Dry preform bonding for internal channel reaction bonded ceramics.

Abstract

To provide a method for fabricating a reaction-bonded silicon carbide (RB-SiC) ceramic component that encompasses an internal channel.SOLUTION: The method can utilize diamond powder at an interface of two or more preformed sections.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE / INCORPORATION BY REFERENCE TO RELATED APPLICATIONS

[0001] Not applicable

[0002] Aspects of the present disclosure relate to ceramic components for the semiconductor industry. More specifically, certain embodiments of the disclosure relate to reaction-bonded silicon carbide (RB-SiC) ceramic components containing internal channels. [Background technology]

[0002]

[0003] Conventional approaches to fabricating ceramic components for the semiconductor industry can be problematic, especially when they involve internal channels.

[0004] Further limitations and drawbacks of conventional and traditional approaches will become apparent to those skilled in the art through a comparison of such systems with certain aspects of the present disclosure as described in the remainder of this application with reference to the drawings. Summary of the Invention

[0003]

[0005] As more fully set forth in the claims, a system and / or method for fabricating ceramic components for the semiconductor industry, as substantially shown and / or described in connection with at least one of the drawings.

[0004]

[0006] These and other advantages, aspects and novel features of the present disclosure, as well as details of illustrated embodiments thereof, will be more fully understood from the following description and drawings. [Brief explanation of the drawings]

[0005] [Figure 1]

[0007] FIG. 1 is a diagram of reaction-bonded silicon carbide according to an example embodiment of the disclosure. [Figure 2]

[0008] 1A-1C are diagrams of exemplary preforms bonded using a SiC-based adhesive, according to an embodiment of the disclosed examples. [Figure 3]

[0009] FIG. 1C is a cross-sectional view of an RB-SiC flow-through part fabricated by bonding two preform halves together using a SiC-based adhesive followed by reaction bonding, according to an embodiment of the disclosed example. [Figure 4]

[0010] 1 is a table illustrating properties of various forms of carbon, according to an example embodiment of the disclosure. [Figure 5]

[0011] 10A-10C illustrate the use of diamond powder at the interface of preformed sections to create a part with internal channels, according to an example embodiment of the disclosure. [Figure 6]

[0012] FIG. 10 is a diagram of a control sample having preform halves reaction bonded without diamond at the interface, according to an example embodiment of the disclosure. [Figure 7]

[0013] 10A-10C are diagrams of bond microstructures for samples made with two different diamond particle sizes at the interface, according to an example embodiment of the disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0006]

[0014] Reaction-bonded silicon carbide (RB-SiC) ceramic components containing internal channels are important to the semiconductor industry. Example components include, but are not limited to, water-cooled wafer tables, water-cooled collector mirrors, and water-cooled high-energy laser mirrors. Conventional parts may be fabricated by forming preform pieces / portions (e.g., two preform halves) with surface channels, bonding multiple preform pieces together using a SiC-based adhesive or bonding agent (a caulk-like material), and heat treating (e.g., ceramic firing, reaction bonding, etc.) to result in a finished component that is a unitary ceramic body with internal channels.

[0007]

[0015] During conventional preform bonding operations such as those described above, microscopic spheres of excess SiC-based adhesive can protrude into channels in the finished part. When channel sizes are large (5 to 10 mm), the excess adhesive may not pose a problem. However, many next-generation designs have extremely small channel sizes (e.g., <1 mm; in some embodiments, 0.25-1.0 mm or 0.5-1.0 mm). The excess adhesive spheres can restrict flow or even clog channels of this small size, making it difficult to fabricate parts with extremely small channels. Thus, alternative bonding methods are needed.

[0008]

[0016] The RB-SiC pieces may be glass bonded to try to avoid the problem of excess adhesive, but this type of bonding has poor corrosion resistance, poor thermal conductivity, poor electrical conductivity, and / or poor high temperature strength.

[0009]

[0017] This disclosure presents a method for forming bonds between silicon carbide (RB-SiC) ceramic parts without the use of bonding agents such as SiC-based adhesives, such as caulking, thus eliminating the formation of spheres that can clog small channels. The bond is formed by placing dry diamond powder between two or more preform pieces and then reactively bonding the pieces together to create the finished part. In some embodiments, there are two preform pieces, and in further embodiments, there are two preform half pieces. In other embodiments, there are more than two preform pieces. Upon reactive bonding of the preform pieces together (i.e., reactive infiltration with molten Si), the diamond powder expansively reacts with the Si to form SiC via Si+C→SiC, resulting in a bond line (i.e., interface) that is SiC-rich and where the silicon is largely reacted away. A strong bond line is formed without adhesive spheres entering the channels. Advantages of this method of fabrication may include (1) the ability to fabricate Si-free bond lines for improved corrosion resistance and properties, and / or (2) reduced manufacturing labor. In some embodiments, the bond lines have a majority (>50%) of the silicon reacted away, and in other embodiments, 75% or more of the silicon has reacted away.

[0010]

[0018] In the disclosed methods, dry diamond powder is used, i.e., diamond powder is used without further additives. In some embodiments, no medium or carrier (i.e., solvent) for the diamond powder is used. In addition, the reaction bonding occurs under vacuum (the vacuum should remove any residual moisture, such as from room humidity, etc.). In other embodiments, the reaction may be carried out under an inert atmosphere and / or in a humidity-controlled environment.

[0011]

[0019] The disclosed method does not use adhesives or cements and further avoids the problems presented with glass bonding or other bonding techniques.

[0020] Figure 1 is a diagram of reaction-bonded silicon carbide (RB-SiC, also called SiSiC). Referring to Figure 1, reaction-bonded SiC ceramic is fabricated by reactive infiltration of molten Si into a SiC+carbon preform. During infiltration, the molten Si reacts with the carbon to form additional SiC (Si+C→SiC), bonding the structure together. The final composite consists of the original SiC, the reaction-formed SiC, and residual Si.

[0012]

[0021] The creation of reaction-bonded silicon carbide (RB-SiC) ceramic parts as described herein utilizes a preform. The preform is created using a slurry (SiC + C-based binder + deionized HO) that is formed into the desired shape, including both the inner and outer contours. The preform may be fabricated as a green part, which is then further engineered to end up as a finished ceramic part. In some embodiments, internal channels are present in the finished part.

[0013]

[0022] 2 shows exemplary preforms bonded using a SiC-based adhesive (a caulk-like mixture of SiC particles and carbon-based additives). Specifically, these preform assemblies are reaction bonded to produce ceramic parts with internal channels by first gluing the two parts of the part together and then performing a reaction bonding process. In some embodiments, the preform comprises a body portion and a cover portion, as shown in FIG. 2.

[0014]

[0023] Additionally, Figure 2 shows the bond line microstructure after the preforms have been bonded using a SiC-based adhesive. The microstructure depicts a sufficiently tight bond line that indicates a hermetic seal, allowing fluid to be used to control the temperature of the part during use in a vacuum environment.

[0015]

[0024] SiC-based adhesives for preform bonding are sometimes formulated to have a caulk-like viscosity. These adhesives may contain SiC powder, a high-carbon organic liquid, and a rheology modifier. In practice, more adhesive than needed is applied to the interface. This excess adhesive prevents any gaps in the bond line. However, the excess adhesive will protrude into the channel and form adhesive spheres along the bottom, top, and / or sidewalls of the channel. These spheres can affect flow characteristics, especially in part designs with small channels (e.g., <1 mm, see above). Figure 3 illustrates a cross section of an RB-SiC flow-through part fabricated by bonding two preform halves together using a SiC-based adhesive followed by reaction bonding. In Figure 3, excess adhesive spheres are visible within the channel.

[0016]

[0025] Conventional reaction-bonded SiC materials with internal channels are often assembled as follows: (1) multiple preforms are bonded together using a SiC-based adhesive, and (2) the preform assembly is reaction-bonded to produce a flow-through ceramic (i.e., a material with internal channels). As discussed above, a problem with the conventional method is that excess adhesive forms spheres that protrude into the channels.

[0017]

[0026] In this disclosure, a method is disclosed for producing a reaction-bonded silicon carbide (RB-SiC) ceramic component containing one or more internal channels without excess material present within the channels. Therefore, the disclosed method does not utilize an adhesive or bonding agent. Instead, the method involves joining (assembling) two or more preformed sections with dry diamond powder and reaction-bonding the preformed sections. In the disclosed method, diamond reacts with Si (whereas SiC does not react in conventional methods). In this method, the sections become bonded due to the Si+C (diamond) → SiC reaction. The interface between the sections includes a bond line. Due to the significant expansion as the diamond reacts to form SiC, a bond line with low residual Si content, having 25% or less silicon by weight, is produced. Because there is no "glue," there are no glue spheres that enter the channel, and therefore the channel remains substantially free of excess material (e.g., no excess silicon is present within the channel). Varying the time and temperature may yield different results.

[0018]

[0027] Carbon can exist in several forms, including carbon black, graphite, and diamond. Diamond is a dense form of carbon, and a given specific volume contains more moles of carbon than other forms of carbon. Thus, the expansion (volume increase) in the Si + diamond → SiC reaction is large, allowing gaps between preforms to be filled. The supply of silicon is in excess of what diamond can react with. Figure 4 is a table showing the properties of various forms of carbon.

[0019]

[0028] As discussed above, green parts may be made by creating a slurry of water and a carbon-based binder, which is then formed into a mold (or cast into bricks for later machining). The slurry is frozen, dried, or both to remove the solvent and solidify the green part. A drying / carbonization procedure is then performed, which may be performed under a nitrogen atmosphere. In some embodiments, the temperature range for this step is from about 260°C to about 371°C (about 500°F to about 700°F). During the carbonization procedure, the carbon-based binder is decomposed.

[0020]

[0029] After the green part (green body) is created, two or more preform pieces are assembled to create the finished ceramic part. This step is usually done in a vacuum furnace. Dry diamond powder is applied to the interface of two or more preform pieces, and heat (usually with a vacuum) is applied. Heat is applied until the melting temperature of silicon is reached (~1,410°C) or higher.

[0021]

[0030] When used to create parts with internal channels, the use of diamond powder at the interface of two or more preformed pieces instead of SiC-based adhesives allows for reactive bonding without excess material within the channels. The diamond powder may be applied directly to the bonding surfaces of the two or more preformed pieces and by simple brushing (e.g., "painting" with a brush) or by other methods to the surfaces of the preformed pieces. Other methods of applying diamond powder include, but are not limited to, screen printing, using a low vapor pressure liquid as a carrier, powder coating (if the diamonds are of a sufficiently small particle size), dusting, and aerosol-attaching to the surface to attach diamonds larger than a certain size (10 μm). In some embodiments, masking may be used to prevent the diamond powder from entering the channels.

[0022]

[0031] In some embodiments of the disclosed method, a preform having half of a channel is prepared, and the bonding surface is then coated with diamond powder (by brushing the powder onto the surface). The preform halves are then assembled and subsequently reaction bonded. The microstructure of the bond line is then inspected. FIG. 5 illustrates the use of diamond powder at the interface of the preformed sections to create a part with internal channels. In some embodiments, the bonding surface includes all surfaces between two or more matching pieces (excluding all internal channels). In other embodiments, the bonding surface may include a portion of the surfaces between two or more matching pieces (excluding all internal channels).

[0023]

[0032] A control sample was created for comparison without an interface. To create this control, two preforms were placed on top of each other (with only air or space between them) and the process was performed. In this control sample, the gap ends up being filled with Si metal. The Si bond line is not ideal; this bond can have low strength, low stiffness, and / or increased susceptibility to corrosion (Si is more susceptible to corrosion than SiC). Figure 6 shows a control sample with reaction-bonded preform halves without diamond at the interface. The gap in Figure 6 is due to uneven surfaces resulting from machining these parts in the green state. An unacceptable Si bond line is shown. This bond is unacceptable because the bond is weak and Si is susceptible to corrosion.

[0024]

[0033] Further example methods of fabrication are generally described below, and properties of reaction-bonded silicon carbide (RB-SiC) ceramic components may be evaluated.

[0034] The diamond powder used at the interface can have a variety of particle sizes. In some embodiments, the diamond powder particle size is between about 3 μm and 200 μm; in other embodiments, the diamond powder particle size is between about 3 μm and 150 μm, about 3 μm and 100 μm, about 3 μm and 50 μm, about 10 μm and 200 μm, about 50 μm and 200 μm, or about 100 μm and 200 μm. In one embodiment, the diamond powder particle size is between about 3 μm and 30 μm; in another embodiment, the diamond powder particle size is between about 3 μm and 10 μm. Given a constant time above the melting point of Si, less SiC may be formed from larger sizes.

[0025]

[0035] Figure 7 shows the bond line microstructure for samples fabricated with two different diamond particle sizes, 6 μm and 22 μm, at the interface. For both samples, a satisfactory bond interface (bond line) is achieved, although more reaction is seen in the 6 μm sample. This case shows excellent complete infiltration, i.e., no porosity and low amounts of Si, which, among other benefits, means less corrosion in the expected environment.

[0026]

[0036] The larger surface area of ​​the 6 μm diamond powder results in a higher level (more reaction) of Si+C→SiC reaction, creating a bond line between the SiC and diamond with little or no Si present within the bond line. A bond line with reduced amounts of Si present is desirable for increased stiffness and corrosion resistance, as well as to prevent Si from leaching into all channel features.

[0027]

[0037] In some embodiments, the amount of Si reduction is at a lower limit of 0% Si (undetectable), corresponding to 25% or less by weight of Si remaining. In other embodiments, 20% or less by weight of Si remaining, 15% or less by weight of Si remaining, 10% or less by weight of Si remaining, 5% or less by weight of Si remaining, 1% or less by weight of Si remaining, 0.5% or less by weight of Si remaining, or 0.1% or less by weight of Si remaining. In some embodiments, there is no detectable silicon (0% remaining).

[0028]

[0038] Silicon can also be measured in the opposite manner, i.e., by the amount of Si that reacts away (reacts away) during the reactive bonding process. In some embodiments, the amount of Si reduction corresponds to 75% or less by weight of Si removed, with the lower limit being 100% silicon removed (undetectable). In other embodiments, 80% or less by weight of Si is removed, 85% or less by weight of Si is removed, 90% or less by weight of Si is removed, 95% or less by weight of Si is removed, 99% or less by weight of Si is removed, 99.5% or less by weight of Si is removed, or 99.9% or less by weight of Si is removed. In some embodiments, there is no detectable silicon (100% removal).

[0029]

[0039] The small surface area of ​​the 22 μm diamond allows little reaction to occur, resulting in bond lines of SiC, diamond, and residual Si. Some of the Si present may be due to the fact that the 6 μm diamond powder fits more snugly between the grains on the bonding surface of the preform than the 22 μm diamond powder.

[0030]

[0040] For example, the surface area (or surface available for reaction) of a given volume can be calculated as follows:

[0031]

number

[0032] Here, SA represents the surface area and d represents the diameter. The ratio gives an expression of how reactive a particle is, and the various particle sizes may be discussed in terms of strict size.

[0041] Advantages of using diamond powder at the interface include, for example, 1) the ability to form bond lines in internal channel reaction-bonded ceramics without adhesive spheres within the channels (benefits related to enhanced flow behavior and the ability to form parts with extremely small channel sizes); 2) the ability to form Si-free bond lines via SiC+Diamond→SiC reaction (most if not all of the Si is unreacted, which is advantageous for improved corrosion resistance and stiffness, as well as preventing Si from leaching into all channel structures); and / or 3) improved manufacturing efficiency (no need to prepare SiC-based adhesives and no effort to apply adhesive to preforms).

[0033]

[0042] Applications of this bonding technique may be used for ceramics where internal cooling channels are required. Particular value lies in applications with small channel sizes or where corrosion by silicon would be an issue. Key areas include, but are not limited to, water-cooled thermal management components, water-cooled semiconductor wafer chucks and electrostatic chucks, heat exchangers, petrochem valve bodies, and / or high-energy laser mirrors.

[0034]

[0043] As used herein, "and / or" means any one or more of the items in the list connected by "and / or." As an example, "x and / or y" means any element of the three-element set {(x), (y), (x, y)}. In other words, "x and / or y" means "one or both of x and y." As another example, "x, y, and / or z" means any element of the seven-element set {(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}. In other words, "x, y, and / or z" means "one or more of x, y, and z." As used herein, the term "exemplary" means serving as a non-limiting example, instance, or illustration. As used herein, the terms "etc.", "eg," and "for example" place out of a list of one or more non-limiting examples, instances, or illustrations.

[0035]

[0044] While the present invention has been described with reference to certain embodiments, it will be apparent to those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. 1. A method of making a reaction-bonded silicon carbide (RB-SiC) ceramic component having one or more internal channels, comprising: fabricating a preform piece having a surface channel, the preform piece comprising SiC and carbon; placing diamond powder on the bonding surface of the preform piece; assembling the preform pieces; reactively bonding the preform pieces to produce the ceramic part having an internal channel, the step resulting in a bond line between the preform pieces; wherein the diamond powder has a particle size between about 3 μm and 30 μm.

2. 10. The method of claim 1, wherein no adhesives or cements are used.

3. 10. The method of claim 1, wherein the preform piece comprises two halves of a final ceramic part.

4. The method of claim 2 , wherein the preform piece includes a body portion and a cover portion.

5. 10. The method of claim 1, wherein Si is reacted out of the bond lines.

6. 5. The method of claim 4, wherein a majority of the Si reacts away from the bond lines.

7. 7. The method of claim 6, wherein 75% or more of the Si reacts away from the bond lines.

8. 8. The method of claim 7, wherein 85% or more of the Si reacts away from the bond lines.

9. 9. The method of claim 8, wherein greater than 95% of the Si reacts away from the bond lines.

10. 10. The method of claim 9, wherein there is no detectable silicon in the bond lines.

11. The method of claim 1 , wherein the one or more internal channels do not contain excess silicon.

12. The method of claim 1 , wherein the diamond powder has a high surface area.

13. 10. The method of claim 1, wherein the diamond powder has a particle size between about 3 μm and 10 μm.

14. 10. The method of claim 1, wherein the diamond powder is dry.

15. 10. The method of claim 1, wherein no medium or carrier is used for the diamond powder.

16. 2. The method of claim 1, wherein the step of depositing diamond powder comprises applying the powder directly to the preform piece.

17. 10. The method of claim 1, wherein the step of reactively bonding the preform pieces includes applying heat to melt the silicon.

18. 20. The method of claim 17, wherein the step of applying heat occurs under vacuum.

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