JPH01301142A - Semiconductor decomposing device - Google Patents

Abstract

PURPOSE:To exactly, accurately and rapidly obtain a sample for measuring the impurity quantity of a semiconductor by heating a decomposing liquid from the outside of a vessel and simultaneously reducing the pressure in the vessel, thereby thickening the decomposing liquid. CONSTITUTION:A silicon wafer is dissolved by an acid mixture composed of hydrofluoric acid and nitric acid in the hermetically closed decomposing vessel 1 having a pure water injecting port 4 and an aspirator connecting port 5. The aspirator connecting port 5 is connected to the aspirator 3 when the wafer is completely dissolved. The water is then heated by a heater 2 for heating provided to the decomposition vessel 1 and is rested for a prescribed period of time while the pressure in the vessel is reduced. The acid concn. at which fuming takes place in the beginning lowers down to the azeotropic compsn. and further, the acids evaporate with the azeotropic compsn. A prescribed volume of pure water is injected into the vessel from the pure water injecting port 4 to form the dilute liquid which is drastically lowered in the acid concn. from the azeotropic compsn. when the decomposing liquid 9 evaporates and thickens. The dilute liquid is taken by a micropipette and the impurity quantity is measured by a direct flameless atomic absorption device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a semiconductor decomposition apparatus, and is particularly used for analyzing trace impurities in silicon wafers.

(Prior Art) As is well known, if impurities such as Na, Fe, etc. are present in silicon crystal used as a semiconductor substrate material, the electrical characteristics of the semiconductor device will be affected even if the amount is extremely small. be greatly affected. Therefore, in order to reduce the amount of these impurities and improve the characteristics of the element, it is first necessary to accurately understand the impurity content. However, since the amount of impurities in silicon crystals is extremely small, it is not possible to obtain sufficient data through instrumental analysis, and chemical analysis has often been performed. To prepare samples for measuring impurities in silicon wafers, a liquid phase decomposition method is used in which the silicon wafer is dissolved in a mixed acid of hydrofluoric acid and nitric acid.

Conventionally, the decomposition vessel used for this purpose is composed of a main body 6 and a pipe 7 as shown in the perspective view of FIG. 2, and as shown in the plan view of FIG. A silicon wafer 8 is placed in the container, and a mixed acid 9 of ultra-high purity hydrofluoric acid and nitric acid is poured into the container.The lid 7 is sealed as shown in FIG. 2, and the container is left at room temperature for a predetermined period of time. After a predetermined period of time has elapsed, the silicon wafer is completely decomposed by the mixed acid, and the amount of impurities in the decomposed solution is measured. Frameless atomic absorption spectrometry is the best way to measure the amount of impurities, but the decomposition solution is not diluted and is used as a sample as a concentrated acid.

However, in the above-mentioned method, when measuring with a flameless atomic absorption spectrometer, the graphite tube for heating the sample and surrounding parts deteriorate due to the acid because a concentrated acid decomposition solution is injected into the sample injection port of the device. However, parts must be replaced frequently. Furthermore, it is not possible to accurately measure the amount of impurities in the sample due to rust, etc. from parts that cannot be replaced.

Therefore, when the decomposition solution is diluted to the acid concentration level at which the flameless atomic absorption spectrometer wants to deteriorate, the amount of impurities in the decomposition solution is originally very small (for example, the Na concentration is 10I6ato
lls/cm' or less) is further diluted, which poses a problem in that impurities cannot be detected. In addition, the method of heating the decomposed liquid in advance with a heater, concentrating it, and then diluting it with pure water has the problem that it takes time to concentrate, and during that time the decomposed liquid becomes contaminated from the outside. .

(Problems to be Solved by the Invention) The present invention has been made in view of the above, and provides a semiconductor decomposition device that can accurately and precisely obtain a sample for measuring the amount of semiconductor impurities and quickly. The purpose is to Another object of the present invention is to provide a decomposition device for sample preparation that prevents deterioration of measurement devices such as frameless atomic absorption spectrometers.

[Structure of the Invention J (Means and Effects for Solving the Problems) The semiconductor decomposition apparatus of the present invention is for dissolving a semiconductor to obtain a sample liquid for trace impurity analysis, and is in a state where it is shielded from the atmosphere. A sealed container for melting and processing semiconductors,
a heating means for heating the decomposition liquid in the container from outside the container; and a decompression means such as an aspirator for heating the decomposition liquid by the heating means and at the same time reducing the pressure in the container to condense the decomposition liquid; It is characterized by comprising a pure water inlet for diluting the concentrated decomposition liquid in the container to prepare the sample liquid.

In the apparatus of the present invention, the wafer decomposition liquid is connected to the aspirator, the pressure inside the container is reduced, and the container is simultaneously heated with a heating heater, so that the decomposition liquid is rapidly concentrated without being contaminated from the outside. In addition, by diluting the decomposed solution, a diluted solution is created without changing the original amount of impurities, and the diluted solution is measured with a flameless atomic absorption spectrometer, so deterioration of the graphite tube of the sample injection port and surrounding parts can be prevented. This prolongs the life of the measuring device and provides accurate and accurate values for impurity measurements.

(Embodiment) FIG. 1 shows the structure of a disassembly apparatus according to an embodiment of the present invention.

In a sealed decomposition container 1 having a pure water inlet 4 and an aspirator connection port 5, silicon wafers are dissolved in advance with a mixed acid of hydrofluoric acid and nitric acid, and once completely dissolved, the aspirator connection port 5 is connected to the aspirator connection port 5. -3, and while reducing the pressure inside the vessel, it is heated with the heating heater 2 provided in the decomposition vessel 1, and left for a predetermined period of time. The acid concentration that initially produced smoke decreases to an azeotropic composition, and further volatilizes at the azeotropic composition.

After the decomposition liquid 9 is volatilized and concentrated, a predetermined amount of pure water is injected from the pure water inlet 4 to create a diluted liquid whose acid concentration is much lower than the azeotropic composition. The diluted solution is collected with a micropipette, and the amount of impurities is directly measured using a flameless atomic absorption spectrometer.

[Effects of the Invention] According to the present invention, by heating the decomposition liquid under reduced pressure, it can be easily concentrated in a short time, and contamination in the atmosphere can be minimized, thereby improving analytical accuracy. was completed.

In addition, by diluting the decomposed solution and measuring the diluted solution with a flameless atomic absorption spectrometer, we can prevent deterioration of the sample inlet, extend the life of parts, and reduce the effects of contamination due to rust in the sample inlet. I no longer receive it.

Figure 4 shows the results of measuring the amount of Na in silicon wafers using the conventional concentration method and the concentration method of the present invention. Two wafers from the same lot were used as samples, and a measurement sample was prepared for each sample. I got it. When each sample was measured three times using a flameless atomic absorption spectrometer, it was found that in the conventional method, impurities were mixed in or removed during concentration, and the averages of No. 1 and No. 3, which should match, did not match. It can be seen that the method of the present invention is extremely accurate and accurate, whereas the method of the present invention has an effect on the equipment and has poor accuracy.

As a result, the amount of trace impurities in the semiconductor substrate could be accurately and quickly determined, contributing to improving the quality of semiconductor devices.

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram of the semiconductor decomposition apparatus of the present invention, Fig. 2 is a perspective view of a conventional decomposition container, Fig. 3 is a plan view showing the usage state of the container shown in Fig. 2, and Fig. 4 is a detailed diagram of the present invention. This is a graph that explains. 1... Decomposition container, 2... Heating heater, 3.
...Aspirator-54...Pure water inlet, 5...
Aspirator connection port, 9... Decomposition liquid. Figure 1 Figure 3

Claims (1)

[Claims] 1 A semiconductor decomposition device for dissolving a semiconductor to obtain a sample solution for trace impurity analysis, which includes a container for dissolving and processing the semiconductor in a state cut off from the atmosphere, and a device for heating the decomposition liquid inside the container from outside the container. a heating means for heating the decomposition liquid by the heating means and at the same time reducing the pressure in the container to concentrate the decomposition liquid; and pure water for diluting the concentrated decomposition liquid in the container to prepare the sample liquid. A semiconductor decomposition device characterized by comprising an injection port.