TW201347826A - Air filter for CVD apparatus and CVD apparatus having the same - Google Patents

Abstract

The present invention provides an air filter for CVD apparatus, having suitable properties such as excellent heat resistance and plasma resistance to be used in an air filter for CVD apparatus, while exhibiting a filter performance of good balance in which a pressure loss is low and a capture rate of particles is high. The air filter for CVD apparatus provided in the present invention comprises: a filter layer (a) consisting of PTFE fibers (a); wherein the average fiber diameter of the PTFE fibers (a) is 10nm to 50 μ m.

Description

Air filter for CVD apparatus and CVD apparatus having the same

The present invention relates to an air filter (air filter for CVD apparatus) used in a CVD apparatus and a CVD apparatus having the same.

The air filter is used to trap fine particles contained in air, raw material gas or exhaust gas, and requires high particle trapping rate (must be able to trap particles with high efficiency) and low pressure loss. The materials constituting the air filter are also involved in various aspects depending on the application.

As a material constituting the air filter, a fluororesin such as polytetrafluoroethylene (PTFE) is known. Since the fluororesin has excellent properties (chemical resistance, plasma resistance, heat resistance, etc.), the fluororesin air filter is used in a wide range of applications.

Patent Document 1 discloses a turbo air intake port filter including a composite filter medium and a frame, the composite filter medium comprising: a membrane filter layer containing porous polytetrafluoroethylene (extended PTFE); Deep layer of filter media.

Patent Document 2 discloses a filter medium having a PTFE porous membrane (extending PTFE), wherein the PTFE porous membrane (extended PTFE) is specific The uncalcined PTFE was extended under the conditions.

Although compared to filters made of other polymeric materials, Although the PTFE filter is excellent in plasma resistance, etc., there is still room for improvement in heat resistance and the like because heat shrinkage or the like is still generated.

On the other hand, in Patent Document 3, a use is disclosed in filtering A fluorine fiber sheet for use in a device in which a PTFE powder is dispersed in a matrix (for example, a viscose) to prepare an aqueous dispersion, and the aqueous dispersion is discharged into a coagulation bath and spun to obtain an unstretched PTFE. The fiber sheet is produced by heating and sintering the unstretched PTFE-based fiber sheet and extending at least in the longitudinal direction or the transverse direction.

Further, in Patent Document 4, a use in a filter is disclosed. A fluorofiber formed body obtained by dehydrating and drying a papermaking raw material of a fluorine-based fiber by a wet paper making method using a wire mesh papermaking mold, and then placing the shaped body in a mold The mold can be adhered to the inner wall of the shaped original body after the heat treatment, and the fibers are fused to each other by heating to a melting point of the fluorine-based fiber to form a preform, and then the preform is further prepared. The molded body is obtained by inserting a male and female mold corresponding to the shape of the preform and performing hot press forming.

The filter composed of such a fluorine fiber cannot be satisfactorily balanced. The balance between pressure loss and particle trapping still has room for improvement in terms of filter performance.

A chemical vapor deposition (CVD) method is a method of supplying a material gas containing a target film component on a substrate material to a CVD apparatus, and depositing a thin film by chemical reaction on the surface of the substrate and the gas phase. . For example, it is generally used in the surface treatment of a cutting tool and the manufacturing steps of a semiconductor element. Moreover, the type of CVD involves thermal CVD and plasma in accordance with the film formation mechanism. CVD and many other aspects.

The exhaust gas discharged from the CVD apparatus contains various types of pollutants represented by SiO ₂ , SiH ₄ , and SiCl ₄ , and is required to be removed by using a filter or the like before being discharged to the atmosphere. Therefore, the filter provided at the exhaust port of the CVD apparatus is required to have a high particle collection rate. Further, since the inside of the CVD apparatus is a high temperature environment (for example, thermal CVD) or a raw material gas is excited to a severe condition such as a plasma state (for example, plasma CVD), the filter used in the CVD apparatus is also Heat resistance and plasma resistance (free radical resistance) are required.

Prior technical literature Patent literature

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2011-202662

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2011-105895

[Patent Document 3] Japanese Patent Laid-Open Publication No. 03-130496

[Patent Document 4] Japanese Laid-Open Patent Publication No. 05-287700

An object of the present invention is to provide an air filter for a CVD apparatus, which is a filter having a low pressure loss and a high collection rate of particles, and a CVD apparatus having the filter. At the same time, it is excellent in heat resistance and plasma resistance, and is suitable for use in an air filter for a CVD apparatus.

The result of intensive research by the inventors found that the use contains When the filter medium layer of the PTFE fiber having a predetermined average fiber diameter is used as a material of the air filter, it is possible to exhibit a filter performance with a low pressure loss and a high collection rate of particles, and is excellent in heat resistance and plasma resistance. Further, the inventors of the present invention have completed the present invention based on the characteristics that can be used as such an air filter for a CVD apparatus.

That is, the gist of the present invention is as follows.

[1] An air filter for a CVD apparatus, comprising: a filter medium layer (a) comprising PTFE fibers (a); and an average fiber diameter of the PTFE fibers (a) of 10 nm to 50 μm.

[2] The air filter for a CVD apparatus according to [1], wherein the filter layer (a) has a thickness of from 5 μm to 200 μm.

[3] The air filter for a CVD apparatus according to [1] or [2], wherein the filter medium layer (a) has a void ratio of 0.60 to 0.95.

[4] The air filter for a CVD apparatus according to any one of [1] to [3] wherein the PTFE fiber (a) is obtained by an electric field spinning method.

[5] The air filter for a CVD apparatus according to any one of [1] to [4], wherein the support layer (b) is laminated on one or both sides of the filter layer (a).

[6] A CVD apparatus according to any one of [1] to [5], wherein the air filter for the CVD apparatus is provided in the raw material gas supply port and/or the gas exhaust port.

The air filter for a CVD apparatus of the present invention exhibits high heat resistance and high radical resistance (plasma resistance), and exhibits excellent air balance with low pressure loss and high particle collection rate. Filter performance.

Fig. 1 is a view showing an electron micrograph of the actual machine obtained in Example 3.

Fig. 2 is a view showing an electron micrograph of the surface (surface) obtained after the actual machine obtained in Example 3.

Fig. 3 is a view showing an electron micrograph of the actual machine obtained in Example 3 (back surface).

Hereinafter, the present invention will be described in more detail.

An air filter for a CVD apparatus according to the present invention (hereinafter, simply referred to as an "air filter") is an essential component and has a polytetrafluoroethylene fiber (a) (PTFE fiber (a)). a filter material layer (a), wherein the polytetrafluoroethylene fiber (a) has an average fiber diameter of 10 nm to 50 μm, and may be laminated on one or both sides of the filter layer (a) as necessary, as will be described later. (b).

The air filter of the present invention is provided in a CVD (Chemical Vapor Deposition) device (specifically, a raw material gas supply port and/or an exhaust gas discharge port of the device, and is capable of supplying a raw material gas and/or an exhaust gas In the filtered state, it is used to filter the exhaust gas discharged from the raw material gas and/or the device supplied into the device, and the particles (dust) contained in the raw material gas and/or the exhaust gas , dust) capture. Further, the air filter of the present invention is an air filter which is excellent in balance between low pressure loss and high particle collection rate because of high heat resistance and high resistance to radical resistance (plasma resistance). Performance, regardless of the type of raw material gas and the evaporation mechanism of the substrate, can be used in various types Various types of CVD devices. Further, examples of the CVD apparatus include a thermal CVD apparatus, a plasma CVD apparatus, a photo CVD apparatus, and an MOCVD (metalorganoic CVD) apparatus.

In the air filter of the present invention, the average fiber of the PTFE fiber (a) is straight The diameter is from 10 nm to 50 μm, preferably from 100 nm to 5000 nm. When the average fiber diameter of the PTFE fiber (a) is within such a range, the pressure loss can be reduced, and the particle collection rate can be improved to improve the performance of the air filter.

Here, the average fiber diameter of the PTFE fiber (a) is The PTFE fiber (a) to be measured was randomly selected from the region observed by a scanning electron microscope (SEM), and subjected to SEM observation (magnification: 10,000 times). The region was arbitrarily selected from 10 PTFE fibers (a), and the measurement was selected. The arithmetic mean of the fiber diameters of the ten PTFE fibers (a) and based on the values of the obtained 10 fiber diameters.

As will be described later, when the PTFE fiber (a) is obtained by an electric field spinning method, The PTFE fiber (a) having a desired average fiber diameter can be obtained by appropriately adjusting the concentration of PTFE in the spinning solution, the environmental humidity at the time of production, the tip diameter of the spinning nozzle, the applied voltage, the voltage density, and the like. Further, in the electrospinning method, by using a spinning solution having a low PTFE concentration; reducing the ambient humidity; reducing the diameter of the front end of the spinning nozzle; increasing the applied voltage; or increasing the voltage density, etc., the PTFE fiber (a) The average fiber diameter tends to become smaller.

The "PTFE fiber (a)" usually contains PTFE fibers in an amount of 95 to 100% by weight, preferably 99 to 100% by weight, preferably 100% by weight. The air filter for a CVD apparatus according to the present invention exhibits plasma resistance (free radical resistance), heat resistance (especially, low heat shrinkability), and the like due to the properties of the PTFE fiber (a).

The method for producing the PTFE fiber (a) is as long as it is manufactured The method of the PTFE fiber having an average fiber diameter is not particularly limited, but it is preferably obtained by an electric field spinning (electrospinning) method. The electric field spinning method can easily obtain the PTFE fiber (a) having the average fiber diameter in the above range, and in the air filter of the present invention, when the PTFE fiber (a) obtained by such a method is used, it can be realized. High particle trapping rate, low pressure loss, high durability air filter for heat, free radicals, and harmful substances.

As the above-described electric field spinning method, it is possible to contain the above PTFE and For the spinning solution of the solvent and the necessary additives (fiber forming agent, ionic surfactant, viscosity adjusting agent, etc.), for example, a well-known electric field spinning method such as the method described in JP-A-2010/0193999 A1 is used. law.

The porosity (porosity) of the filter layer (a) is from the fluid flow path, The viewpoint of ensuring the strength of the filter material to prevent the pressure loss from increasing is preferably 0.60 to 0.95, preferably 0.70 to 0.90.

The basis weight of the filter layer (a) depends on the fiber diameter of the PTFE fiber, and is preferably from 1 to 200 g/m ² from the viewpoint of achieving high particle collection performance, low pressure loss, and strength of the filter medium. It is preferably from 10 to 100 g/m ² .

The thickness of the filter layer (a), although also depends on the fiber of the PTFE fiber The diameter is preferably from 5 μm to 200 μm from the viewpoint of achieving high particle trapping performance and low pressure loss.

Moreover, the void ratio, the basis weight and the thickness of the filter layer (a), When the PTFE fiber (a) is produced by the electric field spinning method, the spinning time is increased and the number of spinning nozzles is increased, which tends to be large.

The method for manufacturing an air filter for a CVD apparatus according to the present invention is There is a particular limitation, for example, a step of producing a PTFE fiber (a) by the electrospinning method as described above, and a step of forming the air filter by aggregating the PTFE fiber (a) into a sheet shape.

Moreover, the two steps can be performed independently of each other, or Simultaneously (that is, the PTFE fibers (a) are produced while being aggregated to form a sheet material to form a filter layer (a)).

Moreover, the air filter of the present invention may be a laminated support. The body layer (b) or the like is only composed of the filter layer (a) (single layer type air filter), and may be a support layer (b) on one side or two areas of the filter layer (a). (Laminar air filter).

Further, the laminated air filter described above can be implemented, for example, as follows a step of producing a PTFE fiber (a) having a specific average fiber diameter as described above; and, at least one surface of the support layer (b), agglomerating the PTFE fibers (a) into a sheet form to form a filter layer (a) ) The steps. The two steps may be carried out independently or simultaneously (that is, the PTFE fibers (a) may be formed while being aggregated on at least one surface of the support layer (b) to form a filter layer (a). ).

Moreover, as the support layer (b), it can be used in an air filter. A conventionally known support layer, for example, a mesh composed of iron, copper, stainless steel or the like, may, for example, be a nonwoven fabric composed of glass fibers, cellulose fibers, polyolefin fibers, nylon fibers, polyester fibers or the like. In particular, from the viewpoint of durability, the support layer (b) is preferably a nonwoven fabric comprising a mesh or a glass fiber composed of iron, copper, stainless steel or the like.

Further, the air filter of the present invention contains PTFE fibers (a) in addition to In addition to the filter layer (a), it may have a different material from the filter layer (a). More than one filter layer (c). In this case, the air filter of the present invention may be composed of the filter material layer (a) and one or more filter material layers (c), or one or more support layers (b) may be laminated. Adult. Since it is associated with prevention of clogging of the filter layer, it is preferable to collect dust (dust) of various particle sizes using a plurality of filter layers from the viewpoint of maintaining long-term performance of the air filter.

As the filter layer (c), from the viewpoint of durability, metality is preferred. A powdery filter material composed of a metal sintered powder, a mesh-shaped filter material composed of a sintered metal wire mesh, and a fluffy and non-woven filter material composed of metal fibers can be used.

Moreover, the air filter of the present invention is in a range that does not impair its performance. Within the circumference, previously known processing can be performed, for example, pleating processing can also be performed.

[Examples]

Hereinafter, the present invention will be described in more detail by way of examples, but the invention is not limited by the examples.

[Example 1]

The PTFE fiber (a) 1 composed only of PTFE was produced by the original electric field spinning method. The characteristics of the produced PTFE fiber (a) 1 were measured or evaluated based on the following "measurement method and evaluation criteria". The results obtained are shown in Table 1.

Next, the PTFE fiber (a) 1 was stacked (laminated) to prepare a filter material layer (a) 1 (10 cm in the longitudinal direction and 10 cm in the lateral direction). The characteristics of the produced filter material layer (a) 1 were measured or evaluated based on the following "measurement method and evaluation criteria". The results obtained are shown in Table 1.

[Measurement method, evaluation criteria] 1. <Average fiber diameter of PTFE fiber (a) 1 >

For the PTFE fiber (a) 1, the SEM observation area was arbitrarily selected and observed by SEM (device: S-3400N (manufactured by Hitachi HIGHTECH NOLOGIES), magnification: 10000 times), and 10 PTFE fibers were randomly selected ( a)1, an average (arithmetic mean) fiber diameter is calculated based on the measurement results of the PTFE fibers (a)1.

2. <thickness of filter layer (a) 1 >

The thickness of the filter layer (a) 1 was measured using LITEMATIC VL-50 (manufactured by Mitutoyo Co., Ltd.).

3. <The weight per unit area of the filter layer (a) 1 >

The basis weight (g/m ² ) of the filter material layer (a) 1 was measured in accordance with JIS L 1906 (2000).

4. <void rate>

The filter layer (a) 1 was cut into 4 cm square (4 cm in the longitudinal direction × 4 cm in the lateral direction) to prepare a test piece 1, and the weight (g) of the test piece 1 was measured. Next, the volume (cm ³ ) of the test piece 1 was calculated using the thickness measured by the item "2. <Thickness of the filter layer (a) 1>", and the calculated volume (cm ³ ) and the test were performed. The weight (g) of the sheet 1 was calculated as the density (g/cm ³ ). The void ratio was calculated based on the calculated density (g/cm ³ ) based on the following formula (I).

Void ratio = (true density of PTFE - density of test piece 1) 真 true density of PTFE (I)

(Either "true density of PTFE", "density of test piece 1", and "true density of PTFE" are "g/cm ³ "; in addition, "true density of PTFE" is 2.2. g/cm ³ ).

5. <Average flow diameter and average flow diameter pressure>

Semi-dry method based on ASTM E1294-89, using Galwick (15.9 dyn/cm) The average flow diameter and the average flow diameter pressure were measured for the immersion liquid.

The vertical axis represents the flow rate and the horizontal axis represents the aeration curve (dry curve) of the filter layer (a) 1 not immersed in the Galwick (impregnation liquid) supplied to the filter layer (a) 1; and immersed in Galwick ( Aeration curve (wet curve) of the filter layer (a) 1 of the immersion liquid). Further, the slope of the dry curve was calculated and a curve having a slope of 1/2 of the dry curve (semi-dry curve) was prepared.

Next, the pressure at the intersection of the wet curve and the semi-dry curve (average flow diameter pressure) is obtained and substituted into the following Washburn formula to calculate the average flow diameter d.

d=4 γ cos θ/P

(In the formula, θ represents the contact angle of the filter medium layer and the immersion liquid, γ [N/m] represents the surface tension of the immersion liquid, and P represents the average flow diameter pressure).

6. <Particle capture rate and pressure loss>

The particle collection rate was measured in accordance with JIS B 9908 for the filter layer (a) 1. At this time, the filter medium layer (a) 1 having a size of 200 mm × 200 mm was cut in place of the air filter unit, and as the dust for measurement, atmospheric dust having a specific particle diameter range as shown in Table 2 was used. When the particle collection rate was measured, the flow rate of air was set to a surface velocity of 5.3 cm/s. Further, at the same time as the measurement, the difference in pressure (that is, pressure loss) on the upstream side and the downstream side of the filter medium layer (a) 1 was measured using a differential pressure gauge. This measurement was changed to the flow rate of the air shown in Table 3.

[Embodiment 2]

The PTFE fiber (a) 1 was produced in the same manner as in Example 1, and then the PTFE fiber (a) 1 was deposited (laminated) to prepare a filter material layer (a) 2 (10 cm in the longitudinal direction, 10 cm in the lateral direction, 20 μm in thickness, and 0.76 in porosity). . Further, the thickness and void ratio of the filter medium layer (a) 2 were measured in the same manner as in Example 1. The filter layer (a) 2 was cut into a size of 40 mm (A) in the longitudinal direction and 40 mm (B) in the transverse direction to prepare a sample. The prepared sample was allowed to stand in an electric furnace (fixed-temperature drier DRA430DA (manufactured by ADVANTEC Toyo Co., Ltd.)) held at 260 ° C for 30 minutes without being fixed by a fixing device such as a frame. Subsequently, after taking out from the electric furnace and air-cooling to room temperature, the longitudinal length (a) and the lateral length (b) were measured as the dimensions after the heat treatment. The shrinkage ratio (%) in the longitudinal direction and the transverse direction was calculated based on the longitudinal length (A) and the lateral length (B) before the heat treatment, the length of the longitudinal length (a) and the transverse length (b) after the heat treatment, and the following formula. The results are shown in Table 4.

[Comparative Example 1]

In the second embodiment, the evaluation was carried out in the same manner as in the case of using the expanded PTFE (40 mm in the longitudinal direction, 40 mm in the lateral direction, 108 μm in thickness, and 0.89 in the void: POREFLON (registered trademark) MEMBRANE manufactured by Sumitomo Electric Industries Co., Ltd.) instead of the filter layer (a) 2 . Shrinkage rate after heat treatment at 260 °C. The results are shown in Table 4.

As shown in Table 4, it was found that the stretched PTFE in the comparative example produced shrinkage before and after the heat treatment at 260 ° C, and had a problem of shape stability, that is, heat resistance in a high temperature environment. On the other hand, it was found that the filter material layer (a) 2 of the present invention hardly shrinks in the heat treatment environment of 260 ° C and has high stability to the shape of heat. That is, it can be understood that the filter layer (a) 2 has heat resistance which can be used even in a high temperature environment.

[Example 3]

The PTFE fiber (a) 1 produced in Example 1 was deposited (laminated) to produce a filter layer (a) 3 (20 cm in the longitudinal direction, 20 cm in the lateral direction, and 59.5 μm in the thickness). Further, the thickness of the filter medium layer (a) 3 was measured in the same manner as in Example 1.

Next, the air filter (a) is produced by sequentially laminating the filter layer (a) 3, the stainless steel mesh as the support layer (b), and the steel wool as the filter layer (c), and the air is filtered. The device (a) is incorporated in the gas exhaust port of the plasma CVD apparatus for forming a ruthenium film, instead of the previous air filter. Here, the filter layer (c) functions as a prefilter, and the filter layer (c) of the air filter (a) is placed in the CVD apparatus. The side (that is, the filter layer (a) 3 is provided on the outer side of the CVD apparatus).

Next, the actual operation was performed for 30 days, and when the exhaust gas was discharged from the inside of the CVD apparatus to the outside, it was passed through the air filter (a). Here, the air filter (a) is exposed to a high temperature condition of 200 ° C by exhaust gas and contains a radical substance such as SiH ₃ or SiH ₂ in the exhaust gas.

After the completion of the actual operation, the filter layer (a) 3 is taken out and the surface of the filter layer (a) 3 (the exhaust gas inlet side (the inside of the CVD apparatus)) and the back surface (the exhaust gas outlet surface (the outer side of the CVD apparatus)) SEM observation (device: S-3400N (manufactured by Hitachi HIGHTECH NOLOGIES), magnification: 2000 times) was provided, and an electron microscope photograph was obtained. Further, the filter layer (a) 3 before being incorporated into the CVD apparatus was subjected to SEM observation using the same conditions to obtain an electron micrograph. The obtained electron micrographs are shown in Figures 1 to 3.

In addition, the average flow diameter (μm) and the average flow diameter were measured in the same manner as in Example 1 except that the filter layer (a) 1 was used instead of the filter layer (a) 1 . Pressure (psi). The results are shown in Table 5.

As shown in the first to third figures, the SEM photograph ("Before the actual machine is used") (Fig. 1) before the actual machine operation and the SEM photograph after the actual machine operation ("After the actual machine is used (surface)" 2) and "After the actual machine was used (back)" (Fig. 3)), it was found that the shape of the PTFE fiber (a) 1 constituting the filter layer (a) 3 did not change at all.

Moreover, as shown in the figure "After the actual machine is used (surface)" in Fig. 2, It is known that the particulate matter is trapped on the surface of the filter medium layer (a) 3 . That is, it can be understood that the filter layer (a) 3 has a function of trapping particles in the exhaust gas discharged to the outside from the inside of the CVD apparatus.

Further, as shown in Table 5, before and after the actual use of the machine, it was observed that the trapped particles caused a slight decrease in the average flow diameter and the increase in the average flow path pressure, but no large change was thought to be expected to damage the filter. . In other words, it can be understood that the filter layer (a) 3 has durability such as resistance to radical resistance and heat resistance required for the air filter for a CVD apparatus.

Claims (6)

An air filter for a CVD apparatus, comprising: a filter medium layer (a) comprising PTFE fibers (a); and the PTFE fibers (a) having an average fiber diameter of 10 nm to 50 μm. The air filter for a CVD apparatus according to claim 1, wherein the filter layer (a) has a thickness of from 5 μm to 200 μm. The air filter for a CVD apparatus according to claim 1 or 2, wherein the filter medium layer (a) has a void ratio of 0.60 to 0.95. The air filter for a CVD apparatus according to any one of claims 1 to 3, wherein the PTFE fiber (a) is obtained by an electric field spinning method. The air filter for a CVD apparatus according to any one of claims 1 to 4, wherein the support layer (b) is laminated on one or both sides of the filter layer (a). A CVD apparatus according to any one of claims 1 to 5, wherein the air filter for a CVD apparatus is provided in a raw material gas supply port and/or a gas exhaust port.