JP2020064928A - Method for replacing gas in reactor in vapor phase growth apparatus - Google Patents

Abstract

To provide a method for replacing gas in a reactor in a vapor phase growth apparatus that can suppress the generation of particles and replace gas in the reactor.SOLUTION: Before a reactor 11 in a vapor phase growth apparatus is opened by operating an opening/closing lid 11a for loading and unloading a substrate, a purge gas is introduced into the reactor while continuing an exhaust operation from an exhaust unit such as a normal pressure exhaust path 22 or a vacuum exhaust path 23 that exhausts the gas in the reactor to replace the gas in the reactor with the purge gas from the reactive gas.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for replacing a gas in a reaction furnace in a vapor phase growth apparatus, and more specifically, a gas for replacing a reactive gas atmosphere in a reaction furnace with an inert gas atmosphere when a substrate is put in and out of a reaction furnace. The present invention relates to a method for replacing gas in a reaction furnace in a phase growth apparatus.

  The vapor phase growth apparatus is for growing a semiconductor crystal on the substrate by heating a substrate installed in the reaction furnace to a preset temperature and supplying a source gas into the reaction furnace. Specifically, the substrate is installed in the reaction furnace, the reactor is closed and the reactor is depressurized, the reactive gas is supplied into the reaction furnace and the substrate is heated, and the source gas is supplied while supplying the reactive gas. Stop supply of raw material gas after crystal growth, lower temperature in reaction furnace while supplying reactive gas, replace gas in reaction furnace by supplying inert gas, pressurize in reaction furnace, open reactor It is a batch-type apparatus that repeats the procedure of taking out a substrate from the reaction furnace and installing a new substrate. Further, the reaction furnace is housed in a glove box having a shape covering the reaction furnace, and by passing an inert gas such as nitrogen at a pressure higher than atmospheric pressure into the glove box, To prevent the invasion of the atmosphere.

  In such a vapor phase growth apparatus, it is required to prevent particles from being mixed into the semiconductor substrate and to shorten the time required for one semiconductor crystal growth, and various measures have been conventionally proposed. For example, it is possible to suppress the generation of particles by providing a pressure equalizing valve, opening and closing a plurality of valves as appropriate to make the pressure inside the reactor equal to the pressure inside the glove box, and then opening the reactor. (For example, see Patent Document 1).

Japanese Patent No. 5079902

  However, in the vapor phase growth apparatus described in Patent Document 1, when the reaction furnace is opened, the operation of opening and closing the exhaust valve and the pressure equalizing valve is performed, so that a gas flow different from the normal time occurs, so that particles are generated. It was likely to occur. In addition, if the reaction furnace is opened in a state where the temperature inside the reaction furnace is higher than the temperature around the reaction furnace, gas convection occurs due to the temperature difference, which may cause particles to be generated. In particular, there is a possibility that more particles may be generated due to the reverse flow of the gas from the exhaust system pipe serving as the exhaust unit from the reaction furnace.

  Therefore, an object of the present invention is to provide a method for replacing gas in a reaction furnace in a vapor phase growth apparatus, which can suppress gas generation and perform gas replacement in the reaction furnace.

  In order to achieve the above object, the method for replacing the gas in the reaction furnace in the vapor phase growth apparatus of the present invention, in order to take out the substrate after film formation from the reaction furnace placed in the glove box in which the inert gas is flowing In the gas replacement method in the reaction furnace in the vapor phase growth apparatus when opening the reaction furnace, after completing the film forming operation on the substrate placed in the reaction furnace, before opening the reaction furnace, The gas in the reaction furnace is replaced with the purge gas by introducing the purge gas into the reaction furnace while continuing the exhaust operation from the exhaust unit for exhausting the gas in the reaction furnace.

  Further, in the gas replacement method in the reaction furnace in the vapor phase growth apparatus of the present invention, the exhaust part is provided with conductance adjusting means for adjusting the conductance of the gas flowing through the exhaust part, and the purge gas supply part into the reaction furnace. The conductance of the exhaust part is adjusted according to the supply amount of the purge gas.

  In addition, after replacing the gas in the reaction furnace with the purge gas and increasing the pressure, it is possible to maintain the pressure in the reaction furnace equal to the pressure in the glove box without lowering the pressure in the reaction furnace before opening the reaction furnace. It has a feature.

  In particular, the vapor phase growth apparatus is a vapor phase growth apparatus for forming a compound semiconductor for forming a compound semiconductor on a substrate, and further, the vapor phase growth apparatus is a MOCVD apparatus.

  In addition, the gas in the reaction furnace is purged until the cumulative supply amount of the purge gas is larger than the internal volume of the reaction furnace and the concentration of the reactive gas discharged from the reaction furnace becomes equal to or lower than the allowable concentration. It is characterized by performing a gas replacement operation for replacing the gas.

  According to the method for replacing the gas in the reaction furnace in the vapor phase growth apparatus of the present invention, since the exhaust from the exhaust unit is continuously performed, the back flow of gas from the exhaust pipe constituting the exhaust unit is not generated. Moreover, the generation of particles can be suppressed, and the particles can be prevented from entering the reaction furnace.

It is explanatory drawing which shows one form example of the vapor phase growth apparatus which can implement the substitution method of the gas in a reaction furnace in the vapor phase growth apparatus of this invention. It is explanatory drawing which shows the state during film-forming operation in a reaction furnace. It is explanatory drawing which similarly shows the state which opened the reaction furnace. It is a flow chart which shows an example of the program for gas substitution in the substitution method of the gas in the reaction furnace in the vapor phase growth device of the present invention. FIG. 3 is a diagram showing an example of supply states of a purge gas and a reactive gas into the reaction furnace and a temperature change and a pressure change in the reaction furnace in one film forming operation.

  1 to 5 are views for explaining a method for replacing a gas in a reaction furnace in a vapor phase growth apparatus of the present invention, and FIG. 1 is an example of one embodiment of a vapor phase growth apparatus in which the present invention can be carried out. Is shown. The vapor phase growth apparatus shown in this embodiment includes a reaction furnace 11 for growing a semiconductor crystal on a substrate, a glove box 12 that covers the reaction furnace 11, and a plurality of reaction furnaces 11 and a plurality of glove boxes 12 connected to the glove box 12, respectively. It has a gas supply system and a gas exhaust system.

  The gas supply system includes a reactor supply gas supply path 15 for supplying various gases to the reaction furnace 11 through a supply valve 13 and a flow rate controller 14 for a purge gas and a reactive gas, and a nitrogen supply valve 16 for supplying nitrogen gas. And a glove box gas supply path 17 for supplying the gas into the glove box 12. Usually, an inert gas such as nitrogen or argon is used as the purge gas, and the reactive gas is a gas used when growing a semiconductor crystal on a substrate, and is a gas depending on the type of the semiconductor crystal. , Hydrogen, ammonia, silicon compounds, organometallic compounds and the like are used.

  The gas exhaust system of the glove box 12 is provided with a glove box gas exhaust path 20 for exhausting nitrogen gas from the inside of the glove box 12 via an opening / closing valve 18 and an automatic valve 19, and the automatic valve 19 is a glove box. The opening degree is adjusted according to the pressure detected by the glove box pressure gauge 21 that detects the pressure inside the box 12, and the pressure inside the glove box 12 is adjusted to a pressure slightly higher than the atmospheric pressure so that the inside of the glove box 12 is adjusted from the outside. We are trying to prevent the invasion of the atmosphere into.

  On the other hand, the gas exhaust system of the reaction furnace 11 includes a normal pressure exhaust path 22 and a vacuum exhaust path 23 for exhausting gas from the reaction furnace 11, and the normal pressure exhaust path 22 includes the reaction furnace 11 in the normal pressure exhaust path 22. A normal pressure exhaust valve 24 is provided which opens when the internal pressure rises to normal pressure. Further, the vacuum exhaust path 23 is provided with a vacuum pump 25 for reducing the pressure inside the reaction furnace 11, a pressure reducing valve 26 that opens when the pressure inside the reaction furnace 11 is reduced, and a pressure inside the exhaust system. An exhaust adjusting valve 28 for adjusting the gas conductance in the vacuum exhaust path 22 according to the detected pressure of the exhaust pressure gauge 27 for detecting

  As shown in FIGS. 2 and 3, the reaction furnace 11 is provided with an opening / closing lid 11a for loading / unloading the substrate. As shown in FIG. 2, the opening / closing lid 11a is provided except when the substrate is loaded / unloaded. 11a is closed, and when the substrate is taken in and out, the opening / closing lid 11a is opened as shown in FIG. Normally, the inside of the reaction furnace 11 is exhausted from the gas exhaust system, and the purge gas and the reactive gas supplied into the reaction furnace 11 are exhausted from the normal pressure exhaust path 22 and / or the vacuum exhaust path 23. There is. When the opening / closing lid 11a is opened with the gas exhaust stopped, the gas in the gas exhaust system flows backward as indicated by an arrow A in FIG. 3 due to the pressure difference and the temperature difference between the gas exhaust system and the glove box 12. May occur and cause particles to be generated.

  Therefore, when the opening / closing lid 11a of the reactor 11 is opened, the opening / closing lid 11a is opened after performing a gas replacement operation incorporated in an automatic growth program for growing a semiconductor crystal on a substrate. In this gas replacement operation, as shown in FIG. 4, first, in step 51, it is confirmed whether or not only an inert gas is flowing into the reaction furnace 11 as a purge gas. If the reactive gas is being supplied into the reaction furnace 11 at this point, it means that the film forming operation is not completely completed.

  If it is confirmed in step 51 that only the inert gas is flowing into the reaction furnace 11, the process proceeds to step 52, where the inflow integrated value of the inert gas is compared with a preset specified value, and the inflow integrated value is When it exceeds the specified value, the process proceeds to step 53. The specified value is set to a value larger than the internal capacity of the reaction furnace 11, and an optimum value selected by performing simulation in advance can be set as the specified value.

  When the integrated value of the inflow of the inert gas exceeds the specified value in step 52, it is confirmed in step 53 whether the temperature of the reaction furnace 11 is lower than the temperature at which the reaction furnace lid can be opened and closed, which is 150 ° C. in the present embodiment. Then, when the temperature of the reaction furnace 11 is lower than the temperature at which the reaction furnace lid can be opened and closed, it is confirmed in step 54 that the automatic growth program is not being executed, that is, that a series of film forming operations have been completed. As a result, the opening / closing lid 11a of the reaction furnace 11 can be opened. The temperature at which the reaction furnace lid can be opened and closed is influenced by the heat-resistant temperature of the peripheral members of the reaction furnace, and is, for example, in the range of 60 to 600 ° C., but is not limited thereto.

  FIG. 5 shows changes in the temperature, pressure, and supply gas in the reaction furnace 11 per film forming operation. First, after the substrate is installed, the reaction furnace 11 is sealed with the opening / closing lid 11a, and the reaction furnace 11 is closed. The substrate is heated while the internal pressure is reduced to a predetermined film forming operation pressure (10 kPa in this example), and the inert gas (nitrogen) and the reactive gas (hydrogen, ammonia) are supplied into the reaction furnace 11. Is started (heating process). A thin film of a predetermined semiconductor crystal grows in a state where the substrate is heated to a predetermined temperature, in this case 1000 ° C. (deposition process).

  When the predetermined thin film has grown, the heating of the substrate is terminated, and the temperature inside the reaction furnace 11 is lowered while each gas is being supplied (cooling process). When the temperature in the reaction furnace 11 has dropped to a certain temperature (265 ° C. in this example), the supply of the reactive gas is stopped, and only the inert gas is supplied to the reaction furnace 11, and the reactivity in the reaction furnace 11 is reduced. Gas replacement is performed by purging the gas into an inert gas atmosphere (cooling down + replacement process).

  Then, by supplying an inert gas and reducing the vacuum exhaust amount in the reaction furnace 11, the pressure in the reaction furnace 11 is filled and raised to a predetermined pressure (100 kPa (approximately atmospheric pressure in this example)). (Charging process). For example, when the pressure inside the reaction furnace 11 is low, the exhaust control valve 28 is fully opened to exhaust the gas inside the reaction furnace 11 by the vacuum pump 25, and when the pressure inside the reaction furnace 11 rises due to the supply of the inert gas. In addition, the exhaust control valve 28 is gradually operated in the closing direction to regulate the gas flow to reduce the exhaust amount by the vacuum pump 25, and when the pressure in the reaction furnace 11 rises to normal pressure, the exhaust control valve 28 28 is fully closed and the atmospheric pressure exhaust valve 24 is fully opened to exhaust the reaction furnace 11 from the atmospheric pressure exhaust path 22.

  By exhausting the inert gas thus supplied from the atmospheric pressure exhaust path 22 through the reaction furnace 11, the pressure in the reaction furnace 11 can be increased to a predetermined pressure. When the inside of the reaction furnace 11 is filled with a predetermined pressure, the gas flow rate supplied to the reaction furnace 11 and the glove box 12 is appropriately adjusted to make the pressure inside the reaction furnace 11 equal to the pressure inside the glove box 12. The opening / closing lid 11a can be opened without generating a gas flow, the substrate on which the thin film is grown is taken out, and a new substrate is installed (reactor opening process). After closing the opening / closing lid 11a again and sealing the reaction furnace 11, the supply of the reactive gas is restarted, the depressurization in the reaction furnace 11 is started, and the same process is repeated by returning to the first temperature rising process.

  By constantly performing the operation of supplying the inert gas to the reaction furnace 11 and the operation of exhausting the gas from the reaction furnace 11 in each process, it is possible to prevent the backflow of the gas from the exhaust section, and to generate particles to cause the reaction inside the reaction furnace 11. Will not flow into. Further, when charging or depressurizing the inside of the reaction furnace 11, the gas conductance in the vacuum exhaust path 22 is adjusted according to the pressure detected by the exhaust pressure gauge 27, so that the gas is smoothly discharged from the inside of the reaction furnace 11. Therefore, it is possible to avoid the generation of particles due to the fluctuation of the gas flow rate.

  Furthermore, after the inside of the reaction furnace 11 has been filled up, decompression purging for reducing the pressure inside the reaction furnace has been conventionally performed, but in the present invention, the inside of the reaction furnace 11 is kept filled. Therefore, the time required for the reduced pressure purge becomes unnecessary, and the time for one cycle can be shortened. As a result, generation of particles can be avoided, time can be shortened, and a semiconductor crystal of higher quality than in the past can be efficiently manufactured.

  In particular, in a vapor phase growth apparatus for forming a compound semiconductor for forming a compound semiconductor on a substrate, for example, a MOCVD apparatus, since an organometallic compound is used as a reactive gas, the present invention can surely prevent generation of particles. The growth time for one cycle can be shortened. Further, the cumulative supply amount of the inert gas serving as the purge gas is larger than the internal volume of the reaction furnace 11, and the reaction gas discharged from the reaction furnace 11 becomes less than the allowable concentration. By performing a gas replacement operation for replacing the gas in the interior with an inert gas, it is possible to reliably prevent harmful reactive gas from flowing out of the reaction furnace 11 into the glove box 12 when the opening / closing lid 11a is opened. .

  11 ... Reactor, 11a ... Open / close lid, 12 ... Glove box, 13 ... Supply valve, 14 ... Flow controller, 15 ... Reactor gas supply path, 16 ... Nitrogen supply valve, 17 ... Glove box gas supply path, 18 ... Open / close valve, 19 ... Automatic valve, 20 ... Glove box gas exhaust path, 21 ... Glove box pressure gauge, 22 ... Normal pressure exhaust path, 23 ... Vacuum exhaust path, 24 ... Normal pressure exhaust valve, 25 ... Vacuum pump , 26 ... Pressure reducing valve, 27 ... Exhaust pressure gauge, 28 ... Exhaust regulating valve

Claims (6)

  In the gas replacement method in the reaction furnace in the vapor phase growth apparatus when opening the reaction furnace to take out the substrate after film formation from the reaction furnace arranged in the glove box in which the inert gas is flowing, the reaction After finishing the film forming operation on the substrate arranged in the furnace, before opening the reaction furnace, while continuing the exhaust operation from the exhaust unit for exhausting the gas in the reaction furnace, A gas replacement method in a reaction furnace in a vapor phase growth apparatus, wherein the gas in the reaction furnace is replaced with a purge gas by introducing a purge gas.   The exhaust unit includes conductance adjusting means for adjusting the conductance of the gas flowing through the exhaust unit, and adjusts the conductance of the exhaust unit in accordance with the amount of purge gas supplied from the purge gas supply unit into the reaction furnace. The method for gas replacement in the reaction furnace in the vapor phase growth apparatus according to claim 1.   After replacing the gas in the reaction furnace with a purge gas and increasing the pressure, until the reaction furnace is opened, the pressure in the reaction furnace is maintained at the same level as the pressure in the glove box without decreasing. The method for gas replacement in the reaction furnace in the vapor phase growth apparatus according to claim 1 or 2.   4. The reactor in the vapor phase growth apparatus according to claim 1, wherein the vapor phase growth apparatus is a vapor phase growth apparatus for forming a compound semiconductor that forms a compound semiconductor on a substrate. Gas replacement method.   The method for gas replacement in a reaction furnace in a vapor phase growth apparatus according to claim 4, wherein the vapor phase growth apparatus is a MOCVD apparatus.   The purge gas replaces the gas in the reaction furnace until the integrated supply amount of the purge gas is larger than the internal volume of the reaction furnace and the concentration of the reactive gas discharged from the reaction furnace becomes equal to or lower than an allowable concentration. The gas replacement method in a reaction furnace in a vapor phase growth apparatus according to claim 1, wherein a gas replacement operation is performed.

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