Abstract:
A shielded lid heater lid heater suitable for use with a plasma processing chamber, a plasma processing chamber having a shielded lid heater and a method for plasma processing are provided. The method and apparatus enhances positional control of plasma location within a plasma processing chamber, and may be utilized in etch, deposition, implant, and thermal processing systems, among other applications where the control of plasma location is desirable. In one embodiment, a shielded lid heater is provided that includes an aluminum base and RF shield sandwiching a heater element.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims benefit of U.S. Provisional Application Ser. No. 61/038,510 filed Mar. 21, 2008 (Attorney Docket No. APPM/12624), which is incorporated by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    Embodiments of the present invention generally relate to semiconductor substrate processing systems. More specifically, the invention relates to a shielded lid heater assembly for a plasma processing system. 
         [0004]    2. Background 
         [0005]    In manufacture of integrated circuits, precise control of various process parameters is required for achieving consistent results within a substrate, as well as the results that are reproducible from substrate to substrate. As the geometry limits of the structures for forming semiconductor devices are pushed against technology limits, tighter tolerances and precise process control are critical to fabrication success. However, with shrinking geometries, precise critical dimension and etch process control has become increasingly difficult. 
         [0006]    Many semiconductor devices are processed in the presence of a plasma. If the plasma is not uniformly positioned over the substrate, processing results may also by non-uniform. 
         [0007]    Although conventional plasma processing chambers have proven to be robust performers at larger critical dimensions, existing techniques for controlling the plasma uniformity are one area where improvement in plasma uniformity will contribute to the successful fabrication of next generation, submicron structures, such as those having critical dimensions of about 55 nm and beyond. 
         [0008]    The inventors have discovered that improvements to the design of heaters utilized to control the temperature of a lid of the processing chamber have a beneficial effect on plasma uniformity. 
       SUMMARY 
       [0009]    Embodiments of the invention generally provide a shielded lid heater. Other embodiments provide a method and apparatus for controlling the lid temperature of a plasma processing chamber. The method and apparatus enhances positional control of plasma location within a plasma processing chamber, and may be utilized in etch, deposition, implant, and thermal processing systems, among other applications where the control of plasma location is desirable. 
         [0010]    In one embodiment, a shielded lid heater is provided that includes an aluminum base and RF shield sandwiching a heater element. A thermal insulator is disposed on the RF shield. 
         [0011]    In another embodiment, a shielded lid heater is provided that includes an aluminum base, an RF shield and a heater element. The base has a channel formed therein which accommodates heater element. The RF shield covers the channel to enclose the heater element. 
         [0012]    In another embodiment, a shielded lid heater includes an inductor coil coupled thereto. The inductor coil may optionally be a variable inductor, thereby enabling the inductance to be tuned to position a plasma with in a processing chamber. 
         [0013]    In another embodiment, a plasma processing chamber is provided that includes a chamber body enclosed by a lid, a substrate support disposed in the chamber body, coils positioned adjacent the lid for coupling RF power to gases within the chamber body; and a shielded lid heater coupled to the lid. The lid heater includes an aluminum base and RF shield sandwiching a heater element. Optionally the lid heater may include an inductor coil. 
         [0014]    In yet another embodiment, a process for turning a plasma processing chamber is provided that include determining a position of a plasma within the processing chamber, selecting an inductance and/or position of an inductor coil coupled to a lid heater that shifts the plasma location from the determined position to a target position, and plasma processing a substrate with the inductor coil having the selected inductance and/or position. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0015]    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. 
           [0016]      FIG. 1  is a schematic diagram of an exemplary semiconductor substrate processing apparatus comprising a shielded lid heater in accordance with one embodiment of the invention; 
           [0017]      FIGS. 2A-B  are a schematic cross-sectional views of two embodiments of a shielded lid heater; 
           [0018]      FIG. 3  is an isometric view of one embodiment of the shielded lid heater of  FIG. 1 ; 
           [0019]      FIG. 4  is a top view of one embodiment of the shielded lid heater of  FIG. 1 ; 
           [0020]      FIG. 5  is a partial front side view of one embodiments of a shielded lid heater; 
           [0021]      FIG. 6  is a partial back side view of one embodiments of a shielded lid heater; 
           [0022]      FIG. 7  is a partial side view of another embodiment of a shielded lid heater; and 
           [0023]      FIG. 8  is a flow diagram of one embodiment of a method for plasma processing a substrate. 
       
    
    
       [0024]    To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is also contemplated that elements and features of one embodiment may be beneficially incorporated on other embodiments without further recitation. 
       DETAILED DESCRIPTION  
       [0025]      FIG. 1  depicts a schematic diagram of an exemplary plasma processing chamber  100  having one embodiment of a shielded lid heater  180  of the present invention. The particular embodiment of the plasma processing chamber  100  is shown in  FIG. 1  as an etch reactor, but is contemplated that the shielded lid heater  180  may beneficially be utilized in other types of plasma processing chambers, including chemical vapor deposition chambers, physical vapor deposition chambers, implantation chambers, nitriding chambers, plasma annealing chambers, plasma treatment chambers, and ashing chambers, among others. Thus, the embodiment of plasma processing chamber of  FIG. 1  is provided for illustrative purposes and should not be used to limit the scope of the invention. 
         [0026]    Processing chamber  100  generally includes a chamber body  110 , a gas panel  138  and a controller  140 . The chamber body  110  includes a bottom  128 , sidewalls  130  and a lid  120  that enclose a process volume. The sidewalls  130  and bottom  128  are fabricated from a conductive material, such as stainless steel or aluminum. The lid  120  may be fabricated from aluminum, stainless steel, ceramic or other suitable material. 
         [0027]    Process gasses from the gas panel  138  are provided to the process volume of the chamber body  110  through a showerhead or one or more nozzles  136 . In the embodiment depicted in  FIG. 1 , the processing chamber  100  includes a plurality of nozzles  136  positioned along the sidewalls  130  of the chamber body and a nozzle  136  centrally mounted below the lid  120 . The nozzle  136  mounted in the center of the lid  120  may include independently controllable radial and down-facing gas outlet ports. 
         [0028]    The controller  140  includes a central processing unit (CPU)  144 , a memory  142 , and support circuits  146 . The controller  140  is coupled to and controls components of the processing chamber  100 , processes performed in the chamber body  110 , as well as may facilitate an optional data exchange with databases of an integrated circuit fab. 
         [0029]    In the depicted embodiment, the lid  120  is a substantially flat ceramic member. Other embodiments of the process chamber  100  may have other types of ceilings, e.g., a dome-shaped ceiling. Above the lid  120  is disposed an antenna  112  comprising one or more inductor coil elements (two co-axial coil elements are illustratively shown). The antenna  112  is coupled, through a first matching network  170 , to a radio-frequency (RF) plasma power source  118 . During plasma processing, the antenna  112  is energized with RF power provided by the power source  118  to maintain a plasma  106  formed from the process gasses within in the internal volume of the chamber body  110 . 
         [0030]    In one embodiment, the substrate pedestal assembly  116  includes a mount assembly  162 , a base assembly  114  and an electrostatic chuck  188 . The mount assembly  162  couples the base assembly  114  to the bottom  128  of the chamber body  110 . 
         [0031]    The electrostatic chuck  188  is generally formed from ceramic or similar dielectric material and comprises at least one clamping electrode  186  controlled using a power supply  128 . In a further embodiment, the electrostatic chuck  188  may comprise at least one RF electrode (not shown) coupled, through a second matching network  124 , to a power source  122  of substrate bias. The electrostatic chuck  188  may optionally comprise one or more substrate heaters. In one embodiment, two concentric and independently controllable resistive heaters, shown as concentric heaters  184 A,  184 B, are utilized to control the edge to center temperature profile of the substrate  150 . 
         [0032]    The electrostatic chuck  188  may further comprise a plurality of gas passages (not shown), such as grooves, that are formed in the substrate supporting surface of the chuck and fluidly coupled to a source  148  of a heat transfer (or backside) gas. In operation, the backside gas (e.g., helium (He)) is provided at controlled pressure into the gas passages to enhance the heat transfer between the electrostatic chuck  188  and the substrate  150 . Conventionally, at least the substrate supporting surface of the electrostatic chuck is provided with a coating resistant to the chemistries and temperatures used during processing the substrates. 
         [0033]    The base assembly  114  is generally formed from aluminum or other metallic material. The base assembly  114  includes one or more cooling passages that are coupled to a source  182  of a heating or cooling liquid. A heat transfer fluid, which may be at least one gas such as Freon, Helium or Nitrogen, among others, or a liquid such as water or oil, among others, is provided by the source  182  through the passages to control the temperature of the base assembly  114 , thereby heating or cooling the base assembly  114 , thereby controlling, in part, the temperature of a substrate  150  disposed on the base assembly  114  during processing. 
         [0034]    Temperature of the pedestal assembly  116 , and hence the substrate  150 , is monitored using a plurality of sensors (not shown in  FIG. 1 ). Routing of the sensors through the pedestal assembly  116  is further described below. The temperature sensors, such as a fiber optic temperature sensor, are coupled to the controller  140  to provide a metric indicative of the temperature profile of the pedestal assembly  116 . 
         [0035]    Temperature of the lid  120  is controlled by the shielded lid heater  180 . In one embodiment, the shielded lid heater  180  is a resistive heater energized by a power source  178 . In embodiments wherein the lid  120  is fabricated from a ceramic material, the shielded lid heater  180  may be adhered or clamped to the exterior surface of the lid  120 . 
         [0036]      FIG. 2A  is a partial cross-sectional view of one embodiment of the shielded lid heater  180  disposed on the lid  120 . The shielded lid heater  180  generally includes a conductive base  202 , a heater element  204  and an RF shield  206 . The heater element  204  is sandwiched between the conductive base  202  and the RF shield  206 . The heater element  204  generally includes a resistive element  212  embedded in an electrical insulator  210 . The RF shield  206  substantially prevents the resistive element  212  from influencing the orientation of the magnetic and electrical field lines generated by the antenna  112  passing through the lid  220  so that the plasma  106  may be more accurately positioned within the interior volume of the chamber body  110 . 
         [0037]    The conductive base  202  generally has sufficient mass to provide uniform heat transfer between the heater element  204  and the lid  120 . In one embodiment, the conductive base  202  is fabricated from a metallic material having good heat transfer characteristics, such as aluminum and the like. The conductive base  202  may have a geometric form suitable to provide a desired heat distribution to the lid  220 . 
         [0038]    The RF shield  206  is generally fabricated from a metallic material such as aluminum. The RF shield  206  may be aluminum foil or plate. In one embodiment, the RF shield  206  has the same plan form as the conductive base  202 . 
         [0039]    Optionally, a thermal insulator  208  may be disposed on the RF shield  206 . The thermal insulator  208  is generally fabricated from a material which has little influence on the RF magnetic and electrical fields, such as a high temperature elastomer, such as a silicone or other high temperature foam. The thermal insulator  208  provides protection from burns that may be received if the lid heater  180  is inadvertently touched while at a high temperature. 
         [0040]    The conductive base  202 , heater element  204  and RF shield  206  may be secured using fasteners, clamped together or held by a suitable adhesive. In one embodiment, the components of the shielded lid heater  180  are secured together utilizing a high temperature epoxy. 
         [0041]      FIG. 2B  is a schematic cross-sectional view of another embodiment of a shielded lid heater  280  which may be utilized in the chamber  100 . The shielded lid heater  280  generally includes a conductive base  282 , a heater element  284  and a RF shield  206 . An optional thermal insulator  208  may be disposed on the RF shield  206 . The heater element  284  is configured as described above with reference to the heating element  204  of  FIG. 2A . The conductive base  282  is substantially similar to the conductive base  202  described above, with the addition of a channel  286  formed in a top surface  290 . The channel  286  is sized to accommodate the heater element  284 . The sidewalls  288  of the channel  286  have a height sufficient such that the heater element  284  is enclosed within the channel  286  when the RF shield  206  is disposed on the top surface  290  of the conductive base  282 . 
         [0042]      FIG. 3  depicts an isometric view of the shielded lid heater  280 . The shielded lid heater  280  generally includes a first section  302  and a second section  304 . Each section comprises an annular member  300  and a plurality of fingers  308 ,  318 . The fingers  308 ,  318  extend radially inward from the annular member  300 . The annular members  300  of the sections  302 ,  304  have the same radial dimension, such that when coupled together, the sections  302 ,  304  form a generally circular plan form. The fingers  318  are generally shorter than the fingers  308  and are interweaved between adjacent fingers  308  to form a spoke-like pattern. 
         [0043]    The first and second sections  302 ,  304  are coupled by at least one bridge connector  310 . In the embodiment depicted in  FIG. 3 , two bridge connectors  310 ,  312  are illustrated. In one embodiment, at least one of the bridge connectors, such the bridge connector  312 , may include an inductor coil  314 . At least one of the bridge connectors  310 ,  312  couples the heater elements  284  disposed in each section  304 ,  302 , such that a single lead  316  may be utilized to couple the shielded lid heater  280  to the power source  178 . 
         [0044]      FIG. 4  depicts a top view of the shielded lid heater  280  with the RF shield  206  removed to expose the heater element  284 . As shown, the heater element  284  may be stepped along its path so that a greater density of heating capacity is provided. The ends of the heater element  284  include contacts  402  to facilitate coupling of the heater elements of each section  302 ,  304 , as discussed further below. Also illustrated in  FIG. 4  are threaded holes  404  formed in the conductive base  282  to facilitate fastening of the bridge connectors  310 ,  312 . 
         [0045]      FIG. 5  is a partial front view of one embodiment of the shielded lid heater  280  illustrating the bridge connector  310 . The bridge connector  310  generally includes a body  500  having a plurality of holes  502  which accommodate fasteners  504 . The fasteners  504  engage the threaded holes  404  formed in the conductive base  282 , thereby securing the sections  302 ,  304  together. The sections  302 ,  304  may include a step  510  which engages with a tab  512  to locate the body  500  relative to the conductive bases  282  in a predefined orientation. 
         [0046]    The bridge connector  310  additionally includes a plurality of pins  506  which project therefrom. The pins  506  are configured to electrically connect the contacts  402  formed at the end of the heater elements  284 . Although not shown in  FIG. 5 , the pins  506  couple the resistive elements of each heater elements  284  disposed in each of the portions  302 ,  304  through the body  500 . 
         [0047]    Optionally, the body  500  may be comprised of a conductive material which electrically couples the bases  282  of the sections  302 ,  304 . Alternatively, the body  500  may be fabricated from an insulator. 
         [0048]      FIG. 6  depicts one embodiment of the bridge connector  312 . The bridge connector  312  is coupled to the sections  302 ,  304  of the shielded lid heater  280  as described above. Also as discussed above, the bridge connector  312  includes an inductor coil  314 . The inductor coil  314  may be sized to provide an inductance tailored to influence the magnetic and electric fields within the chamber in order to produce a desired effect on the plasma  106 . In one embodiment, the inductor  314  is a variable inductor to allow tuning of the inductance value between process runs or in situ processing. The inductor coil  314  may be isolated from the conductive bases  282 , or alternatively electrically couple the bases  282  through leads  602 ,  604 . 
         [0049]    A body  600  of the bridge connector  312  may be conductive as to electrically couple the conductive bases  282  of the sections  302 ,  304 . Alternatively, the body  600  of the bridge connector may be fabricated from a dielectric material to electrically insulate the sections  302 ,  304 . 
         [0050]      FIG. 7  is a partial top view of another embodiment of a shielded lid heater  780 . The shielded lid heater  780  is generally configured similar to the heaters  180 ,  280  described above, with the addition of a repositionable inductor  700 . The shielded lid heater  780  includes a plurality of mounting holes  702  which allow the inductor  700  may be fastened at any number of locations. Thus, the position of the inductor  700  along the shielded lid heater  780  may be changed as needed to suit processes needs by securing the inductor  700  to a different set of mounting holes  702 . 
         [0051]    In one embodiment, the inductor  700  may be electrically isolated from the shielded lid heater  780 . In one embodiment, the inductor  700  may be electrically coupled to the conductive base of the shielded lid heater  780  either through contact pins, mounting fasteners or other suitable manner. 
         [0052]      FIG. 8  is a block flow diagram of a method  800  for plasma processing a substrate in a processing chamber equipped with a shielded lid heater. The method  800  begins by determining a position of a plasma within the processing chamber at  802 . The plasma position may be determined by measuring a characteristic of the plasma, by optical methods, utilizing sensors, empirical dates, examination of processing results, modeling or other suitable manner. At  804 , an inductance and/or position of an inductor coil coupled to a lid heater is selected which will to shift the plasma location from the determined position to a target position. At  806 , the substrate is processed in the presence of a plasma with the inductor coil having the selected inductance and/or position. The process performed on the substrate may be selected from the group consisting of etching, chemical vapor deposition, physical vapor deposition, implanting, nitriding, annealing, plasma treating, and ashing, among other plasma processes. 
         [0053]    Thus, a lid heater has been provided that enhances positioning of the plasma within a processing chamber. As the plasma can be positioned in a more desirable location, more uniform and predictable processing requests may be realized. 
         [0054]    While the foregoing is directed to embodiments of the present 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.