JPH0795021B2 - Semiconductor disassembly device - Google Patents

Description

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

(Prior Art) As is well known, when impurities such as Na, K, and Fe are present in a silicon crystal used as a semiconductor substrate material, the electrical characteristics of a semiconductor element are To be greatly affected. Therefore, in order to reduce the amount of these impurities and improve the characteristics of the device, it is necessary to first accurately grasp the content of the impurities. However, since the amount of impurities in silicon crystals is extremely small, sufficient data could not be obtained by instrumental analysis, and chemical analysis was often performed. A liquid phase decomposition method in which a silicon wafer is dissolved in a mixed acid of hydrofluoric acid and nitric acid is used to prepare a sample for measuring impurities in a silicon wafer.

A decomposition container conventionally used for this purpose is composed of a main body 6 and a lid 7 as shown in a perspective view of FIG. 2, and a decomposition container as shown in a plan view of FIG. 3 showing a dissolved state in the main body 6. A silicon wafer 8 is put in the inside, a mixed acid 9 of ultra-high purity hydrofluoric acid and nitric acid is poured, the lid 7 is closed as shown in FIG. 2 and left at room temperature for a predetermined time. After a lapse of a predetermined time, the silicon wafer is completely decomposed by the mixed acid, and the amount of impurities in the decomposed solution is measured. Although the amount of impurities is usually measured by the flameless atomic absorption method, the decomposition solution is not diluted and used as a sample in a concentrated acid state.

However, in the above-mentioned method, when measuring with a flameless atomic absorption spectrometer, since the decomposition solution of concentrated acid is injected into the sample inlet of the apparatus, the graphite tube for heating the sample and peripheral parts are deteriorated by the acid. I often have to replace parts. In addition, the amount of impurities in the sample cannot be accurately measured due to rusting from the part that cannot be replaced.

Therefore, if the decomposition solution is diluted to an acid concentration level where the flameless atomic absorption spectrometer does not deteriorate, the amount of impurities in the decomposition solution is originally very small (for example, the Na concentration is 10 ¹⁶ atoms / cm ³ or less), and this is further diluted. There is a problem that impurities cannot be detected. Further, in the method of heating the decomposition liquid with a heater in advance, concentrating it and then diluting it with pure water, there is a problem that it takes time to condense and the decomposition liquid is contaminated from the outside during that time. .

(Problems to be Solved by the Invention) The present invention has been made in view of the above problems, and it is possible to obtain a sample for measuring the amount of semiconductor impurities of a silicon wafer accurately, accurately, and rapidly, and to decompose a semiconductor. The purpose is to provide a device. It is also an object of the present invention to provide a decomposition device for preparing a sample that prevents deterioration of a measuring device such as a flameless atomic absorption spectrometer.

[Structure of the Invention] (Means and Actions for Solving the Problem) In the semiconductor decomposing apparatus of the present invention, a whole silicon wafer is dissolved by a mixed acid of hydrofluoric acid and nitric acid to obtain a sample solution for trace impurity analysis. Which is a semiconductor decomposing device for melting and processing a whole silicon wafer in a state of being shielded from the atmosphere, a heating means for heating a decomposing solution in the container from outside the container, and a decomposing solution heated by the heating means. At the same time, a pressure reducing means for reducing the pressure in the container and concentrating the liquid is divided,
And a pure water injection port for preparing the sample solution by diluting the concentrated decomposition solution in the container.

In the apparatus of the present invention, the wafer decomposition solution is connected to the aspirator, the pressure inside the container is reduced, and the container is simultaneously heated by the heater for heating. Therefore, the decomposition liquid is rapidly concentrated without being contaminated from the outside. Also, by diluting the decomposed solution, a diluted solution can be made without changing the original amount of impurities, and the diluted solution is measured by a flameless atomic absorption spectrometer, so that deterioration of the graphite tube at the sample inlet and peripheral parts is prevented. Prevents, extends the life of the measuring device, and provides accurate and accurate numerical values for impurity measurement.

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

In a closed decomposition vessel 1 having a pure water inlet 4 and an aspirator connection port 5, a silicon wafer is previously dissolved with a mixed acid of hydrofluoric acid and nitric acid, and when completely dissolved, the aspirator connection port 5 is attached to the aspirator 3. While connected, the inside of the container is depressurized and heated by the heating heater 2 provided in the decomposition container 1 and left for a predetermined time. Initially, the fumed acid concentration drops to the azeotropic composition, and further vaporizes in the azeotropic composition. After the decomposition liquid 9 is volatilized and concentrated, a predetermined amount of pure water is injected from the pure water injection port 4 to prepare a diluting liquid having an acid concentration significantly lower than the azeotropic composition. The diluted solution is collected with a micropipette and the amount of impurities is directly measured by a flameless atomic absorption spectrometer.

[Effects of the Invention] According to the present invention, by heating the decomposition liquid under reduced pressure, it is possible to easily concentrate in a short time, and it is possible to suppress contamination in the atmosphere to a minimum and improve analysis accuracy. I was able to.

In addition, by diluting the decomposed solution and measuring the diluted solution with a flameless atomic absorption spectrometer, deterioration of the sample injection port is prevented, the life of parts is extended, and the influence of contamination due to rusting of the sample injection port is prevented. I no longer receive it.

FIG. 4 shows the results of measuring the amount of Na in the silicon wafer by the conventional concentration method and the concentration method of the present invention. Two wafers were sampled from each silicon wafer of the same lot, and a measurement sample was obtained for each sample. When I measured each sample three times with a flameless atomic absorption spectrometer,
In the conventional method, impurities are mixed in or released during the concentration.
It can be seen that the averages of NO.1 and No.2 do not match, and the mixed acid has an effect on the measuring device, resulting in poor accuracy, whereas the method of the present invention is extremely accurate and highly accurate.

As a result, the amount of trace impurities in the semiconductor substrate can be accurately and quickly ascertained, which can contribute to the improvement of the quality of the semiconductor device.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a semiconductor disassembling apparatus of the present invention, FIG. 2 is a perspective view of a conventional disassembling container, FIG. 3 is a plan view showing a usage state of the container of FIG. 2, and FIG. 4 is an effect of the present invention. 7 is a graph for explaining. 1 ... Decomposition container, 2 ... Heating heater, 3 ... Aspirator, 4 ... Pure water injection port, 5 ... Aspirator connection port, 9 ... Decomposition liquid.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Rie Aono 25-1, Ekimaehonmachi, Kawasaki-ku, Kawasaki-shi, Kanagawa Toshiba Microcomputer Engineering Co., Ltd. (56) Reference JP-A 61-144545 (JP, A) JP A Sho 62-73137 (JP, A) JP-A-59-73001 (JP, A)

Claims (1)

[Claims] 1. A semiconductor decomposing device for dissolving a whole silicon wafer with a mixed acid of hydrofluoric acid and nitric acid to obtain a sample solution for trace impurity analysis, wherein the whole silicon wafer is cut off from the atmosphere. A container for melting and processing,
A heating means for heating the decomposition liquid inside the container from the outside of the container; a decompression means for heating the decomposition liquid by the heating means and decompressing the inside of the container to concentrate the decomposition liquid; and a concentrated decomposition liquid inside the container. A semiconductor decomposing device, comprising: a pure water inlet for diluting to prepare the sample solution.