Abstract:
A heater assembly and a wafer processing apparatus using the same are provided. The heater assembly comprises a substrate, a heater, a reflector and a protective layer. The substrate has a top surface, a side surface surrounding the top surface and a trench formed on the top surface. The heater comprises a heater element accommodated within the trench and two electrodes respectively connecting two ends of the heater element and extending outside of the substrate. The reflector covers an inner surface of the trench. The protective layer covers the top surface, the side surface and the trench.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention generally relates to a wafer processing apparatus, and more particularly to a heater assembly for a wafer processing apparatus. 
       DESCRIPTION OF THE RELATED ART 
       [0002]    In semiconductor fabrication, it is important to modulate a temperature of a wafer, such as to heat the wafer or to maintain the temperature of the wafer, and thus deposition or growth of materials and selective removal or modification of the deposited/grown materials are controllable. In practice, a heater assembly located within a chamber is usually used for the above-mentioned purpose. 
         [0003]    For example, the wafer may be held and heated to a predetermined temperature by the heater assembly within the chamber first. After that, the wafer may be maintained at the predetermined temperature, and thus a material may be deposited on the wafer with desired deposition parameters by a chemical vapor deposition (CVD) process, such as metal organic chemical vapor deposition (MOCVD), plasma enhanced chemical vapor deposition (PECVD), high density plasma chemical vapor deposition (HDP-CVD), expanding thermal plasma chemical vapor deposition (ETP-CVD), thermal plasma chemical vapor deposition (TPCVD), etc. 
         [0004]    Note that a heater of the conventional heater assembly is usually directly exposed in the chamber and some matters provided or generated in the chamber may be harmful to the heater. For example, the heater may be damaged by plasma attacks or chemicals used in the cleaning process. Accordingly, it is highly desirable to protect the heater against damage, so as to enhance the lifetime of the heater. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention is directed to a heater assembly and a wafer processing apparatus using the same, wherein the protective layer may protect the heater against a mechanical damage. 
         [0006]    The present invention provides a heater assembly formed integrally and monolithically for a wafer processing apparatus comprising a substrate, at least a heater, a reflector and a protective layer. The substrate has a top surface, a side surface surrounding the top surface and at least a trench formed on the top surface with a predetermined pattern. The heater comprises a heater element accommodated within the trench and two electrodes respectively connecting two ends of the heater element and extending outside of the substrate. The reflector covers a bottom surface of the trench. The protective layer covers the top surface, the side surface and the trench. 
         [0007]    The present invention further provides a wafer processing apparatus comprising a chamber, a spindle comprising a carrier and a shaft and the above-mentioned heater assembly. The carrier is disposed within the chamber and having a first side and a second side opposite to the first side. The shaft passes through a wall of the chamber and an end thereof within the chamber connects the first side. The heater assembly formed integrally and monolithically may be fixed on the second side as a bottom surface of the substrate facing the second side, and the two electrodes electrically connect to a power supply located outside of the chamber via the spindle. 
         [0008]    According to an embodiment of the present invention, the substrate is made by a ceramic sintering process or a CVD process and the trench is formed by machining the top surface of the substrate. 
         [0009]    According to an embodiment of the present invention, a material of the substrate is AlN or Al 2 O 3  when a heating temperature of the heater is lower than 1000° C. and is SiC, BN (boron nitride) or PBN (pyrolytic boron nitride) when a heating temperature of the heater is higher than 1000° C. 
         [0010]    According to an embodiment of the present invention, a material of the heater is graphite, W, SiC or Mo. 
         [0011]    According to an embodiment of the present invention, the electrodes connect two ends of the heater element respectively. 
         [0012]    According to an embodiment of the present invention, the electrodes pass through the bottom surface. 
         [0013]    According to an embodiment of the present invention, the reflector is made by BN or PBN on metal-based materials. 
         [0014]    According to an embodiment of the present invention, the protective layer further covers side surfaces of the trench. 
         [0015]    According to an embodiment of the present invention, the protective layer is made by a thin film coating process and capable of standing the temperature of the heater. 
         [0016]    According to an embodiment of the present invention, materials of the substrate and the protective layer are the same. 
         [0017]    According to an embodiment of the present invention, outer surfaces of the protective layer are flat surfaces. 
         [0018]    According to an embodiment of the present invention, a thickness of the protective layer ranges inclusively between 0.1 mm and 2 mm. 
         [0019]    In contrast to the conventional heater assembly, the heater of the present invention is covered by the protective layer, and thus the protective layer may protect the heater against plasma attacks and chemicals. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1A  illustrates a schematic view of a wafer processing apparatus according to an embodiment of the present invention. 
           [0021]      FIG. 1B  illustrates an explosion view of the heater assembly as illustrated in  FIG. 1A . 
           [0022]      FIGS. 2A to 2D  illustrate different schematic layouts of the heaters designed on the substrates according to different embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    Reference will now be made in detail to specific embodiments of the present invention. Examples of these embodiments are illustrated in the accompanying drawings. While the invention will be described in conjunction with these specific embodiments, it will be understood that it is not intended to limit the invention to these embodiments. In fact, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. In the following description, numerous specific details are set forth in order to provide a through understanding of the present invention. The present invention may be practiced without some or all of these specific details. In other instances, well-known process operations are not described in detail in order not to obscure the present invention. 
         [0024]      FIG. 1A  illustrates a schematic view of a wafer processing apparatus according to an embodiment of the present invention,  FIG. 1B  illustrates an explosion view of the heater assembly as illustrated in  FIG. 1A , and  FIGS. 2A to 2D  illustrate different schematic layouts of the heaters designed on the substrates according to different embodiments of the present invention. Referring to  FIG. 1 , the wafer processing apparatus  10  for modulating a temperature of a wafer  20 , for example heating a wafer  20  or maintaining a temperature of a wafer  20 , is composed of a chamber  100 , a spindle  200  and a heater assembly  300 . A carrier  210  of the spindle  200  is disposed within the chamber  100 . In addition, a shaft  220  of the spindle  200  passes through a bottom wall  110  of the chamber  100  from outside of the chamber  100  to connect a bottom side of the carrier  210 . Further, the heater assembly  300  may be fixed on a top side of the carrier  210  by fasteners (not shown), such as screws, clamps, etc. 
         [0025]    The heater assembly  300  is formed integrally and monolithically and comprises a substrate  310 , a heater  320 , a reflector  330  and a protective layer  340 . The substrate  310  has a top surface  312 , a bottom surface  314 , a side surface  316  and a trench  318 . The bottom surface  314  is opposite to the top surface  312  and faces the top side of the carrier  210  when the heater assembly  300  is fixed on the carrier  210 . The side surface  316  surrounds and connects between the top surface  312  and the bottom surface  314 . The trench  318  is formed on the top surface  312  with a predetermined pattern. In the present embodiment, the substrate  310  may be made by a ceramic sintering process or a CVD process and the trench  318  may be formed by machining the top surface  312 . 
         [0026]    Furthermore, the heater  320  includes a heater element  322  and two electrodes  324 . The heater element  322 , for example a wire, is accommodated within and supported well by the trench  318  to form an electrical flow with the predetermined pattern. Each of the electrodes  324  connects an end of the heater element  322  and may further pass through the bottom surface  314  to extend outside of the substrate  310 . In the present embodiment, the electrodes  324  may electrically connect to a power supply (not shown) located outside of the chamber  100  via wires  400  passing through the spindle  200 , and thus the wafer  20  may be uniformly heated by the heater element  322 . Note that if a heating temperature of the heater  320  is lower than 1000° C., it is recommended to choose AlN, Al 2 O 3  or SiC for being a material of the substrate  310 . In contrary, if a heating temperature of the heater  320  is higher than 1000° C., it is recommended to choose SiC, BN (boron nitride) or PBN (pyrolytic boron nitride) for being a material of the substrate  310 . In addition, the heater  320  may be made by metal or non-metal based materials, such as graphite, W, SiC or Mo, and machined to form the required shape, cross-section and resistivity. 
         [0027]    Note that the top view of the schematic layout of the heater element  322  designed on the substrate  310  may be a serpentine geometry with locating the electrodes  324  at two opposite sides of the substrate  310  as illustrated in  FIG. 2A  or the same side of the substrate  310  as illustrated in  FIG. 2B , a spiral geometry with locating the electrodes  324  at two opposite sides of the substrate  310  as illustrated in  FIG. 2C  or the same side of the substrate  310  as illustrated in  FIG. 2D , or any other proper layouts. In addition, both numbers of the trench  318  and the heater  320  are only one in the present embodiments for providing single heating zone, but may be two or more in other un-illustrated embodiments for providing multiple heating zones. Besides, the electrodes in other un-illustrated embodiments may connect between two ends of the heater element, and thus only a portion of the heater element between the electrodes may use for heating the wafer. 
         [0028]    Moreover, the reflector  330  covers a bottom surface of the trench  318 , but covering both the bottom surface and the side surfaces of the trench  318  is preferred, and may be made by BN or PBN on metal-based materials which may sustain a higher temperature. Therefore, the heat generated by the heater  320  may be reflected towards designed directions, such as upward, to be used more efficiency, instead of being transmitted towards non-design directions, such as downward or sideward, to be wasted. 
         [0029]    In addition, the protective layer  340  may be made by a thin-film coating process, such as a CVD process, to cover the top surface  312 , the side surface  316 , the trench  318 , the heater element  322  and the reflector  330  with a thickness ranges inclusively between 0.1 mm and 2 mm, and is capable of standing the temperature of the heater  320 . In the present embodiment, outer surfaces of the protective layer  340 , including a top surface  342  and a side surface  344 , may be flat surfaces to form uniform heat surface distribution. Further, the protective layer  340  may be made by a material similar to or the same as the material of the substrate  310 , so as to have similar or the same coefficient of thermal expansion (CTE) and thermal conductivity as the substrate  310 . 
         [0030]    In contrast to the conventional heater exposed in the chamber directly, the heater element  322  of the present invention is enclosed by the substrate  310  and the protective layer  340 , and thus the heater element  322  may be protected against a mechanical damage, such as attacks by plasma or chemicals used in the cleaning process. 
         [0031]    Although specific embodiments of the present invention have been described, it will be understood by those of skill in the art that there are other embodiments that are equivalent to the described embodiments. Accordingly, it is to be understood that the invention is not to be limited by the specific illustrated embodiments, but only by the scope of the appended claims.