substrate from spilling out from the periphery, it is preferable to have a collar around the periphery.

  The support container is formed of a material having a contact angle with the etching solution of 65 ° or more. When a support container made of a material having a contact angle of less than 65 ° is used, acid flows around the back surface of the semiconductor substrate and the back surface is likely to be dissolved.

  As the support container, a clean container having corrosion resistance that is not dissolved by the etching solution and having no impurities that affect the measurement results of the quantitative analysis on the surface thereof is used. For example, when a strong acid such as aqua regia is used as an etchant, an acid-resistant glass or petri dish made of fluororesin is used.

  The size of the support container may be any size as long as the bottom surface can contain the semiconductor substrate, and does not have to be the same size as the semiconductor substrate. As long as the bottom surface is larger than the semiconductor substrate, it can be used even if the type and size of the semiconductor substrate is different, so that it is not necessary to use a dedicated container for etching a specific semiconductor substrate. Therefore, it is not necessary to reuse the dedicated container, and it can be used for etching (quantitative analysis) of the semiconductor substrate without worrying about contamination (contamination) from the previous etching.

In the method of the present invention, when the diameter of the semiconductor substrate is Xcm, the amount of the etching solution added to the support container is 2 × (X / 5) ² ml or more and 3 × (X / 2) ² ml or less. It is characterized by being. That is, by setting the amount of the etching solution within the above range, only one side of the semiconductor substrate can be in contact with the etching solution. And even when there is a chip in the semiconductor substrate, only one surface can be in contact with the etching solution without acid flowing around the back surface of the semiconductor substrate.

As a result, the area of the semiconductor substrate in contact with the etching solution can be accurately grasped, and accurate quantitative analysis can be performed. When the amount of the etching solution is less than 2 × (X / 5) ² ml, the entire surface of one side of the semiconductor substrate cannot be brought into contact with the etching solution, and a portion that does not come into contact with a part is generated. On the other hand, when the amount of the etching solution exceeds 3 × (X / 5) ² ml, the etching solution flows around the back surface of the semiconductor substrate and dissolves the back surface.

  The semiconductor substrate is a thin substrate made of a semiconductor used for manufacturing a semiconductor element, and is called a wafer, a wafer or the like. Examples of the semiconductor substrate to which the method of the present invention is applied include silicon wafers, GaAs wafers, GaN wafers, InP wafers, SiC wafers, AlN wafers and the like. In addition, the present invention can be applied to any flat substance other than the semiconductor substrate in principle.

In the method of the present invention, it is necessary to float the semiconductor substrate on the etching solution so that the semiconductor substrate does not come into contact with the support container. Can float. Therefore, the present invention is applied to a semiconductor substrate having a thickness equal to or less than a limit thickness. The limit thickness is a thickness represented by 1 / (ρ−ρ0) × (2γρ0 / g) ^0.5 , where ρ is the density of the semiconductor substrate, ρ0 is the density of the etching solution, and γ is the etching solution. The surface tension, g, represents the gravitational acceleration (0.98 m / sec ² ). The limit thickness is 0.93 mm for GaAs, 0.78 mm for GaN, and about 1.05 mm for InP. The thickness of a normal semiconductor wafer is about 0.1 to 0.5 mm, which is much thinner than the limit thickness. The method of the invention is fully applicable.

  As long as the surface of the semiconductor substrate is flat so as not to come into contact with the support container when it floats on the etching solution, the method of the present invention can be applied even if there is a difference between a mirror surface and a non-mirror surface.

  As described above, the method for recovering impurities on the surface of a semiconductor substrate according to the present invention places a semiconductor substrate on a droplet of an etching solution dropped on a flat support container on the bottom surface, and the flatness and surface tension of the etching solution. By using this, the semiconductor substrate is floated on the droplet of the etching solution, and only one side of the semiconductor substrate is brought into contact with the etching solution uniformly and entirely, so that all impurities in the vicinity of the one side can be recovered. Is the method.

  The invention according to claim 2 is characterized in that the etching solution is obtained by diluting rare aqua regia with ultrapure water, and the dilute aqua regia: ultra pure water is 1: 1 to 49 in volume ratio. The method for recovering impurities on the surface of a semiconductor substrate according to claim 1. Examples of the etching solution include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, hydrofluoric acid, hydrogen peroxide solution, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, and the like, but an aqueous solution of a strong acid that dissolves the semiconductor is preferably used. There are many cases. In particular, when the semiconductor substrate is a GaAs wafer, a GaN wafer, an InP wafer, or the like, a dilute aqua regia, hydrochloric acid, nitric acid diluted with ultrapure water is preferable. Here, dilute aqua regia refers to a 3: 1 mixture of 37% by mass hydrochloric acid and 60% by mass nitric acid. Ultrapure water refers to water that does not contain impurities that hinder quantitative analysis or affect analysis results.

  Next, each step of the method for recovering impurities on the surface of the semiconductor substrate will be described in claim 1 or claim 2.

  First, a support container having a bottom surface larger than the semiconductor substrate is prepared. The support container needs to be sufficiently cleaned so that impurities that affect the results of quantitative analysis do not adhere and the contact angle with the etching solution is 65 ° or more. An etching solution in an amount within the predetermined range is dropped on the bottom of the support container. It is preferable that the etching solution is dropped as close as possible to the central portion of the bottom of the support container. If the liquid is dropped at a position away from the central portion, the etching liquid may not spread over the entire surface of one side of the semiconductor substrate when the semiconductor substrate is placed.

After dropping the etching solution, a semiconductor substrate is placed on the etching solution. When the semiconductor substrate is placed, the etching solution is spread by the weight of the semiconductor substrate, the entire surface of the semiconductor substrate comes into contact with the etching solution, and the semiconductor substrate floats on the etching solution due to its surface tension. If the amount of the etching solution is 2 × (X / 5) ² ml or more, the entire one surface of the semiconductor substrate can be brought into contact with the etching solution. Further, when the amount of the etching solution is 3 × (X / 5) ² ml or less, the etching solution does not enter the back surface of the semiconductor substrate and dissolve the back surface. Moreover, if the thickness of a semiconductor substrate is below a limit thickness, a semiconductor substrate can be floated on etching liquid and a semiconductor substrate and a support container will not contact.

  After the semiconductor substrate to be analyzed is placed on the etching solution, the semiconductor substrate surface is left for a time required for dissolution in the etching solution. This leaving is preferably carried out until all of the portion of the semiconductor substrate (usually near the surface) that is considered to contain impurities is dissolved. Alternatively, if only a predetermined part (a predetermined thickness from the surface) of the semiconductor substrate is dissolved and the amount of impurities in another part can be estimated by quantifying the amount of impurities, the process until the predetermined part is dissolved Left for hours.

  After leaving, the etching solution in which the semiconductor is dissolved is collected. It is preferable to collect the entire amount of the etching solution. Therefore, for example, the semiconductor substrate and the support container are washed with ultrapure water, and the entire amount of the washing solution is collected to obtain a sample solution for quantitative analysis.

  According to a third aspect of the present invention, the amount of impurities in a sample solution obtained by diluting the collected etching solution with ultrapure water after performing the method for collecting impurities on the surface of the semiconductor substrate according to the first or second aspect. This is a method for quantitatively analyzing impurities on the surface of a semiconductor substrate.

  The recovered etching solution is a combination of the etching solution in which the semiconductor is dissolved and the cleaning solution obtained when the etching solution adhering to the support container and the semiconductor substrate is washed with ultrapure water. By sufficiently performing this cleaning, the entire amount of the etching solution in which the semiconductor is dissolved can be recovered. After the entire amount of the etching solution is recovered, the sample solution is preferably fixed to a constant volume to obtain a sample solution. The constant volume is performed, for example, by transferring the entire amount of the collected etching solution to a volumetric flask or the like, then diluting with ultrapure water to make a constant volume, and shaking to make it uniform.

  The sample solution obtained by constant volume is subjected to quantitative analysis, and the content of impurities is calculated from the measured value. Since the content of impurities is usually a trace amount, preferred examples of quantitative analysis include AAS, ICP-OES, ICP-MS and the like that enable a trace amount of quantification. In addition, when the total amount of the collected etching solution (including the cleaning solution) can be accurately grasped, the collected etching solution is sufficiently agitated by ultrasonic waves or the like without performing a constant volume, Analysis may be performed to determine the impurity content from the measured value and the amount of the recovered etching solution.

  According to the method for recovering impurities on the surface of the semiconductor substrate of the present invention, impurities in the vicinity of the surface of the semiconductor substrate can be recovered in the sample solution for quantitative analysis without introducing (contamination) impurities from other than the semiconductor substrate. it can. In addition, the entire surface of the semiconductor substrate contacts the etching solution. On the other hand, the contact area can be accurately grasped because there is no contact on the other side of the semiconductor substrate other than the one surface. Therefore, impurities in the vicinity of the semiconductor substrate surface can be quantitatively analyzed with high accuracy using the sample solution obtained by the recovery method of the present invention.

It is sectional drawing which shows typically 1 process of an example of the recovery method of the impurity of the semiconductor substrate surface of this invention. It is sectional drawing which shows typically 1 process of an example of the recovery method of the impurity of the semiconductor substrate surface of this invention. It is sectional drawing which shows typically 1 process of an example of the recovery method of the impurity of the semiconductor substrate surface of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the following embodiments. Various modifications can be made without departing from the spirit of the present invention.

  FIG. 1 is a cross-sectional view schematically showing one step of an example of a method for collecting impurities on the surface of a semiconductor substrate of the present invention. Represents a semiconductor substrate to be mounted on the substrate. In FIG. 1, 1 represents a support container having a flat bottom surface 1a and a flange 1b, and 2 represents an etching solution. Reference numeral 3 represents a semiconductor substrate, and reference numeral 4 represents a holding means for the semiconductor substrate 3. The holding means 4 may be a vacuum pipette or the like, but may be a handle made of an adhesive tape or the like, and is not particularly limited as long as it can hold the semiconductor substrate 3.

  The etching solution 2 is dropped near the center of the bottom surface of the support container 1 by a pipette or the like to form droplets as shown in FIG. The semiconductor substrate 3 is held by the holding means 4, moves as indicated by an arrow in the figure, and is placed on the droplet of the etching solution 2.

FIG. 2 shows a state when the semiconductor substrate 3 is placed on the droplet of the etching solution 2. The etching solution 2 is spread by the weight of the semiconductor substrate 3, and the semiconductor substrate 3 is in a state of floating on the etching solution 2. FIG. 2A shows that the amount of the etching solution 2 is 2 × (X / 5) ² ml or more and 3 × (X / 2) ² ml or less when the diameter of the semiconductor substrate 3 is Xcm. The case where the contact angle between the support container 1 and the etching solution 2 is 65 ° or more is shown. As shown in FIG. 2A, the entire one surface 3b (lower surface in the drawing) of the semiconductor substrate 3 is in contact with the etching solution 2, while the other surface 3a (back surface, upper surface in the drawing). ) Has no portion in contact with the etching solution 2.

When the amount of the etching solution 2 exceeds 3 × (X / 2) ² ml when the diameter of the semiconductor substrate 3 is Xcm, the amount of the etching solution 2 is too large, as shown in FIG. The back surface 3b of the semiconductor substrate 3 is also in contact with the etching solution 2 and a sample solution that enables accurate quantitative analysis cannot be obtained. When the contact angle of the etching solution 2 is less than 65 °, the semiconductor substrate 3 cannot be floated on the etching solution 2 due to the surface tension of the etching solution 2, and as a result, the back surface 3 a of the semiconductor substrate 3 is also etched. 2 or the semiconductor substrate 3b comes into contact with the support container 1a, and a sample solution that enables accurate quantitative analysis cannot be obtained.

When the amount of the etching solution 2 is less than 2 × (X / 2) ² ml when the diameter of the semiconductor substrate 3 is Xcm, the amount of the etching solution 2 is too small, as shown in FIG. The entire surface of one side 3b of the semiconductor substrate 3 cannot be brought into contact with the etching solution 2, and a sample solution that enables accurate quantitative analysis cannot be obtained.

  2A, the semiconductor substrate 3 is removed from the etching solution 2 after being left for a predetermined time in the state shown in FIG. The standing time is several minutes to several days when the InP wafer is melted at room temperature with 10-fold diluted aqua regia, but it may be heated within a range that does not impair the spirit of the present invention in order to promote dissolution. .

  When the etching solution 2 is removed from the top surface, the etching solution 2 adheres to the one surface 3b of the semiconductor substrate 3. Therefore, the one surface is washed with ultrapure water, and the washed cleaning solution is combined with the etching solution 2. The FIG. 3 is a cross-sectional view schematically showing how the one surface 3b of the semiconductor substrate 3 is cleaned with ultrapure water and how the cleaning solution is combined with the etching solution 2 to form the sample solution stock solution 5. In the figure, 6 represents ultrapure water, and as shown in the figure, the ultrapure water 6 cleans the etching solution 2 adhering to one side 3b of the semiconductor substrate 3 and becomes the cleaning solution 7 to be combined with the etching solution 2. A sample solution stock solution 5 is generated.

  The obtained sample solution undiluted solution 5 is transferred to a constant volume means such as a volumetric flask, and ultrapure water is added to make a predetermined volume, thereby obtaining a sample solution for quantitative analysis. Examples of a method for forming a uniform solution include a method of stirring by shaking and the like, a method of irradiating ultrasonic waves, and the like. By measuring the sample solution thus obtained by AAS, ICP-OES, ICP-MS, etc., quantitative analysis of impurities can be performed.

  Examples of impurities quantitatively analyzed by the method of the present invention include Ca, Cr, Cu, Fe, Ni, and Zn.

[Preparation of standard sample]
A standard solution in which 50 μg of Ca, Cr, Cu, Fe, Ni, and Zn are dissolved on one side of an InP wafer having a diameter of 2 inches (5 cm) and a thickness of 360 μm is added and dried at room temperature for one day. A standard sample of InP wafer contaminated with 50 μg each of Cu, Fe, Ni, and Zn was prepared.

Example 1
A Teflon (registered trademark) petri dish with a flat bottom surface and a diameter of about 10 cm (support container: 70 ° contact angle with an etching solution below) is sufficiently cleaned, and a 37 mass% hydrochloric acid is pipetted at the center using a pipette. Then, 2.5 ml of an etching solution obtained by diluting a mixed solution of 3: 1 with a mass ratio of nitric acid and 60 mass% nitric acid 10 times with ultra pure water was dropped. When the above-mentioned standard sample was placed on the droplet formed by dripping so that the contaminated one side was in contact with the droplet, the standard sample floated on the etching solution, and the entire one side was in contact with the etching solution. On the other hand, the back surface of the standard sample was not in contact with the etching solution.

  The standard sample was left on the etching solution for 1 day at room temperature. Thereafter, as shown in FIG. 3, the standard sample was moved from above the etching solution, the one surface was washed with ultrapure water, and the washing solution was combined with the etching solution. The total amount of the sample solution stock solution thus obtained was transferred to a volumetric flask, and ultrapure water was added to make a constant volume, and the mixture was shaken and homogenized to obtain a sample solution. The obtained sample solution was measured by ICP-MS, and a quantitative value M (μg) was obtained for each of Ca, Cr, Cu, Fe, Ni, and Zn that contaminates one side of the standard sample. The same operation was performed three times (N = 3) to obtain a quantitative value M (μg).

  Table 1 shows the ratio (recovery rate) of the quantitative value M (μg) thus obtained to the actual amount of contamination (50 μg) (recovery rate): (M / 50) × 100 (%) for three operations and Ca , Cr, Cu, Fe, Ni, Zn are shown. As shown in Table 1, the variation between the three operations was small, and a recovery rate of 97% or more was obtained for any contaminating element, confirming the effectiveness of the method of the present invention. .

Example 2
Except for the thicknesses of 300 μm, 500 μm, 1000 μm, 1050 μm, and 1200 μm, respectively, the same InP wafer as that of the standard sample was prepared and placed on the etching solution in the same manner as in Example 1. The thickness was 300 μm and 500 μm. The InP wafer having a thickness of 1050 μm and 1200 μm did not float on the etching solution, and the bottom surface of the wafer was in contact with the bottom surface of the petri dish. Further, the back surface (upper surface) of the InP wafer was also in contact with the etching solution. From this result, in the case of an InP wafer, the limit thickness (the maximum thickness at which the wafer floats in the etching solution) is between about 1000 to 1050 μm, and it is shown that the method of the present invention can be applied if the thickness is 1000 μm.

Example 3
The same standard sample as in Example 1 was used except that the petri dish (support container) was made to have a contact angle of 40 °, 60 °, 90 °, and 110 ° with the etching solution (diluted aqua regia). When the InP wafer (standard sample) was placed on the etching solution, when the contact angle was 40 ° and 60 °, the InP wafer (standard sample) did not float on the etching solution, and the bottom surface of the wafer and the bottom surface of the petri dish Contacted. On the other hand, in the case of 90 ° and 110 °, the InP wafer (standard sample) floated on the etching solution as in the case of 70 ° (Example 1). This result shows that the contact angle between the support container and the etching solution needs to be about 65 ° or more in order to effectively carry out the method of the present invention.

Example 4
The recovery rate for Cu was determined in the same manner as in Example 1 except that the amount of the etching solution was 1.5 ml, 2.0 ml, 3.0 ml, and 3.5 ml. Table 2 shows the recovery rate and how the InP wafer (standard sample) is placed on the etching solution.

Example 5
A test sample (semiconductor substrate) was prepared in the same manner as the standard sample of Example 1 using an InP wafer having a diameter of 4 inches (10 cm), and a petri dish (supporting container) having a diameter of 15 cm was used. , 6 ml, 8 ml, 12 ml, and 14 ml were used in the same manner as in Example 1 to obtain the recovery rate for Cu. Table 3 shows the recovery rate and how the InP wafer (standard sample) is placed on the etching solution.

From the results of Table 2 and Table 3, when W / (X / 5) ² is 1.5, the entire surface of one side of the wafer is not in contact with the etching solution, the impurity recovery rate is low, and accurate quantitative analysis is possible. It has been shown that this is not possible. On the other hand, when W / (X / 5) ² is 1.5, it is indicated that the back surface of the wafer is also in contact with the etching solution, and accurate quantitative analysis cannot be performed. On the other hand, when W / (X / 5) ² is in the range of ² to 3, the entire one surface of the wafer is in contact with the etching solution, while the back surface of the wafer is not in contact with the etching solution. The recovery rate of Cu is 99% or more or 100%, and it is shown that the method of the present invention can be applied sufficiently effectively if the amount of the etching solution is within this range.

1. 1. Support container 2. Etching solution 3. Semiconductor substrate 4. holding means 5. Sample solution stock solution 6. Ultrapure water Cleaning liquid

Claims (3)

In this method, an etching solution is added to a support container having a flat bottom surface, a semiconductor substrate to be analyzed is placed on the support vessel, and the etching solution is recovered after leaving the semiconductor substrate surface for a time required for dissolution in the etching solution. Then, when the diameter of the semiconductor substrate is Xcm, the amount of the etching solution added to the support container is 2 × (X / 5) ² ml or more and 3 × (X / 2) ² ml or less, and the support A method for recovering impurities on the surface of a semiconductor substrate, wherein the contact angle between the container and the etching solution is 65 ° or more.   2. The semiconductor according to claim 1, wherein the etching solution is obtained by diluting dilute aqua regia with ultrapure water, and the dilute aqua regia: ultra pure water is 1: 1 to 49 in a volume ratio. A method for collecting impurities on the substrate surface.   3. The semiconductor according to claim 1, wherein after performing the method for collecting impurities on the surface of the semiconductor substrate, the amount of impurities in a sample solution obtained by diluting the collected etching solution with ultrapure water is measured. Quantitative analysis method for impurities on substrate surface.

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