Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
  • C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
  • C23C16/301—AIII BV compounds, where A is Al, Ga, In or Tl and B is N, P, As, Sb or Bi
  • C23C16/303—Nitrides
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
  • C23C16/455—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating characterised by the method used for introducing gases into reaction chamber or for modifying gas flows in reaction chamber
  • C23C16/45523—Pulsed gas flow or change of composition over time
  • C23C16/45525—Atomic layer deposition [ALD]
  • C23C16/45544—Atomic layer deposition [ALD] characterized by the apparatus
  • C23C16/45548—Atomic layer deposition [ALD] characterized by the apparatus having arrangements for gas injection at different locations of the reactor for each ALD half-reaction
  • C23C16/45551—Atomic layer deposition [ALD] characterized by the apparatus having arrangements for gas injection at different locations of the reactor for each ALD half-reaction for relative movement of the substrate and the gas injectors or half-reaction reactor compartments
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
  • C30B25/02—Epitaxial-layer growth
  • C30B25/14—Feed and outlet means for the gases; Modifying the flow of the reactive gases
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
  • C30B29/10—Inorganic compounds or compositions
  • C30B29/40—AIIIBV compounds wherein A is B, Al, Ga, In or Tl and B is N, P, As, Sb or Bi
  • C30B29/403—AIII-nitrides
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/02104—Forming layers
  • H01L21/02365—Forming inorganic semiconducting materials on a substrate
  • H01L21/02518—Deposited layers
  • H01L21/02521—Materials
  • H01L21/02538—Group 13/15 materials
  • H01L21/0254—Nitrides
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/02104—Forming layers
  • H01L21/02365—Forming inorganic semiconducting materials on a substrate
  • H01L21/02612—Formation types
  • H01L21/02617—Deposition types
  • H01L21/0262—Reduction or decomposition of gaseous compounds, e.g. CVD

Definitions

• the present invention generally relates to a Metalorganic Vapor Deposition (MOCVD) method and an apparatus for growing semiconductor crystal, more particularly for fabricating Nitride-based compound semiconductors with substantially high Al content between 20% and 100%.
• MOCVD Metalorganic Vapor Deposition
• MOCVD Metal organic chemical vapor deposition
• MOCVD Metal organic chemical vapor deposition
• epitaxy growth is initiated by the thermal pyrolysis of group II or III metal-organic sources and group VI or V hydrides, with the nitrogen or hydrogen as the carrier gas, injected into the reactor with pre-determined proportions.
• group II or III metal-organic sources and group VI or V hydrides with the nitrogen or hydrogen as the carrier gas, injected into the reactor with pre-determined proportions.
• Several reaction pathways compete in both vapor phase and on the surface of hot substrate, and the metal-organic source consumption in the vapor phase is an important factor affecting the composition of the deposited film, thereby its final opto-electronic properties.
• reaction space in the reactor gas temperature, substrate temperature, gas flow field, and operating pressure, all play important roles in growing II- VI or III-V semiconductor materials and their alloys of desired properties.
• MOCVD reactor design a great deal of focus has been put forward to better control aforementioned process parameters.
• One particular area is the design of reactant gas distribution device, for its contribution to forming a uniformly mixed gaseous environment above the hot substrate where epitaxial growth takes place is believed to be essential in MOCVD process.
• AlGaN/GaN materials system is used for different purposes.
• Aluminum Gallium Nitride (AlGaN) has a direct transition band gap between 3.4 and 6.2 eV, thus it is often used as active region of UV LED, deep UV LED and UV detectors. It could also be used as buffer layer to block dislocations and relax the strains between active layers and underneath substrate to improve the device performance.
• AlGaN Aluminum Gallium Nitride
• the wavelength of the LED - the higher the Al content, the shorter the wavelength.
• the Al content over the Ga content is greater than 40%.
• the AlGaN/GaN super lattice (SL) used as buffer layers on Si substrate for LED or HEMT application the Al content is generally over 70%.
• Al composition in the epitaxial film (solid phase) grown on the hot substrate is commonly controlled by the composition in the gaseous phase, gas flow velocity, and operating pressure.
• the Al composition in the solid phase increases with that in the gaseous phaseto a point beyond which a saturation of Al content is reached.
• a MOCVD method to synthesize Group III-V nitride-based compound semiconductor crystals with high Al content comprising:
• a reactant gas distribution apparatus comprising:
• an inlet side where at least one inlet connecting to metalorganic source reactant gas feed, at least one inlet connecting to ammonia reactant gas feed, and at least one inlet connecting purge gas,
• a first gas distribution member connecting said inlet side, consisting of a gas connection channels isolating said metalorganic source reactant from said ammonia reactant and distributing reactant gases from said inlets to said reactant distributing zones;
• a plurality of second gas distribution members connecting to said outlet side, each consisting of a plurality of gas outlets and gas connection channels distributing reactant gas from each of said reactant distribution zones to gas outlets that guide reactant gas flow to exit vertically to said outlet side; at least one third gas distribution member consisting of an inlet gas switch among metalorganic source reactant gas, ammonia reactant gas, and nitrogen purge gas feed, gas flow connection channels, and an outlet gas injector that guides reactant gas flow exiting gas injector horizontally to said outlet side.
• One characteristic of this invention is that the reactants mix inhomogeneously in the gaseous environment to form a plurality of alternating zones, one rich in metalorganic source and the other rich in ammonia, immediately above the epitaxy substrates.
• This inhomogeneously mixed gaseous phase reduces parasitic reaction to only regionswhere one zone rich in metalorganic source and the other rich in ammonia meet.
• the hot epitaxy substrates continuously move under said alternating zones of reactants, passing each zone at the time scales from a few milliseconds to a few tens of milliseconds.
• compound semiconductor crystals with high Al content between 20% and 100% can be made by an economical process ata reduced consumption rate of metalorganic precursors.
• Fig. 1 illustrates the side view of part of the gas distribution apparatus
• Fig. 2 illustrates the side view of the reaction spacing between the gas distribution apparatus and the substrates
• Fig. 3a illustrates the side view of a first embodiment of the center gas injector
• Fig. 3b illustrates the side view of a second embodiment of the center gas injector
• Fig. 3c illustrates the side view of a third embodiment of the center gas injector
• Fig. 4a illustrates the bottom view of part of one embodiment of the gas distribution apparatus
• Fig. 4b illustrates the bottom view of part of another embodiment of the gas distribution apparatus
• Fig. 5a illustrates the ammonia mass fraction on the plane of the substrate surface with one distance between the gas distribution apparatus and substrates by computer simulation
• Fig. 5b illustrates the ammonia mass fraction on the plane of the substrate surface with another distance between the gas distribution apparatus and substrate by computer simulation
• Fig. 6a illustrates side view of the reaction spacing between the gas distribution apparatus and the substrates at one time
• Fig. 6b illustrates side view of the reaction spacing between the gas distribution apparatus and the substrates at another time
• Fig. 7 illustrates the ⁇ -2 ⁇ scan curve by XRD for one AlGaN sample prepared in the MOCVD apparatus
• Fig. 8 illustrates the ⁇ -2 ⁇ scan curve by XRD for another AlGaN sample prepared in the MOCVD apparatus
• Fig. 9 illustrates the chart of the Al concentration in the AlGaN films prepared at different distances between substrate surface and gas delivering device
• Fig. 10 illustrates the chart of the Al concentration in AlGaN films prepared with different Al composition in the gaseous phase.
• Fig. 1 illustrates the side view of part of the gas distribution apparatus 100 that delivering the precursors into the reaction area.
• the gas distribution apparatus 100 comprises an inlet side 110 and an outlet side 120. And there is a cooling system 130 in the gas distribution apparatus 100 at the inlet side 110. This cooling system can also be placed at outlet side 120.
• the first gas distribution member 111 comprises a gas distribution channel which isolates the metalorganic precursors from the ammonia precursor, and distributes the metalorganic precursors to a plurality of second gas distribution member 121 at the outlet side 120 of the gas distribution apparatus.
• Each of the second gas distribution members 121 for delivering metalorganic precursors comprises a plurality of gas outlets 131 to introduce metalorganic precursors into the reaction area with a vertical flow at the outlet side 120.
• the first gas distribution member for metalorganic precursors 111 and the second gas distribution members for metalorganic precursors 121 can be made in one body.
• one of the second gas distribution members 121 for delivering metalorganic precursors comprises 10 or more than 10 gas outlets 131.
• the total area of the gas outlets 131 on one of the second gas distribution members 121 for delivering metalorganic precursors is greater than 5% and less than 75% of the area of one of the second gas distribution members 121.
• the gas distribution member 112 comprises a gas distribution channel which isolates the ammonia precursor from the metalorganic precursors, and distributes the ammonia precursor to a plurality of second gas distribution members 122 at the outlet side 120 of the gas distribution apparatus.
• Each of the second gas distribution members 122 for delivering ammonia precursor comprises a plurality of gas outlets 132 to introduce ammonia precursor into the reaction area with a vertical flow at the outlet side 120.
• the first gas distribution member for ammonia 112 and the second gas distribution members for ammonia 122 can be made in one body.
• one of the second gas distribution members 122 for delivering ammonia precursor comprises 10 or more than 10 gas outlets 132.
• the total area of the gas outlets 132 on one of the second gas distribution members 122 for delivering ammonia precursor is greater than 5% and less than 75% of the area of one of the second gas distribution members 122.
• the second gas distribution members 121 for delivering metalorganic precursors and the second gas distribution members 122 for delivering ammonia precursor are adjacent to each other.
• the metalorganic precursors with the carrier gas are delivered vertically into the reaction spacing 201 between the gas distribution apparatus 100 and the substrates 210, as shown in Fig. 2, by a plurality of second gas distribution members 121, thereby forming a plurality of zones 141 rich in metalorganic precursors.
• the ammonia precursor with carrier gas is delivered vertically into the reaction spacing 201 between the gas distribution apparatus 100 and the substrates 210, as shown in Fig. 2, by a plurality of second gas distribution members 122, thereby forming a plurality of zones 142 rich in ammonia precursor.
• the zones 141 rich in metalorganic precursors and the zones 142 rich in ammonia precursor are adjacent to each other to form an inhomogeneous gaseous environment in the reaction spacing 201.
• the gas outlets 131 and 132 in the gas distribution apparatus 100 can be straight holes, tapered holes, rectangular slits or any other possible configurations that are used for gas distribution.
• the dimension of the gas outlets 131 and 132 is between 0.5 and 2mm, or larger than 2mm.
• the gas distribution apparatus 100 comprises at least one gas inlet 103 connected to a third gas distribution member 113.
• the inlet gas for the gas inlet 103 can be switched among metalorganic precursors, ammonia precursor, carrier gases and their mixtures.
• the third gas distribution member 113 is connected to at least one gas injector 123 which delivers the inlet gas into the reaction spacing 201 horizontally.
• the gas injector 123 has one slit gas flow opening around its perimeter or a plurality of separated gas flow openings, each of which is positioned in between projections of the second gas distribution members 121 and 122.
• Fig. 3a shows the side view of a first embodiment of the gas injector 123.
• the third gas distribution member 113 comprises a gas distribution channel 301 connected to the gas injector 123.
• the gas injector 123 comprises a plurality of separated openings 302 to deliver nitrogen or hydrogen to the reaction spacing 201. After the gas flows out from each of the separated gas flow openings, the gas flows into the area between zones 141 rich in metalorganic precursors and the zones 142 rich in ammonia, thereby prohibitingdirect mixing of gas flows from gas outlets 131 and 132.
• Fig. 3b shows the side view of a second embodiment of the gas injector 123.
• the third gas distribution member 113 comprises a gas distribution channel 311 connected to the gas injector 123.
• the gas injector 123 comprises a slit opening around its perimeter to deliver the metalorganic precursors or the ammonia precursor with carrier gas into the reaction area 210.
• gas flows out from the slit gas flow opening around the perimeter of gas injector 123 an uniform gas layer is formed immediately outside of the injector, and this layer of uniform gas flow aids mixing between gas vertical gas flows from gas outlets 131 and 132.
• Fig. 3c shows the side view of a third embodiment of the gas injector 123, with a combination of the first and second embodiments of the gas injector 123 shown in Fig. 3a and 3b.
• the third gas distribution member 113 comprises a first gas distribution channel 321 to introduce nitrogen or hydrogen to the first layer of the gas injector 1231 and a second gas distribution channel 323 to introduce metalorganic precursors or ammonia precursor with carrier gas to the second layer of the gas injector 1232.
• the first layer of the gas injector 1231 comprises a plurality of separated openings 322 to deliver nitrogen or hydrogen to the reaction spacing 201 to inhibit direct mixing of gas flows from gas outlets 131 and 132.
• the second layer of the gas injector 1232 comprises a slit opening around its perimeter to deliver the metalorganic precursors or the ammonia precursor with carrier gas into the reaction area 210 to aid mixing between vertical gas flows from gas outlets 131 and 132.
• the gas flow out from the opening 322 and that from 324 can be controlled independently.
• the gas distribution apparatus is made of graphite or graphite coated with protective layer, silicon carbide, stainless steel or any other material which is compatible for the MOCVD process.
• the substrates are made from one of A1203, Si, SiC, AIN, AlGaN or InAlGaN.
• Fig. 4a illustrates the bottom view of part of one embodiment of the gas distribution apparatus 100.
• the second gas distribution members 121 for delivering metalorganic precursors and the second gas distribution members 122 for delivering ammonia precursor have a fan shape and are adjacent to each other.
• the gas injector 123 is at the center of bottom side of the gas distribution apparatus 100.
• the gas injector 123 can be one of the embodiments illustrated in Fig. 3a to 3c, or any other configurations without departing from the invention.
• the second gas distribution members 121 deliver the metalorganic precursors into the reaction spacing 201 vertically and form the zones rich in metalorganic precursors 141.
• the concentration of metalorganic precursor in the zones rich in metalorganic precursors 141 is more than 1.2 times of that of the average concentration of metalorganic precursors in the whole reaction spacing 201.
• the total volumetric gaseous flow rate through each of the zones rich in metalorganic precursors 141 is between 0.2 to lOL/min.
• the second gas distribution members 122 deliver the ammonia precursor into the reaction spacing 201 vertically and form the zones rich in ammonia precursor 142.
• the gas injector 123 delivers metalorganic precursors, ammonia precursor, nitrogen, hydrogen or a mixture of the above gases into the reaction area horizontally.
• the concentration of ammonia precursor in the zones rich in ammonia precursors 142 is more than 1.2 times of that of the average concentration of ammonia precursors in the whole reaction spacing 201.
• the total volumetric gaseous flow rate through each of the zones rich in ammonia reactant 142 is between 0.15 to 8L/min.
• the zones rich in metalorganic precursors 141 constitutes between 15% and 85% of the reaction spacing 201.
• the computer simulation by ANSYS FLUENT was carried out to estimate the ammonia mass fraction on the plane of the substrate surfaces with one embodiment of the gas distribution apparatus 100 with a small distance between the gas distribution member 100 and the substrates 210, as shown in Fig. 5a.
• the mass fraction of ammonia in the zones 142 rich in ammonia precursor is 0.9, while that in the zones 141 rich in metalorganic precursor is 0.3. It can be concluded that the zones 142 rich in ammonia precursor contain majority of ammonia reactant within the reaction spacing 201 and the zones 141 rich in metalorganic precursors contain majority of metalorganic reactant within the reaction spacing 201, which indicate an inhomogeneous mixing of ammonia and metalorganic precursors.
• Fig. 5b illustrates the ammonia mass fraction on the plane of the substrate surface with a large distance between gas distribution apparatus and the substrate by computer simulation.
• the mass fraction of ammonia in the zones 142 rich in ammonia precursor is 0.8, while that in the zones 141 rich in metalorganic precursor is 0.5.
• the concentration of ammonia precursor in the zones rich in ammonia 142 is 1.23 times of the average ammonia concentration in the whole reaction spacing 201.
• the Al concentration in the fabricated nitride-based semiconductor compound can be controlled by controlling the distance between the gas distribution apparatus 100 and the substrates 210.
• Fig. 4b illustrates the bottom view of part of another alternative embodiment of the gas distribution apparatus 100.
• a plurality of second gas distribution members 121 for delivering metalorganic precursors and a plurality of second gas distribution members 122 for delivering ammonia precursor have a fan shape and are adjacent to each other.
• a plurality of gas injectors 123 are in between the second gas distribution members 121 and 122. And the gas injectors 123 can be one of the embodiments illustrated in Fig. 3a to 3c, or any other configuration without departing from the invention.
• the gas distribution members 121 deliver the metalorganic precursors into the reaction spacing 201 vertically and form the zones rich in metalorganic precursors 141.
• the second gas distribution members 122 deliver the ammonia precursor into the reaction spacing 201 vertically and form the zones rich in ammonia precursor 142.
• the gas injectors 123 deliver metalorganic precursors, ammonia precursor, nitrogen, hydrogen or a mixture of the above gases into the reaction area horizontally.
• the substrates 210 are heated between 500 and 1350C and the pressure in the reaction space 210 is 50 to 800mbar.
• the metalorganic precursor and ammonia are introduced into the reaction space 210 by the gas distribution apparatus 100.
• a plurality of alternating zones 141 rich in metalorganic precursor and a plurality of alternating zones 142 rich in ammonia are formed.
• the substrates 210 are rotated around an axis with 1 to 300rpm and are exposed to one of the alternating zones 141 rich in metalorganic precursor and in contact with the majority of the metalorganic precursor before and after they are exposed to one of the alternating zones 142 rich in ammonia and in contact with the majority of ammonia with the rotation of the substrate holding device.
• the metalorganic precursor and ammonia react and form a layer of semiconductor compound with high Al content on the substrate surface.
• An exemplary procedure is shown in Fig. 6a and 6b.
• substrate 210a is under one of the second gas distribution member 121 delivering metalorganic precursors and substrate 210b is under one of the second gas distribution member 122 delivering ammonia precursor.
• the substrates 210a and 210b have a relative motion to the gas distribution apparatus 100 in a time period t2-tl.
• substrate 210a is under one of the second gas distribution member 122 delivering ammonia precursor
• substrate 210b is under one of the second gas distribution member 121 delivering metalorganic precursors.
• the substrates 210a and 210b are exposed to one of the alternating zones 141 rich in metalorganic precursor and in contact with the majority of the metalorganic precursor before and after they are exposed to one of the alternating zones 142 rich in ammonia and in contact with the majority of ammonia with the rotation of the substrate holding device.
• the metalorganic precursor and ammonia react and form a layer of semiconductor compound with high Al content on the substrate surface.
• the time period t2-tl is determined by the speed of the relative motion between the substrates 210 and the gas distribution apparatus 100 and the area of the second gas distribution member 121 and 122. In one embodiment of the invention, the time period t2-tl is longer than 4ms. In another embodiment of the invention, the relative motion between substrates 210 and gas distribution apparatus 100 is a kind of translational motion with a translational velocity less than 13m/s.
• the gas feed of either metalorganic precursor or ammonia to the gas injector 123 is closed and an inhomogeneous gaseous environment is formed.
• the substrates 210 are exposed to one of the alternating zones 141 rich in metalorganic precursor and in contact with the majority of the metalorganic precursor before or after they are exposed to one of the alternating zones 142 rich in ammonia and in contact with the majority of ammonia to form a layer of semiconductor compound with high Al content on the substrate surface.
• the Al content is further increased when gas feed of nitrogen, serving as a separation gas, to the separated openings of the flow injector is open and separation gas flows into the area between zones rich in metalorganic precursors and the zones rich in ammonia, reducing the mixing of the two zones.
• the gas feed of either metalorganic precursor or ammonia is open to feed to the slit opening around the perimeter of the gas injector 123 to aid mixing between gas vertical gas flows from gas outlets 131 and 132 and a more homogeneous gaseous environment is formed.
• One example of the high Al content semiconductor compound was prepared with the disclosed method and gas distribution apparatus 100.
• the ⁇ -2 ⁇ scan of XRD of the prepared AlGaN film is illustrated in Fig. 7.
• the temperature of the substrate surfaces was between 500 to 1350°C and the pressure in the reaction spacing 201 was between 50 to 800mbar.
• the metalorganic precursors were, but not limited to, TMGa and TMA1.
• the Al concentration is defined as the molar concentration of Al divided by the molar concentration of total group III metal sources.
• the Al concentration in the gaseous phase was 34.4%, and the Al concentration in the AlGaN film was estimated as 52.6% based on the XRD result, which was much higher than that in the gas phase.
• the utilization of Al source is defined as the Al concentration in the synthesized solid semiconductor compound divided by the Al concentration in the gaseous phase, and in this case the utilization of Al source is larger than 1.5.
• FIG. 8 Another example of the high Al content semiconductor compound was prepared with the disclosed method.
• the temperature of the substrate surfaces was between 500 to 1350°C and the pressure in the reaction spacing 201 was between 50 to 800mbar.
• the metalorganic precursors were, but not limited to, TMGa and TMAL.
• the ⁇ -2 ⁇ scan by XRD of the prepared AlGaN films is illustrated in Fig. 8.
• Two layers of AlGaN were prepared in the sample with different Al concentration in each layer, by adjusting the Al concentration in the gas phase.
• the Al concentration in the gas phase for preparing the layer with low incorporated Al concentration is 19%, while that for the one with high incorporated Al concentration is 48.5%.
• the ⁇ -2 ⁇ scan of XRD of the AlGaN sample showed two peaks for AlGaN, indicating an AlGaN layer with low incorporated Al concentration as 31.5% and another with high incorporated Al concentration as 80.2%, both of which are higher than that in the gas phase.
• the utilization of Al source is larger than 1.5 for both low and high Al content semiconductor compound layers.
• Fig. 9 illustrates the Al concentration in the exemplary AlGaN films prepared in the reaction spacing 201 with the method disclosed in this invention at different distances between the substrate 210 surfaces and the gas distribution apparatus 100. It showed that the Al concentration in the AlGaN film decreased when the distance between the substrate 210 surface and the gas distribution apparatus 100 became larger. When the distance between the gas distribution apparatus 100 and the substrates 210 became larger, the metalorganic precursors and the ammonia had a more homogeneous mixing due to longer diffusion distance. More metalorganic precursor reacted and was consumed with the ammonia in the gas phase, while less reached to the substrate 210 surfaces to form a layer of solid semiconductor compound, leading to a lower Al concentration in the layer. This indicates that the inhomogeneous mixing of ammonia and metalorganic precursors helps for preventing gas phase parasitic reaction and preparing the semiconductor compound with high Al content between 20% and 100% with the disclosed method.
• Fig. 10 illustrates the Al concentration in the exemplary AlGaN films prepared in the reaction spacing 201 with the method disclosed in this invention with different Al concentration in the gas phase. It showed that Al concentration in the AlGaN film increased with that in the gas phase, and it is higher than that in the gas phase.
• This high incorporation rate of Al into the AlGaN film prepared with the method disclosed in this invention brings additional benefit of reducing particle formation brought about by gas phase reaction between Al metalorganic precursor and ammonia.
• the particle formation in the gas phase is a seriousproblem in commercial MOCVD reactors when being applied to growing Al containing nitride-based compound semiconductors. These particles, when migrating from gas phase to solid AlGaN, cause defects and low yield in the final devices.
• the disclosed method and apparatus can also be used to synthesis A1N, AlInN, AlInGaN or any other nitride based semiconductor compound with high Al content between 20% and 100%, by applying different metalorganic precursors such as, but not limit to TMGa, TEGa, TMA1 and TMIn.

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• 2012
  • 2012-07-19 WO PCT/CN2012/078899 patent/WO2014012237A1/en active Application Filing
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