JP3179778U - UV irradiation chamber with protective member for light transmission window - Google Patents

Abstract

A UV irradiation chamber for protecting a light transmission window from corrosion of a cleaning gas containing fluorine radicals.
A UV irradiation chamber 31 with a protective member for a light transmission window 17 that protects the light transmission window 17 from corrosion of a cleaning gas containing fluorine radicals. A light transmission window 17 that partitions the irradiation object side, a sapphire bulk crystal plate 35 that is a protection member for the light transmission window 17 and covers the light transmission window 17 with a predetermined gap 36 and is disposed on the irradiation object side; , Comprising.
[Selection] Figure 3

Description

  The present invention relates to a UV irradiation chamber with a protective member for a light transmission window that protects the light transmission window from corrosion of a cleaning gas containing fluorine radicals.

  As a result of the miniaturization of wiring design and the multilayer wiring structure that accompany high device integration in recent years, reduction of interlayer capacitance is indispensable for high speed and low power consumption of the device. A low-k (low dielectric constant film) material is used to reduce the interlayer capacitance, but the mechanical strength (EM: Elastic modulus) decreases with the reduction of the dielectric constant, which is received in the post-process of CMP, wiring bonding and packaging. Problems arise with stress tolerance.

  As a method for improving the above problem, a method of improving the mechanical strength by curing a low-k material by UV irradiation can be considered (for example, Patent Document 1 and Patent Document 2). According to this UV irradiation method, the low-k material shrinks and hardens, and the mechanical strength EM can be improved by 50 to 200%.

  In addition, the dielectric constant of the film can be reduced and cured by decomposing and / or removing the porogen introduced into the film by UV irradiation (or heating, plasma, electron beam). (For example, patent documents 3-5).

Furthermore, as another requirement with the recent high integration of devices, photo-CVD using photochemical reaction is a method for obtaining various thin films formed by thermal CVD or PECVD by a method that is not damaged by heat or plasma. As studied, the UV processing apparatus has been generally used for the preparation of substances using various kinds of objects to be processed by ultraviolet rays and photochemical reactions.
US Pat. No. 6,759,098 US Pat. No. 6,296,909 US Pat. No. 6,583,048 US Pat. No. 6,846,515 US Pat. No. 7,098,149

  As described above, when light energy is to be applied to the object to be processed or the reaction space, 1) the pressure of the reaction space and control of the atmospheric gas are required, and 2) the generated gas adheres to the UV lamp. It is necessary to partition the UV lamp from the reaction space for reasons such as fouling and 3) the need for safe exhaust of the generated gas. As the partition plate, a light transmission window made of synthetic quartz that transmits light energy uniformly is usually used.

  However, UV, which is high energy, tends to cause a decrease in transmittance due to the material of the light transmission window and the deposits attached to the light transmission window, and in a curing process in which a large amount of outgas (decomposed gas that generates an irradiated film) is generated. There is a problem that the maintenance cycle (the number and time of cleaning or replacement of the transmission window) must be very short.

Conventionally, a cleaning method in which ozone is generated by introducing O ₂ into a reaction space and irradiating UV, and deposits are removed by the generated ozone, is a curing process in which a large amount of outgas is generated. Since a long time is required for cleaning, a more efficient method is desired.

  For example, there is a method of generating radical species with a radical generator installed outside the UV irradiation chamber and introducing the radical species into the UV irradiation chamber from the outside of the UV irradiation chamber, but the device is expensive and large. A cheaper and space-saving method is desired.

As another cleaning method, there is a method in which active species are generated by an auxiliary RF electrode provided in the UV irradiation chamber for cleaning, and a method in which this cleaning method is combined with conventional O ₂ + UV ozone cleaning. .

As a further cleaning method with improved efficiency, a cleaning gas containing fluorine as an additive gas instead or O ₂ in O _2, the radical generator was placed in UV irradiation chamber outside or auxiliary RF provided in the chamber There is a method of cleaning by generating active species with an electrode. In this case, it is necessary to select a material that does not corrode the transmission window by fluorine and has a high light transmittance. As such a material, crystals such as CaF ₂ , MgF ₂ , BaF ₂ , Al ₂ O ₃ , or the synthetic quartz coated with _{CaF 2, MgF 2, BaF 2} , Al 2 O 3 can be used.

However, the light transmission window is made of a crystal such as CaF ₂ , MgF ₂ , BaF ₂ , Al ₂ O _3, etc., and all the light transmission windows are formed with a thickness having a mechanical strength sufficient to partition an atmospheric pressure-vacuum. Then, it becomes very expensive and the transmittance is also lowered. In addition, when coating with CaF ₂ , MgF ₂ , BaF ₂ , Al ₂ O _3, etc., it is very difficult to produce the entire surface of the light transmission window with no defects, and there is an adverse effect due to the occurrence of pinholes and the like. It is almost impossible to prevent. In the case of bonding, there are many problems such as differences in thermal expansion coefficient, heat resistance, UV transmittance / UV resistance of the adhesive, and practical application is difficult.

  An object of the present invention is to provide a UV irradiation chamber that protects a light transmission window from corrosion of a cleaning gas containing fluorine radicals.

  In order to solve the above problems, the present invention provides a UV irradiation chamber with a light transmission window protection member that protects the light transmission window from corrosion of a cleaning gas containing fluorine radicals. A light transmission window that partitions the UV light source side and the UV irradiated object side; and a protective member for the light transmitting window that covers the light transmitting window with a predetermined gap and is disposed on the irradiated object side. A UV irradiation chamber with a protective member for a light transmission window, comprising a bulk crystal plate of sapphire.

  In this way, since the bulk crystal plate of sapphire that covers the light transmission window with a predetermined gap is arranged on the irradiated object side, adhesion of outgas to the light transmission window and corrosion due to fluorine radicals can be suppressed. The light transmission window can be protected.

  The sapphire bulk crystal plate has excellent light transmission in a wide wavelength range, and is excellent in durability and chemical resistance in high temperature processes, so even if it is placed in a UV irradiation chamber, fluorine radicals and outgas Etc. can be suppressed as much as possible, and the light transmission window can be protected.

  Further, the end of the bulk crystal plate is disposed at the inlet of the source gas into the UV irradiation chamber, and the source gas is passed through the gap and the irradiated object side so that the light transmission window Since the gap between the metal plate and the bulk crystal plate and the irradiated object side are at substantially the same pressure, it prevents outgas from adhering to the gap to prevent its adhesion, and further prevents fluorine radicals from entering and corrodes the light transmission window. Can be prevented.

  In addition, since the gap between the light transmission window and the bulk crystal plate is configured to communicate with the irradiated object side by a pipe with a shut-off valve, the pressure in the gap and the irradiated object side is almost the same, It is possible to prevent the outgas from entering into the gap and prevent its adhesion. Further, by closing the shut-off valve when fluorine radicals are generated, entry of fluorine radicals into the gap can be prevented and corrosion of the light transmission window can be prevented.

  The UV irradiation chamber may include an auxiliary RF electrode that generates the fluorine radicals in the UV irradiation chamber. Alternatively, the UV irradiation chamber may be provided with a fluorine radical generator that generates the fluorine radicals outside the UV irradiation chamber, and the generated fluorine radicals may be introduced into the UV irradiation chamber.

  As the cleaning gas, a gas containing fluorine in a molecule can be used, or a gas containing a gas containing fluorine in a molecule and oxygen gas can be used.

  According to the present invention, the light transmission window is covered with a predetermined gap, and the sapphire bulk crystal plate, which is the protective member of the light transmission window, is disposed on the irradiated object side. It is possible to provide a UV irradiation chamber that protects the light transmission window from corrosion of the cleaning gas that is contained.

FIG. 1A is a schematic cross-sectional view of a conventional UV irradiation chamber, and FIG. 1B is an enlarged schematic view of a part of FIG. FIG. 2 is a schematic cross-sectional view in which a remote plasma unit of a fluorine radical generator is added to the UV irradiation chamber of FIG. FIG. 3 is a schematic partial sectional view of a UV irradiation chamber according to the first embodiment of the present invention. FIG. 4 is a partial cross-sectional schematic view of a UV irradiation chamber according to the second embodiment of the present invention. FIG. 5 is a diagram showing the relationship between the UV transmittance (%) and the wavelength (nm) at each stage before and after UV irradiation of the light transmission window and after cleaning. FIG. 6 is a diagram showing the relationship between the UV transmittance (%) and the wavelength (nm) of the sapphire bulk crystal plate before and after cleaning in the first example. FIG. 7 is a diagram showing the relationship between the UV transmittance (%) and the wavelength (nm) of the sapphire bulk crystal plate before and after cleaning in the second embodiment.

  1A and 1B are schematic views of a conventional UV irradiation chamber for strengthening a substrate which is an object to be irradiated by UV irradiation.

  As shown in FIG. 1A, the UV irradiation chamber 11 is mainly composed of a chamber main body 12 capable of controlling the surroundings of atmospheric pressure from a vacuum, and a UV irradiation unit 13 installed on the upper portion of the chamber main body 12. .

  The UV irradiation unit 13 includes a plurality of tube-shaped UV lamps 15 which are UV light emitters that emit light continuously and in a pulse shape, and are arranged in parallel. Further, UV light from the UV lamps 15 is placed in the chamber body 12. An umbrella-shaped reflector 16 is provided above the UV lamp 15 in order to efficiently irradiate a substrate (not shown) to be placed. The reflection plate 16 is adjusted in its arrangement position and installation angle in order to make the illuminance uniform.

  In the upper part of the chamber body 12, synthetic quartz that uniformly transmits UV from the UV lamp 15 into the chamber body 12, partitions the chamber body 12 and the UV irradiation unit 13, and blocks the chamber body 12 from the atmosphere. A light transmission window 17 made of metal is provided.

  As shown in FIG. 1B, a susceptor 18 with a built-in heater is installed in the chamber body 12 in parallel with the UV lamp 15 so that UV is uniformly irradiated. A source gas introduction port 21 for introducing a source gas into the inside is formed in an annular shape in a ring-shaped member.

  The chamber body 12 is provided with an exhaust port (not shown) for exhausting reaction gas or the like, and the pressure inside the chamber body 12 is a pressure control valve (not shown) provided at the exhaust port. It is adjusted by.

  The inside of the UV irradiation unit 13 is a sealed space, but a purge gas intake port (not shown) and a discharge port (not shown) are provided.

The UV irradiation process by the UV irradiation chamber 11 will be described. The interior of the chamber body 12 is selected from Ar, CO, CO ₂ , C ₂ H ₄ , CH ₄ , H ₂ , He, Kr, Ne, N ₂ , O ₂ , Xe, alcohol-based gas, and organic-based gas. The gas pressure is about 0.1 Torr to about atmospheric pressure (1 Torr, 10 Torr, 50 Torr, 100 Torr, 1000 Torr, and a value between the above values, preferably 1 to 50 Torr), and an atmosphere of about 0 ° C. to about 650 A susceptor 18 set at a temperature of 10 ° C. (10 ° C., 50 ° C., 100 ° C., 200 ° C., 300 ° C., 400 ° C., 500 ° C., 600 ° C.) A semiconductor substrate, which is an object to be processed, carried from a load lock chamber (not shown) through a gate valve (not shown) is placed on the UV lamp 15. UV having a proper distance (Gap) (5 to 90 mm) and a wavelength of about 100 nm to about 400 nm (including 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, and numerical values between the above values, preferably about 200 nm) Light output from about 1 mW / cm ² to about 1000 mW / cm ² (10 mW / cm ² , 50 mW / cm ² , 100 mW / cm ² , 200 mW / cm ² , 500 mW / cm ² , 800 mW / cm ² , and between the above values Thin film on a semiconductor substrate at a rate of about 1 Hz to about 1000 Hz (including 10 Hz, 100 Hz, 200 Hz, 500 Hz, and values between the above values) continuously or in a pulsed manner, preferably 5 to 200 mW / cm ^2. Is irradiated with UV light.

  The UV irradiation time is about 1 second to about 20 minutes (including 5 seconds, 10 seconds, 20 seconds, 50 seconds, 100 seconds, 200 seconds, 500 seconds, 1000 seconds, and numerical values between the above values). After the UV irradiation process, the generated gas or the like inside the chamber body 12 is exhausted from an exhaust port (not shown).

  In the UV irradiation chamber 11, this series of UV irradiation processing is performed in an automatic sequence, and gas introduction, UV irradiation, UV irradiation stop, and gas stop steps can be performed as processing steps.

  In the UV irradiation process, outgas is generated from the thin film on the semiconductor substrate by UV irradiation and adheres to the light transmission window 17 made of synthetic quartz and the inner wall of the chamber body 12. Since outgas deposits deposited on the light transmission window absorb UV, the curing efficiency by UV irradiation is reduced. In addition, the deposits deposited on the inner wall of the chamber peel off and cause generation of particles.

In order to remove these deposits, the inside of the light transmission window 17 and the chamber body 12 is cleaned. For cleaning, for example, there is a method in which O ₂ is ozonized by UV irradiation and reacted with the deposit to remove it. However, since the proportion of O ₂ that is ozonized by UV is considerably low, for example, there is a method of increasing the efficiency of ozone generation by activating with a remote plasma unit before introducing O ₂ into the chamber and ozonizing with UV. It has been taken.

  A schematic cross-sectional view of the remote plasma unit 27 connected to the UV chamber 1 is shown in FIG. In FIG. 2, the same parts as those in FIG. 1 are denoted by the same names and the same reference numerals.

  As shown in FIG. 2, the remote plasma unit 27 is provided outside the UV irradiation chamber 11, and the cleaning gas is first introduced into the remote plasma unit 27, excited, and then introduced into the UV irradiation chamber 11. The remote plasma unit 27 and the cleaning gas inlet 28 provided on the side wall of the chamber body 12 are connected by piping.

On the other hand, when further cleaning speed is required, or when deposits that are not decomposed by ozone are generated, or when a large amount of deposits are generated and sufficient cleaning cannot be expected with ozone alone, the cleaning gas is used. NF ₃ or the like can be used. Specifically, NF ₃ is introduced into the chamber, and fluorine radicals are used to decompose and remove the light transmission window and the dirt on the inner wall of the chamber body. In some cases, a small amount of NF ₃ is added to O ₂ for use. There is also.

  Although this fluorine radical has an effect of decomposing and removing dirt in the reactor better than ozone, on the other hand, the surface of the light transmission window made of synthetic quartz is eroded by corrosion, resulting in a problem of lowering the UV transmittance. (See FIG. 5).

FIG. 5 shows the ultraviolet visible transmittance in a predetermined wavelength range of the light transmission window. FIG. 5 is a result of measuring how much light of which wavelength is transmitted by the light transmission window made of synthetic quartz by a spectrophotometer, and graph (1) in FIG. 5 shows an initial state before UV irradiation. 2) shows the transmittance after UV irradiation, (3) shows the transmittance after cleaning with O ₂ , and (4) shows the transmittance after cleaning with NF ₃ .

When NF ₃ is used as the cleaning gas, the decomposition and removal of the deposits by the fluorine radicals generated as described above is much more effective than the case of using O ₂ , but the surface of the light transmission window is corroded and UV transmission is achieved. It can be seen that the rate is greatly reduced (see (4) in FIG. 5).

  In order to solve the above problems, the present invention provides efficient cleaning and removal of deposits with a cleaning gas containing fluorine radicals, protecting the light transmission window from corrosion caused by fluorine radicals, and UV transmittance. The UV irradiation chamber is provided with a sapphire bulk crystal plate which is a protective member for the light transmission window and is disposed on the chamber body side so as to cover the light transmission window with a predetermined gap.

  The cleaning method of the UV irradiation chamber of the present invention comprises a remote plasma unit of a radical generator installed outside the UV irradiation chamber after completing irradiation of the substrate with UV light transmitted through a light transmission window provided in the UV irradiation chamber, Alternatively, it is a process of cleaning the light transmission window and the inner wall of the chamber by generating fluorine radicals which are active species with an auxiliary RF electrode provided in the chamber body.

  In the UV irradiation process, a substrate (for example, a semiconductor substrate) placed on a susceptor provided in the UV irradiation chamber is passed through a light transmission window provided between the UV lamp and the susceptor in the UV chamber. In this process, the substrate is irradiated with UV light.

  Prior to the UV irradiation process, a film composed of Si, C, H, O, and optional N, or a dielectric film containing porogen is formed on the substrate by, for example, PECVD, PEALD, PVD, or the like.

  The UV irradiation process is a film curing process or a porogen decomposition and / or removal process.

  This film is a low dielectric film, a SiOC film, or a dielectric film containing porogen. When the film formed on the substrate is cured in the chamber body, or the porogen introduced in the film is decomposed and / or removed, the dielectric constant of the film is reduced, And when cured, a substantial amount of outgas is generated from the film as a result of the decomposition of the chemical structure within the chamber body.

  Outgas consists of hydrocarbon species. Outgas accumulates on the surface of the inner wall of the chamber body including the light transmission window. Accumulated outgas accumulation prevents UV light from passing through the light transmission window, thereby reducing the efficiency of the process. In particular, the light transmission window needs to be frequently cleaned.

  In a UV irradiation chamber, the cleaning process is controlled by controlling the pressure and flow within the chamber body. The pressure is 10 Torr or less (for example, 0.2 to 8 Torr), the flow rate of a gas containing fluorine in the molecule is 0 to 10 slm (for example, 0 to 8 slm), and the flow rate of oxygen gas is 0 to 10 slm (for example, 0 ~ 8 slm), inert gas such as Ar, He, Kr or Xe has a flow rate of 0.1 to 10 slm (eg 0.2 to 8 slm) and a cleaning time of 5 to 1000 seconds (eg 10 to 600). Second, 50-200 seconds).

  In the cleaning process, UV irradiation is preferably combined as appropriate. In this case, the UV light has an intensity of 1 mW / cm 2 to 500 mW / cm 2 (for example, 100 mW / cm 2 to 400 mW / cm 2) and a wavelength of 100 to 1000 nm (for example, 200 to 400 nm). When the fluorine-containing gas is used as a cleaning gas, UV irradiation is performed as necessary to further excite the fluorine gas.

  Note that oxygen gas and fluorine-containing gas may be used in combination as the cleaning gas.

  In addition, when fluorine radicals are generated from a remote plasma unit that is a radical generation mechanism provided outside the UV irradiation chamber and introduced into the chamber body, the fluorine radicals enter the gap between the light transmission window and the sapphire bulk crystal plate. In order to prevent this, it is necessary to flow nitrogen gas or the like from the raw material gas inlet and maintain the inside of the chamber body and the gap at substantially the same pressure. In this case, the flow rate of nitrogen gas is preferably about 0.1 to 10 slm (for example, 0.2 to 8 slm).

  Embodiments of the UV irradiation chamber of the present invention will be described below with reference to the drawings.

  FIG. 3 shows a schematic partial sectional view of the UV irradiation chamber of Example 1 according to the present invention. In FIG. 3, parts having the same structure and function as those in FIGS. 1 and 2 are given the same name and the same reference numerals.

  As shown in FIG. 3, the UV irradiation chamber 31 of this embodiment includes a UV irradiation unit 32 provided with a UV lamp 15 and a reflection plate 16 serving as a light source of UV light, and a substrate (not shown) irradiated with UV. And a chamber body 33 provided with a susceptor (not shown).

  In the upper part of the chamber body 33, the UV light from the UV lamp 15 is uniformly transmitted into the chamber body 33, the chamber body 33 and the UV irradiation unit 32 are partitioned, and the chamber body 33 is shielded from the atmosphere. A light transmission window 17 made of quartz is provided.

  A large-diameter sapphire bulk crystal plate 35 is disposed below the light transmission window 17 and on the chamber body 33 side so as to cover the light transmission window 17 with a predetermined gap 36. The thin sapphire bulk crystal plate 35 that is held in the chamber body 33 and has a large diameter has a thickness of 3 mm.

  The peripheral edge of the sapphire bulk crystal plate 35 is disposed in a ring-shaped source gas inlet 38 through which source gas is introduced, and the source gas introduced from the source gas inlet 38 is separated from the chamber body 33 and the gap. Therefore, the inside of the chamber main body 33 and the inside of the gap 36 have substantially the same pressure.

In the present embodiment, using the NF ₃ as a cleaning gas excites the fluorine radicals by the remote plasma unit 27 provided outside the UV irradiation chamber 31 a cleaning gas of NF ₃ (see FIG. 2), the chamber body 33.

  Instead of the remote plasma unit 27, an auxiliary RF electrode may be provided inside the chamber body 33, and fluorine gas may be excited by applying RF power to generate fluorine radicals.

In the UV irradiation chamber 31 of this embodiment, the cleaning process is controlled by controlling the pressure and flow in the chamber body 33. In this embodiment, the pressure is 1-10 Torr, the flow rate of the cleaning gas of NF ₃ is 0.5-2 slm, the flow rate of Ar gas is 2-5 slm, and the cleaning time is 5 minutes. During the cleaning, in order to prevent the entry of fluorine radicals into the gap 36, 4 slm of N ₂ is passed through the ring-shaped source gas inlet 38.

  FIG. 6 shows a graph of ultraviolet visible transmittance in a predetermined wavelength range before and after cleaning of the sapphire bulk crystal plate 35 in the present embodiment. Since the graph (1) indicating the transmittance before cleaning and the graph (2) indicating the transmittance after cleaning almost overlap each other, in this embodiment, the sapphire bulk crystal plate is also cleaned before and after the cleaning in the same manner as the light transmission window. It can be seen that there was no change in the transmittance.

As described above, in this embodiment, the end portion of the sapphire bulk crystal plate 35 is disposed in the source gas introduction port 38, and the source gas flows through the gap 36 and the chamber body 33. The penetration of fluorine radicals can be suppressed, adhesion of outgas to the light transmission window and corrosion due to fluorine radicals can be suppressed, and the light transmission window can be protected.

  FIG. 4 shows a schematic partial sectional view of the UV irradiation chamber of Example 2 according to the present invention. In FIG. 4, parts having the same structure and function as those in FIGS. In addition, the present embodiment will be described with a focus on differences from the first embodiment, and the points in common with the first embodiment will be omitted as appropriate.

  As shown in FIG. 4, in Example 2, source gas or the like does not flow directly from the source gas introduction port 38 into the gap 36 between the light transmission window 17 and the sapphire bulk crystal plate 35, The difference from the first embodiment is that communication is performed by a pipe 42 provided with a shut-off valve 41 in the middle.

Therefore, NF ₃ is used as the cleaning gas, a remote plasma unit that generates fluorine radicals by exciting fluorine is provided outside the UV processing chamber 31, and in this embodiment, the pressure is 1-10 Torr. The gas flow rate is 0.5 to 2 slm, the flow rate of Ar gas is 2 to 5 slm, and the cleaning time is 5 minutes.

  The feature of this embodiment is that, during the curing process by UV irradiation, the gap 36 and the inside of the chamber body 33 communicate with each other through a pipe, so that the pressure is substantially the same, so that the generated outgas is prevented from entering the gap 36. Further, during the cleaning process, the entry of fluorine radicals into the gap 36 can be prevented by closing the shut-off valve 41, so that the adhesion of outgas to the light transmission window 17 and the corrosion of light transmission by the fluorine radicals can be prevented. Is possible.

In Example 1, N ₂ is introduced into the gap 36 from the source gas inlet 38 in order to prevent entry of fluorine radicals into the gap 36 during cleaning. During cleaning, the shut-off valve 41 can be closed to suppress the entry of fluorine radicals into the gap 36, and N ₂ need not be introduced from the source gas inlet 38 during cleaning.

  FIG. 7 shows a graph of ultraviolet visible transmittance in a predetermined wavelength range before and after cleaning of the sapphire bulk crystal plate 35 in this example. Since the graph (1) indicating the transmittance before cleaning and the graph (2) indicating the transmittance after cleaning almost overlap each other, in this embodiment, the sapphire bulk crystal plate is also cleaned before and after the cleaning in the same manner as the light transmission window. It can be seen that there was no change in the transmittance.

DESCRIPTION OF SYMBOLS 11 UV irradiation chamber 12 Chamber main body 13 UV irradiation unit 15 UV lamp 16 Reflector plate 17 Light transmission plate 18 Susceptor 21 Raw material gas inlet 28 Cleaning gas inlet 29 Remote plasma unit 31 UV irradiation chamber 32 UV irradiation unit 33 Chamber main body 35 Sapphire Bulk crystal plate 36 Gap 38 Source gas inlet 41 Shut-off valve

Claims (7)

A UV irradiation chamber with a protective member for a light transmission window that protects the light transmission window from corrosion of a cleaning gas containing fluorine radicals,
A light transmission window that divides the inside of the UV irradiation chamber between the UV light source side and the UV irradiated object side;
A sapphire bulk crystal plate, which is a protective member for the light transmission window, covers the light transmission window with a predetermined gap, and is disposed on the irradiated object side. UV irradiation chamber.   2. An end of the bulk crystal plate is disposed at a source gas introduction port into the UV irradiation chamber, and the source gas flows through the gap and the irradiated object side. A UV irradiation chamber with a protective member for a light transmission window described in 1.   The UV irradiation chamber with a protective member for a light transmission window according to claim 1, wherein the gap is communicated with the irradiated object side by a pipe with a shutoff valve.   The UV irradiation chamber with a protective member for a light transmission window according to claim 1, wherein the UV irradiation chamber includes an auxiliary RF electrode for generating the fluorine radical in the UV irradiation chamber.   The UV irradiation chamber with a protective member for a light transmission window according to claim 1, wherein the UV irradiation chamber includes a fluorine radical generator for generating the fluorine radical outside the UV irradiation chamber.   The UV irradiation chamber with a protective member for a light transmission window according to claim 1, wherein the cleaning gas is a gas containing fluorine in a molecule. 2. The UV irradiation chamber with a protective member for a light transmission window according to claim 1, wherein the cleaning gas is a gas containing a gas containing fluorine in its molecule and oxygen gas.

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