JPS60260855A - Analysis of radioactive element in semiconductor material - Google Patents

Abstract

PURPOSE:To determine quantitatively and quickly the radioactive elements in a semiconductor material with good accuracy by using a hermetic decomposing vessel and a separating means which operates under pressurization. CONSTITUTION:A sample to be analyzed is first stored into the hermetic decomposing vessel 1 of which the entire part of the inside wall is constituted of a fluororesin 3. Said sample is heated to dissolve at 150-250 deg.C together with an inorg. acid. U and Th are separated from the matrix and concd. by using a constant volume pump which feeds the sample soln. and separating soln. to an ion exchange column 5 if necessary. The resulting sample soln. is dried and ashed on a boat made of a metal having a high melting point and thereafter the dried sample is introduced into the Ar plasma generated by heating to 1,500-2,000 deg.C. The respective radioactive elements are quantitatively determined from the intensity of the light emitted by the excitation. The pressure in the vessel 1 rises high during the decomposition by heating and therefore the easy decomposition of Al2O3 is made possible only by the inorg. acid according to the above- mentioned method. In addition, there is no contamination from the outside. The sample soln., etc. are fed under the pressure into the ion exchange resin 5 and therefore the resin column is made finer and the resolving power is made higher.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for the analysis of radioactive elements in semiconductor materials.

[Technical background of the invention and its problems] Radioactive elements contained as impurities in semiconductor materials, such as uranium (U)
,) A phenomenon in which data stored in a semiconductor memory is reversed due to α rays generated from lithium (Th), a so-called semiconductor dump error, is well known.

Among these semiconductor materials, for example, about 70% of Sin is contained as a filler in the semiconductor encapsulation resin, and the encapsulation resin is in direct contact with the semiconductor element.

In addition, Al1-84 alloy is used as wiring material, and Mo81hMo and W are used as electrode materials in semiconductor devices, so it is important to accurately and quickly quantify radioactive elements in a short time to improve the reliability of semiconductors. is important.

In general, methods for analyzing radioactive elements in semiconductor materials include:
For example, a method is used in which U is quantified by fluorescence photometry, Th is quantified by spectrophotometry, or υ and Th are simultaneously quantified by activation analysis. Among these analytical methods, the activation analysis method is the most superior in terms of detection sensitivity, product moment, and ability to quantify U and Th from the same sample.

When quantifying U, Th, etc. using the activation analysis method, ■Method of directly irradiating the sample with neutrons and measuring the radioactivity of %U, Th■
There is a method of decomposing a sample in advance with an inorganic acid or alkaline flux, separating and concentrating U and Th using an ion exchange separation method, and then irradiating the sample with neutrons to measure and quantify the radioactivity of U and Th. ■ is mainly suitable for high-concentration U and Th quantitative methods, and is excellent in speed by fM delivery, but there is a high risk of being exposed to a large amount of radioactivity during measurement, and high-concentration radioactive waste is There are drawbacks that occur. Method (2) is suitable for quantifying trace amounts of U%Th, but the radioactivity of trace amounts of [1,Th is weak and it takes several hours to several days to measure a sample. In addition, the activation analysis method required a nuclear reactor and was therefore impractical as an analysis method for quality control.

Furthermore, when quantifying trace amounts of U and Th by spectrophotometry, fluorometry, and the activation analysis method described in (2), U and Th are usually separated and concentrated at the pretreatment stage.゛For example, % 8i
0* is 810 for hydrofluoric acid and sulfuric acid! After volatilizing the StO, the undecomposed KL and OLL mixed in from the alumina balls used when grinding StO are melted with an alkaline flux, dissolved with an inorganic acid such as nitric acid, and then separated using a gravity-type ion exchange separation method. U and Th are separated and concentrated. however,
In these pretreatments, especially during sample decomposition, the sample often comes into contact with various reagents and analytical instruments, so there is a high possibility of contamination from the outside. Further, in the gravity-type ion exchange separation method, it takes a long time to separate U and Th, and when the separation ability between U and Th and the matrix is poor, it is necessary to repeat the separation operation 2.3 times.

It was not practical as an analysis method for quality control, which emphasizes high accuracy and speed.

[Purpose of the invention]

The present inventors have developed these conventional methods for quantitative analysis of U and Th.
U and T solve the problems of sample solution preparation and measurement in the laboratory.
As a result of various studies on quantitative analysis methods for h, the present invention has been completed.

[Summary of the invention]

That is, in the present invention, a sample to be analyzed is stored in a sealed decomposition container whose inner wall is entirely made of an inorganic acid or a fluororesin, and the sample is heated to 150 to 250°C together with the inorganic acid to dissolve it.
If necessary, %U and Th are removed and concentrated from the matrix using a constant volume pump that sends the sample solution and separation solution to the ion exchange resin column, and the obtained sample solution is dried and incinerated on a boat made of high melting point metal. After that, 1500-2000℃
Each radioactive element can be quantified from the excitation emission intensity by introducing it into argon plasma generated by heating. The present invention also provides a quantitative analysis method for radioactive elements in semiconductor materials, which is characterized by high sensitivity, high precision, and can be performed simply and quickly from the same sample.

A7.0 mixed in during crushing. has strong acid resistance and is usually not completely decomposed by inorganic acids. therefore.

Conventionally, it was melted with an alkaline flux and then dissolved with an inorganic acid. Therefore, there is a high possibility of contamination from alkaline fluxes, analytical instruments, etc.

In the present invention, the sample is decomposed using a closed decomposition container shown in FIG. 1 in a temperature range of 150 to 250°C. 15
If the temperature is below 0°C, it will take a long time to decompose the sample, and if it is above 250°C, the fluororesin will be attacked. During thermal decomposition, the inside of the container is under high pressure (5 to 25 kg/cm”)
However, this has the effect of promoting the decomposition of AI, o, and can easily decompose AI, 0° with just an inorganic acid, and since it is a sealed container made of fluororesin, there is no contamination from the outside. Nor.

In addition, a schematic diagram of an ion exchange separation device using a constant volume pump is shown in the second factor. In the conventional ion-exchange separation method using the gravity fall method shown in Figure 3, not only is it difficult to completely separate U and Th from the matrix, but also the sample solution or separation solution is mixed with the ion exchange resin due to gravity fall. It took a long time to pass the pillar. The ion exchange separation device of the present invention can feed the sample solution or separation solution into the ion exchange resin in a short time by applying pressure using a constant volume pump, so the resin column can be made thinner to improve separation performance. is possible, and U and Th can be completely separated from the matrix in a single operation.

[Embodiments of the invention]

Examples of analyzes of high-purity silica are shown below.

Place sample 10II in a fluororesin beaker, add 50 ml of hydrofluoric acid (1+1) and 5 ml of perchloric acid, and heat on a hot plate until almost dry. After cooling, add hydrochloric acid (1+1
), 5 tll was added and heated to melt away most of the residue, and then a 5 mm thick stainless steel container (diameter 50 mm) whose inner wall was coated with 3 mm thick fluororesin as shown in Fig. 1 was prepared.

Rinse with water to a depth of 3 Qmm) and add hydrofluoric acid (
1+1), 10 rnJ and 5 ml of hydrochloric acid were added thereto, and a 5 mm thick stainless steel lid whose inner surface was coated with a 5 mm thick fluororesin was fitted with a screw to secure the lid. Next, this closed decomposer was left for 2 hours in an air chamber whose temperature was controlled at 200°C. Sulfuric acid after quenching (1+1), 1
Add mJf and 5 ml of perchloric acid, generate white sulfuric acid smoke, and heat to near dryness.

After cooling, 5 m of nitric acid (1+1) was added and dissolved.

The obtained solution was held in a fluoroplastic preparative loop having a diameter of 3 mm and a length of 1.4 m of an ion exchange chromatograph shown in FIG. 2 using a constant volume pump. Next, the anion exchange resin was injected from the top of the column, and the solution flowing out from the bottom of the column was collected.
Strongly basic quaternary ammonium form (trade name, DOWBX
1-X8200 to 400 mesh L) was used by filling a column with a diameter of g mm and a length of 2 ocm. Flow 30ml of 7N nitric acid through the column to remove the matrix (Fe, Ca, Na,
etc.) are flushed out. Furthermore, 0.5 N hydrochloric acid somi was flowed to elute U and 'rh, and the mixture was collected in a fluororesin beaker. Evaporate the solution to near o, i m, and
This was used as the test solution.

Collect 5 to 50 μm of this test solution using a microphone pipette and inject it onto the tungsten boat of a high-temperature vaporizer.
Dry at 100°C as shown in Table 1.

After incineration at 160°C, it was vaporized at 2300°C and introduced into Argon Plasma, where U and Th were quantitatively analyzed by emission spectroscopy.

Table 2 shows the quantitative analysis values of U and Th obtained by the above operations and the time required for analysis. For comparison, the quantitative analysis values of U and Th in the same sample using the activation analysis method and the time required for two analyzes are also shown. As is clear from the above results, compared to the conventional activation analysis method, 0 and 5p, which could not be quantified,
It has been found that U and Tb below PB can be analyzed easily and in a large amount of samples in a short time using IA7.

Table 1: High-frequency stimulated plasma emission spectroscopy Table 2 [Effects of the invention] According to the present invention, 0.5 ppb, which was previously impossible to quantify.
The following radioactive elements can be easily analyzed over a long period of time, and its industrial value is great.

[Brief explanation of the drawing]

Figure 1 shows 1 a vertical cross-sectional view of a sealed decomposer used in the present invention, and
The figure is a schematic diagram of an element separation device similarly used in the present invention, and FIG. 3 is a schematic diagram of a conventional ion exchange separation device. 1... Lid, 2... Container, 3... Fluorine resin, 4...
... Screw, 5 ... Anion exchange resin, 6 ... Sample solution, 7 ... Effluent, 8 ... Preparation loop, 9,9',
9'... Eluent. Representative Patent Attorney Noriyuki Chika (and 1 other person) ’7

Claims (1)

[Scope of Claims] (1> Decompose the sample to be analyzed with an inorganic acid or a closed decomposition container, separate and concentrate radioactive elements from the matrix by ion exchange separation if necessary, and use the resulting sample solution to make a refractory metal. After drying and ashes on the boat, 1,500 to 2,000
℃ to evaporate it, introduce it into argon plasma generated by high frequency induction heating of 10 to 30 MHz,
A method for analyzing radioactive elements in semiconductor materials, characterized by quantitative determination based on excitation emission intensity. ρ) In the analysis method described in claim 1, when the sample to be analyzed is decomposed, it is stored in an airtight decomposition container made of an inorganic acid or at least the entire inner wall of which is made of a fluororesin,
A method for analyzing radioactive elements in a semiconductor material, which comprises heating and dissolving at 150 to 250°C together with an inorganic acid. G) In the analytical method described in claim 1, when separating and concentrating radioactive elements from a sample solution, a constant volume pump that sends at least one sample solution to an ion exchange resin column is used to separate and concentrate the radioactive element. A method for analyzing radioactive elements in semiconductor materials, characterized by: