JPH11183366A - Measurement cell for spectral analysis - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately analyze gas containing a constituent which is condensed at an ordinary temperature and decomposed at a high temperature by providing a means for heating a tubular cell main body and a means for heating a transmissive window material. SOLUTION: A measurement cell for spectral analysis is so constructed that a heating means 5 is provided like a cylinder in the outer periphery of the cell main body 1, and as a buffer material 9, a rubber heater having designated elasticity is used. By this arrangement, a transmissive window material 2 can be directly heated by the buffer material 9, and the heating temperature (heating capability) of the transmissive window material 2 can be set separately from the heating temperature of the cell main body 1 by the heating means 5, so that the cell main body 1 and the transmissive window material 2 can be surely heated to the designated temperature. Thus, condensation of gas can be prevented by a portion of the transmissive window material 2, and decomposition of gas in the cell main body 1 can be prevented, so that gas containing a condensed constituent and a decomposited constituent can be analyzed accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring cell for spectroscopic analysis, and more particularly to a measuring cell for spectroscopic analysis used for analyzing a gas used in the field of semiconductor manufacturing.

[0002]

2. Description of the Related Art Infrared absorption spectroscopy is widely used as a method for measuring trace impurities contained in a gas.
In this method, the measurement gas in the infrared region is irradiated to the gas to be measured flowing in the measurement cell, and the type and content of impurities are measured by measuring the absorption spectrum of the light that has passed through the gas to be measured. As the measurement cell, a cell in which a translucent window material for transmitting measurement light is attached to both ends of a cell body through which a gas to be measured flows is used.

In the spectroscopic analysis using the measuring cell, the gas to be measured is introduced into the cell from a gas inlet provided at one end of the measuring cell, and is derived from a gas outlet provided at the other end. The gas to be measured is circulated in this state, and in this state, a measurement light having a predetermined wavelength, for example, a laser beam is introduced into the cell through the translucent window material at one end, and is derived from the translucent window material at the other end. The measurement data is obtained by analyzing the measurement light.

[0004]

On the other hand, in the field of semiconductor manufacturing in recent years, it has become necessary to analyze a gas containing a component condensing at room temperature and a component decomposing at high temperature with high sensitivity. In the analysis of a gas containing such components, if the gas is condensed and adheres to the inside of the cell or the light-transmitting window material, it will hinder the flow of gas and the transmission of measurement light. Heat must be applied to prevent condensation of the gas. At this time, since the cell body of the measurement cell is usually formed of a metal such as stainless steel, it can be easily heated to a predetermined temperature by covering its outer periphery with a heater or the like. Cannot be covered with a heater or the like, so that the translucent window material is heated to a predetermined temperature by heat conduction from the cell body.

However, in order to heat the translucent window material to a temperature at which condensed components do not adhere by heat conduction from the cell body, it is necessary to heat the cell body to an unnecessarily high temperature. In order to heat the conductive window material to about 100 ° C., it was necessary to heat the cell body to several hundred degrees Celsius. However, when the cell body is in such a high temperature state,
Components that decompose at high temperatures, for example, silane, dichlorosilane, trichlorosilane, etc., begin to decompose at about 200 ° C., and thus decompose in the cell body.

That is, if the translucent window material is heated to a temperature at which the condensed component does not adhere, the cell body must be excessively heated, so that the gas is decomposed in the cell body. However, if the cell body is heated to a range where the gas does not decompose, the light-transmitting window material cannot be sufficiently heated, and condensed components adhere to and accumulate on the light-transmitting window material, thereby impeding the transmission of the measurement light. Will be. Therefore, gases containing components that condense at room temperature and components that decompose at high temperatures,
The measurement of a gas containing a component having a small difference between the condensation temperature and the decomposition temperature cannot be performed accurately with a conventional spectroscopic analyzer.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a spectroscopic measuring cell capable of accurately analyzing a gas containing a component which condenses at room temperature and decomposes at high temperature.

[0008]

In order to achieve the above object, a measuring cell for spectroscopic analysis of the present invention comprises a tubular cell body having a gas inlet at one end and a gas outlet at the other end. In the measurement cell for spectroscopic analysis, each equipped with a translucent window material, means for heating the tubular cell body,
Means for heating the translucent window material is provided.

In particular, in the measurement cell for spectroscopic analysis of the present invention, the means for heating the light-transmitting window material may include a ring-shaped buffer material for mounting the light-transmitting window material on the tubular cell body. Or a heating element deposited in a ring shape on the surface of a translucent window material.

[0010]

FIG. 1 is a partially sectional front view showing a first embodiment of a measuring cell for spectroscopic analysis of the present invention. The measuring cell for spectroscopic analysis has a tubular cell body 1 having a predetermined length, a light-transmissive window material 2 which is attached to both ends of the cell body 1 at a predetermined angle, and one end of the cell body 1. The gas introduction pipe 3 connected to the gas supply pipe 4 connected to the other end, the heating means 5 provided in a cylindrical shape on the outer periphery of the cell main body 1, and the translucent window material 2 are attached to the cell main body 1. It is formed by a fixing flange 6 and a holding flange 7 for fixing, an O-ring 8 and a cushioning material 9 provided inside and outside the translucent window material 2, and a bolt 10 for fastening the flanges 6 and 7. I have.

The cell body 1 is usually formed of SUS316, but is made of metal such as other stainless steel, nickel steel, chromium-molybdenum steel, hastelloy, etc., which has little moisture adsorption on the surface and has excellent corrosion resistance. Can be formed. Further, in the cell body 1 and the like, it is preferable to passivate portions to be contacted by the gas to be measured, such as an electric field polishing process or a chromium oxide coating process. The same material as that of the cell body 1 is usually used for the two flanges 6 and 7, but the flange 6 is preferably one that can be integrated with the cell body 1 by welding (welding) or the like. If there is no problem, various materials can be used in appropriate combination. Further, the heating means 5 may be a normal heating wire and a heat insulating material, a rubber heater, or the like. Further, the same heating means can be provided in the flange portion and the like as necessary.

The translucent window material 2 is made of a glass material such as ordinary glass, ordinary optical glass for visible region (for example, BK-7), quartz glass, sapphire or the like, or ceramic such as CaF ₂ . Various kinds of insulators can be used as long as they are light-transmitting materials having no catalytic action on the surface. The angle at which the translucent window material 2 is set is 56 when the axis of the cell body 1 and the axis of the translucent window material 2 are, for example, quartz glass.
It is set at an angle called the Brewster angle that crosses in degrees. This Brewster angle
This is an angle at which light reflection can be reduced, and is suitably used for a measurement cell for spectroscopic analysis.

The gas inlet 3a of the gas inlet tube 3
The gas outlet of the gas outlet pipe 4 is located at a position where the axis of the pipe is oriented toward the center of the translucent window material 2 and three axes including the axis of the cell body 1 are present on one plane. It is provided in. By forming in this manner, the gas to be measured introduced into the cell main body 1 from the gas introduction pipe 3 is transmitted through the translucent window material 2.
After the reflection, the gas can flow into the cell body 1 in the axial direction, so that the gas flow can be formed smoothly and the temperature unevenness can be reduced. Further, by forming the inlet / outlet as described above, gas accumulation at both ends of the cell body 1 can be almost eliminated.

An inner O-ring 8 for supporting the translucent window material 2
Is made of a rubber material such as viton rubber or fluorine rubber or a metal C-ring. The outer cushioning material 9 presses the light-transmitting window material 2 evenly against the flange 6 via the O-ring 8. In addition, it is formed of a material having appropriate elasticity so that stress due to thermal expansion or the like can be absorbed.

In this embodiment, as the cushioning material 9,
A rubber heater having a predetermined ring shape is used. This rubber heater is a heating element in which a heating wire is embedded in a rubber-based material having appropriate elasticity and heat resistance, and heat is generated by supplying power from a heater wire 11 connected to the rubber heater. It is formed so that.

As described above, by using a rubber heater having a predetermined elasticity instead of a normal rubber cushioning material as the cushioning material 9, the light-transmitting window material 2 is directly heated by the cushioning material 9. Since the heating temperature (heating ability) of the translucent window material 2 can be set separately from the heating temperature of the cell body 1 by the heating means 5, the cell body 1 and the translucent window material 2 can be set to a predetermined temperature. It can be reliably heated to the temperature.

As a result, the gas can be prevented from being condensed in the translucent window member 2, the gas can be prevented from being decomposed in the cell body 1, and the analysis of the gas containing the condensed component and the decomposed component can be performed accurately. The analysis of trace components in the special gas used in the semiconductor manufacturing field can be performed reliably.

FIG. 2 is a sectional view of a main part showing a second embodiment of the present invention. In this embodiment, a normal cushioning material 9 is used outside the translucent window material 2, and a ring-shaped heater 12 is provided on the inner peripheral side of the cushioning material 9.
2 is pressed against the outer surface of the translucent window material 2 by the holding metal 13. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted.

The heater 12 has a size (diameter) avoiding a portion of the translucent window material 2 through which the measurement light passes, and is capable of heating the translucent window material 2 to a predetermined temperature range. It can be formed in a shape. Further, as the heater 12, a heating wire can be directly provided on the surface of the translucent window material 2, and a heater in which the heating wire is covered with a heat-resistant insulating material can be used.

FIG. 3 is a sectional view of a main part showing a third embodiment of the present invention. In the present embodiment, a spring 14 is interposed in the presser fitting 13 in the second embodiment, and the heater 14 is uniformly pressed against the outer surface of the translucent window material 2 by the spring 14. That is, when the heater 12 is directly pressed by the holding metal 13, there is a possibility that the light-transmitting window material 2 may be distorted or the airtightness between the O-ring 8 and the O-ring 8 may be deteriorated due to the balance of the pressing amount. By interposing a spring 14 in the heater 12, distortion can be prevented, and the dimensional accuracy of the heater 12 can be reduced.

FIG. 4 is a sectional view of a main part showing a fourth embodiment of the present invention. The heating means 15 shown in the present embodiment is configured such that a carbon film, a tungsten film, a SnO ₂ film (transparent conductive film) is formed on the outer periphery of the measurement light passage portion 16 in the translucent window material 2 by vacuum evaporation, sputtering, CVD, or the like. And the heater wire 11 is connected to both ends. As described above, by forming a film having a heat-generating property integrally with the translucent window material 2 as the heating means 15, the translucent window material 2 can be easily mounted on the cell body 1. Note that the outer surface side of the heating means 15 may be covered with a suitable heat insulating material.

In each embodiment, a temperature detecting means such as a thermocouple is provided on each of the cell body 1 and the translucent window member 2, and the temperature control means and the power control sections of both the heating means are appropriately combined. Accordingly, the entire measurement cell can be efficiently heated and maintained at a predetermined temperature. The cell body 1
And the translucent window material 2 do not necessarily need to be heated to the same temperature, the cell body 1 is heated to a range where the components that decompose at high temperatures are not decomposed, and the translucent window material 2 is It is sufficient to heat the material 2 to a temperature at which the components which may be condensed do not condense and adhere by direct heating by the heating means provided on the material 2 and heat conduction from the cell body 1.

Therefore, when analyzing a gas containing a component that condenses at room temperature and decomposes at a high temperature, it is necessary to heat each part to an appropriate temperature according to the condensation temperature and decomposition temperature of various components contained in the gas. As a result, condensation and decomposition of gas components do not occur, and accurate spectroscopic analysis can be performed. Further, since it is not necessary to heat the cell main body 1 more than necessary, the temperature difference in the temperature distribution of the entire measurement cell can be reduced, and the burden of metal or the like due to the temperature difference can be reduced.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Trimethylindium (TMIn) and phosphine (PH ₃ ) were used as starting materials by MOCVD.
When growing nP, the concentration of undecomposed TMIn in the exhaust gas discharged from the apparatus was measured by near-infrared spectroscopy. As the measurement cells, those having the configuration shown in FIG. 1 using a rubber heater as a buffer material (Example cells) and those using a normal rubber cushion material (Comparative Example cells) were used. In addition,
The cell body and each flange were made of SS316, and the cell body was 50 cm long and 20 mm inside diameter. In addition, a transparent quartz glass having a thickness of 10 mm was used for the translucent window material.

The light-transmitting window material was heated to 100 ° C. so that the by-product phosphorus (P ₂ , P ₄ ) contained in the exhaust gas was not condensed and adhered to the light-transmitting window material. As a result, FIG.
In the case of the example cell, when the temperature of the central portion C of the cell body is about 120 ° C., the translucent window material portions A and B on both sides become 100 ° C. as shown in FIG. TM
The concentration of TMIn could be accurately measured without decomposition of In. On the other hand, in the case of the cell of the comparative example, the temperature of the central portion C of the cell body had to be 200 ° C. in order to heat the translucent window material portions A and B to 100 ° C. Since TMIn starts to decompose at about 130 ° C,
TMIn was decomposed during heating, and phosphorus adhered to the light-transmitting window material, so that accurate measurement could not be performed.

[0026]

As described above, according to the measuring cell for spectroscopic analysis of the present invention, the cell body and the translucent window material can be heated to a predetermined temperature. A specific component in a gas containing a component having a small difference can be accurately measured by spectroscopic analysis.

[Brief description of the drawings]

FIG. 1 is a partially sectional front view showing a first embodiment of a measurement cell for spectroscopic analysis of the present invention.

FIG. 2 is a sectional view of a main part showing a second embodiment of the measuring cell.

FIG. 3 is a sectional view of a main part showing a third embodiment of a measuring cell.

FIG. 4 is a sectional view of a main part showing a fourth embodiment of a measuring cell.

FIG. 5 is a diagram showing a temperature distribution of a measurement cell.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cell main body, 2 ... Translucent window material, 3 ... Gas introduction pipe, 3a
... gas inlet, 4 ... gas outlet pipe, 5 ... heating means, 6 ... fixed flange, 7 ... holding flange, 8 ... O-ring, 9 ... cushioning material, 10 ... bolt, 11 ... heater wire, 12 ... heater, 13 … Holding bracket, 14… Spring

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Isao Matsumoto 1-16-7 Nishi-Shimbashi, Minato-ku, Tokyo Nippon Sanso Corporation

Claims (3)

[Claims] 1. A spectroscopic measurement cell comprising a tubular cell body having a gas inlet at one end and a gas outlet at the other end, and a translucent window material attached to both ends of the tubular cell body. And a means for heating the light-transmitting window material. 2. The heating means for heating the light-transmitting window material comprises a ring-shaped buffer for mounting the light-transmitting window material on the tubular cell body as a heating element. The measurement cell for spectroscopic analysis according to claim 1. 3. The measurement for spectroscopic analysis according to claim 1, wherein the means for heating the translucent window member is a heating element deposited in a ring shape on the surface of the translucent window member. cell.