JP2005285949A - Molecular beam epitaxial growth device and its cleaning method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To raise operation rates by cleaning efficiently a molecular beam epitaxial growth device. <P>SOLUTION: The molecular beam epitaxial growth device is provided with: an input part 13, which introduces the radical for cleaning the surface of a wall of the chamber arranged in a chamber 11; an exhaust port 14, which is arranged in the chamber and exhausts the gas in a chamber; a radical supplying 20 which is arranged in an input part, generates a radical by converting the gas into a plasma, and supplies the radical to the chamber; and an exhaust device 12 connected to the exhaust port. H radicals and N radicals are generated by a radical generating device and are supplied to the chamber 11. The pollution molecule or pollution atom adhering to the wall of the chamber 11 is removed efficiently by the chemical reaction of radicals. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a molecular beam epitaxial growth apparatus (MBE) having a cleaning function and a cleaning method for a molecular beam epitaxial growth apparatus.

  In recent years, molecular beam epitaxial growth apparatuses (MBE) have been actively used as crystal growth apparatuses in semiconductors. However, since vacuum devices such as MBE perform crystal growth and other processes in a state of being sealed in an ultra-vacuum state, raw material molecules and impurity atoms adhere to the inner wall of the chamber, and the attached atoms are removed. It is necessary to perform cleaning.

  As a technique for cleaning the inside of a chamber for performing a process other than crystal growth, techniques described in the following patent documents are known. Patent Document 1 below discloses a technique for cleaning with fluorine radical ions generated by plasma generated inside a chamber in an apparatus for forming an insulating film using plasma.

  Patent Document 2 below discloses a method of generating plasma in a process chamber and periodically cleaning the inside of the chamber in a plasma etching apparatus. Patent Document 3 below discloses a method of performing plasma cleaning in a reactive ion etching apparatus in order to remove source molecules and atoms attached to a deposition preventing plate that prevents adhesion of source molecules and atoms to the inner wall of the chamber. Disclosure.

JP 2002-134488 A JP 2003-224076 A JP-A-11-112436

  However, in each of Patent Documents 1 to 3, the target process is film formation or etching using plasma, and the apparatus is removed in the same manner as when processing a wafer by periodically removing the processing wafer. This is a method for cleaning the chamber by generating plasma. Patent Documents 2 and 3 disclose that plasma is generated in the chamber and the inside of the chamber is cleaned by the plasma, but that the inside of the chamber is not cleaned only by radicals.

  Further, Patent Document 1 discloses that the inside of the chamber is cleaned with fluorine radical ions, but the radical ions are included when plasma is generated inside the chamber. Therefore, Patent Document 1 discloses cleaning with radical ions, but actually includes neutral atoms, neutral molecules, electrons, ions, and radicals.

  On the other hand, in a molecular beam epitaxial growth apparatus that does not use plasma treatment, plasma cannot be generated in the chamber in order to clean the chamber. When performing maintenance of the molecular beam epitaxial growth system, etc., after cleaning the inner wall of the chamber, repairing the components, replenishing materials, and adjusting the mechanical parts, the entire system is evacuated with a vacuum pump or the like. doing. However, opening the chamber to the atmosphere itself exposes the chamber inner wall to the atmosphere and contaminates the inner wall. For this reason, in order to obtain a desired degree of vacuum in the chamber, it is necessary to clean the contaminated inner wall.

  If the inner wall of the chamber is not cleaned, the contaminated atoms and molecules attached to the inner wall are gradually detached from the inner wall and discharged into the chamber as the vacuum is evacuated. There is a problem that can not be.

The main contaminants adhering to the inner wall of the chamber are H ₂ O and HC compounds. Usually, in order to remove these substances, the chamber itself is heated from the outside simultaneously with evacuation, and the chamber is baked. Usually, the chamber is baked at 150 ° C. for about one week. At this time, the H ₂ O and HC compounds adhering to the inner wall of the chamber obtain separation energy from the inner wall by heating and are released into the chamber, and the molecules of the adhering matter are released to the outside of the chamber along with vacuum exhaust. Will be discharged.

  At this time, in order to efficiently discharge the contaminant molecules detached from the inner wall of the chamber, the gas is flowed to perform baking. However, since the temperature of the surface of the chamber is cooled by the gas flow, the peeled molecules and atoms will adhere to the inner wall of the chamber again, and efficient cleaning cannot be performed. For this reason, once the molecular beam epitaxial growth apparatus is opened to the atmosphere, baking for about one week is required. Therefore, the operation rate of the molecular beam epitaxial growth apparatus is extremely low, for example, 20% to 30%. There wasn't.

  This operating rate is extremely lower than that of the metal organic vapor phase growth apparatus, and this is the reason why the molecular beam epitaxial growth apparatus that can obtain higher quality crystals is not used in the mass production process.

The present invention has been made to solve the above-described problems, and an object thereof is to improve the operation rate of the molecular beam epitaxial growth apparatus.
Another object of the present invention is to enable efficient cleaning of the chamber in order to improve the operating rate of the molecular beam epitaxial growth apparatus.
Another object of the present invention is to execute a short-time cleaning by appropriately controlling the start timing and the end timing of cleaning the chamber of the molecular beam epitaxial growth apparatus.

  The object of the invention is an object to be solved by each invention, and all the inventions should not be construed as achieving all the objects of the invention.

  Since the present invention is a cleaning method and a molecular beam epitaxial growth apparatus for performing the cleaning method, the invention of the cleaning method and the corresponding invention of the molecular beam epitaxial growth apparatus will be described below.

  The invention according to claim 1 for solving the above-described problem is a method for cleaning an inner wall of a chamber of a molecular beam epitaxial growth apparatus (MBE), wherein plasma is applied to a gas introduced into the chamber outside the chamber. A cleaning method for a molecular beam epitaxial growth apparatus, characterized in that a radical is generated and introduced into a chamber.

  According to a sixth aspect of the present invention, in a molecular beam epitaxial growth apparatus (MBE) having a chamber for performing a process, an input unit is provided in the chamber, the radical is introduced into the chamber for cleaning the wall surface of the chamber, An exhaust port for exhausting the gas in the chamber; a radical supply device that is provided in the input unit, generates a radical by converting the gas into plasma and supplies the radical to the chamber; and an exhaust device connected to the exhaust port A molecular beam epitaxial growth apparatus comprising:

  That is, according to the method of the present invention, plasma is generated outside the chamber for crystal growth of the molecular beam epitaxial growth apparatus to supply high concentration radicals into the chamber. Further, the apparatus of the present invention is an apparatus that cleans the chamber by generating a radical by converting the gas into plasma at the input portion of the chamber and supplying the radical to the chamber.

  In practicing the present invention, it is usually desirable to heat the chamber. However, cleaning is possible even if the chamber is not heated because of the radically strong chemical reactivity. In the heated state, radicals are introduced into the chamber. The supply of radicals is performed by evacuating the chamber and flowing a gas from the upstream into the chamber. A radical flow is generated in the chamber by generating a plasma upstream of the gas flow to generate a radical flow.

  As a result, the contaminating molecules and atoms attached to the inner wall of the chamber chemically react with the radicals, and the contaminating molecules and atoms can be separated from the inner wall. In order to dissociate contaminating molecules and atoms from the inner wall by the action of radicals, the energy of radicals is released to the inner wall, so the temperature of the inner wall does not decrease even if there is a gas flow. The dissociated contaminant molecules and atoms are prevented from reattaching because the temperature of the inner wall of the chamber does not decrease, and are taken out of the chamber through the gas outlet by riding on the gas flow. Thereby, the cleaning time can be shortened.

  In the molecular beam epitaxial growth apparatus, the gas is introduced from the input unit and exhausted from the exhaust port by the exhaust action of the exhaust apparatus connected to the exhaust port. A radical supply device is provided in the input section (including a cylindrical member protruding from the chamber) to generate a radical by converting the gas into plasma and supply the radical to the chamber.

  Plasma includes electrons, cations, radicals, neutral molecules, and neutral atoms. For cleaning the inner wall of the chamber, even if particles other than radicals are present, it is considered that there is not much inconvenience as long as there are many radical particles. However, in the present invention, it may be desirable to supply as high a density of radicals as possible into the chamber. Therefore, as long as the radical supply device of the claims has a function of supplying radicals, it may supply other neutral particles, cations, electrons, etc., or extract only radicals. An apparatus that supplies only radicals to the chamber may be used. Extracting only radicals from plasma can be achieved by bending the electrons and cations in a direction perpendicular to the gas flow by an electric field, absorbing the electrons and cations into the conductive material, and collecting the charge in the power source. Is possible. An apparatus that extracts only radicals from plasma and releases the radicals is known as a radical gun, and these may be provided in the vicinity of the input section upstream of the chamber. In this case, the radical generating device of the claim is meant to include a device for extracting only radicals.

  A location where plasma is generated is preferably a gas inlet of the chamber. In other words, it is desirable that it is the closest to being opened to the chamber. This is to prevent the radicals from disappearing. That is, it is desirable that radicals hardly disappear when radicals are generated and immediately opened to a large space. However, as long as radicals are efficiently supplied to the chamber, a radical supply device may be provided at a location away from the chamber. In this case, the path from the location where the radical supply device is provided to the chamber is defined as the input part of the claims.

  Further, while the molecular beam epitaxial growth apparatus is used for original crystal growth, it is desirable to provide a shutter or the like between the plasma generation site and the chamber to shield the chamber.

The invention according to claim 2 or claim 7 is characterized in that the gas is hydrogen gas or / and nitrogen gas, and the radical is hydrogen radical or nitrogen radical. A molecular beam epitaxial growth apparatus according to claim 6, wherein
As hydrogen gas or nitrogen gas, or hydrogen gas and nitrogen gas, radicals are converted into hydrogen radicals or nitrogen radicals, or hydrogen radicals and nitrogen radicals, thereby efficiently removing contaminating molecules and atoms attached to the inner wall of the chamber. be able to. Only one radical may be used, but if both radicals are present, the cleaning efficiency is improved. In particular, the efficiency of cleaning is improved by the presence of hydrogen radicals.

In the inventions of claims 3 and 8, the gas contains ammonia (NH ₃ ), a gas containing at least a hydrogen atom (H) and a nitrogen atom (N), or a hydrogen atom (H). The cleaning method for a molecular beam epitaxial growth apparatus according to claim 1 and the molecular beam epitaxial growth apparatus according to claim 6, wherein the cleaning method is a gas or a gas containing nitrogen atoms (N).

  In this way, hydrogen radicals and nitrogen radicals are generated by converting ammonia gas into plasma. In addition, hydrogen radicals and nitrogen radicals are generated by plasmatization of a gas containing at least hydrogen atoms (H) and nitrogen atoms (N), that is, a molecular gas containing H and N as constituent elements. Further, hydrogen radicals are generated by gasification of a gas containing hydrogen atoms (H), and nitrogen radicals are generated by gasification of a gas containing nitrogen atoms (N). It is a feature of the invention of this claim to introduce a gas that generates hydrogen radicals or nitrogen radicals in this way.

The invention according to claim 4 and claim 9 is an inert gas, and the radical is a radical of an inert atom. The molecular beam according to any one of claims 1 to 3 A method for cleaning an epitaxial growth apparatus, the molecular beam epitaxial growth apparatus according to any one of claims 6 to 8.
In the invention of claim 4 that cites claim 1 and claim 9 that cites claim 6, the gas is an inert gas, and cites claim 4, claim 7, or 8 that cites claim 2 or 3. In the ninth aspect of the invention, the gas further includes an inert gas.

  The inert gas includes a rare gas such as helium, neon, argon, krypton, xenon, or radon. Only the radicals of the inert atoms have a cleaning effect, but the cleaning effect is particularly high when used together with the radicals of these inert atoms together with hydrogen radicals and nitrogen radicals.

According to a fifth aspect of the present invention, the gas component in the chamber is measured, and the start and end of cleaning are controlled based on the measured value. 2. A cleaning method for a molecular beam epitaxial growth apparatus according to item 1.
The invention of claim 10 is characterized by comprising a measuring device for measuring the component amount of the gas in the chamber and a control device for controlling the start and end of cleaning based on the measured value of the measuring device. A molecular beam epitaxial growth apparatus according to any one of claims 6 to 9.

  In these inventions, the amount of gas components in the chamber is measured. The amount of gas component can be implemented, for example, by measuring a light absorption spectrum. In particular, by measuring the absorption spectrum of this light using a laser, glow discharge light, and arc discharge light as a probe, the gas component and the component amount can be measured. In the molecular beam epitaxial growth apparatus, the growth is stopped and the amount of gas components in the chamber is measured while the molecular beam supply source is shielded. If this exceeds a predetermined value, it can be determined that it is the cleaning start time. Next, the radical supply device and the exhaust device are activated, gas is supplied into the chamber, and radicals are supplied from the input portion to the chamber to perform cleaning. When the gas component amount detected by the measuring device becomes lower than a predetermined value, it is determined that the cleaning is completed, and the cleaning is stopped.

  According to the cleaning method and molecular beam epitaxial growth apparatus of the molecular beam epitaxial growth apparatus of the present invention, it is possible to automatically determine the cleaning start time and end time. Therefore, the operation efficiency can be made extremely high while keeping the quality of the crystal grown by this apparatus high.

  According to the present invention, due to the high chemical reactivity of radicals, contaminant molecules and atoms attached to the inner wall of the chamber of the molecular beam epitaxial growth apparatus are removed and cleaned, so that the chamber wall surface is cooled. Therefore, efficient cleaning is possible. As a result, cleaning can be performed in a short time, and the operation efficiency of the molecular beam epitaxial growth apparatus can be improved.

  According to the fifth and tenth aspects of the present invention, since the cleaning start time and end time can be automatically determined, the cleaning can be completed in the shortest time through the cleaning at the optimum time. Therefore, the operating efficiency of the molecular beam epitaxial growth apparatus can be improved.

  Thus, conventionally, an organic metal gas vapor phase growth apparatus has been advantageous for mass production. However, according to the present invention, a molecular beam epitaxial growth apparatus can be used for mass production, and a device having high quality. The mass production of crystals and crystals is possible, and the industrial significance of the present invention is great.

  The best mode for carrying out the present invention will be described. The embodiments will be specifically described in order to facilitate understanding of the inventive concept, and the present invention should not be construed as being limited to the following examples.

  FIG. 1 shows a molecular beam epitaxial growth apparatus 10 according to a specific embodiment of the present invention. The chamber 11 is provided with an input unit 13 and an exhaust port 14. A high vacuum exhaust device 12 is connected to the exhaust port 14 and the chamber 11 is exhausted to a high vacuum by this device. Further, a radical generator 20 and an electron / ion removal device 40 are provided inside the input unit 13 which is a cylindrical metal body. The input unit 13 includes nitrogen gas and hydrogen from a nitrogen gas cylinder 31. Hydrogen gas is supplied from the gas cylinder 32. In addition, a shutter 15 that blocks the input unit 13 and the chamber 11 is provided at a portion of the input unit 13 that opens to the chamber 11. When the molecular beam epitaxial growth apparatus 10 is performing crystal growth, the shutter 15 is in a closed state.

FIG. 2 is a cross-sectional view showing the configuration of the radical generator 20. A plurality of flat anodes 21, spacers 22 made of a flat insulator, and flat cathodes 23 are stacked. In the figure, four sets are stacked. And many through-holes 24 (micro hollow) with a diameter of 0.1 mm are provided. A mixed gas of N ₂ and H ₂ is passed through the through hole 24, and a DC voltage is applied between the anode 21 and the cathode 23. At this time, plasma is generated by glow discharge in the portion 25 of the through hole 24 of each cathode 23. Electrons, cations, neutral particles, and radicals are generated by plasma.

  This plasma flow then flows into the electron / ion removal device 40. The electron / ion removing apparatus 40 is an apparatus that removes electrons and ions from plasma and extracts radicals and neutral particles. This apparatus is possible by a method in which electrons and cations are bent in a direction perpendicular to the gas flow by an electric field, the electrons and cations are absorbed in a conductive material, and electric charges are collected by a power source. This device extracts radicals from plasma and releases radicals.

Usually, when the chamber 11 is cleaned, N ₂ and H ₂ are supplied to the radical generator 20 while the chamber 11 is heated in a furnace (not shown) and evacuated by the high vacuum evacuator 12. N radicals and H radicals generated by the radical generator 20 are introduced into the chamber 11, chemically react with contaminant molecules and contaminant atoms adhering to the wall surface, leave the wall surface, and are exhausted by the high vacuum exhaust device 12. It is discharged to the outside in the flow. The pollutant molecules and atoms are peeled off by a chemical reaction by radicals, and the excitation energy of radicals is released at that time, so the wall surface is not cooled. Therefore, the cleaning effect is kept high and cleaning can be performed in a short time.

  In general, the above cleaning is performed after the molecular beam epitaxial growth apparatus is opened and opened to the atmosphere and repaired. However, the cleaning may be performed between normal crystal growths without opening the molecular beam epitaxial growth apparatus. Further, heating of the chamber 11 at the time of cleaning is not always necessary.

  Further, the cleaning start time and end time can be controlled as follows. A gas analyzer 51 is provided in the chamber 11. Irradiation with glow discharge light, arc discharge light, or laser is performed to measure the absorption spectrum of these lights. A light source and a light receiving element are arranged in the chamber 11, and an output signal from the light receiving element is input to the control device 50. In a state where the crystal growth is completely stopped, when the predetermined gas component amount exceeds a predetermined value by the control device, it is determined that the cleaning start time is reached, and the cleaning is started by the above procedure. Thereafter, when the gas component amount measured by the gas analyzer 51 becomes equal to or less than a predetermined value, the above cleaning is stopped. Thereby, it is possible to know an appropriate time to start cleaning, and to complete the cleaning in a minimum time.

FIG. 3 shows a radical generator 60 having another configuration. A number of glass tubes 61 having an inner diameter of 0.1 mm to 0.5 mm are arranged in a matrix. A mixed gas of N ₂ and H ₂ passes through the inside of the glass tube 61. A flat plate-like first electrode 63 and a flat plate-like second electrode 64 are arranged to face each other in a direction orthogonal to the longitudinal direction of the glass tube 61. The second electrode 64 is connected to the ground. A high frequency is applied between the first electrode 63 and the second electrode 64. Plasma is generated inside the glass tube 61 by the high-frequency power, and H radicals and N radicals are generated. These radicals are supplied to the chamber 11 to clean the inner wall of the chamber 11.

In the above embodiment, N ₂ gas and H ₂ gas are used, but NH ₃ gas may be used. Further, a molecular gas containing N atoms and H atoms may be used. Further, a mixed gas of a gas containing N and a gas containing H may be used. Further, an inert gas may be mixed in this. A mixture of these radicals such as radicals of group 0 elements such as N radicals, H radicals, and Ar radicals from these plasmas can be used for etching the chamber.

  Further, the radical generator is not limited to the above embodiment, and is arbitrary. For example, microwaves propagated in a waveguide are converted into a coaxial mode and supplied to a ring-shaped gap. By passing the gas through the gap and discharging it, plasma is generated to generate radicals. You may make it supply.

  The present invention has a tremendous effect in improving the operating rate of the molecular beam epitaxial growth apparatus. Therefore, the present invention is a main technique to be solved since the molecular beam epitaxial growth apparatus is used for mass production of semiconductors. This technology is extremely effective in industrialization.

The block diagram which showed the molecular beam epitaxial growth apparatus which concerns on the specific Example of this invention. The block diagram of the radical generator used with the Example apparatus. The block diagram of another radical generator. Explanatory drawing which showed the mode of generation | occurrence | production of the radical of the apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Molecular beam epitaxial growth apparatus 11 ... Chamber 20 ... Radical generator 40 ... Electron / ion removal apparatus 21 ... Anode 22 ... Spacer (insulator)
23 ... Cathode 24 ... Through hole (micro hollow)
61 ... pipe 63 ... first electrode 64 ... second electrode

Claims (10)

In a method of cleaning an inner wall of a chamber of a molecular beam epitaxial growth apparatus (MBE),
A cleaning method for a molecular beam epitaxial growth apparatus, characterized in that plasma is generated with respect to a gas introduced into the chamber outside the chamber, radicals are generated, and the radical is introduced into the chamber.   2. The cleaning method for a molecular beam epitaxial growth apparatus according to claim 1, wherein the gas is hydrogen gas and / or nitrogen gas, and the radical is a hydrogen radical or a nitrogen radical. The gas is ammonia (NH ₃ ), a gas containing at least a hydrogen atom (H) and a nitrogen atom (N), a gas containing a hydrogen atom (H) or / and a gas containing a nitrogen atom (N). The method for cleaning a molecular beam epitaxial growth apparatus according to claim 1, wherein:   4. The cleaning method for a molecular beam epitaxial growth apparatus according to claim 1, wherein the gas is an inert gas, and the radical is a radical of an inert atom.   5. The molecular beam epitaxial growth according to claim 1, wherein a gas component in the chamber is measured, and the start and end of cleaning are controlled based on the measured value. How to clean the device. In a molecular beam epitaxial growth apparatus (MBE) having a chamber for performing a process,
An input unit provided in the chamber for introducing radicals for cleaning the wall surface of the chamber;
An exhaust port provided in the chamber for exhausting the gas in the chamber;
A radical supply device that is provided in the input unit, generates a radical by converting the gas into plasma, and supplies the radical to the chamber;
A molecular beam epitaxial growth apparatus comprising: an exhaust apparatus connected to the exhaust port.   The molecular beam epitaxial growth apparatus according to claim 6, wherein the gas is hydrogen gas and / or nitrogen gas, and the radical is a hydrogen radical or a nitrogen radical. The gas is ammonia (NH ₃ ), a gas containing at least a hydrogen atom (H) and a nitrogen atom (N), a gas containing a hydrogen atom (H) or / and a gas containing a nitrogen atom (N). The method for cleaning a molecular beam epitaxial growth apparatus according to claim 6, wherein:   The molecular beam epitaxial growth apparatus according to any one of claims 6 to 8, wherein the gas is an inert gas, and the radical is a radical of an inert atom. A measuring device for measuring the amount of gas components in the chamber;
A control device for controlling the start and end of cleaning based on the measurement value of the measurement device;
10. The molecular beam epitaxial growth apparatus according to claim 6, comprising:

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