Patent Publication Number: US-2013239894-A1

Title: Chemical vapor deposition apparatus

Description:
BACKGROUND OF THE INVENTION  
     1. Field of the Invention 
     The present invention generally relates to chemical vapor deposition (CVD), and more particularly to a CVD apparatus having a susceptor that is mounted in a non-horizontal manner. 
     2. Description of Related Art 
     Chemical vapor deposition (CVD) is a semiconductor process used to produce thin films. A conventional CVD apparatus typically includes a graphite susceptor that is horizontally placed in a chamber. A showerhead located above the susceptor is used to provide a reaction gas to one or more wafers supported on the susceptor. The reaction gas then reacts on the wafers to produce desired films on the wafers. 
     As the susceptor is generally designed to capably hold a large number of wafers, a large area may be required to accommodate the CVD apparatus. Because of the large area occupied by the CVD apparatus, the number of CVD apparatus that can be located in a semiconductor manufacturing factory may be limited. Because conventional CVD apparatus are bulky and area consuming, there is a need for novel CVD apparatus or systems that take less area in the semiconductor manufacturing factory. 
     SUMMARY  
     In certain embodiments, a chemical vapor deposition (CVD) apparatus occupies less area than conventional CVD apparatus, such that more CVD apparatuses can be located in a semiconductor manufacturing factory. In some embodiments, a CVD system stacks a number of CVD apparatuses to further enhance efficiency in area, mass production, or cost. 
     In certain embodiments, a chemical vapor deposition (CVD) apparatus includes at least one susceptor and at least one holder. The susceptor is mounted in a non-horizontal position. The holder is rotatably mounted on a first surface of the susceptor for holding one or more wafers, the holder being rotatable around a holder axis. In some embodiments, the CVD apparatus includes a showerhead mounted at or near a center of the susceptor. A reaction gas may be released from the showerhead and flow radially toward a periphery of the susceptor. In some embodiments, the holder has a mass center that is eccentric from the holder axis. The eccentric mass center allows the holder to have movement relative to the susceptor when the susceptor rotates. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  shows a cross-sectional side view of an embodiment of a chemical vapor deposition (CVD) apparatus. 
         FIG. 1B  shows a cross-sectional side view of another embodiment of the CVD apparatus. 
         FIG. 2  shows an elevational view of the susceptor taken from a pair of broken lines  2 - 2  of  FIGS. 1A and 1B ; 
         FIGS. 3A-3D  show representations of embodiments of a holder. 
         FIG. 4  shows a cross-sectional side view of an additional embodiment of a CVD apparatus. 
         FIG. 5  shows a cross-sectional side view of another additional embodiment of a CVD apparatus. 
         FIG. 6  shows a cross-sectional side view of yet another embodiment of a CVD apparatus. 
         FIG. 7  shows an elevational view of the susceptor taken from a pair of broken lines  7 - 7  of  FIG. 6 . 
         FIG. 8  shows a cross-sectional side view of an embodiment of a vertically stacked CVD system. 
         FIG. 9  shows a top view of an embodiment of a horizontally stacked CVD system. 
         FIG. 10  shows a top view of an embodiment of a horizontally stacked CVD system without a chamber wall. 
         FIG. 11  shows a top view of an embodiment of another horizontally stacked CVD system without the chamber wall. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS  
       FIG. 1A  shows a cross-sectional side view of an embodiment of a chemical vapor deposition (CVD) apparatus. In certain embodiments, CVD apparatus  100  includes at least one susceptor  10  that is mounted in a non-horizontal position. For example, susceptor  10  may be mounted in a substantially vertical position (e.g., a susceptor axis of the susceptor is substantially perpendicular to the direction of gravity). In certain embodiments, CVD apparatus  100 , as shown in  FIG. 1A , includes two susceptors  10 A,  10 B that face each other. 
       FIG. 1B  shows a cross-sectional side view of another embodiment of CVD apparatus  100 ′. In certain embodiments, susceptors  10 A,  10 B are mounted within an angle of 45° with respect to the direction of gravity. For example, susceptors  10 A,  10 B may be mounted at an angle of 15° with respect to the direction of gravity, as shown in  FIG. 1B . 
       FIG. 2  shows an elevational view of susceptor  10  taken from a pair of broken lines  2 - 2  of  FIGS. 1A and 1B . At least one holder  101  is rotatably mounted on a first (e.g., front) surface of susceptor  10  for holding one or more wafers (not shown). Holder  101  may be, for example, a graphite disc. In certain embodiments, holder  101  is adapted to be rotatable relative to susceptor  10 . Holder  101  may be rotatable around a holder axis that is substantially parallel with and distinct from the susceptor axis. It is appreciated by those skilled in the pertinent art that the susceptor axis (or the holder axis) may be a physical axis used to support and rotate susceptor  10  (or holder  101 ), or the susceptor axis (or the holder axis) may be a virtual (or hypothetical) axis, around which the susceptor (or the holder) rotates. 
     In some embodiments, one or more securing mechanisms (not shown) may be required to keep holder  101  from falling/dropping from susceptor  10  (e.g., in the embodiment of CVD apparatus  100  shown in  FIG. 1A ). Securing mechanisms may be omitted in certain embodiments (e.g., the embodiment of CVD apparatus  100 ′ shown in  FIG. 1B ). 
     In certain embodiments, as shown in  FIG. 3A , holder  101  has a mass center  102  that is eccentric from an area center  103  (or the holder axis). The eccentric mass center allows holder  101  to have movement relative to susceptor  10 . In some embodiments, holder  101  includes counterweight  104  (shown in  FIG. 2 ), which makes mass center  102  of holder  101  eccentric from area center  103 . Accordingly, as susceptor  10  rotates, holder  101  is kept upright by gravity in a manner similar to a chair on a Ferris wheel. The eccentric mass center  102  may be realized by a variety of implementations. For example, as shown in  FIG. 3B , mass  30  may be coupled (e.g., additively attached) at an edge of holder  101 . As shown in  FIG. 3C , wafers may be placed off-center of the area center  103 . The wafers may be located within predetermined range  31  that is eccentric from area center  103 . As shown in  FIG. 3D , bearing  32  may be placed around holder  101  to allow constrained relative rotation between the holder and susceptor  10 . Mass  33  may be further attached at bearing  32  to result in an eccentric mass center. In one exemplary embodiment, the bearing  32  may include an inner bearing and an outer bearing, wherein the former is fixed to the holder  101  and is attached with a mass or counterweight, and the latter is fixed to the susceptor  10 . In another exemplary embodiment, the bearing  32  may include a top bearing and a bottom bearing, wherein the former is fixed to the holder  101  and is attached with a mass or counterweight, and the latter is fixed to the susceptor  10 . 
     Referring back to  FIGS. 1A ,  1 B, and  2 , showerhead  11  may be mounted at or near a center of susceptor  10 . In certain embodiments, as shown in  FIGS. 1A and 1B , showerhead  11  is located between two susceptors  10 A,  10 B such that the showerhead is shared between the two susceptors. Sharing showerhead  11  may substantially reduce the overall cost. In general, showerhead  11  may be shared among more than two susceptors that face each other and are arranged, for example, in a triangular, a rectangular, or a polygonal arrangement. 
     In certain embodiments, a reaction gas is released from nozzles  21  (denoted by hollow circles) of showerhead  11 , and the reaction gas flows radially toward a periphery of susceptors  10 A,  10 B (as shown by the arrows in  FIG. 2 ) to provide the reaction gas to one or more wafers held on holders  101 A,  101 B. In certain embodiments, showerhead  11  has a form of a cylinder and the nozzles are formed on the cylindrical surface of the showerhead. At least one gas pipe line  111  and at least one coolant pipe line  112  may be located in showerhead  11  to provide the reaction gas (and/or purge gas) and coolant, respectively. 
     In certain embodiments, exhaust outlet plates  12 A,  12 B are located near a second (back) surface of each susceptor  10 A,  10 B and are fixed with respect to the ground. A plurality of exhaust holes  120 A,  120 B may be formed on exhaust outlet plates  12 A,  12 B. In some embodiments, as shown in  FIG. 2 , (upper) exhaust holes  120 A on the upper periphery of exhaust outlet plate  12  have a diameter larger than that of (lower) exhaust holes  120 B on the lower periphery of the exhaust outlet plate. As upper exhaust holes  120 A may have a flow resistance lower than that of lower exhaust holes  120 B, and due to the fact that the reaction gas tends to be pulled downward by gravity, the upper exhaust holes may have a larger drawing force (with respect to the lower exhaust holes) to smoothly and effectively bring out exhaust gas. In certain embodiments, heater  13  is mounted away from the second (back) surfaces of susceptors  10 A,  10 B for heating the wafers held on holders  101 A,  101 B. 
     In certain embodiments, as shown in  FIGS. 1A and 1B , susceptors  10 A,  10 B have rotating shells  105 A,  105 B that extend away from the second (back) surfaces of the susceptors. Motors  14 A,  14 B may be used to drive rotating shells  105 A,  105 B via gears  141 A,  141 B, thereby rotating susceptors  10 A,  10 B. 
       FIG. 4  shows a cross-sectional side view of an additional embodiment of a CVD apparatus. The embodiment of CVD apparatus  100 ″ shown in  FIG. 4  is similar to the embodiment of CVD apparatus  100 ′, shown in  FIG. 1A , with the exception that CVD apparatus  100 ″ includes flange  113  extending from showerhead  11 . Flange  113  may include nozzles  21 ′ formed on a surface of the flange. The reaction gas released from nozzles  21 ′ of flange  113  may flow toward the wafers in a direction perpendicular to the radially moving reaction gas released from nozzles  21  of showerhead  11 . 
       FIG. 5  shows a cross-sectional side view of another additional embodiment of a CVD apparatus. The embodiment of CVD apparatus  100 ″′ is similar to the embodiment of CVD apparatus  100 ′, shown in  FIG. 1A , with the exception that no counterweight  104  (shown in  FIG. 2 ) is needed in CVD apparatus  100 ″′. As shown in  FIG. 5 , instead of the counterweight, holder gears  106 A,  106 B are attached to periphery of holders  101 A,  101 B. In certain embodiments, fixed gears  114 A,  114 B are attached to fixed shell  115  that extends from showerhead  11 . As susceptors  10 A,  10 B rotate, holders  101 A,  101 B may rotate relative to the susceptors due to the mesh or engagement between holder gears  106 A,  106 B and fixed gears  114 A,  114 B. 
       FIG. 6  shows a cross-sectional side view of yet another embodiment of a CVD apparatus, and  FIG. 7  shows an elevational view of susceptor  10  taken from a pair of broken lines  7 - 7  of  FIG. 6 . The embodiment of CVD apparatus  100 ″′ is similar to the embodiment of CVD apparatus  100 ″′, shown in  FIG. 5 , with the exception that holder gears  106 A,  106 B and fixed gears  114 A,  114 B are replaced with one or more susceptor rollers  107 A,  107 B and one or more holder rollers  108 A,  108 B. In certain embodiments, susceptor rollers  107 A,  107 B support and rotate the susceptors  10 A,  10 B and holder rollers  108 A,  108 B support and rotate holders  101 A,  101 B. As described herein, the rotation of holders  101 A,  101 B may, alternatively, be realized by a physical axis such as a pin (not shown) that supports and drives the holders. 
     Although a single CVD apparatus has been demonstrated in the preceding embodiments, a number of CVD apparatuses described above may be stacked to build a CVD system. For example, a plurality of CVD apparatuses may be located substantially adjacent to each other in a CVD system (either horizontally or vertically).  FIG. 8  shows a cross-sectional side view of an embodiment of a vertically stacked CVD system. CVD system  800  may be made up of a number of CVD apparatuses  100  that are substantially vertically stacked. In certain embodiments, showerhead  11  is mounted at the top of CVD system  800  to provide the reaction gas. Exhaust outlet  121  may be located at the bottom of CVD system  800  for bringing an exhaust gas out of the CVD system. It is noted that showerhead  11  is shared among all the CVD apparatuses, which may reduce overall cost. 
       FIG. 9  shows a top view of an embodiment of a horizontally stacked CVD system. CVD system  900  may be made up of a number of CVD apparatuses  100  that are substantially horizontally or vertically linked or adjacent to each other. In certain embodiments, neighboring CVD apparatuses  100  are isolated from each other by chamber wall  15 . Accordingly, each CVD apparatus  100  may be operated individually for performing its associated CVD process. 
       FIG. 10  shows a top view of an embodiment of horizontally stacked CVD system  1000  without the chamber wall. Accordingly, all CVD apparatuses  100  may be simultaneously operated, thereby facilitating mass production. In certain embodiments, each CVD apparatus  100  is individually provided with the reaction gas through individual showerheads  11 .  FIG. 11  shows a top view of an embodiment of another horizontally stacked CVD system  1100  without the chamber wall. In the embodiment, all CVD apparatuses are provided with the reaction gas through a common gas inlet  116  coupled to showerheads  11 . 
     As described herein, susceptor  10  may be mounted in a substantially vertical or near vertical position. In certain embodiments described herein, susceptor  10  is in an approximately vertical position. However, in some embodiments, susceptor  10  may be inclined at an angle enough for the wafers supported and held on the holder  101  without locking the wafers to the holder  101  (e.g., as shown in the embodiment depicted in  FIG. 1B ). 
     It is to be understood the invention is not limited to particular systems described which may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting. As used in this specification, the singular forms “a”, “an” and “the” include plural referents unless the content clearly indicates otherwise. Thus, for example, reference to “a device” includes a combination of two or more devices and reference to “a reactant gas” includes mixtures of reaction gases. 
     Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as the presently preferred embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the spirit and scope of the invention as described in the following claims.