JP2008268012A - Fine particle scattered light measuring method and measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for irradiating fine particles with a laser light, and measuring the scattering light; to improve a method for measuring a polysilane contained in an exhaust gas from a CVD apparatus; and to provide a method for measuring the flow and concentration of the polysilane either in plane surface or stereoscopically to obtain a distribution. <P>SOLUTION: The method includes irradiating the fine particle with the laser light and measuring its scattering light and measures the scattering light, as the laser light is scanned by an optical system having at least a polygon mirror or a galvanometer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fine particle scattered light measurement method in which fine particles are irradiated with laser light and the scattered light is measured, and more specifically, fine particle scattered light measurement is performed to measure fine particles called polysilane contained in exhaust gas generated inside a CVD apparatus. The present invention relates to a method and a fine particle scattered light measurement apparatus.

  With the increase in semiconductor products, it is desired to increase the throughput of semiconductor manufacturing equipment. For example, in a CVD apparatus (a plasma CVD apparatus, a thermal CVD apparatus, a photo CVD apparatus, etc.) that is one of typical semiconductor manufacturing apparatuses, a device such as increasing the film forming speed is required in order to increase the throughput. In a CVD apparatus using a gas containing silicon atoms as a source gas, fine particles called polysilane are generated as a by-product in the CVD apparatus during film formation. And it deposits in the film-forming chamber inside a CVD apparatus, or an exhaust pipe. Such fine particles contaminate the semiconductor film and cause problems such as a decrease in yield and an increase in exhaust resistance. As a result, frequent maintenance is required, that is, downtime increases. Furthermore, these fine particles are ignited easily and need to be handled with care.

  In response to the above problems, attempts have been made to visualize the generation state of polysilane by irradiating polysilane with laser light and detecting the scattered light. By visualizing the polysilane when the polysilane is produced, the relationship between the film deposition conditions and the fine particle deposition, or the fine particle size is analyzed. Then, the substance of the fine particle deposition is grasped by a method of directly measuring or observing the polysilane when the polysilane is generated, and as a result, the downtime is shortened.

  Examples thereof include Patent Document 1, Patent Document 2, Patent Document 3, Non-Patent Document 1, Non-Patent Document 2, and the like. An example of measurement of fine particle scattered light using conventional laser light described in such a document will be described with reference to FIG.

  In FIG. 2, reference numeral 201 denotes a vacuum container, the inside of which is decompressed, and a gas used for film deposition is introduced from a gas supply port 202. Reference numeral 203 denotes a gas flow. The gas flow 203 passes through the vacuum vessel 201 and is exhausted by a vacuum exhaust device (not shown) via a gas exhaust port 204. A discharge power source 210 includes a transmitter such as RF, VHF, and microwave and a matching box. Reference numeral 211 denotes a discharge electrode, which discharges and decomposes the gas in the gas flow 203 with electric power from the discharge power supply 210, and forms a semiconductor film on a substrate disposed between, for example, two discharge electrodes. Reference numeral 213 denotes fine particles (so-called polysilane) obtained by polymerization in the air without forming a film among gases decomposed by discharge. Some of the fine particles 213 are exhausted via the exhaust port 204, but some are deposited on the inside of the vacuum vessel 201, the exhaust port 204, the discharge electrode 211, and further on the substrate. Reference numeral 220 denotes a light source that emits laser light. For example, a transmitter such as an argon (Ar) laser or a helium neon (He—Ne) laser is used. Reference numeral 221 denotes a laser beam that irradiates the vacuum vessel 201 via the laser introduction port 222. The laser light applied to the fine particles 213 generates scattered light 225. The scattered light 225 is measured or observed from the scattered light measurement / observation view port 226. Of course, in addition to visual observation, a variety of applications are possible by performing processing such as changing the scattered light into a signal using a photosensor or the like.

  However, in any of the methods proposed in any patent document or non-patent document, only the scattered light of polysilane passing through a part of the path through which the laser beam passes accidentally is observed. It was difficult to grasp the entire polysilane image.

  That is, the generation state and distribution state of the polysilane other than on the path where the laser beam is irradiated are still unclear, and it is difficult to analyze the polysilane generation mechanism and take appropriate measures.

  Even if the number of laser beams introduced is increased in order to solve such a problem, only a few scattered lights can be seen, and it is far from grasping the whole image of the generated polysilane.

  In Patent Document 4, a laser beam is roughly scanned in parallel (parallel scanning) to create a wide laser light irradiation region. Next, a fine particle measurement method is disclosed in which a fluid to be inspected is caused to flow in the laser light irradiation region, and the identification of a plurality of shapes and dimensions of the particles is measured from the light scattering and light diffraction patterns of the particles in the measurement field of the fluid. Yes. According to the present invention, it is possible to measure fine particles in a wide range by creating a wide laser light irradiation region. However, the invention described in Patent Document 4 has a problem that a lens system for scanning in parallel is separately required. Further, in the invention of Patent Document 4, although the laser beam scans a wide range, it is actually used for measuring the shape and dimensions of the particles, and the flow of the particles as a whole of the CVD apparatus is obtained. It was not a thing.

  That is, the invention described in Patent Document 4 is a concept of flowing a fluid to be inspected in a laser light irradiation region. Therefore, the idea of adjusting the laser irradiation region in accordance with the vacuum vessel having a complicated shape or the structure in the exhaust pipe is not disclosed.

  On the other hand, according to the knowledge of the present inventor, the polymerization reaction and the aggregation reaction of polysilane are the distance from the discharge (plasma), the size and shape of the gas channel, the pressure in the channel, the temperature of the wall surface, the flow rate, It varies greatly depending on gas stagnation. On the other hand, in the invention of Patent Document 4, it is difficult to grasp how polysilane is generated, flows, and deposited in the entire CVD apparatus.

Therefore, there is a need for an apparatus that visualizes polysilane generated in a CVD apparatus in a planar or three-dimensional manner with a simpler apparatus.
JP-A-5-34259 JP 9-259246 A JP 2000-180345 A JP 2001-264232 A The 6th PVTEC Technical Report Meeting-FY2004 Interim Report-Mitsubishi Electric's report "Development of Silicon Crystalline Thin-Film Solar Cell Module Manufacturing Technology" (Simultaneous in situ measurements of properties of properties in rf silane plasma usima a polarization-sensitive laser-light1.

  The present invention improves the method for measuring the scattered light by irradiating fine particles with laser light, more specifically, the method for measuring polysilane contained in exhaust gas in a CVD apparatus. It is another object of the present invention to provide a method by which the flow and concentration of polysilane can be directly measured or observed two-dimensionally or three-dimensionally and the distribution can be intuitively grasped. Moreover, it aims at providing the dress price for it. Furthermore, as a result, an object is to enable an optimal gas flow path design.

As a result of intensive investigations to achieve the above object, the present inventors have completed the present invention.
A method for irradiating fine particles with laser light and measuring scattered light scattered from the fine particles, wherein the scattered light is measured while scanning the laser light with an optical system having at least a polygon mirror or a galvanometer mirror. It is what.

  Furthermore, the present invention is characterized in that the fine particles include fine particles generated inside a CVD apparatus.

  Furthermore, the present invention is an apparatus for irradiating fine particles with laser light to measure scattered light, and includes a laser light scanning unit having at least a polygon mirror or a galvanometer mirror, and a detection unit for detecting the scattered light. It is a feature.

  Further, the present invention is characterized in that a reflecting means is further provided on the path of the laser beam after being reflected by the polygon mirror or the galvanometer mirror.

  Furthermore, the present invention is characterized in that the incident light to the reflecting means and the reflected light do not overlap.

  The generation situation of polysilane in the observation space, the flow and concentration of polysilane can be measured or observed directly in a plane or three-dimensionally, and the distribution can be accurately grasped. As a result, it is possible to design an optimal gas flow path.

  Further, a film formation condition with less generation of fine particles can be obtained from a correlation between the film formation condition and the generation condition of the fine particles.

  FIG. 1 shows a typical apparatus for carrying out the present invention. The apparatus shown in FIG. 1 is based on the apparatus shown in FIG. 2 and is improved in the part related to laser light irradiation, measurement or observation. Therefore, it is the same as that in FIG. 1 except for the optical system (optical components or configuration).

  In FIG. 1, reference numeral 101 denotes a vacuum container, the inside of which is decompressed, and a gas used for film deposition is introduced from a gas supply port 102. Reference numeral 103 denotes a gas flow. The gas flow 103 passes through the vacuum vessel 101 and is exhausted through a gas exhaust port 104 by a vacuum exhaust device (not shown). A discharge power source 110 includes a transmitter such as RF, VHF, and microwave and a matching box. Reference numeral 111 denotes a discharge electrode, which discharges and decomposes the gas in the gas flow 103 by the electric power from the discharge power supply 110, and forms a semiconductor film on, for example, a substrate disposed between two discharge electrodes. Reference numeral 113 denotes fine particles. Some of the fine particles 113 are exhausted through the exhaust port 104, but some are deposited inside the vacuum container 101, the exhaust port 104, the discharge electrode 111, and the like. Reference numeral 120 denotes a light source that emits laser light. For example, a transmitter such as an Ar laser or a He—Ne laser is used. Reference numeral 121 denotes a laser beam. Reference numeral 122 denotes a polygon mirror (rotating polyhedral mirror) that irradiates the inside of the vacuum vessel 101 via a laser light introduction port 123. As a result of the rotation of the polygon mirror 122, the laser beam scans as indicated at 124. The laser light applied to the fine particles 213 generates scattered light 125. The scattered light 125 is observed from the scattered light measurement / observation view port 126. In addition to visual observation, it can be used in various ways by performing processing such as changing the scattered light into a signal using a photo sensor or the like. When the flow of the entire fine particles is grasped, it is preferable to provide a detection unit such as a CCD or C-MOS sensor that can capture the light intensity two-dimensionally.

  FIG. 3 shows a top view of the scanning state of the laser beam scanning unit by the polygon mirror. In FIG. 3, 301 is a flow of fine particles, 302 is laser light, 303 is a polygon mirror, 304 is laser light scanned by a polygon mirror, and 305 is fine particles visualized by scanning laser light. Reference numeral 310 denotes a vacuum vessel wall, and 311 denotes a laser light introduction port. In FIG. 1, a scattered light measurement / observation viewport 126 is provided above the vacuum vessel 101 so that the particles 305 thus visualized can be measured at a large angle. Instead of the polygon mirror 304, a laser beam may be scanned as a laser beam scanning unit using a galvanometer mirror.

  When a polygon mirror is used for the laser beam scanning unit, an fθ lens may be used to make the scanning speed constant. This is particularly necessary when the illuminance during scanning is required to be constant, such as a laser beam printer. However, in the present invention, if the purpose is to know the whole image of the fine particles, it is sufficiently practical without using an fθ lens. Alternatively, as shown in FIG. 4, it is more effective to easily grasp the entire flow of fine particles by further expanding the visualization region using a mirror. In FIG. 4, 401 is a flow of fine particles, 402 is a laser beam, 403 is a polygon mirror, 404 is a scanning laser beam, 405 is a reflecting mirror, and 406 is a visualized fine particle. Reference numeral 410 denotes a vacuum vessel wall, and 411 denotes a laser beam introduction port. 4A is a top view and FIG. 4B is a cross-sectional view. As shown in the cross-sectional view, it is better to prevent the incident light and reflected light on the fixed mirror from overlapping. This is because if the incident light and the reflected light are on the same surface, there will be a place where the scattered light due to the fine particles is generated twice and a place where it is generated only once, which is inappropriate for knowing the overall light and shade. . Note that the members indicated by the numbers used in the cross-sectional view of FIG. 4B are the same as those in FIG.

  FIG. 5 schematically shows an example in which the fine particles visualized two-dimensionally in this way are observed. 501 is a flow of fine particles, 502 is a laser beam, 503 is a polygon mirror, and 504 is a scanning laser beam. 505a is a visualized fine particle having a large scattered light intensity, and 505b is a visualized fine particle having a small scattered light intensity. The fine particles visualized by the scattered light as described above flow to the right in the figure as a whole, but appear as three streaks. This is presumably because the gas from the gas supply port 506 is actually ejected from the three small gas blowing holes 507, and more fine particles are generated in a place where the raw material gas concentration is high. From these facts, a guideline for designing the apparatus is obtained in which the intervals between the gas blowout holes 507 are arranged so that the streaks of the scattered light intensity are not recognized when the fine particles are visualized. Reference numeral 508 denotes a discharge electrode, 510 denotes a vacuum vessel wall, and 511 denotes a laser light introduction port.

  FIG. 7 shows an example in which a lens is added to an optical system, which is a typical apparatus for carrying out the method for measuring fine particle scattered light of the present invention. In FIG. 7, reference numeral 701 denotes a cylindrical concave lens, and the incident spot laser beam 702 is enlarged only in one cross section to have a fan-shaped light shape as indicated by 703. Reference numeral 704 denotes a cylindrical convex lens, which converts the laser beam spreading in a fan shape into substantially parallel light as indicated by 705. Next, reference numeral 706 denotes a polygon mirror, which scans the incident substantially parallel laser beam 705 so as to become a triangular prism-shaped laser beam as indicated by 707. Reference numeral 708 denotes a convex lens. Further, a laser beam is formed into a rectangular parallelepiped laser beam as indicated by 709.

  In the case of such a rectangular parallelepiped laser light irradiation region, all the fine particles crossing the rectangular parallelepiped can be measured, so that the density of the laser scattered light by the fine particles in the film forming apparatus can be grasped three-dimensionally. As a result, the flow of fine particles can be intuitively grasped. However, since the number of parts forming the optical system increases, it is desirable to use them as necessary.

  Examples of the method for measuring fine particle scattered light and the apparatus for measuring fine particle scattered light of the present invention are shown below, but the configuration of the present invention is not limited to the following examples.

Example 1
The fine particle scattered light measuring apparatus of the present invention is performed using the fine particle scattered light measuring apparatus of the present invention described above with reference to FIG. Although the apparatus used in this embodiment has the same basic part as that of FIG. 1 described above, the parts corresponding to the gas supply port 506 and the gas blowing hole 507 shown in FIG. ing. Some parameters when implemented are described below.

  The typical ones of the apparatus and conditions used in this embodiment are described below.

  As the vacuum container 101, a container having internal dimensions of a width of 0.8 m, a depth of 0.5 m, and a height of 0.4 m is used as a rough numerical value.

  The gas is supplied from a gas cylinder (not shown), and is supplied from the gas supply port 102 into the vacuum vessel 101 via a decompressor and a flow rate controller (mass flow controller) (not shown). The structure of the gas supply port 102 is the same as that of the gas supply port 506 and the gas blowing hole 507 shown in FIG.

The raw material gas flow rate is SiH ₄ : 350 sccm (cm ³ / min (standard state))
H ₂ : 3000 sccm (cm ³ / min (standard state))
SiF ₄ : 200 sccm (cm ³ / min (standard state))
It was.

  Gas exhaust is adjusted using a vacuum pump (not shown) so that the inside of the vacuum vessel is about 1000 Pa.

  Next, a 60 MHz VHF power supply is used as the discharge power supply. An electric power of 1.5 kW is applied to a parallel plate electrode having a substantially 25 cm square through a matching box and discharged.

  The gas blowing hole is provided with three φ5 mm holes at 10 cm intervals so that the central hole comes to the center with respect to the 25 cm long electrode.

  A helium neon laser with an output of 20 mW is used as a light source for transmitting laser light. The polygon mirror is a hexahedron with a rotational speed of 20000 rpm.

  The fine particles measured under the above conditions have a scattering intensity distribution as shown in FIG. As described above, depending on the arrangement of the gas blowing holes, it is considered that the concentration of fine particles is generated and the corresponding light and shade can be observed.

  Next, a gas supply port with a newly reduced interval between the gas blowing holes is produced, and the above-described gas supply port is replaced, and an experiment similar to the above is performed. As specific dimensions, the hole diameter is 1.5 mm, and the distance is 2.5 cm. As a result of the measurement, it is considered that the intensity of scattered light is not visually observed and the unevenness of the generation of fine particles is substantially reduced.

(Example 2)
A similar experiment is performed by changing the polygon mirror 122 of the laser beam scanning unit to a galvanometer mirror in the fine particle measurement method performed in the first embodiment. The galvanometer mirror scans 10 times per second at a deflection angle of 25 °. As a result, as compared with the case of using a polygon mirror by visual observation, although the scanning speed is lowered, the measurement is intermittent, but the same intensity of scattered light intensity as that observed in Example 1 is observed. . The galvanometer mirror is more suitable when deciding the mirror angle and observing a specific place in a bright state.

(Example 3)
The fine particle scattered light measuring method of the present invention is performed using the fine particle scattered light measuring apparatus of the present invention described above with reference to FIG. However, in addition to the structure shown in FIG. 1, a reflecting mirror shown by 405 in FIG. 4 is added. All other experimental parameters are the same as in Example 1, and the parts corresponding to the gas supply port 506 and the gas blowing hole 507 shown in FIG.

  As a result of the experiment, as shown in FIG. 4, as the scanning range of the laser beam is expanded by the reflecting mirror, the places where the scattered light can be visualized are expanded. Then, the scattered light intensity can be intuitively grasped over a wide range as shown in FIG. In FIG. 6, 601 is the flow of fine particles, 602 is a laser beam, 603 is a polygon mirror, and 604 is a scanning laser beam. Reference numeral 605a denotes a portion where the scattered light intensity of the visualized fine particles is large, and reference numeral 605b denotes a portion where the scattered light intensity of the visualized fine particles is low. 606 is a gas supply port, 607 is a gas blowing hole, 608 is a discharge electrode, 609 is a reflecting mirror, 610 is a wall of a vacuum vessel, and 611 is a laser light introduction port. Also in this embodiment, the intensity of scattered light intensity that is considered to correspond to the gas blowing hole 607 is observed.

Typical apparatus for carrying out the method for measuring fine particle scattered light of the present invention Example of a device that measures fine particle scattered light using conventional laser light The figure which shows a mode that a laser beam is scanned by a polygon mirror A figure showing how laser light is scanned by a polygon mirror and then reflected by a reflecting mirror The conceptual diagram which shows the light and shade of scattered light intensity when measuring the fine particle in a CVD apparatus using the fine particle scattered light measuring method of this invention Another example of a conceptual diagram showing the intensity of scattered light intensity when measuring fine particles in a CVD apparatus using the fine particle scattered light measurement method of the present invention Typical apparatus for carrying out the method for measuring fine particle scattered light of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Vacuum vessel 102 Gas supply port 103 Gas flow 104 Gas exhaust port 110 Discharge power supply 111 Discharge electrode 112 Discharge 113 Fine particle 120 Laser 121 Laser light 122 Polygon mirror 123 Introduction port of laser light 124 Scanning laser light 125 Scattered light 126 Scattered light measurement / View port for observation 201 Vacuum container 202 Gas supply port 203 Gas flow 204 Gas exhaust port 210 Discharge power supply 211 Discharge electrode 212 Discharge 213 Particle 220 Laser 221 Laser beam 222 Laser beam introduction port 225 Scattered light 226 View for scattered light measurement / observation Port 301 Flow of fine particles 302 Laser light 303 Polygon mirror 304 Scanning laser light 305 Visualized polysilane 310 Wall of vacuum vessel 311 Laser light introduction port 401 Particle flow 402 Laser beam 403 Polygon mirror 404 Scanning laser beam 405 Reflector 406 Visualized particle 410 Vacuum vessel wall 411 Laser beam introduction port 501 Particle flow 502 Laser beam 503 Polygon mirror 504 Scanning laser beam 505a Visualized particle ( (Spot with high scattered light intensity)
505b Visualized fine particles (locations with small scattered light intensity)
506 Gas supply port 507 Gas blowout hole 508 Discharge electrode 510 Wall of vacuum vessel 511 Laser light introduction port 601 Flow of fine particles 602 Laser light 603 Polygon mirror 604 Scanning laser light 605a Visualized fine particles (location with large scattered light intensity)
605b Fine particles visualized (locations with small scattered light intensity)
606 Gas supply port 607 Gas blowout hole 608 Discharge electrode 609 Reflective mirror 610 Vacuum vessel wall 611 Laser light introduction port 701 Cylindrical concave lens 702 Incident spot laser beam 703 Fan-shaped laser beam 704 Cylindrical convex lens 705 Substantially parallel laser beam 706 Polygon mirror 707 Triangular prism-shaped laser beam 708 Convex lens 709 Rectangular laser beam

Claims (6)

A method of irradiating fine particles with laser light and measuring scattered light scattered from the fine particles,
A method for measuring scattered light of fine particles, comprising: measuring scattered light while scanning laser light with an optical system having at least a polygon mirror or a galvanometer mirror.   The fine particle scattered light measuring method according to claim 1, wherein the fine particles include fine particles generated inside a CVD apparatus. A device that irradiates fine particles with laser light and measures scattered light, and a light source that emits laser light;
A laser beam scanning unit having at least a polygon mirror or a galvanometer mirror;
A detector for detecting the scattered light;
A fine particle scattered light measuring apparatus comprising:   The fine particle scattered light measuring apparatus according to claim 3, wherein the fine particles include fine particles generated inside a CVD apparatus.   4. The fine particle scattered light measuring apparatus according to claim 3, further comprising a reflecting means on a path of the laser light after being reflected by the polygon mirror or the galvanometer mirror.   6. The fine particle scattered light measuring apparatus according to claim 5, wherein the incident light to the reflecting means and the reflected light do not overlap each other.

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