Abstract:
A method and apparatus for hydride vapor phase epitaxial (HVPE) deposition is disclosed. In the HVPE process, a hydride gas flows over a metal source to react with the metal source, which then reacts at the surface of a substrate to deposit a metal nitride layer. The metal source comprises gallium, aluminum, and/or indium. The hydride gas is evenly provided over the metal source to increase efficiency of hydride-metal source reaction. An exhaust positioned diametrically across the chamber from the metal source creates a cross flow of the hydride-metal source product and nitrogen precursor across the chamber tangential to the substrate. A purge gas flowing perpendicular to the cross flow directs the hydride-metal source product and nitrogen precursor to remain as close to the substrate as possible.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    Embodiments of the present invention generally relate to an apparatus for hydride vapor phase epitaxial (HVPE) deposition. Additional embodiments of the present invention generally relate to a HVPE deposition method. 
         [0003]    2. Description of the Related Art 
         [0004]    Group-III nitride semiconductors are finding greater importance in the development and fabrication of short wavelength light emitting diodes (LEDs), laser diodes (LDs), and electronic devices including high power, high frequency, and high temperature transistors and integrated circuits. One method that has been used to deposit Group-III nitrides is HVPE. In HVPE, a hydride gas reacts with the Group-III metal which then reacts with a nitrogen precursor to form the Group-III metal nitride. 
         [0005]    As the demand for LEDs, LDs, transistors, and integrated circuits increases, the efficiency of depositing the Group-III metal nitride takes on greater importance. Therefore, there is a need in the art for an improved HVPE deposition method and an HVPE apparatus. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention generally comprises a HVPE deposition method and apparatus. In one embodiment, a hydride vapor phase epitaxial method is disclosed. The method comprises positioning at least one substrate in a chamber, flowing a metal chloride gas and a first nitrogen precursor across the chamber, directing the first nitrogen precursor and the metal chloride to flow substantially tangential to the deposition surface of the substrate by flowing a purge gas into the chamber in a direction substantially perpendicular to the deposition surface, and reacting the first nitrogen precursor with the metal chloride to deposit a metal nitride on the at least one substrate. 
         [0007]    In another embodiment, a hydride vapor phase epitaxial apparatus is disclosed. The apparatus comprises a chamber having a chamber body, a substrate carrier having a surface for receiving one or more substrates disposed within the chamber body, a source boat disposed within the chamber body and adjacent the substrate carrier, a first gas inlet coupled to a nitrogen precursor source and the chamber body, a second gas inlet separate from the first gas inlet and coupled with a hydride gas source and the chamber body, and one or more third gas inlets coupled with the chamber body and oriented to direct gas into the chamber body in a direction substantially perpendicular to the surface for receiving the one or more substrates. 
         [0008]    In yet another embodiment, a hydride vapor phase epitaxial apparatus is disclosed. The apparatus comprises a substrate carrier disposed within a chamber body, a source boat disposed within the chamber body and adjacent the substrate carrier, and a cover coupled with the boat. The boat has a gas passage bounded by a wall having a plurality of openings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    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. 
           [0010]      FIG. 1  is a schematic cross sectional view of an HVPE chamber according to one embodiment of the invention. 
           [0011]      FIG. 2A  is a schematic perspective view of the HVPE chamber of  FIG. 1 . 
           [0012]      FIG. 2B  is a schematic perspective view of the source boat of  FIG. 2A . 
           [0013]      FIG. 3  is a schematic top view of the HVPE chamber of  FIG. 1 . 
           [0014]      FIG. 4  is another schematic cross sectional view of the HVPE chamber of  FIG. 1 . 
           [0015]      FIG. 5  is a schematic cross sectional view of an HVPE chamber according to another embodiment of the invention. 
           [0016]      FIG. 6  is a schematic cross sectional view of an HVPE chamber according to another embodiment of the invention. 
           [0017]      FIG. 7A  is a schematic cross sectional view of the gas manifold according to one embodiment of the invention. 
           [0018]      FIG. 7B  is a schematic view of the gas manifold of  FIG. 7A . 
           [0019]      FIG. 8A  is a schematic cross sectional view of the gas manifold according to another embodiment of the invention. 
           [0020]      FIG. 8B  is a schematic view of the gas manifold of  FIG. 8A . 
           [0021]      FIG. 9  is a schematic cross sectional view of an HVPE chamber according to another embodiment of the invention. 
       
    
    
       [0022]    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 and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. 
         [0023]    It is to be noted, however, that the appended drawings illustrate only exemplary 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. 
       DETAILED DESCRIPTION 
       [0024]    The present invention generally comprises a HVPE deposition method and apparatus.  FIG. 1  is a schematic cross sectional view of an HVPE chamber that may be used to practice the invention according to one embodiment of the invention. Exemplary chambers that may be adapted to practice the present invention are described in U.S. patent application Ser. Nos. 11/411,672 and 11/404,516, both of which are incorporated by reference in their entireties. Another design that may be adapted to practice the present invention includes an EPI RP 200 mm chamber, available from Applied Materials, Santa Clara, Calif. 
         [0025]    The apparatus  100  in  FIG. 1  comprises a chamber body  102  that encloses a processing area. A substrate carrier  114  is disposed within the chamber body  102 . The substrate carrier  114  may comprise one or more recesses  116  within which one or more substrates may be disposed during processing. The substrate carrier  114  may carry six or more substrates. In one embodiment, the substrate carrier  114  carries eight substrates. It is to be understood that more or less substrates may be carried on the substrate carrier  114 . In certain embodiments, the substrates may comprise sapphire. In other embodiments, the substrates may comprise SiC, silicon, or GaN. It is to be understood that other types of substrates, including glass substrates, may be processed. In one embodiment, the substrate carrier  114  may be about 200 mm in diameter. In another embodiment, the substrate carrier  114  may be about 300 mm in diameter. In one embodiment, the substrates may be about one inch to about 4 inches in diameter. In another embodiment, the substrates may be about 2 inches in diameter. It is to be understood that substrates of other sizes may be processed within the apparatus  100  and according to the processes described herein. The substrate carrier  114  may rotate about its central axis during processing. In one embodiment, the substrates may be individually rotated within the substrate carrier  114 . The substrate carrier  114  may comprise silicon carbide. 
         [0026]    A plurality of lamps  130   a,    130   b  may be disposed both above and below the substrate carrier  114 . In certain embodiments, the lamps may be arranged in concentric circles. For example, the inner array of lamps  130   b  may comprise eight lamps, and the outer array of lamps  130   a  may comprise twelve lamps. It is understood that other arrangements and other numbers of lamps are possible. The arrays of lamps  130   a,    130   b  may be selectively powered to heat the inner and outer areas of the substrate carrier  114 . In one embodiment, the lamps  130   a,    130   b  are collectively powered as inner and outer arrays in which the top and bottom arrays are either collectively powered or separately powered. In another embodiment, the lamps  130   a,    130   b  are each individually powered. In yet another embodiment, separate lamps or heating elements may be positioned over and/or under the source boat  118 . It is to be understood that the invention is not restricted to the use of arrays of lamps. Any suitable heating source may be utilized to ensure that the proper temperature is adequately applied to the processing chamber, substrates therein, and metal source  122 . For example, it is contemplated that a rapid thermal processing lamp system may be utilized such as is described in United States Patent Publication No. 2006/0018639 A1, which is incorporated by reference in its entirety. 
         [0027]    The metal source  122  may be disposed within a source boat  118  adjacent to the processing area within the chamber body  102 . The source boat  118  is disposed within the processing area above the substrate carrier  114 . The source boat  118  is disposed outside of the recess  116  where the substrates rest. The source boat  118  may be formed of quartz. The source boat  118  may be enclosed by a cover  120 . The cover  120  may comprise a baffle  132  that extends into a cavity of the source boat  118 . In yet another embodiment, multiple baffles  132  may extend from the cover  120 . The baffles  132  may be of different shape or extend different distances from the cover  120 . The baffles  120  may be arranged to create a labyrinth through which gas may pass. A gas passage  128  may be present adjacent the metal source  122  within the source boat  118  to permit passage of a gas. A gas manifold  124  may be disposed adjacent the source boat  118 . 
         [0028]      FIG. 2A  is a schematic perspective view of the HVPE chamber of  FIG. 1 . The substrate carrier  114  may be positioned within the apparatus  100  on a susceptor (not shown) through a slot  238  present in the chamber body  102  by a positioning robot (not shown). The substrates may be disposed on the substrate carrier  114  adjacent the source boat  118 . As shown in  FIG. 2B , the source boat  118  may have a plurality of openings  236  in the wall bounding the gas passage  128 . The openings  236  may be evenly spaced along the gas passage  128  as shown by the arrows “A” to permit an even flow of gas through the source boat  118 . The source boat  118  may be disposed adjacent a gas manifold  234  having a passage  240  through which purge gas may be provided. In one embodiment, the plurality of openings  236  may be disposed below the surface of the metal source  122  so that the gas bubbles up through the metal source  122 . 
         [0029]      FIG. 3  is a schematic top view of the HVPE chamber of  FIG. 1 . Hydride gas may be provided to the source boat  118  from a chlorine containing gas source  304  through a gas inlet  302  into the passage  128  (shown in  FIG. 1 ). A nitrogen precursor may be provided to the source boat  118  through a gas inlet  302  into the gas manifold  124  from a gas source  306 . Purge gas may be provided to the gas manifold  234  from a purge gas source  308 . The temperature of the metal source  122  may be monitored by a thermocouple  326 . In one embodiment, the gas source  306  may be coupled with the gas manifold  234  disposed adjacent the source boat  118 . In one embodiment, the nitrogen precursor may instead be hydrogen gas or a mixture of hydrogen gas and nitrogen precursor. In one embodiment, the purge gases may comprise nitrogen, hydrogen, and mixtures thereof. Additionally, argon may be provided with the hydrogen and/or nitrogen for both the purge gas and the gas from source  306 . 
         [0030]    Diametrically opposite the source boat  118 , a chamber exhaust  310  may be present. By placing the chamber exhaust  310  diametrically opposite the source boat  118 , gases introduced in an area near the source boat  118  will flow across the deposition surface  312  of the substrates  31 . 6  disposed on the substrate carrier  114 . 
         [0031]    As may be seen in  FIG. 3 , the source boat  118  does not extend over the substrates  316  on the substrate carrier  114 . By disposing the source boat  118  adjacent the substrate carrier  114 , the source boat  118  does not interfere with substrate  316  insertion or removal. Additionally, the source boat  118  does not interfere with gas flow across and/or perpendicular to the substrates  316 . 
         [0032]      FIG. 4  is another schematic cross sectional view of the HVPE chamber of  FIG. 1 . The source boat  118  may comprise a cavity  418  within which the metal source  122  may be disposed. The cavity  418  may be bound by a plurality of walls  404 ,  406 . One of the walls  406  may have a height “B” which is shorter than the height “C” of another wall  404 . The shorter wall  406  may be disposed on the side of the source boat  118  adjacent to the substrate carrier  114 . The shorter wall  406  permits a space  410  to be present between the cover  120  and the source boat  118 . The space  410  permits passage of gas out of the source boat  118  and over a lip  412  to the substrate carrier  114 . 
         [0033]    Inert gas fed into the manifold  234  may flow through a conduit  416  to the top plate  416  where the inert gas may flow out of a plurality of openings  420 . The nitrogen precursor may be fed through the gas manifold  124  and into the chamber body  102  through a gas inlet  408 . 
         [0034]    The process may be used to deposit various metal nitride layers including GaN, AlN, InN, AlGaN, and InGaN. During processing, the substrates are initially positioned in the chamber body  102  through the slot  238  (see  FIG. 2A ). The chamber may be maintained at a chamber pressure of about 760 Torr down to about 100 Torr. In one embodiment, the chamber is maintained at a pressure of about 450 Torr to about 760 Torr. The metal source  122  is positioned within the source boat  118  while chlorine containing gas, purge gas, and nitrogen precursor are provided to the chamber. 
         [0035]    The metal source  122  may be previously disposed within the source boat  118  or supplied on an “as needed” basis to the source boat  118  from a metal supply  328 . In one embodiment, the metal source  122  may comprise gallium, aluminum, indium, and combinations thereof. The substrate carrier  112  may be rotated. In one embodiment, the substrate carrier  114  may be rotated at about 2 RPM to about 100 RPM. In another embodiment, the substrate carrier  114  may be rotated at about 30 RPM. Rotating the substrate carrier  114  aids in providing uniform exposure of the processing gases to each substrate  316 . 
         [0036]    In the embodiment where the metal source is not provided from the metal supply  326  disposed outside the chamber, it is preferable that the amount of metal source  122  within the cavity  418  of the source boat  118  be sufficient to ensure a significant amount of substrates may be processed before the apparatus  100  would need to be opened to replenish the metal source  122 . Whenever the apparatus is opened to ambient air, it may take about 1 day to about 2 days of downtime before the apparatus is ready to process substrates again due to pumping times, chamber cleaning, and metal source purifying. Whenever the metal source  122  is exposed to atmospheric air, it may prematurely react with the oxygen in the air to form a metal oxide such as GaO on the surface of the liquid metal. The metal oxide forms a “skin” over the liquid metal that prevents the liquid metal from reacting with the nitrogen precursor to form the metal chloride. Thus, all traces of oxygen need to be removed before the further processing. The downtime between processing may be significant if sufficient metal source  122  is not initially provided to the source boat  118 . Therefore, the size and shape of the source boat  118  as well as the amount of metal source  122  positioned within the cavity  418  of the source boat  118  should be predetermined to ensure an optimal level of substrate throughput. 
         [0037]    One or more lamps  103   a,    130   b  may be powered to heat the substrates as well as the source boat  118 . The lamps may heat the substrate to about 1,000 degrees Celsius to about 1,100 degrees Celsius. In another embodiment, the lamps  130   a,    130   b  maintain the metal source  122  within the source boat  118  at a temperature of about 700 degrees Celsius to about 900 degrees Celsius. A thermocouple  326  may be positioned to measure the metal source  122  temperature during processing. The temperature measured by the thermocouple may be fed back to a controller that adjusts the heat provided from the heating lamps  130   a,    130   b  so that the temperature of the metal source  122  may be controlled or adjusted as necessary. 
         [0038]    A hydride gas may be provided from a hydride gas source  304  to the gas inlet  302  in the source boat  118 . The hydride gas may include a precursor gas such as HX where X may include chlorine, bromine, or iodine. The hydride gas flows through the gas passage  128  and through the openings  236  in the wall  404  of the source boat  118 . The even spacing of the openings  236  in the wall  404  permits the chlorine containing gas to flow evenly into the cavity  418  of the source boat  118 . When the gas comprises chlorine, the hydride gas reacts with the metal source to form a metal chloride and hydrogen gas. In one embodiment, the hydride gas comprises HCl. 
         [0039]    The HCl flows into the cavity  418  where a baffle  132  alters the flow path of the HCl (shown by arrows “F”) through the source boat  118 . By altering the flow path of the HCl through the cavity  418 , the residence time that the metal source  122  is exposed to the HCl may be increased. By increasing the residence time, the amount of metal and HCl converted to metal chloride and hydrogen is increased. 
         [0040]    In one embodiment, the HCl is provided to the source boat  118  at a rate of about 50 sccm to about 2 slm. In another embodiment, the HCl may be provided with a carrier gas. The carrier gas may comprise nitrogen gas or hydrogen gas or an inert gas. The carrier gas may be provided at a flow rate of about 0 slm to about 1 slm. The flow rate of the HCl and the carrier gas together may be about 500 sccm to about 1 slm. 
         [0041]    In another embodiment, the cover  120  may have one or more holes therein. The HCl would then be fed, either additionally or alternatively, through the holes within the cover  120  to the cavity  418  where it may then react with the metal source  122 . The holes may be designed to control the direction of the flow of the HCl into the cavity  418  so that the residence time of the HCl within the cavity  418  may be maximized. 
         [0042]    Once the metal source  122  and the HCl react to form the metal chloride and hydrogen gas, the gases then flow over the short wall  406  of the source boat  118  through the opening  410  between the short wall  406  and the cover  120 . The gases then travel down between the short wall  406  and the cover  120  to a lip  412  of the source boat  118 . The lip  412  alters the flow path of the gases so that the gases exit the source boat  118  and cover  120  to flow substantially tangential to the deposition surface of the substrates. 
         [0043]    A nitrogen precursor may be provided from gas source  306  to the chamber body  102  through the gas manifold  124 . In one embodiment, the nitrogen precursor may comprise ammonia. The ammonia may exit the gas manifold  124  through an opening  408  disposed under the source boat  118  and flow in a direction substantially tangential to the substrates as shown by arrow “G”. By flowing the ammonia under the source boat  118 , the ammonia and the metal chloride may not contact each other and prematurely react to deposit on undesired surfaces. If the ammonia is co-flowed with the HCl through the source boat  118 , the metal chloride and the ammonia may react within the source boat and thus deposit on an undesired surface. In one embodiment, the ammonia is provided to the processing area at a rate of about  1  slm to about  15  slm. In another embodiment, the ammonia may be co-flowed with a carrier gas such as those described above. 
         [0044]    Purge gas may be provided to the chamber body  102  from the purge gas source  308 . In one embodiment, the purge gas may be an inert gas such as argon or helium. In another embodiment the purge gas may comprise hydrogen gas or nitrogen gas. The purge gas travels from the purge gas source  308  to the gas manifold  234  and then through the conduit  416  to the top plate  414  where the purge gas exhausts through openings  420  that are disposed to provide the purge gas to the chamber body in a direction perpendicular to the axis of rotation of the substrates as shown by arrows “E”. The purge gas also flow out the top of the top plate  414  as shown by arrows “D”. The purge gas prevents the metal nitride from depositing on upper portions of the chamber. 
         [0045]    The openings  420  permit the purge gas to flow perpendicular to the axis of rotation the substrates. The openings  420  enable the metal chloride gas and the nitrogen containing gas to flow across the chamber. The purge gas pushes the metal chloride gas and the nitrogen precursor downward towards the substrates so that the nitrogen precursor and the metal chloride gas flow substantially tangential to the deposition surface of the substrates as shown by the arrows “H”. The chamber exhaust channels  310  additionally pull the metal chloride gas and the nitrogen precursor across the deposition surfaces. Thus, the combination of the direction of the purge gas flow and the exhaust help flow the nitrogen precursor and the metal chloride gas tangential to the deposition surface of the substrates. In one embodiment, the nitrogen precursor may be co-flowed with the purge gas through the top plate  414  and out the openings  420  so that the purge gas and the nitrogen precursor flow into the processing area in a direction substantially perpendicular to the axis of rotation for the substrates. 
         [0046]    As all of the gases are provided to the chamber, the purge gases push the nitrogen precursor and metal chloride gases down towards the rotating substrates. The flow of the metal chloride and the nitrogen precursor is substantially tangential to the deposition surface of the substrates due to the direction of flow of the purge gas and the pull of the gases by the chamber exhaust. As the nitrogen precursor and the metal chloride travel across the chamber and react, a metal nitride may be deposited onto the substrates. The metal nitride may deposit on the substrates at a rate of about 5 microns per hour to about 25 microns per hour. In one embodiment, the deposition rate is about 15 microns per hour to about 25 microns per hour. 
         [0047]    In one embodiment, the top plate  414  may be sloped. As may be seen in  FIG. 5 , the sloped top plate  414  introduces the purge gas to flow through the openings  420  and enter the processing space closer to the substrates. Additionally, by sloping the top plate  414 , the metal chloride and the nitrogen precursor may be further confined to the area above the substrates. 
         [0048]    In another embodiment, the metal source may be moved outside the processing chamber.  FIG. 6  shows an embodiment where the metal source  602  is disposed outside the processing chamber. One advantage of disposing the metal source outside the chamber is that the metal source may be replenished without the need to open the chamber. By not opening the chamber, process downtime may be reduced. When the metal source  602  is disposed outside the processing chamber, the metal source  602  may comprise a container  604  housing a boat  606  within which the metal  608  will be disposed. A lid  610  of the container  604  may comprise one or more baffles  612  as discussed above in other embodiments. The hydride vapor may be fed to the container through a conduit  614  and the metal chloride may exit the metal source  602  through a conduit  616  to enter the processing chamber. 
         [0049]    When the metal source is disposed outside the chamber, the metal chloride may pass through the same gas manifold  124  as the nitrogen precursor. As shown in  FIG. 7A , the nitrogen precursor may enter the manifold through a conduit  702  and exit the manifold into the processing chamber through a gas inlet  706 . The metal chloride may exit the gas manifold  124  and into the processing chamber through a gas inlet  704 . As may be seen in  FIG. 7B , the gas inlets  704  for the metal chloride gas may be disposed above the gas inlets  706  for the nitrogen precursor. It should be understood that the gas inlets could be reversed so that the gas inlets  706  for the nitrogen precursor are disposed above the gas inlets  704  for the metal chloride. Alternatively, gas inlets  802  for the nitrogen precursor and the metal chloride  804  may be disposed side by side as shown in  FIGS. 8A and 8B . It should be understood that the gas inlets  802 ,  804  may be disposed in one or more rows across the face of the gas manifold  124 . To ensure the metal chloride and the nitrogen precursor effectively react and deposit onto the substrates, the gas inlets  704 ,  706 ,  802 ,  804  may be disposed about one inch away from the substrate carrier. In another embodiment, the gas inlets  704 ,  706 ,  802 ,  804  may be disposed about one inch away from the substrates. 
         [0050]    In another embodiment of the invention, the boat  118  may be fed with metal source from an outside source  902  on an as needed basis.  FIG. 9  shows a supplemental source  902  disposed outside the chamber. Whenever the metal source  122  needs to be replenished, additional metal may be provided to the boat  118  from the supplemental source  902 . The supplemental source  902  may be provided with its own heating system to ensure the metal is maintained at the desired temperature. The supplemental source  902  may be gravity fed to the boat  118  by opening one or more valves  904  along a conduit  906  to the boat  118  to allow the affects of gravity to permit the metal to flow to the boat  118  inside the processing chamber. In one embodiment, the metal source may be injected into the boat  118  from a supplemental source  902 . 
         [0051]    A source boat disposed within a processing chamber capable of processing multiple substrates simultaneously may be beneficial in increasing substrate throughput. Directing the metal chloride and nitrogen containing gases to flow substantially tangential to the deposition surface of the substrate increases efficiency of HVPE deposition so that multiple substrates may be processed simultaneously. 
         [0052]    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.