JP2016119332A - Manufacturing method of recovery instrument, recovery method of metal impurity, and analysis method of metal impurity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a manufacturing method of a recovery instrument capable of accurately recovering and analyzing metal impurities present on the surface of a substrate; a recovery method of metal impurities; and an analysis method of metal impurities.SOLUTION: A recovery instrument 1 is formed of a fluorine resin, and has: a support tray 2 having a flat support surface 21; and a ring member 3 which is placed on the support tray 2 and acts as a recovery instrument. An inner surface of an opening 34 of the ring member 3 is subjected to surface melting processing at 340-380°C and surface polishing processing so that the surface roughness becomes 200 nm or less. When metal impurities are recovered, a semiconductor substrate W is mounted on the support tray 2, the ring member 3 is placed on the semiconductor substrate W, and the outer periphery of the semiconductor substrate W is sandwiched between the support tray 2 and the ring member 3. Then, a recovery liquid is injected into the opening 34, and the metal impurities present on the surface of the semiconductor substrate W are eluted in the recovery liquid. Then, the recovery liquid is taken out from the opening 34, and the metal impurities in the recovery liquid are measured by ICP-MS or the like.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a recovery tool for recovering metal impurities present on the surface of a semiconductor substrate, a method for recovering metal impurities present on the surface of a semiconductor substrate, and an analysis method.

  Metal impurities present on the surface of a semiconductor substrate are one of the causes of reducing semiconductor device characteristics and semiconductor device manufacturing yield. Therefore, it is important to take measures against contamination by metal impurities on the substrate surface, and a highly sensitive analysis technique for metal impurities on the substrate surface is required.

  Methods for analyzing metal impurities present on the substrate surface include atomic absorption spectrometry (AAS), inductively coupled plasma optical emission spectrometry (ICP-OES), and inductively coupled plasma mass spectrometry. The method (ICP-MS: Inductively Coupled Plasma Mass Spectrometry) is known.

  In addition, in order to analyze metal impurities by these analysis methods, it is necessary to recover metal impurities on the surface of the substrate, and various methods have been proposed as recovery methods. For example, Patent Document 1 discloses that a natural oxide film on a substrate surface is vapor-phase decomposed with hydrofluoric acid vapor, and then a chemical solution (recovered solution) for recovering metal impurities is uniformly scanned on the surface of the semiconductor substrate. Describes a method for incorporating metal impurities into a chemical solution.

  In addition to this, in Patent Document 1, (1) an acid-resistant container having a depression with a curved central part is used, a recovery solution is put into the depression, and a substrate with the analysis surface facing downward is placed in the container. Thus, a method is disclosed in which metal impurities on the substrate surface are taken into the recovery liquid. Patent Document 2 discloses (2) a method in which a recovery solution is added to a support container having a flat bottom surface, and a metal substrate is taken into the recovery solution by placing an analysis target substrate thereon. . Further, in Patent Document 3 and Non-Patent Document 1, (3) the analysis target substrate includes a flat support surface disposed on the back surface side of the analysis target substrate and a ring member disposed on the front surface side of the analysis target substrate. A method is disclosed in which the metal impurities are taken into the recovery liquid by supporting the metal so as to be sandwiched and injecting the recovery liquid into the opening of the ring member.

  In addition, these documents describe the use of a fluororesin such as PTFE (polytetrafluoroethylene) as a jig and container used when recovering metal impurities.

JP-A-10-64966 JP 2013-115261 A JP 2007-207783 A Miyuki Takenaka, 4 others, “Measurement of depth distribution of ultra-fine chromium, iron, nickel and copper in silicon wafers by thermal vaporization / inductively coupled plasma mass spectrometry”, Analytical Chemistry, Japan Analytical Chemistry Society 1994, Vol. 43, p173-176

  In the recovery methods (1) to (3) above, the recovery tool (acid-resistant container, support container, ring member) and the recovery liquid come into contact with each other during recovery of the metal impurities present on the substrate surface. For this reason, the elution of metal impurities from the recovery tool to the recovery liquid and the adsorption of metal impurities from the recovery liquid to the recovery tool reduce the accuracy of recovery of metal impurities present on the substrate surface. There is a problem that the analysis accuracy of metal impurities is lowered.

  The present invention has been made in view of the above problems, and provides a method for manufacturing a recovery tool, a method for recovering metal impurities, and a method for analyzing metal impurities that can accurately recover and analyze metal impurities present on the surface of a substrate. Is an issue.

  As a result of the study, the present inventor found that the surface condition and the surface processing roughness of the part of the collecting device (wetted part) in contact with the collected liquid are important, and completed the present invention.

That is, the present invention is a method of manufacturing a recovery instrument that has a liquid contact portion that is used when recovering metal impurities present on the surface of a semiconductor substrate and that contacts the recovery liquid supplied to the surface during the recovery,
A preparation step of preparing a resin molded product molded into a shape having the liquid contact part;
A melting step of melting the surface of the wetted part in the molded product;
A polishing step of performing surface polishing of the wetted part after performing the melting step;
It is characterized by including.

  According to the present invention, in the preparation step, a resin molded product molded into a shape necessary as a collecting tool is prepared, and surface treatment is performed on the liquid contact portion in the prepared molded product. Specifically, first, so-called melting processing is performed to melt the surface portion of the wetted part in the melting step, so that the fine holes on the wetted part surface formed at the time of molding can be eliminated. Next, since the surface of the wetted part is polished by the polishing step, the surface of the wetted part can be smoothed. As a result, elution of metal impurities from the wetted part when in contact with the recovered liquid and adsorption of metal impurities to the wetted part can be reduced, and the metal impurities present on the substrate surface can be recovered accurately.

  Further, in the present invention, the collection device is arranged on the surface side of the semiconductor substrate at the time of collection, and a ring-shaped as the liquid contact portion that exposes a specific part of the surface of the semiconductor substrate at the time of the collection. It has an opening, and the recovered liquid can be injected into the opening. As a result, the elution and adsorption of metal impurities between the opening and the recovery liquid can be reduced, and the metal impurities present at a specific site on the substrate surface can be accurately recovered.

  Moreover, in this invention, it is preferable to prepare the molded article of a fluororesin in a preparation process. At this time, the kind of fluororesin can be polytetrafluoroethylene. In this way, by producing a collection device with a fluororesin such as polytetrafluoroethylene, it is possible to obtain a collection device with high chemical resistance and to suppress contamination (cross-contamination) from the collection device to the collected liquid. it can. In addition, the molding of the fluororesin is performed, for example, by performing a process of cutting a raw material obtained by pressure firing the raw material into a desired shape. In addition, there are fine pores peculiar to the press fired product, and the surface processing roughness is large. It is particularly effective when such a pressure-fired cut product of fluororesin is applied to the present invention.

  Moreover, when a fluororesin is used, it is preferable to perform the surface melt processing of the wetted part at 340 ° C. to 380 ° C. in the melting step. The melting point of the fluororesin is 327 ° C., and if it is 340 ° C. or less, there is a problem that the fluororesin does not melt or is difficult to process because it has high viscosity even when melted. Further, at 380 ° C. or higher, there is a problem that processing in the molten fluororesin is difficult because it expands (fires). By performing surface melt processing of the wetted part at 340 ° C. to 380 ° C., the viscosity can be lowered and expansion of air in the fluororesin can be suppressed, and as a result, the wetted part surface can be easily melt processed. .

  In the case where a fluororesin is used, it is preferable to perform surface polishing of the wetted part so that the surface roughness Ra is 200 nm or less in the polishing step. Thereby, as shown in the below-mentioned Example, the elution and adsorption | suction of the metal impurity between liquid contact part-recovery liquid can be reduced effectively.

  The method for recovering metal impurities of the present invention is characterized by recovering metal impurities present on the surface of the semiconductor substrate by supplying a recovery liquid to the surface of the semiconductor substrate using the recovery tool obtained by the manufacturing method of the present invention. And

  In this way, by using a recovery tool that has been subjected to surface treatment (melting process, polishing process) of the wetted part, elution of metal impurities from the wetted part when in contact with the recovered liquid, or to the wetted part Therefore, the metal impurities present on the substrate surface can be accurately recovered.

Further, in the recovery method of the present invention, the recovery tool is arranged in a ring shape as the liquid contact part in which the semiconductor substrate is disposed on the surface side and a specific part of the surface of the semiconductor substrate is exposed during the placement. With an opening of
The recovery solution is injected into the opening in a state where the semiconductor substrate is supported by the recovery tool and a back-side support member having a flat support surface that supports the back surface of the semiconductor substrate.

  In this way, during collection, the collected recovery liquid and the back-side support member are supported so as to sandwich the semiconductor substrate, so that the injected collected liquid can be held in the opening, and the metal impurities present in a specific part of the substrate surface Can be collected accurately. In other words, it is possible to suppress the occurrence of cross-contamination due to the collected liquid flowing outside the opening (a part other than a specific part on the substrate surface, the back surface of the substrate, etc.)

  In the recovery method of the present invention, the semiconductor substrate can be a silicon carbide substrate. Since the surface of the silicon carbide substrate has hydrophilicity, the recovery liquid supplied to the surface of the substrate can be spread thinly and easily compared to a semiconductor substrate having a hydrophobic surface. That is, even with a small amount of collected liquid, the collected liquid can be distributed to each part of the substrate surface. By reducing the recovered liquid, elution and adsorption of metal impurities between the wetted part and the recovered liquid can be suppressed.

  In the recovery method of the present invention, the semiconductor substrate can be a silicon substrate. Since the surface of the silicon substrate has hydrophobicity, the recovered liquid does not spread thinly and easily gathers in part compared to a semiconductor substrate having a hydrophilic surface due to the influence of surface tension. For this reason, a large amount of recovery liquid is required to cover the substrate surface with the recovery liquid. In this invention, since the collection | recovery instrument which performed the said surface treatment with respect to the liquid contact part which contacts a large amount of collection liquids is used, the elution and adsorption | suction of the metal impurity between liquid contact parts-recovery liquid can be suppressed. In addition, when a large amount of the recovery liquid is used, the recovery liquid tends to remain in the wetted part, which causes a reduction in the recovery rate of metal impurities. In the present invention, the surface treatment is performed on the wetted part. Therefore, the deterioration of the recovery rate can be suppressed. As a result, the metal impurities can be accurately analyzed.

  In the recovery method of the present invention, the recovery solution is a mixed aqueous solution of hydrofluoric acid and hydrogen peroxide solution, a mixed aqueous solution of hydrofluoric acid, hydrochloric acid and hydrogen peroxide solution, or a mixed aqueous solution of hydrofluoric acid, nitric acid and hydrochloric acid. By using a mixed aqueous solution of hydrofluoric acid and hydrogen peroxide solution or a mixed aqueous solution of hydrofluoric acid, hydrochloric acid and hydrogen peroxide solution as the recovery liquid, metal impurities present on the substrate surface can be eluted (recovered) into the mixed aqueous solution. Further, by using a mixed aqueous solution of hydrofluoric acid, nitric acid, and hydrochloric acid as the recovery liquid, not only the substrate surface but also metal impurities in the substrate near the surface can be eluted into the mixed solution.

  The metal impurity analysis method of the present invention is characterized in that after the metal impurity recovery method of the present invention is carried out, the amount of metal impurities in the recovered solution is measured. According to this, since the amount of metal impurities in the recovered liquid that suppresses the elution and adsorption of metal impurities between the wetted part and the recovered liquid is measured, it is possible to accurately analyze the metal impurities present on the substrate surface.

It is side surface sectional drawing of a collection | recovery jig. It is the flowchart which showed the manufacturing procedure of the ring member. It is the figure which showed the investigation result of the metal impurity elution amount from a PTFE test piece. It is the figure which showed the investigation result of the metal impurity adsorption amount to the PTFE test piece surface. It is the figure which showed the metal impurity measurement result of the SiC substrate surface in an Example. It is the figure which showed the metal impurity measurement result of the SiC substrate surface in a comparative example. It is the figure which showed the metal impurity measurement result of the silicon substrate surface in an Example. It is the figure which showed the metal impurity measurement result of the silicon substrate surface vicinity in an Example. It is the figure which showed the metal impurity measurement result of the silicon substrate surface in a comparative example. It is the figure which showed the metal impurity measurement result of the silicon substrate surface vicinity in a comparative example. It is side surface sectional drawing of the collection | recovery jig | tool in a comparative example.

  Embodiments of the present invention will be described below with reference to the drawings. In the present embodiment, an example in which the present invention is applied to a case where metal impurities present on the surface of a semiconductor substrate are collected and analyzed by the same method as described in Patent Document 3 and Non-Patent Document 1 will be described. . FIG. 1 shows a side cross-sectional view of the recovery jig 1 of the present embodiment. FIG. 1 also illustrates a semiconductor substrate W (hereinafter also referred to as an analysis target substrate) that is set (fixed) on the recovery jig 1 and is an analysis target of metal impurities.

  The recovery jig 1 is configured similarly to the recovery jigs described in Patent Document 3 and Non-Patent Document 1, and includes a support tray 2 and a ring member 3. The support plate 2 and the ring member 3 are made of PTFE (polytetrafluoroethylene). The support tray 2 is formed in a bottomed cylindrical shape. Specifically, the support plate 2 has a circular and bottomed opening as viewed from above, and the opening is formed to have a diameter equal to or larger than the diameter of the analysis target substrate W. In FIG. 1, the opening is formed to have the same diameter as that of the analysis target substrate W. The bottom surface 21 in the opening is formed as a flat surface. Further, a screw portion is formed on the side surface 22 in the opening.

  The ring member 3 is formed in a ring shape (cylindrical shape). Specifically, the ring member 3 has an opening 34 (a hatched portion in FIG. 1) penetrating between the upper surface and the lower surface of the ring member 3. When the ring member 3 is installed as shown in FIG. 1, the size and position of the opening 34 are set such that a specific part of the surface of the analysis target substrate W where metal impurities are collected is exposed from the opening 34. Determined. In FIG. 1, most of the analysis target substrate W excluding the outer peripheral portion (the inner portion of the circle having a diameter slightly smaller than the diameter of the analysis target substrate W centered on the substrate center) is set as the specific portion.

  Further, the inner surface of the opening 34 is subjected to surface melting processing and surface polishing by a manufacturing process described later. The inner surface has a surface roughness Ra (arithmetic mean roughness) of 200 nm or less.

  The ring member 3 has an insertion portion 31 that is formed to have the same outer diameter as the opening diameter of the support tray 2 and is inserted into the opening of the support tray 2. The outer peripheral surface 32 of the insertion portion 31 is formed with a screw portion that is screw-coupled with the screw portion 22 (side surface of the opening) of the support plate 2 when inserted into the opening of the support plate 2. Further, the ring member 3 has a large-diameter portion 33 having a diameter larger than the diameter of the insertion portion 31 so as to be connected to the upper end of the insertion portion 31.

  In addition, the ring member 3 corresponds to the collection | recovery instrument of this invention, the opening part 34 corresponds to a liquid-contact part, and the support plate 2 corresponds to a back surface side support member.

  The ring member 3 is manufactured according to the procedure shown in FIG. First, a PTFE molded product formed into a shape necessary for the ring member 3 (a shape having an opening 34) is prepared (S1). Specifically, for example, a PTFE raw material is pressure-fired to form a PTFE material having a shape that can be easily machined into the shape shown in FIG. 1, and the material is cut into the shape shown in FIG. (Machining). On the inner surface of the opening 34 in the obtained molded product (pressure-fired product), there are fine holes unique to the pressure-fired product. Further, since the inner surface of the opening 34 is a cutting surface, the surface processing roughness is large. In addition, the process of S1 corresponds to the preparation process of this invention.

  Next, surface melting processing is performed at 340 ° C. to 380 ° C. for the opening 34 of the molded product obtained in S1 (S2). Specifically, heat of 340 ° C. to 380 ° C. is applied to the inner surface of the opening 34 to melt the surface portion. The time for applying heat is, for example, within 30 minutes. By applying heat at 340 ° C. to 380 ° C., the inner surface can be melted, the viscosity of the inner surface at the time of melting can be made appropriate, and the expansion of air in the molded product can be suppressed. Further, by performing processing (smoothing) on the inner surface in the molten state, fine holes existing on the inner surface can be eliminated, and the surface roughness of the inner surface can be reduced. Note that step S2 corresponds to the melting step of the present invention.

  Next, surface polishing is performed so that the surface roughness Ra (arithmetic average roughness) is 200 nm or less with respect to the opening 34 after the surface melting processing of S2 is performed (S3). Note that step S3 corresponds to the polishing step of the present invention. The ring member 3 is obtained through the above steps.

  As for the manufacturing method of the support dish 2, since there is no liquid contact part in contact with the recovered liquid in the support dish 2, there is no need for surface melting processing and surface polishing. ) Is obtained by cutting.

  Next, a procedure for collecting and analyzing metal impurities on the surface of the analysis target substrate W using the collection jig 1 will be described. First, the analysis target substrate W is placed on the bottom surface 21 of the support tray 2. Any type of analysis target substrate W may be used, and for example, a silicon carbide (SiC) substrate or a silicon (Si) substrate may be used.

  After placing the analysis target substrate W, next, the insertion portion 31 of the ring member 3 is inserted into the opening of the support tray 2. At this time, by rotating the ring member 3 (large-diameter portion 33) around the central axis, the insertion portion 31 is inserted into the opening of the support tray 2, and along with the insertion, the screw portion 32 of the ring member 3 is supported. The screw portion 22 of the plate 2 is screwed. The insertion part 31 is inserted into the opening of the support plate 2 until the lower surface 35 of the insertion part 31 contacts the surface (outer peripheral part) of the analysis target substrate W. As a result, the analysis target substrate W is fixed (supported) to the recovery jig 1 such that the outer peripheral portion of the analysis target substrate W is sandwiched between the support tray 2 and the ring member 3.

  Thereafter, a chemical solution (recovery solution) that elutes metal impurities present on the surface of the analysis target substrate W is injected into the opening 34. As this recovery liquid, for example, a mixed aqueous solution of hydrofluoric acid and hydrogen peroxide, a mixed aqueous solution of hydrofluoric acid, hydrochloric acid and hydrogen peroxide, or a mixed aqueous solution of hydrofluoric acid, nitric acid and hydrochloric acid is used. Although any mixed aqueous solution is used, metal impurities on the substrate surface can be eluted. However, when a mixed aqueous solution of hydrofluoric acid, nitric acid and hydrochloric acid is used, not only the substrate surface but also the substrate in the vicinity of the surface. Metal impurities present in the aqueous solution can also be eluted in the mixed aqueous solution. Therefore, when it is desired to collect and analyze only the metal impurities on the substrate surface, it is preferable to use a mixed aqueous solution of hydrofluoric acid and hydrogen peroxide solution or a mixed aqueous solution of hydrofluoric acid, hydrochloric acid and hydrogen peroxide solution. In addition, when it is desired to collect and analyze metal impurities present on the substrate surface and in the vicinity of the substrate, it is preferable to use a mixed aqueous solution of hydrofluoric acid, nitric acid and hydrochloric acid.

  The amount of the recovery liquid injected into the opening 34 is determined according to the size of the specific part of the analysis target substrate W exposed from the opening 34 and the type of the analysis target substrate W. Specifically, the larger the specific part, the greater the amount of the collected liquid. In addition, when the analysis target substrate W is a substrate having a hydrophobic surface such as a silicon substrate, the amount of the recovered liquid is increased as compared with a substrate having a hydrophilic surface such as a silicon carbide substrate. As a result, the recovered liquid can be reliably supplied to the hydrophobic substrate surface that is difficult to spread thinly on the substrate surface due to the influence of the surface tension.

  After injecting the recovery liquid, the recovery liquid is stirred so as to spread evenly over the substrate surface exposed to the opening 34, and is allowed to stand for a predetermined time (for example, 5 minutes). Thereby, metal impurities existing on the substrate surface or in the vicinity of the surface (including the surface) can be eluted (recovered) into the recovery liquid. Further, since the inner surface of the opening 34 has been subjected to the above-described surface melting processing and surface polishing processing, it is possible to suppress the metal impurities present in the ring member 3 from being eluted into the recovered liquid. Moreover, it can suppress that the metal impurity eluted in the collection | recovery liquid from the substrate surface adsorb | sucks to the opening part 34. FIG.

  Further, since the entire back surface of the analysis target substrate W is supported by the support tray 2 and the outer peripheral portion of the analysis target substrate W is sandwiched between the support tray 2 and the ring member 3, the recovery injected into the opening 34. It can suppress that a liquid wraps around the opening part 34 (for example, the outer peripheral part and back surface of the analysis object board | substrate W). That is, the recovered liquid can be reliably held in the opening 34. As described above, only the metal impurities existing on the surface of the analysis target substrate W or in the vicinity of the surface can be accurately recovered in the recovery liquid.

  Thereafter, the recovery jig 1 is tilted to extract the recovery liquid from the opening 34, and the metal impurities in the extracted recovery liquid are measured by ICP-MS, ICP-OES, atomic absorption spectrometry (AAS) or the like. Thereby, the metal impurity which exists in the surface of the analysis object board | substrate W or the surface vicinity can be analyzed correctly.

Hereinafter, the present invention will be described more specifically with reference to examples of the present invention.
Example 1
In the present invention, first, using a test piece, the relationship between the surface condition and surface processing roughness of the test piece, the amount of metal impurities eluted from the test piece to the recovery liquid, and the amount of metal impurity adsorption from the recovery liquid to the test piece The following survey was conducted. The material of the test piece was PTFE. Based on the investigation results, the optimum machining conditions for the inner surface of the opening of the ring member were found.

  First, a plurality of test pieces made of PTFE (25 mm × 35 mm × 2 mm) were produced by cutting (Ra = 1200 nm), and some of the test pieces were polished on the surface to further reduce the surface processing roughness, The roughness (Ra) was 200 nm. Moreover, what cut the surface of the cut test piece at 340 ° C. to 380 ° C. (Ra = 450 nm) and further polished the surface after melt processing (Ra = 200 nm) were prepared. In other words, a test piece with cutting only, a test piece with cutting + surface polishing, a test piece with cutting + surface melting, a test piece with cutting + surface melting + surface polishing 4 types of test pieces were prepared. The following processes were implemented using each prepared test piece.

<Process 1: Removal of surface metal impurities from test piece>
PFA (tetrafluoroethylene) containing a mixed solution of hydrofluoric acid + nitric acid + hydrochloric acid + water (hydrofluoric acid approx. 10%, nitric acid approx. 12%, hydrochloric acid approx. 7%) to remove metal impurities adhering during test piece fabrication The test piece was placed in a beaker made of (~ perfluoroalkyl vinyl ether copolymer), heated on a hot plate at 80 ° C for 2 hours, and washed with ultrapure water several times.

<Process 2: Investigation of metal impurity elution amount from test piece>
Put 50 mL of a mixed solution of hydrofluoric acid + nitric acid + hydrochloric acid + water (about 10% hydrofluoric acid, about 12% nitric acid, about 7% hydrochloric acid) into a well-washed PFA beaker until there is no impurity elution. A PFA ball having a diameter of 5 mm that had been thoroughly washed was placed in a beaker. Here, when the test piece (flat plate) is put into the beaker as it is, the flat surface of the test piece sticks to the bottom surface of the beaker, and the mixed solution does not sufficiently reach the surface of the test piece. By inserting a PFA ball, a part of the test piece rides on the PFA ball and floats from the bottom of the beaker, so that the mixed solution can be spread all over the surface of the test piece.

  Next, one test piece after performing Step 1 was put in a beaker and heated at 80 ° C. for 20 minutes to elute metal impurities from the test piece. The amount of eluted metal impurities was measured by ICP-MS. This process was repeated for the number of test pieces.

  The measurement result of the amount of metal impurities eluted from each test piece is shown in FIG. FIG. 3 shows the amount of metal impurities eluted from the four types of test pieces (shown as A, B, C, and D in FIG. 3) for each type of metal impurity (Na, Mg, Al, etc.). . In FIG. 3, the result of E (chemical blank) shows the amount of metal impurities originally present in the mixed aqueous solution used for elution of metal impurities. Therefore, the value obtained by subtracting the result of E from the results of A to D indicates the amount of metal impurities eluted from the test piece into the mixed solution.

  From the results of A in FIG. 3 and the other cases (B, C, D), it can be seen that the larger the surface processing roughness is, the more metal impurities are eluted. From the results of B and C, it can be seen that when surface melting is performed, the amount of metal impurities eluted is equal to or less than that obtained when only surface polishing is performed. Furthermore, when the results of A to D are compared, the result of D is the smallest metal impurity elution amount in any metal impurity. That is, it can be seen that the amount of elution of metal impurities is greatly reduced by performing surface melting and then smoothing the surface.

<Process 3: Investigation of metal impurity adsorption amount on test piece surface>
Put 50 mL of a mixed solution of hydrofluoric acid + hydrochloric acid + hydrogen peroxide water + water (hydrofluoric acid about 8%, hydrochloric acid about 4%, hydrogen peroxide water about 7%) into a PFA beaker that has been thoroughly washed until no impurities are eluted. Similarly, a PFA ball having a diameter of 5 mm, which was thoroughly washed until no impurities were eluted, was placed in a beaker. Next, one test piece after step 1 is put into a beaker and immersed for 5 minutes at room temperature. Subsequently, the test piece was taken out and thoroughly washed with pure water. The amount of metal impurities in the soaked mixed solution was measured by ICP-MS, and was taken as the value before soaking the contaminated liquid.

  Next, in a 5% nitric acid solution at room temperature containing 10 ng / ml of Na, Mg, Al, Ca, Ti, Cr, Fe, Ni, Cu, Zn, Mo, Sn, and W, respectively, hydrofluoric acid + hydrochloric acid + excess The test piece after being immersed in a mixed solution of hydrogen oxide water and water was immersed for 10 minutes to adsorb metal impurities on the surface of the test piece. Next, the test piece was taken out and thoroughly washed with ultrapure water. The reason for performing this water washing is that in this adsorption amount investigation, the influence of metal impurities that are not removed (adsorbed) even if the water washing process is performed is considered. In a PFA beaker, 50 mL of a mixed solution of hydrofluoric acid + hydrochloric acid + hydrogen peroxide water + water (hydrofluoric acid approximately 8%, hydrochloric acid approximately 4%, hydrogen peroxide solution approximately 7%) was thoroughly washed until no impurities were eluted. In the same manner, a PFA ball having a diameter of 5 mm, which was sufficiently washed until no impurities were eluted, was placed in a beaker. Next, the test piece after immersion in the contaminated liquid was placed in this beaker and immersed at room temperature for 5 minutes. Subsequently, the test piece was taken out and thoroughly washed with pure water. The amount of metal impurities in the soaked mixed solution was measured by ICP-MS, and the value after immersion in the contaminated liquid was taken. The difference in values before and after the immersion of the contaminated liquid in the same test piece was defined as the amount of adsorbed metal impurities.

  The measurement result of the metal impurity adsorption amount of each test piece is shown in FIG. FIG. 4 shows the amount of metal impurities adsorbed by the above four types of test pieces (shown as A, B, C, and D in FIG. 4) for each type of metal impurity (Na, Mg, Al, etc.). From the results of A in FIG. 4 and other cases (B, C, D), it can be seen that the larger the surface processing roughness is, the more metal impurities are adsorbed. From the results of B and C, it can be seen that when surface melting is performed, the amount of adsorption of metal impurities excluding Na is smaller than when only surface polishing is performed. Furthermore, when the results of AD are compared, the result of D is the smallest metal impurity adsorption amount in any metal impurity. That is, it can be seen that the amount of metal impurity adsorption is greatly reduced by performing surface melting and then smoothing the surface.

  From the above results, the inner surface of the opening of the ring member made of fluororesin (PTFE) is subjected to surface melting processing at 340 ° C. to 380 ° C. (Ra = 450 nm), and then the surface roughness Ra is set to 200 nm or less. It has been found that surface polishing is appropriate.

(Example 2)
PTFE support pan 2 and PTFE ring member 3 (surface-melted at 340 ° C. to 380 ° C. (Ra = 450 nm) and further polished (Ra = 200 nm)) matched to a SiC substrate having a diameter of 100 mm A recovery jig 1 (see FIG. 1) provided with The ring member 3 is screwed into the support plate 2 so that the ring member 3 and the SiC substrate are brought into close contact with each other. Even if the recovery liquid is injected into the opening 34 of the ring member 3, the recovery liquid remains in the opening 34, and the SiC substrate Do not wrap around the periphery or back.

  In the opening 34 of the ring member 3 (on the SiC substrate), a recovered solution (hydrofluoric acid + hydrochloric acid + hydrogen peroxide solution + water mixed solution (hydrofluoric acid approximately 8%, hydrochloric acid approximately 4%, hydrogen peroxide solution approximately 7%) )) Was injected in 5 mL, stirred so that the recovered solution was evenly distributed, and allowed to stand for 5 minutes. Thereafter, the recovery jig 1 is tilted and the recovery liquid is taken out, and measurement of metal impurities (Na, Mg, Al, Ca, Ti, Cr, Fe, Ni, Cu, Zn, Mo, Sn, W) is performed by ICP-MS. went. The measurement results are shown in FIG. In FIG. 5, the result of E (chemical solution blank) indicates the amount of metal impurities originally present in the mixed solution used for elution of metal impurities. Therefore, the value obtained by subtracting the result of E from the result of D indicates the amount of metal impurities eluted from the SiC substrate into the mixed solution.

(Comparative example of Example 2)
A recovery jig 4 (see FIG. 11) provided with a PTFE support tray 5 and a PTFE ring member 6 (cutting only (Ra = 1200 nm)) matched to a 100 mm diameter SiC substrate was prepared. The recovery jig 4 is different from the recovery jig 1 of FIG. 1 in that the inner surface of the opening 61 of the ring member 6 is only cut, and the rest is the same as the recovery jig 1. The ring member 6 is screwed into the support plate 5 so that the ring member 6 and the SiC substrate are brought into close contact with each other. Do not wrap around the periphery or back.

  5 mL of collected liquid (hydrofluoric acid + hydrochloric acid + hydrogen peroxide solution + water mixed solution (hydrofluoric acid approximately 8%, hydrochloric acid approximately 4%, hydrogen peroxide solution approximately 7%)) in the opening 61 (on the SiC substrate) The mixture was poured and stirred so that the recovered solution was evenly distributed, and allowed to stand for 5 minutes. Thereafter, the recovery jig 4 is tilted to extract the recovered liquid, and the measurement of metal impurities (Na, Mg, Al, Ca, Ti, Cr, Fe, Ni, Cu, Zn, Mo, Sn, W) is performed by ICP-MS. went. The measurement results are shown in FIG. In FIG. 6, the result of E (chemical blank) shows the amount of metal impurities originally present in the mixed solution used for elution of metal impurities. Therefore, the value obtained by subtracting the result of E from the result of A indicates the amount of metal impurities eluted from the SiC substrate into the mixed solution.

  Comparing the results of FIG. 5 and FIG. 6, the amount of metal impurities in the result of FIG. 5 is smaller than the result of FIG. This is because metal impurities are eluted from the ring member (the inner surface of the opening) and the ring member is removed when a metal impurity recovery operation is performed with a recovery jig using a ring member having a large surface roughness only by cutting (Ra = 1200 nm). This is because the state is not always stable due to the influence of adsorption of metal impurities (FIG. 6). On the other hand, when a metal impurity recovery operation is performed with a recovery jig using a ring member subjected to surface melting processing + surface polishing (Ra = 200 nm), elution of metal impurities from the ring member and adsorption of metal impurities to the ring member There is little influence, the state is stable, and highly accurate analysis is possible (FIG. 5).

(Example 3)
A recovery jig 1 shown in FIG. 1 was prepared in accordance with a 200 mm diameter silicon substrate. 20 mL of a recovery liquid (hydrofluoric acid + hydrogen peroxide solution + water mixed solution (hydrofluoric acid approximately 2%, hydrogen peroxide solution approximately 5%)) is injected into the opening 34 of the ring member 3 (on the silicon substrate), The recovered liquid was stirred so that it was evenly distributed, and allowed to stand for 5 minutes. Thereafter, the collection jig 1 is tilted to take out the collected liquid, and after measuring the volume of the collected liquid, the metal impurities (Na, Mg, Al, Ca, Ti, Cr, Fe, Ni, etc.) in the collected liquid are measured by ICP-MS. Cu, Zn, Mo, Sn, W) were measured. The recovery rate calculated from the injection amount of the recovered liquid and the recovery rate is shown in Table 1 ("Surface Melting + Surface Polishing" / "Surface" column in Table 1), and the metal impurity measurement results by ICP-MS are shown in FIG.

Example 4
A recovery jig 1 shown in FIG. 1 was prepared in accordance with a 200 mm diameter silicon substrate. Etching solution (hydrofluoric acid + nitric acid + hydrochloric acid + water mixed solution (hydrofluoric acid approximately 2%, nitric acid approximately 25%, hydrochloric acid approximately 4%) as a recovery solution in the opening 34 of the ring member 3 (on the silicon substrate)) 20 mL was injected, stirred so that the etching solution was evenly distributed, and allowed to stand for 5 minutes. Thereafter, the recovery jig 1 is tilted to take out the etching solution, and after measuring the amount of the etching solution, metal impurities (Na, Mg, Al, Ca, Ti, Cr, Fe, Ni, etc.) in the etching solution are measured by ICP-MS. Cu, Zn, Mo, Sn, W) were measured. The recovery rate calculated from the injection amount and the recovery amount of the etching solution is shown in Table 1 above (in the column of “Surface Melting + Surface Polishing” / “Near Surface” in Table 1), and the metal impurity measurement result by ICP-MS is shown in FIG. Show.

(Comparative example of Example 3)
A recovery jig 4 shown in FIG. 11 was prepared in accordance with a 200 mm diameter silicon substrate. 20 mL of a recovery liquid (hydrofluoric acid + hydrogen peroxide solution + water mixed solution (hydrofluoric acid approximately 2%, hydrogen peroxide solution approximately 5%)) is injected into the opening 61 of the ring member 6 (on the silicon substrate), The recovered liquid was stirred so that it was evenly distributed, and allowed to stand for 5 minutes. Thereafter, the collection jig 4 is tilted to take out the collected liquid, and after measuring the volume of the collected liquid, the metal impurities (Na, Mg, Al, Ca, Ti, Cr, Fe, Ni, etc.) in the collected liquid are measured by ICP-MS. Cu, Zn, Mo, Sn, W) were measured. The recovery rate calculated from the injected amount of recovered liquid and the recovery rate is shown in Table 1 above (column of “cutting only” / “surface” in Table 1), and the metal impurity measurement results by ICP-MS are shown in FIG.

(Comparative example of Example 4)
A recovery jig 4 shown in FIG. 11 was prepared in accordance with a 200 mm diameter silicon substrate. Etching solution (hydrofluoric acid + nitric acid + hydrochloric acid + water mixed solution (hydrofluoric acid approximately 2%, nitric acid approximately 25%, hydrochloric acid approximately 4%)) as a recovery liquid in the opening 61 of the ring member 6 (on the silicon substrate) 20 mL was injected, stirred so that the etching solution was evenly distributed, and allowed to stand for 5 minutes. Thereafter, the recovery jig 4 is tilted to take out the etching solution, and after measuring the amount of the etching solution, metal impurities (Na, Mg, Al, Ca, Ti, Cr, Fe, Ni, etc.) in the etching solution are measured by ICP-MS. Cu, Zn, Mo, Sn, W) were measured. The recovery rate calculated from the injection amount and the recovery amount of the etching solution is shown in Table 1 above (column of “cutting only” / “near the surface” in Table 1), and the metal impurity measurement result by ICP-MS is shown in FIG.

  7 to 10, the result of E (chemical solution blank) indicates the amount of metal impurities originally present in the mixed solution used for elution of metal impurities. Therefore, the value obtained by subtracting the result of E from the result of D or A indicates the amount of metal impurities eluted from the silicon substrate into the mixed solution.

  From a comparison between Examples 3 and 4 (FIGS. 7 and 8) and comparative examples (FIGS. 9 and 10), recovery treatment using a ring member having a large surface roughness only by cutting (Ra = 1200 nm). When metal tools are used to collect metal impurities, there is an effect of elution of metal impurities from the ring member and adsorption of metal impurities to the ring member. Compared to the case of using a ring member with surface melting and surface polishing, metal impurities The amount of recovered is increasing. That is, it can be seen that the state is not always stable when a ring member only for cutting is used. Further, as shown in Table 1, it can be seen that when a ring member only for cutting is used, the recovery rate decreases because the recovery liquid remains in the liquid contact portion (opening portion inner surface) of the ring member and the semiconductor substrate.

  On the other hand, when a metal impurity recovery operation is performed with a recovery jig using a ring member subjected to surface melting processing + surface polishing (Ra = 200 nm), elution of metal impurities from the ring member and adsorption of metal impurities to the ring member There is little influence and the state is stable. Further, as shown in Table 1, when a ring member of surface melting processing + surface polishing is used, no recovery liquid remains in the liquid contact portion (inner surface of the opening) between the ring member and the semiconductor substrate, and the recovery rate is 100. It turns out that it improves to near%. As a result, highly accurate analysis is possible.

  Further, comparing the results of FIG. 7 and FIG. 8, the result of FIG. 8 has a larger amount of metal impurities than the result of FIG. From this, it can be seen that by using a mixed solution of hydrofluoric acid + nitric acid + hydrochloric acid + water as the recovery liquid, not only the substrate surface but also metal impurities in the substrate near the surface can be recovered and analyzed. On the other hand, it can be said that by using a mixed solution of hydrofluoric acid + hydrogen peroxide water + water as the recovery liquid, it is possible to recover and analyze metal impurities only on the substrate surface.

  As described above, in the present embodiment, surface melt processing is performed at 340 ° C. to 380 ° C. for the liquid contact portion of the ring member, and surface polishing is performed so that the surface roughness is 200 nm or less. Since the metal member is recovered using the ring member, elution and adsorption of the metal impurity between the ring member and the recovered liquid can be suppressed, and the metal impurity on the substrate surface can be accurately recovered and analyzed. In addition, no recovery liquid remains in the liquid contact portion between the ring member and the semiconductor substrate, and the recovery rate of the recovery liquid (metal impurities) can be improved. Further, metal impurities can be collected and analyzed for each of a substrate having a hydrophilic surface (SiC substrate) and a substrate having a hydrophobic surface (silicon substrate).

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope. For example, in the above-described embodiment, an example in which a fluororesin (PTFE) recovery jig is used has been described. However, a metal impurity recovery operation may be performed using another resin recovery jig. Even in this case, the recovery accuracy of metal impurities on the surface of the substrate can be improved by subjecting the liquid contact portion of the recovery jig to surface melting processing and surface polishing. When another resin recovery jig is used, surface melting processing (heating temperature) and surface polishing according to the characteristics of the resin may be performed.

  Moreover, although the said embodiment demonstrated the example using the collection | recovery jig | tool provided with the support plate and the ring member, if it has the liquid-contacting part which collection | recovery liquid contacts, the collection | recovery jig | tool of another structure ( For example, the metal impurities may be collected using the support container described in Patent Documents 1 and 2 above. Even in this case, it is possible to improve the recovery accuracy of the metal impurities on the surface of the substrate by subjecting the wetted part to surface melting and surface polishing.

  Moreover, although the said embodiment demonstrated the example which applied this invention to the metal impurity analysis of a SiC substrate and a silicon substrate, you may apply this invention to the metal impurity analysis of another semiconductor substrate.

DESCRIPTION OF SYMBOLS 1 Recovery jig | tool 2 Supporting plate 3 Ring member 34 Opening part

Claims (12)

A method of manufacturing a recovery instrument having a liquid contact portion that is used when recovering metal impurities present on the surface of a semiconductor substrate and that contacts the recovery liquid supplied to the surface during the recovery,
A preparation step of preparing a resin molded product molded into a shape having the liquid contact part;
A melting step of melting the surface of the wetted part in the molded product;
A polishing step of performing surface polishing of the wetted part after performing the melting step;
The manufacturing method of the collection | recovery instrument characterized by including.   The collection device is arranged on the surface side of the semiconductor substrate at the time of collection, and has a ring-shaped opening as the liquid contact portion that exposes a specific part of the surface of the semiconductor substrate at the time of the arrangement, The method for manufacturing a recovery instrument according to claim 1, wherein the recovery liquid is injected into the opening.   The method for manufacturing a recovery tool according to claim 1 or 2, wherein in the preparation step, the molded product of a fluororesin is prepared.   The method for producing a recovery instrument according to claim 3, wherein the type of the fluororesin is polytetrafluoroethylene.   5. The method for manufacturing a recovery tool according to claim 3, wherein in the melting step, surface melting processing of the wetted part is performed at 340 ° C. to 380 ° C. 5.   In the said grinding | polishing process, the surface grinding | polishing of the said liquid contact part is performed so that surface roughness Ra may be 200 nm or less, The manufacturing method of the collection | recovery instrument of any one of Claims 3-5 characterized by the above-mentioned.   Using the recovery tool obtained by the manufacturing method according to any one of claims 1 to 6, recovering metal impurities present on the surface by supplying a recovery liquid to the surface of the semiconductor substrate. A method for recovering metal impurities. The collection device is disposed on the surface side of the semiconductor substrate, and has a ring-shaped opening as the liquid contact portion that exposes a specific part of the surface of the semiconductor substrate during the arrangement,
Injecting the recovery liquid into the opening in a state in which the semiconductor substrate is sandwiched and supported by the recovery tool and a back-side support member having a flat support surface that supports the back surface of the semiconductor substrate. The method for recovering metal impurities according to claim 7.   9. The method for recovering metal impurities according to claim 7, wherein the semiconductor substrate is a silicon carbide substrate.   9. The method for recovering metal impurities according to claim 7, wherein the semiconductor substrate is a silicon substrate.   11. The recovered liquid is a mixed aqueous solution of hydrofluoric acid and hydrogen peroxide solution, a mixed aqueous solution of hydrofluoric acid, hydrochloric acid and hydrogen peroxide solution, or a mixed aqueous solution of hydrofluoric acid, nitric acid and hydrochloric acid. The method for recovering metal impurities according to any one of the above.   A metal impurity analysis method, comprising: measuring the amount of metal impurities in the recovered liquid after performing the recovery method according to any one of claims 7 to 11.

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