JPH01189558A - Analyzing method of surface of si semiconductor substrate - Google Patents

Abstract

PURPOSE:To collect a sample with excellent operability and also to obtain the sample having little surplus impurity mixed in, by a method wherein an Si semiconductor is held horizontally in a vessel, a chemical liquid is so put as to cover the whole surface of the Si semiconductor and it is made to react therewith. CONSTITUTION:A holding table 5 for setting an Si semiconductor substrate 4 is provided in a reaction vessel 1 having a clean gas introduction port 2 and a discharge port 3. In the reaction vessel 1, the Si semiconductor substrate 4 is set horizontally on the holding table 5, and a chemical liquid 6 purified by a non-boiling distillation method is put on the Si semiconductor substrate 4 so that it covers the upper surface of the substrate. A clean N2 gas is blown in from the clean gas introduction port 2, the inside of the reaction vessel 1 is kept with clean atmosphere, the chemical liquid 6 is made to react with the surface of the Si semiconductor substrate 4 for a prescribed time, a reaction liquid thus obtained is collected, and an elementary analysis is conducted with the reaction liquid used as a sample. The 'prescribed time' is selected in conformity with an object of the surface analysis and the concentration of the chemical liquid, and ammonia, a hydrochloric acid, a nitric acid, a fluoric acid or the like is used as the chemical liquid, while an atomic absorption method or an ICP emission method is used as a method for the elementary analysis of the sample.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for analyzing the surface of a Si semiconductor substrate, and particularly relates to a method for analyzing the surface of a Si semiconductor substrate, and particularly to a sample for analyzing ultra-trace impurities present on the surface of a Si semiconductor substrate (hereinafter simply referred to as a "sample"). ) has its characteristics at the stage of collection.

(Prior Art) In an element manufacturing process, a Si semiconductor substrate is cleaned to remove contaminants adhering to its surface. After this cleaning, various surface analyzes are performed to evaluate cleanliness. In order to properly understand the analytical value in this surface analysis, ultra-L
This is essential for improving the performance and yield of SI devices.

Conventionally, a Si semiconductor substrate is placed vertically in a covered container, and a chemical solution is sprayed onto one surface of the Si semiconductor substrate from a spray nozzle to dissolve the surface of the Si semiconductor substrate and drop the solution (hereinafter referred to as reaction). (referred to as a solution) was collected in a saucer, and the reaction solution in the saucer was used as a sample.

(Problems to be Solved by the Invention) According to the above-mentioned conventional method, (a) there is a possibility that the dropped reaction liquid may be contaminated in the saucer.

(b) Even if sprayed only on one side of the semiconductor substrate, the sprayed chemical solution may wrap around the back side, and the reaction solution affected not only by the front side but also by the back side may drip. Surface analysis of a Si semiconductor substrate requires evaluation values for only one side on which elements are fabricated, and the influence of the back side must be avoided.

(C) The sprayed chemical solution becomes too fine particles, and the entire reaction solution does not drip onto the saucer, but instead adheres to the surface of the Si semiconductor substrate, making it difficult to recover all of it.

Generally, the sample tends to be contaminated from sources other than the Si semiconductor substrate, and as a result, the S
Even among i-semiconductor substrates, there were often those with poor electrical characteristics.

In other words, the analysis value obtained by the conventional surface analysis method does not represent the appropriate cleanliness of the surface of the Si semiconductor substrate, and is a value that is difficult to apply to VLSI devices.

In view of this point, it is possible to place the Si semiconductor substrate horizontally, but in this case, since the chemical used is hydrogen fluoride and is vapor, the reaction vessel must be equipped with a lid as described above. The chemical solution adhering to the lid sometimes dripped onto the substrate surface, resulting in contamination of the reaction solution.

(Means for Solving the Problems) The present invention solves the above problems by using a "liquid phase method" in which a liquid chemical is reacted. Specifically, a Si semiconductor substrate is placed horizontally in a container. A chemical solution is applied to cover the entire surface of the Si semiconductor and reacted with the surface of the Si semiconductor for a predetermined period of time, and the resulting reaction solution is collected and used as a sample for elemental analysis. are doing.

The above-mentioned "predetermined time" is selected depending on the surface analysis object and the concentration of the chemical solution. The chemical solution used is ammonia, hydrochloric acid, nitric acid, hydrofluoric acid, etc., and the elemental analysis method for the sample is as follows. Atomic absorption method or ICP emission method is used.

(Function) In other words, by holding the Si semiconductor substrate horizontally, it is possible to place the chemical solution on the Si semiconductor substrate so as to cover it, and when the chemical solution is placed and reacted in this way, it is necessary to cover the reaction container. The reaction solution generated by placing the chemical solution contains impurity elements only on the surface side of the Si semiconductor (the composition of impurity elements on the back side is irrelevant). Therefore, a sample containing few extra impurities can be obtained.

(Example) An embodiment of the present invention will be described below based on the drawings.

The drawing is a longitudinal section showing an embodiment of the present invention, and in the drawing, 1 is a reaction vessel, 2 is a clean gas inlet attached to the reaction vessel, and 3 is an outlet for the same. is Si
A holding table 5 for mounting a semiconductor substrate 4 is provided.

In the reaction vessel 1, a Si semiconductor substrate 4 is placed on a holding table 5, and a chemical solution 6 purified by a non-boiling distillation method is placed on the Si semiconductor substrate 4 so as to cover the upper surface of the Si semiconductor substrate 4. is placed, normal N2 gas is blown from the clean gas inlet 2 to maintain a clean atmosphere inside the reaction vessel 1, and the chemical solution 6 is
It is used to react the surface of the i-semiconductor substrate 4 for a predetermined period of time to obtain a sample.

Here, the non-boiling distillation method means placing commercially available chemicals and ultrapure water in separate containers and connecting the tops of both containers with piping, or placing the chemicals and ultrapure water in the same sealed container. In this method, the chemical vapor is absorbed into the pure water by placing it in a container and leaving it at room temperature for several days, thereby increasing the purity of the chemical.

Note that it is preferable to use a wet gas as the clean gas introduced into the reaction vessel 1. In this case, in addition to being able to maintain a clean atmosphere inside the container as described above, it is also possible to cope with the situation where the chemical solution on the Si semiconductor substrate dries.

A specific example in which elemental analysis was performed using a frameless atomic absorption spectrometer will be described below. The conditions for the flameless atomic absorption spectrometer are: drying at 1150°C for 30 seconds, ashing at 1000°C for 5 seconds for Na, and 4 seconds at 2200°C for atomized di-Na.

Si whose natural oxide film has a thickness of several tens of layers and a diameter of 4 inches
The semiconductor substrate 4 is placed on the holding table 5 of the reaction vessel 1, and the Si
4 cc of hydrofluoric acid purified by a non-boiling distillation method is dropped onto the semiconductor substrate 4 so as to cover the surface of the Si semiconductor substrate 4, and the Si semiconductor is left for 30 minutes while blowing normal N2 gas from the clean gas inlet 2. A target sample was obtained by reacting purified hydrofluoric acid on the surface of the substrate 4, and the sample was subjected to a flameless atomic absorption spectrometer to obtain the results shown in the table below.

Note that the analysis results obtained by the conventional method (a method in which the wafer is held upright, a chemical solution cleaned by a non-boiling method is sprayed, and the dropped solution is collected and analyzed) are subjected to the same temperature.

(Margins below) Analysis Results Table From this table, it was possible to clearly distinguish between different values of Na. Note that even though the same cleaning was performed, the analytical value of the conventional device was higher.

This is because in conventional equipment, the analysis value was high due to some kind of contamination due to the presence of a separate container, the influence of the back side, the presence of the lid, etc. It is considered a thing.

(Effects of the Invention) As explained above, according to the present invention, the chemical solution can be reacted only on the surface side of the Si semiconductor substrate, and
A sample is obtained that is not affected by impurity elements on the back side, and therefore desired accurate measurement values can be obtained.

[Brief explanation of the drawing]

The drawings are longitudinal sectional views showing embodiments of the present invention. 4...Si semiconductor substrate 6...Chemical liquid patent applicant Kyushu Electronic Metals Co., Ltd. Patent applicant Osaka Titanium Manufacturing Co., Ltd. Agent
Patent attorney Masa Mori Sumi 4...Si semiconductor substrate 6...Chemical solution

Claims (3)

[Claims] (1) Hold the Si semiconductor substrate horizontally in the container, and
A Si semiconductor substrate characterized in that an acid or alkaline chemical solution is placed so as to cover the entire surface of the semiconductor and reacted with the surface of the Si semiconductor for a predetermined period of time, and the reaction solution obtained is collected and used as a sample for elemental analysis. Surface analysis method. (2) The method for analyzing the surface of a Si semiconductor substrate according to claim 1, wherein the chemical solution is purified by a non-boiling distillation method. (3) The method for analyzing the surface of a Si semiconductor substrate according to claim 1, characterized in that a clean gas is introduced into the container during the reaction of the chemical solution.