JP3345121B2 - Method and apparatus for analyzing trace components of solid sample - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for analyzing ultra-trace impurities in materials for semiconductor industry. In particular, the present invention relates to a method for analyzing ultra-trace impurities in a solid material such as quartz glass or silicon by a high-frequency inductively coupled plasma mass spectrometer (hereinafter referred to as ICP-MS) capable of high-sensitivity analysis, and an analyzer thereof.

[0002]

2. Description of the Related Art In recent years, with the progress of the semiconductor industry, the purity of semiconductor industrial materials has been increased, and the amount of impurities contained in the semiconductor industrial materials has been required to be of the order of ppt. For this reason, an apparatus capable of analyzing a ppt order has been used as an apparatus for analyzing the semiconductor industrial material. However, there are many sources of impurities such as alkali, iron, and copper that the semiconductor device dislikes most in the analysis room in which the analysis device is placed, and impurities generated therefrom contaminate the analysis sample. Generally, for example, T
HE TRC NEWS No. 40 Jul. 199
2, pages 27-31 and "Bunseki", February 1992
Cleanrooms and clean laboratories as described on pages 110-118 have been described.

However, as described in the above-mentioned literature, the above-mentioned clean room and clean laboratory require enormous equipment and operation costs, and in addition, the analysis of products for the semiconductor industry. Since highly corrosive hydrofluoric acid and nitric acid are used as reagents, the air circulating through the clean room and clean laboratory cannot be reused and is discarded in large quantities by local exhaust equipment such as a draft. Must be
The cost of removing the exhaust was expensive.

Therefore, a glow discharge mass spectrometer (GDM)
S) or direct vaporization of solid sample by laser vaporizer
Attention has been paid to a method of directly analyzing a solid sample, such as analysis by CP-MS. Indeed, in the analysis device, since the analysis sample is hermetically installed in the sample chamber and contamination from the environment is limited to the sample surface layer, if the analysis is performed while the surface layer is volatilized, the analysis of the solid bulk will be performed soon. Therefore, there is an advantage that a clean room facility is not required, and that no toxic or corrosive reagent is used. However,
In the analysis by these analyzers, a very small area, for example, 1
It requires a standard sample containing a known amount of an additional component in the order of ppb or ppt, and it is difficult to obtain the standard sample, and it is difficult to procure a standard sample having a trace concentration required for drawing a calibration curve. There are drawbacks such as the necessity of always paying attention to the uniformity of the standard sample.

[0005]

In view of these circumstances, the present inventors have studied means for performing ultra-sensitive quantitative analysis of solid samples without a clean room or a clean laboratory. When an ICP-MS is used as an apparatus, a sample solution or the like to be supplied to the analyzer is simply injected through a thin tube, and the entire analyzer is cleaned.
It has been concluded that if this ICP-MS is improved because it does not need to be installed in a room, high-sensitivity analysis can be performed without the clean room or clean laboratory. However, even when ICP-MS is used as an analyzer, since highly corrosive acids are often used for analyzing semiconductor materials, clean air is indispensable to eliminate harmful vapors of these acids. is there. Therefore, the present inventors continued further study on the treatment of this harmful vapor and the like,
A large amount of clean air is required to prepare solutions for analysis and to prepare standard solutions in order to exhaust harmful vapors such as generated acid.If the work area is isolated from the human body, the volume required for exhaust is reduced. It has been found that the separation can be performed and that the upper limit of the atmospheric concentration can be determined not only from consideration of safety to human body but also from consideration of corrosion resistance of facility equipment. A glove box is most suitable as an apparatus satisfying these requirements. If preparation for analysis is performed using this glove box, high-sensitivity analysis can be performed while maintaining the required cleanness. I found that I could do it.

However, since the ICP-MS needs to supply the measurement object to the ICP torch through a thin tube, the measurement object must be in a solution state. However, materials used in the semiconductor industry are solid samples as found in quartz glass, silicon wafers and the like. For this reason, it is necessary to remove trace impurities to be analyzed from these quartz glass, silicon wafers, and the like to form a solution.
The present inventors have already developed and proposed the solutionization of trace impurities such as quartz glass and silicon wafers, but this solution is prepared in a glove box with a high degree of cleanness to prepare a sample solution. The present inventors have found that ultra-trace impurities in a solid sample can be easily and highly sensitively analyzed even in a semi-clean room of class 10000 by introducing into ICP-MS and analyzing the present invention. It is completed.

An object of the present invention is to provide an analytical method and an analytical apparatus for easily and economically performing ultra-trace impurities contained in materials used in the semiconductor industry.

It is another object of the present invention to provide a method and an apparatus for analyzing the impurity content on a ppt order using ICP-MS.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a method of analyzing a trace component in a solid sample, which comprises decomposing and dissolving the solid sample, and evaporating and drying to prepare a sample solution from an impurity residue. The present invention relates to a method for analyzing a trace component of a solid sample, wherein the preparation is performed in a glove box having an increased cleanness, and an analyzer therefor.

The above "preparation for analysis" refers to an operation for preparing a sample solution by separating impurities in a solid sample and converting it into a solution, and for preparing a standard solution for a calibration curve essential for quantitative analysis and for preparing an internal standard. Means addition and the like.

The analyzer of the present invention comprises an ICP-MS, an analysis preparation glove box for preparing a sample solution and an oven. In the ICP-MS, a sample solution is atomized and supplied to the ICP torch 6 using an argon gas supplied from an argon gas storage container 9 as a medium, and ionized and detected as shown in FIG. This is an analyzer that converges the ionized element with an ion lens, guides the ionized element to a quadrupole mass analyzer 7, separates each ion by mass, counts the number of ions, and performs mass analysis. The ICP
The supply of the sample solution to the torch section 6 is performed through a sample introduction capillary 8, which protrudes above a sample table 13 shown in FIG. Further, the analysis preparation glove box,
A cleaning glove box 5 for washing a solid sample, a drying glove box 4 for loading a washed solid sample into a decomposition / drying container, and a preparation glove for preparing evaporated and dried impurities in a sample solution. It comprises a box 3 and a measuring solution supply glove box 2 for supplying a sample solution, a standard solution and the like to the ICP-MS, and they are connected in this order. In the cleaning glove box, the drying glove box, and the preparation glove box, air is supplied to the down flow through the HEPA filter 10 on the ceiling as shown in FIG. The duct 16 is connected to an outdoor gas cleaning tower (not shown). The cleaning glove box contains a faucet and a sink (not shown) of ultrapure water, and cleans an analysis sample with hydrofluoric acid to remove surface contaminants. The waste water washed in the cleaning glove box is discarded through the drain pipe 27. The ultrapure water pipe 18 is loop-shaped so that the flow does not accumulate even when the faucet is closed. The washed solid sample is transferred into the drying glove box 4 and placed in the inner container 23 of the disassembling / drying container 22 shown in FIG. The reservoir 25 of the outer container 24 is filled with a hydrofluoric acid solution.
The decomposition / drying container containing the solid sample is moved into an oven 15 with the door 17 shown in FIG. 7 opened, and heated, so that the solid sample is decomposed and dissolved. The inside of the oven is ventilated with clean air passing through an air filter 28. At the stage where the solid sample is completely dissolved and decomposed, water is passed through the cooling coil 26 shown in FIG. 8 to provide a temperature difference between the inner container 23 and the reservoir 25, and the decomposition solution in the inner container 23 is evaporated and dried. The evaporated and dried residue is transferred to the preparation glove box 3 via the drying glove box 4, and while monitoring the degree of cleanness, the container 22 is opened to dissolve the residue remaining in the inner container 23, and the sample solution is dissolved. Is prepared. The obtained sample solution is transferred to the measurement solution supply glove box 2 and the ICP-M opening there is opened.
The S is supplied to the ICP-MS through the sample introduction capillary 8. The measurement solution supply glove box 2 is cantilevered by the preparation glove box 3 and can be fitted into a sample table 13 of ICP-MS. Compressed air is filtered through the glove box 2 for measuring solution supply from the opposite side of the glove box 3 for preparation with a membrane filter (not shown) of about 0.01 μm, and the diffused air is diffused.
The liquid flows in the horizontal direction at the nozzle 14, and the inside of the glove box for supplying the measuring solution is maintained in a pressurized state. This prevents impurities from entering the container containing the sample solution from the inside of the preparation glove box, and keeps the measurement solution supply glove box more clean as compared with other boxes.

In the preparation glove box 3, an acid, pure water, a stock solution for a standard sample, a volumetric flask,
Glove box 4 for drying
The dried product is taken out from the inner container 23 of the decomposition / drying container 22 transferred from the container and dissolved using the acid or pure water to prepare a sample solution.

The drying glove box 4 is connected to an oven 15 through a door 17. Oven is electrical 2
1, the internal pressure is negative with respect to the drying glove box, so that the contamination in the oven is not transferred.

Each of the above glove boxes is provided with a lid 11 shown in FIGS. 2 to 4, so that instruments and containers can be put in with the lid opened. The cover shown in FIG.
The glove 12 is mounted, and the work in the box is performed using this glove.

The size of each glove box for washing, drying and preparation is sufficient if the inner volume is about 100 to 200 l. With this size, for example, in the case of a glove box with an internal volume of 100 l, the air volume is 10 m ³ / hour and the air volume is 1 hour / hour.
If the ventilation is performed 100 times, the cleanness of the class 100 can be easily maintained. Then, even if the degree of cleanliness is broken by opening the lid, if the above conditions are adopted, it is possible to recover to class 100 in 30 minutes.

[0016]

The analysis procedure of the present invention is as follows. That is, first, the lid 11 of the cleaning glove box 5 is opened, a solid sample and a hydrofluoric acid cleaning liquid are put therein, and air is supplied to make the cleaning degree 100 or less. Then, the solid sample is washed with a hydrofluoric acid washing solution. The washed solid sample is transferred to a dry glove box 4 having a cleanness of 100 or less.
Then, the solid sample is put into the inner container 23 of the decomposition / drying container 22, and the solid sample is put into an oven 15 through a door and heated to decompose and dissolve the solid sample. When the decomposition is completed, water is passed through the cooling coil 26 of the decomposition / drying container to cool the container.
A temperature difference is provided between the inner container 23 and the reservoir 25 of the decomposition / drying container to evaporate and dry the decomposition liquid. After drying, the inner container was taken out in the drying glove box, transferred to a preparation glove box 3 having a cleanness of 100 or less, dissolved in a dilute nitric acid solution prepared in advance, and a sample solution was prepared. Is prepared. At the same time, a calibration curve solution prepared from the standard stock solution is also prepared. Next, these measurement solutions were cleaned at a degree of cleanliness of 10.
The solution is transferred to a glove box 2 for supplying a measuring solution of 0 or less, and the IC is passed through a sample introduction capillary 8 of ICP-MS which is opened there.
The sample is introduced into the P-torch section 6 and quantitative analysis is performed. A calibration curve is created from the analysis results of the solution for the calibration curve, and the impurity material in the solid sample is quantified according to the calibration curve.

[0017]

EXAMPLES Each of the washing, drying and preparation shown in FIG.
A 100-liter glove box was supplied with air having an air volume of 10 m ³ / hour at a rate of 100 ventilations / hour for 30 minutes to reduce the cleanness to class 100 or less.

The lid 11 of the cleaning glove box 5 is opened, and 1.3 g of a glass lump sampled from a used high purity synthetic quartz glass wafer boat is placed. At this time, all chemicals and instruments such as hydrofluoric acid, nitric acid, standard stock solution, pipette, etc. to be used are also put in predetermined places in the box.
Since the cleanliness inside the box is deteriorated by this work, wait at least 30 minutes after closing the lid to reduce the cleanliness to class 10.
After confirming that the value was 0 or less, the glove 12 of the cleaning glove box was put into a hand to remove the synthetic quartz glass from the glove.
Wash repeatedly with 1.0% hydrofluoric acid solution to 1.0 g.
The washed synthetic quartz glass is transferred to the drying glove box 4 and the inner container 23 of the disassembly / drying container 22 in the box is dried.
Put in. Open the door of the disassembly / drying container in an oven adjacent to the glove box for drying, and place it at 105 ° C.
For 13 hours. As a result, the decomposition of the synthetic quartz glass is completed, and then water is passed through the pipe 20 shown in FIG.
The reservoir 25 is cooled. This cooling causes a temperature difference between the inner container 23 and the 38% hydrofluoric acid solution in the reservoir 25, and the decomposition solution evaporates to dryness. When the evaporation and drying were completed, the disassembling / drying container 22 was returned to the glove box 4 for drying, and after 30 minutes, it was confirmed that the cleanliness level was 100 or less. Then, the inner container was taken out and prepared. Transfer to glove box 3 and add 1 ml of 0.07 N dilute nitric acid to collect impurity residues to prepare a sample solution. The obtained sample solution and the solution for the S calibration curve in Table 2 prepared from the standard stock solution were transferred to the measurement solution supply glove box 2 and the ICP of ICP-MS was passed through the sample introduction capillary 8 opening there.
It is supplied to the torch 6 to prepare a calibration curve and to determine the Fe and N in the sample solution.
i, Cu analysis was performed. As a result of the analysis, the used high-purity synthetic quartz glass wafer boat was found to be 1 in this example.
It was found to contain 00 ppt Ni and 200 ppt Cu. Fe was 100 ppt or less.

Table 1 shows the reagents, samples, and the like used in the above analysis.
Table 2 shows the breakdown of the prepared sample solution and calibration solution.
Shown in

[0020]

[Table 1]

[0021]

[Table 2]

In order to investigate the lower limit of quantification of the method of the present invention separately from the above analysis, 20 parts of the 100 ppt standard curve solution shown in Table 2 were used.
Times, the standard deviation σ is 10 ppt
And the lower limit of quantification defined by 10σ is 10 for all four elements.
It was 0 ppt.

[0023]

According to the present invention, the use of four glove boxes having a small capacity of about 100 to 200 l can reduce impurities contained in quartz glass, silicon wafers and the like as semiconductor materials in the order of ppt. Can be accurately analyzed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of ICP-MS.

FIG. 2 is a front view of the device of the present invention.

FIG. 3 is a perspective view of a glove box of the device of the present invention.

FIG. 4 is a perspective view of a glove box for supplying a measurement solution.

FIG. 5 is a rear perspective view of the device of the present invention.

FIG. 6 is a perspective view of a glove.

FIG. 7 is a perspective view of an oven.

FIG. 8 is a cross-sectional view of a disassembly / drying container.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ICP-MS 2 Glove box for supply of measurement solution 3 Glove box for preparation 4 Glove box for drying 5 Glove box for washing 6 ICP torch 7 Quadrupole mass spectrometer 8 Sample introduction Narrow tube 9 Argon gas storage container 10 HEPA filter 11 Lid 12 Glove 13 Sample table 14 Diffuser 15 Oven 16 Exhaust duct 17 Door 18 Loop for ultrapure water 19 Compressed air supply pipe 20 For cooling water Supply / discharge pipe 21 Heating power supply 22 Decomposition / drying container 23 Inner container 24 Outer container 25 Liquid reservoir 26 Cooling coil 27 Drain pipe 28 Air filter (0.1 μm)

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-2-229428 (JP, A) JP-A-2-28533 (JP, A) JP-A 5-149847 (JP, A) JP-A-7- 39769 (JP, A) JP-A-6-174716 (JP, A) JP-A-60-91247 (JP, U) Yutaka Hiratsuka, "Clean Laboratory", Bunseki, Japan, Japan Society for Analytical Chemistry, 1992 February 5, Issue 2, p. 110-118 Kazuyoshi Sushida, "Analysis of Trace Elements in Semiconductor Materials, etc.", THE TR C NEWS, Japan, Toray Research Center Co., Ltd., July 1, 1992, Vol. 11, No. 3, p. 27-31 (58) Field surveyed (Int.Cl. ⁷ , DB name) G01N 1/00-1/44 G01N 27/62 H01J 49/04 G21F ⁷ /00-7/06 B25J 21/00-21 / 02 B01L 1/00-1/04 JICST file (JOIS)

Claims (9)

(57) [Claims] After decomposing and dissolving a solid sample, evaporation and drying
Analytical solution for dissolving the impurity residue obtained by
In the trace component analysis method to prepare and then analyze,
Glove box with increased cleanliness for the analysis preparation
And evaporate to dryness in an oven.
A small amount of solid sample characterized by being performed simultaneously in a solid container
Component analysis method . 2. The degree of cleanness in the glove box is determined.
2. The method according to claim 1, wherein the amount is less than or equal to 100 . 3. The method according to claim 1, wherein the solid sample is subjected to etching cleaning with an acid before decomposition and dissolution. 4. A high-frequency inductively coupled plasma mass spectrometer, an analysis preparation glove box and an oven, wherein the analysis preparation glove box is a cleaning glove box, a drying glove box, and a preparation glove box. A trace component analyzer for a solid sample, comprising a glove box and a glove box for supplying a measurement solution. 5. An oven connected to a drying glove box via a door, wherein the inside of the oven is maintained at a negative pressure with respect to the drying glove box. Item 5. An apparatus for analyzing a trace component of a solid sample according to Item 4 . 6. The preparation solution glove box according to claim 4, wherein the measurement solution supply glove box is cantilevered by the preparation glove box so as to be fitted into a sample table of the high frequency inductively coupled plasma mass spectrometer. Trace component analyzer for solid samples. 7. The solid sample trace component analyzer according to claim 4, wherein the sample introduction capillary of the high frequency inductively coupled plasma mass spectrometer is airtightly protruded from the measuring solution supply glove box. 8. The glove box for washing, the glove box for drying and the glove box for preparation of the glove box for analysis preparation, air flows from the ceiling filter to the down flow, while the glove for supplying the measuring solution. The apparatus according to claim 4, wherein compressed air flows in the box in a horizontal direction from the opposite side of the preparation glove box. 9. An apparatus according to claim 8 , wherein the inside of the glove box for supplying the measuring solution is in a pressurized state.