JP2011133368A - Container for sample treatment, and analysis method for impurities in sample using the container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a container for dissolving a sample surface layer part and dipping an analysis sample into dissolving liquid, and efficiently recovering dissolving liquid containing analysis impurities, and to provide an analysis method which uses the container. <P>SOLUTION: The container 1 for sample treatment includes fine projections 2, 3 on a container inner wall and a container bottom so that a solid sample does not adhere to the whole surface, namely, to the side surface in the container or to the bottom surface in the container and thereby allows uniform contact of the dissolving liquid with the sample surface. The container is also provided with a fine liquid reservoir 4 for efficiently recovering the dissolving liquid. It is preferable that a material of the container 1 for sample treatment be fluororesin and preferably, have a concentration below 1 ppb for each metal element in an elution test. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a container provided for quantitative analysis of impurities in a sample and an analysis method using the container.

  Quartz glass is currently used in various fields including the optical field and semiconductor manufacturing field because of its heat resistance and light transmittance. In particular, in the field of semiconductor manufacturing, it is used for CVD (Chemical Vapor Deposition) reaction vessels, quartz boats, washing vessels, washing tanks and the like because of its high purity and chemical resistance. Further, this quartz glass is also used as a crucible for pulling up a Si single crystal for solar cells.

  When there are many metal impurities in quartz glass, these impurities diffuse into the product and lower the yield. Therefore, when used in CVD reaction vessels, quartz boats, etc., quartz glass may be of high purity. Desirably, it is necessary to quantify the amount of impurities contained in the quartz glass.

  As a method of quantifying the amount of impurities contained in the quartz glass, a sample such as quartz glass is immersed in a container and an acid is dissolved to dissolve the sample, and a part of the quartz glass surface is dissolved. In general, the lysate is collected and analyzed.

  For example, Patent Document 1 discloses a sample melting jig and a method for analyzing impurities in an aluminum alloy thin film on a silicon substrate using the jig. In this method, one side of the silicon substrate is brought into close contact with the inner bottom of the container, and a U-shaped groove is provided on the outer peripheral side inside the container to collect the solution. This is quantified by atomic absorption. However, this method has a problem in that the solution flows around the back surface of the silicon substrate, resulting in a large error in analysis data.

  Further, as a method for analyzing the surface of a silicon wafer, Patent Document 2 discloses a method in which an analysis jig is vacuum-adsorbed on a silicon wafer. In this method, the analysis jig is adsorbed while the surface of the silicon wafer is smooth. However, when the surface starts to become rough, problems such as liquid leakage occur.

Japanese Patent Laid-Open No. 11-118684

Japanese Patent Laid-Open No. 08-005526

  The present invention provides a container capable of analyzing impurities contained in a sample with high sensitivity and an analysis method using the same, and is characterized by extremely low contamination from the container.

  The present invention relates to a sample processing container having minute protrusions on the inner wall of the container and the bottom of the container so that the sample does not adhere to the entire inner surface of the container or the bottom surface of the container.

  The container of the present invention has minute protrusions on the inner wall and the bottom of the container so that the sample does not adhere to the entire inner surface and bottom surface of the container. Is possible.

  The number and shape of minute protrusions on the inner wall and the bottom of the container are not particularly limited as long as the sample does not adhere to the entire inner surface and bottom surface of the container. From the point that the contact area with the solid sample is small and can be stably held, it is preferable that there are 1 to 4 minute protrusions on the inner surface of the container, and 3 to 8 minute protrusions on the bottom of the container. It is preferable.

  The protrusion distance of the protrusion on the inner wall of the container is preferably 0.5 to 3 mm, and the height of the protrusion on the bottom surface of the container is preferably 0.5 to 3 mm. It is preferable that the space | interval of protrusion parts is 2-5 cm.

  Moreover, in order to avoid metal elution and contamination from a container, it is necessary to manufacture with the acid-resistant resin from the container of this invention. Examples of the acid resistant resin include fluororesin and polypropylene. In view of the absence of acid elution of the plasticizer and flame retardant, a fluororesin is particularly preferable.

  Among fluororesins, polytetrafluoroethylene (200 to 260 ° C.), water absorption (0.01% 24 hr), acid resistance (super excellent: not affected even under severe conditions) PTFE), perfluoroalkoxyalkanes (PFA), perfluoroethylene propene copolymer (PFEP) are preferred.

  In addition, as for the material of the container of this invention, it is preferable that the density | concentration of all the metal elements is less than 1 ppb by the elution test after performing acid treatments, such as boiling in an acid solution previously. That is, a 25 wt% hydrofluoric acid aqueous solution and a 1 wt% nitric acid mixed solution are poured into a container, and after holding for 24 hours, the mixed solution is analyzed using an analysis method with a quantitative limit of 1 ppb. It is preferable that Group Ia elements such as Na, K and Rb, Group IIa elements such as Mg, Ca and Sr and transition metal elements such as Ti, Cr, Mn, Fe, Co, Ni and Cu are not detected.

  The size of the container is not particularly limited, but is preferably 6 to 10 cm in length, 6 to 10 cm in width, and 2 to 5 cm in height from the viewpoint of easy handling. Further, although there is no particular limitation on the internal shape, it is preferable that there is a gap that allows the solution to move up and down the quartz glass plate when holding the glass plate as the measurement sample. It is preferable that it is ˜9 cm and the depth is 1 to 4 cm because it is easy to handle.

  In the present invention, it is preferable to provide a small liquid reservoir for efficiently recovering the solution. The position of the liquid reservoir is not particularly limited, but is particularly preferably provided at the corner of the container because the solution can be most easily recovered.

Furthermore, in this invention, it is preferable to design the shape of a container bottom so that the amount of solution per unit area of quartz glass may be 0.1-0.3 mL / cm < ² >. This is because the analysis accuracy is improved by making the necessary amount of the solution to be used.

  Further, it is preferable to provide a container lid for preventing evaporation of the solution during long-time etching.

  The shape of the container lid is not particularly limited, but is preferably acid resistant and not easily broken. The material of the container lid is not particularly limited as long as it has the same properties as the material used for the container. However, transparent perfluoroalkoxyalkane (PFA), polytetrafluoroethylene perfluorodiode is used. A xol copolymer (PTFE / PDD) is preferred.

  Since the sample processing container of the present invention is made of an acid-resistant resin, there is very little contamination from the container, and the impurities in the net sample can be dissolved in the solution. It can be analyzed with high sensitivity.

It is the figure seen from diagonally upward of the sample processing container concerning this invention. It is the figure seen from diagonally upward when a quartz glass sample is inserted in the sample processing container concerning this invention. It is a center sectional view of the container implemented with the present invention. It is a top view of the container implemented by this invention. It is the Cu concentration in the quartz glass depth direction determined by the atomic absorption method.

  In the present invention, the size of the quartz glass sample to be quantitatively analyzed is large enough to be inserted into the container.

If there is no problem, a thin quartz glass plate having a side length of 20 to 100 mm and a thickness of 1 to 2 mm is preferable from the viewpoint of easy handling. Further, if the thickness is 1 to 2 mm, the diffusion of metal impurities proceeds from all directions, so that the metal impurity concentration can be measured with almost no error even when all the glass plates are immersed.

  For the diffusion of metal impurities into the quartz glass plate, the quartz glass plate is placed in a quartz glass bowl, a metal diffusion source such as metal powder is placed around the quartz glass plate, and an electric furnace having a quartz furnace core tube is provided. By inserting a quartz glass sagger in the furnace and holding it at an arbitrary temperature for an arbitrary time, the metal can be diffused inside.

  The solution used in the present invention may be hydrofluoric acid alone or a mixed solution of hydrofluoric acid and a strong acid such as nitric acid, hydrochloric acid or sulfuric acid. Usually, it is desirable to use a mixture of hydrofluoric acid and nitric acid that does not interfere with peaks during analysis. Here, the purity of the solution is 50% for ultra trace analysis, and the metal impurity concentration is less than 10 ppt (pg / g) (ICP / MS, partly GF-AAS) for hydrofluoric acid. Ultra high purity is preferable. Similarly, nitric acid is preferably ultra-pure as much as possible for ultra trace analysis (70%) and metal impurity concentration of less than 10 ppt (pg / g). The dilution water is preferably ultrapure water (RO membrane, mixed bed ion exchange resin twice, UF membrane, 0.1 μm membrane filter treated water) having a specific resistance of 18 MΩ · cm or more.

  When the surface of the sample is dissolved with the dissolution solution, it is important that the dissolution solution is not necessary and sufficient. This is because the analysis accuracy is increased by making the amount of the lysate necessary and sufficient. It is preferable that the height from the upper surface of the quartz glass plate to the dissolved liquid surface is 0.1 to 2 mm.

  Further, when the etching time is relatively short (2 minutes to 59 minutes), the evaporation of the solution can be ignored, but when the etching time is long (1 hour to 1 day), the evaporation of the solution cannot be ignored. It is preferable that a container lid is placed on the above-described container so that the container is almost sealed.

  After the etching with the solution is completed, the solution in which the impurities are dissolved is collected.

  In the present invention, flameless atomic absorption, ICP-AES (inductively coupled plasma emission spectrometry), ICP-MS (inductively coupled plasma mass spectrometry), and flame atomic absorption are suitable for quantitative analysis of impurities in quartz glass thin plate samples. used. Since there is no 1 ppb of impurity elution from the container, analysis is possible with a quantification limit of 1 ppb for each impurity.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated in detail, this invention is not limited to an Example at all.

  As a sample, an optically polished quartz glass thin plate of 50 mm × 50 mm × 1 mm was used. The sample was placed in a quartz glass bowl with a lid of 100 mm × 120 mm × 60 mm, and CuO powder was placed around the sample as a Cu diffusion source. The Cu diffusion source was not in direct contact with the sample, and the sample was placed against a quartz glass block.

  Into an electric furnace having a quartz furnace core tube having a diameter of 180 mm, a quartz glass sagger having a sample disposed therein was inserted and maintained at 1050 ° C. for 24 hours to diffuse copper into the sample.

  In a clean draft kept in class 100 in a class 1000 clean room, Teflon (registered) according to the present invention is in a state where the impurity elution with respect to a mixed solution of 25 wt% hydrofluoric acid-1 wt% nitric acid is 1 ppb or less. The sample was inserted into a container made of (trademark) (outside diameter 85 mm × 85 mm × 30 mm, inner hole shape 53 mm × 53 mm × depth 20 mm). As the lysis solution, a mixed acid of 25% hydrofluoric acid and 1% nitric acid was prepared using an ultra-trace analysis reagent and ultrapure water. This solution was dropped three times with a 2.4 mL fixed pipettor.

  The solution was poured from the upper surface of the sample to 0.3 mm above, and the entire sample was immersed. The etching time was changed to 2, 4, 8, 16, 32, 60, and 120 minutes. After etching for each set time, the solution was sucked from a small liquid reservoir with a fixed pipettor and poured into a 5 mL container. The container used was a cryovial (a cryopreservation tube), a main body PP (polypropylene), a lid PE (polyethylene), a radiation-sterilized, non-toxic, non-pyrogen commercial product so as not to contaminate impurities.

  Graphite furnace atomic absorption method was used for determination of Cu. FIG. 6 shows the Cu concentration in the depth direction of the quartz glass determined by the atomic absorption method. An error function was used to connect the plots. With the container and analysis method of the present invention, Cu atoms diffused in the quartz glass depth direction could be accurately quantified to the limit of 1 ppb.

  It is possible to analyze the concentration of trace metals in quartz glass down to the level of 1 ppb. In addition, it can be applied to the analysis of the concentration of trace metals in the silicon wafer in the depth direction by the same method.

1. Sample processing container 2. A small protrusion on the bottom of the container. 3. Small protrusions on the inner surface of the container 4. A small reservoir for collecting the solution. Quartz glass sample

Claims (7)

A sample processing container used for measuring the amount of impurities in a sample by dissolving the sample, and the inner wall of the container and the inner surface of the container so that the sample does not adhere to the inner surface of the container or the bottom surface of the container. A sample processing container having a minute protrusion on the container bottom. The sample processing container according to claim 1, further comprising at least one minute liquid reservoir for recovering a solution in which a surface component of the sample is dissolved. 3. The sample processing container according to claim 1, wherein the sample processing container is made of a high-purity fluororesin. The internal shape designed so that the amount of solution per unit area of quartz glass to be etched is 0.1 to 0.3 mL / cm ^2. Sample processing container. 5. The sample processing container according to claim 1, wherein the content of the group Ia element, the group IIa element, and the transition metal element is 1 ppb or less. 6. The sample processing container according to claim 1, further comprising a container lid for preventing evaporation of the solution during etching. A method for analyzing trace impurities in a sample by flameless atomic absorption spectrometry using the sample processing container according to claim 1.

Images