Patent Publication Number: US-2010126419-A1

Title: Susceptor for cvd apparatus and cvd apparatus including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of Korean Patent Application No. 10-2008-0119185 filed on Nov. 27, 2008, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus for performing a high-temperature chemical vapor deposition (CVD) process on a substrate, and more particularly, to a susceptor having a structure for uniformly heating a substrate placed thereon, and a CVD apparatus including the susceptor. 
     2. Description of the Related Art 
     Recently, devices such as small and high-performance semiconductor devices and high-power light emitting devices (LEDs) are increasingly required in various industrials. Therefore, there is an increasing need for a chemical vapor deposition (CVD) apparatus that can be used for mass-producing such devices without reducing the quality or performance of the devices. 
     Generally, a CVD apparatus is used to grow a thin epitaxial layer on a substrate by using chemical reaction between a heated top side of the substrate and reaction gas supplied to the inside of a reaction chamber where the substrate is placed. 
     The epitaxial layer grown on the substrate should have a uniform thickness all over the area of the substrate, and for this, the substrate should be uniformly heated. 
     However, a substrate is increased in thickness with an increase in its size, and the substrate may be bent (bowing effect) and cracked due to the difference in stress caused by the increase in thickness of the substrate. 
     If a substrate is bent, an inner region of the substrate may be heated to a relatively higher temperature than an outer region of the substrate because the inner region makes contact with the bottom side of a pocket while the outer region of the substrate is spaced apart from the bottom side of the pocket. 
     In this case, a concentration of a material growing on the substrate varies due to the difference in temperature between the inner and outer regions of the substrate. Therefore, when devices such as LED are formed on the substrate, the substrate may have non-uniform wavelength characteristics, and it may be difficult to perform the subsequent processes, thereby adversely affecting the manufacturing efficiency and product quality. 
     To prevent the bowing effect of a large substrate, various attempts such as patterning of the substrate and modification of a susceptor are being made. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention provides a susceptor having a simple structure and configured to prevent bending of a substrate for uniformly heating the substrate and maintain wavelength uniformity of an epitaxial layer formed on the substrate, and a chemical vapor deposition (CVD) apparatus including the susceptor. 
     According to an aspect of the present invention, there is provided a susceptor for a CVD apparatus, the susceptor including: a rotary part configured to be rotated through a rotation shaft connected to a driving device; and at least one pocket disposed at a top side of the rotary part for receiving a substrate, wherein the pocket includes a block part protruded upward from a bottom side of the pocket on which the substrate is placed, the block part being protruded at a position corresponding to a position of a groove, which is formed in a bottom side of the substrate for distributing stress uniformly along the substrate. 
     The pocket may include one or more block parts according to the number and positions of grooves formed in the bottom side of the substrate. 
     The block part of the pocket may have a ring shape. 
     The block part of the pocket may include a plurality of blocks arranged at predetermined intervals in a ring shape. 
     The pocket may be separable from the rotary part and rotatable relative to the rotary part. 
     The pocket may further include a fixing clip configured to fix the substrate placed at the pocket for preventing escaping of the substrate when the pocket is rotated. 
     The block part of the pocket may have a shape corresponding to that of the groove of the substrate for coupling with the groove. 
     According to another aspect of the present invention, there is provided a CVD apparatus including: a reaction chamber to which reaction gas is supplied through a gas supply unit for performing a deposition process; a substrate to which the reaction gas is supplied for depositing an epitaxial layer on a top side of the substrate, the substrate including a groove in a bottom side thereof for uniformly distributing stress when the epitaxial layer is deposited; a pocket at which the substrate is placed, the pocket including a block part protruded upward from a bottom side of the pocket that makes contact with the bottom side of the substrate, the block part being protruded at a position corresponding to a position of the groove of the substrate; a susceptor including the pocket at a top side thereof; and a heating unit disposed at a bottom side of the susceptor for heating the substrate. 
     The pocket may include one or more block parts according to the number and positions of grooves formed in the bottom side of the substrate. 
     The block part of the pocket may have a ring shape or include a plurality of blocks arranged at predetermined intervals in a ring shape. 
     The pocket may be separable from the susceptor and rotatable relative to the susceptor. 
     The block part of the pocket may have a shape corresponding to that of the groove of the substrate for coupling with the groove. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1A  is a plan view illustrating a susceptor for a chemical vapor deposition (CVD) apparatus according to an embodiment of the present invention; 
         FIG. 1B  is a sectional view taken along line X-X′ of  FIG. 1A ; 
         FIG. 2A  is an enlarged perspective view illustrating pockets and block parts of the susceptor according to an exemplary embodiment of the present invention; 
         FIG. 2B  is an enlarged perspective view illustrating modification versions of the pockets and the block parts of  FIG. 2A  according to another exemplary example of the present invention; 
         FIG. 3  is a sectional view illustrating the pocket and the block part depicted in  FIGS. 2A and 2B ; 
         FIGS. 4A and 4B  are sectional views illustrating modification versions of the pocket and the block part of the susceptor according to other exemplary embodiments of the present invention; 
         FIG. 5  is a sectional view illustrating a modification version of the pocket of the susceptor according to another embodiment of the present invention; 
         FIG. 6A  is a sectional view illustrating a CVD apparatus including a susceptor according to an exemplary embodiment of the present invention; and 
         FIG. 6B  is a sectional view illustrating a CVD apparatus including a susceptor according to another exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A susceptor for a chemical vapor deposition (CVD) apparatus and a CVD apparatus including the susceptor will now be described in detail with reference to the accompanying drawings according to exemplary embodiments of the present invention. 
       FIG. 1A  is a plan view illustrating a susceptor  100  for a chemical vapor deposition (CVD) apparatus according to an embodiment of the present invention, and  FIG. 1B  is a sectional view taken along line X-X′ of  FIG. 1A . 
     Referring to  FIGS. 1A and 1B , according to an embodiment of the present invention, the susceptor  100  for a CVD apparatus includes a rotary part  110 , pockets  120 , and a rotation shaft  130 . 
     The rotary part  110  is a rotary member formed of graphite coated with carbon or silicon carbide (SiC). The rotary part  110  has a disk shape such that the rotary part  110  can be easily rotated in a reaction chamber  31  (refer to  FIG. 6 ) to which reaction gas is supplied. 
     At the top side of the rotary part  110 , the pockets  120  are regularly arranged on the same plane around the rotation center of the rotary part  110  along the circumferential direction. Substrates  10  may be placed in the pockets  120  for chemically depositing a metal compound on the substrates  10 . 
     That is, while simultaneously rotating the substrates  10  placed in the pockets  120  of the rotary part  110 , epitaxial layers may be simultaneously grown on the substrates  10 . 
     The rotation shaft  130  is coupled to the bottom side of the rotary part  110 , and a driving unit (not shown) is connected to the rotation shaft  130 . Therefore, when the rotation shaft  130  is rotated in a predetermined direction by the driving unit, the rotary part  110  is rotated together with the rotation shaft  130  in the predetermined direction. 
     The number of the pockets  120  may be one or more. Substrates  10  may be placed in the pockets  120  for growing epitaxial layers on the substrates  10 . 
     The pockets  120  will now be described in more detail with reference to  FIGS. 2A through 5 . 
       FIG. 2A  is an enlarged perspective view illustrating the pockets  120  and block parts  121  of the susceptor  100  according to an exemplary embodiment of the present invention;  FIG. 2B  is an enlarged perspective view illustrating modification versions of the pockets  120  and the block parts  121  of  FIG. 2A  according to another exemplary example of the present invention;  FIG. 3  is a sectional view illustrating the pocket  120  and the block part  121  depicted in  FIGS. 2A and 2B ;  FIGS. 4A and 4B  are sectional views illustrating modification versions of the pocket  120  and the block part  121  of the susceptor  100  according to other exemplary embodiments of the present invention; and  FIG. 5  is a sectional view illustrating a modification version of the pocket  120  of the susceptor  100  according to another embodiment of the present invention. 
     Referring to  FIGS. 2A and 2B , each of the pockets  120  may have a shape corresponding to a disk-shaped substrate  10 . The pocket  120  may have a diameter larger than that of the substrate  10  so as to easily place the substrate  10  in the pocket  120  and take the substrate  10  out of the pocket  120 . 
     The pocket  120  includes the block part  121 . The block part  121  protrudes upward from the bottom side of the pocket  120  at a position corresponding to a groove  11  formed in the bottom side of the substrate  10  for uniform distribution of stress. 
     For example, when a gallium nitride (GaN) epitaxial layer is growing on a sapphire substrate  10 , the sapphire substrate  10  may be bent (bowing effect) due to the difference in lattice constants and thermal expansion coefficients between the GaN epitaxial layer and the sapphire substrate  10 . The bowing effect becomes serious when the size of the sapphire substrate  10  is large. For example, the bowing effect becomes more serious when the sapphire substrate  10  is a large substrate such as a 6-inch or 8-inch substrate than when the sapphire substrate  10  is a small substrate such as a 4-inch substrate. 
     Therefore, it is necessary to minimize the stress distribution difference between the sapphire substrate  10  and the GaN epitaxial layer to reduce bending of the sapphire substrate  10 . To reduce bending of the sapphire substrate  10 , a groove  11  may be formed in the bottom side of the sapphire substrate  10 . 
     In the case where a substrate  10  having a groove  11  in its bottom side is placed in the pocket  120  with the bottom side of the substrate  10  being in contact with the bottom side of the pocket  120 , an air cavity is formed between the substrate  10  and the pocket  120  due to the groove  11 , and thus it is difficult to heat the substrate  10  uniformly by using a heating unit  33  (refer to  FIG. 6 ) disposed under the susceptor  100 . 
     That is, although a region of the substrate  10  making contact with the bottom side of the pocket  120  may be easily heated to a high temperature owing to a high heat transfer rate, a cavity region of the substrate  10  where the groove  11  is formed may not be easily heated to a high temperature due to a low heat transfer rate. 
     Non-uniform heat distribution of the substrate  10  varies the concentration of a material growing on the substrate  10 . Therefore, for example, when a light emitting diode (LED) is formed on the substrate  10  by growing an epitaxial layer on the substrate  10 , the wavelength uniformity characteristics of the LED may be deteriorated. 
     Therefore, the block part  121  is formed on the bottom side of the pocket  120 . When the substrate  10  is placed in the pocket  120 , the block part  121  is coupled to the groove  11  of the substrate  10 , and thus, a cavity is not formed between the substrate  10  and the pocket  120 . 
     As a result, the substrate  10  may be uniformly heated, and a high-quality epitaxial layer may grow on the substrate  10  uniformly. Therefore, the wavelength non-uniformity of the epitaxial layer may be minimized, and the substrate  10  may have high quality. 
     Referring to  FIG. 2A , the block part  121  protruded on the bottom side of the pocket  120  has a ring shape corresponding to the shape of the groove  11  formed in the bottom side of the substrate  10 . 
     However, the present invention is not limited thereto. That is, as shown in  FIG. 2B , a plurality of blocks  122  may be arranged at regular intervals in a ring shape to form a block part  121 ′. 
     As shown in  FIG. 3 , when the substrate  10  is placed in the pocket  120 , the block part  121  is coupled to the groove  11  of the substrate  10 , and thus an air cavity is not formed by the groove  11 . 
     The substrate  10  may have a single groove  11  as shown in  FIG. 3A  or a plurality of grooves  11  as shown in  FIG. 4A . 
     According to the positions and number of the grooves  11  formed in the bottom side of the substrate  10 , the pocket  120  may include corresponding block parts  121 . 
     As shown in  FIG. 4B , the groove  11  may have an arc-shaped cross-section having a gradually curved profile. In this case, the block part  121  may have an arc-shaped cross-section corresponding to the shape of the groove  11 . 
     The cross-sectional shape of the block part  121  of the pocket  120  is not limited to the illustrated rectangular or arc shape. That is, the cross-section shape of the block part  121  may be varied. For example, the block parts  121  may have a triangular shape. The cross-sectional shape of the block part  121  may be determined according to the shape of the groove  11  formed in bottom side of the substrate  10 . 
     As shown in  FIGS. 2A through 4B , the pocket  120  may be formed in the top side of the rotary part  110  to a predetermined depth as part of the rotary part  110 . 
     Alternatively, as shown in  FIG. 5 , the pocket  120  may be provided in a structure separable from the rotary part  110  and rotatable relative to the rotary part  110 . 
     In the case where the pocket  120  is detachably coupled to the rotary part  110 , the pocket  120  can be replaced with another pocket  120  according to the size of the substrate  10  and the shape or number of grooves  11  formed in the substrate  10 . 
     Therefore, substrates  10  having various structures and sizes can be processed using the susceptor  100  by replacing only the pocket  120  without having to replace the entire susceptor  100 . 
     In addition, independent of the rotation of the rotary part  110 , the pocket  120  can be rotated in the same direction as the rotation direction of the rotary part  110  or in the opposite direction to the rotation direction of the rotary part  110 . In this case, a substrate  10  placed in the pocket  120  can rotate on its axis as the pocket  120  rotates, and at the same time, the substrate  10  may revolve around the rotation center of the rotary part  110  as the rotary part  110  rotates, such that an epitaxial layer may be formed on the substrate  10  more uniformly. 
     The pocket  120  may further include a fixing clip (not shown) to prevent escaping of the substrate  10  from the pocket  120  during rotation. 
     Examples  30  and  30 ′ of a CVD apparatus including the above-described susceptor  100  will now be described with reference to the accompanying drawings according to exemplary embodiments of the present invention. 
       FIG. 6A  is a sectional view illustrating a CVD apparatus  30  including a susceptor according to an exemplary embodiment of the present invention, and  FIG. 6B  is a sectional view illustrating a CVD apparatus  30 ′ including a susceptor according to another exemplary embodiment of the present invention. 
     Referring to  FIGS. 6A and 6B , each of the CVD apparatus  30  and  30 ′ includes a reaction chamber  31 , a substrate  10 , a pocket  120 , a susceptor  100 , and a heating unit  33 . 
     The reaction chamber  31  has a vertical cylindrical structure and provides a predetermined inner space that can be used for depositing and growing an epitaxial layer on the top side of the substrate  10  (for example, a sapphire substrate) through chemical reaction between the sapphire substrate  10  and reaction gas introduced into the reaction chamber  31  through a gas supply unit  34 . 
     The reaction chamber  31  may be formed of an abrasion-resistant, corrosion-resistant metallic material, and a thermal insulator may be disposed on the inner surface of the reaction chamber  31  for protecting the reaction chamber  31  from a high-temperature atmosphere. 
     In the reaction chamber  31 , the susceptor  100  and the heating unit  33  are disposed. At least one substrate  10  can be mounted on the susceptor  100 . An exhaust port  131  is provided at the reaction chamber  31  for discharging gas after the gas chemically reacts with the substrate  10 . 
     As shown in  FIG. 6A , the gas supply unit  34  may be disposed at an upper side of the reaction chamber  31  and have a showerhead shape for vertically injecting reaction gas to the upper side of the susceptor  100  which rotates under the gas supply unit  34 . 
     Alternatively, as shown in  FIG. 6B , a gas supply unit  34 ′ may be disposed along the lateral upper end portion of the reaction chamber  31 . The gas supply unit may have a planetary structure for horizontally injecting reaction gas into the reaction chamber  31  through a plurality of injection nozzles  35  in directions from the periphery of the reaction chamber  31  toward the center of the reaction chamber  31 . 
     In this case, deposition may proceed while the reaction gas flows from the periphery of the susceptor  100  toward a rotation shaft  130 , and then the reaction gas may be discharged from the inside of the reaction chamber  31  through an exhaust port  131  formed in the rotation shaft  130 . 
     In addition, a reverse flow prevention unit (not shown) may be disposed at the exhaust port  131  to prevent a reverse flow of reaction gas from the exhaust port  131  to the inside of the reaction chamber  31  caused by a pressure difference or error. 
     The pocket  120  includes a block part  121  protruded upward from the bottom side of the pocket  120  at a position corresponding to the position of a groove  11  formed in the bottom side of the substrate  10 , so as to uniformly distribute stress when a deposition process is performed in a state where the substrate  10  is placed in the pocket  120  and brought into contact with the bottom side of the pocket  120 . 
     The susceptor  100  may include a plurality of pockets  120  at the top side thereof for performing a deposition process simultaneously on a plurality of substrates  10 . 
     The substrate  10 , the pocket  120 , and the susceptor  100  including the pocket  120  at its top side are substantially the same as those shown in  FIGS. 1  A through  5 . Thus, the structures and functions thereof will not be described in detail. 
     The heating unit  33  is disposed near the bottom side of the susceptor  100  for heating the susceptor  100  where the substrate  10  is placed. 
     The heating unit  33  may be one of an electric heater, a high-frequency induction heater, an infrared radiation heater, and a laser heater. 
     A temperature sensor (not shown) may be disposed at the reaction chamber  31  in the vicinity of the susceptor  100  or the heating unit  33  for measuring the inside temperature of the reaction chamber  31  and controlling the heating temperature of the heating unit  33  based on the measured temperature. 
     In the case where an epitaxial layer such as a gallium nitride (GaN) epitaxial layer, an aluminum nitride (AlN) epitaxial layer, or an indium nitride (InN) epitaxial layer is grown on a sapphire substrate  10  using a CVD apparatus including the above-described susceptor  100 , first, the substrate  10  is placed in the pocket  120  disposed at the top side of a rotary part  110  of the susceptor  100 . 
     In this state, the rotary part  110  is rotated by a driving motor (not shown) in a predetermined direction, and group III source gas such as trimethyl gallium (TMGa), triethyl gallium (TEGa), trimethyl indium (TMIn), and trimethyl aluminum (TMAl) is supplied, together with carrier gas such as ammonia, to the inside of the reaction chamber  31  where the rotary part  110  is disposed. 
     The heating unit  33  disposed under the rotary part  110  is operated to heat the substrate  10 . Then, while a mixture (reaction gas) of the source gas and the carrier gas makes contact with the surface of the substrate  10  that rotates together with the rotary part  110  in the predetermined direction, a thin nitride layer (for example, a semiconductor epitaxial layer) is uniformly grown on the surface of the substrate  10 , and remaining gas or byproducts flow downward along an inner wall of the reaction chamber  31  and are discharged to the outside. 
     As described above, the groove  11  is formed in the bottom side of the substrate  10  so as to prevent bending (bowing effect) of the substrate  10  during a layer growing process, and the block part  121  is disposed at the bottom side of the pocket  120  to couple the block part  121  to the groove  11  of the substrate  10  when the substrate  10  is placed in the pocket  120  and brought into contact with the bottom surface of the pocket  120  so as to prevent non-uniform heating of the substrate  10 . Therefore, wavelength uniformity of an epitaxial layer formed on the substrate can be maintained. For example, a high-quality substrate product can be manufactured by uniformly forming a high-quality nitride layer on the surface of a substrate. 
     According to the susceptor and the CVD apparatus including the susceptor, bending (bowing effect) of a larger substrate caused by non-uniform stress distribution may be minimized, and the substrate may be uniformly heated, such that the wavelength uniformity of an epitaxial layer formed on the substrate can be maintained. Therefore, high-quality substrate products can be provided. 
     While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.