Patent Application
20210242049
The present invention relates to an apparatus comprising a thermal leveler. In particular, the present invention relates to an apparatus with a thermal leveler that is detachable and removable from the apparatus.
Thermal pyrolytic graphite (TPG) based thermal levelers or spreaders are used in various heat dissipating, leveling, spreading, and focusing applications along with a heater or cooler. The goal of using these levelers is to achieve a desired temperature profile utilizing the enhanced thermal conductivity of the TPG material. These levelers can be in the form of either naked TPG or an encapsulated TPG structure, i.e., TPG encapsulated by a metal, semimetal, ceramic or alloy such as, for example, aluminum, copper, stainless steel, silicon, aluminum nitride, aluminum oxide or tungsten-copper respectively. TPG based thermal spreaders are typically used to cool the high-end electronics to improve the reliability of the system. In such applications, the thermal spreaders provides undiminished performance over the lifetime of the system, hence the thermal spreader is part of the capital expenditure.
TPG based thermal levelers are used in the production of semiconductor equipment. Many semiconductor processes are typically performed in a vacuum environment, i.e., a sealed chamber containing an assembly for supporting the wafer substrate(s) disposed therein. In a semiconductor process, a heating apparatus typically includes a ceramic support that may have electrodes disposed therein to heat the support, and additionally may have electrodes that electrostatically hold the wafer or substrate against the ceramic support, i.e., electrostatic chuck or ESC (also sometimes called susceptors). A semiconductor device fabrication process can take place in the chamber, including deposition, etching, implantation, oxidation, etc. As an example of a deposition process is a physical vapor deposition (PVD) process, known as sputter deposition, in which a target generally comprised of a material to be deposited on the wafer substrate is supported above the substrate, typically fastened to a top of the chamber. Plasma is formed from a gas such as argon supplied between the substrate and the target. The target is biased causing ions within the plasma to be accelerated toward the target. The ions of the plasma interact with the target material, and cause atoms of the material to be sputtered off, travel through the chamber toward the wafer, and redeposit on the surface of a semiconductor wafer that is being processed into integrated circuits (IC's). Other deposition processes may include, but are not limited to, plasma enhanced chemical vapor deposition (PECVD), high density plasma chemical vapor deposition (HDP-CVD), low pressure chemical vapor deposition (LPCVD), sub-atmospheric pressure chemical vapor deposition (SACVD), metal organic chemical vapor deposition (MOCVD), molecular beam evaporation (MBE), etc.
In some of the above processes it is desirable to heat the wafer by heating the support. In some of the other cases, heat generated on the wafer due to the process needs to be removed. The chemical reaction rate of the materials being deposited, etched, implanted, etc., is controlled to some degree by the temperature of the wafer. Undesirable unevenness in deposition, etching, implantation, etc., over a face of the wafer can easily result if the temperature of the wafer across its area varies too much. In most cases, it is highly desirable that deposition, etching, implantation be uniform to a nearly perfect degree since otherwise the IC's being fabricated at various locations on the wafer will have electronic characteristics that deviate from the norm more than is desirable.
In these applications, the thermal leveler helps to dissipate the heat in the lateral direction and improve the temperature distribution across the entire wafer. The thermal leveler, however, is exposed to corrosive process chemistries. This corrosive environment wears the thermal leveler or the component containing the leveler, thus the leveler or the component containing the leveler becomes “consumable,” i.e. the leveler needs to be replaced with a newly made component as the performance deteriorates. Replacement can be initiated by diminished performance of the thermal leveler or failure of some other sub-components of the component such as the heater or corrosion of the leveler encapsulating the thermal leveler causing contamination or particle generation. Corrosion of the encapsulating layers of the leveler can also cause pitting and/or can push the flatness out of specification. These mechanisms can diminish the thermal performance of the leveler by inducing poorer contact with the wafer/substrate. Although replacing the old & worn leveler with a newly made leveler or a newly made component with the leveler works technically, it is not a viable solution economically, as the cost of manufacturing the leveler is very high. Cost of the leveler is high because of the number of batch processes involved in the manufacturing process. Manufacturing involves multiple steps of bonding, machining, lapping, and finishing. In addition to these processes, the TPG material cost is high because of batch processes such as CVD and high temperature treatment.
The following presents a summary of this disclosure to provide a basic understanding of some aspects. This summary is intended to neither identify key or critical elements nor define any limitations of embodiments or claims. Furthermore, this summary may provide a simplified overview of some aspects that may be described in greater detail in other portions of this disclosure.
Provided is an apparatus suitable for supporting a substrate in a process chamber or other application and providing a desired thermal leveling profile. The apparatus is configured to provide a thermal leveler that is detachable from the apparatus. As such, the thermal leveler may be removed from the apparatus when a portion of the apparatus, e.g., an outer surface of the apparatus, has been deteriorated (e.g., corroded, consumed, etc.) to a point that the performance of the apparatus makes it no longer suitable for use. The thermal leveler can be removed from the apparatus and reused by transferring to another apparatus to provide a desired thermal leveling profile.
In one aspect, provided is an apparatus for supporting a substrate comprising a cover plate having an upper surface for supporting a substrate and a lower surface opposite the upper surface, and a thermal leveler comprising thermal pyrolytic graphite, the thermal leveler disposed adjacent to the lower surface of the cover plate and detachable from the coverplate.
In one aspect, provided is an apparatus comprising a thermal leveler releasably associated with a cover plate.
In one embodiment, the thermal leveler is releasably associated with the cover plate via a clamp, a bolt, a thread, a cam lock, a retaining groove, a retaining ring, a spring, a vacuum, electrostatic forces, electromagnetic forces, magnetic forces, an adhesive, a solder, or a paste.
In one embodiment, the thermal leveler is disposed between the cover plate and the base plate.
In one embodiment, the thermal leveler is detachably associated with the base plate.
In on embodiment, the base plate comprises a lower surface, one or more sidewalls extending around the perimeter of the base plate, and an opening defined between the one or more side walls, the thermal leveler disposed within the opening, and the one or more sidewalls having a threaded surface adjacent an upper end of the one or more sidewalls; wherein the cover plate is sized to fit within the opening of the base plate and includes a threaded side surface to engage the threaded surface of the base plate.
In one embodiment, the base plate comprises an upper surface, a lower surface, and a threaded side surface, the upper surface supporting the thermal leveler; the cover plate includes an upper surface, and one or more side walls extending downwardly from the upper surface of the cover plate and extending around the perimeter thereof, and an opening defined between the one or more side walls and sized to surround the thermal leveler and the base plate, wherein the one or more walls of the cover plate include a threaded surface to engage the threaded surface of the base plate.
In one embodiment, the cover plate includes one or more apertures; the thermal leveler includes one more apertures aligned with the one or more apertures of the cover plate; and the base plate includes one or more recesses aligned with the one or more apertures of the thermal leveler, wherein the cover plate, thermal leveler, and base plate are releasably connected to one another via fasteners disposed through the one or more apertures of the cover plate and the thermal leveler and the recesses of the base plate
In one embodiment, at least one of the fasteners is a pin that locks into one of the one or more recesses of the base plate
In one embodiment, at least one of the one or more recesses in the base plate has a threaded surface, and at least one of the fasteners is a threaded fastener suitable for threaded engagement of the at least one or more recesses with the threaded surface.
In one embodiment, an upper surface of the thermal leveler includes a recess, and a lower surface of the cover plate includes a projection aligned with and sized to mate with the recess in the upper surface of the thermal leveler.
In one embodiment, the thermal leveler comprises thermal pyrolytic graphite.
In one embodiment, the thermal leveler comprises a sheet of thermal pyrolytic graphite disposed between an upper sheet and a lower sheet.
In one embodiment, the thermal leveler is encapsulated by a cover layer.
In one embodiment, the upper sheet, the lower sheet, or the cover layer are independently chosen from a metal or ceramic material.
In one embodiment, the upper sheet, the lower sheet, or the cover layer are independently chosen from aluminum, copper, silver, gold, nickel, beryllium, tin, lead, steel, a steel alloy, copper-tungsten, copper-molybdenum, Invar, aluminum-beryllium, tin-lead; an oxide, nitride, carbide, carbonitride or oxynitride of elements selected from a group consisting of B, Al, Si, Ga, Y, refractory hard metals, transition metals.
In one embodiment, the thermal leveler comprises plural sheets of thermal pyrolytic graphite.
In one embodiment, the plural sheets of thermal pyrolytic graphite with graphene basal planes parallel or perpendicular to the substrate surface.
In one embodiment, the apparatus comprises a plurality of thermal levelers.
In one embodiment, the plurality of thermal levelers comprises thermal pyrolytic graphite with graphene basal planes parallel or perpendicular to the substrate surface.
In one embodiment, the base plate includes a heater and/or a cooler.
In one embodiment, the apparatus comprises an electrode disposed therein.
In another aspect, provided is a process for heating or cooling a substrate comprising heating or cooling a substrate disposed on the upper surface of the cover plate of any of the previous embodiments.
In one embodiment, the process comprises heating the substrate to an end point, removing the substrate from the apparatus, releasing the cover plate from the thermal leveler, providing a fresh cover plate and releasably connecting it to the thermal leveler, and providing a second substrate to the apparatus and heating the second substrate.
The following description and the drawings disclose various illustrative aspects. Some improvements and novel aspects may be expressly identified, while others may be apparent from the description and drawings.
The accompanying drawings illustrate various systems, apparatuses, devices and related methods, in which like reference characters refer to like parts throughout, and in which:
Reference will now be made to exemplary embodiments, examples of which are illustrated in the accompanying drawings. It is to be understood that other embodiments may be utilized and structural and functional changes may be made. Moreover, features of the various embodiments may be combined or altered. As such, the following description is presented by way of illustration only and should not limit in any way the various alternatives and modifications that may be made to the illustrated embodiments. In this disclosure, numerous specific details provide a thorough understanding of the subject disclosure. It should be understood that aspects of this disclosure may be practiced with other embodiments not necessarily including all aspects described herein, etc.
As used herein, the words “example” and “exemplary” means an instance, or illustration. The words “example” or “exemplary” do not indicate a key or preferred aspect or embodiment. The word “or” is intended to be inclusive rather than exclusive, unless context suggests otherwise. As an example, the phrase “A employs B or C,” includes any inclusive permutation (e.g., A employs B; A employs C; or A employs both B and C). As another matter, the articles “a” and “an” are generally intended to mean “one or more” unless context suggest otherwise.
As used herein, the “heating apparatus,” may be used interchangeably with “treating apparatus,” “heater,” “electrostatic chuck,” “chuck,” or “processing apparatus,” “pedestal,” upper or bottom electrode, referring to an apparatus containing at least one heating and/or cooling element to regulate the temperature of the substrate supported thereon, specifically, by heating or cooling the substrate.
As used herein, the term “substrate” refers to the semiconductor wafer or the glass mold being supported/heated by the processing apparatus of the invention. As used herein, the term “sheet” may be used interchangeably with “layer.”
As used herein, the term “circuit” may be used interchangeably with “electrode,” and the term “heating element” may be used interchangeably with “heating electrode,” “electrode,” “resistor,” “heating resistor,” or “heater.” The term “circuit” may be used in either the single or plural form, denoting that at least one unit is present.
A thermal leveler may have multiple zones. Temperatures of different zones can be different based on the configuration and layout of TPG (as exemplified in
In a plasma chamber for processing substrates such as semiconductor wafers or glass lenses, the substrate temperature significantly affects the process. For a processing apparatus to uniformly regulate the temperature of the substrate being treated, it is desirable for the apparatus to provide temporal and spatial control of the surface temperature of the substrate. Graphite is an anisotropic material with a unique ability to direct heat in a preferred direction. Thermal pyrolytic graphite (TPG) is a unique graphite material consisting of crystallites of considerable size, the crystallites being highly aligned or oriented with respect to each other and having well ordered carbon layers or a high degree of preferred crystallite orientation. TPG may be may be used interchangeably with “highly oriented pyrolytic graphite” (“HOPG”), or compression annealed pyrolytic graphite (“CAPG”). TPG is extremely thermally conductive with an in-plane (a-b direction) thermal conductivity greater than 1000 W/m-K, while the thermal conductivity in the out-of-plane (z-direction) is in the range of 5 to 30 W/m-K. In one embodiment, TPG has an in-plane thermal conductivity greater than 1,500 W/m-K.
In one embodiment, the heating apparatus 100 is as illustrated in
In one embodiment, the top surface 112 is relatively uniform in temperature, i.e., the difference between a maximum and a minimum temperatures on the top surface is less than 10° C. In a second embodiment, the temperature difference is less than 5° C. In temperature uniformity of the top surface 112 corresponds to a uniform temperature of the substrate W being heated. In one embodiment, the substrate W has a maximum temperature variation of 5° C., and in a second embodiment a maximum temperature variation of 2° C.
In the heater apparatus, one or more electrodes can be employed. Depending on the application, the electrode may function as a resistive heating element, a plasma-generating electrode, an electrostatic chuck electrode, or an electron-beam electrode. The electrode can be embedded within the substrate of the heater toward the top (near the wafer substrate) or the bottom (away from the wafer substrate). A bottom location may help diffuse the pattern of the electrode and assist in the heat distribution to the wafer substrate.
In one embodiment, the electrode is in the form of a film electrode and formed by processes known in the art including screen-printing, spin coating, plasma spray, spray pyrolysis, reactive spray deposition, sol-gel, combustion torch, electric arc, ion plating, ion implantation, sputtering deposition, laser ablation, evaporation, electroplating, and laser surface alloying. In one embodiment, the film electrode comprises a metal having a high melting point, e.g., tungsten, molybdenum, rhenium and platinum or alloys thereof. In another embodiment, the film electrode comprises at least one of carbides or oxides of hafnium, zirconium, cerium, and mixtures thereof.
In another embodiment, the electrode layer is in the form an elongated continuous strip of pyrolytic graphite. Pyrolytic graphite (“PG”) is first deposited onto a heater base, e.g., pyrolytic boron nitride coated graphite base, via processes known in the art such as chemical vapor deposition. The PG is then machined into a pre-determined pattern, e.g., a spiral, a serpentine, etc. The forming of the electrical pattern of the heating zones, i.e., an electrically isolated, resistive heater path, may be done by techniques known in the art, including but not limited to micro machining, micro-brading, laser cutting, chemical etching, or e-beam etching.
Referring back to
The thermal leveler is releasably detachable from the apparatus. The thermal leveler may be associated with or secured in the apparatus by any suitable fastener or fastening mechanism. This may include, but is not limited to, clamps, bolts, threads, cam locks, retaining grooves, retaining rings, a spring, a vacuum, electrostatic forces, electromagnetic forces, magnetic forces, an adhesive, a solder, a paste, etc. In the case of adhesive type fasteners (e.g., adhesives, solder, pastes, etc.), the adhesive fastener should be such that the adhesive fastener can be “reflowed” to a sufficient extent to allow for the leveler to be detached from the cover plate and/or the base plate.
It will be appreciated that this configuration could be reversed as shown in
The cover plate, thermal leveler, and/or base plate can be configured with additional features that can serve to provide additional support, centering, or locking capabilities. For example, a surface of the thermal leveler can be provided with a slot that can receive a protrusion defined in surface of the cover plate and or the base plate. Referring to
The thermal leveler comprises thermal pyrolytic graphite. The configuration of the thermal leveler is not particularly limited and can be selected as desired for a particular application or end use. In particular, the configuration of the thermal leveler will be chosen to provide a desired thermal profile. The TPG layer may be embedded in the heater of the invention as a single layer by itself, or in one embodiment for a heater with a metal substrate, the TPG layer can be in an encapsulated form, e.g., a TPG core encapsulated within a structural metallic shell. Encapsulated TPG is commercially available from Momentive Performance Materials Inc. as TC1050® encapsulated TPG. TPG can be incorporated into the heater as a contiguous single sheet, or, in one embodiment, a plurality of smaller TPG pieces in an overlapping/mosaic configuration.
The orientation and number of TPG sheets in the thermal leveler is not particularly limited. The number, orientation, and position of the sheets can be selected as desired to provide a particular thermal profile. As shown in
The thermal leveler can also be provided with grooves. The grooves may be provided to receive a gas, o-ring, fluid, heater attachment, cooler attachment, etc.
The TPG in the thermal leveler is not particularly limited. TPG may be may be used interchangeably with “highly oriented pyrolytic graphite” (“HOPG”), or compression annealed pyrolytic graphite (“CAPG”). TPG is extremely thermally conductive with an in-plane (a-b direction) thermal conductivity greater than 1000 W/m-K, while the thermal conductivity in the out-of-plane (z-direction) is in the range of 5 to 30 W/m-K. In one embodiment, TPG has an in-plane thermal conductivity greater than 1,500 W/m-K. In one embodiment, the TPG layer has a thickness ranging from about 0.5 mm to 15 mm with thickness variation (parallelism) within 0.005 mm. In another embodiment, the TPG layer has a thickness in the range of 1 mm to 10 mm. In a third embodiment, the TPG layer has a thickness in the range of 2 to 8 mm.
In one embodiment, the TPG is held in place and embedded within the thermal leveler simply by the adhesion of the underlying substrate and/or overcoat where they make contact. In another embodiment, the TPG (in a pure TPG sheet form, or as an encapsulated TPG core in a metal casing, as pure thermal pyrolytic graphite in small piece sizes such as rectangular, square pieces; in random sizes; or in “strips”) is glued in place using a high-temperature adhesive known in the art.
The outer layers or encapsulating layer of a thermal leveler can be selected as desired to contribute to the desired thermal profile of the leveler. The outer layers or encapsulating layer of the thermal leveler can be, for example a metal or ceramic material. Examples of suitable materials for coating, covering, and/or encasing the TPG include, but are not limited to, aluminum, copper, silver, gold, nickel, beryllium, tin, lead and steel or an alloy thereof or a composite such as Kovar, copper-tungsten, copper-molybdenum, Invar, Inconel, Hastelloy, aluminum-beryllium and tin-lead, an oxide, nitride, carbide, carbonitride or oxynitride of elements selected from a group consisting of B, Al, Si, Ga, Y, refractory hard metals, transition metals; oxide, oxynitride of aluminum.
The cover plate and/or the base plate can be formed from any suitable material as desired for a particular purpose or intended application. The cover and/or base plate may form part of a heater configuration. The cover and/or base plate may be formed from a metal or a ceramic material. Examples of suitable metals include, but are not limited to, high temperature materials such as, copper or aluminum alloy. Examples of suitable ceramic materials include, but are not limited to, an oxide, nitride, carbide, carbonitride or oxynitride of elements selected from a group consisting of B, Al, Si, Ga, Y, refractory hard metals, transition metals; oxide, oxynitride of aluminum; and combinations thereof.
The base plate or the cover plate can optionally include features to contribute to controlling the temperature of the apparatus. The base plate or the cover plate can include, for example, heater tubes, cooling tubes, or a combination thereof.
Assembly of the apparatus may be accomplished by providing the respective components (e.g., the cover plate, thermal leveler, and optionally the base plate) configured to be secured to one another by a particular fastener or fastening mechanism, attaching the fastener and securing the components together. The apparatus is similarly dismantled by disconnecting the fastener or fastening mechanism. The thermal leveler can be removed from the system and used in a subsequent process or a different thermal leveler can be inserted into the apparatus. If necessary due to decomposition of a part (e.g., wear/decomposition of the cover plate due to exposure to processing conditions), the respective components can be replaced as necessary. Thus, in an embodiment, it may be necessary to replace the cover plate to use in a processing operation.
The apparatus can include other features as desired for a particular purpose or application. In one embodiment, the apparatus includes lifter pins disposed through the base plate and/or the thermal leveler. The cover plate may include recesses to receive the lifter pins pushed through the base plate and/or thermal leveler. The pins engage the cover plate through the recesses and push or separate the cover plate from the apparatus when a force is applied thereto.
What has been described above includes examples of the present specification. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present specification, but one of ordinary skill in the art may recognize that many further combinations and permutations of the present specification are possible. Accordingly, the present specification is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent that the term “includes” is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term “comprising” as “comprising” is interpreted when employed as a transitional word in a claim.
The foregoing description identifies various, non-limiting embodiments of a thermal management assembly. Modifications may occur to those skilled in the art and to those who may make and use the invention. The disclosed embodiments are merely for illustrative purposes and not intended to limit the scope of the invention or the subject matter set forth in the claims.
The present application claims priority to and the benefit of U.S. Provisional Patent Application No. 62/713,169 titled “Detachable Thermal Leveler” filed on Aug. 1, 2018, the disclosure of which is incorporated herein by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2019/043579 | 7/26/2019 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62713169 | Aug 2018 | US |
