Patent Publication Number: US-2022223453-A1

Title: Electrostatic chuck

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of and priority to U.S. Provisional Patent Application Ser. No. 63/136,086 filed Jan. 11, 2021, the disclosure of which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF INVENTION 
     The present disclosure generally relates to substrate supports. More particularly, the disclosure relates to electrostatic chucks suitable for supporting substrates and to methods of forming the chucks. 
     BACKGROUND OF THE DISCLOSURE 
     Electrostatic chucks can be used for a variety of applications during the formation of devices. For example, an electrostatic chuck can be used to retain a substrate, such as a wafer, during lithography, such as extreme ultraviolet lithography (EUVL); plasma-based and/or vacuum-based processing, such as dry etching, plasma enhanced chemical vapor deposition (PECVD), thermal chemical vapor deposition, physical vapor deposition (PVD), ion implantation, and the like. Temperatures during such processes can be relatively high (e.g., about 800° C.) and/or temperature cycling during such processes can be relatively high (e.g., about 800° C.). 
     A typical electrostatic chuck can include a ceramic body, one or more electrodes (e.g., an electrostatic and an RF electrode) embedded in the body, and a heating element or a plurality of heating elements embedded within the body. The ceramic body, heating element(s), and electrodes can be formed of different materials, which have different coefficients of thermal expansion. 
     During substrate processing, the high temperatures and/or the temperature variation of the chuck, in combination with the differences in the coefficients of thermal expansion, can cause mechanical fatigue in materials, such as the body, electrodes, or the wire. The mechanical fatigue, in turn, can result in cracks within the body, heating element(s), and/or electrode(s), shortening a lifespan of the electrostatic chuck. Accordingly, improved chucks and methods of forming the chucks are desired. 
     Any discussion, including discussion of problems and solutions, set forth in this section has been included in this disclosure solely for the purpose of providing a context for the present disclosure. Such discussion should not be taken as an admission that any or all of the information was known at the time the invention was made or otherwise constitutes prior art. 
     SUMMARY OF THE DISCLOSURE 
     Various embodiments of the present disclosure relate to electrostatic chucks and to methods of forming electrostatic chucks. While the ways in which various embodiments of the present disclosure address drawbacks of prior chucks and methods are discussed in more detail below, in general, exemplary chucks include an interface layer to mitigate damage, such as cracks, to the chuck that might otherwise occur during temperature cycling of the chucks. Methods of forming improved chucks are also described. Additionally or alternatively, the interface layer can reduce volumetric expansion with temperature (e.g., in the range of about 1 to about 800° C.) of the ceramic body, compared to volumetric expansion of an electrostatic chuck that does not include the interface layer. 
     In accordance with examples of the disclosure, an electrostatic chuck is provided. The electrostatic chuck includes a ceramic body, a heating element and/or one or more electrodes (e.g., a first and a second electrode, such as an electrostatic electrode and an RF electrode) embedded within the ceramic body, optionally a dielectric layer, and an interface layer formed overlying the heating element and/or the one or more electrodes, and/or between the ceramic body and the dielectric layer, wherein the interface layer can form a solid solution with the ceramic body. The electrostatic chuck can also suitably include fluid channels to allow a fluid to be circulated through portions of the ceramic body and/or fluid reservoirs or channels. The dielectric layer can be between the heating element and one or more electrodes. The ceramic body can include one or more of aluminum nitride, boron nitride, silicon carbide, and silicon nitrate. In some cases, the ceramic body can include up to about 1-100 ppm or about to 1-30 weight percent of an additive, such as an additive selected from the group consisting of one or more of Al 2 MgO 4 , Al 2 O 3 , Y 2 O 3 , MgO, CaF 2 , and LiF. The heating element can be or include molybdenum or alloys thereof comprising from about 1 at % to about 50 at % or tungsten and/or silicon. The one or more electrodes can be formed of, for example, molybdenum, which, in some cases, may be coated with, for example, gold and/or platinum. The interface layer (e.g., formed over a heating element and/or over an electrode and/or between a dielectric layer and the ceramic body) can include, for example, a (e.g., ceramic) compound that comprises a metal selected from the group consisting of Mg, Ca, Mn, Al, Ba, Be, Zr, Co, Zn, and Cr and one or more of oxygen, nitrogen, carbon, and phosphorous. The interface layer can additionally include an additive selected from the group consisting of one or more of CaO, MnO, MgO, AlON, BaO, BeO, ZrO 2 , CoO, ZnO, Cr 2 O 3 , and Al 2 O 3 . 
     In accordance with additional embodiments of the disclosure, a method of forming an electrostatic chuck is provided. An exemplary method includes providing ceramic precursor material within a mold, providing a heating element and/or one or more electrodes, coating the heating element and/or one or more electrodes with an interface material to form a coated heating element and/or coated electrode(s), placing the coated heating element and or electrode(s) on or within the ceramic precursor material, and sintering the ceramic precursor material to form the electrostatic chuck. In addition or as an alternative to coating a heating element and/or electrodes(s), a dielectric layer can be provided and coated with the interface material. In accordance with examples of these embodiments, the interface material forms an interface layer between one or more of the heating element, electrodes(s), and dielectric layer and ceramic material formed during the step of sintering. The step of providing a ceramic precursor material can include providing one or more of aluminum nitride, boron nitride, silicon carbide, and silicon nitrate powder. Exemplary methods can further include a step of providing one or more additives to the mold prior to the step of sintering. The one or more additives can be selected from the group consisting of Al 2 MgO 4 , Al 2 O 3 , Y 2 O 3 , MgO, CaF 2 , LiF, and the like. The step of sintering can include a typical sintering with applied uniaxial pressure or spark plasma sintering. The step of coating can include, for example, one or more of physical vapor deposition; electrochemical deposition; applying the interface material or interface metal on a surface of the heating element and/or electrode(s) during an extrusion process; deposition of a metal and subsequent oxidation, nitridation, and/or phosphating in a furnace; a gas-phase deposition process, such as chemical vapor deposition and/or atomic layer deposition. By way of particular example, the heating element and/or electrode can include molybdenum and tungsten and the interface material can include a metal selected from the group consisting of Mg, Ca, Mn, Al, Ba, Be, Zr, Co, Zn, Cr and one or more of oxygen, nitrogen, fluoride and phosphate. 
     These and other embodiments will become readily apparent to those skilled in the art from the following detailed description of certain embodiments having reference to the attached figures; the invention not being limited to any particular embodiment(s) disclosed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       A more complete understanding of exemplary embodiments of the present disclosure can be derived by referring to the detailed description and claims when considered in connection with the following illustrative figures. 
         FIG. 1  illustrates a system including an electrostatic chuck in accordance with examples of the disclosure. 
         FIG. 2  illustrates a portion of a system and an electrostatic chuck in greater detail and in accordance with at least one embodiment of the disclosure. 
         FIG. 3  illustrates a method in accordance with at least one embodiment of the disclosure. 
     
    
    
     It will be appreciated that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of illustrated embodiments of the present disclosure. 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Although certain embodiments and examples are disclosed below, it will be understood by those in the art that the invention extends beyond the specifically disclosed embodiments and/or uses of the invention and obvious modifications and equivalents thereof. Thus, it is intended that the scope of the invention disclosed should not be limited by the particular disclosed embodiments described below. 
     The present disclosure generally relates to electrostatic chucks and to methods of forming electrostatic chucks. The chucks and methods as described herein can be used to process substrates to form, for example, electronic devices. By way of examples, the chucks can be used in wafer processes, such as lithography, e.g., as extreme ultraviolet lithography (EUVL); plasma-based and/or vacuum-based processing, such as dry etching, plasma-enhanced etching, plasma enhanced chemical vapor deposition (PECVD), thermal chemical vapor deposition, physical vapor deposition (PVD), ion implantation, and the like, used to form electronic devices. 
     In this disclosure, “gas” may include material that is a gas at normal temperature and pressure, a vaporized solid and/or a vaporized liquid, and may be constituted by a single gas or a mixture of gases, depending on the context. 
     As used herein, the term “substrate” may refer to any underlying material or materials that may be used to form, or upon which, a device, a circuit, or a film may be formed. A substrate can include a bulk material, such as silicon (e.g., single-crystal silicon), other Group IV materials, such as germanium, or compound semiconductor materials, such as Group III-V or Group II-VI semiconductors, and can include one or more layers overlying or underlying the bulk material. Further, the substrate can include various topologies, such as recesses, lines, and the like formed within or on at least a portion of a layer of the substrate. 
     In some embodiments, “film” or “coating” refers to a layer (e.g., continuously) extending in a direction perpendicular to a thickness direction. A coating or layer may be constituted by a discrete single film or layer having certain characteristics or multiple films or layers, and a boundary between adjacent films or layers may or may not be clear and may or may not be established based on physical, chemical, and/or any other characteristics, formation processes or sequence, and/or functions or purposes of the adjacent films or layers. 
     Further, in this disclosure, any two numbers of a variable can constitute a workable range of the variable as the workable range can be determined based on routine work, and any ranges indicated may include or exclude the endpoints. Additionally, any values of variables indicated (regardless of whether they are indicated with “about” or not) may refer to precise values or approximate values and include equivalents, and may refer to average, median, representative, majority, etc. in some embodiments. Further, in this disclosure, the terms “including,” “constituted by” and “having” can refer independently to “typically or broadly comprising,” “comprising,” “consisting essentially of,” or “consisting of” in some embodiments. In this disclosure, any defined meanings do not necessarily exclude ordinary and customary meanings in some embodiments. 
     Turning now to the figures,  FIG. 1  illustrates an exemplary reactor system  100 . Reactor system  100  can be used for a variety of applications, such as, for example, chemical vapor deposition (CVD), plasma-enhanced CVD (PECVD), atomic layer deposition (ALD), clean processes, etch processes, and the like. Other systems may be used for lithography or ion implantation. Although exemplary embodiments are described below in connection with gas-phase reactor systems, embodiments and the disclosure are not so limited, unless stated otherwise. 
     In the illustrated example, reactor system  100  includes an optional substrate handling system  102 , a reaction chamber  104 , a gas injection system  106 , and optionally a wall  108  disposed between reaction chamber  104  and substrate handling system  102 . System  100  also includes an electrostatic chuck  116  to support one or more substrates or wafers  120 . Electrostatic chuck  116  can include one or more embedded devices  118 , such as one or more heating elements and/or one or more electrodes and an interface layer  122  formed over one or more devices  118 . System  100  can also suitably include a first gas source  112 , a second gas source  114 , and an exhaust source  110 . Although illustrated with two gas sources  112 ,  114 , reactor system  100  can include any suitable number of gas sources. Further, reactor system  100  can include any suitable number of reaction chambers  104 , which can each be coupled to a gas injection system  106 . In the case in which reactor system  100  includes multiple reaction chambers, each gas injection system can be coupled to the same gas sources  112 ,  114  or to different gas sources. 
       FIG. 2  illustrates an electrostatic chuck  200 , suitable for use as electrostatic chuck  116 . Electrostatic chuck  200  includes a ceramic body  202 , one or more heating elements  204  embedded within ceramic body  202 , one or more electrodes  206 ,  208 , a dielectric layer  210 , and a fluid cavity  212 . As illustrated, one or more gas supplies  214 , power supplies  216 ,  220 , and fluids  218  can be supplied to electrostatic chuck  200  through a ceramic shaft  222 . As discussed in more detail below, electrostatic chuck  200  also includes one or more interface layers  226 - 232  that can mitigate mechanical fatigue and/or defects within electrostatic chuck  200  that might otherwise arise—e.g., from use of electrostatic chuck  200  during processing. 
     Ceramic body  202  can be formed of ceramic material. By way of examples, ceramic body  202  can include one or more of aluminum nitride, boron nitride, silicon carbide, and silicon nitrate. Ceramic body  202  can additionally include an additive selected from, for example, the group consisting of one or more of Al 2 MgO 4 , Al 2 O 3 , Y 2 O 3 , MgO, Ca F 2 , and LiF. 
     Heating element(s)  204  can be formed of a resistive heating material. By way of examples, one or more heating elements can be formed of one or more of molybdenum, tungsten, a molybdenum alloy, and a tungsten alloy, such as one or more of Mo, W, Mo x W y , MoSi x , and/or WSi x , where x and y are greater than 0 and less than 1 or between about 0.1 and about 0.5. In some cases, an alloy can include Mo and/or W and up to 50 at % of another element, such as silicon, or the other of Mo and W. Heating element  204  can be in the form of a wire or the like. 
     Electrodes  206 ,  208  can be formed of a suitable conducting material. For example, electrodes  206 ,  208  can be formed of a metal, such as molybdenum, or an alloy, such as the molybdenum alloys described above. The metal or alloy can be coated with a layer  207 . Layer  207  can be formed of, for example, gold or platinum. As illustrated, a cooling fluid  224  can be provided within one or more electrodes  206 ,  208  to facilitate temperature regulation of electrodes  206 ,  208  and of electrostatic chuck  200 . 
     Dielectric layer  210  can be formed of a suitable dielectric material, such as a ceramic material. The ceramic material used to form dielectric layer  210  can include a dielectric material that has a higher dielectric resistivity, compared to a dielectric resistivity of ceramic body  202  material. By way of examples, dielectric layer  210  can be or include AlN, Si 3 N 4 , SiC, BN, optionally with one or more additive selected from the group consisting of CaO, MnO, MgO, AlON, BaO, BeO, ZrO 2 , CoO, ZnO, Cr 2 O 3 , and Al 2 O 3 ; the dielectric layer can form during the sintering process. 
     Fluid cavity  212  can be formed during a mold and sintering process and can include a void or porous region formed within ceramic body  202 . A gas, such as Ar, N 2 , or CO, can be present within fluid cavity  212 . 
     As noted above, electrostatic chuck  200  can include one or more interface layers  226 - 232 . In accordance with examples of the disclosure, one or more of interface layers  226 - 232  form a solid solution with the ceramic body  202 . 
     In the illustrated example, interface layer  226  can be formed overlying one or more (e.g., all) heating elements  204 . Interface layer  226  can include a ceramic compound that comprises a metal selected from the group consisting of Mg, Ca, Mn, Al, Ba, Be, Zr, Co, Zn, Cr and one or more of oxygen, nitrogen, carbon, and phosphorous. By way of particular example, the interface layer can be or include MgO, alone or with an additive. Exemplary additives include one or more of CaO, MnO, MgO, AlON, BaO, BeO, ZrO 2 , CoO, ZnO, Cr 2 O 3 , and Al 2 O 3 , and the like. 
     Advantageously, interface layers including (e.g., consisting of or consisting essentially of) MgO may exhibit about reduction of about 30% in volumetric expansion in relation interface layers formed from other ceramic materials, such as AlN. As will be appreciated by those of skill in the art in view of the present disclosure, reducing volumetric expansion of the interface layer reduces the likelihood of crack development at a given temperature. As will also be appreciated by those of skill in the art in view of the present disclosure, reducing volumetric expansion of the interface layer also increases temperature of processes in which the heaters having the interface layer may be employed. 
     Interface layers  228 ,  230  can be formed about electrodes  206 ,  208 . Interface layers  228 ,  230  can be formed of any of the materials described above in connection with interface layer  226 . Similarly, interface layer  232  can be formed about dielectric layer  210 . Interface layer  232  can be formed of any of the materials described above in connection with interface layer  226 . A thickness of any of interface layers  226 - 232  can range from about 1-10 nm to about 1-50 μm or about 1 mm to about 5 mm. 
     Turning now to  FIG. 3 , a method  300  of forming an electrostatic chuck in accordance with embodiments of the disclosure is illustrated. Method  300  includes the steps of providing ceramic precursor ( 302 ), providing a device ( 304 ), coating the device with an interface material to form a coated device ( 306 ), placing the coated device on or within the ceramic precursor material ( 308 ); and sintering the ceramic precursor material to form the electrostatic chuck ( 310 ). The interface material can form an interface layer, such as an interface layer  226 ,  228 ,  230 , and/or  232 , between the device and ceramic material formed during the step of sintering. 
     Step  302  can include providing one or more precursors, such as one or more of aluminum nitride, boron nitride, silicon carbide, and silicon nitrate powder. In some cases, step  302  can additionally include providing one or more additives, such as one or more of Al 2 MgO 4 , Al 2 O 3 , Y 2 O 3 , MgO, CaF 2 , and LiF to the mold. 
     Step  304  can include providing a device. Exemplary devices include heating elements, such as heating elements  204 , electrodes, such as electrodes  206 ,  208 , and a dielectric layer, such as dielectric layer  210 . 
     One or more of the devices provided during step  304  can be coated with an interface material to form a coated device during step  306 . The one or more of the devices can be coated with any of the interface layers noted above in connection with interface layers  226 - 232 . 
     Coating during step  306  can be performed using a variety of techniques. For example, step  306  can include physical vapor deposition of material; electrochemical deposition of material; applying material on a surface of the device during an extrusion process; use of a gas-phase deposition process, such as chemical vapor deposition or a cyclical deposition process, such as atomic layer deposition. The material that is deposited can include the interface material or a metal that is subjected to an oxidation, nitridation, and/or phosphating atmosphere in a furnace. An interface layer that forms from the interface material can include a metal selected from the group consisting of Mg, Ca, Mn, Al, Ba, Be, Zr, Co, Zn, Cr and one or more of oxygen, nitrogen, fluoride and phosphate. 
     Once the device is coated, the coated device can be placed within a mold that includes the ceramic precursor material during step  308 . By way of examples, coated electrode(s), coated heating element(s), and/or coated dielectric layer(s) can be placed in the mold during step  308 . 
     During step  310 , a ceramic body is formed by sintering. The sintering can occur at a temperature of about 1300° C. to about 1900° C., a pressure of about 1 PSI to about 500 PSI, and a time of about 15 min to about several days. The interface layer(s) can form during step  310 . The interface layer(s) can be a ceramic. In some cases, a spark sintering process can be used during step  310 . 
     The example embodiments of the disclosure described above do not limit the scope of the invention, since these embodiments are merely examples of the embodiments of the invention. Any equivalent embodiments are intended to be within the scope of this invention. Indeed, various modifications of the disclosure, in addition to those shown and described herein, such as alternative useful combinations of the elements (e.g., steps) described, may become apparent to those skilled in the art from the description. Such modifications and embodiments are also intended to fall within the scope of the appended claims.