gasket

Abstract

Provided herein is a gasket (100) formed from two parts, a first part (11) made from an elastomer and a second part (21) made from a material having less gas permeable and less flexible properties than the elastomer, the second part being secured to the first part in a direction perpendicular or substantially perpendicular to the direction of gas permeation between the two components (31, 41). The gasket can reduce or prevent the permeation of small molecule gases, and thus the gasket is useful, for example, in sealing equipment for semiconductor wafer processing technology.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates to gaskets, particularly O-rings, that prevent gas transmission under high vacuum conditions and methods of forming the gaskets. Gaskets are useful as sealing components used in semiconductor wafer processing techniques. [Background technology]

[0002] In order to more fully describe the technical field to which this invention pertains, several patents and publications are cited herein, the entire disclosures of each of which are incorporated herein by reference.

[0003] Sealing components (O-rings, gaskets, etc.) are exposed to harsh conditions, such as high temperatures and many types of organic solvents and gases, some of which can be corrosive, reactive, or otherwise aggressive. Fluorinated elastomers are widely used in sealing components in various industries because they have desirable elastic properties, low chemical reactivity, and high heat resistance. Devices using sealing components formed from fluorinated elastomers can achieve high vacuum or pressure conditions because such sealing components can function effectively even when used under such harsh conditions.

[0004] Sealing components used in semiconductor manufacturing technology, such as chamber seals for vacuum or deposition process equipment, are exposed to special gases (e.g., deposition process gases or chamber cleaning gases) and plasma. Because semiconductor wafer processing is performed under high temperatures, such sealing components also require high heat resistance. Based on the excellent properties mentioned above, fluorinated elastomers are good candidates for use under harsh conditions, but gas permeation is an issue. This is because fluorinated elastomers can only permeate small molecular gases (e.g., O2 or N2) at a rate of only 1×10 -4Because metal can prevent gas permeation, all-metal gaskets are sometimes used for such purposes. However, because metal has relatively low flexibility, all-metal gaskets must be carefully seated and bolted in place to ensure optimal sealing. Furthermore, when metal gaskets are used, the flange that contacts the metal gasket must be polished to a mirror finish. Another conventional technique uses a combination of two gaskets: one highly heat-resistant perfluoroelastomer gasket and the other a partially fluorinated elastomer gasket with low gas permeability. However, because a nitrogen gas purge is required between the two seals, this technique is not an easy task to implement. Therefore, there is still an urgent need for a flexible sealing component that can prevent the permeation of small molecule gases.

[0005] US Pat. No. 9,290,838(B) discloses a diffusion-resistant metal-coated O-ring in which at least a portion of the surface of the O-ring is coated with a malleable metal coating. Summary of the Invention [Means for solving the problem]

[0006] Provided herein is a gasket useful in semiconductor wafer processing technology. The gasket is positioned between two components and can prevent or reduce the permeation of small molecule gases (e.g., O2 or N2) between the two components. The gasket of the present technology is formed from two parts. The first part is made of an elastomer (fluoroelastomer, particularly perfluoroelastomer), and the second part is made of a rigid material (such as metal) with low gas permeability. The second part is firmly fixed to the first part, so that gas permeation between the two components is substantially reduced or completely prevented. [Brief explanation of the drawings]

[0007] [Figure 1]1 is a cross-sectional view of a portion of one embodiment of a gasket of the present invention positioned between two components to be sealed. [Figure 1a] 2 is a cross-sectional view of FIG. 1, with arrows indicating the applied force sealing the two components with the gasket. [Figure 2] 10 is a cross-sectional view of a portion of another embodiment of a gasket of the present invention positioned between two components to be sealed. [Figure 2a] 3 is a cross-sectional view of FIG. 2, with arrows indicating the applied force sealing the two components with the gasket. [Figure 3] 10 is a cross-sectional view of a portion of yet another embodiment of a gasket of the present invention positioned between two components to be sealed. [Figure 3a] FIG. 4 is a cross-sectional view of FIG. 3, with arrows indicating the applied force sealing the two components with the gasket. [Figure 4] FIG. 2 is a plan view of the gasket of the present invention. [Figure 4a] 1 is a cross-sectional side view of a gasket of the present invention. [Figure 5] 1 is a cross-sectional side view of a gasket of the present invention in sealing engagement with two components. [Figure 5a] FIG. 1 is a cross-sectional perspective view of a gasket of the present invention in sealing engagement with two components. DETAILED DESCRIPTION OF THE INVENTION

[0008] The gasket of the present invention includes two components: (A) a first component made from an elastomer; and (B) a second component made from a material that has properties that are less gas permeable and less flexible than the elastomer.

[0009] The first component is made of an elastomer. Fluorinated elastomers are particularly preferred due to their excellent properties, such as desirable elasticity, low chemical reactivity, good solvent resistance, and high heat resistance. Fluoroelastomers (FKM) and perfluoroelastomers (FFKM) can be used. Conventional fluoroelastomers contain copolymerized units of tetrafluoroethylene, vinylidene fluoride, or another partially fluorinated comonomer, such as fluoro(methyl vinyl ether), and a cure site monomer. Conventional perfluoroelastomers contain copolymerized units of tetrafluoroethylene, perfluoro(methyl vinyl ether), and a cure site monomer. Suitable fluoroelastomers include, but are not limited to, those described in U.S. Patent No. 8,765,876 issued to Bish et al. The fluoroelastomer may be synthesized by the methods described in Kaiser, RJ, et al., "Synthesis of Transparent Fluorocarbon Elastomers: Effect of Crosslinker Type and Electron Beam Irradiation Level on Physical and Mechanical Behavior," Journal of Applied Polymer Science, Vol. 27, pages 957-968 (1982), and the references cited therein. Suitable perfluoroelastomers include, but are not limited to, those described in U.S. Pat. No. 6,281,296 issued to MacLachlan et al. and U.S. Pat. No. 6,191,208 issued to Kohtaro Takahashi, and may be prepared by the methods described in these references.

[0010] The first component, due to its desirable elastic properties, functions to prevent gas leakage (i.e., gas diffusion) and maintain high pressure or high vacuum within the device in which the gasket is used. Because the first component is made of a flexible material (elastomer), it provides flexibility and a smooth surface for the sealing structure when the gasket is fitted to the sealing component. When the gasket is used in the sealing structure, the first component is compressed to a linear compression rate of 3 to 40%, preferably 10 to 30%, along a line perpendicular to the radius of the gasket, which is the maximum diameter of the cross section of the first component. This line is shown, for example, as aa in Figures 4a and 5 and as an arrow in Figures 1a, 2a, and 3a. As used herein, the term "perpendicular" refers to a direction parallel to line aa.

[0011] The second component is made of a material that has lower gas permeability and flexibility than elastomers. While any material that meets this requirement can be used, metals and metal alloys are preferred due to their rigidity and low gas permeability. Metals or metal alloys that are less reactive to chamber cleaning gases or plasma are more preferred. In this regard, aluminum or aluminum alloys may be used. Metals of note for use in the second component are stainless steel 304, 316, and aluminum A1000, A5000, and A6000 series. The permeability of these metals to small molecule gases is considered to be zero, or at least substantially zero, when used at the thicknesses described herein. As used herein, the term "substantially zero" means a permeability greater than zero and less than 1×10 -8 It refers to pressures below 1 Pa.

[0012] The second part has a thickness. The thickness varies depending on the size of the first part and the material of the second part. The thickness should be such that when the gasket is positioned between the two components to be sealed, the second part does not break or undergo irreversible bending deformation due to the compressive forces shown as arrows in Figures 1a, 2a, and 3a. Such breakage or deformation may be observed by visual inspection. Alternatively, a high gas permeability may indicate that the second part is damaged.

[0013] For example, if the second component is made of aluminum, the thickness of the aluminum is preferably about 0.2 to about 10 mm when the cross-sectional diameter of the elastomer (first component) along line aa is 3.5±0.10 mm. Again, high gas permeability may indicate that the second component is insufficiently thick.

[0014] The second component acts as a gas permeation barrier to small molecular gases. The elastomer can essentially prevent air leakage, but a small amount of small molecular gases, such as oxygen or nitrogen gas, can permeate the elastomer. 1×10 of nitrogen or oxygen in a vacuum chamber -4 Even the permeability that results in pressures of Torr is sufficient to disrupt some processes, such as deposition processes or semiconductor wafer processes.

[0015] The second part is made of a less flexible material but should be in full contact with the surfaces of both components of the sealing structure. To ensure full contact, the second part can be compressed vertically, i.e., along the line indicated as aa in Figures 4a and 5 and as an arrow in Figures 1a, 2a, and 3a, to a linear compression of less than 5%.

[0016] The first part of the gasket must be firmly bonded to the second part of the gasket.

[0017] If the first part is made of perfluoroelastomer and the second part is made of metal or metal alloy, the gasket can be manufactured by the following process: (a) providing a metal component of a gasket (which means a second component comprising metals and metal alloys), the surface of which is to be bonded to a perfluoroelastomer is chemically or mechanically treated; (b) compression molding the curable perfluoroelastomer composition onto the surface of the metal part; It can be formed by:

[0018] In step (a), the surface of the metal part is chemically or mechanically treated to form a strong metal-perfluoroelastomer bond. Because perfluoroelastomers are chemically inert, bonding to a metal surface is difficult. A typical example of chemical pretreatment of a metal surface is an adhesion primer or bonding agent. Such chemical agents can be coated on the surface of a metal part to improve the bond strength between the perfluoroelastomer and the metal part. Another example of a strong bond between a metal and a perfluoroelastomer is the use of an anchor effect by roughening the metal surface, for example, by creating scratches or pores. Acid etching, zinc chromate treatment, sandblasting, laser etching, and anodizing can be used. When the metal is aluminum or an aluminum alloy, the method disclosed in European Patent No. 1,855,864(B) by Minowa et al. can be used to anodize the surface of aluminum (alloy) to form a porous surface.

[0019] In step (b), a perfluoroelastomer part (i.e., a first part) is formed on a metal part using the curable perfluoroelastomer composition. Usually, perfluoroelastomers are amorphous polymeric compositions having copolymerized units of at least two main perfluoromonomers. Typically, one of the main comonomers is a perfluoroolefin, and the other is a perfluorovinyl ether. Representative perfluoroolefins include tetrafluoroethylene and hexafluoropropylene. Suitable perfluorovinyl ethers include those of formula (I): CF2=CFO(RfO) n (Rf'O) m Rf” (I) In the formula, Rf and Rf' are different straight-chain or branched perfluoroalkylene groups of 2 to 6 carbon atoms, m and n are independently 0 to 10, and Rf'' is a perfluoroalkyl group of 1 to 6 carbon atoms.

[0020] Other suitable fluoroelastomers and perfluoroelastomers are described in the above-cited Bish, Kaiser, MacLachlan, and Takahashi references.

[0021] The curable perfluoroelastomer composition is compression molded onto the porous surface of a metal part. The mold is in the shape of a gasket. The metal part is placed in the mold before the curable perfluoroelastomer composition is placed in the mold. Molding is carried out under pressure and at elevated temperature for a time sufficient to at least partially cure (i.e., vulcanize or crosslink) the perfluoroelastomer and bond it to the metal surface. The bond is strengthened by allowing the perfluoroelastomer compound to flow under pressure into the porous surface structure of the metal before crosslinking. Optionally, the resulting perfluoroelastomer-metal part may be post-cured at elevated temperature for a time sufficient to improve the physical properties of the elastomer and the bond strength of the cured elastomer to the metal surface. Post-curing may be carried out in an air oven or in an inert atmosphere. Typical compression molding conditions are 4 to 8 minutes at a temperature of 180 to 220°C. Typical post-cure conditions are 5 to 48 hours at a temperature of 250 to 315°C. Similar molding processes are described in the MacLachlan and Takahashi patents cited above.

[0022] For example, when used to form a seal in a vacuum chamber or pressurized vessel, the gasket is placed between two components to seal the gap between the two components. Preferably, the first and second components are positioned such that the first component is proximal to the vacuum side of the two components and the second component is proximal to the external atmosphere side of the two components, such that when the gasket is installed as a seal between the two components, gas transmission between the two components is reduced or prevented.

[0023] Referring now to the drawings, in which like reference numerals indicate corresponding structures throughout the figures, and particularly to FIG. 1, a cross-sectional view of one embodiment of a gasket (100) of the present invention is shown. The gasket (100) is formed from an elastomer (11) and a metal (21), preferably aluminum, which are rigidly connected to each other. The gasket (100) is positioned between two components (31, 41) to seal the gap between the two components (31, 41). When the gasket is used in semiconductor manufacturing technology, the inner elastomer side (11) of the gasket (100) is exposed to vacuum or to special gases (such as deposition process gases or chamber cleaning gases) and plasmas present inside the sealed components (50). A second component, a metal or metal alloy (21), is positioned on the outside of the gasket (100) to prevent gas permeation. The metal or metal alloy component (21) is positioned vertically, perpendicular to the surfaces of the two components (31, 41).

[0024] In other words, the second part (21) is fixed to the first part (11), and the first part and the second part are positioned such that when the gasket (100) is installed as a seal between the two components (31, 41), the first part (11) is proximal to the vacuum or process side (50) of the two components (31, 41) and the second part (21) is proximal to the external atmosphere side of the two components (31, 41) so that gas permeation into the space (50) defined by the two components (31, 41) is reduced or prevented.

[0025] FIG. 2 shows a cross-sectional view of another embodiment of a gasket (100) formed from a metal component (21) and an elastomeric component (11). Similar to FIG. 1, the metal component is located on the exterior, and the elastomeric component is located on the interior (50) side of the gasket. Additionally, the cross-section of the gasket is generally circular. Advantageously, the overall view of the gasket shown in FIG. 2 resembles a conventional gasket formed from a fluorinated elastomer, such as a torus or O-ring. Thus, the gasket shown in FIG. 2 can be applied to conventional applications and provides the improved seal described above without requiring elaborate and expensive retooling to modify the structure of the sealing components (31, 41) of current equipment.

[0026] In particular, in Figures 1 and 2, the contact area between the elastomer (11) and the metal (21) is cylindrical with a circular cross section of constant diameter and a vertical axis, i.e., an axis perpendicular to the plane of the gasket and the surfaces of the two components (31, 41).

[0027] Referring now to FIG. 3, a cross-sectional view of another embodiment of the present invention is shown in which a gasket (100) is positioned between two components (31, 41) to be sealed. As in FIGS. 1 and 2, an elastomeric part (11) is positioned inside the gasket, proximal to the interior (50) of the sealed chamber. Also, as in FIG. 2, the overall view of the gasket (100) resembles that of a conventional gasket. However, the embodiment of FIGS. 1 and 2 is distinguished from the embodiment of FIG. 3 by the shape of the interface between the elastomer (11) and the metal (21). The elastomer-to-metal interface in FIG. 3 is not accurately depicted as a cylinder with a circular cross-section of a constant diameter and a vertical axis, i.e., an axis perpendicular to the surfaces of the two components (31, 41). Rather, this interface is curved. While its cross-section is circular, its diameter is not constant relative to the distance between the sealing components (31, 41). Any shape of contact is suitable for use in this orientation, provided that thorough contact and proper bonding between the elastomer (11) and the metal (21) can be achieved by the methods described herein.

[0028] 1a, 2a, and 3a, the embodiments of Figures 1, 2, and 3 have been replicated with the addition of arrows indicating the sealing force applied perpendicularly to the sealing components (31, 41). In all three of the illustrated embodiments, the second part (21) is oriented perpendicular to the direction of gas permeation between the two components. Gas moving from the exterior of the sealed chamber to its interior (50) must move in a direction represented by a vector having a component perpendicular to the perpendicular direction indicated by the arrows.

[0029] Those skilled in the art can design metal component 21 to accommodate the application of a specified magnitude and direction of force at a given linear compression. Design choices include the selection of the metal and cross-section of metal component 21. For example, compared to gasket 100 of Figures 1 and 1a, gasket 100 as shown in Figures 2 and 2a may be used for seals requiring a larger than typical force to be applied vertically, while gasket 100 as shown in Figures 3 and 3a may be used for seals requiring a smaller than typical force to be applied vertically.

[0030] 4, a plan view of gasket 100 shows lines bb and cc in the plane of gasket 100. Additionally, elastomeric part 11 is proximal to interior 50 of sealed components (31, 41), which are not shown in FIG.

[0031] Referring now to Figure 4a, this cross-sectional view of gasket 100 shows a vertical axis aa that is perpendicular to lines bb and cc in the plane of the gasket, lines bb and cc not shown in Figure 4a.

[0032] Referring now to Figure 5, the sealed structure includes two sealing components (31, 41) and a gasket (100). Each component (31, 41) has a surface parallel to the surface of the other component, and the gasket (100) is disposed between the two parallel surfaces to seal the components (31, 41) and prevent gas leakage into the interior (50). The second part (21) is fixed to the first part (11) in a direction perpendicular to the direction of the parallel surfaces of the components (31, 41). In other words, the second part (21) is fixed to the first part (11) in a direction parallel to line aa.

[0033] Referring now to Figure 5a, a cross-sectional perspective view of a gasket (100) in sealing engagement with two components (31, 41) shows the second part (21) forming continuous contact with the surface of each component (31, 41).

[0034] Although Figures 4 and 5a show circular gaskets such as torus or O-rings, the gaskets of the present invention may have any shape known for gaskets or required by the design of the equipment to be sealed. Other conventional shapes for gaskets include ovals and rectangles with rounded corners, e.g., squares.

[0035] Although not shown in the drawings, either or both sealing components (31, 41) may be provided with one or more holes in addition to the holes sealed by the gasket of the present invention. These holes may be sealed from gas permeation by the gasket of the present invention or by other means. For example, sealing components (31, 41) may be provided with holes for gas inlet valves, vacuum ports, or openings into which instruments may be inserted, including, but not limited to, heaters, pressure gauges, electrodes, and probes such as temperature probes, Langmuir probes, or QMS probes.

[0036] The following examples are provided to further illustrate the present invention. These examples, which represent preferred modes presently contemplated for carrying out the invention, are intended to illustrate, but not to limit, the invention. [Example]

[0037] Test sample Test sample 1: The newly developed gasket shown in Figure 1 Test sample 2: The newly developed gasket shown in Figure 2 Test Sample 3: Conventional O-ring made from perfluoroelastomer (AS568 228 O-ring made from FFKM) Test Sample 4: Conventional O-ring made from a fluorinated elastomer (FKM AS568 228 O-ring)

[0038] Test Sample 1 and Test Sample 2 were bonded parts of FFKM (11) and aluminum (21) made by the co-curing molding process. The curable perfluoroelastomer was prepared according to the methods described in the above-cited U.S. Patents 6,281,296 and 6,191,208 and EP 1,855,864(B). The bonding method is also disclosed in EP 1,855,864(B). Test Sample 3 and Test Sample 4 were obtained commercially.

[0039] Testing equipment and method for gas permeation through vacuum seals Test-1 The test instrument was a vacuum chamber with a stainless steel AS568 228 O-ring sized flange for vacuum sealing. A vacuum pump and a QMS (quadrupole mass spectrometer) were attached to the chamber. Ribbon heaters were attached around the chamber and a thermostatically controlled mantle heater was attached around the flange to heat the instrument to above 200°C.

[0040] The two-piece gaskets of the test samples (Test Samples 1, 3, and 4) were attached to the flanges of the instrument to create a vacuum seal. The chamber was heated to 1 × 10°C with the ribbon heaters around the chamber set to 100°C. -7 The chamber was placed in an ultra-vacuum level of 100 Pa. The ribbon heater constantly heated the chamber at 100°C. When the mantle heater around the flange was off, the flange temperature was 52°C due to heating by the ribbon heater around the chamber. The vacuum was maintained by continuously running the vacuum pump. While the heater around the chamber was set to 100°C, the temperature of the heater around the flange was increased to 200°C at a rate of 2.5°C / min by the mantle heater around the flange.

[0041] The air pressure inside the vacuum chamber resulting from seal permeation was measured by QMS when the temperature of the heater around the flange was recorded at 100° C., 150° C., and 200° C. At these temperatures, the partial pressures of N2 and O2 were also measured.

[0042] Test-2 An aluminum flange was also prepared for test sample 2. Due to the difference in thermal conductivity between stainless steel and aluminum, the starting temperature for the measurement was 66°C. To confirm the reproducibility of the temperature thermal cycle, transmission measurements were performed 10 times. Since the flange was made of aluminum, the surface of test sample 2 was inspected after the test using a 3D image measuring instrument, model VHX-7000, manufactured by KEYENCE Corp. in Itasca, IL, to confirm that there was no physical damage to the flange that would make it unsuitable for repeated use. No scratches were found on the surface.

[0043] Gas permeability (air, N2, and O2) test results. Test-1 The air permeability results are shown in Table 1, the N2 permeability results are shown in Table 2, and the O2 results are shown in Table 3. All gas permeabilities reported herein are in Pascals (Pa).

[0044] [Table 1]

[0045] [Table 2]

[0046] [Table 3]

[0047] Test-2 The air permeability results are shown in Table 4, the N2 permeability results are shown in Table 5, and the O2 results are shown in Table 6.

[0048] [Table 4]

[0049] [Table 5]

[0050] [Table 6]

[0051] After completion of Test 2, no damage to the flange was observed.

[0052] While certain preferred embodiments of the present invention have been described and specifically exemplified above, it is not intended that the present invention be limited to such embodiments. Rather, while many of the features and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, it is to be understood that the present disclosure is merely illustrative, and that changes may be made in details, particularly with respect to the shape, size, and arrangement of parts, within the principles of the invention to the fullest extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

1. 1. A gasket for sealing two components from gas transmission, said gasket comprising: (A) a first component comprising an elastomer; (B) a second component comprising a material that is less gas permeable and less flexible than the elastomer; Including, the first component comprises a perfluoroelastomer; the second component comprises aluminum or an aluminum alloy; the second component is secured to the first component, and the first component and the second component are positioned such that the first component is proximal to a vacuum side of the two components and the second component is proximal to an external atmosphere side of the two components, such that gas transmission between the two components is reduced or prevented when the gasket is installed as a seal between the two components. gasket.

2. The gasket of claim 1 , wherein the second part is oriented perpendicular to the direction of gas permeation between the two components.

3. The gasket of claim 1 , wherein the contact portion between the first component and the second component has a cylindrical shape.

4. 2. The gasket of claim 1, wherein the contact surface of the aluminum or aluminum alloy has pores, and at least a portion of the elastomer is inserted into the pores by compression molding.

5. 1. A method of manufacturing a gasket for sealing two components from gas transmission, the gasket comprising: (A) a first part made from an elastomer; and (B) a second part made from a metal or metal alloy; the first component comprises a perfluoroelastomer; the second component comprises aluminum or an aluminum alloy; The method comprises: (a) providing a metal part made of a metal or metal alloy, wherein the surface of the metal part to be bonded to a perfluoroelastomer is chemically or mechanically treated; (b) compression molding a curable perfluoroelastomer composition onto the surface of the metal component; Including, the second component is secured to the first component, and the first component and the second component are positioned such that the first component is proximal to a vacuum side of the two components and the second component is proximal to an external atmosphere side of the two components, such that when the gasket is installed as a seal between the two components, gas transmission between the two components is reduced or prevented.

6. A sealing structure comprising two components and the gasket of claim 1, wherein each component has surfaces facing parallel to each other; the gasket is disposed between the two surfaces to seal the component against gas leakage; the second part is fixed to the first part in a direction perpendicular to the direction of gas permeation between the two components; Sealed structure.

7. The sealing structure according to claim 6, wherein the first part is compressed to a linear compression rate of 3 to 40%.

8. The sealing structure of claim 6 , wherein the second part forms continuous contact with the surface of each component.

9. The sealing structure according to claim 6, which is used for high vacuum sealing of equipment used in a semiconductor manufacturing process or a flat panel display manufacturing process.

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