Abstract:
A method and apparatus for heating or cooling a fluid is provided. In one embodiment, a heat exchanger is provided. The heat exchanger includes a first subassembly comprising an insert. The insert comprises a body having a blind passage formed axially in the body, a plurality of nozzles formed therein, and a first plurality of heat exchange elements disposed within the body. The heat exchanger also comprises a second subassembly comprising a sleeve and a second plurality of heat exchange elements disposed within the sleeve, wherein the insert is sealably engaged inside the sleeve and the insert and the sleeve cooperatively define a thin gap, and wherein each of the plurality of nozzles are disposed radially between the blind passage and the thin gap.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/122,616, filed May 16, 2008, which application is hereby incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     Embodiments of the invention relate generally to semiconductor processing, and more particularly to an apparatus for treating a substrate. 
     Description of the Related Art 
     Semiconductor manufacturing processes rely heavily on chemical reactions to build devices on substrates. These chemical reactions are often sustained in processing chambers in which vapor species are brought into contact with substrates to be processed. Chemical species are provided as vapors to control reaction rate, duration, and uniformity across the substrate, and are sometimes ionized to varying extents to promote reactions. 
     The vapor species may be produced from liquids or solids contained in vessels connected to the processing chambers by piping. The precursor species are generally heated to vaporize them. In some embodiments, the heat is applied directly to the precursor species, while in others a carrier gas is heated and contacted with the precursors to heat and vaporize them. In any event, heat must be applied, and the precursors must be maintained in the vapor state while traveling to the processing chamber. 
     In-line heaters of various designs have commonly been used to heat gases for semiconductor processing. Recently, as devices formed on semiconductor substrates have continued to become smaller, all facets of semiconductor manufacture are forced to reduce dimensions. Thus, there is a continuing need for process elements, such as heat exchangers, useable for the next generation of semiconductor manufacturing processes. 
     SUMMARY OF THE INVENTION 
     Embodiments of the invention provide a heat exchanger, including a first subassembly comprising an insert. The insert comprises a body having a blind passage formed axially in the body, a plurality of nozzles formed therein, and a first plurality of heat exchange elements disposed within the body. The heat exchanger also includes a second subassembly comprising a sleeve and a second plurality of heat exchange elements disposed within the sleeve, wherein the insert is sealably engaged inside the sleeve and the insert and the sleeve cooperatively define a thin gap, and wherein each of the plurality of nozzles are disposed radially between the blind passage and the thin gap. 
     Embodiments of the invention also provide a heat exchanger, comprising an inlet conduit coupled to a body. The body comprises a first portion having a central blind passage, a plurality of nozzles extending radially from the central blind passage, and a first plurality of thermal elements disposed therein, wherein the plurality of nozzles are in fluid communication with the inlet conduit and the central blind passage. The body also comprises a second portion configured as a sleeve to at least partially surround and mate sealably with the first portion, wherein the first portion and the second portion cooperatively defines a distribution channel and a thin gap, the second portion having a second plurality of thermal elements disposed therein, wherein the distribution channel and the thin gap are in fluid communication with the plurality of nozzles. The heat exchanger also comprises an outlet conduit coupled to the body and in fluid communication with the thin gap. 
     Further embodiments of the invention provide a heat exchanger, comprising an inlet conduit coupled to a body. The body comprises a first cylindrical portion having a central blind passage, a plurality of nozzles extending radially from the central blind passage, and a first plurality of thermal elements disposed therein, wherein the plurality of nozzles are in fluid communication with the inlet conduit and the central blind passage. The body also comprises a second cylindrical portion configured as a sleeve to at least partially surround and mate sealably with the first cylindrical portion, wherein the first cylindrical portion and the second cylindrical portion cooperatively defines a distribution channel and a thin gap, the second cylindrical portion having a second plurality of thermal elements disposed therein, wherein the distribution channel and the thin gap are in fluid communication with the plurality of nozzles. The heat exchanger also comprises an outlet conduit coupled to the body and in fluid communication with the thin gap. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above-recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1  is a perspective view of an apparatus according to one embodiment of the invention. 
         FIG. 2  is a cross-sectional view of the apparatus of  FIG. 1 . 
         FIG. 3  is an expanded cross-sectional view of the apparatus of  FIG. 1 . 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation. 
     DETAILED DESCRIPTION 
     The invention generally provides an apparatus for thermal control of a fluid in a semiconductor manufacturing process. The fluid may be liquid or vapor. 
       FIG. 1  is an isometric view of an apparatus  100  according to one embodiment of the invention. The apparatus  100  comprises a first portion  102  and a second portion  104  that fit together at joint  106 . An inlet conduit  108  is coupled to a surface (not visible in  FIG. 1 ) of the first portion  102 , and an outlet conduit  110  is correspondingly coupled to a surface  114  of the second portion  104 . Thermal elements  112  are disposed in the second portion  104 , as is a temperature sensor  116 . A controller  118  is also coupled to the second portion  104 . 
       FIG. 2  is a cross-sectional view of the apparatus  100  of  FIG. 1 . The inlet conduit  108  couples to the surface  202  of the first portion  102 , and registers with a passage  204  formed in the first portion  102 . The coupling of the inlet conduit  108  to the surface  202  of the first portion  102 , and the passage  204 , are shown substantially centered along an axis of the apparatus  100 , but alternate embodiments may position these elements at any convenient location away from the central axis. In other embodiments, multiple inlet conduits may be spaced across the surface  202 . 
     A plurality of nozzles  206  connects the passage  204  formed within the first portion  102  to a channel  208  around the periphery of the first portion. The nozzles  206  may be substantially perpendicular to the passage  204 , or they may form an angle with the passage  204 . The nozzles  206  place the channel  208  into fluid communication with the passage  204  and the inlet conduit  108 . The passage  204  may extend beyond the point at which the nozzles  206  contact the passage  204  in some embodiments. In other embodiments, the passage  204  may end at the nozzle attachment point. The nozzles  206  may be formed with the same diameter as the passage  204  within the first portion  102 . In some embodiments, the diameter of the nozzles  206  will be constant from the point at which they contact the passage  204  to the point at which they contact the channel  208 . In other embodiments, the diameter of the nozzles  206  may change along their length. It is preferable that all nozzles  206  have the same diameter profile along their length to avoid flow imbalances within the apparatus. In some embodiments, a first diameter of each nozzle  206  at the channel  208  will be smaller than a second diameter at the passage  204 . In other embodiments, the first diameter will be larger than the second diameter. The plurality of nozzles  206  may comprise any convenient number of nozzles. The embodiment illustrated in  FIGS. 1 and 2  has three nozzles, as suggested by  FIG. 2 , but designs having more than three, or less than three, nozzles are conceivable. 
     In embodiments featuring multiple inlet conduits, as described above, the conduits may register with one or more common passages, such as the passage  204  of  FIG. 2 , or each inlet conduit may have a dedicated passage to the channel  208 . For example, three inlet conduits may be spaced evenly across the surface  202  of the first portion  102 , each registering with one of the three nozzles  206  of the  FIG. 2  embodiment. Embodiments of this kind may also be constructed having more than three or less than three pathways. 
     The first portion  102  is configured to mate sealably with the second portion  104  at joint  106 . A seal is formed at joint  106  by virtue of a sealing member  210  disposed in an opening  212  cooperatively defined by complimentary recesses formed in the sealing surfaces of the first portion  102  and the second portion  104 . In some embodiments, the sealing member may comprise a compliant material able to form a seal under compression, such as any suitable variety of rubber. The first and second portions have thermal surfaces  214  and  216 , respectively, which together define the channel  208  and a thin gap  218 . The thin gap  218  is preferably less than about 0.1 inches in width, more preferably less than about 0.05 inches, such as about 0.025 inches. The thin gap  218  between the thermal surfaces  214  and  216  results in excellent heat exchange with a fluid flowing through the thin gap  218 . In embodiments wherein the first portion  102  and the second portion  104  are generally cylindrical in shape, the thin gap  218  may be annular in shape. Fluid flow through the thin gap  218  may be laminar or turbulent, with similar thermal exchange results. 
       FIG. 3  is an expanded view of the apparatus of  FIGS. 1 and 2 , showing the first portion  102  of the apparatus  100  and the second portion  104  spaced apart for illustration purposes. In some embodiments, the first portion  102  has a recess  302  formed proximate the sealing surface  304  of the first portion  102 . The recess  302 , together with the thermal surface  216  of the second portion  104 , defines the channel  208  shown in  FIG. 2 . The channel  208  is in fluid communication with the thin gap  218  and the plurality of nozzles  206  formed in the first portion  102 . Fluid flowing through the plurality of nozzles  206  from the inlet conduit  108  flows around the channel  208 , distributing evenly before flowing into the thin gap  218 . The recess  302  has a floor  306  adjacent to the sealing surface  304  and a wall  308 . In this embodiment the wall  308  has a sloped profile, but in alternate embodiments the wall  308  may be substantially perpendicular to the floor  306 , or it may have a curved profile with a convex or concave shape. The shape of the wall  308  influences how fluid flows from the channel  208  into the thin gap  218 . 
     The first portion  102  has a notch  310  at an edge of a flange  312 , the flange  312  comprising the sealing surface  304 . In some embodiments, the notch  310  may be an alignment notch. The notch  310  mates with a rim  314  on the second portion  104 . The notch  310  and rim  314  are shown in this embodiment with a generally rectangular profile, but both may be formed with any convenient profile, so long as they are complimentary. In some embodiments, the notch  310  and rim  314  facilitate alignment of the first portion  102  with the second portion  104  to ensure consistent dimension of the thin gap  218 . 
     Each of the plurality of nozzles  206  provides a pathway connecting the passage  204  in the first portion  102  with the channel  208 . In some embodiments, the nozzles  206  may be distribution nozzles. The nozzles  206  in the embodiment of  FIG. 3  have a constant diameter that is less than the width of the recess  302 , but in alternate embodiments the nozzles may have different dimensions. For example, the nozzles may have a varying diameter that decreases from the passage  204  to the channel  208 , or the diameter may increase from the passage  204  to the channel  208 . In another embodiment, the nozzles  206  may have tapered openings leading into the channel  208 . In most embodiments, the plurality of nozzles  206  will be spaced evenly about the passage  204 . In an embodiment with three nozzles  206 , each nozzle will preferably form an angle of 120° with the other two nozzles. In an embodiment with four nozzles, the preferred angle will be 90°. 
     As shown in  FIG. 3 , the first portion  102  further comprises one or more thermal elements  316  for generating an energy flux through the apparatus. The thermal elements are generally housed in one or more receptacles  318  formed in the first portion  102 . In some embodiments, the thermal elements  316  may be heaters, while in other embodiments they may be coolers. In some embodiments, the thermal elements  316  may be resistive heating elements, and in other embodiments the thermal elements  316  may be electrical heating elements. In other embodiments, the thermal elements may be configured to provide a hot or cold fluid to drive heat flux. In some embodiments, the thermal elements  316  may be thermal inserts. A plurality of thermal elements  316  is generally provided in most embodiments to facilitate uniform and rapid heat flux, but embodiments comprising one thermal element  316  in the first portion  102  are conceivable. In embodiments featuring a plurality of thermal elements  316 , the thermal elements  316  will generally be spaced equally throughout the first portion  102 . For example, in the embodiment shown in  FIGS. 1 through 3 , the first portion  102  comprises three thermal elements  316  housed in three receptacles  318 . The thermal elements of the  FIG. 3  embodiment are spaced evenly through the first portion  102  in a pattern similar to the spacing of the nozzles  206 . In the  FIG. 3  embodiment, each thermal element  316  is located opposite a nozzle  206 . The thermal elements  316  are located near the thermal surface  214  of the first portion  102 . The distance between a surface of the thermal elements  316  closest to the thermal surface  214  is selected to provide structural integrity, vigorous thermal exchange, and substantial thermal spreading along the thermal surface  214 . More distance between the thermal elements  316  and the thermal surface  214  promotes structural integrity and spreading of heat at the expense of heat exchange, with more heat held inside the first portion  102 . Less distance localizes and speeds heat exchange, but risks failure of the thermal surface  214 . 
     The thermal elements  316  of the embodiment of  FIGS. 1-3  are rod-like, cylindrical in shape with rectangular profile, but they may be any convenient shape so long as they make intimate contact with the bulk of the first portion  102  when inserted into receptacles  318 . Shape profiles such as square, rectangular, triangular, polygonal, oval, frustoconical, or starburst may be useful in some embodiments. The thermal elements  316  of  FIGS. 1-3  also exhibit conical ends, but may also be flat, beveled, rounded, hemispherical, and the like. Moreover, the first portion  102 , as shown in  FIG. 3 , exhibits a generally rectangular profile, and is generally cylindrical in shape, with a beveled edge portion  320 . The beveled edge portion  320  facilitates fluid flow through the thin gap  218  to achieve the desired throughput. The bulk of the first portion  102 , may, however, have any convenient shape. Instead of being cylindrical, it may be rectangular, triangular, polygonal, frustoconical, or starburst-like in shape. The edge portion  320  may likewise be rounded or hemispherical in profile. A rounded or curved profile may further promote smooth fluid flow through the thin gap  218 . The second portion  104  will preferably have a complimentary shape to the first portion  102  to preserve the dimension of the thin gap  218 . 
     Referring again to  FIG. 3 , in some embodiments the second portion  104  is a sleeve into which the first portion  102  is inserted. In some embodiments the second portion  102  also has thermal elements  316 . The thermal elements  316  of the second portion  102  are generally shaped to follow the contours of the thermal surface  216 . In the embodiment of  FIG. 3 , the thermal elements  316  of the second portion  104  are also rod-like and cylindrical in shape, with a rectangular profile and conical end. These thermal elements may likewise be any convenient shape, and may be resistive or electrical heaters, or fluid heat exchange elements, such as those described above. Depending on the needs of particular embodiments, the thermal elements  112  of the second portion  104  may be larger or smaller than those of the first portion  102 . In most embodiments, the thermal elements  112  of the second portion  104  will be aligned with, and equidistant from, the thermal elements  112  of the first portion  102 . If the thermal elements  112  of the first portion  102  are equidistant from the nozzles  206 , the thermal elements  112  of the second portion  104  may be aligned with the nozzles  206 , as shown in  FIG. 2 . 
     In some embodiments, a temperature sensor  116  may be provided, as described above in reference to  FIG. 1 . The temperature sensor  116  may be a thermocouple, resistance thermometer, diode bandgap sensor, thermistor, electron tunneling sensor, or any other convenient device for sensing temperature. In most embodiments, the temperature sensor  116  will be disposed to register the temperature of the fluid passing through the thin gap  218 . In some embodiments, the temperature sensor may be disposed in a receptacle (not shown) formed in the second portion  104 . A receptacle similar to the receptacles  318  may be used to house the temperature sensor  116 , if the temperature sensor  116  has a rod-like shape. Other types of temperature sensors  116  may be embedded in the second portion  104  near the thermal surface  216 . A temperature sensor  116  embedded in the thermal surface  216  will preferably be located near the junction between the thin gap  218  and the outlet conduit  110  to measure the full temperature change of the fluid in the device. 
     Some embodiments of the invention will provide a controller  118 . In the embodiment of  FIGS. 1-3 , the controller  118  is attached to the second portion  104  of the apparatus  100 . The controller  118  may be electrical for controlling electrical thermal elements, or it may control a valve by electrical or pneumatic means for thermal elements incorporating a heat exchange fluid or medium. In the embodiment of  FIGS. 1-3 , the controller  118  is an over-temperature controller that reduces or shuts off power to the thermal elements  316  if the temperature of the fluid in the thin gap  218  reaches a specified temperature above the target temperature. A controller such as the controller  118  may also be used to increase or reduce thermal flux of the thermal elements  316  in response to a measured temperature compared with a target temperature. The controller  118  may be an analog controller, such as a switch activated by an electrical signal from the temperature sensor, or a digital controller under the direction of a computer program. In some embodiments, the controller may also be remotely located, depending on specific needs. 
     Embodiments of the invention may be configured to heat a gas such as nitrogen flowing at 10 standard liters per minute from room temperature of about 25° C. to about 200° C. using 3 electrical heater rods, each 0.125 inches in diameter and 2 inches long, and 3 electrical heater rods, each 0.125 inches in diameter and 1.5 inches long. Application of about 40 Watts of electrical power to each heater rod, and flowing the gas through a thin gap pathway about 1 inch long at the flow rate specified above achieves an exit temperature of 200° C. For such a heater, the first portion or insert, the second portion or sleeve, and the heater rods may all be made of a metal such as stainless steel or aluminum. 
     A longer pathway allows heating to a higher temperature, or at higher throughput. The heater above extended to a 2 inch thin gap pathway will heat 20 SLM to 200° C., or 10 SLM to 250° C. Multiple such heaters may be used in series to boost the temperature of a gas by stages. At higher temperatures, materials capable of retaining their shape and thermal conductivity as temperatures rise are preferred. In some embodiments, alloys such as Inconel may be useful. At higher temperatures, insulation may be applied around the apparatus and secured with an enclosure to prevent unnecessary heat loss. Finally, increased roughness of the thermal surfaces  214  and  216  may aid in heat transfer by increasing contact area for heat exchange. 
     In operation, the device described above embodies a method of changing the thermal state of a fluid. The fluid is introduced to a device configured to force the fluid into intimate contact with one or more thermal agents. The thermal agents generate heat flux with respect to the fluid, changing its thermal state and, in some embodiments, its temperature. 
     In a preferred embodiment, the fluid may be forced to follow a sheet-like path through a thin gap. Forcing the fluid through a thin gap increases the surface area of thermal contact for the fluid volume, speeding up thermal exchange. In some embodiments, the gap may be engineered to assume a convenient shape, such as that of an annulus or rectangular annulus, and the pathway may incorporate folding or reversals. 
     The fluid may be exposed to thermal agents to generate heat flux into or out of the fluid. The thermal agents may be point or line agents, or may be distributed sources such as plane agents. The thermal agents may be heat sources or sinks, and may have uniform thermal capacity or varying thermal capacity. For example, in one embodiment multiple line sources of heat may be placed in close proximity to a sheet-like stream of fluid flowing through a thin gap to heat the fluid. The line sources may be oriented along the path of flow or perpendicular to the path of flow, and may be uniformly or non-uniformly spaced. For example, line sources may be concentrated near an upstream portion of the thin gap path. The thermal agents may be electrical in nature or may incorporate a hot or cold medium for generating heat flux. 
     The thermal state of the fluid flowing through the thin gap may be controlled by providing a sensor and a controller. The sensor may be a thermocouple or any other suitable device. The controller may be an analog controller, such as a switch configured to interrupt the thermal flux generated by the thermal agents when signaled by the sensor, or it may be a digital controller under the direction of a computer program. 
     While the foregoing is directed to embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.