JP2008166397A - Vapor phase growth device and vapor phase growth method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To permit stably the supply of material gas into a reaction tube by eliminating pressure fluctuation in run-side piping which can be generated upon switching a flow passage in a run/vent system. <P>SOLUTION: The vapor phase growth device for effecting flow passage switching employs a gas supply route to the reaction tube 1 i.e., a run line 2 and a gas exhaust route, i.e., vent line 3 to make dummy gas to flow into the vent line 3 while making the material gas to flow into the run line 2 or to make the dummy gas to flow through the run line 2 while making the material gas to flow through the vent line 3. Also, it comprises a fluctuation detecting means 12 for detecting the pressure fluctuation of the run line 2 caused by the switching of the flow passage, a storing means 22 for storing the detecting result of the fluctuation detecting means 12 and a sequential control means 23 for effecting the flow regulation of gas in the run line 2 based on a storing content of the storing means 22 in synchronization with the timing of flow switching are provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a vapor phase growth apparatus and a vapor phase growth method for performing film formation by vapor phase growth.

  When two or more types of crystal structures are continuously grown by vapor phase growth, a source gas necessary for the first crystal layer is supplied into a reaction tube for film formation by the vapor phase growth, and then The source gas may be switched to that required for the second crystal layer. As a vapor phase growth apparatus suitable for growing such two or more types of crystal structures, a so-called run / vent type apparatus is known (for example, see Patent Documents 1 and 2).

  FIG. 4 is an explanatory view showing a configuration example of a conventional run / vent type vapor phase growth apparatus. As shown in the figure, the run / vent type vapor phase growth apparatus includes a run line 2 connected to the reaction tube 1 and a vent line 3 bypassing the reaction tube 1. A raw material line 6 connected to a raw material gas supply mechanism 5 is connected to the run line 2 and the vent line 3 via a flow path switching mechanism 4. By switching the flow path in the flow path switching mechanism 4, the raw material line 6 is communicated with the run line 2 at the time of vapor phase growth, and communicated with the vent line 3 when the vapor phase growth is stopped. As a result, the run line 2 functions as a supply path for the source gas to the reaction tube 1 and the vent line 3 functions as an exhaust path for the source gas. A dummy line 7 provided corresponding to each of the raw material lines 6 is also connected to the run line 2 and the vent line 3 via a flow path switching mechanism 4. In the dummy line 7, a gas having the same flow rate as that of the gas in the corresponding raw material line 6 is usually flowed. By switching the flow path in the flow path switching mechanism 4, the dummy line 7 is connected to the vent line 3 when the corresponding raw material line 6 is connected to the run line 2, and conversely, the raw material line 6 is connected to the vent line 3. When it is done, it communicates with the run line 2. With such a configuration, in the run / vent type vapor phase growth apparatus, at the moment when the supply of the raw material gas to the reaction tube 1 is switched, the previous raw material gas is quickly exhausted and the vapor phase growth reaction is completed immediately. However, only the vapor phase growth reaction based on the newly supplied source gas of another kind starts to proceed immediately.

By the way, in the run / vent type vapor phase growth apparatus, even if the type of the raw material gas supplied to the reaction tube 1 is changed by the channel switching in the channel switching mechanism 4, the supply gas to the reaction tube 1 is changed. Therefore, it is necessary to control the gas flow rate so that the gas pressure does not fluctuate in the reaction tube 1 or in the piping.
However, in the run line 2 and the vent line 3, a differential pressure is generated when the flow path is switched in the flow path switching mechanism 4 due to a difference in the viscosity of the flowing gas. If the flow path is switched in a situation where such a pressure difference occurs, there is a difference in the ease of flow between the high pressure side and the low pressure side, so that stable gas supply to the reaction tube 1 becomes impossible. There is a fear.
Therefore, in the conventional run / vent type vapor phase growth apparatus, the pressure difference between the run line 2 and the vent line 3 is detected in real time by the differential pressure gauge 12 or the like, and the detection signal is sent to the vent line 3. The pressure difference between the run line 2 and the vent line 3 is canceled by changing the gas flow rate in the vent line 3 using the MFC 9 that is sent to the mass flow controller (hereinafter abbreviated as “MFC”) 9 provided. Some are configured to perform so-called feedback control.

JP-A-4-324623 JP-A-8-288226

  However, in the run / vent type vapor phase growth apparatus that performs feedback control, for example, as shown in FIG. 5, the flow rate of the MFC 9 oscillates in order to converge the pressure difference between the run line 2 and the vent line 3. Change. Therefore, it takes about several seconds to converge the pressure difference. Therefore, for example, when considering the case of growing a thin film whose growth time is shorter than the pressure convergence time, in that case, the composition and film thickness at the time of film formation by vapor phase growth may not be obtained as intended. There is.

  Further, in the conventional feedback control described above, the gas flow rate in the vent line 3 is controlled using the MFC 9 provided on the vent line 3, so that the run line 2 connected to the reaction tube 1 in which the reaction is actually performed is performed. Pressure fluctuations cannot be controlled. Therefore, since the pressure change on the run line 2 side occurs during the growth, there is a possibility that the supply of the raw material gas to the reaction tube 1 is not stably performed.

  Therefore, the present invention eliminates the pressure fluctuation in the run side pipe that may occur when the flow path is switched in the run / vent system, makes it possible to stably supply the source gas into the reaction tube, and continuously at a short interval. To provide a vapor phase growth apparatus and a vapor phase growth method capable of growing a steep interface in a reaction tube without taking time to converge the flow rate even when the flow path is switched. With the goal.

  The present invention is a vapor phase growth apparatus devised to achieve the above object. That is, it is necessary for the vapor phase growth, a reaction tube for film formation by vapor phase growth, a run line that functions as a gas supply path to the reaction tube, a vent line that functions as an exhaust path for the gas, and Vapor phase growth comprising switching means for switching between flowing a dummy gas to the vent line while flowing a raw material gas to the run line, or switching the dummy gas to flow to the run line while flowing the raw material gas to the vent line In the apparatus, the fluctuation value detecting means for detecting the fluctuation value of the gas flow rate in the run line caused by the flow path switching by the switching means, the fluctuation value detected by the fluctuation value detecting means, or the fluctuation value uniquely. A storage means for storing a correction value that can be derived, and a change stored by the storage means at a flow path switching timing by the switching means. Based on the value or the correction value, characterized in that it comprises a sequential control unit for adjusting the gas flow rate in the run line so as to cancel the fluctuation value.

  The present invention is also a vapor phase growth method devised to achieve the above object. That is, using a run line that functions as a gas supply path to the reaction tube and a vent line that functions as an exhaust path for the gas, a dummy gas is allowed to flow through the vent line while flowing a source gas to the run line, or In the vapor phase growth method in which film formation is performed by vapor phase growth in the reaction tube by switching the flow path of flowing the dummy gas to the run line while flowing the source gas to the vent line, A change detection step for switching the flow path under the same conditions as when forming a film and detecting pressure fluctuation or gas flow fluctuation in the run line caused by the flow path change, and detection in the fluctuation detection step A storage step for storing a result or a value that can be uniquely derived from the detection result, and a flow path for film formation by vapor deposition Characterized in that it comprises a sequential control step of adjusting the gas flow rate in the run line based on a stored content by said storing step in accordance with the Rikae timing.

  In the vapor phase growth apparatus configured as described above and the vapor phase growth method according to the above procedure, the gas flow rate in the run line is adjusted instead of the vent line side, so the gas supply into the reaction tube can be stabilized directly. become. In addition, pressure fluctuations or gas flow fluctuations are detected in advance, and so-called sequential control is performed on the gas flow in the run line when film formation by vapor phase growth is performed using the detection result. . Therefore, the gas flow rate is adjusted in accordance with the flow channel switching timing, and the time required for the gas supply to the reaction tube to be stabilized after the flow channel switching depends on the detection result of the pressure fluctuation or the gas flow fluctuation. This is shorter than when feedback control is performed.

  According to the present invention, by directly stabilizing the gas supply into the reaction tube, pressure fluctuations in the run-side piping that may occur when switching the flow path in the run / vent system are eliminated, and the raw material gas is stabilized. Therefore, it is possible to achieve good film formation by vapor phase growth in the reaction tube. In addition, since the gas flow rate in the run line is controlled sequentially using the detection result of pressure fluctuation or gas flow rate fluctuation in advance, the flow rate to be adjusted according to the flow path switching timing can be instantly determined. Compared to such feedback control, the time until the gas supply is stabilized can be shortened. Therefore, the flow path can be switched continuously at short intervals, so the composition and film thickness at the time of film formation by vapor phase growth can be obtained as intended, and as a result, sharp interface growth is realized in the reaction tube. It becomes possible to do.

  Hereinafter, a vapor phase growth apparatus and a vapor phase growth method according to the present invention will be described with reference to the drawings.

  First, a schematic configuration example of the vapor phase growth apparatus will be described. FIG. 1 is an explanatory diagram showing a configuration example of a vapor phase growth apparatus according to the present invention. In addition, in the figure, the same code | symbol is attached | subjected about the component similar to the conventional thing (refer FIG. 4).

  As shown in FIG. 1, the vapor phase growth apparatus described as an example in this embodiment includes a run line 2 that functions as a gas supply path to a reaction tube 1 for performing film formation by vapor phase growth, It is of a run / vent type provided with a vent line 3 that functions as an exhaust path for the gas. The run line 2 and the vent line 3 are provided with a flow path switching mechanism 4 made of, for example, an electromagnetic valve, and the flow path switching mechanism 4 is a source gas necessary for vapor phase growth in the reaction tube 1, That is, while the source gas from the source line 6 connected to the source gas supply mechanism 5 is caused to flow to the run line 2, the dummy gas from the dummy line 7 corresponding to the source line 6 is allowed to flow to the vent line 3 or from the source line 6. The source gas is allowed to flow to the vent line 3 while the dummy gas from the dummy line 7 is switched to the run line 2.

  As the source gas supply mechanism 5, it is conceivable to use an organic metal, a gas source, or the like. By supplying the source gas from the supply mechanism 5 to the reaction tube 1, film formation for forming, for example, a III-V group compound semiconductor can be performed in the reaction tube 1. More specifically, it is possible to form a group III-V compound semiconductor functioning as a laser light emitting element by performing film formation, for example, by metal organic chemical vapor deposition in the reaction tube 1.

  In order to carry the raw material gas from the supply mechanism 5 into the reaction tube 1, a carrier gas flows through the run line 2. For example, hydrogen gas may be used as the carrier gas, but the carrier gas is not limited thereto. Further, it is assumed that the same carrier gas flows not only in the run line 2 but also in the vent line 3.

  Further, the run line 2 is provided with an MFC 8 for adjusting the gas flow rate in the run line 2 upstream of the flow path switching mechanism 4 in the gas flow direction. Similarly, it is conceivable to provide the MFC 9 on the vent line 3 as well, but the MFC 9 in the vent line 3 is not essential. The same applies to the MFCs 10 and 11 in the raw material line 6 and the dummy line 7.

  Further, the run line 2 is caused by the flow path switching by the flow path switching mechanism 4 on the downstream side in the gas flow direction from the flow path switching mechanism 4 and on the upstream side in the gas flow direction from the reaction tube 1. A pressure gauge 12 for detecting pressure fluctuations in the run line 2 is provided. The pressure gauge 12 may be a differential pressure gauge that detects the pressure difference between the run line 2 and the vent line 3 in real time. An absolute pressure gauge is attached to the run line 2 to detect the absolute pressure measured by the absolute pressure gauge. As a result. Moreover, the structure which takes the difference of an absolute pressure gauge may be sufficient. That is, the pressure gauge 12 only needs to be able to detect the pressure fluctuation of the gas supplied to the reaction tube 1. The pressure fluctuation is detected by the fact that the pressure fluctuation in the run line 2 and the fluctuation of the gas flow rate uniquely correspond to each other, using the ideal gas equation of state, the law of conservation of mass, etc., or using the feedback control described later This is because the fluctuation value of the gas flow rate can be derived from the pressure fluctuation value. This is because, instead of the pressure gauge 12, a flow meter is provided in the run line 2 and the vent line 3, and the total flow rate of each is monitored to identify the fluctuation value of the gas flow rate in the run line 2, or the pressure It means that the fluctuation value of the gas flow rate in the run line 2 may be specified by using a meter and a flow meter together. That is, a means for detecting at least one of pressure fluctuation or gas flow fluctuation in the run line 2 may be provided between the flow path switching mechanism 4 and the reaction tube 1 on the run line 2. It should be noted that the pressure gauge 12 as an example of means for detecting such fluctuations in the run line 2 has the detection result connected to the pressure gauge 12 via a wired or wireless communication line. It comes to notify.

  The control unit 20 has a function as a computer device that executes a predetermined program, realized by a combination of a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and the like. By executing the predetermined program, it functions as the feedback control means 21, the storage means 22, and the sequential control means 23.

The feedback control means 21 gives an operation instruction to the MFC 8 provided on the run line 2 in order to adjust the gas flow rate in the run line 2 so as to cancel the pressure fluctuation detected by the pressure gauge 12. It is. That is, the feedback control means 21 performs feedback control so that the gas flow rate from the run line 2 into the reaction tube 1 is always constant based on the detection result by the pressure gauge 12. In addition, since it is sufficient to use a known technique for the feedback control itself, the description thereof is omitted here.
Further, the feedback control means 21 obtains the value of the gas flow rate fluctuation in the run line 2 through the feedback control. That is, in the feedback control means 21, the gas flow rate adjustment amount of the gas flow rate in the MFC 8 for canceling the pressure fluctuation detected by the pressure gauge 12 is changed to the gas flow rate in the run line 2 caused by the flow path switching mechanism 4. Change amount.

  When the detection result from the pressure gauge 12 is notified to the control unit 20, the storage unit 22 stores and holds the detection result. The detection result here includes, in addition to the pressure fluctuation value detected by the pressure gauge 12, a value that can be uniquely derived from the pressure fluctuation value. Examples of the value that can be uniquely derived include the value of the gas flow rate fluctuation obtained by the feedback control means 21 performing feedback control based on the detection result of the pressure gauge 12, the correction value described in detail later, and the like.

  The sequential control means 23 gives a flow switching operation instruction to the flow switching mechanism 4 to continuously grow two or more types of crystal structures by vapor phase growth, and in accordance with the flow switching timing, The operation instruction based on the storage contents of the storage means 22 is given to the MFC 8 provided on the storage unit 2. That is, the sequential control means 23 performs sequential control for adjusting the gas flow rate in the run line 2 using the stored contents stored in the storage means 22 in advance.

  Next, an example of processing operation in the vapor phase growth apparatus having the above configuration, that is, a vapor phase growth method executed using the vapor phase growth apparatus will be described.

  In using the vapor phase growth apparatus, before performing the film forming process by vapor phase growth using the vapor phase growth apparatus, first, data of pressure fluctuation and flow rate fluctuation when the flow path switching mechanism 4 switches the flow path. Take.

  Data collection is performed during a sequence operation under exactly the same conditions as in the case of performing film formation by vapor phase growth. That is, the control unit 20 causes the flow path switching mechanism 4 to perform flow path switching at the same operation timing as when the film forming process is performed. Further, the gas flow rates flowing through the run line 2 and the vent line 3 as well as the raw material line 6 and the dummy line 7 are all the same as in the case of performing the film forming process. At this time, if the MFC 9 is provided in the vent line 3, the MFC 9 is used so that the gas flow rate in the vent line 3 is always constant. On the other hand, with respect to the gas flow rate in the run line 2, the feedback control means 21 gives an operation instruction to the MFC 8 on the run line 2 based on the detection result notified from the pressure gauge 12, thereby the vent line 3 The differential pressure is always set to “0”. Then, the adjustment result of the gas flow rate by the MFC 8 according to the instruction from the feedback control means 21, that is, the adjustment amount of the gas flow rate for the run line 2 is recorded using, for example, a function as a data collector in the control unit 20. To be able to do.

  Under such circumstances, when the flow path switching mechanism 4 switches the flow path at the same operation timing as when the film forming process is performed, the difference in the viscosity of the gas flowing through the run line 2 and the vent line 3 at the time of the flow path switching, etc. In order to eliminate the pressure difference, the MFC 8 adjusts the gas flow rate in the run line 2 in accordance with an instruction from the feedback control means 21. By this adjustment, the adjustment amount of the gas flow rate is recorded in time series in the data collector.

  FIG. 2 is an explanatory diagram showing a specific example of the recording result of the fluctuation amount of the gas flow rate. In the illustrated example, there is a flow path switching by the flow path switching mechanism 4 at time “0”, and in order to eliminate the differential pressure between the run line 2 and the vent line 3 due to the flow path switching, the feedback control means 21 The MFC 8 is adjusting the gas flow rate in the run line 2 while following the instructions. By this adjustment, the gas flow rate in the run line 2 increases, for example, from 0 [a.u.] to 1 [a.u.]. However, since the increase is due to feedback control, it undergoes a process of change such that it eventually stabilizes at the convergence point while vibrating.

  When the adjustment amount of the gas flow rate in the run line 2 is recorded in this way, the feedback control means 21 specifies a correction value that can be uniquely derived from the recorded result. FIG. 3 is an explanatory diagram showing a specific example of the correction value that can be uniquely derived from the gas flow rate fluctuation. For example, it is conceivable that the correction value is specified based on the difference between the value before switching the flow channel and the value when the flow rate is stable after switching the flow channel in the recording result in the data collector. Specifically, if the gas flow rate adjustment result as shown in FIG. 2 is recorded in the data collector, as shown in FIG. 3, +1 [au] at the time “0” is derived. Can be considered.

  In data acquisition, during a series of sequence operations, for all timings at which the flow path switching mechanism 4 performs flow path switching, the adjustment amount for the gas flow rate fluctuation as described above is recorded and correction values that can be uniquely derived from the adjustment amount are recorded. Identify. Of these adjustment amounts and correction values, at least the correction values are stored and held in the storage means 22 so as to be used in film formation processing by vapor phase growth performed thereafter.

  After collecting data according to such a procedure, it becomes possible to perform a film formation process by vapor phase growth using a vapor phase growth apparatus.

  When the film formation process by vapor phase growth is performed, the sequential control unit 23 does not control the feedback flow control unit 21 but the adjustment of the gas flow rate of the run line 2 by the MFC 8. That is, the sequential control means 23 gives a flow path switching operation instruction to the flow path switching mechanism 4 in order to continuously grow two or more types of crystal structures by vapor phase growth, and according to the flow path switching timing, The gas flow rate is adjusted by the MFC 8 provided on the run line 2. At this time, the sequential control unit 23 causes the MFC 8 to adjust the gas flow rate using the stored contents stored in the storage unit 22. Specifically, if the correction value shown in FIG. 3 is stored in the storage unit 22, the sequential control unit 23 increases the flow rate by +1 [au] at the time “0”. The gas flow rate adjustment in the MFC 8 is controlled. Thus, the MFC 8 instantaneously changes the gas flow rate in the run line 2 in synchronization with the flow path switching timing by the flow path switching mechanism 4.

  As described above, in the vapor phase growth apparatus and the vapor phase growth method described in the present embodiment, in order to supply gas to the reaction tube 1 stably, the gas flow rate in the run line 2 instead of the vent line 3 side. Adjust. Therefore, the gas supply into the reaction tube 1 can be directly stabilized, so that the pressure fluctuation on the side of the run line 2 that may occur when switching the flow path in the run / vent system is eliminated, and the raw material gas is stabilized. Therefore, it is possible to supply the inside of the reaction tube 1, and as a result, it is possible to achieve good film formation by vapor phase growth in the reaction tube 1.

  In addition, in the vapor phase growth apparatus and the vapor phase growth method described in the present embodiment, when adjusting the gas flow rate in the run line 2, pressure fluctuation or gas flow rate fluctuation is detected in advance, and the detection result is used. So-called sequential control is performed on the gas flow rate in the run line 2 when performing film formation by vapor phase growth. Therefore, the flow rate to be adjusted according to the flow path switching timing can be determined instantaneously, and the process of oscillation and convergence of the gas flow rate does not go through as in the case of feedback control. It takes less time to stabilize the supply. That is, the flow path can be continuously switched at a short interval, and the composition, film thickness, and the like at the time of film formation by vapor phase growth can be obtained as intended. It is possible to realize the growth of the interface.

  In addition, in the vapor phase growth apparatus and the vapor phase growth method described in the present embodiment, it is essential to collect data in advance, but the result of feedback control by the feedback control unit 21 is used at the time of data collection. . Therefore, the data can be easily acquired based on the detection result of the pressure fluctuation by the pressure gauge 12, and can be performed with high accuracy.

In addition, although this embodiment demonstrated the suitable Example of this invention, this invention is not limited to the content.
For example, the number of source lines 6 and dummy lines 7 shown in the present embodiment is not particularly limited as long as it corresponds to the number of crystal structure layers grown by vapor phase growth.
Further, the film formation process by vapor phase growth performed in the reaction tube 1 is not limited to the one for forming the III-V group compound semiconductor exemplified in the present embodiment, but other semiconductor devices. It is conceivable to apply to.
Furthermore, in this embodiment, the case where feedback control is used at the time of preliminary data acquisition and sequential control is performed at the time of subsequent vapor deposition is taken as an example. In addition to the sequential control, it is also conceivable to use feedback control by the feedback control means 21 together, thereby further improving controllability.
Thus, the present invention can be modified as appropriate without departing from the scope of the invention.

It is explanatory drawing which shows the structural example of the vapor phase growth apparatus which concerns on this invention. It is explanatory drawing which shows a specific example of the recording result of the variation | change_quantity of gas flow volume. It is explanatory drawing which shows a specific example of the correction value which can be derived | led-out uniquely from a gas flow rate fluctuation | variation. It is explanatory drawing which shows the structural example of the conventional vapor growth apparatus of a run / vent type. It is explanatory drawing which shows a specific example of the flow volume fluctuation | variation by the conventional feedback control.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Reaction tube, 2 ... Run line, 3 ... Vent line, 4 ... Flow path switching mechanism, 5 ... Supply mechanism, 6 ... Raw material line, 7 ... Dummy line, 8, 9, 10, 11 ... MFC, 12 ... Pressure 20 ... control unit, 21 ... feedback control means, 22 ... storage means, 23 ... sequential control means

Claims (4)

A reaction tube for film formation by vapor phase growth;
A run line that functions as a gas supply path to the reaction tube;
A vent line that functions as an exhaust path for the gas;
Switching means for switching between flowing a dummy gas to the vent line while flowing the source gas necessary for the vapor phase growth, or flowing the dummy gas to the run line while flowing the source gas to the vent line; In a vapor phase growth apparatus comprising:
Fluctuation detecting means for detecting pressure fluctuations or gas flow fluctuations in the run line caused by flow path switching by the switching means;
Storage means for storing a detection result by the fluctuation detection means or a value that can be uniquely derived from the detection result;
A sequential control unit that gives a flow path switching operation instruction to the switching unit and adjusts the gas flow rate in the run line based on the stored contents of the storage unit in accordance with the flow path switching timing by the switching unit. A vapor phase growth apparatus characterized by that.   A feedback control unit that adjusts the gas flow rate in the run line so as to cancel out the pressure variation detected by the variation detection unit, and obtains the value of the gas flow rate variation in the run line from the result of the adjustment; The vapor phase growth apparatus according to claim 1. Using a run line that functions as a gas supply path to the reaction tube and a vent line that functions as an exhaust path for the gas, a dummy gas is allowed to flow through the vent line while a source gas is allowed to flow into the run line, or the raw material In the vapor phase growth method of performing film formation by vapor phase growth in the reaction tube through switching the flow path of flowing the dummy gas to the run line while flowing gas to the vent line,
A change detection step of performing the flow path switching under the same conditions as when performing film formation by the vapor phase growth, and detecting a pressure fluctuation or a gas flow rate fluctuation in the run line caused by the flow path switching,
A storage step for storing a detection result in the variation detection step or a value that can be uniquely derived from the detection result;
And a sequential control step of adjusting the gas flow rate in the run line based on the storage contents of the storage step in accordance with the flow path switching timing when the film formation by the vapor phase growth is performed. Phase growth method.   And a feedback control step of adjusting the gas flow rate in the run line so as to cancel the pressure fluctuation detected in the fluctuation detection step, and obtaining a value of the gas flow rate fluctuation in the run line from the result of the adjustment. The vapor phase growth method according to claim 3.

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