Patent Publication Number: US-2017353994-A1

Title: Self-centering pedestal heater

Description:
BACKGROUND 
     Field 
     Embodiments disclosed herein generally relate to a pedestal heater for forming films on substrates, such as semiconductor substrate and, more specifically, a pedestal heater that centers a substrate for a film stack formation process. 
     Description of the Related Art 
     Semiconductor processing involves a number of different chemical and physical processes enabling minute integrated circuits to be created on a substrate. Layers of materials which make up the integrated circuit are created by chemical vapor deposition, physical vapor deposition, epitaxial growth, and the like. Some of the layers of material are patterned using photoresist masks and wet or dry etching techniques. The substrate utilized to form integrated circuits may be silicon, gallium arsenide, indium phosphide, glass, or other appropriate material. 
     A pedestal heater is typically utilized to support a substrate relative to a showerhead in a chamber in a deposition process. Some of the conventional pedestal heaters include a pocket formed in a surface thereof where the substrate may be positioned. However, the typical pocket is sized greater than the substrate such that the substrate may move within the pocket and/or a gap between the edge of the substrate and an inner surface of the pocket varies. This errant positioning of the substrate negatively affects film uniformity. 
     Therefore, what is needed is a pedestal that effectively centers the substrate and prevents movement thereon. 
     SUMMARY 
     A method and apparatus for a heated pedestal is provided. In one embodiment, a pedestal is provided that includes a body, a heater embedded in the body, a support pocket formed within the body having a surface disposed in a first plane, a peripheral surface disposed in a second plane surrounding the support pocket, and a plurality of centering tabs positioned between the support pocket and the peripheral surface, each of the centering tabs having a surface disposed in a third plane that is between both of the first and second planes. 
     In another embodiment, a pedestal is provided that includes a body, an embedded heater disposed in the body, a support pocket formed within the body having a surface disposed in a first plane, a peripheral surface disposed in a second plane surrounding the support pocket, and a plurality of centering tabs positioned between the support pocket and the peripheral surface, each of the centering tabs having a surface disposed in a third plane that is between both of the first and second planes, and a gap having a width that is substantially the same is formed between each of the centering tabs. 
     In another embodiment, a pedestal is provided that includes a body having a heating element embedded therein, a support pocket formed within the body having a surface disposed in a first plane extending a first distance from a longitudinal axis of the body, a peripheral surface disposed in a second plane having a wall surrounding the support pocket, the wall extending a second distance from the longitudinal axis of the body that is greater than the first distance, and a plurality of centering tabs positioned between the first and second distances, each of the centering tabs having a surface disposed in a third plane that is between both of the first and second planes, wherein the first plane and the second plane have a parallelism of 0.002 inches or less. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description, 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 and are therefore not to be considered limiting of its scope, for the embodiments disclosed herein may admit to other equally effective embodiments. 
         FIG. 1  is a partial cross sectional view of a plasma system. 
         FIG. 2A  is an isometric top view of one embodiment of a pedestal that may be utilized in the plasma system of  FIG. 1 . 
         FIG. 2B  is a cross-sectional view of the susceptor body along lines  2 B- 2 B of  FIG. 2A . 
         FIG. 2C  is an enlarged detail view of one of the centering tabs of  FIG. 2A . 
         FIG. 3A  is a cross-sectional view of a portion of the susceptor body showing another embodiment of a centering tab that may be used with the pedestal shown in  FIG. 2A  as one or more of the centering tabs. 
         FIG. 3B  is an elevation view of the centering tab along line  3 B- 3 B of  FIG. 2A . 
         FIG. 4  is a cross-sectional view of a portion of the susceptor body showing another embodiment of a centering tab that may be used with the pedestal shown in  FIG. 2A  as one or more of the centering tabs. 
         FIG. 5  is a cross-sectional view of a portion of the susceptor body showing another embodiment of a centering tab that may be used with the pedestal shown in  FIG. 2A  as one or more of the centering tabs. 
     
    
    
     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 
     Embodiments of the present disclosure are illustratively described below in reference to plasma chambers, although embodiments described herein may be utilized in other chamber types and in multiple processes. In one embodiment, the plasma chamber is utilized in a plasma enhanced chemical vapor deposition (PECVD) system. Examples of PECVD systems that may be adapted to benefit from the disclosure include a PRODUCER® SE CVD system, a PRODUCER® GT™ CVD system or a DXZ® CVD system, all of which are commercially available from Applied Materials, Inc., Santa Clara, Calif. 
     The PRODUCER® SE CVD system chamber has two isolated processing regions that may be used to deposit thin films on substrates, such as conductive films, oxide films such as silicon oxide films, nitride films, polysilicon films, carbon-doped silicon oxides and other materials. Although the exemplary embodiment includes two processing regions, it is contemplated that embodiments disclosed herein may be used to advantage in systems having a single processing region or more than two processing regions. It is also contemplated that embodiments disclosed herein may be utilized to advantage in other plasma chambers, including etch chambers, ion implantation chambers, plasma treatment chambers, and in resist stripping chambers, among others. It is further contemplated that embodiments disclosed herein may be utilized to advantage in plasma processing chambers available from other manufacturers. 
       FIG. 1  is a partial cross sectional view of a plasma system  100 . The plasma system  100  generally comprises a chamber body  102  having sidewalls  112 , a bottom wall  116 , and an interior sidewall  101  defining a pair of processing regions  120 A and  120 B. Each of the processing regions  120 A- 120 B is similarly configured, and for the sake of brevity, only components in the processing region  120 B are described. 
     A pedestal  128  is disposed in the processing region  120 B through a passage  122  formed in the bottom wall  116  in the system  100 . The pedestal  128  provides a heater adapted to support a substrate  129  on the upper surface thereof. The pedestal  128  may include heating elements  132 , for example resistive heating elements, to heat and control the substrate temperature at a desired process temperature. Alternatively, the pedestal  128  may be heated by a remote heating element, such as a lamp assembly. 
     The pedestal  128  is coupled by a flange  133  to a stem  126 . The stem  126  may couple the pedestal  128  to a power outlet or power box  103 . The power box  103  may include a drive system that controls the elevation and movement of the pedestal  128  within the processing region  120 B. The stem  126  may also contain electrical power interfaces to provide electrical power to the pedestal  128 . The power box  103  may also include interfaces for electrical power and temperature indicators, such as a thermocouple interface. The stem  126  also includes a base assembly  138  adapted to detachably couple to the power box  103  thereto. A circumferential ring  135  is shown above the power box  103 . In one embodiment, the circumferential ring  135  is a shoulder adapted as a mechanical stop or land configured to provide a mechanical interface between the base assembly  138  and the upper surface of the power box  103 . 
     A rod  130  is disposed through a passage  124  formed in the bottom wall  116  of the processing region  1206  and may be utilized to position substrate lift pins  161  disposed through the pedestal  128 . The substrate lift pins  161  selectively space the substrate  129  from the pedestal to facilitate exchange of the substrate  129  with a robot (not shown) utilized for transferring the substrate  129  into and out of the processing region  120 B through a substrate transfer port  160 . 
     A chamber lid  104  is coupled to a top portion of the chamber body  102 . The lid  104  may accommodate one or more gas distribution systems  108  coupled thereto. The gas distribution system  108  includes a gas inlet passage  140  which delivers reactant and cleaning gases through a dual-channel showerhead  118  into the processing region  1206 . The dual-channel showerhead  118  includes an annular base plate  148  having a blocker plate  144  disposed intermediate to a faceplate  146 . A radio frequency (RF) source  165  may be coupled to the dual-channel showerhead  118 . The RF source  165  powers the dual-channel showerhead  118  to facilitate generating a plasma region between the faceplate  146  of the dual-channel showerhead  118  and the pedestal  128 . In one embodiment, the RF source  165  may be a high frequency radio frequency (HFRF) power source, such as a 13.56 MHz RF generator. In another embodiment, RF source  165  may include a HFRF power source and a low frequency radio frequency (LFRF) power source, such as a 300 kHz RF generator. Alternatively, the RF source may be coupled to other portions of the chamber body  102 , such as the pedestal  128 , to facilitate plasma generation. A dielectric isolator  158  may be disposed between the lid  104  and the dual-channel showerhead  118  to prevent conducting RF power to the lid  104 . A shadow ring  106  may be disposed on the periphery of the pedestal  128  that engages the pedestal  128 . 
     Optionally, a cooling channel  147  may be formed in the annular base plate  148  of the gas distribution system  108  to cool the annular base plate  148  during operation. A heat transfer fluid, such as water, ethylene glycol, a gas, or the like, may be circulated through the cooling channel  147  such that the base plate  148  may be maintained at a predefined temperature. 
     A liner assembly  127  may be disposed within the processing region  120 B in very close proximity to the sidewalls  101 ,  112  of the chamber body  102  to prevent exposure of the sidewalls  101 ,  112  to the processing environment within the processing region  120 B. The liner assembly  127  includes a circumferential pumping cavity  125  that may be coupled to a pumping system  164  configured to exhaust gases and byproducts from the processing region  120 B and control the pressure within the processing region  120 B. A plurality of exhaust ports  131  may be formed on the liner assembly  127 . The exhaust ports  131  are configured to allow the flow of gases from the processing region  120 B to the circumferential pumping cavity  125  in a manner that promotes processing within the system  100 . 
       FIG. 2A  is an isometric top view of one embodiment of a pedestal  128  that is utilized in the plasma system  100 . The pedestal  128  includes a stem  126  and the base assembly  138  opposite a peripheral surface  205  of a susceptor body  207 . In one embodiment, the stem  126  is configured as a tubular member or hollow shaft. The substrate support  205  includes a substrate receiving surface or support pocket  210  that is substantially planar, or may include a concave or slightly curved surface. The support pocket  210  may be adapted to support a 200 millimeter (mm) substrate, a 300 mm substrate, or a 450 mm substrate. In one embodiment, the support pocket  210  includes a plurality of structures  215 , which may be bumps or protrusions extending above the plane of the support pocket  210 . The height of each of the plurality of structures  215  are substantially equal to provide a substantially planar substrate receiving plane or surface that is slightly elevated or spaced-away from a surface of the support pocket  210 . In one embodiment, each of the structures  215  are formed of or coated with a material that is different from the material of the support pocket  210 . The support pocket  210  also includes a plurality of openings  220  formed therethrough that are adapted to receive a lift pin  161  ( FIG. 1 ). 
     In one embodiment, the susceptor body  207  and stem  126  are made of a conductive metallic material while the base assembly  138  is made of a combination of a conductive metallic material and an insulative material. Fabricating the susceptor body  207  from a conductive metallic material serves to shield an embedded heater (not shown in this view) from RF power. This increases the efficiency and lifetime of the pedestal  128 , which decreases cost of ownership. 
     In one embodiment, the susceptor body  207  and stem  126  are made solely of an aluminum material, such as an aluminum alloy or a ceramic material. In a specific embodiment, both of the susceptor body  207  and stem are made of AlN. In one embodiment, the susceptor body  207  is made from a ceramic material while each of the structures  215  disposed on the support pocket  210  are made of or coated with a ceramic material, such as aluminum oxide. 
     In some embodiments, the support pocket  210  includes a plurality of centering tabs  225 . Each of the centering tabs  225  may be positioned to extend radially inward from the peripheral surface  205  (e.g., toward a longitudinal axis  230  of the pedestal  128 ). The number of centering tabs  225  are not limited to the quantity shown in the drawing and may be three or more, such as four, five, six, seven, eight or more. In some embodiments, the centering tabs  225  are positioned opposite to each other, such as with an even number of centering tabs  225 . In other embodiments, the centering tabs  225  are spaced apart by substantially equal intervals, such as about 120 degrees where there are three centering tabs  225 , or about 72 degrees where there are five centering tabs  225 . 
       FIG. 2B  is a cross-sectional view of the susceptor body  207  along lines  2 B- 2 B of  FIG. 2A . One embodiment of a centering tab  225  is shown in  FIG. 2A . In this embodiment, the centering tab  225  includes a surface  235  in a plane  240  that is intermediate to a plane  245  of a surface  250  of the support pocket  210  and a plane  255  of the peripheral surface  205 . A parallelism between the plane  255  and the plane  245  may be about 0.002 inches or less. The centering tab  225  includes a sloped surface  260  intersecting the surface  250  of the support pocket  210  and the surface  235 . The intersection of the sloped surface  260  with the surface  235  as well as the intersection of the sloped surface  260  with the surface  250  of the support pocket  210  generally defines a substrate receiving area where an edge of a substrate (not shown) may reside during processing. In some embodiments, the angle α of the sloped surface  260  relative to the surface  250  of the support pocket  210  may be about 50 degrees to about 70 degrees, such as about 60 degrees. 
     In one example, when a 300 mm substrate is utilized, a radial length  265  between the longitudinal axis  230  and the intersection of the sloped surface  260  with the surface  235  may be about 5.92 inches (about 150.3 mm). As such, the edge of the 300 mm substrate may contact the sloped surface  260  and fall to a position toward the surface  250  of the support pocket  210 . At some position between the plane  240  and the plane  245  of the surface  250  of the support pocket  210 , a diameter that is substantially equal to the diameter of the substrate is defined (e.g., about +/−6 mm). For example, the intersection of the sloped surface  260  with the surface  250  of the support pocket  210  may include a radial length  268  of about 5.08 inches (about 147.3 mm) in some embodiments. As such, the substrate is centered relative to the longitudinal axis  230  of the pedestal  128 , and may be in thermal communication with the susceptor body  207  such that thermal energy may heat the substrate uniformly. In addition, the elevation and/or parallelism of the substrate relative to the peripheral surface  205  (e.g., the plane  255 ) is controlled. This provides uniform conditions for deposition which increases deposition uniformity. 
     The support pocket  210  may also include a sloped surface  270  interfacing with the surface  235  and opposing the sloped surface  260 . In some embodiments, the angle of the sloped surface  270  may be substantially equal to the angle α of the sloped surface  260  such that the sloped surface  270  and the sloped surface  260  are parallel (e.g., a parallelism of about 0.005 inches or less). A length  272  of the surface  235  in the radial direction as shown in  FIG. 2B  may be about 0.01 inches (0.25 mm) to about 0.03 inches (0.76 mm), such as about 0.02 inches (0.51 mm). 
     A height or distance  246  from the surface  250  of the support pocket  210  (e.g., the plane  245 ) to the surface  235  (e.g., the plane  240 ) may be about 0.02 inches to about 0.03 inches (0.51 mm to 0.76 mm). A height or distance  248  between the surface  235  (e.g., the plane  240 ) to the peripheral surface  205  (e.g., the plane  245 ) may be about 0.04 inches (about 1 mm). 
       FIG. 2C  is an enlarged detail view of one of the centering tabs  225  of  FIG. 2A . The sloped surface  270  is more clearly shown in relation to the centering tab  225 . The sloped surface  270  may occupy portions of the support pocket  210  where no centering tabs  225  are positioned as well as encompass the centering tabs  225 . A radial length  275 , measured between the longitudinal axis  230  of the pedestal  128  and an intersection  274  of the surface  250  of the support pocket  210  and the sloped surface  270 , may be about 5.94 inches (150.88 mm) according to this embodiment. 
     In one embodiment, a gap or channel  276 , formed between the centering tabs  225  has substantially the same width (e.g., +/−0.5 mm measured between the intersection  274  and the sloped surface  260 ) about the entire susceptor body  207  which provides uniform conditions for deposition processes. 
     A length  280  of the sloped surface  260  in a direction orthogonal to the longitudinal axis  230  of the pedestal  128  may be about 0.2 inches (5 mm) to about 0.07 inches (1.7 mm), such as about 0.15 inches (3.8 mm). 
     The configuration of the susceptor body  207  having the centering tabs  225  and the sloped surface  270  surrounding the support pocket  210  provides centering of a substrate relative to the longitudinal axis  230  of the pedestal  128 . Additionally, height of the substrate relative to the surface  250  of the support pocket  210  is controlled. This provides repeatability, prevents movement of the substrate during processing (via pressure changes, for example), and provides a controlled gap between the edge of the substrate and the peripheral surface  205  of the susceptor body  207 . One or more of the above described benefits provides greater uniformity during a deposition or etch process. 
       FIG. 3A  is a cross-sectional view of a portion of the susceptor body  207  showing another embodiment of a centering tab  300  that may be used with the pedestal  128  shown in  FIG. 2A  as one or more of the centering tabs  225 . 
     The centering tab  300  according to this embodiment is substantially the same as the centering tab  225  of  FIG. 2B  with the following exceptions. A radial length  305  between an intersection  310  of the surface  250  of the support pocket  210  and the longitudinal axis  230  of the pedestal  128  may be about 5.92 inches (150.3 mm). In addition, an angle α of the sloped surface  270  relative to the peripheral surface  205  (as well as the surface  250  of the support pocket  210 ) may be about 50 degrees to about 70 degrees, such as about 60 degrees. Additionally, a height or distance  315  between the surface  235  (e.g., the plane  240 ) to the peripheral surface  205  (e.g., the plane  245 ) may be about 0.09 inches (about 2.2 mm). An intersection  320  where the sloped surface  270  meets the peripheral surface  205  may include a radius of about 0.05 inches to about 0.07 inches (1.2 mm to 1.7 mm). 
       FIG. 3B  is an elevation view of the centering tab  300  along line  3 B- 3 B of  FIG. 2A . The centering tab  300  includes the sloped surface  260  and has two compound sloped surfaces  325  (in an X-Y plane as well as a Y-Z plane) that transition from the sloped surface  260  into the sloped surface  270 . The sloped surfaces  325  in the X-Y plane may be formed along a radius relative to a length thereof. In addition, the compound sloped surfaces  325  in the Y-Z plane include an angle  330  that may be about 50 degrees to about 70 degrees, such as about 60 degrees. 
     In one example, when a 300 mm substrate is utilized, the edge of the 300 mm substrate may contact the sloped surface  260  and fall to a position adjacent to the intersection  310 . As such, the substrate is centered relative to the longitudinal axis  230  of the pedestal  128 , and may be in thermal communication with the susceptor body  207  such that thermal energy may heat the substrate uniformly. In addition, the elevation and/or parallelism of the substrate relative to the peripheral surface  205  (e.g., the plane  255 ) is controlled. This provides uniform conditions for deposition which increases deposition uniformity. 
     The configuration of the susceptor body  207  having the centering tabs  300  and the sloped surface  270  surrounding the support pocket  210  provides centering of a substrate relative to the longitudinal axis  230  of the pedestal  128 . Additionally, height of the substrate relative to the surface  250  of the support pocket  210  is controlled. This provides repeatability, prevents movement of the substrate during processing (via pressure changes, for example), and provides a controlled gap between the edge of the substrate and the peripheral surface  205  of the susceptor body  207 . One or more of the above described benefits provides greater uniformity during a deposition or etch process. 
       FIG. 4  is a cross-sectional view of a portion of the susceptor body  207  showing another embodiment of a centering tab  400  that may be used with the pedestal  128  shown in  FIG. 2A  as one or more of the centering tabs  225 . 
     The centering tab  400  according to this embodiment is substantially the same as the centering tab  225  of  FIG. 2B  with the following exceptions. The centering tab  400  according to this embodiment includes a peripheral wall  405  that interfaces with the peripheral surface  205  and the surface  235 . The peripheral wall  405  and the surface  235  may circumscribe or surround the entire support pocket  210 . A radial length  410  between the peripheral wall  405  and the longitudinal axis  230  of the pedestal  128  may be about 5.94 inches (150.8 mm). A radial length  415  of the surface  235  may be about 0.03 inches to about 0.05 inches (0.7 mm to 1.25 mm), such as about 0.04 inches (1.02 mm). A depth  420  (or length orthogonal to the plane  255 ) may be about 0.01 inches (0.254 mm) to about 0.006 inches (0.152 mm), such as about 0.008 inches (0.203 mm). 
     In one example, when a 300 mm substrate is utilized, the edge of the 300 mm substrate may contact the sloped surface  260  and fall to a position adjacent to the surface  250  of the support pocket  210 . As such, the substrate is centered relative to the longitudinal axis  230  of the pedestal  128 , and may be in thermal communication with the susceptor body  207  such that thermal energy may heat the substrate uniformly. In addition, the elevation and/or parallelism of the substrate relative to the peripheral surface  205  (e.g., the plane  255 ) is controlled. This provides uniform conditions for deposition which increases deposition uniformity. 
     The configuration of the susceptor body  207  having the centering tabs  400  and the peripheral wall  405  surrounding the support pocket  210  provides centering of a substrate relative to the longitudinal axis  230  of the pedestal  128 . Additionally, height of the substrate relative to the surface  250  of the support pocket  210  is controlled. This provides repeatability, prevents movement of the substrate during processing (via pressure changes, for example), and provides a controlled gap between the edge of the substrate and the peripheral surface  205  of the susceptor body  207 . One or more of the above described benefits provides greater uniformity during a deposition or etch process. 
       FIG. 5  is a cross-sectional view of a portion of the susceptor body  207  showing another embodiment of a centering tab  500  that may be used with the pedestal  128  shown in  FIG. 2A  as one or more of the centering tabs  225 . 
     The centering tab  500  according to this embodiment is substantially the same as the centering tab  225  of  FIG. 4  with the following exceptions. The centering tab  500  according to this embodiment has a radial length  505  between the peripheral wall  405  and the longitudinal axis  230  of the pedestal  128  of about 5.97 inches (151.64 mm). A radial length  510  of the surface  235  may be about 0.07 inches to about 0.09 inches (1.78 mm to 2.29 mm), such as about 0.08 inches (2.03 mm). A depth  420  (or length orthogonal to the plane  255 ) may be about 0.01 inches (0.254 mm) to about 0.006 inches (0.152 mm), such as about 0.008 inches (0.203 mm). 
     In one example, when a 300 mm substrate is utilized, the edge of the 300 mm substrate may contact the sloped surface  260  and fall to a position adjacent to the surface  250  of the support pocket  210 . As such, the substrate is centered relative to the longitudinal axis  230  of the pedestal  128 , and may be in thermal communication with the susceptor body  207  such that thermal energy may heat the substrate uniformly. In addition, the elevation and/or parallelism of the substrate relative to the peripheral surface  205  (e.g., the plane  255 ) is controlled. This provides uniform conditions for deposition which increases deposition uniformity. 
     The configuration of the susceptor body  207  having the centering tabs  500  and the peripheral wall  405  surrounding the support pocket  210  provides centering of a substrate relative to the longitudinal axis  230  of the pedestal  128 . Additionally, height of the substrate relative to the surface  250  of the support pocket  210  is controlled. This provides repeatability, prevents movement of the substrate during processing (via pressure changes, for example), and provides a controlled gap between the edge of the substrate and the peripheral surface  205  of the susceptor body  207 . One or more of the above described benefits provides greater uniformity during a deposition or etch process. 
     While the foregoing is directed to embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.