JP2006173540A - Vapor growth equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent decomposition and reaction of a raw material gas, and also prevent a low temperature raw material gas from cooling a substrate and a susceptor, and supply the raw material gas to a substrate surface under an optimum temperature condition, thereby improving the film quality due to particles. Provided is a vapor phase growth apparatus capable of forming a high-quality thin film by suppressing deterioration and occurrence of a film thickness distribution due to a decrease in substrate temperature.
SOLUTION: First temperature control for controlling the temperature of a source gas introduced into a flow channel from a source gas supply unit 14 into a flow channel 15 upstream of the susceptor 11 in the source gas flow direction to be equal to or lower than its thermal decomposition temperature. A second temperature control region that provides a region 21 and controls the temperature between the first temperature control region and the susceptor to be higher than the temperature controlled by the first temperature control region and lower than the substrate heating temperature. 22 is provided.
[Selection] Figure 1

Description

  The present invention relates to a vapor phase growth apparatus. Specifically, the substrate supported on a susceptor directly or via a tray is heated to a predetermined temperature, and a source gas is allowed to flow in a direction parallel to the substrate surface. The present invention relates to a horizontal vapor phase growth apparatus for forming a semiconductor thin film, and more particularly to a vapor phase growth apparatus suitable for metal organic chemical vapor deposition (MOCVD) for growing a nitride compound semiconductor thin film such as GaN.

  A substrate supported by a susceptor is placed in a flow channel made of quartz glass or the like as a vapor phase growth apparatus for manufacturing thin films such as compound semiconductors used in light emitting devices such as light emitting diodes and laser diodes and electronic devices. The substrate is heated to a predetermined temperature via a susceptor heated by a heater, a lamp, a high-frequency induction heating coil, etc., and a gas phase source gas is allowed to flow in the flow channel in a direction parallel to the substrate surface. There is known a horizontal vapor phase growth apparatus in which a thin film is formed by causing a thermal decomposition reaction on a susceptor heated to a high temperature and depositing generated gas molecules on a substrate surface.

In such a horizontal vapor phase growth apparatus, in order to suppress the reaction between the source gases before reaching the substrate, a cooling unit for cooling the entire nozzle for supplying the source gases is provided (for example, see Patent Document 1). In order to optimize the temperature of the source gas before reaching the substrate, a heating unit is provided on the upstream side of the substrate (for example, see Patent Document 2).
Japanese Patent Laid-Open No. 10-167833 JP-A-11-74202

  However, when the raw material gas is cooled by providing a cooling unit, the upstream portion of the substrate and the susceptor is cooled by the low temperature raw material gas. Therefore, when the substrate and the susceptor are not rotated, the upstream portion of the substrate, the substrate When the susceptor is rotated, the temperature of the outer peripheral portion of the substrate is lowered, so that the film quality is deteriorated or the film thickness distribution is generated.

  Further, when the raw material gas is heated by providing a heating unit, for example, when ammonia and trimethylaluminum are used as the raw material gas, particles are generated when the temperature of the raw material gas exceeds 200 ° C., and the generated particles are contained in the thin film. There is a problem that the film quality is deteriorated by being taken in.

  Therefore, the present invention prevents decomposition and reaction of the raw material gas, prevents the low temperature raw material gas from cooling the substrate and the susceptor, and supplies the raw material gas to the substrate surface under the optimum temperature condition. An object of the present invention is to provide a vapor phase growth apparatus capable of forming a high-quality thin film while suppressing the deterioration of film quality and the occurrence of film thickness distribution due to a decrease in substrate temperature.

  In order to achieve the above object, the vapor phase growth apparatus of the present invention heats a substrate supported by a susceptor provided in a flow channel via the susceptor and flows a source gas in parallel to the substrate surface. In a vapor phase growth apparatus that performs vapor phase growth of a thin film, particularly in a vapor phase growth apparatus that performs vapor phase growth of a nitride-based compound semiconductor thin film, the flow channel is connected to the flow channel upstream of the susceptor in the flow direction of the source gas. A first temperature control region for controlling the temperature of the raw material gas introduced into the interior to be equal to or lower than its thermal decomposition temperature is provided, and the first temperature control region is controlled between the first temperature control region and the susceptor. And a second temperature control region for controlling the temperature to be lower than the heating temperature of the substrate.

  Furthermore, the vapor phase growth apparatus of the present invention is characterized in that the first temperature control region and the second temperature control region include temperature control means for adjusting the temperature of each region, and the first temperature control region Provided between the control region and the second temperature control region is a heat insulating member made of a material having a low emissivity and a high reflectance, and the heat insulating member is a plane in a direction perpendicular to the raw material gas flow direction. Or the flow channel center part is a plate-shaped member which has a curved surface which becomes convex toward the upstream of the raw material gas flow direction.

  According to the vapor phase growth apparatus of the present invention, since the source gas is controlled to be equal to or lower than the thermal decomposition temperature in the first temperature control region on the upstream side of the flow channel, the thermal decomposition of the source gas is prevented and the reaction between the source gases is also prevented. Can be prevented. Therefore, the generation of particles that deteriorate the film quality is eliminated. In addition, since the source gas is heated in the second temperature control region, the substrate is not cooled by the low temperature source gas and the film thickness distribution is not generated. By these, a homogeneous thin film can be formed.

  By providing temperature control means in the first temperature control region and the second temperature control region, each region can be controlled to an optimum temperature according to the type of the source gas. Also, by providing a heat insulating member between the two regions, the temperature of both regions can be reliably controlled to a predetermined temperature, and the temperature of the source gas is rapidly increased between the first temperature control region and the second temperature control region. Therefore, the source gas can be supplied to the substrate in a better state.

  In particular, a nitride compound semiconductor thin film that uses a source gas that is easily pyrolyzed and that heats the substrate to a high temperature can prevent the substrate gas from being thermally decomposed while also preventing the substrate from being cooled. Can be obtained efficiently.

  FIG. 1 is a sectional front view of a vapor phase growth apparatus showing a first embodiment of the present invention. The vapor phase growth apparatus supports a plurality of substrates 13 on the upper surface of the susceptor 11 via a tray 12 and grows a semiconductor thin film on the substrate surface by flowing a source gas parallel to the surface of the substrate 13. In the so-called horizontal vapor phase growth apparatus, the source gas is supplied from the source gas supply unit 14 to the substrate portion via the flow channel 15, and excess source gas or the like is discharged from the exhaust passage 16.

  The susceptor 11 is a disk-like one supported on the upper end of a susceptor support shaft 17 that rotates the susceptor 11, and a heater 18 for heating the substrate 13 to a predetermined temperature via the susceptor 11 on the back surface portion thereof. Is provided. The periphery of the susceptor 11 and the heater 18 is covered with a reflector 19 for efficiently transferring the heat of the heater 18 to the susceptor 11. In some cases, the reflector 19 is not installed. Even when the reflector 19 is installed, the temperature of the reflector 19 is quite close to that of the susceptor 11. Therefore, in the following description, the susceptor 11 includes the reflector 19.

  The upstream side of the flow channel 15 is controlled by the first temperature control region 21 for controlling the temperature of the raw material gas flowing in the flow channel 15 to be equal to or lower than the thermal decomposition temperature of the raw material gas, and the first temperature control region 21. There is provided a second temperature control region 22 for controlling the temperature to be higher than the applied temperature and lower than the heating temperature of the substrate 13 (susceptor 11). On the outside of the flow channel of the first temperature control region 21 and the second temperature control region 22, a first temperature adjusting means 23 and a second temperature adjusting means 24 each having a heater and a fluid flow path are provided, respectively. The temperature of the first temperature adjusting means 23 and the second temperature adjusting means 24 can be adjusted to a preset temperature by the first temperature control means 25 and the second temperature control means 26 using a personal computer or the like.

  The source gas (including carrier gas, doping gas, etc.) flowing into the flow channel 15 from the source gas supply unit 14 is heated or cooled by the first temperature adjusting means 23 when passing through the first temperature control region 21. Thus, the temperature is controlled to be equal to or lower than the thermal decomposition temperature of the raw material gas. For example, the temperature is controlled to 200 ° C. or lower for trimethylaluminum, 150 ° C. or lower for trimethylindium, and 300 ° C. or lower for trimethylgallium.

  The source gas that has passed through the first temperature control region 21 and has flowed into the second temperature control region 22 is heated by the second temperature adjusting means 24, is higher than the temperature of the first temperature control region 21, and The temperature is controlled to a temperature close to or lower than the heating temperature. That is, the source gas flowing into the second temperature control region 22 rapidly increases in a short time from a relatively low temperature in the first temperature control region 21 to near the temperature of the substrate 13 heated to a high temperature. Further, by dividing the first temperature control region 21 and the second temperature control region 22 linearly in a direction orthogonal to the raw material gas flow direction, a temperature distribution is generated in the gas flow width direction. Can be prevented.

  At this time, if the temperature of the source gas is made higher than the heating temperature of the substrate 13 in the second temperature control region 22, the source gas is decomposed and reacted before reaching the substrate surface, thereby causing generation of particles. The set temperature of the second temperature adjusting means 24 is normally set to the maximum set temperature up to the heating temperature of the substrate 13, but the source gas is rapidly heated to a predetermined temperature at the most downstream portion of the second temperature control region 22. When it is possible to do so, the set temperature of the second temperature adjusting means 24 may be higher than the heating temperature of the substrate 13.

  Thus, by providing the first temperature control region 21 for holding the source gas at a temperature equal to or lower than the thermal decomposition temperature on the source gas supply unit 14 side of the flow channel 15, the source gas is prevented from being thermally decomposed. Reaction between each other can be prevented, and generation of particles is eliminated. Furthermore, by providing the second temperature control region 22 that raises the source gas near the heating temperature of the substrate 13 on the susceptor 11 side of the flow channel 15, the susceptor 11 and the substrate 13 are cooled by the low-temperature source gas. Can be prevented. Thereby, decomposition | disassembly and reaction of source gas on a board | substrate can be performed smoothly, and the growth efficiency of a thin film can also be improved.

  The configuration of the vapor phase growth apparatus main body, such as the shape and structure of the susceptor 11 and the flow channel 15, the presence or absence of the tray 12, is arbitrary, and the first temperature control region 21 and the second temperature control region 22 have various configurations. It can be applied to a vapor phase growth apparatus. Further, the cooling means and the heating means in the first temperature adjusting means 23 and the second temperature adjusting means 24 are arbitrary, and appropriate means such as a heater, a heating fluid, and a cooling fluid are employed alone or in combination depending on the temperature adjustment range. can do. Further, the dimensions of the first temperature adjusting means 23 and the second temperature adjusting means 24 in the gas flow direction can be set according to various conditions such as the gas flow velocity.

  2 and 3 show a second embodiment of the present invention. FIG. 2 is a sectional front view of a vapor phase growth apparatus, and FIG. 3 is a partial sectional plan view. This embodiment shows an example in which a heat insulating member 31 is provided between the first temperature adjusting means 23 and the second temperature adjusting means 24. In the following description, the same components as those in the vapor phase growth apparatus shown in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The heat insulating member 31 is composed of a plate-like member having a plane in a direction orthogonal to the raw material gas flow direction (arrow A), and has a low emissivity, a high reflectivity, and further against the raw material gas and the like. It is made of a material having corrosion resistance and little thermal deformation at a high temperature, for example, silicon carbide, molybdenum, boron nitride, alumina ceramic or the like. Note that the plate-like member serving as the heat insulating member 31 only needs to be orthogonal to the raw material gas flow direction in a plan view, and does not have to be perpendicular to the outer surface of the flow channel 15 and may be inclined. Good.

  By providing such a heat insulating member 31, heat transfer between the first temperature control unit 23 and the second temperature control unit 24 and between the first temperature control region 21 and the second temperature control region 22 is suppressed. In addition, the downstream side of the first temperature control region 21 whose temperature is controlled by the first temperature adjusting means 23 can be prevented from being heated to a predetermined temperature or more and the source gas being thermally decomposed, and the second temperature adjusting means It is also possible to prevent the temperature from being lowered by cooling the upstream side of the second temperature control region 22 whose temperature is controlled by 24. Thereby, while being able to hold | maintain the 1st temperature control area | region 21 below the decomposition temperature of source gas reliably, the heat loss of the 1st temperature control means 23 and the 2nd temperature control means 24 can be suppressed, 1st temperature control The heating and cooling efficiency in the means 23 and the second temperature adjusting means 24 can be improved.

  As described above, the first temperature control region 21 controlled to a low temperature and the second temperature control region 22 controlled to a high temperature are provided between the source gas supply unit 14 of the flow channel 15 and the susceptor 11, and the first By disposing the heat insulating member 31 between the temperature adjusting means 23 and the second temperature adjusting means 24, a nitride-based compound semiconductor thin film that uses a source gas that is easily pyrolyzed and that heats the substrate to a high temperature is used. Also in production, since the source gas can be effectively heated by the second temperature adjusting means 24 while more reliably preventing thermal decomposition of the source gas in the first temperature control region 21, a high-quality thin film can be obtained more efficiently. be able to.

  In both embodiments, depending on the shape of the flow channel 15 and the gas flow conditions, the first temperature adjusting means 23 and the second temperature adjusting means 24 are surrounded by the flow channel 15 including the heat insulating member 31. Can be arranged.

  FIG. 4 is a diagram showing an example of the temperature state of the first temperature control region 21 depending on the presence or absence of the heat insulating member 31 made of a molybdenum plate-like member having a thickness of 1 mm. In this experiment, the various conditions including the kind of gas flowing in the flow channel 15 and the flow velocity are the same, and the comparison is made only with or without the heat insulating member 31. As can be seen from FIG. 4, by installing the heat insulating member 31, the temperature rise due to the heat transfer from the second temperature adjusting means 24 can be suppressed by 50 ° C.

  FIG. 5 is a diagram illustrating a change example of the surface temperature of the flow channel 15 when the temperature control is performed. During InGaN growth, the temperature is maintained at 150 ° C. or lower in the first temperature control region 21, and the second temperature control region 22 is rapidly heated to near 700 ° C., which is the heating temperature of the substrate 13 (susceptor 11). . During GaN growth, the temperature is maintained at 200 ° C. or lower in the first temperature control region 21, and the second temperature control region 22 is rapidly heated to near 1100 ° C. that is the heating temperature of the substrate 13 (susceptor 11). ing. By performing such temperature control, an InGaN substrate and a GaN substrate having good film quality can be efficiently manufactured.

  As the shape of the flow channel 15, an optimum shape can be selected according to the film forming conditions. For example, as shown in the schematic cross-sectional view of FIG. 6, the source gas or the like flows obliquely toward the substrate 13. It may be a thing. Further, the substrate 13 may be installed in an inclined state in which the downstream side is raised. Further, the heat insulating member 31 may not be a planar plate shape, and for example, as shown in the schematic plan view of FIG. 7, the center portion of the flow channel has a curved surface that is convex toward the upstream side in the raw material gas flow direction. The plate-like members 31a and 31b may be used, and a certain degree of effect can be obtained even if they are not provided over the entire width of the flow channel 15.

1 is a cross-sectional front view of a vapor phase growth apparatus showing a first embodiment of the present invention. It is a cross-sectional front view of the vapor phase growth apparatus showing the second embodiment of the present invention. It is a partial cross section top view similarly. It is a figure which shows an example of the temperature state of the 1st temperature control area | region by the presence or absence of a heat insulation member. It is a figure which shows the example of a change of the surface temperature of the flow channel at the time of performing temperature control. It is a schematic sectional drawing which shows the other shape example of a flow channel. It is a schematic plan view which shows the other example of a shape of a heat insulation member.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Susceptor, 12 ... Tray, 13 ... Board | substrate, 14 ... Raw material gas supply part, 15 ... Flow channel, 16 ... Exhaust passage, 17 ... Susceptor support shaft, 18 ... Heater, 19 ... Reflector, 21 ... 1st temperature control area | region , 22 ... second temperature control region, 23 ... first temperature adjustment means, 24 ... second temperature adjustment means, 25 ... first temperature control means, 26 ... second temperature control means, 31 ... heat insulation member

Claims (5)

  In a vapor phase growth apparatus that heats a substrate supported by a susceptor provided in a flow channel via the susceptor and flows a raw material gas in parallel to the substrate surface to perform vapor phase growth of a thin film, the susceptor A flow channel on the upstream side in the flow direction of the raw material gas is provided with a first temperature control region for controlling the temperature of the raw material gas introduced into the flow channel to be equal to or lower than its thermal decomposition temperature, and the first temperature control region and the above-mentioned Vapor phase growth characterized in that a second temperature control region is provided between the susceptor and a temperature controlled to be higher than the temperature controlled by the first temperature control region and lower than the heating temperature of the substrate. apparatus.   2. The vapor phase growth apparatus according to claim 1, wherein the first temperature control region and the second temperature control region include temperature control means for adjusting the temperature of each region.   The vapor phase growth according to claim 1 or 2, wherein a heat insulating member made of a material having a low emissivity and a high reflectivity is provided between the first temperature control region and the second temperature control region. apparatus.   The heat insulating member is a flat member in a direction orthogonal to the raw material gas flow direction, or a plate-like member having a curved surface in which a central portion of the flow channel is convex toward the upstream side of the raw material gas flow direction. The vapor phase growth apparatus according to claim 3.   5. The vapor phase growth apparatus according to claim 1, wherein the thin film is a nitride-based compound semiconductor thin film.

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