JP3179175B2 - Analysis pretreatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pretreatment method for analyzing an extremely small amount of impurities.

[0002]

2. Description of the Related Art As a method for concentrating a substance to be analyzed in a liquid as a pretreatment for analysis, a method of evaporating a liquid on an evaporating dish to dryness is generally used. In this case, since there is no suitable method for quantifying the target substance widely dried on the concave surface (evaporating dish surface) with high sensitivity, the dried substance is usually re-dissolved with a small amount of a dissolving solution, and analyzed for a liquid sample. The analysis is performed by an instrument such as an ICP mass spectrometer or a liquid chromatograph.

[0003] Recently, a total reflection X-ray fluorescence analysis method has been developed for analyzing a local area of a flat surface with high sensitivity. In this analysis method, when a liquid sample is to be analyzed, the droplet is dropped on a high-purity quartz glass surface or a high-purity silicon single-crystal wafer surface, and evaporated to dryness,
A pre-treatment for concentrating in a local area on a plane is performed.

[0004] On the other hand, as a pretreatment method for concentrating metal impurities on the surface of a silicon wafer or the like and collecting it in a small amount (ie, about 100 µl) of liquid, the wafer or the like is subjected to HF vapor in a gas phase decomposition apparatus. After that, the acid droplet is held on a fluororesin holder by surface tension, and the droplet is spirally scanned from the center to the periphery of the wafer by a scanning device, and then the holder is moved to a saucer. There is known a method of recovering a liquid that has collected metal impurities.

[0005]

In the total reflection X-ray fluorescence spectrometry, the dried sample portion of the droplet sample must be located just below the center of the window of the X-ray fluorescence detector in a portion where the dose of X-ray is uniform. Must. In an ordinary apparatus, the impurity dry region on the flat substrate surface portion is at most within 5 to 6 mmφ, and its position (address) must be accurately recognized.

Radioactive isotope ^{59 in} ultra-high purity HF solution
Fe is dissolved about 1 ppb, when dropping the liquid of 20μ l on a silicon wafer substrate was sparse hydrated by blowing steam pre HF, the substrate may droplet diameter 4 to 5 mm. Let it dry slowly and use an autoradiograph
Examination of the dry state of ⁵⁹ Fe reveals that ⁵⁹ Fe is present up to about the same size as the diameter of the droplet before the onset of dryness.

[0007] In the case of such trace impurities, since the evaporated liquid itself has a high purity, no trace of drying on the substrate can be seen. In addition, the droplet may move considerably in the initial stage of the evaporation of the droplet, and the dried portion is not always the same as the position where the liquid is dropped. This is not preferable for measurement. If it is not possible to accurately determine the dry position, it is desirable that the droplet on the substrate be as small as possible. For example, if the diameter of the droplet is 3 mm, the amount of the droplet is about 5 μl. Since the detection sensitivity of the analyzer does not change, reducing the amount of the dropped liquid decreases the analysis sensitivity of the liquid.

Accordingly, a first object of the present invention is to dry an analysis sample solution of several hundred μl accurately at a designated position on a dry substrate with a small area of 2 to 3 mmφ or less. It is to provide a treatment method prior to analysis possible. In the semiconductor field also impurities of the silicon wafer surface were transferred to the droplets, serves a method of analyzing the solution is important, in the present invention, treatment before analysis with a transition operation of its
To provide a sense how a second object.

[0009]

According to the present invention, substantially vertical
Lower end that is held directly and can hold the analysis sample solution
A thin tube having a portion, and surrounding the lower end of the thin tube.
End that can prevent the analysis sample solution from scattering
Using an instrument comprising an outer tube with
Aspirate the analysis sample solution in advance, and fit the end of the capillary
Proximity on hydrophobic analysis sample liquid drying plate heated to the temperature of
And transfer the sample liquid from the capillary to a predetermined position on the sample liquid drying plate.
The sample discharged at that time
The liquid is discharged so that the liquid contacts the lower end of the capillary, and at the same time,
The evaporation of the sample liquid droplets discharged onto the sample liquid drying plate is continued.
By connecting the sample liquid continuously,
Concentrate the sample solution to dryness without spreading it beyond its diameter.
A method is provided for pre-analytical processing characterized by consolidating .

The thin tube, outer tube, etc. are made of a hydrophobic synthetic resin,
For example, polytetrafluoroethylene (PTFE), tetrafluoroethylene perfluoroalkoxyethylene (PF)
A), preferably made of a fluororesin such as Teflon AF, and a second outer tube may be provided further outside the outer tube.

[0011]

Examples of the drying plate for the sample liquid for hydrophobic analysis include a silicon wafer immersed in HF, a silicon wafer heated and ultrasonically treated with an aqueous solution of a strong organic alkali and a surfactant, and a silicon wafer coated with Teflon AF (trade name). Is useful.

[0013] As before Symbol fixtures, the use of instruments second outer tube so as to surround it further outside of the outer tube is provided also in this case, simultaneously with the evacuation of the evaporation material, The atmosphere can be supplied from the second outer tube.

[0014] As an apparatus for carrying out the pretreatment method the onset Ming analysis, the analysis pretreatment instrument arm for holding the pre-analysis treatment instrument, the mechanism for moving the arm, the dry analytical sample liquid A drying plate for performing, a driving mechanism for performing position movement of the drying plate such that an end of the analytical pretreatment instrument held by the arm is set at a predetermined position of the drying plate, and a holding mechanism for holding the arm. has been heated mechanism provided on the opposite side of the pre-analysis process the drying plate in correspondence with the end portion of the instrument can be used is not that minute析前processing apparatus includes a.

According to the present invention, as a method of collecting impurities adhering to a hydrophobic analysis surface of a silicon wafer or the like and performing a pretreatment for analysis , the method of holding the liquid substantially vertically and holding the liquid
A thin tube having a lower end capable of
We can prevent splash of liquid provided to surround
Using a device having an outer tube with an end.
Aspirate liquid to dissolve and collect impurities on the analytical surface in advance in the tube
Let the end of the outer tube be close to the hydrophobic analysis surface
So that the instrument is positioned and discharge liquid from the capillary.
To form a droplet on the hydrophobic analysis surface in the outer tube.
If necessary, make sure that the inside of the outer tube is slightly
While the pressure is reduced, the device is moved to analyze the droplets for hydrophobicity.
By scanning the surface, impurities on the hydrophobic analysis surface can be removed.
Collected in droplets, and then all of the droplets are combined with the sample liquid for analysis.
And aspirate into the capillary, and heat the end of the capillary to a predetermined temperature.
Close to the dried hydrophobic sample liquid drying plate
The sample liquid is gradually connected from the tube to a predetermined position on the sample liquid drying plate.
The sample liquid discharged at that time is
Discharge so that it contacts the lower end, and at the same time dry the sample liquid
Continue evaporation of sample liquid droplets discharged on the plate
As a result, the sample liquid that is continuously discharged is wider than a specified diameter.
Concentrate the sample solution to dryness without removing it
An analysis pre-processing method is provided.

[0016] In the pretreatment method described above, as a vessel device, it is possible to use an instrument the second outer tube so as to surround it further outside of the outer tube is provided. Further, the movement of the pretreatment device for scanning the droplets can be performed by a robot mechanism.

[0017]

[0018]

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in more detail hereinafter with reference to an embodiment shown in the accompanying drawings.

EXAMPLE 1 In FIG. 1 which shows an analytical pretreatment device having a double tube structure used in the present invention , the analytical pretreatment device is basically composed of a cylindrical support 1 made of PTFE, A thin tube 2 made of PFA extending through the center of the support 1;
An elongated hole 6 formed in the support 1 substantially in parallel with a transparent fluororesin made of Teflon AF (trade name) provided at the lower end of the support 1 so as to surround the tip of the thin tube 2. Tube 5 (inner diameter: about 10 mm).

The distal end 3 of the thin tube 2 is narrowed down to an inner diameter of about 0.1 mm, and the distal end 4 of the outer tube 5 is located on substantially the same plane as the distal end 3. At the upper end of the long hole 6, a protruding tube portion 7 for connecting an exhaust tube is formed. The outer tube 5 may be a PFA tube whose thickness is made sufficiently thin so that the distal end portion 3 of the thin tube 2 can be seen.

A description will be given of a method of using the above-described analytical pretreatment device when concentrating an analytical sample solution and forming a dried portion having a diameter of 2 mm or less at a specific position on an analytical sample solution drying plate.
In addition, in order to confirm by the RI tracer method how much the analysis target in the analysis sample solution migrated to the dried portion, a 0.01% Fe Fe ppb solution labeled with ⁵⁹ Fe was prepared. Further, a silicon wafer whose surface was hydrophobized by immersion in HF was used as an analytical sample liquid drying plate.

FIG. 2 shows a droplet drying apparatus used for drying the analysis sample liquid. That is, the drying wafer 8 is accurately positioned and held on the quartz glass plate 10 by the knob 11. The quartz glass plate 10 is horizontally movable by an XY stage 9, and is fixed at a designated position. Below the quartz glass plate 10, a heating halogen lamp
12 are arranged. The halogen lamp 12 is housed in a quartz container 13 whose inside can be ventilated and cooled.

Above the quartz glass plate 10 is disposed the above-mentioned analytical pretreatment instrument used in the present invention. In the pretreatment device, the arm 14 is connected to the support 1,
The position can be freely adjusted by vertical movement, rotation, slide, and the like. Further, a dispenser 15 is connected to the thin tube 2, and an exhaust mechanism 16 such as a water flow pump using ultrapure water is connected to the protruding tube 7.

First, by the operation of the arm 14, the distal end portion 3 of the thin tube 2 of the pretreatment device is moved to a predetermined washing tank, where a chemical solution treatment is performed if necessary, followed by washing with water. Next, only the tip portion 3 of the thin tube 2 enters the sample tank, and the dispenser 15 is operated in reverse to suck 200 μl of the sample solution into the thin tube 2 accurately. Further, the stage 9 is operated to set the wafer 8 at a specified position, and the wafer 8 is
Heat to a temperature of 95 ° C.

Further, the pretreatment device is moved by operating the arm 14 so that the tip portion 3 of the capillary 2 into which the sample solution has been sucked is positioned at the designated position on the wafer 8. Here, when the distal end portion 3 of the thin tube 2 descends to a certain interval with respect to the wafer 8, the operation of the exhaust mechanism 16 starts,
The sample liquid is gradually discharged by operating the dispenser, and small droplets are formed between the tip 3 of the thin tube 2 and the wafer 8. Note that the XY stage 9 is adjusted in advance so that the position of the small droplet becomes the designated position. The position accuracy of the droplet is determined by the accuracy of the XY stage 9, but usually,
The position accuracy is about ± 0.1 mm, and the position accuracy required for the analyzer can be sufficiently obtained. The drying plate was placed at a position where the drying plate was uniformly heated on the heating device, and the support 1, that is, the tip 3 of the thin tube 2
A structure in which the Y stage 9 moves to a designated position on the drying plate may be used.

The diameter of the droplet depends on the discharge speed of the liquid and the evaporation rate of the liquid by heating. Therefore, by appropriately adjusting the discharge speed and the lamp voltage of the lamp 12, the discharge speed and the evaporation speed reach equilibrium, and the diameter of the liquid becomes substantially constant. For example, when the discharge speed was 10 μl / min at the above surface temperature (90 to 95 ° C.), the diameter of the droplet was approximately 2 mm, and the droplet was dried as it was.

[0027] As in the prior art, if it is dried with one drop, 1
Unless the sample solution has a volume of about 2 μl, the dried area cannot be reduced to 2 mmφ. On the other hand, according to the present invention, it is understood that the sample liquid having a much larger liquid volume than the conventional one can be dried in a small area at a predetermined position on the drying plate.

In the above, the amount of radioactivity in the dried portion was 97% of the initial 200 μl sample solution, and it is considered that 3% was scattered. This recovery is well tolerated when analyzing ordinary trace impurities. Therefore, if contamination from the apparatus and the environment can be prevented, the sensitivity of the analysis can be greatly increased, and the pretreatment method of the present invention using the pretreatment instrument is an extremely effective method.

[0029] For comparison, in the pretreatment instrument performs exactly the same experiments by removing the outer tube 5, was subjected to entire surface of the autoradiograph of the wafer 8, ⁵⁹ Fe is scattered rather wide range And found that it was contaminated. Further, the same experiment was performed again with the outer tube 5 attached, but no contamination of ⁵⁹ Fe was observed in the wafer portion outside the outer tube 5. If a pretreatment device having a double-tube structure is used in the present invention , a dried portion for analysis can be formed at a plurality of addresses on the drying plate, and efficient analysis can be performed.

Embodiment 2 FIG. 3 shows a pretreatment device having a triple structure which can be used in the present invention. In this pretreatment device, a thin tube 2, a long hole 6, and an outer tube 5
Is provided, and a second outer tube 17 is provided so as to further surround the outer tube 5. This second outer tube
The space between the outer tube 17 and the first outer tube 5 communicates with a long hole 16 penetrating a portion connecting the upper outer tubes to each other.
A projection tube 19 for connecting to a tube (not shown) for supplying the atmosphere is formed at the upper part of the projection. The lower end 18 of the second outer tube 17 is slightly shorter than the lower end of the first outer tube 5, and the lower end 3 of the thin tube 2 and the lower end of the outer tube 5 are connected to the second outer tube 5. The tube 17 projects outward from the lower end portion 18 of the tube 17. The second outer tube 17 is also made of a hydrophobic synthetic resin, and is formed integrally with the support 1, for example.

The pretreatment device having the triple tube structure shown in FIG. 3 was attached to the arm in the same manner as in FIG. 2, and an experiment was conducted in the same manner as in Example 1. In this case, at the same time as the evacuation from the long hole 6, high-purity dust-free nitrogen gas heated to about 80 ° C. was supplied through the long hole 16 while keeping the amount of exhaust gas balanced.

The droplet formed at the end 3 of the thin tube 2 was controlled to be smaller, and the dried region could be made 1 to 1.5 mmφ. The recovery rate in the dried part of ⁵⁹ Fe was 91%, and the scattering was slightly increased, but this method can be applied sufficiently when the requirement for the analytical value can be one digit. For ultra-trace analysis, general high-sensitivity analyzers have this level of accuracy.
In general, it can be put to practical use.

Embodiment 3 In the pretreatment device having a double tube structure shown in FIG. 1, since the outer tube 5 is hydrophobic, it is moved on a hydrophobic surface while holding an aqueous droplet at its end. Can be. This embodiment describes a method of forming an analysis sample droplet on a wafer surface while dissolving impurities attached thereto.

In order to examine how much impurities on the wafer surface can be trapped in the droplets, a tracer technique using a radioisotope was used as in Example 1. Cu attached to the silicon surface from a HF-based chemical solution in the presence of a reducing substance,
The collection rate by HF droplets following the gas phase decomposition method is very poor in recovery. Moreover, the recovery is poor in reproducibility. Therefore, in this embodiment, the droplet collecting of the thus ⁶⁴ recovery was difficult was deposited only on the mirror surface side of the silicon wafer Cu, tried in the processing method using the partial析前treating appliance.

As shown in FIG.
Is held horizontally, and the end of the outer tube 5 of the pretreatment tool shown in FIG. 1 is brought into contact with the surface of the wafer 20 so that the processing tool can be freely scanned in this state. The body 1 is held by an arm 22 of a predetermined robot mechanism.

First, by the operation of the arm 22, the tip 3 of the thin tube 2 is cleaned in the same manner as in the first embodiment.
Only, and dispenser 15 works in reverse to 100 ~
Aspirate 200 μl of liquid. In addition, as the above solution, a solution obtained by adding 3% of HF to a 1: 1 aqueous solution of nitric acid and water in order to dissolve ⁶⁴ Cu was used.

Further, the arm 22 is operated to move the pretreatment device to a predetermined analysis area on the wafer 20 so as to be in the state shown in FIG. Discharge the acid solution. In this case, the droplet does not protrude outside the outer tube 5 due to the surface tension. At the same time, the exhaust mechanism 16 communicating with the inside of the outer tube 5 is cut by the valve 23, and the separately connected dispenser 15 'is slightly sucked to slightly reduce the pressure inside the outer tube 5.

In this state, the droplets are scanned on the wafer 20 by scanning the pretreatment tool through the arm 22 by the robot mechanism. In this case, the wafer
The scanning of the droplets on 20 is performed in a so-called one-stroke stroke. Further, for example, impurities can be collected on half of the wafer by reciprocating scanning in a seven-curve method starting from parallel to the orientation flat.

By moving the droplet at a constant speed, the entire surface scan on the wafer was completed over 15 minutes. By comparison of the radioactivity measurements, 82% of the ⁶⁴ Cu on the wafer was trapped in the droplet. This is about twice the value obtained when only HF is simply scanned. In the present invention, even if the position of the support 1 is fixed and the dish container 21 is moved by a robot mechanism, the apparatus is relatively the same as the above-described apparatus.

Example 4 In order to further increase the recovery rate of ⁶⁴ Cu as compared with Example 3, it is necessary to increase the concentration of nitric acid to nearly 60% by weight. However, when HF is contained, when the liquid comes into contact with the reducing impurities, an oxidizing gas is generated, which changes the surface of the silicon holding the droplets into a hydrophilic property,
Since the altered surface captures the liquid, the amount of liquid droplets that can be collected is reduced.

Therefore, using the pretreatment device having a triple tube structure used in the second embodiment shown in FIG. 3 and using the same wafer as in the third embodiment, an aqueous solution of 55% nitric acid and 2% hydrofluoric acid was used. And the same scan was performed. As a result, the scan was completed without the droplet remaining on the wafer, and 93% of ⁶⁴ Cu on the wafer was trapped in the droplet by comparing the radioactivity measurements. Thus, the usefulness of the pretreatment device having the triple tube structure is understood.

Example 5 After the same scanning was performed using the wafer of Example 4, the dispenser 15 was immediately operated in reverse to suck all the droplets into the thin tube 2. The pretreatment device having the triple tube structure was replaced with the arm 14 on the XY stage of the first embodiment, and the droplets were dried at a designated position as in the first embodiment.
The droplets formed were about 2.5 mm in size, and the measured radioactivity after drying showed that 90% of the ⁶⁴ Cu on the wafer had been dried. From these results, it is understood that the use of only one pretreatment tool can concentrate the impurities on the wafer and dry the analysis sample to a small area at the designated position on the drying plate with sufficient accuracy. You.

[0043]

According to a separatory 析前 processing method of the present invention, the designated position of the analysis sample solution dried plate was concentrated analytical sample liquid, can be performed dryness diameter 2 to 3 mm, sufficient total Reflected fluorescent X
A sample for line analysis can be prepared. Further, by using a triple tube structure as a tool to be used , it is possible to dry in a smaller area. Even with such a surface analyzer, concentration that can obtain effective information becomes possible. Further, according to the present invention, it is possible to collect and concentrate impurities on the surface of the silicon wafer by using the same equipment as the above-mentioned pretreatment equipment. Instrument analysis can be performed more effectively.

[Brief description of the drawings]

FIG. 1 is a diagram showing an analytical pretreatment instrument used in the present invention having a double-tube structure.

FIG. 2 is a diagram simply showing the overall configuration of an analysis pretreatment device using the analysis pretreatment instrument of FIG.

FIG. 3 is a diagram showing an analytical pretreatment instrument used in the method of the present invention having a triple tube structure.

FIG. 4 is a view for explaining a method of collecting trace impurities on a hydrophobic surface in a droplet using the pretreatment device for analysis of FIG. 1;

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Kazuo Kawai 5-28-3 Shimosueyoshi, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture (56) References JP-A-2-293641 (JP, A) JP-A-61-77777 ( JP, A) JP-A-2-28533 (JP, A) JP-A-5-283498 (JP, A) JP-A-2-60873 (JP, U) JP-A-3-16061 (JP, U) JP Showa 64-5163 (JP, U) Japanese Utility Model Hei 2-2649 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 1/28 G01N 23/233

Claims (5)

(57) [Claims] 1. An analysis sample liquid is held substantially vertically and holds an analysis sample liquid.
A thin tube having a lower end capable of
The scattering of the analytical sample solution provided to surround the lower end
Using an instrument having an outer tube having an end that can be prevented, an analysis sample solution is previously sucked into the capillary, and the end of the capillary is heated to a predetermined temperature. in proximity to the hydrophobic analytes liquid drying board, the trial sample solution from the previous SL tubules
The liquid is gradually and continuously discharged at a predetermined position on the liquid drying plate.
As the sample liquid discharged in to contact with the lower end portion of the capillary tubes
The sample discharged and simultaneously discharged onto the sample liquid drying plate
By continuously evaporating liquid droplets, it is possible to continuously discharge
Sina As sample liquid does not spread over a particular diameter which is
Analysis pretreatment method characterized by causing the Luo said sample solution concentrated to dryness. 2. A discharge speed of a sample liquid from a lower end of a thin tube;
Adjust the evaporation rate by heating the sample liquid drying plate.
The diameter of the sample liquid discharged onto the sample liquid drying plate
The pre-analysis processing method according to claim 1, wherein the method is controlled . 3. An evacuation mechanism connected to an outer tube for evaporating the substance.
2. The pre-analysis processing method according to claim 1, wherein the pre-analysis processing is performed while removing by suction.
Law . As wherein prior Symbol fixtures, using an instrument second outer tube so as to surround it further outside of the outer tube is provided, at the same time as the exhaust evaporation material, the second outer tube The pretreatment method according to claim 3 , wherein an atmosphere is supplied. 5. The liquid is held substantially vertically and holds a liquid.
A thin tube having a lower end capable of
We can prevent splash of liquid provided to surround
Using a device having an outer tube with an end.
A liquid for dissolving and collecting the analysis surface impurities is previously sucked into the tube, the instrument is positioned so that the end of the outer tube is close to the hydrophobic analysis surface, and the liquid is discharged from the thin tube. on hydrophobicity analysis surface of the outer tube Te
Droplets to form, such that the droplets does not protrude from the outer tube, slightly while depressurizing the outer tube as required, it scans on hydrophobicity analysis surface the droplets by moving the instrument , The impurities on the hydrophobic analysis surface are collected in the droplets , and then all of the droplets are sucked into the capillary as the analysis sample solution.
And hydrophobic analytes which are heated end of the capillary tubes to a predetermined temperature
Place the sample solution from the capillary tube close to the sample
The liquid is gradually and continuously discharged at a predetermined position on the liquid drying plate.
So that the sample liquid discharged at the time contacts the lower end of the capillary.
The sample discharged and simultaneously discharged onto the sample liquid drying plate
By continuously evaporating liquid droplets, it is possible to continuously discharge
Make sure that the sample solution does not spread beyond a certain diameter.
And concentrating the sample solution to dryness .