Abstract:
A chemical vapor deposition reactor for depositing a thin film on at least a substrate through a reaction between a vertical input reagent gas flow and the at least a substrate is provided, in which a vertical output reagent gas flow is produced after the reaction. The reactor includes a vertical tube, at least a reaction chamber located inside the vertical tube, an input flow baffle located on the at least a reaction chamber, and at least a gas exit installed on the at least a reaction chamber for exhausting the vertical input reagent gas flow and the vertical output reagent gas flow. In addition, the substrate is located at the bottom of the at least a reaction chamber. The provided reactors allow the achievement of more efficient heating process, lower gas consumption and higher growth uniformity than the conventional reactors.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to a reactor, and more particularly to a chemical vapor deposition reactor.  
         BACKGROUND OF THE INVENTION  
         [0002]    Chemical vapor deposition is a thin film deposition technique about using a method of depositing a solid product onto a chip surface from reactants by a chemical reaction in a reactor. The reactants are usually gas reactants. After decades of developments, the chemical vapor deposition has become the most important and the main deposition method in the semiconductor manufacturing process for depositing a thin film on the semiconductor elements, such as conductors, semiconductors, and dielectric materials.  
           [0003]    The key equipment of the facilities for chemical vapor deposition is a reactor, where is the place for deposing a thin film. However, the designs for chemical vapor deposition reactors are different from one another according to their application scopes. A Hydrogen Vapor Phase Epitaxy reactor, HVPE reactor, is one of the popular chemical vapor decomposition reactors.  
           [0004]    The conventional HVPE reactors for growth of compound semiconductors of IV and III-V groups of periodical table and their alloys are well-known in the industry. These reactors can be divided into three main groups according to their geometrical features. The three main groups are respectively HVPE reactors with horizontal geometry of gas flow (HG HVPE reactors), HVPE reactors with vertical geometry of gas flow (VG HVPE reactors), and HVPE reactors with close shower head (SH HVPE reactors).  
           [0005]    Please refer to FIG. 1, which shows a structural diagram of a prior HG HVPE reactor. As shown in FIG. 1, the HG HVPE reactor includes a horizontal tube  11 , a horizontal reagent gas flow  12 , a substrate  13 , and a gas heater  14 . A hydride thin film is deposited on the substrate  13  through a reaction of the horizontal reagent gas flow  12  in the HG HVPE reactor. The relevant structures and features of HG HVPE reactors are disclosed in U.S. Pat. Nos. 6,176,925, 6,177,292, 6,179,913 and 6,350,666.  
           [0006]    The disadvantages of above-mentioned HG HVPE reactors include: 1. It&#39;s difficult to obtain a high efficiency of gas utilization and high growth uniformity of the thin film simultaneously. 2. A big gas heater  14  with high power consumption is necessary to avoid the temperature gradients inside the horizontal tube  11 . 3. Because it is difficult to obtain the temperature difference between the reactor inside walls and the substrate  13 , a deposition material will be deposited onto the reactor inside walls. 4. Because of the high relaxation times of temperature and gas flow rate changes, a Quantum Well structure, QW structure, is unable to be grown. 5. Because the symmetry of the reactor is low, it is difficult to control and model the growth processes of the thin film.  
           [0007]    Please refer to FIG. 2, which shows a structural diagram of a prior VG HVPE reactor. As shown in FIG. 2, the VG HVPE reactor includes a vertical tube  21 , a vertical reagent gas flow  22 , a substrate  23 , and a gas heater  24 . A hydride thin film is deposited on the substrate  23  through a reaction of the vertical reagent gas flow  22  in the VG HVPE reactor. The relevant structures and features of VG HVPE reactors are disclosed in U.S. Pat. Nos. 5,980,632 and 6,086,673.  
           [0008]    The disadvantages of above-mentioned VG HVPE reactors include: 1. The growth uniformity of the thin film is not yet ideal enough. 2. A big gas heater  24  with high power consumption is still necessary to avoid the temperature gradients inside the vertical tube  21 . 3. Because it is still difficult to obtain the temperature difference between the reactor inside walls and the substrate  23 , a deposition material will be deposited onto the reactor inside walls. 4. Because of the high relaxation times of temperature and gas flow rate changes, a Quantum Well structure, QW structure, is either unable to be grown.  
           [0009]    Please refer to FIG. 3, which shows a structural diagram of a prior SH HVPE reactor. As shown in FIG. 3, the SH HVPE reactor includes a horizontal tube  31 , a vertical reagent gas flow  32 , a substrate  33 , a gas heater  34 , and a shower-type head  35 . A hydride thin film is deposited on the substrate  33  through a reaction of the vertical reagent gas flow  32  in the SH HVPE reactor. The SH HVPE reactor further includes a horizontal gas flow  36  as a buffer gas. The relevant structures and features of SH HVPE reactors are disclosed in U.S. Pat. No. 4,574,093.  
           [0010]    The disadvantages of above-mentioned SH HVPE reactors include: 1. The sprinkle nozzle  35  is a non-technological design, so that the sprinkle nozzle  35  is difficult to be fabricated practically. 2. Because it is difficult to obtain the temperature difference between the reactor inside walls and the substrate  33 , deposition materials are deposited onto the reactor inside walls and the sprinkle nozzle  35 .  
           [0011]    As above-mentioned, a HVPE reactor with the abilities of high efficiency of gas utilization and high growth uniformity of thin film, which avoids the erroneous deposition, is worthy for the relevant industries.  
           [0012]    Because of the technical defects described above, the applicant keeps on carving unflaggingly to develop a “CHEMICAL VAPOR DEPOSITION REACTOR” through wholehearted experience and research.  
         SUMMARY OF THE INVENTION  
         [0013]    It is an object of the present invention to provide a HVPE reactor with the advantages of being able to obtain high efficiencies of gas utilization and high growth uniformity of the thin film simultaneously.  
           [0014]    It is another object of the present invention to provide a HVPE reactor with opposite direction flow geometry and extended diffusion layer. Also, a quantum well structure can be formed on a semiconductor material in the HVPE reactor.  
           [0015]    It is the other object of the present invention to provide a HVPE reactor with a small volume and low power consumption.  
           [0016]    In accordance with one aspect of the present invention, a reactor is provided for depositing a thin film on at least a substrate through a reaction between a vertical input reagent gas flow and the at least a substrate. A vertical output reagent gas flow is produced after the reaction. The reactor includes a vertical tube, at least a reaction chamber located inside the vertical tube, an input flow baffle located on the at least a reaction chamber, and at least a gas exit installed on the at least a reaction chamber for exhausting the vertical input reagent gas flow and the vertical output reagent gas flow. In addition, the substrate is located at the bottom of the at least a reaction chamber.  
           [0017]    Preferably, the reactor is a hydride vapor deposition reactor.  
           [0018]    Preferably, the input flow baffle is located on a top of the at least a reaction chamber.  
           [0019]    Preferably, the at least a gas exit is installed on a side wall of the at least a reaction chamber.  
           [0020]    Preferably, the reactor is made of a material selected from a group consisting of steel, quartz, sapphire, and ceramics.  
           [0021]    Preferably, the vertical input reagent gas flow is a mixture of HCl, GaCl, NH 3 , and Ar gases.  
           [0022]    Preferably, the substrate is a sapphire substrate.  
           [0023]    Preferably, the thin film is one compound semiconductor selected from a group consisting of IV group and their alloys, III-V groups and their alloys, and GaN.  
           [0024]    Preferably, the vertical output reagent gas flow is a mixture of HCl, GaCl, Cl 2 , NH 3 , and H 2  gases.  
           [0025]    Preferably, the reactor further has an extended diffusion layer formed from a bottom of the reaction chamber to the gas exit for increasing a utility rate of the vertical input reagent gas flow and a deposition unity.  
           [0026]    Preferably, the vertical tube includes a first gas heater and a second gas heater.  
           [0027]    Preferably, the first gas heater is one of an external side wall gas heater and an internal side wall gas heater.  
           [0028]    Preferably, the second gas heater controls a temperature difference between the substrate and walls of the reactor.  
           [0029]    Preferably, the second gas heater is an external bottom gas heater.  
           [0030]    Preferably, the second gas heater includes an input gas tube and a heater.  
           [0031]    Preferably, the reaction chamber is a cylindrical chamber.  
           [0032]    Preferably, the reactor further includes an extended diffusion layer for transport of the vertical input reagent gas flow to the substrate.  
           [0033]    In accordance with another aspect of the present invention, a hydride vapor deposition reactor is provided for depositing a thin film on a substrate through a reaction between a vertical input reagent gas flow and the substrate. A vertical output reagent gas flow is produced after the reaction. The reactor includes a vertical tube with two side wall gas heaters and a bottom gas heater, a plurality of first input flow baffles located inside the vertical tube for extending routes of the vertical input reagent gas flow and the vertical output reagent gas flow, a reaction chamber located inside the vertical tube and upon the substrate, at least a second input flow baffle located on a top of the reaction chamber, and at least a gas exit installed on a side wall of the reaction chamber for exhausting the vertical input reagent gas flow and the vertical output reagent gas flow.  
           [0034]    Preferably, the thin film is one compound semiconductor selected form a group consisting of III-V groups and their alloys, IV groups and their alloys, and GaN.  
           [0035]    Preferably, the two side wall gas heaters are a first gas heater and a second gas heater respectively located on external side walls of the vertical tube.  
           [0036]    Preferably, the vertical tube further includes a Ga vessel.  
           [0037]    Preferably, the reactor further includes an extended diffusion layer formed from a bottom of the reaction chamber to the gas exit for increasing a utility rate of the vertical input reagent gas flow and a deposition unity.  
           [0038]    Preferably, the plural first input flow baffles are located above the reaction chamber.  
           [0039]    For understanding this application further, some figures and detailed illustrations are shown as follows: 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0040]    [0040]FIG. 1 shows a structural diagram of a prior HG HVPE reactor;  
         [0041]    [0041]FIG. 2 shows a structural diagram of a prior VG HVPE reactor;  
         [0042]    [0042]FIG. 3 shows a structural diagram of a prior SH HVPE reactor;  
         [0043]    [0043]FIG. 4 shows a structural diagram of the HVPE reactor according to a preferred embodiment I of the present invention;  
         [0044]    [0044]FIG. 5 shows a structural diagram of the HVPE reactor according to a preferred embodiment II of the present invention;  
         [0045]    [0045]FIG. 6 shows a structural diagram of the HVPE reactor according to a preferred embodiment III of the present invention;  
         [0046]    [0046]FIG. 7 shows a structural diagram of the HVPE reactor according to a preferred embodiment IV of the present invention;  
         [0047]    [0047]FIG. 8 shows a structural diagram of the HVPE reactor according to a preferred embodiment V of the present invention; and  
         [0048]    [0048]FIG. 9 shows a structural diagram of the HVPE reactor according to a preferred embodiment VI of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0049]    The present invention provides HVPE reactors with opposite direction flow geometries and extended diffusion layers. And, a quantum well structure can be formed on a semiconductor material in the HVPE reactor.  
         [0050]    Please refer to FIG. 4, which shows a structural diagram of a HVPE reactor according to the preferred embodiment I of the present invention. As shown in FIG. 4, the HVPE reactor includes a vertical tube  41 , a first gas heater  45 , a second gas heater  46 , a reaction chamber  47 , at least an input flow diaphragm  49 , and at least a gas exist slit  410 . The reaction chamber  47  includes a container space  48 . And, a substrate  43  for being deposited thereon is positioned at the bottom of the container space  48 .  
         [0051]    The first gas heater  45  is positioned on the external side wall of the vertical tube  41 , and the second gas heater  46  is positioned at the external bottom wall of the vertical tube  41 . The reaction chamber  47  is located inside the vertical tube  41  and is a cylindrical reaction chamber. The input flow diaphragm  49  is positioned on the top of the reaction chamber  47 , and the at least a gas exist slit  410  is located on the internal side wall of the reaction chamber  47  with a particular distance from the substrate  43 . An extended diffusion layer  411  is formed between the height of the at least a gas exist slit  410  and the bottom of the reaction chamber  47 . The reaction chamber  47  is made of a material selected from a group consisting of steel, quartz, sapphire, and ceramics. The substrate  43  is a sapphire substrate.  
         [0052]    The HVPE reactor of the preferred embodiment I is used for depositing the thin film  412  on the substrate  43  by a reaction between the vertical input reagent gas flow  42  and the substrate  43 . And, an opposite-direction vertical output reagent gas flow  44  is produced after the reaction. The vertical input reagent gas flow  42  and the vertical output reagent gas flow  44  can be exhausted through the gas exist slit  410 .  
         [0053]    The vertical input reagent gas flow  42  is a mixture of HCl, GaCl, NH 3 , and Ar gases. The thin film  412  is a compound semiconductor selected from a group consisting of III-V groups and their alloys, IV group and their alloys, and GaN. The vertical output reagent gas flow  44  is a mixture of HCl, GaCl, NH 3 , Ar, and H 2  gases. And, the second gas heater  46  is used for controlling the temperature difference between the substrate  43  and the internal side walls of the reactor.  
         [0054]    On the other hand, the substrate  43  is not directly reacted with the vertical input reagent gas flow  42 . The reaction is proceeded during the diffusion process of the vertical input reagent gas flow  42  in the extended diffusion layer  411 . Meanwhile, the vertical input reagent gas flow  42  is still in a gas state during the diffusion process. Because the second gas heater  46  can be used to control the temperature difference between the internal side walls of the reactor and the substrate  43 , no deposition will be formed on the internal side walls of the reactor.  
         [0055]    Therefore, the advantage of the reactor according to the preferred embodiment I is that the first gas heater  45  and the second gas heater  46  are not necessary to be sealed up, because they are not directly exposed to the vertical input reagent gas flow  42  and the vertical output reagent gas flow  44 . This reduces the reactor volume effectively.  
         [0056]    Please refer to FIG. 5, which shows a structural diagram of a HVPE reactor according to the preferred embodiment II of the present invention. As shown in FIG. 5, the HVPE reactor includes a vertical tube  51 , a first gas heater  55 , a second gas heater  56 , a reaction chamber  57 , at least an input flow diaphragm  59 , and at least a gas exist slit  510 . The reaction chamber  57  includes a container space  58 . And, a substrate  53  for being deposited thereon is positioned at the bottom of the container space  58 .  
         [0057]    The first gas heater  55  is positioned on the internal side wall of the vertical tube  51  and upon the input flow diaphragm  59 . The second gas heater  56  is positioned at the external bottom of the vertical tube  51 . The reaction chamber  57  is located inside the vertical tube  51  and is a cylindrical reaction chamber. The input flow diaphragm  59  is positioned on the top of the reaction chamber  57 , and the at least a gas exist slit  510  is located on the internal side wall of the reaction chamber  57  with a particular distance from the substrate  53 . An extended diffusion layer  511  is formed from the height of the at least a gas exist slit  510  to the bottom of the reaction chamber  57 . The reaction chamber  57  is made of a material selected from a group consisting of steel, quartz, sapphire, and ceramics. The substrate  53  is a sapphire substrate.  
         [0058]    The HVPE reactor of the preferred embodiment II is used for depositing a thin film  512  on the substrate  53  by a reaction between the vertical input reagent gas flow  52  and the substrate  53 . And, an opposite-direction vertical output reagent gas flow  54  is produced after the reaction. The vertical input reagent gas flow  52  and the vertical output reagent gas flow  54  can be exhausted through the gas exist slit  510 .  
         [0059]    The vertical input reagent gas flow  52  is a mixture of HCl, GaCl, NH 3 , and Ar gases. The thin film  512  is a compound semiconductor selected from a group consisting of III-V groups and their alloys, IV group and their alloys, and GaN. The vertical output reagent gas flow  54  is a mixture of HCl, GaCl, NH 3 , Ar, and H 2  gases. And, the second gas heater  56  is used for controlling the temperature difference between the substrate  53  and the internal side walls of the reactor.  
         [0060]    On the other hand, the substrate  53  is not directly reacted with the vertical input reagent gas flow  52 . The reaction is proceeded during the diffusion process of the vertical input reagent gas flow  52  in the extended diffusion layer  511 . Meanwhile, the vertical input reagent gas flow  52  is still in a gas state during the diffusion process. Because the second gas heater  56  can be used to control the temperature difference between the internal side walls of the reactor and the substrate  53 , no deposition will be formed on the internal side walls of the reactor.  
         [0061]    The first gas heater  55  is directly exposed to the vertical output reagent gas flow  54 , so that the first gas heater  55  of the HVPE reactor of the preferred embodiment II needs to be sealed up. Furthermore, the advantage of the HVPE reactor according to the preferred embodiment II is more sensitive to the temperature change than the HVPE reactor of the preferred embodiment I.  
         [0062]    Please refer to FIG. 6, which shows a structural diagram of a HVPE reactor according to the preferred embodiment III of the present invention. As shown in FIG. 6, the HVPE reactor includes a vertical tube  61 , a first gas heater  65 , a second gas heater  66 , a reaction chamber  67 , at least an input flow diaphragm  69 , and at least a gas exist slit  610 . The reaction chamber  67  includes a container space  68 . And, a substrate  63  for being deposited thereon is positioned at the bottom of the container space  68 .  
         [0063]    The first gas heater  65  is positioned on the internal side wall of the vertical tube  61  and upon the input flow diaphragm  69 . The second gas heater  66  is positioned at the external bottom of the vertical tube  61 . The reaction chamber  67  is located inside the vertical tube  61  and is a cylindrical reaction chamber. The input flow diaphragm  69  is positioned on the top of the reaction chamber  67 , and the at least a gas exist slit  610  is located on the internal side wall of the reaction chamber  67  with a particular distance from the substrate  63 . An extended diffusion layer  611  is formed from the height of the at least a gas exist slit  610  to the bottom of the reaction chamber  67 . The reaction chamber  67  is made of a material selected from a group consisting of steel, quartz, sapphire, and ceramics. The substrate  63  is a sapphire substrate.  
         [0064]    Particularly, the second gas heater  66  includes an input gas tube  612  and an internal heater  613 . A input reagent gas flow  614  is heated by the internal heater  613  while being flown through the input gas tube  612 . An output reagent gas flow  615  is formed after the heated input reagent gas flow  614  is reflected from the bottom of the substrate  63 . The input reagent gas flow  614  and the output reagent gas flow  615  are oppositely directed and thermally coupled. Because the temperature of the substrate  63  directly depends on the heated input reagent gas flow  614 , the temperature can be changed quickly.  
         [0065]    The HVPE reactor of the preferred embodiment III is used for depositing a thin film  616  on the substrate  63  by a reaction between the vertical input reagent gas flow  62  and the substrate  63 . And, an opposite-direction vertical output reagent gas flow  64  is produced after the reaction. The vertical input reagent gas flow  62  and the vertical output reagent gas flow  64  can be exhausted through the gas exist slit  610 .  
         [0066]    The vertical input reagent gas flow  62  is a mixture of HCl, GaCl, NH 3 , and Ar gases. The thin film  616  is a compound semiconductor selected from a group consisting of III-V groups and their alloys, IV group and their alloys, and GaN. The vertical output reagent gas flow  64  is a mixture of HCl, GaCl, NH 3 , Ar, and H 2  gases.  
         [0067]    In the preferred embodiment III, the substrate  63  is not directly reacted with the vertical input reagent gas flow  62 . The reaction is proceeded during the diffusion process of the vertical input reagent gas flow  62  in the extended diffusion layer  611 . And, the vertical input reagent gas flow  62  is still in a gas state during the diffusion process. The second gas heater  66  is used for controlling the temperature difference between the substrate  63  and the internal side walls of the reactor, so that no deposition will be formed on the internal side walls of the reactor.  
         [0068]    The reactors of the preferred embodiment I, II, and III are used for depositing a thin film on single substrate, so that they are not suitable for mass production. On the other hand, the following reactors of the preferred embodiment IV and V are suitable for mass production of the substrates with a thin film.  
         [0069]    Please refer to FIG. 7, which shows a structural diagram of a HVPE reactor according to the preferred embodiment IV of the present invention. As shown in FIG. 7, the HVPE reactor includes a vertical tube  71 , a first gas heater  75 , a second gas heater  76 , a reaction chamber  77 , at least an input flow diaphragm  79 , and at least a gas exist slit  710 . The reaction chamber  77  includes a container space  78 . And, the substrates  73  for being deposited thereon are positioned at the bottom of the container space  78 .  
         [0070]    The first gas heater  75  is positioned at the external side wall of the vertical tube  71 , and the second gas heater  76  is positioned on the external bottom of the vertical tube  71 . The reaction chamber  77  is located inside the vertical tube  71  and is a cylindrical reaction chamber. The input flow diaphragm  79  is positioned on the top of the reaction chamber  77 , and the at least a gas exist slit  710  is located on the internal side wall of the reaction chamber  77  with a particular distance from the substrates  73 . An extended diffusion layer  711  is formed from the height of the at least a gas exist slit  710  to the bottom of the reaction chamber  77 . The reaction chamber  77  is made of a material selected from a group consisting of steel, quartz, sapphire, and ceramics. The substrates  73  are sapphire substrates.  
         [0071]    The HVPE reactor of the preferred embodiment IV is used for depositing the thin film  712  on each of the substrates  73  by reactions between the vertical input reagent gas flow  72  and the substrates  73 . And, an opposite-direction vertical output reagent gas flow  74  is produced after each reaction. The vertical input reagent gas flow  72  and the vertical output reagent gas flow  74  can be exhausted through the gas exist slit  710 .  
         [0072]    The vertical input reagent gas flow  72  is a mixture of HCl, GaCl, NH 3 , and Ar gases. The thin film  712  is a compound semiconductor selected from a group consisting of III-V groups and their alloys, IV group and their alloys, and GaN. The vertical output reagent gas flow  74  is a mixture of HCl, GaCl, NH 3 , Ar, and H 2  gases.  
         [0073]    In the preferred embodiment IV, the substrates  73  are not directly reacted with the blowing of the vertical input reagent gas flow  72 . The reactions are proceeded during the diffusion process of the vertical input reagent gas flow  72  in the extended diffusion layer  711 . And, the vertical input reagent gas flow  72  is still in a gas state during the diffusion process. The second gas heater  76  is used for controlling the temperature difference between the substrates  73  and the internal side walls of the reactor, so that no deposition will be formed on the internal side walls of the reactor.  
         [0074]    Please refer to FIG. 8, which shows a structural diagram of a HVPE reactor according to the preferred embodiment V of the present invention. As shown in FIG. 8, the HVPE reactor includes a vertical tube  81 , a plurality of first gas heaters  85 , a plurality of second gas heaters  86 , a plurality of reaction chambers  87 , at least an input flow diaphragm  89 , and at least a gas exist slit  810 . Each of the reaction chambers  87  includes a container space  88 . And, each of the substrates  83  for being deposited thereon is positioned at the bottom of each container space  88 .  
         [0075]    The first gas heaters  85  are positioned on the external side walls of the vertical tubes  81  respectively, and the second gas heaters  86  are positioned at the external bottoms of the vertical tubes  81 . The reaction chambers  87  are respectively located inside the vertical tubes  81  and are cylindrical reaction chambers. The input flow diaphragm  89  is positioned on a top of the reaction chamber  87 , and the gas exist slit  810  is located on the internal side wall of the reaction chamber  87  with a particular distance from the height of the substrate  83 . A plurality of extended diffusion layers  811  are respectively formed from the gas exist slits  810  to the bottoms of the reaction chambers  87 . The reaction chambers  87  are made of a material selected from a group consisting of steel, quartz, sapphire, and ceramics. The substrates  83  are sapphire substrates.  
         [0076]    The HVPE reactor of the preferred embodiment V is used for respectively depositing the thin film  812  on the substrate  83  by a reaction between the vertical input reagent gas flow  82  and the substrate  83 . And, an opposite-direction vertical output reagent gas flow  84  is produced after the reaction. The vertical input reagent gas flow  82  and the vertical output reagent gas flow  84  can be exhausted through the gas exist slit  810 .  
         [0077]    The vertical input reagent gas flow  82  is a mixture of HCl, GaCl, NH 3 , and Ar gases. The thin film  812  is a compound semiconductor selected from a group consisting of III-V groups and their alloys, IV group and their alloys, and GaN. The vertical output reagent gas flow  84  is a mixture of HCl, GaCl, NH 3 , Ar, and H 2  gases.  
         [0078]    In the preferred embodiment V, the substrate  83  is not directly reacted with the vertical input reagent gas flow  82 . The reaction is proceeded during the diffusion process of the vertical input reagent gas flow  82  in the extended diffusion layer  811 . And, the vertical input reagent gas flow  82  is still in a gas state during the diffusion process. The second gas heater  86  is used for controlling the temperature difference between the substrate  83  and the internal side walls of the reactor, so that no deposition will be formed on the internal side walls of the reactor.  
         [0079]    The reactors of the preferred embodiment I, II, III, IV, and V are the main designs of the HVPE reactors in the present invention. The following reactor of the preferred embodiment VI is an extended reactor of the preferred embodiment I.  
         [0080]    Please refer to FIG. 9, which shows a structural diagram of a HVPE reactor according to the preferred embodiment VI of the present invention. As shown in FIG. 9, the HVPE reactor includes a vertical tube  91 , a first gas heater  95 , a second gas heater  914 , a third gas heater  96 , a reaction chamber  97 , at least a second input flow diaphragm  99 , a plurality of first input flow diaphragms  912 , at least a gas exist slit  910 , a Ga vessel  913 , and a water cooled flange  915 . The reaction chamber  97  includes a container space  98 . And, the substrate  93  for being deposited thereon is positioned at the bottom of the container space  98 .  
         [0081]    The first gas heater  95  is positioned on one external side wall of the vertical tube  91 , the second gas heater  914  is positioned on another external side wall of the vertical tube  91 , and the third gas heater  96  is positioned at the external bottom of the vertical tube  91 . The reaction chamber  97  is located inside the vertical tube  91  and is a cylindrical reaction chamber. The second input flow diaphragm  99  is positioned on the top of the reaction chamber  97  and upon the first input flow diaphragms  912  positioned inside the vertical tube  91 . The gas exist slit  910  is located on the internal side wall of the reaction chamber  97  with a particular distance from the substrate  93 . An extended diffusion layer  911  is formed from the height of the gas exist slit  910  to the bottom of the reaction chamber  97 . The reaction chamber  97  is made of a material selected from a group consisting of steel, quartz, sapphire, and ceramics. The substrate  93  is a sapphire substrate.  
         [0082]    The HVPE reactor of the preferred embodiment VI is used for depositing the thin film  916  on the substrate  93  by a reaction between the vertical input reagent gas flow  92  and the substrate  93 . And, an opposite-direction vertical output reagent gas flow  94  is produced after the reaction. The vertical input reagent gas flow  92  and the vertical output reagent gas flow  94  can be exhausted through the gas exist slit  910 .  
         [0083]    The vertical input reagent gas flow  92  is a mixture of HCl, GaCl, NH 3 , and Ar gases. The thin film  916  is a compound semiconductor selected from a group consisting of III-V groups and their alloys, IV group and their alloys, and GaN. The vertical output reagent gas flow  94  is a mixture of HCl, GaCl, NH 3 , Ar, and H 2  gases. The first input flow diaphragm  912  is for extending the flowing routes of the vertical input reagent gas flow  92  and the vertical output reagent gas flow  94 , and enhancing the thermal interaction between the reagent gas flow  92  and  94 . Furthermore, the volume of the reactor can be effectively reduced by the design of first input flow diaphragm  912 .  
         [0084]    In the preferred embodiment VI, the substrate  93  is not directly reacted with the vertical input reagent gas flow  92 . The reaction is proceeded during the diffusion process of the vertical input reagent gas flow  92  in the extended diffusion layer  911 . And, the vertical input reagent gas flow  92  is still in a gas state during the diffusion process. The third gas heater  96  is used for controlling the temperature difference between the substrate  93  and the internal side walls of the reactor, so that no deposition will be formed on the internal side walls of the reactor.  
         [0085]    As above-mentioned, the features of the HVPE reactors provided by the present invention include:  
         [0086]    1. The reactor has a design of a vertical input reagent gas flow and a vertical output reagent gas flow being oppositely directed and thermally coupled. The design makes the effect of the gas heating improved effectively and allows a reactor with a smaller volume. Besides, with the ability of quick responding to the changes of the temperature and the reagent gas flowing rate, the HVPE reactors are potentially suitable for the growth of quantum well structures.  
         [0087]    2. With the design of an extended diffusion layer, the input reagent gas flow can be reacted with the substrate in a gas state during the diffusion process, so that it is possible to enhance the utilization efficiency of the reagents and obtain a good growth uniformity of the thin film.  
         [0088]    3. The external bottom gas heater of the HVPE reactors according to the present invention allows the control of the temperature difference between the substrate and the internal side wall of the reactor, so that no deposition is formed on the internal side walls of the reactor.  
         [0089]    4. The reaction chamber of the present invention is a cylindrical chamber with high symmetry, so that it is easy to control the model the deposition processes.  
         [0090]    Thus, the advantages of the HVPE reactors provided by the present invention can be summarized as follows:  
         [0091]    1. Good deposition uniformity.  
         [0092]    2. High efficiency of gas reagent utilization.  
         [0093]    3. Compact design.  
         [0094]    4. Easily controlling and modeling the deposition processes due to the high symmetry.  
         [0095]    5. Possibility of using low power heater.  
         [0096]    6. Possibility of growing a QW structure.  
         [0097]    7. Possibility of suppressing the deposition on the reactor walls.  
         [0098]    While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.