JP2008298528A - Optical film thickness monitor and coating device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film thickness monitor which is suitable for aerosol deposition (AD method) and is used for on-the-spot measurement, and to provide a coating device that uses the same. <P>SOLUTION: This optical film thickness monitor is used for a coating device, wherein ultrafine-particle brittle materials supplied onto a substrate 49, are loaded with a mechanical impact force to cause the brittle materials to join to each other, and a compact is formed. White light is inputted into the compact from an end face of a measuring probe 410, to measure the reflectance spectra coming from the compact, and the film thickness and reflectance of the compact are derived from the interfering state of the reflectance spectrum, under conditions where the wavelength band of the reflectance spectrum is larger than the particle diameters of the brittle materials. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical film thickness monitor of a film forming apparatus for forming a compact by applying a mechanical impact force to an ultra fine particle brittle material supplied on a substrate and bonding the ultra fine particle brittle material, and a composition using the same. The present invention relates to a membrane device.

  As a new oxide film formation technique, aerosol deposition (hereinafter referred to as AD method) using a normal temperature impact solidification phenomenon has been developed. The AD method utilizes the impact adhesion phenomenon of ultrafine particle materials. Compared to conventional thin film formation methods, high film formation speed and low process temperature are expected (see Jun Akedo and Maxim Lebedev: Jpn. J. Appl. Phys. 38 (1999) 5397.) ). In addition, since the AD method does not depend on the underlying layer, the substrate can be freely selected.

  The technique disclosed in Japanese Patent Application Laid-Open No. 2001-3180 (Patent Document 1) is a method for forming an AD method, in which ultrafine particles are crushed by applying a mechanical impact to an ultrafine particle brittle material supplied onto a substrate. It is characterized in that the brittle materials or the ultrafine particle brittle material and the substrate are joined. As a result, bonding between ultrafine particles is realized, and a high-density and high-strength film is formed without applying heat.

  Studies on thin film forming of highly transparent electro-optic materials using the AD method have been made (Masafumi Nakada, Keishi Ohashi and Jun Akedo: J. of Crys. Growth, 275 (2005) e1275. (Non-patent Document 2) reference). According to this, the transmission loss of the AD film (film formed by the AD method), which is a basic characteristic of the optical element, is due to Rayleigh scattering of the fine particles forming the compact and the non-molded fine particles having different refractive indexes. It has been made clear.

  The technique disclosed in Japanese Patent Laid-Open No. 2005-181995 (Patent Document 2) relates to an optical element, an optical integrated device, an optical information propagation system, and a method for manufacturing the same by an AD method. Specifically, an optical element in which a compact is formed by impact solidification phenomenon in which an ultrafine particle brittle material supplied on a substrate is loaded with a mechanical impact force to pulverize and join the ultrafine particle brittle material. D6 / λ4 between the average radius d (nm) of the portion where the refractive index of pores (holes), heterogeneous phases, etc. is different from the main constituent of the molded body and the wavelength λ (nm) of the light propagating through the molded body It is characterized by <4x10-5 nm2. In the AD film formation method, the carrier gas and the raw material powder are mixed in an aerosol generator to form an aerosol, and the aerosol is sprayed onto the substrate from the nozzle due to the pressure difference between the aerosol generator and the film formation chamber. A thin film is formed. In order to generate a pressure difference, the film forming chamber is evacuated by a vacuum pump.

  On the other hand, in a thin film forming apparatus, film formation is generally performed while monitoring the film thickness in order to control the film thickness. In the vapor deposition method or the like, a method using a crystal resonator is widely used. This utilizes the fact that the natural frequency changes depending on the mass of the film formed on the surface of the crystal unit. In the vapor deposition method, since a thin film is formed in the entire area in the film formation chamber, a crystal resonator monitor is installed in the vicinity of the substrate, thereby utilizing the fact that the thickness of the monitor and the thickness of the substrate are proportional. As an optical film thickness monitor, a system using an interference effect and a system using ellipsometry are used. Japanese Laid-Open Patent Publication No. 7-280520 (Patent Document 3) proposes a method for measuring the thickness of a thin film by irradiating a thin film with white light and measuring the spectral intensity of interference light.

Jun Akedo and Maxim Lebedev: Jpn. J. Appl. Phys. 38 (1999) 5397. Masafumi Nakada, Keishi Ohashi and Jun Akedo: J. of Crys. Growth, 275 (2005) e1275. JP 2001-3180 JP 2005-181995 gazette JP 7-280520 A

  In order to form an optical element using the AD method, it is necessary to accurately control the thickness of the thin film. For this purpose, a film thickness monitor for in-situ measurement of the film thickness is necessary for the film deposition apparatus of the AD method, but it is difficult to cope with the film thickness monitor attached to a normal film deposition apparatus. This is due to the following reason.

  That is, in the AD method, since the film formation region is limited by the nozzle, the proportional relationship between the film thickness required for the crystal oscillator type monitor and the film thickness on the substrate cannot be guaranteed. Further, since the fine particles are ejected at a high speed, it is considered that the natural frequency is affected.

  As for the optical type, the surface roughness of the AD film is several hundred nm, so that the optical uniformity is inferior. In order to spray aerosol onto the substrate, the raw material powder moves in the film forming chamber and obstructs the optical path. .

  Accordingly, the present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide an in-situ optical film thickness monitor suitable for aerosol deposition (AD method) and the use thereof. It is to provide a film forming apparatus.

  In order to achieve the above object, in the present invention, an optical film thickness of a film forming apparatus for forming a molded body by applying a mechanical impact force to an ultrafine particle brittle material supplied onto a substrate to join the ultrafine particle brittle material. The monitor is configured such that white light is incident on the molded body from the end face of the measurement probe, the reflectance spectrum from the molded body is measured, and the wavelength range of the reflectance spectrum is larger than the particle size of the ultrafine brittle material. The film thickness and refractive index of the molded body are derived from the interference state of the reflectance spectrum under a long condition.

  The reflectance spectrum in the wavelength range longer than the particle size of the ultrafine particle brittle material contains information reflecting the optical interference of the thin film formed by aerosol deposition (AD method), and this reflection spectrum is analyzed. Thus, the film thickness and the refractive index can be obtained and used as a film thickness monitor.

  Further, it is preferable to have means for ejecting gas from the peripheral portion of the measurement probe so that the ultrafine particle brittle material does not adhere to the end face of the measurement probe. By ejecting gas from the periphery of the measurement probe, it is possible to prevent the raw material powder from adhering to the probe tip.

  Alternatively, a gas may be blown to the tip of the measurement probe so that the ultrafine particle brittle material does not adhere to the end face of the measurement probe. By spraying gas on the tip of the measurement probe, it is possible to prevent the raw material powder from adhering to the probe tip.

  Alternatively, a means for heating the measurement probe may be provided so that the ultrafine particle brittle material does not adhere to the end face of the measurement probe. By heating the measurement probe, it is possible to prevent the raw material powder from adhering to the probe tip.

  Further, the film forming apparatus of the present invention has a film forming chamber, and a fine particle trap is installed in the film forming chamber so that the fine particles do not float in the film forming chamber, so that the optical path is not obstructed by the fine particles. A film thickness monitor is installed in the film forming chamber. A fine particle trap is installed to prevent fine particles from floating in the film formation chamber, and a film thickness monitor is installed so that the optical path is not obstructed by the fine particles, thereby preventing the raw material powder from adhering to the tip of the measurement probe. .

  Moreover, it is preferable that the film forming apparatus has an aerosol generator, and the aerosol concentration of the aerosol generator is controlled by a signal generated by the film thickness monitor. In order to control the film thickness, it is necessary to control the amount of aerosol applied to the substrate by a signal obtained by the film thickness monitor. By controlling the aerosol concentration of the aerosol generator, the irradiation amount of the raw material particles can be controlled, and an AD method film forming apparatus capable of controlling the film thickness can be provided.

  The film forming apparatus includes a film forming chamber, and the film forming chamber includes an aerosol ejection nozzle and a shutter provided between the substrate and the aerosol ejection nozzle, and a signal generated by the film thickness monitor. It is preferable to control the film thickness of the molded body by operating the shutter. An AD method film forming apparatus capable of controlling the film thickness by opening and closing the shutter can be provided.

Furthermore, the film forming apparatus of the present invention includes:
Aerosol generating means for generating an aerosol in which fine particles of raw material powder are dispersed in a gas;
A film forming chamber having a nozzle for forming a thin film on the substrate by spraying fine particles supplied from the aerosol generating unit on the substrate, and a film thickness monitoring unit installed in the vicinity of the nozzle;
A light source connected to the film thickness monitoring means;
A spectrometer connected to the film thickness monitoring means;
Control means connected to the spectrometer,
White light from the light source is guided to the film thickness monitoring means and applied to the thin film formed on the substrate, and reflected light from the thin film is incident on the film thickness monitoring means and is guided to the spectroscope. The spectrum is measured, and the film thickness of the thin film is derived by analyzing the reflectance spectrum with the control means under the condition that the wavelength range of the reflectance spectrum is longer than the particle size of the fine particles. And

  Here, the aerosol generating means is provided with a vibrating means, and it is preferable to generate the aerosol by vibrating the vibrating means.

  Further, it is preferable that the control means sends a signal for stopping the vibration means to the vibration means when the film thickness of the thin film reaches a set value, thereby stopping the formation of the thin film.

  Here, the film formation chamber is preferably evacuated to a predetermined degree of vacuum by a vacuum pump.

  The monitoring means and the light source are preferably connected by an optical fiber.

  Here, the film thickness monitoring means preferably includes an irradiation fiber for irradiating the white light, a reading fiber for reading the reflected light, and a gas ejection part for ejecting gas. .

  Also, a fine particle trap is installed in the film forming chamber so that the fine particles do not float in the film forming chamber, and the film thickness monitoring means is installed in the film forming chamber so that the optical path is not obstructed by the fine particles. It is preferable.

  Further, a shutter provided between the substrate and the nozzle is installed in the film forming chamber, and the film thickness of the thin film is reduced by operating the shutter with a signal generated by the film thickness monitoring means. It is preferable to control.

  According to the present invention, it is possible to provide an in-situ film thickness monitor suitable for aerosol deposition (AD method). Furthermore, by using the film thickness monitor, a film forming apparatus in which the film thickness is controlled can be provided.

  Hereinafter, embodiments of the present invention including the principle of the present invention will be described in detail with reference to the drawings.

  The present invention has been made based on the discovery that the film thickness and refractive index can be calculated from the interference state of the reflectance spectrum in a region having a wavelength longer than the particle size of the aerosol raw material powder.

  FIG. 1 is a reflectance spectrum of an AD film (a film formed by an aerosol deposition (AD method) AD method) formed on a glass substrate.

  The reflectance spectrum was measured with an arrangement of 5 degrees incidence. PZT with a particle size of 600 nm is used as the raw material powder. As the measurement wavelength increases, the reflectivity increases monotonically, and the vibration of the reflectivity due to interference is measured at a wavelength of 700 nm or more. By analyzing this interference state with a normal optical model, the film thickness and the refractive index can be obtained.

  FIG. 2 is a reflectance spectrum of an AD film using PZT having a particle diameter of 0.7 μm as raw material powder formed on a glass substrate.

  In this case as well, the reflectance increases monotonously with the increase in the measurement wavelength, and the vibration of the reflectance due to interference is measured at a wavelength of 800 nm or more.

  FIG. 3 shows a cross-sectional SEM photograph (a) and a surface SEM photograph (b) of the AD film.

  It can be seen that irregularities having the same particle diameter as the raw material powder are observed on the surface of the AD film. In the AD method, it is thought that the raw material particles are crushed at the time of collision with the substrate and are firmly bonded between the particles and between the substrate particles. However, it is considered that there are particles on the film surface that have not been sufficiently crushed. It is done. These particles generate optical scattering. Since the optical scattering increases as the size of the scatterer becomes larger than the wavelength, the optical scattering decreases as the wavelength increases. Thereby, it is considered that the reflectance increases monotonously with the wavelength. Therefore, in order to measure the optical interference of a thin film formed by the AD method and use it as a film thickness monitor, measuring a spectral spectrum in a wavelength region equal to or larger than the particle diameter is used as a film thickness monitor of an AD method film forming apparatus. It is effective to use.

  As described above, the spectral spectrum of a thin film having a wavelength longer than the particle diameter of the aerosol raw material powder is measured, and the film thickness and refractive index can be calculated from the interference state. By applying this result, it is possible to realize an optical film thickness monitor for an AD film forming apparatus.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Example 1
FIG. 4 is a schematic view of a film forming apparatus using the film thickness monitor of the present invention.

  A gas cylinder 40 containing oxygen gas is connected to a glass bottle 41 via a transfer tube. After the powder raw material 42 is put into the glass bottle 41 and evacuated to a vacuum of about 20 Torr through the exhaust pipe 43, it is introduced while controlling the flow rate of oxygen as a carrier gas. The glass bottle 41 is vibrated by the vibrator 44 to generate an aerosol in which fine particles of the raw material powder are dispersed in a gas, and the carrier gas is transported to the film forming chamber 46 through the transport pipe 45.

  The film formation chamber 46 is evacuated to a predetermined degree of vacuum by a vacuum pump 47. A thin film is formed by spraying powder onto the substrate 49 from the nozzle 48. A film thickness monitor probe 410 is installed beside the nozzle 48. An optical fiber 411 is connected to the film thickness monitor probe 410 to guide the white light from the light source 412. The white light emitted from the film thickness monitor probe 410 is incident on the thin film formed on the substrate 49, and the reflected light is incident on the film thickness monitor probe 410. The reflected light enters the spectroscope 413 through the optical fiber 411, and the reflectance spectrum can be measured. The reflectance spectrum is analyzed by a personal computer (PC) 414 as a control means, and the film thickness is calculated. When the measured film thickness reaches the set value, a signal is transmitted from the PC 414, whereby the vibration exciter 44 is stopped and thin film formation is stopped.

  FIG. 5 is a schematic diagram of a cross-sectional shape of the film thickness monitor probe 410.

  The film thickness monitor probe 410 includes eight irradiation fibers 52 around one reading fiber 51 and a gas ejection portion 53 around the irradiation fibers 52.

  The film forming conditions are as follows. The carrier gas is oxygen, the gas flow rate is 12 l / min, the film forming speed is 0.5 μm / min, and the vibration frequency of the vibrator 44 is 200 rpm. Silicon was used for the substrate 49. The lead zirconate titanate (PZT) -based powder, which is an oxide with a large electro-optic effect, was used as the film forming material. The composition of PZT is x = 0.3 in Pb (ZrxTi1-x) O3. To increase transparency, 0.5at% of Mn is added. The average particle size of the raw material powder was 0.7 μm. During the film thickness monitoring, oxygen was ejected from the gas ejection part 53 at a gas flow rate of 0.5 l / min.

  FIG. 6 shows the reflectance spectrum. The spectrum measurement range is a wavelength range of 1000 nm to 2000 nm.

  As the measurement wavelength increases, the reflectance increases monotonously, and the vibration of the reflectance due to interference is measured. 61 shows the measured value and 62 shows the calculated value. The agreement between the two is very good. The film thickness obtained from the analysis was 2.29 μm and the refractive index was 2.394. The set value of the film thickness is 2.3 μm, which is almost the same.

  By ejecting gas from the periphery of the film thickness monitor probe 410 during film formation, adhesion of the raw material powder to the end face of the film thickness monitor probe 410 was prevented, and continuous measurement was possible.

  From the above, by measuring the reflectance spectrum in the region where the wavelength is longer than the particle size of the aerosol raw material powder, the film thickness and refractive index can be calculated from the interference state, and gas is ejected from the vicinity of the probe end surface. In this way, it is possible to monitor the film thickness during film formation.

  The raw material powder adhesion prevention method of the present embodiment is a gas ejection method from the vicinity of the end face of the film thickness monitor probe 410, but has the same effect on the spraying of gas to the tip of the probe and the heating of the probe. Specifically, a mechanism for blowing gas to the tip of the film thickness monitor probe 410 may be provided so that the ultrafine particle brittle material does not adhere to the end face of the film thickness monitor probe 410. Alternatively, a mechanism for heating the film thickness monitor probe 410 may be provided so that the ultrafine particle brittle material does not adhere to the end face of the film thickness monitor probe 410.

(Example 2)
In this embodiment, a film forming apparatus using a fine particle trap and a film thickness monitor will be described.

  FIG. 7 is a schematic view of a film forming apparatus using a fine particle trap and a film thickness monitor according to the present invention.

  A gas cylinder 70 containing oxygen gas is connected to a glass bottle 71 through a transfer tube. A powder raw material 72 is placed in a glass bottle 71 and evacuated to a vacuum of about 20 Torr through an exhaust pipe 73, and then introduced as a carrier gas while controlling the flow rate of oxygen. The glass bottle 71 is vibrated by the vibrator 74 to generate an aerosol in which fine particles of the raw material powder are dispersed in the gas, and the carrier is transported to the film forming chamber 76 via the transport pipe 75.

  The film forming chamber 76 is evacuated to a predetermined degree of vacuum by a vacuum pump 77. A thin film is formed by spraying powder onto the substrate 79 from the nozzle 78. A film thickness monitor probe 710 is installed beside the nozzle 78. An optical fiber 711 is connected to the film thickness monitor probe 710 to guide white light from the light source 712. The white light emitted from the film thickness monitor probe 710 is incident on the thin film formed on the substrate 79, and the reflected light is incident on the film thickness monitor probe 710. The reflected light enters the spectroscope 713 through the optical fiber 711, and the reflectance spectrum can be measured.

  The reflectance spectrum is analyzed by a personal computer (PC) 714 as a control means, and the film thickness is calculated. When the measured film thickness reaches the set value, a signal is transmitted from the PC 414, whereby the shutter 715 moves between the nozzle 78 and the substrate 79, and the thin film formation on the substrate 79 is stopped. The raw material powder that has not contributed to the film formation is captured by the fine particle trap 716, and the raw material powder floating in the film forming chamber 76 is reduced.

  The film forming conditions are as follows. The carrier gas is oxygen, the gas flow rate is 12 l / min, the deposition rate is 0.5 μm / min, the incident angle of the raw material powder on the substrate 79 is 30 degrees, and the vibration frequency of the vibrator 74 is 200 rpm. Silicon was used for the substrate 79. The lead zirconate titanate (PZT) -based powder, which is an oxide with a large electro-optic effect, was used as the film forming material. The composition of PZT is x = 0.6 in Pb (ZrxTi1-x) O3. To increase transparency, 0.5at% of Mn is added. The average particle size of the raw material powder was 0.7 μm. During the film thickness monitoring, oxygen was ejected from the gas ejection section 53 (see FIG. 5) at a gas flow rate of 0.5 l / min.

  FIG. 8 shows the reflectance spectrum. The spectrum measurement range is a wavelength range of 1200 nm to 2000 nm. As the measurement wavelength increases, the reflectance increases monotonously, and the vibration of the reflectance due to interference is measured. The film thickness obtained from the analysis was 4.5 μm, and the refractive index was 2.40. The set value of the film thickness is 4.5 μm, which is almost the same.

  Since the raw material powder that has not contributed to the film formation is captured by the fine particle trap 716 and the raw material powder floating in the film formation chamber 76 is reduced, the adhesion of the raw material powder to the end face of the film thickness monitor probe 710 is prevented. Continuous measurement was possible.

  From the above, by measuring the reflectance spectrum of the region having a wavelength longer than the particle size of the aerosol raw material powder, the film thickness and refractive index can be calculated from the interference state, and the raw material powder that did not contribute to film formation is The trapping of the fine particles by the fine particle trap 716 prevents the fine particles from adhering to the end face of the film thickness monitoring probe 710, thereby making it possible to monitor the film thickness during film formation.

  According to the present invention, it is possible to provide an in-situ film thickness monitor suitable for the AD method. In addition, a film formation apparatus in which the film thickness is controlled using the film thickness monitor can be provided.

It is a figure which shows the reflectance spectrum (raw material powder particle size 600nm) of AD film formed on the glass substrate. It is a figure which shows the reflectance spectrum (raw material powder particle size 700nm) of AD film formed on the glass substrate. (A) is a cross-sectional SEM photograph of the AD film, and (b) is a surface SEM photograph of the AD film. It is the schematic of the film-forming apparatus using the film thickness monitor which concerns on Example 1 of this invention. It is a schematic diagram of the cross-sectional shape of a film thickness monitor probe. It is a figure which shows the reflectance spectrum (film thickness of 2.39 micrometers) of AD film formed on the silicon substrate. It is the schematic of the film-forming apparatus using the fine particle trap and film thickness monitor which concern on Example 2 of this invention. It is a figure which shows the reflectance spectrum (4.5 micrometers in film thickness) of AD film formed on the silicon substrate.

Explanation of symbols

40 Gas cylinder 41 Glass bottle 42 Powder raw material 43 Exhaust pipe 44 Exciter 45 Exciter 45 Transport pipe 46 Film forming chamber 47 Vacuum pump 48 Nozzle 49 Substrate 410 Film thickness monitor probe 411 Optical fiber 412 Light source 413 Spectrometer 414 PC
51 Reading Fiber 52 Irradiation Fiber 53 Gas Injection Portion 61 Reflectance Spectrum Measurement Value 62 Reflectance Spectrum Calculation Value 70 Gas Cylinder 71 Glass Bottle 72 Powder Raw Material 73 Exhaust Pipe 74 Exciter 75 Transport Pipe 76 Film Forming Chamber 77 Vacuum Pump 78 Nozzle 79 Substrate 710 Film thickness monitor probe 711 Optical fiber 712 Light source 713 Spectrometer 714 PC
715 Shutter 716 Particulate trap

Claims (17)

An optical film thickness monitor of a film forming apparatus for forming a compact by applying a mechanical impact force to an ultra fine particle brittle material supplied on a substrate to join the ultra fine particle brittle material,
White light is incident on the molded body from the end face of the measurement probe,
Measure the reflectance spectrum from the molded body,
An optical system characterized in that the film thickness and refractive index of the molded body are derived from the interference state of the reflectance spectrum under the condition that the wavelength range of the reflectance spectrum is longer than the particle size of the ultrafine particle brittle material. Film thickness monitor.   2. The optical film thickness monitor according to claim 1, further comprising means for ejecting a gas from a peripheral portion of the measurement probe so that the ultrafine particle brittle material does not adhere to an end face of the measurement probe.   The optical film thickness monitor according to claim 1, further comprising means for blowing a gas to a tip of the measurement probe so that the ultrafine particle brittle material does not adhere to an end surface of the measurement probe.   The optical film thickness monitor according to claim 1, further comprising means for heating the measurement probe so that the ultrafine particle brittle material does not adhere to an end face of the measurement probe. The film forming apparatus has a film forming chamber,
A fine particle trap is installed in the film formation chamber so that the fine particles do not float in the film formation chamber,
The film forming apparatus according to claim 1, wherein the film thickness monitor is installed in the film forming chamber so that an optical path is not obstructed by fine particles. The film forming apparatus has an aerosol generator,
5. A film forming apparatus, wherein the aerosol concentration of the aerosol generator is controlled by a signal generated by the film thickness monitor according to claim 1. The film forming apparatus has an aerosol generator,
The film forming apparatus according to claim 5, wherein the aerosol concentration of the aerosol generator is controlled by a signal generated by the film thickness monitor. The film forming apparatus has a film forming chamber,
The film formation chamber has an aerosol ejection nozzle and a shutter provided between the substrate and the aerosol ejection nozzle,
5. A film forming apparatus, wherein the film thickness of the molded body is controlled by operating the shutter with a signal generated by the film thickness monitor according to claim 1. The film forming apparatus has a film forming chamber,
The film formation chamber has an aerosol ejection nozzle and a shutter provided between the substrate and the aerosol ejection nozzle,
6. The film forming apparatus according to claim 5, wherein the film thickness of the molded body is controlled by operating the shutter with a signal generated by the film thickness monitor. Aerosol generating means for generating an aerosol in which fine particles of raw material powder are dispersed in a gas;
A film forming chamber having a nozzle for forming a thin film on the substrate by spraying fine particles supplied from the aerosol generating unit on the substrate, and a film thickness monitoring unit installed in the vicinity of the nozzle;
A light source connected to the film thickness monitoring means;
A spectrometer connected to the film thickness monitoring means;
Control means connected to the spectrometer,
White light from the light source is guided to the film thickness monitoring means and irradiated to a thin film formed on the substrate, and reflected light from the thin film is incident on the film thickness monitoring means and guided to the spectroscope. The spectrum is measured, and the film thickness of the thin film is derived by analyzing the reflectance spectrum with the control means under the condition that the wavelength range of the reflectance spectrum is longer than the particle size of the fine particles. A film forming apparatus.   The film forming apparatus according to claim 10, wherein the aerosol generating unit is provided with a vibrating unit, and the aerosol is generated by vibrating the vibrating unit.   The control means sends a signal for stopping the vibration means to the vibration means when the film thickness of the thin film reaches a set value, whereby the formation of the thin film is stopped. 2. The film forming apparatus according to 1.   The film forming apparatus according to claim 10, wherein the film forming chamber is evacuated to a predetermined degree of vacuum by a vacuum pump.   The film forming apparatus according to claim 10, wherein the monitoring unit and the light source are connected by an optical fiber.   The film thickness monitoring means includes an irradiation fiber for irradiating the white light, a reading fiber for reading the reflected light, and a gas ejection part for ejecting gas. Item 15. The film forming apparatus according to Item 14. In the film formation chamber, a fine particle trap is installed so that the fine particles do not float in the film formation chamber,
11. The film forming apparatus according to claim 10, wherein the film thickness monitoring means is installed in the film forming chamber so that the optical path is not obstructed by fine particles. In the film forming chamber, a shutter provided between the substrate and the nozzle is installed,
11. The film forming apparatus according to claim 10, wherein the film thickness of the thin film is controlled by operating the shutter with a signal generated by the film thickness monitoring means.

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