JPH0687900B2 - Fluorocarbon decomposition method and fluororesin film formation method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for decomposing CFC gas into a recoverable state and a method for decomposing CFC gas to form a fluororesin film on a substrate.

[Problems to be Solved by Prior Art and Invention]

Freon is photolyzed by the strong ultraviolet rays of sunlight, and the chlorine (Cl ₂ ) generated here reacts with ozone and begins to destroy the ozone layer surrounding the atmosphere. For example, Freon-12 (CCl ₂ F ₂ ), which has the highest destructive power among ozone, is explained as an example. Freon-12 is very stable in the atmosphere, but C-Cl is cut off when it receives the ultraviolet light of the sun. The generated Cl decomposes ozone and continues to generate O ₂ . This is the mechanism of O ₃ destruction. For this reason, light of 200 to 300 nm, which was previously absorbed by the ozone layer and did not reach the earth, that is, DNA of organisms
There is a problem of danger that light in the wavelength range that photodecomposes will fall on the ground.

For this reason, the use of CFCs has recently been banned, and attempts have been made to further decompose CFCs and recover them, but the epoch-making proposal has not yet been made.

The present invention has been made in view of the above problems of the prior art,
The first purpose is to decompose CFC gas and make it recoverable, and the second purpose is to decompose CFC gas.
It is to provide a method of precipitating as C ₂ F ₄ .

[Means for Solving the Problems]

The inventors have filled the reaction cell with CCl ₂ F ₂ gas in order to specify the wavelength of ultraviolet rays effective for the photodecomposition of freon, and
Irradiation with m ArF excimer laser light was performed, and changes in the UV and IR spectra were measured. The experimental results at this time are shown in FIG. 5, in which the horizontal axis represents the wavelength of light and the vertical axis represents the light transmittance. However, in the figure, the code A is for a gas that does not irradiate the laser at all (0 shots), and the code B is 1000
In case of shot, code C is in case of 5000 shot, code D
Shows the case of 10000 shots, the code E shows the case of 15000 shots, the code F shows the case of 20000 shots, the code G shows the case of 25000 shots, and the code H shows the case of 30000 shots.

As can be seen from FIG. 5, in the case of raw gas, the absorption is below 230 nm as shown by the A curve. Also CCl ₂ F ₂
Receiving light energy is decomposed and _{CCl 2 F 2 → CF 2 +} Cl 2, Cl 2 to 330nm is very stable C having absorption at 245nm
F ₂ radicals are generated. The absorption at 245 nm decreases with continued irradiation of laser light. However, the IR spectrum shows an increase in absorption near 1850 cm ^{-1, which} was not seen before. This is because CF ₂ polymerizes and C ₂ F ₄
Is considered to have been generated.

From the above experimental results, the following constitution was adopted to achieve the above object.

That is, in the method for decomposing CFCs according to claim (1), CFC ₂ or C is obtained by placing CFCs in a halogen-resistant reaction vessel and irradiating them with ultraviolet rays having a wavelength range of 170 to 220 nm.
It is intended to generate C ₂ F ₄ , which is a polymer of F ₂ .

In the method of forming a fluororesin film according to Claim (2), CF ₂ radicals by putting Freon inside the deposition substrate stowed halogen resistance reaction vessel, is irradiated with ultraviolet rays in the wavelength range 170~220nm Produces a wavelength range of 2
The fluorocarbon resin and the deposition substrate are irradiated with UV rays of 20 to 270 nm to deposit the fluororesin on the UV irradiation region of the substrate surface.

The wavelength range of ultraviolet rays required for the photodecomposition of CFC gas is 170 to 220 nm according to the experiments of the inventors shown in FIG. 5 and various known documents, and it is a CF ₂ radical and a polymer of CF ₂ radical. The wavelength range of ultraviolet rays for activating the production of (CF ₂ ) n is 220 to 270 nm as shown in FIG.

In addition, CFCs such as CClF ₂ and C
Although F ₂ is produced, since they are very reductive, it is necessary to prevent them from reacting with the reaction vessel in order to decompose them further. Therefore, the reaction vessel is constituted by a halogen-resistant reaction vessel, that is, a vessel made of halide, sapphire, or Teflon, a reaction vessel having an inner peripheral surface coated with Teflon, a stainless steel vessel, or the like.

[Action]

Freon gas receives the light energy of ultraviolet rays in the wavelength range of 170 to 220 nm and photolyzes as CCl ₂ F ₂ → CClF ₂ + Cl → CF ₂ + Cl ₂ . At this time, the presence of ClF, ClF ₃ , and C is also recognized, although it is slight. Note that C, which is an intermediate product in the production process of CF ₂ ,
ClF ₂ has a very strong reducing property, but the interface with CClF _{2 in} the reaction vessel is halogen resistant and does not react with CClF ₂ . Furthermore C
The F ₂ radical receives light energy to form a polymer C ₂ F ₄ . In particular polymerization product and CF ₂ in CF ₂ is activated by ultraviolet light energy 220～270Nm. Then, it can be recovered as a stable gas state of CF ₂ + Cl ₂ or a mixed state of powder and gas of C ₂ F ₄ + Cl ₂ .

In addition, the substrate interface in the reaction vessel is excited by the irradiation of ultraviolet rays, and CF ₂ radicals form C in the ultraviolet irradiation area of this substrate.
₂ F ₄ (fluorine resin) is deposited.

〔Example〕

 Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of an apparatus for carrying out the method of the present invention.

In this figure, reference numeral 10 is a chamber which is a reaction container in which a precipitation substrate 11 made of stainless steel is housed inside and a window 12 for incident ultraviolet light is formed above, and which is made of Teflon in a cylindrical container shape opening upward. It is composed of a chamber body 13, a transparent window member 14 made of MgF ₂ fixed to an opening of the chamber body 13 in a hermetically sealed state, and a ring-shaped window member fastening member 16. A CFC gas supply device (not shown) is connected to the side of the chamber body 13 to supply CFC gas to the chamber.
A gas inlet 18 for supplying the gas to the inside of the chamber 10 and a gas outlet 19 for discharging the gas in the chamber 10 to the outside are formed, which are connected to a processing gas storage tank (not shown). Above the window 12 of the chamber, ArF excimer laser 20A and KrF excimer laser 20B are arranged so that the laser light irradiation directions are orthogonal to each other, and each laser light is a half mirror.
Irradiation into the chamber 10 via 24. A mask plate 26 having a predetermined shape is arranged in the optical path of the laser light below the half mirror 24. A pattern of a predetermined shape (slits 27 with a predetermined pitch in the figure) is formed on the mask plate 26, and the laser light passes through the slit 27 and enters the chamber 10. In the chamber 10, a substrate 11 is arranged orthogonal to the incident laser light.
Only the region corresponding to the slit shape is irradiated with laser light on the surface of 11, and only the laser light irradiation region on the substrate surface is excited. Therefore, CF generated by photolysis
₂ precipitates as C ₂ F _{4 on} the substrate surface in the excited state.

Then, 20 Torr of Freon-12 (CCl ₂ F ₂ ) was enclosed in the chamber, and then ArF excimer laser light (wavelength 193 nm) of 60 mJ / cm ² and pulse width of 10 ns was incident, and CF ₂ radical was detected by 100 shot irradiation. Was done. Further irradiation of the same laser light increased the amount of CF ₂ radicals. Then K
By injecting rF excimer laser light (wavelength 249 nm) and irradiating 100 shots, CF ₂ is polymerized to form C ₂ F ₄ ,
This was deposited on the deposition substrate 11 to form a fluororesin (C ₂ F ₄ ) film having a slit pattern. And the Cl ₂ in the chamber 10 is sucked from the discharge port 19, the Cl ₂ is absorbed in water to recover CF ₂ by bubbling.

Note that CF ₂ radicals are not deposited on the substrate as CFC resin, and CF ₂ + Cl ₂ gas state or C ₂ F ₄ + Cl ₂ powder and gas mixed state is sucked from the discharge port 19 and Cl ₂ is hydrated. It is also possible to absorb CF ₂ and store only CF ₂ in a storage tank (not shown).

FIG. 2 shows a second embodiment of the device for carrying out the method according to the invention.

In the first embodiment, the half mirror 24 is used to make the laser beams of the ArF excimer laser 20A and the KrF excimer laser 20B incident on the same path, but in the present embodiment, the chamber main body 13 A second window 12A is provided on the side surface, and the laser light of the ArF excimer laser 20A is made to enter through this second window 12A. The laser beam incident from the second window 12A is irradiated onto the substrate in parallel with the deposition substrate 11.
Reference numeral 25 is a reflecting mirror, and other elements are the same as those in the first embodiment, and the duplicated description will be omitted.

In this example, ArF incident parallel to the deposition substrate 11
The excimer laser light (wavelength 193 nm) imparts the energy to decompose fluorocarbons, and the KrF excimer laser light (wavelength 2
(49 nm) activates the formation of CF ₂ and C ₂ F ₄ and excites the interface of the substrate 11, thereby increasing the deposition rate of C ₂ F _{4 on} the substrate 11.

FIGS. 3 and 4 show a third embodiment of the device for carrying out the method according to the invention.

In the first and second embodiments, CFC-12 is photolyzed by using a laser beam, but in this embodiment, a low pressure mercury lamp is used. That is, reference numeral 30 is a double-tube low-pressure mercury lamp in which an outer cylinder 34 is integrally formed around an inner cylinder 32 which is a discharge part. A gas inlet 38 and a gas outlet 39 are formed in the outer cylinder 34 to allow the inflow and exhaust of CFC gas. Again lamp 30
Teflon coating on the inner and outer surfaces of the outer cylinder
Is applied so that it does not react with CClF ₂ which is an intermediate product of photodecomposition of Freon-12. Also code 3
Reference numeral 5 is a counter electrode, which is a discharge part.
F ₂ radicals and C ₂ F _4, which is a polymer of CF ₂ radicals, are generated. In each of the first to third embodiments, the chamber 10 or the low-pressure mercury lamp 30 which is a reaction vessel is filled with CFC gas in the outer circumference of the discharge tube and is irradiated with ultraviolet rays for photolysis. Alternatively, the CFC gas may be continuously flowed at a predetermined rate into the reaction vessel to cause photolysis. Especially in the third embodiment,
If left untreated mercury lamp remains in the discharge state, automatically Freon is photolytic CF ₂ (or C ₂ F ₄₎ is obtained.

In the first and second embodiments, the laser light is used as the mask plate.
A slit-shaped fluororesin (C ₂ F ₄ ) film is formed on the substrate 11 by transmitting the slits 27 of 26, but the laser light transmission pattern formed on the mask plate 26 is free. A fluororesin film having an arbitrary pattern can be formed on the substrate.

Further, as an improvement of the present invention, a slight amount of CFCs present in the atmosphere below the ozone layer is irradiated with ultraviolet rays in the vicinity of 200 nm, and CFCs are converted into CF ₂ O and Cl ₂ gas by photolysis of the CFCs, and CFCs of the CFC are converted into ozone layers. It is also possible to prevent diffusion.

CF ₂ radicals are generally very stable and do not react with oxygen. Therefore, in the state of CClF _{2 which} has a strong reducing property before reaching CF ₂ , it is positively bound to oxygen. The reaction formula at this time is CCl ₂ F ₂ + 1 / 2O ₂ → CClF ₂ + 1 / 2O ₂ + Cl → CF ₂ O + Cl ₂ .

That is, a Teflon chamber 10 similar to that of the first embodiment.
CFC-12 gas 30Torr, oxygen 730Torr,
ArF excimer laser light (40 mJ / cm ² ) is incident there. When laser pulses are overlapped as shown in Fig. 6, CCl ₂ F ₂ is photolyzed and Cl ₂ absorption increases at 330 nm, but as shown in Fig. 5, absorption of CF ₂ near 250 mn is observed. In addition, it can be seen from the infrared spectroscopic analysis that CF ₂ O was formed.

〔The invention's effect〕

As is clear from the above description, according to the present invention, the fluorocarbon can be photodecomposed and recovered as stable CF ₂ radicals (or C ₂ F ₄ ). Further, C ₂ F ₄ which is a polymer of CF ₂ can be deposited on the deposition substrate in the reaction vessel to form a fluororesin film having a predetermined shape.

[Brief description of drawings]

FIG. 1 is a schematic view of a first embodiment of an apparatus for carrying out the method of the present invention, FIG. 2 is a schematic view of a second embodiment of an apparatus for carrying out the method of the present invention, and FIG. 3 is a longitudinal sectional view of a third embodiment of the apparatus for carrying out the method of the present invention, FIG.
FIG. 5 is a cross-sectional view taken along line IV-IV shown in the figure, FIG. 5 is a diagram showing a UV spectrum in the case where the Freon-12 gas is irradiated with laser light, and FIG. 6 is a laser beam in the presence of oxygen in the Freon-12 gas. It is a figure which shows a UV spectrum at the time of irradiating with. 10 ... Chamber as reaction container, 11 ... Stainless plate as deposition substrate, 20A ... ArF excimer laser, 20B ... KrF excimer laser, 18,38 ... Gas inlet, 19,39 ... Gas outlet , 26 ... Mask plate, 30 ... Low-pressure mercury lamp which is a reaction vessel, 32 ... Inner cylinder which is an ultraviolet irradiation part.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C08J 5/18 CEW 9267-4F

Claims (2)

[Claims] 1. CF is prepared by placing a CFC gas in a halogen-resistant reaction vessel and irradiating it with ultraviolet rays having a wavelength range of 170 to 220 nm.
_A method for decomposing CFCs, which comprises producing C ₂ F ₄ which is a polymer of ₂ or CF ₂ . 2. A halogen-resistant reaction vessel having a deposition substrate accommodated therein is charged with CFC gas and irradiated with ultraviolet rays having a wavelength range of 170 to 220 nm to generate CF ₂ radicals, and further having a wavelength range of 220 to 270 nm. A method for forming a fluororesin film, which comprises irradiating a fluorocarbon and a deposition substrate with ultraviolet rays to deposit the fluororesin in an ultraviolet irradiation region on the surface of the substrate.