JPS6250660A - Trace organic material measuring instrument - Google Patents

Abstract

PURPOSE:To measure the amt. of the trace org. material in a semiconductor wafer in a short period with high sensitivity by irradiating UV rays on a sample housed in a cell in a UV cracking device in which a UV transmittable gas is filled, passing oxygen to the cell, heating the same and introducing the cracking gas through a concentration column into an analyzing instrument. CONSTITUTION:Gaseous nitrogen is supplied from a cylinder 11 into a UV cracking section 1; at the same time, a specified flow rate of oxygen is passed to the cracking cell 11 through a column 9 which adsorbs impurities from an oxygen cylinder 7. The UV rays are irradiated from a light source 5 on a sample while the sample is heated by a heat block 6. The cracking gas is captured through a 6-way valve 14 to the concentration column 17. Gaseous He is passed from a cylinder 19 to a column 17 and the cracking gas eliminated by a heater 24 is supplied via a sepn. column 26 to a photoionization detector 27. On the other hand, part of the gaseous He is fed through a gas permeating resistance force column 29 to a detector 27 as an electric discharge gas. The output signal from the detector 27 is fed via an amplifier 32 to a recorder 33, by which separated CO2, CO and H2O are measured.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention relates to a trace organic substance measuring device.

[Background of the invention]

A method of cleaning organic contaminants using ultraviolet rays is disclosed in fF Publication No. 59-94821 and Japanese Patent Publication No. 59-94825.
These are Big's review article ``UV10.・Cleaning Op Surf Ace (UV10゜CLtani)''.
On the other hand, there is a method to measure trace amounts of organic matter using the gas produced by the decomposition of organic matter by ultraviolet rays.However, in order to collect the decomposed gas, a decomposition reaction is performed This is carried out in a cell that transmits ultraviolet rays well, but if oxygen exists between the ultraviolet lamp and the cell, the oxygen absorbs light energy around 185rLm and produces ozone, and further ozone
L77! Because it absorbs nearby light energy, the ultraviolet light from the lamp is attenuated considerably by the time it reaches the cell.

Further, depending on the film thickness of the organic substance on the semiconductor wafer, there is a limit to complete oxidative decomposition by ultraviolet rays and ozone. Therefore, there is a problem in that it takes a considerable amount of time to decompose the organic matter on the semiconductor wafer housed in the cell.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a trace organic matter measuring device that can measure the amount of trace organic matter in a semiconductor wafer in a short time and with high sensitivity.

[Summary of the invention]

The present invention includes a cell that accommodates a semiconductor wafer and is capable of transmitting ultraviolet rays, a light source for irradiating ultraviolet rays to trace organic substances on the semiconductor wafer housed in the cell, and a cell that decomposes the organic substances on the semiconductor wafer with ultraviolet rays. a heat source for promoting decomposition when the cell is heated; a gas side between the light source and the cell that absorbs less ultraviolet rays is filled with nitrogen gas; and an irradiation section for housing the light source, cell, and heat source; an oxygen supply section for supplying oxygen to the cell; a concentrating column for concentrating decomposed gas produced by decomposing organic matter on the semiconductor wafer with ultraviolet rays; a heating section for desorbing the decomposed gas from the concentrating column; It is characterized by comprising a carrier supply section and a gas chromatogram for measuring the gas desorbed from the concentration column. According to the trace organic substance measuring device having such characteristics, it is possible to decompose and concentrate trace organic substances on a semiconductor wafer in a short time and perform measurement with high sensitivity. This principle is explained as follows.

Ozone and trace organic matter generated by irradiating oxygen with ultraviolet rays (
For example, CyLHnOJ (n, rIL, A is a natural number) reacts as shown in the following formulas (1) to (5).

Ar (184,94m) + 02 #0 + O...
・・・・・・・・・・・・・・・・・・・・・(1)02+
0 zuOs ,,0. −、 、、、 、、
, , , , , , , , (2) OB + CnH
mOa −> CCfCyu), COzCgrti'
), H2αF-6)-0-(5)Ar (254,7nm
)+Os #02 + 0 ・・””・”・”・44)
o” + Ci 翫 OJ & Co C♂ (ρ), C02 (y
aa), H2O(, p)...(5) (Here, * represents an excited state.) When oxygen is irradiated with light around 184.9 nnh, it absorbs the light energy and generates ozone (O3). ((1).

(2) formula). Because ozone has a strong oxidizing effect,
Bonds with trace amounts of organic matter carbon (C) and hydrogen (H) attached to semiconductor wafers and decomposes them into -carbon oxide (CO), carbon dioxide (CO2) -water vapor (H2O) (formula (5))
, On the other hand, when oscine is irradiated with light around 254.7 nm,
It absorbs light energy and generates excited oxygen atoms (0*), which has an even stronger oxidizing effect than ozone, and like ozone, it bonds to trace amounts of organic matter C, H, 0, Co, Co,...
H2OIl? : decomposes ((a), (5) formula); in reaction equations (51, (5)), by heating trace amounts of organic matter attached to the semiconductor wafer, the decomposition reaction is further accelerated than the decomposition reaction by ultraviolet rays and ozone. do.

On the other hand, if there is a layer of air between the lamp and the pill,
Oxygen in the air absorbs light around 184.9377L and generates ozone, and ozone also absorbs light around 254.7nm, so the ultraviolet rays from the light source are attenuated by the time they reach the cell. This makes it difficult for the decomposition reaction of trace amounts of organic matter on the housed semiconductor wafers to proceed. Therefore, by shortening the distance between the lamp and the cell and at the same time filling the atmosphere with a gas that absorbs little ultraviolet rays (for example, nitrogen gas), the inside of the cell can be efficiently irradiated with ultraviolet rays.

The decomposition gas generated by decomposition within the cell is concentrated in a concentrator column and injected into a gas chromatogram that is highly sensitive to Co, Co, ..., H2O to quantitatively measure the concentration of contaminant organic matter.

According to this device, organic substances can be decomposed in a shorter time and trace amounts of organic substances can be measured with high sensitivity.

[Embodiments of the invention]

FIG. 1 is an explanatory view of the main parts of a specific embodiment for explaining the principle of the trace organic substance measuring device of the present invention, and FIG.
In FIG. 1 showing the overall configuration of the embodiment, an ultraviolet decomposition unit 1 includes a cell 4 with a window plate S through which oxygen can flow and which houses a semiconductor wafer 2 and can transmit ultraviolet rays; It is composed of a light source 5 for irradiating ultraviolet rays onto trace amounts of organic matter on semiconductor wafers 2 housed in the ultraviolet ray decomposition unit 1, and a heat block 6 for heating the ultraviolet ray decomposition unit 1. It is possible to oxidize and decompose trace amounts of organic matter on the semiconductor wafer 2 using oxygen, ultraviolet rays, and heat. The oxygen coming out of the oxygen cylinder 7 passes through a pressure regulator 8 and flows through a column 9 that adsorbs impurities contained in the oxygen.
Inside the ultraviolet decomposition unit 1, which flows into the ultraviolet decomposition unit 10 decomposition cell 4 at a constant flow rate through a constant flow valve 10, nitrogen gas, which absorbs little ultraviolet rays, is supplied from a cylinder 11 to a pressure regulator 12.
, is supplied via a constant flow valve 15. The decomposition gas of trace organic matter on the semiconductor wafer 2 stored in the decomposition cell 4 is 6
The sample passes through a two-way valve 14 and is adsorbed onto the concentration packing material 18 of the concentration column 17, which has been cooled in a constant temperature chamber 16 containing a refrigerant 15 in advance, and is used as an analysis sample. As a result, trace amounts of organic matter on the semiconductor wafer 2 can be decomposed in a shorter time by efficiently irradiating ultraviolet rays and promoting thermal decomposition reactions. The overall configuration of the combined trace organic matter measuring device is shown.

The analysis sample concentrated in the concentration packing material 18 of the concentration column 17 is placed in the dotted line state of the 6-way valve, so that part of the helium scum from the helium cylinder 19 is transferred to the pressure regulator 20 and the column 21 that adsorbs gas impurities. , constant flow pulp 22.6
It flows through the concentrating column 17 through the direct valve 14 and is heated to the heating section 2.
It is separated by the heater 24 of No. 5, passes through the six-way valve 14 again,
It is separated by a separation column 26 of a gas chromatography device 25 and supplied to a photoionization detector 27 . On the other hand, helium cylinder 19
The remaining helium gas that has flowed through the pressure regulator 20 and the column 21 flows through the constant flow valve 28 and the ventilation resistance column 29, and is supplied to the photoionization detector 27 as a discharge gas. The gas chromatography device 25 includes constant flow rate pulps 22 and 28, a separation column 26, an aeration resistance column 29, a constant temperature bath 50 that keeps them at constant temperature, a temperature control 51, and a photoionization detector 27.
It is composed of an amplifier 52 that amplifies the signal from this detector, and a recorder 55, and measures the separated carbon monoxide, carbon dioxide, and water, respectively.

With the configuration described above, the concentration ratio of carbon and hydrogen atoms of the organic contaminants on the semiconductor wafer 1 can be measured in a shorter time.

〔Effect of the invention〕

According to the present invention, since the attenuation of ultraviolet rays is suppressed before reaching the decomposition cell, the decomposition reaction of trace amounts of organic matter within the cell is accelerated, and furthermore, since the decomposition reaction is assisted by heat, decomposition and concentration can be achieved in a shorter time. , which can be quickly analyzed using existing analytical equipment.

[Brief Description of the Drawings] Fig. 1 is an explanatory diagram of the main parts of a specific embodiment for explaining the principle of the trace organic substance measuring device of the present invention, and Fig. 2 is a schematic diagram showing the overall configuration of the embodiment. It is. 1... Ultraviolet decomposition unit, 2... Semiconductor wafer, S... Window plate, 6... Heat block. 8...Pressure regulator. 12... Pressure regulator, 15... Refrigerant, 16... Constant temperature container, 20... Pressure regulator, 21... Column, 50... Constant temperature chamber, 55... Recorder. Representative Patent Attorney Katsutoshi Ogawa = No. t

Claims (1)

[Claims] 1. In an apparatus for measuring trace amounts of organic substances using ultraviolet decomposition, a sample is housed in an ultraviolet decomposition device that can be filled with a gas that absorbs little ultraviolet rays, and a cell through which ultraviolet rays can pass; an oxygen supply section for supplying oxygen into the cell, and a concentrating column for concentrating the decomposed gas of the trace organic matter; and a heating section and a carrier supply section for desorbing the decomposed gas from the concentrating column, and an analysis device capable of measuring with high sensitivity the decomposed gas desorbed from the concentrating column. measuring device.