JP6382295B2 - Multi-zone heater - Google Patents

Description

  The present invention relates to a heater used in semiconductor processing, and more particularly to a heater having a plurality of heater zones and a thermocouple for monitoring the zones.

  In semiconductor manufacturing, silicon substrates (wafers) are processed at high temperatures to deposit a number of different materials. Temperatures typically range from 300-550 ° C, but can sometimes be as high as 750 ° C or higher. The deposited material “grows” in layers on the wafer surface. Many of these materials have extremely high temperature-sensitive growth rates, so temperature fluctuations within the wafer affect the local growth rate of the thin film, resulting in film thickness fluctuations during film deposition within the wafer. May cause.

  It is desired to control the thickness variation of the deposited thin film. It may be desirable to have a thicker (dome-shaped) film at the wafer center. It may be desirable to have a thicker (crater or dimple-like) film at the edges. It may be desirable to have a film thickness that is as uniform as possible (within tens of angstroms).

  One of the most direct ways to control the temperature of the wafer, and thus the film thickness profile immediately after deposition, is to place the wafer on a heater. By designing a heater with a specific watt density “map” that creates the desired temperature profile on the wafer, the desired film thickness profile can be created. At locations where higher temperatures on the wafer are desired, the watt density of the underlying heater is increased and decreased at locations where lower temperatures are desired.

  Chip manufacturers want to have the ability to perform various processes in the same processing chamber. Since the capital equipment for deposition is very expensive (more than $ 1 million per process chamber), it is desirable to maximize the number of required process chambers and minimize their number. Different temperature processes using different chemical reactions are performed in the same chamber to produce different thin films. Also, these various thin films may have different growth rate versus temperature behavior. To this end, chip manufacturers will desire the ability to change the watt density map of the heaters in a given process chamber “on the fly” to achieve the desired film thickness profile.

  In addition, the chip manufacturer performs the exact same “recipe” in multiple processing chambers to match the film thickness profile (as well as other characteristics that may be affected by temperature, such as film stress, refractive index). We hope to have the ability to produce thin films with It is therefore desirable to produce a heater with a watt density map that is very repeatable from unit to unit.

  By using multiple independent heater circuits within the heater, a heater with the ability to change the watt density map can be made. By varying the voltages and currents applied to the different circuits, the power level can be varied at each location of the individual circuit. The positions of these specific circuits are called “zones”. Increasing the voltage for a given zone (and hence the current because these heater elements are all resistive heaters) raises the temperature of that zone. Conversely, when the voltage to a zone is decreased, the temperature of that zone decreases. In this way, various watt density maps can be created with the same heater by varying the power for the individual zones.

  In order to use a multi-zone heater efficiently, at least two constraints affect the ability of the chip manufacturer. The first constraint is that the state-of-the-art heater has only one control thermocouple. The plate-shaft design currently used for heaters allows for thermocouple positioning only at the center of the heater plate or within a radius of about 1 inch from the center of the heater plate, so there is only one control thermocouple. I can not use it. Thermocouples are made of metal that is incompatible with the wafer processing environment and must therefore be isolated from the processing environment. Further, for the fastest response of the thermocouple (TC), it is best to operate the thermocouple in an atmospheric pressure environment rather than the normal processing chamber vacuum environment. Thus, the thermocouple can only be placed in the central hollow region of the heater shaft that is not in communication with the processing environment. If a heater zone is provided outside the heater shaft by more than 2 inches in diameter, no thermocouple can be installed to monitor the temperature of that zone and help control the temperature.

  This constraint has been addressed by using “slave” power ratios to control heater zones located outside the heater central region. The ratio of power applied to each of the central zone and other zones is set to produce the desired watt density map. The central control TC monitors the temperature of the central zone, and the power applied to the central zone (based on central control TC feedback) is then adjusted by a preset ratio and applied to all zones. For example, for a two zone heater, assume a ratio of 1.2 to 1.0 of the power applied to the outer and inner zones that creates the desired temperature profile. Assume that the heater control system determines that a voltage of 100 VAC is required to achieve the proper temperature by reading the temperature data provided by the central control TC. Using the slave ratio control method, a voltage of 120 VAC is applied to the outer heater zone and a voltage of 100 VAC is applied to the inner zone. Therefore, the watt density map can be adjusted by changing the slave ratio.

  This leads to a second constraint. State of the art heaters have inherent variations in the embedded heater resistance. Due to the high temperatures and high pressures required in current ceramic heater manufacturing processes, the achievable resistance tolerance can reach 50%. In other words, a typical resistance value for a semiconductor grade ceramic heater element is 1.8-3.0 ohms (at room temperature: the heater element material is usually molybdenum, and its resistance value increases as the operating temperature increases. In the range of (increased).

  This variability causes problems for maintaining a repeatable watt density map from unit to unit using a multi-zone heater controlled by the slave ratio method. For single zone heaters, resistance variation may not be a problem. This is because the control TC is used to monitor the actual operating temperature, and the power level applied to the heater is appropriately adjusted. However, when a multi-zone heater is provided and the resistance variation of the heater element reaches 50%, the slave ratio control method cannot create a repeatable watt density map for each unit.

  What is needed allows for the installation of multiple control TCs that can be physically located within individual heater zones to allow direct feedback and control, but still allow TCs in the processing chamber. It is to establish a heater design that keeps it isolated from the processing environment.

  The drawings shown in this specification are schematic in many respects, but are merely for illustrative purposes and are not intended to limit the scope of the present disclosure.

FIG. 3 is a diagram of a plate shaft mechanism used in semiconductor processing, according to some embodiments of the present invention. FIG. 6 is a cross-sectional view illustrating a joint between a plate and a shaft, according to some embodiments of the present invention. FIG. 3 is a diagram of a plate shaft mechanism in a processing chamber, according to some embodiments of the present invention. FIG. 3 is a diagram of a heater device in a processing chamber, according to some embodiments of the present invention. 2 is an exemplary schematic cross-sectional view of a multi-zone heater according to some embodiments of the present invention. FIG. FIG. 2 is an exemplary bottom view of a multi-zone heater according to some embodiments of the present invention. FIG. 3 is an illustration of a bonded cover plate according to some embodiments of the present invention. FIG. 3 is an illustration of a cover plate according to some embodiments of the present invention. 1 is a perspective view of a heater according to some embodiments of the present invention. FIG. FIG. 2 is a perspective exploded view of a heater according to some embodiments of the present invention. FIG. 3 is an exemplary cross-sectional view of a heater with a multilayer plate according to some embodiments of the present invention. FIG. 2 is a close-up partial cross-sectional view of a multilayer plate according to some embodiments of the present invention. FIG. 2 is an exemplary cross-sectional view of a heater having multiple heater zones and thermocouples, according to some embodiments of the present invention. FIG. 14 is a close-up cross-sectional view of the plate-to-shaft joint area along line 14-14 of FIG. 13 in accordance with some embodiments of the present invention. FIG. 15 is a top view of the central hub taken along line 15-15 of FIG. 14 in accordance with some embodiments of the present invention. FIG. 16 is a partial cross-sectional view illustrating aspects of the central hub along line 16-16 of FIG. 15 in accordance with some embodiments of the present invention. FIG. 18 is a mapping diagram of multiple heater zones along line 17-17 of FIG. 13 in accordance with some embodiments of the present invention.

  In one embodiment of the present invention, a multi-zone heater with multiple thermocouples is provided so that different heater zones can be monitored independently with respect to temperature. Independent thermocouples can route their leads from the heater shaft into a passage or recess that can withstand both the internal atmosphere of the shaft and the process chemicals in the processing chamber. It can be closed with a bonding process that provides a configured hermetic seal. Independent thermocouples can route their leads from the heater shaft into the spaces, recesses, or cavities between the plate layers, each plate layer being connected to the internal atmosphere of the shaft and the process chemicals in the processing chamber. They can be joined with a joining process that provides a hermetic seal configured to withstand both. The first plate layer or passage cover, which can be the bottom plate layer, is a thermocouple and its lead wire using a bonding process that brazes the second plate layer or heater plate with any suitable bonding material such as aluminum. Can be trapped.

  FIG. 1 shows an exemplary plate and shaft mechanism 100 such as a heater used in semiconductor processing. In some embodiments, the plate shaft mechanism 100 is constructed of a ceramic such as aluminum nitride. The heater includes a shaft 101 that supports the plate 102. The plate 102 has an upper surface 103. The shaft 101 can be a hollow cylinder. The plate 102 can be a flat disk. There may be other auxiliary parts. In some current processes, the plates 102 can be individually manufactured in an initial process with a processing oven that forms a ceramic plate. In some embodiments, the plate can be joined to the shaft using a low temperature hermetic joining process described below.

  FIG. 2 shows a cross-sectional view in which a first ceramic body, for example a ceramic shaft 191, is joined to a second ceramic body, for example a ceramic plate 192, which can be made of the same or different materials. A bonding material, such as a brazing layer 190, that can be selected from a combination of brazing layer materials described herein can be included, and the bonding material can be supplied to the joint according to the methods described herein. it can. In some aspects, the plate can be aluminum nitride and the shaft can be aluminum nitride, zirconia, alumina, or other ceramic. In some aspects, it may be desirable to use a shaft material with a lower heat transfer coefficient in some embodiments.

  In the joint shown in FIG. 2, the shaft 191 may be positioned such that the shaft 191 abuts the plate, and between the joining surfaces, for example, between the shaft surface 193 and the plate surface 194. Only the adhesive layer is present. The joining surface 194 of the plate 192 is preferably present in the recess 195 in the plate. The thickness of the joint is exaggerated for clarity. In one exemplary embodiment, the plate and shaft can both be made of aluminum nitride, and both can be formed separately beforehand using a liquid phase sintering process. In some embodiments, the plate can be approximately 9-13 inches in diameter and 0.5-0.75 inches thick. The shaft can be a hollow cylinder 5-10 inches long with a wall thickness of 0.1 inches and an outer diameter in the range of 1-3 inches. The plate may include a recess configured to receive the outer surface of the first end of the shaft.

  As can be seen from FIG. 3, the joint brazing material used in heaters or other mechanisms may straddle between two completely different atmospheres, which can cause significant problems with conventional brazing materials. . On the external surface 207 of the semiconductor processing apparatus, such as the heater 205 of the semiconductor wafer chuck, the brazing material needs to be compatible with the process occurring in the semiconductor processing chamber 200 where the heater 205 will be used and the environment in which it exists. The environment 201 present in the processing chamber 200 may include fluorinated materials. The heater 205 may have a substrate 206 attached to the upper surface of the plate 203 supported by the shaft 204. On the inner surface 208 of the heater 205, the braze layer material must be compatible with another atmosphere 202, which may be an oxidizing atmosphere. Conventional brazing materials used with ceramics failed to meet both these criteria. For example, brazing elements containing copper, silver, or gold are not suitable because they can interfere with the lattice structure of the silicon wafer being processed. However, in the case of a brazed joint that joins the heater plate to the heater shaft, the inside of the shaft is usually subjected to high temperatures and has an oxidizing atmosphere inside the center of the hollow shaft. This portion of the brazed joint that is exposed to this atmosphere will be oxidized, and oxidation may progress into the joint, resulting in a poor tightness of the joint. In addition to structural connections, the joints between the shafts and plates of these mechanisms used in semiconductor manufacturing need to be sealed in many, if not all, applications.

  FIG. 4 shows a schematic diagram of one embodiment of a heater column used in a semiconductor processing chamber. The heater 300, which may be a ceramic heater, may include a high frequency antenna 310, a heater element 320, a shaft 330, a plate 340, and a mounting flange 350.

  In some embodiments of the present invention, as seen in FIG. 5, an apparatus for semiconductor manufacturing such as a wafer chuck or heater 500 may be provided. The apparatus may include an elongate shaft 516, which is cylindrical and includes first and second opposite ends 517, 518 and a longitudinal central axis 519 extending between the ends 517, 518. It is good to prepare. A passage or central hole 504 extends through the shaft 516 from the first end 517 to the second end 518. The plate 521 can be joined to the first end 517 of the shaft 516. Plate 521 can be any suitable shape, such as a cylindrical shape, and can be centered on axis 519. In one embodiment, the plate 521 has a radius that is greater than the radius of the shaft 516. In one embodiment, the plate 521 has a portion 522 such as an annular portion that extends radially outward from the shaft 519 over the shaft 516. Each of shaft 516 and plate 521 can be made of any suitable material, such as a ceramic material, and in one embodiment, the shaft and plate are each made of aluminum nitride. Plate 521 may comprise a plurality of heater zones, each heater zone having at least one heater. In one embodiment, plate 521 comprises a first or central heater zone 526, which may be centered about axis 519, a second or intermediate heater zone 527, and a third or end zone 528, for example. Each heater zone may be any suitable shape, and in one embodiment, in a plane, the central zone 526 is circular and the intermediate zone 527 and end zone 528 are each annular. The heater zones can overlap, for example, as shown in FIG. 5, or can be spaced from each other without overlapping.

  The apparatus 500 may include a plurality of temperature sensors, such as at least one temperature sensor for each heater zone. In one embodiment, the first temperature sensor 505 is disposed near or adjacent to the central heater zone 526 of the plate 521, the second temperature sensor 506 is disposed near or adjacent to the intermediate heater zone 527, and the third A temperature sensor 507 is disposed near or adjacent to the end heater zone 528. In one embodiment, each temperature sensor is located at the radial center of the respective heater zone, but other location choices for the temperature sensor relative to the respective heater zone are within the scope of the present invention. In one embodiment, each of the second and third temperature sensors 506, 507 is disposed on the portion 522 of the plate 521. In one embodiment, the temperature sensors 505, 506, 507 are spaced radially from one another, and in one embodiment, the second temperature sensor 506 is spaced radially outward from the first temperature sensor 505, The third temperature sensor 507 is arranged radially outward from the second temperature sensor 506. Each temperature sensor may be of any suitable type, and in one embodiment, each temperature sensor is a thermocouple.

  Electrical leads extend from each temperature sensor to the first end 517 of the shaft 516 and through the central hole 504 to the second end 518 of the shaft. At this time, the first electrical lead 531 is electrically connected or joined to the first sensor 505 at one end, the second electrical lead 532 is electrically connected or joined to the second sensor 506 at one end, and the third The electrical lead 533 is electrically connected or joined to the third sensor 507 at one end. Each lead is accessible at the second end 518 of the shaft 516 and monitors the temperature of the plate 521 independently, more specifically in the vicinity of each temperature sensor, and thus in each heater zone. In the vicinity of 526, 527, 528, it extends through the shaft so that the plate temperature can be monitored.

  The plate 521 can be formed by any suitable method, and in one embodiment is manufactured with multiple layers, such as multiple planar layers. In one embodiment, the first plate layer or cover plate 501 of the device 500 covers the hollow region or recess 503 that can be adjacent to or in communication with the hollow core 504 of the heater shaft, while the second plate layer of the device 500. Alternatively, it can be adhered to the back surface of the heater plate 502. The recess can serve as a conduit for temperature sensor leads 531-533, and one or more of the leads 531-533 can be located in each of the recesses or passages. Individual control to directly monitor the local temperature in each heater zone, for example, heater zones 526-528 of multi-zone heater 500, by utilizing radial feeders, recesses, or passages such as covered hollow areas. It becomes possible to use a thermocouple. Thermocouples 505, 506, 507 can be mounted within the respective thermocouple holes 508, 509, 510 located in each individual heater zone. Thermocouples can be attached to these holes located within the covered hollow region or passage 503. In some embodiments, plate machining may be applied to the passage 503 to allow the temperature sensor or thermocouple 505-507 to be installed deeper. Thereafter, the thermocouple can be covered with a ceramic cover plate 501 positioned between the heater plate and the shaft on the back side of the heater plate. Thereafter, the heater plate 502, the hollow area cover plate 501, and the heater shaft 516 can be bonded together. This isolates the thermocouple from the processing environment and provides direct feedback of the temperature of each heater zone for conventional control. In some heater designs, the heater is completely embedded within the plate during the plate manufacturing process. This treatment involves a high temperature of about 1700 ° C. and may involve a high pressure contact force during plate formation. Although the heater element itself can be adapted to withstand this process, thermocouples 505-507, which may be made of Inconel, and leads 531-533 to this thermocouple cannot withstand this process. As a result, the thermocouple 505-507 must be installed after final sintering and pressurization of the ceramic plate 521 to protect the thermocouple from process chemicals that the heater 500 will be exposed to during its use. . By utilizing multiple thermocouples that monitor the temperature of multiple areas of the plate 521 with separate heaters, it is possible to control the temperature of these areas of the plate based on actual temperature measurements.

  The thermocouple hole may reach through the plate 521 to the heater element. In some embodiments, the heater element can comprise an open region, and the thermocouple hole does not extend into the heater element, but extends to the same depth as the heater element in the region where the heater element gap or space exists. It is like that. In some embodiments, after manufacturing a heater plate with multi-zone heater elements therein, the hollow region 503 and thermocouple holes can be machined in the heater plate. The multi-zone heater element can be present in the ceramic heater plate when it is manufactured. The low temperature bonding process described herein can be utilized to join the hollow area cover plate 502 to the heater plate 501 and in some embodiments to a portion or end 517 of the shaft 516.

  FIG. 6 is a bottom view of a plate having a shaft, for example, a plate to which a shaft 516 is attached, for example, a plate 521 of a semiconductor processing wafer chuck 500. A recess, groove or hollow passage region 503 extends radially outward from a portion of the plate present in the central portion of the hollow shaft 516. One or more thermocouple holes that allow the insertion of temperature sensors or thermocouples for respective heater elements provided in the respective heater zones, eg, the intermediate heater zone 527 and the end heater zone 528, are formed in this hollow space. It can be inside the passage area 503, otherwise the temperature cannot be monitored directly.

  FIG. 7 illustrates a portion of a heater plate 502 comprising a recess, space or hollow region 503 and a cover plate 501 according to some embodiments of the present invention, such as a portion included as a semiconductor manufacturing heater or wafer chuck, for example. FIG. The cover plate 501 may be configured to fit into a slot, recess, or opening provided at the bottom of the heater plate. The groove, passage, recess, or slot is provided in at least one of the heater plate 502 and the cover plate 501. In one embodiment, a recess or passage 503 shown in the cross-sectional view of FIG. 7 can exist below the slot to route the electrical lead or coupling 520 from the temperature sensor or thermocouple to the shaft center. Particularly suitable temperature sensors or thermocouples are arranged on the plate radially beyond the outer radius of the shaft so that they do not lie on the shaft. A suitable joint 521 can be, for example, any of the joint layers disclosed herein, and the joint 521 can cause the passage 503 to be oxidized when the cover plate 501 is attached to the heater plate 502. Since there is a possibility of encountering the atmosphere in the center of a certain heater shaft, it straddles different atmospheres. This atmosphere in the passage can allow a much better thermocouple function for the thermocouple in the passage area. The other side of the joint will encounter an atmosphere that can contain a corrosive process gas such as a fluoride in the process chamber. Appropriate bonding methods result in bonding that is compatible with these various atmospheres, such as hermetic bonding of the type disclosed herein. The electrical lead 520 of the device or heater shown in FIG. 7 extends through the heater plate 502 in a recess, passage, or passage that is hermetically sealed from the environment of the semiconductor processing chamber in which such a device is used.

  FIG. 8 is configured to join a second plate layer or hollow cover plate 530, for example included as part of a heater or wafer chuck for semiconductor manufacturing, to the bottom of the first plate layer or heater plate 502. A cross-sectional view of a portion of a first plate layer or heater plate 502 is shown. The heater plate 502 and the cover plate 530 may form a heater plate such as the plate 521. A hollow cover plate 530 may cover the thermocouple hole and the electrical lead or thermocouple coupling wire 520 at the bottom of the heater plate. As a conduit for an electrical lead or wire 520 that is hermetically sealed from the environment of the semiconductor processing chamber and extends radially outward from the heater shaft and connected to a temperature sensor or thermocouple disposed on a portion of the heater plate. To form a groove, passage, recess or slot 545 suitable for functioning, at least one of the opposite surface of the heater plate 502 and the cover plate 530 comprises a groove, passage, recess or slot. A suitable bonding layer or bond 546 can be, for example, any of the bonding layers disclosed herein, and the cover plate 530 can be attached to the heater plate 502 to form a hermetic seal therebetween. it can. In the exemplary embodiment of FIG. 8, passage 545 extends within or through cover plate 530 as opposed to extending within or through heater plate or structure 502. ing.

  9 and 10 are a perspective view and a partially exploded perspective view, respectively, illustrating a heater 500 according to some embodiments of the present invention. The heater 550 is similar to the heater described above, and the same reference numerals are used to describe such heaters and the same components of the heater 550. A hollow cover plate 551 is provided, and the cover plate can comprise a continuous ring piece or ring 552 configured to exist between the shaft 516 and the bottom 502 of the heater plate. In one embodiment, the cover plate 551 and the ring component or ring 552 are integrally formed of the same material and are not separate components. For electrical leads 532, 533 that are hermetically sealed from the semiconductor processing chamber environment and that extend radially outward from the shaft 516 of the heater 550 and are connected to a temperature sensor or thermocouple disposed on a portion of the heater plate 521. At least one of the opposite surface of the heater plate 502 and the cover plate 551 comprises a groove, passage, recess or slot to form a groove, passage, recess or slot suitable for functioning as a conduit. . In the heater 550, the grooves, passages, recesses, or slots for the temperature sensor leads are inside the cover plate 551 as opposed to being inside or extending through the heater plate or structure 502. Or extend through. The hollow cover plate 551 allows the thermocouple leads or wires 532, 533 to be routed from the outside of the periphery of the shaft 516 at the bottom of the plate 521 to the center of the shaft. In some embodiments, the heater plate 502, the hollow cover plate 551 with the ring component 552, and the shaft 516 can be coupled together in a single heating operation that brazes the components together. Any of the bonding processes and bonding layers disclosed herein can be utilized in this context.

  In some embodiments of the present invention, it can be seen that the plate and shaft mechanism 556, eg, a heater or wafer chuck, includes a plate assembly or plate 557 and a shaft 558, as seen in the enlarged view of FIG. The plate assembly 557 includes layers 561, 562, 563, which can be fully fired ceramic layers prior to assembly into the plate assembly 557. The first or top plate layer 561 overlies the second or middle layer 562 with the electrode layer 564 present between the top plate layer 561 and the second or middle layer 562. The intermediate layer 562 lies on the lowermost layer 563 with the heater layer 565 existing between the intermediate layer 562 and the lowermost layer 563.

  In some embodiments, thermocouples can be mounted between each plate layer to monitor temperature at different locations. The multi-layer plate assembly allows access to areas on one or more surfaces of one or more plates so that surface machining can be performed after final firing of the ceramic plate layers. . Furthermore, this access to the surface also allows the assembly of components into the surface of the plate layer and the space between the plate layers.

  Layers 561, 562, 563 of plate assembly 557 include ceramics such as aluminum nitride for heaters, alumina, doped alumina, AlN, doped AlN, beryllia, doped beryllia, etc. for electrostatic chucks. Another ceramic material can be used. The plate assembly layers 561, 562, 563 that comprise the substrate support may be fully fired ceramic prior to introduction into the plate assembly 557. For example, layers 561, 562, 563 are fully fired as plates in special ovens for high temperature, high contact pressure, or tape casting, or spark plasma sintering, or other methods, and then their use and plate assembly Can be machined to the final dimensions required by their position in the stack. The plate layers 561, 562, 563 can be bonded together using a brazing process with the bonding layer 567, thereby providing a final assembly of the plate assembly 557 with a pressurizer for high contact stress applications. This can be done without the need for a special high temperature oven.

  In embodiments where the shaft is also part of the final assembly, as in the case of the plate and shaft mechanism, the joining process step of the plate assembly 557 and the shaft 558 is also specially equipped with a pressurizer for high contact stress applications. A brazing process performed without the need for a high temperature oven can be utilized. In some embodiments, the joining of the plate layers and the joining of the shaft and plate assembly can be performed in a simultaneous processing step. The shaft 558 can be bonded to the plate assembly 557 with a bonding layer 568. In some embodiments, the bonding layer 568 can be the same brazing element as the bonding layer 567.

  An improved method of manufacturing a plate or plate assembly includes the additional processing steps described above and described in more detail below, which join the layers of the plate assembly and use laborious and costly high temperature and high pressure contact forces. A method of making the final plate assembly can be included without doing so. According to an embodiment of the present invention, the plate layers can be joined by a brazing method for joining ceramics. An example of a brazing method for joining the first and second ceramic bodies includes a brazing layer selected from the group consisting of aluminum and an aluminum alloy for joining the first ceramic body to the second ceramic body. Placing the first and second ceramic bodies together between the first and second ceramic bodies, heating the braze layer to a temperature of at least 800 ° C., and curing the braze layer to provide a hermetic seal. Cooling the braze layer to a temperature below its melting point to create. Various shapes of brazed joints can be implemented according to the methods described herein.

  In some embodiments of the present invention, a plate assembly with multiple layers can be presented such that there is a standoff between each plate layer, so that the bonding layer is heated and slightly When pressure is applied to the plates in the axial direction, there will be a slight axial compression so that the bonding layer is reasonably thin until the standoff on one plate contacts the adjacent plate. In some aspects, this allows not only control of the joint thickness, but also control of the dimensions and tolerances of the plate assembly. For example, the parallelism of various plate features may be defined by mechanical tolerances to the plate layer, and this aspect can be maintained during the joining process by the use of standoffs. In some embodiments, post-join dimensional control can be achieved utilizing a circumferential outer ring on the plate layer that overlies the inner ring on the adjacent layer to provide axial alignment. it can. In some embodiments, one of the outer ring or inner ring can also contact an adjacent plate in the axial direction perpendicular to the plate so that positional control is also achieved in the axial direction. Thus, axial position control can also determine the final thickness of the bonding layer between two adjacent plates.

  In some embodiments of the present invention, the interlayer electrode can be the same material as the bonding layer and can function in the dual capacity of both the bonding layer and the electrode. For example, an area previously occupied by an electrode in an electrostatic chuck may be occupied by a bonding layer instead, and the bonding layer functions as an electrode for providing an electrostatic clamping force, for example, and the bonding layer intervenes 2. In order to join two plates, it has a dual function of functioning as a joining layer. In such an embodiment, there is a labyrinth around the perimeter of the two joined plates, minimizing the parting line and normal access to the charged electrodes from the outer area of the plate.

  FIG. 12 shows a partial cross-sectional view of a plate assembly according to some embodiments of the present invention. The plate assembly is a multilayer plate assembly in which a heater and an electrode exist between different layers. The layers are joined with brazing elements and the final plate position in the direction perpendicular to the plate major plane is defined by standoffs 578, 579 on the plate.

  The first or top plate layer 571 overlies the second or bottom plate layer 572. The lower plate layer 572 overlies the third or lowermost plate layer 573. Although illustrated in FIG. 12 with three plate layers, different numbers of plate layers can be utilized depending on the needs of a particular application. The uppermost plate layer 571 is bonded to the lower plate layer 572 using the multifunction bonding layer 576. The multifunctional bonding layer 576 is configured to bond the uppermost plate layer 571 to the lower plate layer 572 and become an electrode. Such an electrode can be substantially a disc bonding layer, which also functions as an electrode. As can be seen from FIG. 12, the standoff 578 is configured to allow position control of the uppermost plate layer 571 relative to the lower plate layer 572 in a direction perpendicular to the major plane of the plate layer. The outer peripheral portion of the uppermost plate layer 571 is configured to eliminate the parting line along the boundary 577 between the two plates at the peripheral portion. Prior to the step of heating and bonding the plate assembly, the thickness of the bonding layer 576 can be determined such that the bonding layer 576 is in contact with the uppermost plate layer 571 and the lower plate layer 572.

  The lower plate layer 572 overlies the lowermost plate layer 573. The heater 574 exists between the lower plate layer 572 and the lowermost plate layer 573. In this regard, a recess, cavity, on at least one of the opposing surfaces of the lower plate layer 572 and the lowermost plate layer 573 to form a recess, cavity, or space 580 for receiving the heater 574. Or a space is provided. In one embodiment shown in FIG. 12, a recess or cavity 580 is formed in the upper surface of the bottom plate 573 to receive the heater. The recess 580 can have any suitable size and shape, and can be circular in plan view, such as a cylindrical recess. The bonding layer 575 bonds the lower plate layer 572 to the lowermost plate layer 573. The bonding layer 575 can be an annular ring on the outer periphery of the plate layer. The standoff 579 is configured to allow position control of the lower layer 572 relative to the lowermost plate layer 573 in a direction perpendicular to the main plane of the plate layer. During the plate assembly joining step, the components shown in FIG. 12 can be pre-assembled and the assembled plate is joined using the process described herein to form a complete plate assembly. be able to. In some embodiments, the assembled plate can be further pre-assembled to the shaft and shaft joining layer so that the complete plate-shaft mechanism can be joined in a single heating step. This single heat treatment may not require a high temperature oven or a high temperature oven with a press adapted to provide high contact stress. Furthermore, in some embodiments, the completed plate and shaft assembly still meets the tolerance requirements of such devices used in semiconductor manufacturing, even though no post-joining machining is required. can do.

  In some embodiments, the top and bottom plate layers are aluminum nitride. In some embodiments, the bonding layer is aluminum. Examples of the bonding process and materials will be described later.

  FIG. 13 is an exemplary cross-sectional view of a plate and shaft mechanism 600, which can be a heater, wafer chuck, pedestal or susceptor, and that uses a plurality of multilayer plates 601 according to some embodiments of the present invention. A heater zone and a plurality of thermocouples are provided. An elongate shaft having a second end 642 opposite the first end 641 and a longitudinal axis 643 extending between the ends 641, 642 is provided. The first end 641 of the shaft 602 can be coupled to the bottom center of the plate 601 by any suitable means including those disclosed herein. In these embodiments, a bonding layer that is hermetic and resistant to corrosive process chemicals can be used to bond adjacent plates and is surrounded by an inner side 603 of shaft 602. The temperature sensor can be inserted into a portion 605 of the plate 601 that extends outside the radius of the region, yet still protected from the corrosive process gas that the heater may suffer. For example, as shown in FIG. 13, the plate 601 can include a suitable lift pinhole or opening 630.

  In some embodiments, the use of multi-layer plates allows access to the space between layers where thermocouples can be placed in areas that cannot be otherwise monitored. For example, in a plate and shaft mechanism 600 as seen in FIG. 13, all output and monitoring is typically routed out of the processing chamber through the hollow center or shaft 603 of the shaft 602 and through the chamber penetration. Wired. In prior art mechanisms where the entire ceramic plate and shaft mechanism is sintered together at high temperature, the only area available for embedding the thermocouple and wiring the telemeter down along the hollow shaft is that of the hollow shaft. It was in the area in the middle. For example, it is possible to drill a hole in the bottom of the plate using a long drill that is adapted to descend along the center of the hollow shaft. A thermocouple can then be inserted into the hole and used to monitor the temperature of the plate only in its central region. The restriction of the position where the thermocouple can be attached makes it impossible to monitor the temperature at a position off the inside of the hollow shaft.

  In some embodiments of the present invention, a central hub 604 can be utilized to help seal the interlayer space of the plate layer from the atmosphere that may be present in the shaft. In such an embodiment, the central hub 604 can function as a penetration from the central portion of the shaft 602 and the interlayer space of the plate layer.

  In some embodiments, the plate 601 of the heater 600 can be assembled from three plate layers. Each plate layer can be made of a fully fired ceramic such as aluminum nitride. Each plate layer can be pre-machined to final or near final dimensions prior to assembly into a multilayer plate assembly. The first or top plate layer 612 can lie on the second or middle plate layer 611, and the second or middle plate layer 611 can lie on the third or bottom plate layer 610 as well. Each plate layer can be cylindrical in shape, and in one embodiment each plate has the same transverse dimension or diameter, which is equal to the transverse dimension or diameter of plate 601. The intermediate plate layer can be bonded to the lowermost plate layer using the bonding layer 614 at the outer periphery thereof. The metal layer 613 between the top plate layer 612 and the intermediate plate layer 611 can function as an RF layer and as a bonding layer between such plate layers. The plate 601 has a portion 605 that extends radially outward from the axis 643 beyond the shaft 602.

  One or more heater elements may exist between the intermediate plate layer 611 and the lower plate layer 610. The intermediate plate layer 611 is configured to receive the heater element such that the heater element 621 is present in the groove 620 at the bottom of the intermediate plate layer 611. An example of the element arrangement of the multi-zone heater is shown in FIG. The heater element is divided into three radial zones, each of which has two halves, so it is divided into a total of six zones. In this regard, the plate 602 is annular and has a central heater zone 647 that can be divided into first and second central half zones 647a, 647b, and an annular first and second intermediate zone. It includes an intermediate heater zone 648 that can be divided into half zones 648a, 648b and an end heater zone 649 that is annular and can be divided into first and second end half zones 649a, 649b. Each such half zone may be semi-annular. The central heater zone 647 can be centered about the axis 643, the intermediate heater zone can be located radially outward from the axis 643 and the central heater zone 647, and the end heater zone is radial from the axis and the intermediate heater zone. Can be placed on the outside. Two radial zones, an intermediate heater zone 648 and an end heater zone 649, are in a portion 605 of the plate 601 and well outside the inner periphery of the hollow shaft. The heater element 621 can be made of molybdenum and can be potted into the groove using an AlN potting compound 622. A power lead 646 for the heater element 621 extends outward from the central hub and sends power to the individual heater circuits.

  In one embodiment, for example, as shown in FIG. 17, at least one first temperature sensor 651 is positioned near or adjacent to the central heater zone 647 of the plate 601 and at least one second temperature sensor 652 is positioned in the middle of the plate. Located near or adjacent to the heater zone 648, at least one third temperature sensor 653 is positioned near or adjacent to the plate end heater zone 649. Any suitable location of the temperature sensor for each heater zone is also within the scope of the present invention. In one embodiment, each of the second and third temperature sensors 652, 653 is disposed on a portion 605 of the plate 601. Thus, temperature sensors configured to allow temperature monitoring and located in heater zones 648, 649 are placed on the plate at a radial distance greater than the inner diameter of shaft 602. In one embodiment, the temperature sensors 651, 652, 653 are radially spaced from one another, and in one embodiment, each second temperature sensor 652 is radially outward from at least one first temperature sensor 651. The third temperature sensors 653 are arranged radially outward from at least one second temperature sensor 652. Each temperature sensor can be of any suitable type, and in one embodiment, each temperature sensor is a thermocouple.

  Electrical leads 661 extend from each of the temperature sensors 651-653 to the first end 641 of the shaft 601 and through the central hole 603 to the second end 642 of the shaft. Each lead 661 is accessible at the second end 642 of the shaft and monitors the temperature of the plate 601 independently, more specifically in the vicinity of the individual heater zones 647, 648, 649. It extends through the shaft 601 so that the plate temperature can be monitored.

  In the embodiment of FIGS. 13-16, it can be seen that various components are attached to the bottom surface of the intermediate plate layer 611. In some aspects, one or more recesses, passages, grooves, or slots 662 can be machined into this surface to attach the heater element 621 and electrical lead 661. Such one or more recesses can include a single cavity, for example, can be cylindrical, and in one embodiment can be centered on axis 643. A hole that functions as a thermocouple hole for mounting the thermocouples 651 to 653 can be formed on this surface. After this machining, the heater element 621 can be attached and potted. In some embodiments, the heater element can be a molybdenum wire disposed in the groove. In some embodiments, heater elements can be deposited in the grooves using thick film deposition techniques. Further, it is possible to perform potting by incorporating thermocouples 651-653. The heater element can be attached to a power lead 646, which can be a bus bar. In embodiments utilizing a central hub, the power lead 646 and the thermocouple lead 661 can be routed via the central hub. The multi-layer plate stack 601 can be assembled, for example, in an upside down fashion, and all elements including the braze layer can be assembled, which is then processed into a final complete heater assembly. The brazing step described herein may include an oxygenated atmosphere and a fluoride, using a hermetic seal that has become resistant to the atmosphere that the heater will encounter while maintaining semiconductor manufacturing. All the components will be joined.

  By routing lead wires, such as thermocouple leads having Inconel outer sides, via the central hub 604, these lead wires can also be routed via the central hub and sealed with brazing elements. For example, the lead can be routed through a hole in the central hub with a stepped hole, and a cylindrical brazing element can be placed around the lead prior to the brazing step. The central hub 604 also allows the space between the plates between the intermediate plate layer 611 and the lowermost plate layer 610 to be hermetically sealed from the space inside the shaft. As shown in FIG. 14, a bonding layer 615 can be utilized to seal the shaft from the bottom of the bottom plate layer 610 and to seal the central hub 604 from the top surface of the bottom plate layer 610. Another bonding layer 616 can be utilized. In some embodiments, the space between the plates is hermetically sealed when the entire heater assembly is heated in vacuum during the brazing step to join all of the various surfaces that will be attached by the various bonding layers. Can be sealed in a vacuum state. In some embodiments, by having a space between the plates that mount the thermocouple, the thermocouple can be well shielded from the temperatures found in the area except the mounted portion.

  15 and 16 show the central hub in top view and partial cross-sectional view, respectively. A central hub can be used as an airtight penetration that isolates the central region of the shaft from the space between the plates between the middle plate layer 611 and the bottom plate layer 610. Leads 646 and thermocouple leads 661 that supply power to the heater are routed through a central hub and sealed with brazing material in the same brazing process step that joins and seals the other components together. Can be stopped.

  FIG. 17 illustrates a multi-zone heater element, such as the heater 600 found in some embodiments of the present invention. The heater element is divided into three radial zones 647, 648, 649 in the plate 601 shown in the plan view of FIG. 17, each of which has two halves, for a total of six heater zones 647a, 647b, 648a. , 648b, 649a, 649b. Two of the radial zones, the intermediate heater zone 648 and the end heater zone 649 are in the plate portion 605 and well outside the outer perimeter inside the hollow shaft 602. In one embodiment, at least one first temperature sensor or thermocouple 651 is provided in each central heater zone 647a, 647b of plate 601 and at least one second temperature sensor or thermocouple 652 is in each middle of plate 601. At least one third temperature sensor or thermocouple 653 is provided in each heater zone 649a, 649 of the plate 601 provided in the heater zones 648a, 648b. In one embodiment, as shown in FIG. 17, when such a heater zone is viewed in plan, the temperature sensor is provided in the range of the respective heater zones 647a, 647b, 648a, 648b, 649a, 649b. In one embodiment, the heater zone of the plate 601 is substantially planar and defines a region when viewed in plan, and at least one temperature sensor associated with such heater zone is within the heater zone region. Located in the zone plane or spaced from this plane along the axis 643. Thus, the temperature sensor is near the heater zone. In one embodiment, each heater zone of plate 601 is substantially planar and extends substantially perpendicular to axis 643. It will be appreciated that all or some of the temperature sensors 651-653 can be so provided.

  The joining method according to some embodiments of the invention relies on controlling the wetting and flow of the joining material relative to the ceramic parts to be joined. In some embodiments, the absence of oxygen during bonding allows proper wetting without a reaction that changes the material in the bond area. With proper wetting and flow of the joining material, a hermetically sealed joint can be achieved at relatively low temperatures. In some embodiments of the invention, premetallization of the ceramic in the joint area is performed prior to the joining process.

  In some applications where a bonded ceramic end product is used, the strength of the bond may not be the primary design factor. In some applications, the tightness of the joint may be required so that the atmosphere on both sides of the joint can be separated. Also, the composition of the bonding material may be important so that the final product of the ceramic assembly is resistant to chemicals that may be exposed. Bonding materials may require resistance to chemicals, otherwise the chemicals can cause joint deterioration and loss of hermetic seal. The bonding material may also need to be of a type that does not interfere in a detrimental manner with processes that are subsequently supported by the finished ceramic mechanism.

  In some embodiments of the present invention, the bonded ceramic assembly is comprised of a ceramic such as aluminum nitride. Other materials such as alumina, silicon nitride, silicon carbide or beryllium oxide can be used. In some aspects, the first ceramic component can be aluminum nitride and the second ceramic component can be aluminum nitride, zirconia, alumina, or other ceramic. In some current processes, the components of the bonded ceramic assembly can be initially manufactured individually in an initial step with a processing oven in which the first and second parts are formed. In some embodiments, one of the mating parts may include a recess, allowing the other mating part to be present in the recess.

  In some embodiments, a plurality of standoffs adapted to maintain a minimum braze layer thickness can be included. In some embodiments, one of the ceramic parts, such as the shaft, utilizes a plurality of standoff mesas, for example, at the end of the shaft that is joined to the plate, or on the surface of the part that joins the cover to the plate. Can do. This mesa can be part of the same structure as the ceramic part and can be formed by scraping the structure from the ceramic part leaving the mesa. This mesa can abut the end of the ceramic part after the joining process. In some embodiments, this mesa can be utilized to provide a minimum braze layer thickness for the joint. In some embodiments, the brazing layer material prior to brazing can be thicker than the distance held by the mesa or powder particles between the shaft end and the plate. In some embodiments, another method can be used to set the minimum braze layer thickness. In some embodiments, ceramic spheres can be used to set the minimum braze layer thickness. In some aspects, since not all of the brazing material is extruded from between the standoff and the adjacent interface, the joint thickness is slightly thicker than another minimum thickness that determines the size or mechanism of the standoff. There is a case. In some embodiments, a portion of the aluminum brazing layer may be found between the standoff and the adjacent interface. In some embodiments, the brazing material can be 0.006 inches before brazing and the minimum thickness of the finished joint can be 0.004 inches. The brazing material can be aluminum containing 0.4 wt% Fe. In some embodiments, no standoff is utilized.

  When both types of atmosphere described above are seen on both sides across the joint of such a mechanism, the brazing material compatible with both types of atmosphere is aluminum. Aluminum has the property of forming a self-inhibiting layer of aluminum oxide. This layer is generally homogeneous and, once formed, prevents or severely restricts further oxygen or other oxidizing chemicals (such as fluorides) from entering the base aluminum and continuing the oxidation process. Thus, there is an initial short period of oxidation or corrosion of the aluminum and the oxide (or fluoride) layer formed on the aluminum surface substantially prevents or slows subsequent oxidation or corrosion. The brazing material can be in the form of a sheet, powder, thin film, or any other form factor suitable for the brazing process described herein. For example, the braze layer can be a sheet having a thickness in the range of 0.00019 inches to 0.011 inches or more. In some embodiments, the brazing material can be a sheet having a thickness of about 0.0012 inches. In some embodiments, the braze layer can be a sheet having a thickness of about 0.006 inches. Usually, alloy components (such as magnesium) in aluminum are formed as precipitates between the grain boundaries of aluminum. The alloying components reduce the oxidation resistance of the aluminum bonding layer, but usually these precipitates do not form a continuous passage through the aluminum and as a result do not allow the oxidant to penetrate the entire aluminum layer, and thus corrosion resistance. The characteristics of the self-inhibiting oxide layer of aluminum having the same are left as it is. In an embodiment using an aluminum alloy containing components capable of forming precipitates, process parameters including cooling procedures will be adapted to minimize precipitates in the grain boundaries. For example, in one embodiment, the brazing material can be aluminum having a purity of at least 99.5%. In some embodiments, it can have a purity greater than 92%. Commercially available aluminum foil can be used. In some embodiments, an alloy is used. These alloys can include Al-5 wt% Zr, Al-5 wt% Ti, and commercially available alloys # 7005, # 5083, and # 7075. These alloys can be used at a bonding temperature of 1100 ° C. in some embodiments. These alloys can be used at temperatures between 800 ° C. and 1200 ° C. in some embodiments. These alloys can be used at lower or higher temperatures in some embodiments.

  The difficulty of diffusing AlN aluminum under process conditions according to embodiments of the present invention results in the maintenance of ceramic material properties and material identity after the brazing step in the manufacture of plate and shaft assemblies.

  In some embodiments, the bonding process is performed in a processing chamber that is adapted to provide very low pressure. The joining process according to the embodiment of the present invention may require an oxygen-free state in order to obtain a hermetically sealed joint. In some embodiments, the bonding process is performed at a pressure of less than 1 × 10E-4 Torr. In some embodiments, the bonding process is performed at a pressure less than 1 × 10E-5 Torr. In some embodiments, further oxygen removal is achieved by placing zirconium or titanium in the processing chamber. For example, a zirconium inner chamber can be placed around the parts to be joined.

  In some embodiments, atmospheres other than vacuum can be used to achieve a hermetic seal. In some embodiments, an argon (Ar) atmosphere can be used to obtain an airtight junction. In some embodiments, another noble gas is used to obtain an airtight joint. In some embodiments, a hydrogen (H2) atmosphere can be used to obtain an airtight junction.

  Brazing layer wetting and flow may be sensitive to various factors. Important factors include brazing material composition, ceramic composition, chemical composition of the atmosphere in the processing chamber, especially the oxygen level in the chamber during the bonding process, temperature, time at temperature, brazing material thickness The surface properties of the materials to be joined, the shape of the parts to be joined, the physical pressure applied to the entire joint during the joining process, and / or the joint gap retained during the joining process.

  In some embodiments, the ceramic surface may be metallized prior to placing the ceramic component in the chamber for bonding. This metallization can be friction metallization in some embodiments. Friction metallization can include the use of aluminum rods. A rotary tool can be used to rotate the aluminum rod over the area that will be adjacent to the brazing layer when joining the parts. The friction metallization step can leave some aluminum on the ceramic component surface. The metallization step by friction can change the ceramic surface somewhat, such as by removing some oxide, so that the ceramic surface is well suited to brazing wetting. The metallization step can be thin film sputtering in some embodiments.

  An example of a brazing method for joining the first and second ceramic bodies includes a first brazing layer selected from the group consisting of aluminum and an aluminum alloy for joining the first ceramic body to the second ceramic body. And between the first and second ceramic bodies to bond the first and second ceramic bodies, heating the brazing layer to a temperature of at least 800 ° C., and curing the brazing layer to create a hermetic seal. Cooling the brazing layer to a temperature below its melting point. Various shapes of brazed joints can be performed according to the methods described herein.

  The joining process according to some embodiments of the present invention may include some or all of the following steps. Two or more ceramic parts are selected and joined. In some embodiments, multiple bonding layers can be used to bond multiple parts in the same set of processing steps, but for clarity of discussion, here a single bonding layer is bonded. Two ceramic parts are discussed. The ceramic component can be made of aluminum nitride. The ceramic component can be single crystal or polycrystalline aluminum nitride. Each part of each part is specified as an area of each part to be joined to the other. In an exemplary embodiment, a portion of the bottom of the ceramic plate structure will be joined to the top of the ceramic hollow cylindrical structure. The joining material can be an aluminum-containing brazing layer. In some embodiments, the braze layer can be a commercially available aluminum foil with an aluminum content greater than 99%. The brazing layer may consist of multiple layers of metal foil in some embodiments.

  In some embodiments, the specific surface regions that are to be joined will undergo a pre-metallization step. The premetallization step can be accomplished in various ways. One method uses a friction pre-metallization process using a material rod, which can be aluminum alloy 6061, which is rotated with a rotary tool to become ceramic in the joint area. So that some aluminum can be deposited in the joint area on each of the two ceramic parts. Alternatively, PVD, CVD, electroplating, plasma spraying, or other methods can be utilized to apply premetallization.

  In order to maintain some position control while in the processing chamber, the two parts can be relatively fixed prior to joining. In addition, this fixing is useful for applying an externally applied load, and generates a contact pressure across the joint between the two parts while the temperature is applied. A weight can be placed on top of the stationary part so that contact pressure is applied across the joint. The weight can be proportional to the area of the brazing layer. In some embodiments, the contact pressure applied across the junction can range from about 2-500 psi on the junction contact area. In some embodiments, the contact pressure can range from 2-40 psi. In some embodiments, minimal pressure can be used. The contact pressure used in this step is significantly lower than the contact pressure found in joining steps that utilize the high temperature pressing / sintering found in conventional processes, and conventional joining steps use pressures in the range of 2000-3000 psi. There is a case.

  In embodiments utilizing a mesa as a standoff or utilizing another method of controlling the joint thickness, such as a ceramic sphere, the original thickness of the brazing layer before application of heat may be greater than the height of the mesa. is there. When the brazing layer temperature reaches and exceeds the liquidus temperature, the pressure across the brazing layer between the parts to be joined is increased between the parts until the mesa on the first part contacts the interface on the second part. Will cause relative movement. At that point, the contact pressure across the joint will no longer be applied by external forces (except for the resistance against the repulsive force inside the brazing layer, if any). The mesa can prevent the brazing layer from being pushed out of the joint area before the ceramic parts are sufficiently wetted, thus allowing good and / or sufficient wetting during the bonding process. it can. In some embodiments, no mesa is utilized.

  The fixed assembly can be placed in a processing oven. The oven can be evacuated to a pressure of less than 5x10E-5 Torr. In some embodiments, the reduced pressure removes residual oxygen. In some embodiments, a vacuum of less than 1 × 10E-5 Torr is used. In some embodiments, the fixed assembly is placed inside a zirconium interior chamber that serves as an oxygen inducer to further reduce residual oxygen that may be directed to the joint during processing. In some embodiments, to remove oxygen, the processing oven is purged and refilled with a pure, dehydrated pure noble gas such as argon gas. In some embodiments, the processing oven is purged and refilled with purified hydrogen to remove oxygen.

  Next, the temperature of the fixed assembly is raised and maintained at the bonding temperature. Immediately after the start of the heating cycle, the temperature is slowly increased, for example to 15 ° C./min to 200 ° C. and then to a standardized temperature at 20 ° C./min, for example to a junction temperature of 600 ° C., to minimize the gradient In addition, and / or for another reason, it is possible to restore the degree of vacuum after heating by maintaining each temperature for a predetermined residence time. When the brazing temperature is reached, this temperature can be held for a time that results in a brazing reaction. In an exemplary embodiment, the residence temperature can be 800 ° C. and the residence time can be 2 hours. In another exemplary embodiment, the residence temperature can be 1000 ° C. and the residence time can be 15 minutes. In another exemplary embodiment, the residence temperature can be 1150 ° C. and the residence time can be 30-45 minutes. In some embodiments, the residence temperature does not exceed a maximum of 1200 ° C. In some embodiments, the residence temperature does not exceed a maximum of 1300 ° C. As soon as sufficient brazing residence time is reached, the furnace can be cooled to room temperature at a rate of 20 ° C. per minute or at a lower rate if the furnace specific cooling rate is good and small. The furnace can be opened to atmospheric pressure and the brazed assembly can be removed for inspection, characterization and / or evaluation.

  The use of excessively high temperatures for extended periods may lead to void formation in the bonding layer as a result of significant aluminum evaporation. Since voids are generated in the bonding layer, the airtightness of the bonding portion may be lost. The treatment temperature and its duration can be controlled so that the aluminum layer does not evaporate and to obtain an airtight joint. In addition to the other process parameters described above, continuous joints can be formed by appropriate temperature and process duration control. The continuous joint obtained by the embodiments described herein will provide a hermetic seal as well as a structural attachment of the part.

  The brazing material flows and allows wetting of the ceramic material surfaces to be joined. If an aluminum braze layer is used to join a ceramic such as aluminum nitride in the presence of a sufficiently low level of oxygen as described herein, the joint becomes a hermetic braze joint. This is in contrast to the diffusion bonding found in some conventional ceramic bonding processes.

  In some embodiments, the parts to be joined can be configured such that no pressure is applied across the braze layer during brazing. For example, the post or shaft can be placed into a countersink or recess in the mating part. The countersink can be larger than the external dimensions of the post or shaft. This can create a post or shaft area that can be subsequently filled with aluminum or an aluminum alloy. In this scenario, the pressure applied between the two parts to hold the two parts during joining does not cause any pressure across the braze layer. It is also possible to hold each component in a preferred end position using a fixture so that little or no pressure is applied between the components.

  The joint assembly joined as described above becomes a part having a hermetic seal between the joined parts. Therefore, such an assembly can be used in locations where isolation from the atmosphere is an important aspect for use of the assembly. Further, for example, some of the junctions that may be exposed to various atmospheres when the bonding assembly is later used in semiconductor processing are not degraded in such atmospheres, and subsequent semiconductors It does not contaminate the process.

  Both the airtight joint and the non-airtight joint can firmly join the parts in that a large force is required to separate the parts. However, the fact that the joint is strong does not determine whether the joint has an airtight seal. The ability to obtain a hermetic bond may be related to the wettability of the joint. Wettability refers to the ability or tendency of a liquid to spread to the surface of another material. If the brazed joint does not have sufficient wettability, there will be unjoined areas. If there are enough non-wetting regions, the gas may pass through the joint and cause a leak. Wettability may be affected by pressure across the joint at various stages of brazing material melting. To limit the compression of the braze layer beyond a certain minimum distance, the use of a mesa-type standoff or another standoff mechanism such as the insertion of a ceramic sphere or powder particle of the appropriate diameter The wettability can be improved. Careful control of the atmosphere experienced by the brazing element during the joining process can improve the wettability of the joint area. The combination of careful control of the joint thickness and careful control of the atmosphere used during processing can result in complete wettability of the joint interface that cannot be achieved with other processes. In addition, the use of a brazing layer of an appropriate thickness that can be thicker than the height of the mesa standoff, in combination with other related factors, provides a very well-wet and airtight joint. Can do. Although various bonding layer thicknesses may work well, increasing the bonding layer thickness can increase the success rate in terms of hermeticity at the joint.

  The presence of large amounts of oxygen or nitrogen during the brazing process can cause reactions that hinder sufficient wettability of the joint interface region, resulting in a joint that is not airtight. Without sufficient wettability, non-wetting regions are brought into the final joint in the joint interface region. If a sufficiently continuous non-wetting region is introduced, the tightness of the joint is lost.

  The presence of nitrogen can lead to the reaction of the nitrogen with molten aluminum to form aluminum nitride, and this reaction generation can interfere with the wettability of the interface region of the joint. Similarly, the presence of oxygen can lead to the reaction of aluminum with molten aluminum to form aluminum oxide, and this reaction generation can interfere with the wettability of the joint interface region. Use a vacuum atmosphere at a pressure of less than 5 × 10 −5 Torr to remove enough oxygen and nitrogen to allow a sufficiently tight joint interface area wettability and airtight joint. Indicated. In some embodiments, higher pressures, such as atmospheric pressure, are used in the processing chamber during the brazing step, but using non-oxidizing gases such as hydrogen or pure noble gases such as argon, the junction A solid wettability and airtight joint in the interface area was produced. In order to avoid the aforementioned oxygen reaction, the amount of oxygen present in the processing chamber during the brazing process must be sufficiently low so as not to adversely affect the sufficient wettability of the joint interface region. In order to avoid the aforementioned nitrogen reaction, the amount of nitrogen present in the processing chamber during the brazing process must be sufficiently low so as not to adversely affect the sufficient wettability of the joint interface region.

  Selection of an appropriate atmosphere during the brazing process can allow sufficient wettability of the joint, coupled with maintaining a minimum joint thickness. Conversely, the selection of an inappropriate atmosphere can lead to poor wettability and voids, resulting in a non-hermetic joint. In addition to the right material selection and the right temperature during brazing, the right combination of controlled atmosphere and controlled joint thickness allows the joining of materials with tight joints Become.

  In some embodiments of the invention where one or both of the ceramic surfaces are pre-metallized, such as by sputtering of an aluminum thin film prior to brazing, the bonding process step is performed at a lower temperature that is held for a shorter duration. Can be used. As soon as the heating cycle is started, the temperature is slowly increased, eg to 15 ° C./min to 200 ° C. and then to a standardized temperature, eg 600 ° C./joining temperature at 20 ° C./min to minimize the gradient. In addition, and / or for another reason, it is possible to restore the degree of vacuum after heating by maintaining each temperature for a predetermined residence time. When the brazing temperature is reached, this temperature can be held for a time that results in a brazing reaction. In some embodiments that utilize pre-metallization of one or more of the bonding interfaces, the brazing temperature can range from 600 ° C to 850 ° C. In an exemplary embodiment, the residence temperature can be 700 ° C. and the residence time can be 1 minute. In another exemplary embodiment, the residence temperature can be 750 ° C. and the residence time can be 1 minute. As soon as sufficient brazing residence time is reached, the furnace can be cooled to room temperature at a rate of 20 ° C. per minute or at a lower rate if the furnace specific cooling rate is good and small. The furnace can be opened to atmospheric pressure and the brazed assembly can be removed for inspection, characterization and / or evaluation.

  Compared with the aluminum brazing process where there is no aluminum layer deposition on the joint interface area, the process of depositing the aluminum thin film layer on the ceramic surface by thin film sputtering technology etc. is low temperature and very short residence time at the brazing temperature Over time will result in a tight joint. By utilizing an aluminum deposition layer on the interface, it is relatively easy to make the surface wettable, and a lower temperature and shorter residence time can be used to obtain an airtight joint. , Can require less energy.

  The outline of the process related to such brazing processing is as follows. The joint was between two parts of polycrystalline aluminum nitride. The braze layer material was 0.003 inch thick 99.8% aluminum foil. The joint interface area of the ring-shaped part was metallized using 2 μm thin film deposited aluminum. The bonding temperature was maintained at 780 ° C. for 10 minutes. Bonding was performed in a processing chamber maintained at a lower pressure of less than 6 × 10E-5 Torr. A junction thickness was maintained using a ZrO2 sphere having a diameter of 0.004 inches. The first part (ring-shaped part) was subjected to an etching process before depositing a thin layer of aluminum. The acoustic image of the joint integrity showed a dark single color where there was good wetting on the ceramic. Good and sufficient integrity of the joint was observed. This joint was airtight. Airtightness was confirmed by having a vacuum leak rate less than 1 × 10E-9 sccm He / sec (can be confirmed by a standard commercial mass spectrometer type helium leak detector).

  The manufacture of a multi-zone heater assembly with a heater zone thermocouple monitor, according to embodiments of the present invention, allows the thermocouple to be inserted after final sintering of the ceramic parts of the heater. Thermocouples are also exposed by hermetic seals that are configured to withstand substantial temperatures and corrosive gases from external environments that may contain corrosive gases that would be exposed to the heater during semiconductor processing. Protected. In addition, hermetic sealing is also a structural joint, and multiple part assemblies can be structurally connected and hermetically sealed in a single brazing step.

  Another advantage of the joining method described herein is that a joint made in accordance with some embodiments of the present invention can repair or replace one of the two parts if necessary. In addition, it is possible to disassemble components. Since the bonding process does not change the ceramic component by diffusion of the bonding layer into the ceramic, the ceramic component can be reused.

  In some embodiments, the alignment and position of the shaft and plate is maintained by the part shape, eliminating the fixing operation and post-joining machining. A weight can be used to ensure that the brazing material does not move during the joining process, except for some axial movement when the brazing material melts. The plate can be placed upside down and the joining element can be provided in a recess on the back side of the plate. The shaft can be inserted vertically downward into the recess of the plate. A weight can be placed on the shaft 401 to provide some contact pressure during the joining process.

  In some embodiments, the position / verticality of the shaft / plate is maintained by a fixture. Fixtures may not be precise due to thermal expansion and machining tolerances and may therefore require post-joining machining. The shaft diameter can be increased to accommodate the required material removal to meet the final dimensional requirements. Similarly, weights can be used to ensure that they do not move during the joining process, except for some axial movement as the brazing material melts. The plate can be placed upside down and the joining element can be provided on the upper back of the plate. The shaft can be placed on the plate to create a pre-assembly of the plate shaft. The fixture can be configured to support and position the shaft. The fixture can be keyed to the plate to provide positional integrity. A weight can be placed on the shaft 401 to provide some contact pressure during the joining process.

  One aspect of the present invention is the maximum working temperature of the joined shaft-plate, defined by the tensile strength that decreases with temperature, of the aluminum or aluminum alloy selected for joining. For example, when using pure aluminum as the bonding material, the structural strength of the bond between the shaft and the plate becomes much lower as the joint temperature approaches the melting point of aluminum, which is generally considered to be 660 ° C. As a practical matter, when using 99.5% or higher purity aluminum, the shaft-plate assembly can withstand all the usual expected stresses experienced with typical wafer processing tools up to a temperature of 600 ° C. become. However, some semiconductor device manufacturing processes require temperatures above 600 ° C.

  A repair procedure for separating assemblies joined according to an embodiment of the present invention may be performed as follows. The assembly can be placed in a processing oven using a fixture configured to provide a tensile force across the joint. The fixture can apply a tensile stress of about 2-30 psi onto the joint contact area. In some embodiments, the fixture can apply more stress across the joint. The secured assembly can then be placed in a processing oven. Although the oven can be evacuated. It may not be necessary during these steps. The temperature can be slowly increased, for example, up to 200 ° C. at 15 ° C. per minute, then to a standardized temperature at 20 ° C. per minute, for example up to 400 ° C., and to the separation temperature. As soon as the separation temperature is reached, the parts can fall apart. The separation temperature is specific to the material used for the brazing layer. In some embodiments, the separation temperature can be in the range of 600-800 ° C. In some embodiments, the separation temperature can be in the range of 800-1000 ° C. The fixture can be configured to limit the amount of movement between the two parts, so that the parts are not damaged during separation. The separation temperature can range from 450 ° C. to 660 ° C. for aluminum.

  Before reusing a previously used part, such as a ceramic shaft, the part can be pretreated for reuse by machining the joint area to remove the relief surface. In some embodiments, it may be desirable to remove all remaining brazing material in order to manage the total amount of brazing material at the joint when joining the part to a new mating part.

  In contrast to bonding methods that produce a diffusion layer within a ceramic, the bonding process according to some embodiments of the present invention does not result in such a diffusion layer. Thus, the material properties of the ceramic and brazing material maintain the material properties prior to the brazing step. Therefore, when it is desired to reuse the part after disassembly, the same material and the same material characteristics exist in the part, and the part can be reused with a known composition and characteristics.

  In one embodiment, a wafer chuck for use in a semiconductor manufacturing process is provided, the wafer chuck having a shaft having a predetermined axis and end, and joined to the end of the shaft and extending radially outward from the axis beyond the shaft. A plate having an extending portion; a temperature sensor disposed on a portion of the plate; and an electrical lead extending from the temperature sensor through the shaft to measure the plate temperature around the temperature sensor during the semiconductor manufacturing process. Can be included.

  The plate can be a ceramic plate. The wafer chuck further includes an additional temperature sensor disposed in a portion of the plate at a radial distance from a first temperature sensor (referred to as such) and a plate temperature around the additional temperature sensor. And an additional electrical lead extending through the shaft from the additional temperature sensor. The wafer chuck further includes a first heater for heating the plate around a first temperature sensor (referred to as such) and a second heater for heating the plate around an additional temperature sensor independent of the first heater. Can be included. The plate can be formed from at least a first plate layer and a second plate layer adjacent to and adjacent to the first plate layer, the first plate layer having a first surface, the second plate layer being First and second for forming a recess between the first and second plate layers having a second surface opposite the first surface and extending between the temperature sensor for receiving the electrical lead and the shaft. At least one of the surfaces has a recess inside. The recess may include a first passage that houses the first electrical lead and a second passage that houses the additional electrical lead. The recess can include a cylindrical cavity about the axis. The wafer chuck may further include a bonding layer disposed between the first plate and the second plate for hermetically bonding the plate layers. The temperature sensor can be a thermocouple.

  In one embodiment, a multi-zone heater is provided, the multi-zone heater can include a heater plate, the heater plate having a first radius and a first radius in a first radial distance area from its center. A first thermocouple hole in the directional distance zone; a first thermocouple in the first thermocouple hole; a second heater in a second radial distance zone that is farther from the center of the heater plate than the first radial distance zone; A second thermocouple hole in the second radial distance section, a second thermocouple in the second thermocouple hole, a passage between the heater plate and the cover, and a cover covering the passage; Two thermocouples have telemetry leads wired through this passage.

  The multi-zone heater can further include a hollow heater shaft attached to the heater plate, the hollow heater shaft including an inner surface and an outer surface. The second thermocouple hole can be located outside the region of the heater plate surrounded by the hollow heater shaft. The second thermocouple telemetry lead can be routed through the passage and into the hollow heater shaft. The cover can be hermetically bonded to the heater plate using the first bonding layer. The heater plate can include aluminum nitride. The hollow heater shaft can include aluminum nitride. The first bonding layer can include aluminum. The multi-zone heater may further include a second bonding layer disposed between the heater plate and the hollow heater shaft, and the second bonding layer hermetically seals the internal space of the shaft from the outside of the shaft. The second bonding layer can include aluminum.

  In one embodiment, a multi-zone heater is provided, the multi-zone heater may include a multi-layer heater plate, the multi-layer heater plate including an upper plate layer, one or more intermediate plate layers, and a lower plate. Layers, a plurality of plate bonding layers arranged between the plate layers to bond the plate layers, a plurality of heater element regions between two plate layers configured to be individually controlled, and mounted between the two plate layers A plurality of thermocouples.

  Each thermocouple can be arranged at a plurality of distances from the center of the multilayer heater plate. The multi-zone heater can further include a hollow heater shaft, which is attached to the bottom surface of the multilayer heater plate. The thermocouple can include a thermocouple lead, and the thermocouple lead can be routed through the interior of the hollow heater shaft. One or more thermocouples can be placed outside the area surrounded by the shaft attachment to the multilayer plate. The multi-zone heater can further include a bonding layer between the hollow heater shaft and the multilayer plate. The plurality of plate bonding layers can include aluminum. The joining layer between the hollow heater shaft and the multilayer plate can include aluminum. The top plate layer and the bottom plate layer can comprise ceramic. The hollow heater shaft can include aluminum. The plurality of plate bonding layers can include aluminum. The joining layer between the hollow heater shaft and the multilayer plate can include aluminum. The multi-zone heater can further include a central hub disposed between the hollow heater shaft and the multilayer plate.

  As is apparent from the above description, various embodiments can be constructed from the description herein, and it is easy for those skilled in the art to envision additional advantages and modifications. The invention in its broader aspects is therefore not limited to the specific details and illustrative embodiments shown and described. Accordingly, departures may be made from such details without departing from the spirit and scope of the applicant's general invention.

350 Mounting flange 500 Wafer chuck or heater 501 First plate layer or cover plate 502 Second plate layer or heater plate 503 Hollow region or passage 504 Central hole 505 First temperature sensor 506 Second temperature sensor 507 Third temperature sensor 508 First Thermocouple hole 509 second thermocouple hole 510 third thermocouple hole 516 shaft 517 first end 518 second end 519 longitudinal central axis 521 plate 522 part of plate 526 plate central zone 527 plate intermediate zone 528 Plate end zone 531 First electrical lead 532 Second electrical lead 533 Third electrical lead

Claims (14)

A wafer chuck for use in a semiconductor manufacturing process, comprising: a shaft having a shaft and an end; and a plate having a portion joined to the end of the shaft and extending radially outward from the shaft beyond the shaft. A plate having a recess extending at the portion ; a temperature sensor disposed at the portion of the plate; and from the temperature sensor to measure the temperature of the plate around the temperature sensor during a semiconductor manufacturing process. In a wafer chuck comprising the recess and an electrical lead extending through the shaft ,
The recess is hermetically sealed from corrosive processing gas by an aluminum joint made of aluminum brazing elements containing more than 92% by weight of aluminum, and the plate has a diffusion layer around the aluminum joint. do not do,
A wafer chuck characterized by that. The plate is a ceramic plate,
The wafer chuck according to claim 1. An additional temperature sensor disposed in a portion of the plate at a radial distance from the temperature sensor, and the shaft from the additional temperature sensor to measure the temperature of the plate around the additional temperature sensor An additional electrical lead extending through the
The wafer chuck according to claim 1. A first heater for heating the plate around the temperature sensor; and a second heater for heating the plate around the additional temperature sensor independent of the first heater. Yes,
The wafer chuck according to claim 3. The plate is formed of at least a first plate layer and a second plate layer hermetically bonded adjacent to the first plate layer, the first plate layer having a first surface, and the second plate The layer has a second surface opposite the first surface, and at least one of the first and second surfaces is between the temperature sensor and the shaft between the first and second plate layers. It has a recess inside that forms a recess that extends into the electrical lead.
The wafer chuck according to claim 3. The recess has a first passage that houses the electrical lead and a second passage that houses the additional electrical lead.
The wafer chuck according to claim 5. The recess includes a cylindrical cavity centered on the axis.
The wafer chuck according to claim 5. The aluminum joint is an aluminum joint formed from an aluminum brazing element heated to a temperature of at least 800 degrees Celsius;
The wafer chuck according to claim 1 . The temperature sensor is a thermocouple;
The wafer chuck according to claim 1. The plate is formed of at least a first plate layer and a second plate layer hermetically bonded adjacent to the first plate layer;
The first plate layer has a first surface, the second plate layer has a second surface facing the first surface, and at least one of the first surface and the second surface is the electrical lead wire. Having a recess that forms a recess extending in the portion between the first plate layer and the second plate layer,
The wafer chuck according to claim 1. Each of the first surface and the second surface has a recess therein, and the first plate layer and the second plate within the portion so that the recess can accommodate the electrical lead. Facing each other to form a recess extending between the layers,
The wafer chuck according to claim 10. The portion of the plate has a lower surface and an elongate cover plate that extends radially outward from the shaft and covers the lower surface, and the recess is adapted to receive the electrical lead. Formed on at least one of a side surface and a cover plate, the cover plate being hermetically sealed from the corrosive process gas to the lower surface by the aluminum joint,
The wafer chuck according to claim 1. The portion of the plate has a flat surface and a long hole extending radially outward from the shaft in the flat surface, and a part of the long hole is the lower surface.
The wafer chuck according to claim 12. The portion of the plate has a flat surface and a portion of the flat surface is the lower surface;
The wafer chuck according to claim 12.

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