Silicon consumable cores for internal features in reaction-bonded ceramics

Abstract

To provide a method for manufacturing reaction-bonded ceramic components incorporating internal features.SOLUTION: A method according to the present invention for fabricating a reaction-bonded ceramic component having one or more internal features includes the steps of: fabricating a Si consumable core shape representing the feature to be formed; assembling the mold to maintain the position of the Si consumable core; casting a preform slurry around the Si consumable core to create a preform piece; and reaction bonding the preform piece to create the ceramic component having the internal feature.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 ceramic components that include internal features (e.g., channels). [Background technology]

[0002]

[0003] Conventional approaches to fabricating ceramic components for the semiconductor industry can be problematic, especially when they include internal features such as 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. 1B is a cross-sectional view of a reaction-bonded silicon carbide (RB-SiC) flow-through section fabricated by bonding two preform halves together using a SiC-based adhesive followed by reaction bonding, according to an embodiment of a disclosed example. [Figure 4]

[0010] 1 is a table illustrating properties of silicon relative to silicon carbide, according to an example embodiment of the disclosure. [Figure 5]

[0011] 10A-10C illustrate the use of a silicon consumable core at the interface of a preformed section to create a part with an internal channel, according to an example embodiment of the disclosure. [Figure 6]

[0012] 1A-1C are diagrams of the structure of a reaction-bonded silicon carbide (RB-SiC) ceramic component according to an example embodiment of the disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0006]

[0013] Reaction-bonded ceramic components containing internal features 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 features (e.g., channels), bonding multiple preform pieces using a silicon carbide (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 features.

[0007]

[0014] During conventional preform bonding operations such as those described above, microscopic spheres of excess SiC-based adhesive can protrude into features, such as channels, in the finished part. If the channels or other features are large (5 to 10 mm), the excess adhesive may not pose a problem. However, many next-generation designs have extremely small feature 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 features of this small size, making it difficult to fabricate parts with extremely small features. Thus, alternative bonding methods are needed.

[0008]

[0015] Reaction bonded pieces can be glass bonded to try to avoid the problem of excess adhesive, but this type of bond has poor corrosion resistance, poor thermal conductivity, poor electrical conductivity, and / or poor high temperature strength. Failure at high temperatures, if any post-processing is required, is also an issue.

[0009]

[0016] This disclosure presents a method for forming ceramic parts without the use of bonding agents such as SiC-based adhesives, such as caulking, thus eliminating the formation of balls that can clog small channels. Instead of pieces bonded together, internal channel reaction-bonded ceramics are formed in a single piece using a silicon consumable core, where the core is removed (i.e., consumed) during the process by melting or other means. In some embodiments, silicon in the shape of internal features (e.g., channels) is used in a preform and then heat treated, during which the Si melts and also infiltrates into the preform, thereby leaving open channels.

[0010]

[0017] The disclosed method is bond-free and therefore no bond lines are formed. Advantages of this method of fabrication may include: (1) the ability to fabricate channeled parts without bond lines; and / or (2) reduced manufacturing labor. In some embodiments, the silicon consumable core melts away a majority (>50%) of the silicon, and in other embodiments, melts away 75% or more, 85% or more, or 95% or more of the silicon.

[0011]

[0018] The disclosed method does not use adhesives or cements and further avoids the problems presented with glass bonding or other bonding techniques.

[0019] Contemplated reaction-bonded materials include, but are not limited to, silicon carbide (RB-SiC), boron carbide, diamond, pure carbon (as powder or fiber), and / or titanium diboride.

[0012]

[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 SiC formed in the reaction, and residual Si.

[0013]

[0021] The creation of reaction-bonded ceramic parts as described herein utilizes a preform. The preform is produced using a slurry that is formed into the desired shape, including both the inner and outer contours. In some embodiments, the ceramic part is reaction-bonded silicon carbide (RB-SiC) produced using a slurry containing SiC+C-based binder+deionized HO. 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.

[0014]

[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.

[0015]

[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.

[0016]

[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 channels and form adhesive spheres along the bottom, top, and / or sidewalls of the channels. 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 using a SiC-based adhesive and then reaction bonding them. In Figure 3, excess adhesive spheres are visible within the channels.

[0017]

[0025] Conventional reaction-bonded SiC materials with internal features, such as 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.

[0018]

[0026] The present invention forms features such as channels without the use of SiC-based adhesives such as caulking; therefore, spheres that can clog small channels are not formed. The channels are instead formed by placing a Si consumable core in a suitable mold and casting the preform slurry around the core. During reaction bonding, the Si melts and infiltrates into the preform, creating a ceramic body with channels that mirror the shape of the consumable core.

[0019]

[0027] The primary objective is to form features such as channels without adhesive spheres entering the channels. Other advantages are (1) continuous material, (2) extremely complex and tolerant internal features in addition to channels can be formed, and (3) custom internal feature roughness can be formed through replication from a core (since the feature will take the inverse shape of the consumable material used to form it). This disclosure discloses a method for creating reaction-bonded ceramic parts (such as silicon carbide (RB-SiC)) that include one or more internal features such as channels without excess material present within the feature. Thus, the disclosed method does not utilize adhesives or bonding agents. Instead, the method involves using a silicon consumable core to create the features. The disclosed method uses silicon in the shape of the internal features. This silicon (Si) is placed into a mold in the desired layout / orientation, and a slurry is poured around the Si. In some embodiments, the slurry is SiC + carbon-based binder + deionized HO. After casting the material to create the preform, the preform is infiltrated with molten Si. In this step, the Si melts and infiltrates further into the preform, leaving open channels. Because there is no "glue," there are no glue spheres that enter the feature, and therefore the feature remains substantially free of excess material (e.g., there is no excess silicon in the feature). Varying the time and temperature may yield different results.

[0020]

[0028] Silicon has a good coefficient of thermal expansion (CTE) match to SiC, resulting in a low stress process during infiltration / melting of the consumable core (where the part / preform remains intact in the process). Figure 4 is a table showing the CTE of silicon relative to silicon carbide.

[0021]

[0029] As discussed above, silicon (Si) consumable cores are placed into a mold in the desired layout / orientation, and a slurry is poured around the Si. This creates a green part from the slurry, which may be shaped in the mold. A drying / carbonization procedure then takes place, which may be performed under an inert 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.

[0022]

[0030] After the green part (green body) is created, the preform piece is processed by heating in the presence of silicon to create the final ceramic part. Heat is applied until the melting temperature of silicon is reached (~1,410°C) or higher. This step is usually performed in a vacuum furnace.

[0023]

[0031] Some embodiments of the disclosed method include the steps of: fabricating a shape from silicon representing the features to be formed as a silicon consumable core, assembling a mold to maintain the position of the silicon consumable core, casting a preform slurry around the silicon consumable core, and reaction bonding to produce a ceramic structure with internal features as described above. The temperature and length of time for the reaction bonding step both depend on the geometry of the structure.

[0024]

[0032] As discussed above, the disclosed methods demonstrate the formation of custom internal feature roughness, as the features take on the inverse shape of the consumable material used to form them. In some embodiments, the Si consumable core shape is formed through laser machining. In other embodiments, conventional machining (e.g., milling), erosive processes (e.g., waterjet machining), additive processes (e.g., 3D printing), and casting (e.g., sand casting) are used to form the Si consumable core shape.

[0025]

[0033] In an example of the disclosed method, a silicon consumable core is used at the interface of a mold section to create a part with internal features such as a channel. Figure 5 illustrates the first part of the process in which a Si consumable core (Si-CC) is prepared by laser cutting a Si wafer (panel 1), the Si consumable core is placed in the mold where the channel is desired (panel 2), the mold is fully assembled, and a slurry is poured into the mold to form a preform piece (panel 3), and the binder from the slurry is burned out to completely create an intact preform (panel 4). At this step, the silicon of the consumable core protrudes from the platform.

[0026]

[0034] The silicon consumable core becomes molten Si and is removed (i.e., consumed) by infiltration. In this process, the silicon within the core melts and infiltrates into the preform, leaving open channels.

[0027]

[0035] In some embodiments, the material used to make the consumable core is pure silicon (>98.8% by weight, %Si), while in other embodiments, Si-based alloys such as Si-Al or Si-Ti are used. If a Si-based alloy is used, the temperature will need to be adjusted accordingly.

[0028]

[0036] In some embodiments, the material used to make the consumable core has a designed roughness. Such a core is used in a mold where a feature is desired, and when the slurry is poured into the mold to form the preform piece, the designed roughness is replicated in the feature. The roughness may be specific to achieve particular flow characteristics.

[0029]

[0037] Figure 6 shows the structure of a reaction-bonded silicon carbide (RB-SiC) ceramic part made by the process disclosed herein. X-rays show the vacant channels (where the Si has been removed) and the microstructure of the vacant channels as well, showing the absence of all bond lines.

[0030]

[0038] In some embodiments, the amount of silicon consumable core consumed during the process corresponds to 25% or less by weight of Si remaining, with a lower limit of 0% Si (undetectable). 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 0-1% detectable silicon, and in other embodiments, there is no detectable silicon (0% remaining).

[0031]

[0039] Silicon can also be measured in the opposite manner, i.e., by the amount of Si consumed. In some embodiments, the amount of Si depletion corresponds to 75% or less by weight of Si consumed, with the lower limit being 100% Si consumed (undetectable). In other embodiments, 80% or less by weight of Si is consumed, 85% or less by weight of Si is consumed, 90% or less by weight of Si is consumed, 95% or less by weight of Si is consumed, 99% or less by weight of Si is consumed, 99.5% or less by weight of Si is consumed, or 99.9% or less by weight of Si is consumed. In some embodiments, 99-100% of Si is consumed, and in other embodiments, there is no detectable silicon (100% consumption).

[0032]

[0040] Advantages of using a silicon consumable core include, for example, (1) the ability to form internal channel reaction bonded ceramics without adhesive spheres (benefits related to enhanced flow behavior and the ability to form parts with extremely small channel sizes), (2) uniform material properties throughout the part due to the absence of typical bond lines, and / or 3) inherently hermetic since it is not a bonded part.

[0033]

[0041] This method may be used for ceramics where internal cooling channels or other features are required. It will be particularly valuable in applications with small feature sizes or where corrosion by silicon is 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, high-energy laser mirrors, and / or small orifice nozzles.

[0034]

[0042] 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]

[0043] 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 ceramic component having one or more internal features, comprising: fabricating a Si consumable core shape representative of the feature to be formed; assembling the mold to maintain the position of the Si consumable core; casting a preform slurry around the Si consumable core to create a preform piece; reaction bonding the preform pieces to produce the ceramic part having internal features; A method comprising:

2. The method of claim 1 , wherein the internal feature is a channel.

3. 10. The method of claim 1, wherein the Si consumable core shape is formed through at least one of conventional machining, laser machining, erosive processing, additive processing, and casting.

4. The method of claim 1 , wherein the Si consumable core is made of pure silicon.

5. The method of claim 1 , wherein the Si consumable core is made from a silicon alloy.

6. The method of claim 1 , wherein the Si consumable core is fabricated with a designed roughness.

7. The method of claim 1 , wherein a majority of the Si consumable core is consumed.

8. The method of claim 7, wherein 75% or more of the Si consumable core is consumed.

9. 9. The method of claim 8, wherein 85% or more of the Si consumable core is consumed.

10. 10. The method of claim 9, wherein 95% or more of the Si consumable core is consumed.

11. 11. The method of claim 10, wherein there is no detectable silicon from the Si consumable core after reaction bonding.

12. The method of claim 1 , wherein the one or more internal features are free of residual silicon.

13. 10. The method of claim 1, wherein reaction bonding the preform pieces comprises applying heat to melt the Si consumable core.

14. 14. The method of claim 13, wherein the step of applying heat is performed under vacuum.

15. 10. The method of claim 1, wherein the reaction-bonded ceramic component comprises one or more of silicon carbide (RB-SiC), boron carbide, diamond, pure carbon (as powder or fiber), and titanium diboride.

16. The method of claim 15, wherein the reaction-bonded ceramic component comprises silicon carbide (RB-SiC).

17. A reaction-bonded silicon carbide (RB-SiC) ceramic component made by the method of claim 16.

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