High temperature aluminum nitride heater with multi-zone capability

Abstract

This invention discloses an embodiment of an electric heater device. In one embodiment, an electric heater device includes: (a) a first thermally conductive layer comprising an electrically insulating material; (b) one or more conductive heating elements, which, or the like, are disposed in one or more trenches disposed on the top side of the first thermally conductive layer; and (c) a second thermally conductive layer disposed above the one or more heating elements on the top side of the first thermally conductive layer. The one or more heating elements comprise one or more refractory hard metals doped with at least one of carbon, nitrogen, aluminum, yttrium, or oxygen. Compared to undoped refractory hard metals, the doped one or more refractory hard metals contain a temperature-insensitive resistance within an operating temperature range from ambient temperature to about 850˚C. The one or more heating elements can be independently controlled to provide one or more heating zones.

Description

Technical Field

[0001] The present invention relates to electric heaters, and more particularly, the present invention relates to heaters used in the manufacture of semiconductor wafers such as silicon wafers, gallium arsenide wafers, and the like. Prior Art

[0002] Electric heaters used in semiconductor wafer manufacturing may be used in various steps in the manufacturing / processing of wafers, including material deposition (e.g., physical or chemical vapor deposition), material removal (e.g., etching or planarization), patterning (e.g., lithography), and modification of electrical properties (e.g., doping and annealing). Such electric heaters must be able to withstand highly corrosive environments, resist thermal shock under rapid temperature changes, and be able to withstand extremely high temperatures for long periods of time. However, prior to the present invention, known electric heaters used in semiconductor wafer manufacturing: (1) are susceptible to relatively high variations in resistivity at high temperatures, which drives the need for complex and expensive temperature control, (2) are not easily capable of multi-zone heating, (3) have components that are susceptible to cracking or failure due to thermal stress and thermal cycling and therefore lack durability and longevity, and (4) have components that cannot be co-fired together due to having different thermal expansion coefficients, which results in additional manufacturing steps for their assembly.

[0003] Therefore, a device is needed to solve these and other problems. Summary of the invention

[0004] In one embodiment of the present invention, an electric heater device comprises one or more heat-conducting layers and one or more heating elements embedded in or between the one or more heat-conducting layers, the one or more heating elements comprising molybdenum (Mo), tungsten (W) or any other refractory hard metal doped with at least one or more of carbon (C), nitrogen (N), aluminum (Al) or oxygen (O). In one embodiment, the heating element of the electric heater device comprises molybdenum and molybdenum carbide (Mo2C), such that the carbide content is greater than 5%.

[0005] The heating element of an electric heater device according to the present invention exhibits, among other advantages, an improved stability of resistivity at high temperatures, particularly in the range of about 300°C to about 850°C, but also across the range from about ambient temperature to about 850°C.

[0006] In another embodiment, an electric heater device for processing a semiconductor wafer in a wafer processing chamber is disclosed, comprising: (a) a first thermally conductive layer comprising an electrically insulating material, a top side and a bottom side; (b) one or more electrically conductive heating elements, or the like, disposed in each of one or more grooves configured on the top side of the first thermally conductive layer, the one or more heating elements comprising one or more refractory hard metals doped with at least one of carbon, nitrogen, aluminum, yttrium or oxygen, the doped one or more refractory hard metals comprising a temperature insensitive resistance within an operating temperature range from ambient temperature to about 850°C compared to undoped refractory hard metals, wherein the one or more heating elements are independently controllable to provide one or more heating zones along the top side of the first thermally conductive layer; and (c) a second thermally conductive layer disposed above the one or more heating elements on the top side of the first thermally conductive layer.

[0007] The first thermally conductive layer may comprise a disk. The first thermally conductive layer may be sintered, and prior to sintering the first thermally conductive layer, the one or more heating elements may initially comprise a powder, a coating, or one of a high load from a pre-cut pattern of a polymer sheet. A concentration of carbon may be allowed to vary from about 0.1 atomic % to about 50 atomic %, a concentration of aluminum may be allowed to vary from about 0.1 atomic % to about 20 atomic %, a concentration of nitrogen may be allowed to vary from about 0 atomic % to about 20 atomic %, a concentration of oxygen may be allowed to vary from about 0 atomic % to about 5 atomic % and a concentration of yttrium may be allowed to vary from about 0 atomic % to about 3 atomic %. The first thermally conductive layer comprises aluminum nitride.

[0008] The electric heater device may include a third thermally conductive layer disposed on the bottom side of the first thermally conductive layer. The third thermally conductive layer may include a hub. The second thermally conductive layer and the third thermally conductive layer may include aluminum nitride. The electric heater device may include a sintered riser attached to the hub. Alternatively, a sintered riser may be bonded to the hub, and the bonded riser may create a helium-tight seal with the hub. The electric heater device may include one or more electrical interconnects disposed in each of one or more channels configured on the bottom side of the first thermally conductive layer. The interconnects may be configured to convey electricity from the hub to the one or more heating elements and from the one or more heating elements to the hub in a circuit. The interconnects may be configured to convey sensor data from the one or more temperature sensors to the hub. The one or more temperature sensors may be disposed in each of one or more channels configured on the bottom side of the first thermally conductive layer and below the third thermally conductive layer. The third thermally conductive layer may be disposed above the one or more temperature sensors.

[0009] The one or more heating elements and the first thermally conductive layer may comprise a functionally similar coefficient of thermal expansion to avoid detrimental cracks or fissures in the electric heater device.

[0010] In another embodiment, an electric heater device for processing a semiconductor wafer in a wafer processing chamber is disclosed, comprising: (a) a sintered disk comprising a thermally conductive and electrically insulating material, a top side and a bottom side; (b) one or more electrically conductive heating elements, which or the like are disposed in each of one or more grooves configured on the top side of the disk, the one or more heating elements comprising one or more refractory hard metals doped with at least one of carbon, nitrogen, aluminum, yttrium or oxygen, the doped one or more refractory hard metals comprising a temperature range from ambient temperature to about 850°C compared to undoped refractory hard metals. (c) a first thermally conductive layer disposed above the one or more heating elements on the top side of the disk; (d) one or more interconnects disposed in respective ones of one or more channels configured on the bottom side of the disk; and (e) a second thermally conductive layer disposed above the one or more interconnects on the bottom side of the disk, the second thermally conductive layer comprising a hub, wherein the one or more electrically conductive heating elements are protected from chemical attack.

[0011] A concentration of carbon may be allowed to vary from about 0.1 atomic % to about 50 atomic %, a concentration of aluminum may be allowed to vary from about 0.1 atomic % to about 20 atomic %, a concentration of nitrogen may be allowed to vary from about 0 atomic % to about 20 atomic %, and a concentration of oxygen may be allowed to vary from about 0 atomic % to about 5 atomic % and a concentration of yttrium may be allowed to vary from about 0 atomic % to about 3 atomic %. The thermally conductive and electrically insulating material may be aluminum nitride. The first thermally conductive layer and the second thermally conductive layer may include aluminum nitride.

[0012] The electrical heater device may include a post attached to the hub. The post may be joined to the hub, and the joined post may create a helium-tight seal with the hub. The interconnects may include one or more electrical interconnects, and the electrical interconnects may be configured to convey electricity from the hub to the one or more heating elements and from the one or more heating elements to the hub in an electrical circuit.

[0013] The electric heater device may include one or more temperature sensors disposed in the one or more channels. The second thermally conductive layer may be disposed above the one or more temperature sensors. The one or more heating elements and the disk may include a function similar thermal expansion coefficient to avoid harmful cracks or fissures in the electric heater device. The one or more heating elements may be independently controlled to provide one or more heating zones along the top side of the disk.

[0014] In another embodiment, a method of making an electric heater device for processing a semiconductor wafer in a wafer processing chamber is disclosed, comprising: (a) preparing a disk, a top side and a bottom side, the disk comprising aluminum nitride, the aluminum nitride comprising a sintering aid, the sintering aid comprising from about 3 weight % to about 5 weight % yttrium oxide; (b) making one or more grooves on the top side of the disk; (c) depositing one or more conductive heating elements in each of the one or more grooves disposed on the top side of the disk; and (d) depositing one or more conductive heating elements in each of the one or more grooves disposed on the top side of the disk. wherein the one or more heating elements comprise one or more refractory hard metals doped with at least one of carbon, nitrogen, aluminum, yttrium or oxygen, the doped one or more refractory hard metals comprising a temperature insensitive resistance within an operating temperature range from ambient temperature to about 850°C compared to the undoped refractory hard metal, wherein the one or more heating elements are independently controllable to provide one or more heating zones along the top side of the disk; (d) depositing a first powder comprising aluminum nitride on the one or more heating elements on the top side of the disk; (e) compressing the disk at least once in a mold to consolidate the first powder; (f) making one or more channels on the bottom side of the disk; (g) depositing one or more conductive interconnects in the one or more channels on the bottom side of the disk; (h) depositing a second powder including aluminum nitride over the one or more interconnects on the bottom side of the disk; (i) compressing the disk at least once in a mold to consolidate the second powder; (j) machining and grinding the pressed disk to include a hub, the pressed and machining a disk to define an aluminum nitride matrix with embedded heating elements and interconnects; (k) sintering the aluminum nitride matrix at a temperature in the range of from about 1600°C to about 1850°C, wherein the sintering step is performed under controlled heating in a nitrogen environment to burn out any temporary binder in the aluminum nitride matrix, wherein the amount of carbon is maintained below the oxygen content of the aluminum nitride in the aluminum nitride matrix that is unassociated with the yttria, such that a composition of a liquid phase of aluminum oxide and yttria is such that the Al2O3 / Y2O3 molar ratio in the sintered aluminum nitride matrix is ​​from 10:3 to 0.1:1, wherein a portion of the amount of carbon is incorporated into the doped one or more refractory hard metals of the one or more electrically conductive heating elements, wherein sintering forms a densified aluminum nitride matrix comprising the densified one or more electrically conductive heating elements within the sintered aluminum nitride matrix; and (l) bonding a sintered post to the hub.

[0015] These and other embodiments are described herein. Simple diagram description

[0016] For a better understanding of one of the features described in the present invention, reference may be made to the embodiments shown in the drawings. The embodiments in the drawings are not necessarily drawn to scale, and related elements may be omitted to emphasize and clearly illustrate the novel features described herein. In addition, the system components may be configured in various ways, as is known in the art. In the drawings, unless otherwise specified, the same reference numeral may refer to the same component in different drawings.

[0017] FIG. 1 is a bottom perspective view of an embodiment of an electric heater of the present invention.

[0018] FIG. 2 is an exploded top perspective view of a portion of the electric heater of FIG. 1 .

[0019] 3 illustrates a top perspective view of the disc assembly of the electric heater of FIG. 1 , with grooves shown in the top side of the disc of the disc assembly.

[0020] 4 is an exploded perspective top view of the disk of FIG. 3 and one of the respective inner and outer heating elements.

[0021] 5 shows a top perspective view of the disk of FIG. 4 after installing respective inner and outer heating elements into grooves in the disk.

[0022] 6 illustrates a top perspective view of one of the disks of FIG. 5 after a thermally conductive powder has been deposited on the top side of the disk.

[0023] 7 illustrates a top perspective view of one of the disks of FIG. 6 after compacting thermally conductive powder onto the disk of FIG. 6 .

[0024] 8 illustrates a bottom perspective view of the disk of FIG. 7 , with the grooves shown in the bottom side of the disk.

[0025] 9 is an exploded bottom perspective view of the disk of FIG. 8 along with the interconnect and thermocouple(s).

[0026] 10 shows a bottom perspective view of the disk of FIG. 9 after installation of the interconnect and thermocouple(s).

[0027] 11 illustrates a bottom perspective view of one of the disks of FIGS. 8-10 after thermally conductive powder has been deposited on the bottom side of the disk.

[0028] FIG12 shows an exploded bottom perspective view of one of the disks of FIGS. 8-11 after compacting the thermally conductive powder onto the bottom side of the disk, after machining, and after sintering to form a completed disk assembly. Also shown are the respective thermocouple sockets and heating element sockets, which may be installed before or after sintering the disk.

[0029] FIG. 13 is a top plan view of the disc assembly of FIG. 12 .

[0030] 14 is a cross-sectional view of the disc assembly of FIG. 13 taken along line 14-14.

[0031] FIG. 15 is a bottom perspective view of the disc assembly of FIG. 13 .

[0032] FIG. 16 is an exploded perspective view of the disc assembly and one of the vertical columns of FIG. 15 as seen from below.

[0033] 17 and 18 are respective top and bottom perspective views of the disc assembly of FIG. 15 shown in an installed position to form an electric heater device with an engaged vertical post.

[0034] FIG. 19 is a transparent top plan view of an embodiment of the electric heater device of FIG. 18 .

[0035] Figures 20 and 21 are cross-sectional views of the electric heater device of Figure 19 taken along lines 20-20 and 21-21, respectively.

[0036] FIG. 22 is a schematic diagram showing a flow chart of a method for manufacturing an embodiment of an electric heater of the present invention.

[0037] FIG. 23 is a cross-sectional view of another embodiment of an electric heater device according to the present invention.

[0038] FIG. 24 is a representative graph showing the resistivity of pure tungsten and pure molybdenum as a function of temperature.

[0039] 25 is a SEM / EDS spectral analysis and FIG. 26 is a representative elemental concentration taken from spectrum 8 of FIG. 25 in a cross section of a heating element within a cross section of an aluminum nitride substrate in a sample disk assembly configured as disclosed herein.

[0040] FIG. 27 is a graph of power versus temperature based on a thermal simulation.

[0041] FIG. 28 shows resistance data captured from a representative heating element of the present invention. Implementation

[0042] Cross Reference This application claims the benefit of U.S. Provisional Patent Application No. 62 / 843,241, filed May 3, 2019, the entire contents of which are incorporated herein by reference.

[0043] Although the features, methods, devices, and systems described herein may be embodied in various forms, some exemplary and non-limiting embodiments are shown in the drawings and described below. However, not all of the depicted components described in the present invention are required, and some embodiments may include additional, different, or fewer components than those explicitly described in the present invention. Changes in the configuration and type of components may be made without departing from the spirit or scope of the invention claims as described herein. Therefore, it should be understood that any of the features of one embodiment discussed with reference to the figures herein may be combined with or substituted for features discussed in conjunction with other embodiments of the present invention.

[0044] The present invention describes various aspects of at least one embodiment of an electric heater device for use in fabricating semiconductor wafers. Various embodiments of an electric heater device provide a variety of advantages. For example, the electric heater device of the present invention provides a resistive heater having a relatively low resistance change (i.e., the resistance is relatively insensitive to temperature changes) during operation within a range from about ambient temperature to about 850°C, and particularly within a range from about 300°C to about 850°C, compared to its metallic counterparts within the same test temperature. Other advantages include: a. The composition of the heating element and its porosity allow for shrinkage that is compatible with the shrinkage of the aluminum nitride. Because there is no excessive mismatch in shrinkage, the resulting heating element including one or more heating elements embedded in an aluminum nitride matrix does not develop detrimental internal cracks or fissures. b. After sintering of the aluminum nitride, the heating element composition has a thermal expansion coefficient that is reasonably close to that of the aluminum nitride so that there are no cracks that are detrimental to the performance of the heater. c. The embodiments described herein include a multi-layered heating element disk and riser assembly with a strong joint capable of being helium sealed. d. The embodiments described herein provide a scalable design for providing single or multiple heating zones and allow for the design of a variety of multi-zone heater configurations with functional temperature uniformity in the range of about ambient temperature to about 850°C. e. The embodiments described herein allow for additional or multiple thermocouple temperature sensors beyond those of known devices, all of which are able to survive a heater process that includes steps involving compressing the component, embedding the component, and exposing the component to a high sintering temperature ranging from about 1600°C to about 1850°C. f. The embodiments described herein provide a solution capable of delivering the high powers required for high temperature operations due to high radiative heat losses. g. The embodiments described herein include electrical connection systems that connect power and sensor conductors to thermal elements suitable for high temperature applications and that can withstand the heater processes disclosed herein. h. The embodiments described herein allow the ability to incorporate or use a standard temperature control system to operate an electric heater device because the heating element does not have a large resistance change over temperature. Thus, using a heating element with a resistance that is relatively insensitive to temperature over a range of operating temperatures avoids the need for more complex controllers, control considerations, and switching components. i. The embodiments described herein provide a multi-zone electric heater device configured to achieve operating temperatures from ambient temperature to about 850°C. j. The embodiments described herein are etch resistant.

[0045] Turning to the figures, various embodiments of an electric heater device are shown. For example, FIG. 1 shows an embodiment of an electric heater device 100 according to the present invention. The electric heater device 100 includes a vertical post 150 attached thereto. The vertical post 150 is configured for attachment to a feedthrough (not shown) to transition the electric heater device 100 to an atmospheric environment outside the semiconductor wafer processing chamber.

[0046] Referring to FIGS. 2 to 18 , various aspects of the electric heater device 100 are shown. For example, the electric heater device 100 includes a disk assembly 105 and a vertical post 150 attached thereto. The disk assembly 105 includes one or more heating elements 110 and a thermally conductive layer 140 positioned on the top side 115 of the disk 120. The disk assembly 105 includes an interconnect 125, a thermally conductive layer 145, and a socket 135 positioned on the bottom side 116 of the disk 120. The vertical post 150 of the electric heater device 100 is generally tubular and extends vertically from the bottom side 116 of the disk 120 after being joined to the disk assembly 105. One of ordinary skill in the art will appreciate that the top side 115 of the disk 120 is the wafer side, and the bottom side 116 provides a portion of the connection to the outside of the wafer processing chamber.

[0047] The disk 120 may be configured as a disk or a plate and may have a circular, semicircular or any other planar geometry. According to the embodiment shown in the figure, the disk 120 has a circular planar geometry and may be manufactured in any diameter, such as, for example, 150 mm, 200 mm, 300 mm or 450 mm diameter. The disk 120 may be configured to have a thermally conductive and electrically insulating material. In the embodiment shown in the figure, a suitable thermally conductive and electrically insulating material includes aluminum nitride, which includes a sintering aid, which may include yttrium oxide in an amount from about 3% by weight to about 5% by weight. In other embodiments, in addition to or in place of yttrium oxide, the aluminum nitride powder may include a small amount (i.e., less than 5% by weight) of an alkaline earth metal oxide, including calcium oxide. The aluminum nitride and sintering aid (if present) may also be combined with a suitable binder. The aluminum nitride ceramic powder with a binder can be consolidated in a mold under sufficient pressure to form the disk 120. The heat conducting layers 140, 145 of the disk assembly 105 can also be made of aluminum nitride to ensure thermal compatibility with each other.

[0048] The disk 120 is configured to have grooves 155 positioned on the top side 115 of the disk 120 to receive one or more heating elements 110. In this manner, the disk 120 can serve as a substrate for the one or more heating elements 110. As best shown in the embodiments of FIGS. 3, 4, and 19, the grooves 155 include inner grooves 156 and outer grooves 157, each defining a continuous channel without a beginning or end. In other embodiments, one or more of the grooves 155 may have a serpentine or other shape with defined ends. The inner grooves 156 and outer grooves 157 of the grooves 155 are further defined by a plurality of arcuate, spaced-apart channel portions that zigzag across the top side 115 of the disk 120 in a common plane. In other embodiments, the grooves 155 may be configured to receive a single heating element. In other embodiments, the grooves 155 may be configured to receive more than two heating elements.

[0049] Although the spaced channel portions of the outer grooves 157 of the disk 120 are approximately radially equidistant from each other (as shown in FIG. 3 ), at least some of the spaced, zigzag channel portions of the inner grooves 156 are radially closer to each other than other spaced, zigzag channel portions of the inner grooves 156. In this manner, the radial density of the channel portions may be higher or lower in different portions or regions of the top side 115 of the disk 120. In some embodiments, the radial spacing of the arcuate, zigzag channel portions may be relatively constant relative to each other as the channels traverse radially outward from the center of the top side 115 of the disk 120 in an arcuate and zigzag pattern. In other embodiments, the radial spacing of the arcuate, zigzag channel portions may vary. In some embodiments, the circumferential spacing of the channel portions may be relatively constant, variable, or higher or lower in different portions or regions of the top side 115 of the disk 120.

[0050] In other embodiments, the pattern and geometry of the grooves 155 may include any desired pattern, depth, and width. For example, in some embodiments, the grooves 155 may be spirally arranged on the top side 115 of the disk 120. In some embodiments, the internal geometry of the grooves 155 may include a flat bottom wall and have opposing side walls oriented perpendicular to the bottom wall. In other embodiments, the internal geometry of the grooves 155 may include sloped, conical, or rounded side walls and / or bottom walls or any other geometry. In some embodiments, the width of the channel may be optimized across the disk 120 or locally using thermal analysis to achieve an optimal thermal uniformity.

[0051] As shown in the embodiments of FIGS. 4 and 5 , the one or more heating elements 110 include an inner heating element 111 and an outer heating element 112 positioned in or received by a respective inner groove 156 and outer groove 157. In some embodiments, the one or more heating elements 110 may be embedded within or between the thermally conductive layers 140, 145 and / or the disk 120. For example, the groove 155 may alternatively be disposed in the bottom side of the thermally conductive layer 140 to receive the one or more heating elements rather than having the groove 155 formed in the top side 115 of the disk 120. Although a pair of heating elements is shown in the figures, in other embodiments, only one heating element or more than two heating elements may be configured on the top side 115 of the disk 120. The multiple heating elements may be controlled by a controller to provide differential heating or substantially uniform heating across the top side 115 of the disk 120.

[0052] In at least this embodiment, one or more heating elements 110 include doped molybdenum or an equivalent compound containing a carbide or refractory hard metal (such as tungsten or its alloys). Preferred doping of molybdenum involves carbon, aluminum and possibly nitrogen, oxygen and yttrium.

[0053] During the binder burnout while sintering the disk assembly 105, a carbon dopant is produced or otherwise added to the metal powder associated with the electrically conductive one or more heating elements 110. During this process, the portion is heated in an inert or substantially inert atmosphere in the range of about 1600°C to about 1850°C to pyrolyze the binder so that a desired amount of residual carbon is produced. The amount of carbon produced by this process is maintained below the oxygen content of the aluminum nitride unassociated with the yttrium oxide so that the composition of the liquid phase of the aluminum oxide and the yttrium oxide is such that the Al2O3 / Y2O3 molar ratio in the sintered body is between 10:3 and 0.1:1. A portion of this carbon is incorporated into the molybdenum powder that is shrunk and sintered to produce a dense heating element within the aluminum nitride matrix. The remainder of the carbon reacts with the Al2O3 to form aluminum nitride and carbon monoxide. At high temperatures (typically in the range of about 1600°C to about 1850°C), the composition of the one or more heating elements 110 is allowed to approach chemical equilibrium in a nitrogen atmosphere due to the interaction between the aluminum nitride, molybdenum, carbon and the sintering aid of aluminum oxide-yttrium oxide (as described above), resulting in the desired composition of the one or more heating elements 110. Other dopants, such as aluminum, nitrogen, oxygen and yttrium, can be added simply by high temperature interaction between the thermally conductive element components and the surrounding aluminum nitride matrix. The concentrations of carbon, aluminum, nitrogen, oxygen and yttrium can be allowed to vary within the following ranges: Carbon: 0.1 atomic% to 50 atomic% Aluminum: 0.1 atomic% to 20 atomic% Nitrogen: 0 atomic % to 20 atomic % Oxygen: 0 atomic% to 5 atomic% Yttrium: 0 atomic% to 3 atomic%

[0054] It should be noted that SEM / EDS analysis may be insensitive to trace to small amounts of boron. Typically, if the boron concentration becomes greater than ~10%, then the absence of interference from other elements in the spectral analysis can be detected. Since boron may be present due to its use as a boron nitride (or boron nitride and aluminum nitride machinable ceramic combination) to provide inert support during binder burnout and / or sintering, it cannot be excluded from a possible composition. Therefore, in one of the ways described above for dopants such as aluminum, nitrogen, and oxygen, boron may be added during high temperature interactions during sintering, but it may be detected using conventional SEM / EDS analysis. Therefore, as a dopant typically in the range from 0 to the detection limit, which is approximately 10 atomic %, boron cannot be excluded.

[0055] The composition of the one or more heating elements 110 involves non-metallic elements such as carbon, nitrogen and oxygen along with trace amounts of boron and elements found in aluminum nitride ceramics (i.e., aluminum, yttrium), all determined by SEM / EDS analysis. The non-metallic elements can be added by direct addition of precursors such as organic binders that produce residual amounts of carbon during their pyrolysis in the binder burnout step, or by direct addition of particulate carbon, which will simply be incorporated into the heating element forming a solid solution of molybdenum and carbon or molybdenum carbide (Mo2C or MoC). X-ray diffraction analysis shows that the heating element contains a mixture of molybdenum and molybdenum carbide along with trace amounts of unidentified phases due to the insufficient number of peaks. In one case, the ratio of molybdenum to molybdenum carbide (such as Mo2C) is close to 2:1.

[0056] The composition of the one or more heating elements 110 may include trace to small amounts of aluminum, yttrium, and oxygen due to the use of a liquid that forms an oxide sintering phase (A2O3-Y2O3) in part in a nitrogen atmosphere. The presence of trace to small amounts of elements in the heating element / electrode composition must be considered because it is well known that the addition of small amounts of dopants can affect the electrical properties of metals and ceramics (a compound of a metal and a non-metal).

[0057] The described one or more heating elements 110 provide several highly desirable properties, including: (1) an ability to withstand thermal stresses (i.e., a coefficient of thermal expansion sufficiently close to that of the ceramic matrix of the disk assembly 105); (2) chemical compatibility (i.e., inertness) relative to the ceramic matrix; (3) an ability to be co-fired with the ceramic matrix; and (4) of particular note, an improved stability of resistivity as a function of temperature (particularly at high operating temperatures). In fact, the described one or more heating elements 110 are observed to have a relatively low variation in resistivity (i.e., resistance is relatively insensitive to temperature variations) over the desired operating range of about ambient temperature to about 850°C due to a relatively low resistivity coefficient of approximately 0.001 (1 / K) measured from about ambient temperature to about 850°C relative to pure molybdenum having a resistivity coefficient of 0.005 (1 / K) over the same temperature. In one embodiment, as shown in FIG. 28 , within a temperature range from about 300° C. to about 600° C., the resistance is within a range from about 4.18 ohms to about 4.28 ohms.

[0058] FIG. 6 shows the thermally conductive layer 140 initially disposed on the top side 115 of the disk 120 in the form of aluminum nitride powder. The powder is consolidated with a binder under pressure to form a machinable surface. As shown in FIG. 7 , the composite disk 120 / thermally conductive layer 140 is drilled in 3 locations to form holes 122 for indexing and timing of the disk assembly 105. As shown in FIG. 19 , the holes 122 do not interfere with the one or more heating elements 110 or the interconnect 125.

[0059] The disk 120 is configured with grooves 165 positioned on the bottom side 116 of the disk 120 to receive the interconnects 125. As best shown in the embodiment of FIGS. 8-9 , the grooves 165 include heating element interconnect grooves 166, inner thermocouple interconnect grooves 167, and outer thermocouple interconnect grooves 168. For purposes of the present invention, as shown in FIGS. 2 and 9 , the interconnects 125 include heating element interconnects 126, 129, inner heating element thermocouples 127, and outer heating element thermocouples 128. In some embodiments, the interconnects 125 may be embedded within or between the thermally conductive layers 140, 145, and / or the disk 120. For example, instead of having the grooves 165 formed in the bottom side 116 of the disk 120, the grooves 165 may be disposed in the top side of the thermally conductive layer 145 to receive one or more heating elements.

[0060] As shown in FIG. 10 , the heating element interconnects 126, 129 are positioned in or received by respective interconnect grooves 166, the inner heating element thermocouple 127 is positioned in or received by the interconnect groove 167, and the outer heating element thermocouple 128 is positioned in or received by the interconnect groove 168. The grooves 165 are generally arcuate and slightly radially arranged in a common plane. Interconnection vias 170, 171, 172, 173 allow power to be communicated to one or more heating elements 110 and allow sensor signals from the inner thermocouple 127 and the outer thermocouple 128 to pass through the disk 120 to the top side 115 or from the top side 115 through the disk 120 to communicate through conductors (such as any electrodes and thermocouple extension wires located inside the vertical column) and ultimately through a feedthrough (not shown).

[0061] Specifically, the posts 146 of the respective heating element interconnects 126 are inserted into or received by the respective through-holes 170 to communicate power to the outer heating element 112. One post 146 delivers electricity to the outer heating element 112, and the other post 146 returns electricity from an opposite end of the outer heating element 112 to a feed-through (not shown) to complete the circuit.

[0062] One of the heating element interconnects 126 receives electricity at its inner end interface 130 and delivers electricity to its post 146. The other of the heating element interconnects 126 receives electricity from its post 146 and delivers electricity to its inner end interface 130. As shown in Figures 9 and 12, the inner end interface 130 receives electricity delivered to it from a respective one of the sockets 174 inserted into the through-holes 163 located on the inner hub 142 of the disk 120. Of course, electricity can flow in the opposite direction.

[0063] Similarly, posts 147 (not shown) of the heating element interconnect 129 are inserted into or received by through-holes 172 to communicate power to the inner heating element 111. Posts 147 deliver electricity to the inner heating element 111, and terminals 137 return electricity from an opposite end of the inner heating element 111 to a feed-through (not shown) to complete the circuit.

[0064] The heating element interconnect 129 receives electricity at its inner end interface 131 and delivers electricity to its post 147. As shown in Figures 9 and 12, the inner end interface 131 receives electricity delivered thereto from one of the sockets 174 inserted into the through-holes 162 located on the inner hub 142 of the disk 120. The terminal 137 delivers electricity from the opposite end of the inner heating element 111 to one of the sockets 174 inserted into the through-holes 171 located on the inner hub 142 of the disk 120. Of course, electricity can flow in the opposite direction.

[0065] The inner and outer thermocouples 127 , 128 generate a temperature proportional millivolt signal and communicate the signal via terminals 138 connected to respective sockets 175 inserted into respective through holes 164 .

[0066] The composition and method of manufacturing the heating element interconnects 126, 129 and sockets 135 can be similar to the composition and method of the one or more heating elements 110 to include the benefits of low variation in resistance within a range of operating temperatures in these components. As disclosed herein, low variation in resistance (i.e., resistance is relatively insensitive to temperature variations) minimizes thermal contributions to thermal non-uniformity. Therefore, the heating element interconnects 126, 129 and sockets 135 can be doped as described herein for the one or more heating elements 110. In some embodiments, it is also acceptable for the heating element interconnects 126, 129 and sockets 135 to be undoped, but in such cases, the undoped heating element interconnects 126, 129 and sockets 135 must have sufficiently low resistance at any temperature compared to the one or more heating elements 110. This can be achieved by controlling, for example, the geometry of the heating element interconnects 126, 129 and sockets 135 so that the resistance is sufficiently small. In some embodiments, the composition of the heating element interconnects 126, 129 and the socket 135 including one or more refractory hard metals as disclosed herein may not require doping or at least be doped only to the extent required for the resistive portion of the respective components.

[0067] As shown in FIG. 11 , the thermally conductive layer 145 is initially disposed on the bottom side 116 of the disk 120 in the form of aluminum nitride powder. The powder is consolidated under pressure with a binder to form a processable surface. As shown in FIG. 12 , the bottom side 116 has been pressed and processed to form the finished thermally conductive layer 145. The socket 135 includes a heating element socket 175 and a thermocouple socket 176. FIG. 13 to FIG. 15 show the finished disk assembly 105. The bottom side 116 of the disk assembly 105 includes an annular groove 178 formed in an annular protrusion 180 to receive the flange 182 of the vertical column 150. At this point, in order to provide access to a wafer lifting mechanism, the hole 122 can be enlarged to its final diameter. The socket 135 can be inserted into the disk 120 before or after sintering the disk 120 / disk assembly 105.

[0068] FIG. 16 shows the disk assembly 105 before the installation of the vertical column 150, and FIGS. 17-18 show the disk assembly 105 after the installation of the vertical column 150. The vertical column 150 includes a tubular extension 160 having a flange 182 located on one end (top end) and an annular protrusion 183 located on the opposite end (bottom end). The top surface 184 of the flange 182 is configured to mate with the bottom wall 186 of the annular groove 178. Similarly, the outer wall 188 of the flange 182 is configured to mate with the outer wall 190 of the annular groove 178, and the inner wall 192 of the flange 182 is configured to mate with the inner wall 194 of the annular groove 178. The annular protrusion 183 is configured to engage a feed-through (not shown) or other structure to transition to the atmospheric conditions outside the wafer processing chamber.

[0069] The upright 150 may be bonded to the disk assembly 105 using any suitable bonding method to produce a strong joint with the ability to also be a helium-tight seal. For example, diffusion bonding, metallization brazing, mechanical joints with high temperature seals, glass or glass ceramic bonding techniques, or other techniques may be used depending on the process requirements. A suitable bonding method is disclosed in U.S. Patent No. 5,096,863, entitled "Diffusion-Bonded Assembly of AlN Ceramic Bodies and Heat Dissipation Member Constituted Thereby," which is incorporated herein by reference in its entirety. The bonding process taught in this patent produces a helium-tight seal between the upright 150 and the disk assembly 105.

[0070] It should be noted that any geometry or configuration of an electric heater device consistent with the principles disclosed herein is feasible. For example, some end users may desire a configuration that includes a ground plane or an electrostatic chuck electrode embedded within the disk assembly 105. Such additional features may be readily incorporated without departing from the teachings herein. Additionally, different electrical wiring schemes may be deployed to accommodate multiple heating elements and / or heating zones while minimizing the number of through connections. Additionally, the disk assembly 105 may include more than the number of layers described above, with interconnects conveying signals (i.e., power signals, sensor signals, etc.) between components on different layers.

[0071] Turning to FIG. 22 , various steps for making one embodiment of the electric heater device 100 are shown. For example, at step 300 , starting with a “green” disk 120 made of a thermally conductive and electrically insulating material such as aluminum nitride, formed by consolidating powders using a binder under sufficiently high pressure in a mold and having a desired diameter and initial thickness, grooves 155 are created on the top side 115 of the disk 120 to receive one or more heating elements 110, and grooves 165 are created on the bottom side 116 of the disk 120 to receive the interconnects 125. In other embodiments, grooves 165 may be created at a different time than grooves 155. To make grooves 155, 165, a masking film may be applied to the respective top side 115 / bottom side 116 and a laser engraving technique may be deployed. Additionally, similar techniques may be used to make grooves 155, 165 without departing from the teachings of the present invention. For example, the grooves 155, 165 may be formed on the green disc 120 when the disc 120 is initially pressed and formed. Alternatively, the grooves 155, 165 may be machined into the disc 120 after the disc 120 is initially formed.

[0072] Holes 122 may be created at this point to enable / ensure timing / indexing of the disk 120 after the disk surface is covered with aluminum nitride powder. At step 305, one or more heating elements 110 are placed in the grooves 155. To this end, at least one of the following is applied or placed (as applicable) to fill the grooves 155: (1) a highly loaded coating including one or more refractory hard metals (such as molybdenum, tungsten and / or tantalum, etc.), (2) a pre-cut pattern from a polymer sheet including one or more highly loaded refractory metals (such as molybdenum, tungsten and / or tantalum, etc.), or (3) a highly loaded powder of refractory hard metals (such as molybdenum, tungsten and tantalum, etc.), all of the foregoing including a composition / concentration naturally occurring as disclosed herein or as would be understood by one of ordinary skill in the art from the teachings disclosed herein. At step 310, a thermally conductive powder (such as aluminum nitride powder) is applied to the top side 115 of the disk 120. At step 315, the powder is consolidated using a binder under pressure to form a machinable surface. At step 320, the interconnect 125 is installed in the groove 165, and a powder, a coating, or one of a high load from a pre-cut pattern of a polymer sheet as disclosed above is applied or placed to fill the groove 165, each including one or more refractory hard metals (such as molybdenum, tungsten and / or tantalum, etc.) in the composition / concentration disclosed herein. At step 325, a thermally conductive powder (such as aluminum nitride powder) is applied to the bottom side 116 of the disk 120. At step 330, the powder is consolidated using a binder under pressure to form a machinable surface. At step 335, the power supply and thermocouple sockets 135 are installed in respective through holes in the aluminum nitride powder on the bottom side 116 of the disk 120. At step 340, both sides of the disk 120 are machined to near final dimensions to form the disk assembly 105. At step 345, the disc assembly 105 is subjected to binder burnout and sintering in a nitrogen atmosphere under controlled heating to produce a small amount of residual carbon. A portion of this carbon is incorporated into the molybdenum powder that shrinks and sinters to produce a dense one or more heating elements 110 in the aluminum nitride matrix. The remaining portion of the carbon reacts with Al2O3 to form aluminum nitride and carbon monoxide. At high temperatures (typically in the range of from about 1600°C to about 1850°C), due to the interaction between the aluminum nitride, molybdenum, carbon and the sintering aid of aluminum oxide-yttrium oxide, in a nitrogen atmosphere, the composition of the one or more heating elements 110 is allowed to approach chemical equilibrium, resulting in the desired composition of the one or more heating elements 110.

[0073] At step 350, a final machining and / or grinding operation is performed on the disc assembly 105 to achieve the final dimensional form. At step 355, the upright 150 is joined to the disc assembly 105 using any suitable joining method as disclosed herein. At step 360, a feedthrough may be assembled (if made from separate components), and at step 365, the feedthrough may be mounted on the upright 150.

[0074] One of ordinary skill in the art will appreciate that various additive manufacturing methods may be adapted to manufacture the disk assembly 105 and / or the electric heater device 100. As described below for the electric heater device 400, a suitable additive manufacturing process may include a process known as laminated object manufacturing developed by Helysis Inc. for producing 3D objects by stacking sheets of laser cut paper fed by a roll-to-roll process, the entire contents of which are incorporated herein by reference.

[0075] Turning now to FIG. 23 , another embodiment of an electric heater device 400 of the present invention is shown. In this embodiment, a disk assembly 420 includes aluminum nitride layers 401, 402, 403 with embedded heating elements 407, through holes 409 and power distribution layer 402a, shaft 404 and feedthrough 406, metal chamber mounting flange 405, heating element / electrode assemblies 411, 412, 413 and electrode entry point 410.

[0076] A heating element / electrode system, conceptually shown as components 411, 412, 413, is used to provide current to the heating element 407 at the entry point 410. The rigid pin 411 is not limited to a conductive metal such as molybdenum or tungsten because it is not bonded to the entry point 410. In some embodiments, a nickel alloy may also be used. The interface between 410 and 411 creates an electrical contact to feed the current. An upward force is applied by spring 412. A flexible conductor is connected to the external system. It is sealed at the feed-through 406. This connection system can be used for heaters and thermocouple sensors. Only one set of components is shown for simplicity. This connection system allows for thermal extension of components at high temperatures. A metal chamber mounting flange 405, preferably made of aluminum, mounts the base to the chamber wall or lifting platform with sealing components and fasteners.

[0077] In at least this embodiment, the heating element 407 comprises a carbide doped with or containing molybdenum, or an equivalent compound of a refractory hard metal such as tungsten or an alloy thereof. Preferred doping of molybdenum involves carbon, aluminum, and possibly nitrogen, oxygen, and yttrium.

[0078] During the binder burnout while sintering the disk assembly 420, a carbon dopant is produced or otherwise added to the metal powder associated with the conductive heating element 407. During this process, the portion is heated in an inert or substantially inert atmosphere in the range of about 1600°C to about 1850°C to pyrolyze the binder so that a desired amount of residual carbon is produced. The amount of carbon produced by this process is maintained below the oxygen content of the aluminum nitride that is not associated with the yttrium oxide so that the composition of the liquid phase of the aluminum oxide and the yttrium oxide is such that the Al2O3 / Y2O3 molar ratio in the sintered body is between 10:3 and 0.1:1. A portion of this carbon is incorporated into the molybdenum powder that is shrunk and sintered to produce a dense heating element within the aluminum nitride matrix. The remainder of the carbon reacts with the Al2O3 to form aluminum nitride and carbon monoxide. At high temperatures (typically in the range of about 1600°C to about 1850°C), the composition of the heating element 407 is allowed to approach chemical equilibrium in a nitrogen atmosphere due to the interaction between the aluminum nitride, molybdenum, carbon and the sintering aid of aluminum oxide-yttrium oxide (as described above for disk 120). This results in the desired composition of the heating element 407. Other dopants, such as aluminum, nitrogen, oxygen, and yttrium, can be added simply by high temperature interaction between the thermally conductive element components and the surrounding aluminum nitride matrix. The concentrations of carbon, aluminum, nitrogen, oxygen, and yttrium can be allowed to vary within the following ranges: Carbon: 0.1 atomic% to 50 atomic% Aluminum: 0.1 atomic% to 20 atomic% Nitrogen: 0 atomic % to 20 atomic % Oxygen: 0 atomic% to 5 atomic% Yttrium: 0 atomic% to 3 atomic%

[0079] It should be noted that SEM / EDS analysis may be insensitive to trace to small amounts of boron. Typically, if the boron concentration becomes greater than ~10%, then the absence of interference from other elements in the spectral analysis can be detected. Since boron may be present due to its use as a boron nitride (or boron nitride and aluminum nitride machinable ceramic combination) to provide inert support during binder burnout and / or sintering, it cannot be excluded from a possible composition. Therefore, in one of the ways described above for dopants such as aluminum, nitrogen, and oxygen, boron may be added during high temperature interactions during sintering, but it may be detected using conventional SEM / EDS analysis. Therefore, as a dopant typically in the range from 0 to the detection limit, which is approximately 10 atomic %, boron cannot be excluded.

[0080] The composition of the heating element 407 involves non-metallic elements such as carbon, nitrogen and oxygen along with trace amounts of boron and elements found in aluminum nitride ceramics (i.e., aluminum, yttrium), all determined by SEM / EDS analysis. The non-metallic elements can be added by direct addition of precursors such as organic binders that produce residual amounts of carbon during their pyrolysis in the binder burnout step, or by direct addition of particulate carbon, which will simply be incorporated into the heating element forming a solid solution of molybdenum and carbon or molybdenum carbide (Mo2C or MoC). X-ray diffraction analysis shows that the heating element contains a mixture of molybdenum and molybdenum carbide along with trace amounts of unidentified phases due to the insufficient number of peaks. In one case, the ratio of molybdenum to molybdenum carbide (such as Mo2C) is close to 2:1.

[0081] The composition of the heating element 407 may include trace to small amounts of aluminum, yttrium, and oxygen due to the partial firing in a nitrogen atmosphere using a liquid that forms an oxide sintering phase (A2O3-Y2O3). The presence of trace to small amounts of elements in the heating element / electrode composition must be considered because it is well known that the addition of small amounts of dopants can affect the electrical properties of metals and ceramics (a compound of a metal and a non-metal).

[0082] The described heating element 407 provides several highly desirable properties, including: (1) an ability to withstand thermal stresses (i.e., a coefficient of thermal expansion sufficient to that of the ceramic substrate of the heater base disk assembly 420); (2) chemical compatibility (i.e., inertness) relative to the ceramic substrate; (3) an ability to be co-fired with the ceramic substrate; and (4) of particular note, an improved stability of resistivity as a function of temperature (particularly at high operating temperatures). In fact, the described heating element 407 is observed to have a relatively low variation in resistivity (i.e., resistance is relatively insensitive to temperature variations) over the desired operating range of about ambient temperature to about 850°C due to a relatively low resistivity coefficient of approximately 0.001 (1 / K) measured from about ambient temperature to about 850°C relative to pure molybdenum having a resistivity coefficient of 0.005 (1 / K) over the same temperature. In one embodiment, as shown in FIG. 28 , within a temperature range from about 300° C. to about 600° C., the resistance is within a range from about 4.18 ohms to about 4.28 ohms.

[0083] The multi-layer structure of the electric heater device as disclosed herein, when installed in a vacuum wafer processing chamber, is also leak-proof and provides a scalable design that can accommodate multiple zones, thus presenting a solution that can have a single heating zone or multiple heating zones for better temperature uniformity. The construction also allows for the addition of one or more thermocouples (e.g., temperature sensors). Thermocouples are added between layers 402 and 403 and survive the ceramic process.

[0084] Additionally, the aforementioned concentrations involving doping of molybdenum with carbon and aluminum and possibly oxygen produce the unexpected discovery that reduced sensitivity of the resistance to temperature allows for easier temperature control, chemical compatibility at high temperatures, and compatibility with aluminum nitride substrates during co-firing / sintering of the assembly.

[0085] In at least this embodiment disclosed herein, the electric heater device 400 can be constructed according to the following steps: a. Prepare a green body comprising aluminum nitride (i.e., a self-supporting body formed by consolidating ceramic powder using a binder in a mold under sufficiently high pressure). Next, process the green body to produce a disc-shaped substrate on which the heating element 407 can be printed and / or positioned. b. Prepare a conductive heating element composition including molybdenum powder, organic binder and solvent using any of several known coating or paste manufacturing techniques. Alternatively, a powder, a coating or a highly loaded one from a pre-cut pattern of a polymer sheet as disclosed above for the electric heater device 100 may be prepared, each including one or more refractory hard metals (such as molybdenum, tungsten and / or tantalum, etc.) in the compositions / concentrations disclosed herein. c. Next, a masking film is applied to one of the surfaces of the green body disc and a laser engraving technique is used to produce a well-defined pattern of shallow trenches comprising the desired depth, width and length. d. Next, apply a molybdenum coating to uniformly fill the trenches so that the molybdenum surface and the aluminum nitride surface are at the same height relative to the baseline surface. Alternatively, apply or place one of a powder, a coating, or a high load from a pre-cut pattern of a polymer sheet as disclosed above to fill the trenches, each including one or more refractory hard metals (such as molybdenum, tungsten and / or tantalum, etc.) in the composition / concentration disclosed herein. Next, fill the through hole 409 to create a power lead connected to the opposite surface. e. Remove the mask and check the thickness uniformity of the pattern of vias 409 and heating elements 407 and repair if necessary. f. Next, continuous powder extrusion in a mold is followed by processing for encapsulating or embedding the conductive pattern of the heating element into a multi-layer disc assembly 420 structure as shown in FIG. 23 . g. Alternatively, a lamination process may be adapted to encapsulate or embed the conductive pattern. A suitable lamination process that may be adapted for this purpose may include a process developed by Helysis Inc. for producing 3D objects by stacking sheets of laser cut paper fed by a roll-to-roll process known as Laminated Object Manufacturing, the entire contents of which are incorporated herein by reference. By utilizing the principles of this process, sheets of aluminum nitride may be produced by ceramic processes known in the art such as extrusion (as described herein), rolling, tape casting, spray deposition, etc. The surface of a sheet may be laser cut for through connections and printed with conductive element coatings. However, instead of adding powder on top of a sheet including a printed conductive element pattern and then compressing the powder, the printed sheets can be stacked on top of each other and initially joined by using a solvent according to the teachings of U.S. Patent No. 4,024,629 entitled "Fabrication Techniques for Multi-Layer Ceramic Modules," the entire contents of which are incorporated herein by reference. The assembly can be further consolidated by warm isostatic pressing, hydroforming, or an equivalent forming technique. The above-described laminated object process has been highly automated to produce complex 3D structures, which suggests that the process for making the electric heater device described herein can also be highly automated. It should be noted that the principle described herein of producing two interconnected 3D structures: one 3D structure that is electrically insulating but thermally conductive and another 3D structure that is electrically conductive can be deployed using other lamination processes to produce a matrix of aluminum nitride containing conductive patterns of heating elements, interconnects, sensors, etc. The internal structure described herein. These other layered fabrication methods include: binder jetting, fused filament deposition, spray deposition, UV curing polymers with highly loaded ceramic or metal powders as in stereolithography. After fabricating a green body of aluminum nitride containing an internal structure as described herein of conductive heating elements, interconnects, power leads, thermocouples, etc., the remainder of the process steps described below may apply. h. The resulting disk assembly 420 is then subjected to binder burnout and sintering in a nitrogen atmosphere. Binder burnout is performed in a nitrogen environment under controlled heating so that a small amount of residual carbon is produced. The amount of carbon produced by this process is kept below the oxygen content of the aluminum nitride that is not associated with the yttria, so that the composition of the liquid phase of aluminum oxide and yttria is such that the Al2O3 / Y2O3 molar ratio in the sintered body is between 10:3 and 0.1:1. A portion of this carbon is incorporated into the molybdenum powder that is shrunk and sintered to produce a dense heating element / electrode within the aluminum nitride matrix. As previously described, other dopants such as aluminum, nitrogen, oxygen, yttrium, and possibly boron are added during sintering due to the high temperature interaction between the heating element 407, the through hole 409, and the surrounding aluminum nitride matrix containing the aluminum oxide-yttria phase that acts as a sintering aid during sintering. The remainder of the carbon reacts with the Al2O3 to form aluminum nitride and carbon monoxide. At high temperatures (typically in the range of about 1600°C to about 1850°C), the composition of the heating element 407 is allowed to approach chemical equilibrium due to the interaction between the aluminum nitride, molybdenum, carbon and the sintering aids of aluminum oxide-yttria in a nitrogen atmosphere, resulting in the desired composition of the heating element 407. This description covers the fabrication of a sintered aluminum nitride disc heater. It is then machined to the final dimensions required for bonding to the hollow / tubular shaft 404 and post-bonding operations. i. The hollow / tubular shaft 404 is prepared from aluminum nitride using known procedures suitable for manufacturing articles from aluminum nitride and machined to final form. More specifically, the hollow / tubular shaft 404 is processed by machining the preform following a standard procedure for sintering aluminum nitride ceramics (i.e., extruding the powder into a tubular preform) to produce a green body of the desired shape and size, which is then subjected to binder burnout and sintering. The sintered portion is then machined to the final dimensions required to produce the hollow / tubular shaft 404 ready for joining to the disc assembly 420. j. The sintered hollow / tubular shaft 404 and the sintered aluminum nitride disc assembly 420 are attached to each other using any applicable bonding method. For example, diffusion bonding, metallization brazing, mechanical joints with high temperature seals, glass or glass ceramic bonding techniques, or other techniques may be used depending on the process requirements. A suitable bonding method is disclosed in U.S. Patent No. 5,096,863, entitled "Diffusion-Bonded Assembly of AlN Ceramic Bodies and Heat Dissipation Member Constituted Thereby," which is incorporated herein by reference in its entirety. k. The volume within the tubular shaft 404 is flushed with an inert gas to prevent oxidation of the components. 1. A power electrode system conceptually illustrated by components 411 , 412 , 413 is installed to feed current to the heating element 407 at the entry point 410 . m. A flexible conductor is connected to the external system and sealed at the feed-through 406. n. Although only one set of heating elements 407 and thermocouple sensors are shown for simplicity, in other embodiments, multiple heating elements and thermocouple sensors may be deployed. o. This connection system allows thermal expansion of components at high temperatures.

[0086] This unique manufacturing method that may include using a build-up process involving using a particle composition of most components, controlling the binder burn-out sequence, and sintering the susceptor disk produces a solution with unexpected results as disclosed herein.

[0087] Turning now to FIG. 24 , a graph showing resistivity as a function of temperature for pure tungsten and pure molybdenum is shown, which shows that resistivity increases steadily over temperatures ranging from about 0°C to about 3400°C for tungsten and from about 0°C to about 2200°C for molybdenum.

[0088] FIG. 25 and FIG. 26 show SEM / EDS spectroscopic analysis and representative element concentrations near the heating element / electrode in a sample disk assembly configured as disclosed herein. The palladium and gold spectral lines are from a thin conductive film of the sample. In this sample, the weight percentage of molybdenum is 70.8%, the weight percentage of carbon is 20.6%, the weight percentage of oxygen is 3.6%, the weight percentage of nitrogen is 3.1%, the weight percentage of aluminum is 1.9% and the weight percentage of yttrium is 0.0%, as shown in FIG. 26.

[0089] FIG. 27 shows a power versus temperature plot from a thermal simulation. A plot of this type can aid in sizing and selecting components for an appropriate control system. High temperature operations have high power requirements due to radiative heat losses. The Stefan-Boltzmann Law of radiative heat transfer shows a non-linear increase (fourth power) with temperature. The embodiments disclosed herein deliver high power for high temperature operations in the range of about 600°C to about 800°C due to high radiative heat losses, as depicted in FIG. 25 .

[0090] FIG. 28 shows resistance data taken from a representative heating element of the present invention. The data shows resistance stability at high temperatures (i.e., from about 500°C to about 600°C, and to some extent from about 300°C to about 500°C). Fluctuations are due to power variations and heating of the conductor. Resistance is calculated from voltage and current readings.

[0091] The embodiments described herein are possible examples of implementations and are set forth only for a clear understanding of the principles of the features described herein. Many changes and modifications may be made to the above-described embodiments without substantially departing from the spirit and principles of the techniques, procedures, devices, and systems described herein. All such modifications are intended to be included herein within the scope of the present invention and protected by the following invention claims.

[0092] 100: Electric heater device 105:Disc assembly 110: Heating element 111: Internal heating element 112: External heating element 115: Top side 116: Bottom side 120: Disc 122: Hole 125: Interconnection 126: Heating element interconnect 127: Internal heating element thermocouple 128: External heating element thermocouple 129: Heating element interconnect 130:Internal interface 131:Internal Interface 135: Socket 137:Terminal 138:Terminal 140: Thermal conductive layer 142: Inner hub 145: Thermal conductive layer 146: column 147: column 150: Vertical column 155: Groove 156: Inner groove 157: Outer groove 160: Tubular extension 162:Through hole 163:Through hole 164:Through hole 165: Groove 166: Heating element interconnection groove 167: Internal thermocouple interconnection groove 168: External thermocouple interconnection groove 170: Interconnection through hole 171: Interconnection through hole 172: Interconnection through hole 173: Interconnection through hole 174: Socket 175: Socket 176: Thermocouple socket 178: Annular groove 180: Ring protrusion 182: Flange 183: Ring protrusion 184: Top 186:Bottom wall 188:Outer wall 190:Outer wall 192: Inner wall 194: Inner wall 300: Steps 305: Steps 310: Steps 315: Steps 320: Steps 325: Steps 330: Steps 335: Steps 340: Steps 345: Steps 350: Steps 355: Steps 360: Steps 365: Steps 400: Electric heater device 401: Aluminum nitride layer 402: Aluminum nitride layer 402a: Power distribution layer 403: Aluminum nitride layer 404: Shaft 405:Metal chamber mounting flange 406: Feedthrough 407:Embedded heating element / conductive heating element 409:Through hole 410: Electrode entry point 411: Heating element / electrode assembly / rigid pin 412: Heating element / electrode assembly / spring 413: Heating element / electrode assembly 420:Disc assembly

Claims

1. An electric heater apparatus for processing a semiconductor wafer in a wafer processing chamber, comprising: A first thermally conductive layer comprising an electrically insulating material, a top side, and a bottom side; one or more conductive heating elements, or the like, disposed in each of one or more trenches disposed on the top side of the first thermally conductive layer, the one or more heating elements comprising molybdenum doped with carbon and aluminum, the doped molybdenum comprising a temperature-insensitive resistor within an operating temperature range from ambient temperature to about 850˚C, wherein the one or more heating elements are independently controllable to provide one or more heating areas along the top side of the first thermally conductive layer; and a second thermally conductive layer disposed on the top side of the first thermally conductive layer above the one or more heating elements.

2. The electric heater device of claim 1, wherein the first heat-conducting layer comprises a disk.

3. The electric heater device of claim 1, wherein the first thermally conductive layer is sintered, and wherein prior to sintering the first thermally conductive layer, the one or more heating elements initially comprise one of a powder, a coating, or a high load of a pre-cut pattern from a polymer sheet.

4. The electric heater apparatus of claim 1, wherein the concentration of carbon is allowed to vary from about 0.1 atomic% to about 50 atomic%, the concentration of aluminum is allowed to vary from about 0.1 atomic% to about 20 atomic%, the concentration of nitrogen is allowed to vary from about 0 atomic% to about 20 atomic%, the concentration of oxygen is allowed to vary from about 0 atomic% to about 5 atomic%, and the concentration of yttrium is allowed to vary from about 0 atomic% to about 3 atomic%.

5. The electric heater device of claim 1, wherein the first thermally conductive layer comprises aluminum nitride.

6. The electric heater device of claim 1, comprising a third thermally conductive layer disposed on the bottom side of the first thermally conductive layer, the third thermally conductive layer comprising a hub.

7. The electric heater device of claim 6, wherein the second thermally conductive layer and the third thermally conductive layer comprise aluminum nitride.

8. The electric heater device as claimed in claim 6, comprising a sintered column attached to the hub.

9. The electric heater device of claim 6, comprising a sintered column joined to the hub, wherein the joined column forms a helium-tight seal with the hub.

10. The electric heater device of claim 6, comprising one or more electrical interconnects disposed in each of one or more channels arranged on the bottom side of the first thermally conductive layer.

11. The electric heater device of claim 10, wherein the interconnects are configured to transmit electricity from the hub to the one or more heating elements and from the one or more heating elements to the hub in a circuit.

12. The electric heater device of claim 10, wherein the interconnects are configured to transmit sensor data from one or more temperature sensors to the hub.

13. The electric heater device of claim 12, wherein the one or more temperature sensors are disposed in each of one or more channels disposed on the bottom side of the first heat-conducting layer and below the third heat-conducting layer.

14. The electric heater device of claim 13, wherein the third heat-conducting layer is disposed above the one or more temperature sensors.

15. The electric heater device of claim 1, wherein the one or more heating elements and the first thermally conductive layer include a functionally similar coefficient of thermal expansion to avoid harmful cracks or fissures in the electric heater device.

16. The electric heater apparatus of claim 1, wherein the one or more conductive heating elements are sintered from a paste, a coating, a pre-cut polymer pattern, or a metal powder composed of molybdenum powder, a selective organic binder, a selective polymer, and a selective solvent.

17. The electric heater apparatus of claim 16, wherein the aluminum is incorporated by means of a high-temperature interaction between the molybdenum powder and a powder comprising aluminum nitride deposited on one or more conductive heating elements.

18. The electric heater device of claim 1, wherein the operating temperature is at least about 300˚C.

19. The electric heater apparatus of claim 1, wherein the molybdenum system is further doped with at least one of nitrogen, yttrium or oxygen.

20. The electric heater apparatus of claim 1, wherein the one or more conductive heating elements comprise molybdenum carbide.

21. An electric heater apparatus for processing a semiconductor wafer in a wafer processing chamber, comprising: A sintered disk comprising a thermally conductive and electrically insulating material, a top side and a bottom side; One or more conductive heating elements, or the like, disposed in each of one or more trenches arranged on the top side of the disk, the one or more heating elements comprising molybdenum doped with carbon and aluminum, the doped molybdenum comprising a temperature-insensitive resistor within an operating temperature range from ambient temperature to about 850˚C, wherein the one or more heating elements can be independently controlled to provide one or more heating areas along the top side of the disk; a first thermally conductive layer disposed above the one or more heating elements on the top side of the disk; one or more interconnects, or the like, disposed in each of one or more channels arranged on the bottom side of the disk; and a second thermally conductive layer disposed above the one or more interconnects on the bottom side of the disk, the second thermally conductive layer comprising a hub, wherein the one or more conductive heating elements are protected from chemical corrosion.

22. The electric heater apparatus of claim 21, wherein a concentration of carbon is permitted to vary from about 0.1 atomic% to about 50 atomic%, a concentration of aluminum is permitted to vary from about 0.1 atomic% to about 20 atomic%, a concentration of nitrogen is permitted to vary from about 0 atomic% to about 20 atomic%, a concentration of oxygen is permitted to vary from about 0 atomic% to about 5 atomic%, and a concentration of yttrium is permitted to vary from about 0 atomic% to about 3 atomic%.

23. The electric heater apparatus of claim 21, wherein the thermally conductive and electrically insulating material is aluminum nitride.

24. The electric heater device of claim 21, wherein the first thermally conductive layer and the second thermally conductive layer comprise aluminum nitride.

25. The electric heater device of claim 21, comprising a column attached to the hub.

26. The electric heater device of claim 25, wherein the column is engaged to the hub, and the engaged column forms a helium-tight seal with the hub.

27. The electric heater device of claim 21, wherein the interconnects include one or more electrical interconnects, and the electrical interconnects are configured to transmit electricity from the hub to the one or more heating elements and from the one or more heating elements to the hub in a circuit.

28. The electric heater device of claim 21, comprising one or more temperature sensors disposed in the one or more channels.

29. The electric heater device of claim 28, wherein the second thermally conductive layer is disposed above the one or more temperature sensors.

30. The electric heater device of claim 21, wherein the one or more heating elements and the disk include a functionally similar coefficient of thermal expansion to avoid harmful cracks or fissures in the electric heater device.

31. The electric heater device of claim 21, wherein the one or more heating elements can be independently controlled to provide one or more heating zones along the top side of the disk.

32. The electric heater apparatus of claim 21, wherein the one or more conductive heating elements are sintered from a paste, a coating, a pre-cut polymer pattern, or a metal powder composed of molybdenum powder, a selective organic binder, a selective solvent, and a selective polymer.

33. The electric heater apparatus of claim 32, wherein during the formation of the electric heater apparatus, the aluminum is incorporated by means of the high-temperature interaction between the molybdenum powder and the powder comprising aluminum nitride deposited on the one or more conductive heating elements.

34. The electric heater device of claim 21, wherein the operating temperature is at least about 300˚C.

35. The electric heater apparatus of claim 21, wherein the molybdenum system is further doped with at least one of nitrogen, yttrium or oxygen.

36. The electric heater apparatus of claim 21, wherein the one or more conductive heating elements comprise molybdenum carbide.

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