JPH054360B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a growth rate control method in an apparatus for growing an epitaxial layer on a substrate. (Prior Art) The present inventor has proposed a particle beam epitaxial apparatus. In this particle beam epitaxial apparatus, a vacuum chamber is separated into a source chamber and a growth chamber by a cooling wall that is inclined with respect to the particle beam ejected from the particle beam source to the substrate. The cooling wall and substrate are tilted so that the particle beams are connected through holes, but are exhausted by independent exhaust systems, and the unnecessary particle beams scattered in each chamber are effectively exhausted by each exhaust system. , and the position of the exhaust port of each exhaust system are set. Here, the word "particle" is used to collectively refer to molecules, atoms, ions, and radicals. Generally, crystal oscillation type film thickness monitors, nude ion gauges, and quadrupole mass analyzers are used to control the deposited film thickness and grown film thickness in vapor deposition methods and molecular beam epitaxial growth (MBE) methods. This film thickness monitor and the like are installed on the side or rear of the substrate for deposition or growth. In the vapor deposition method and molecular beam epitaxial growth method, the evaporated particles fly over a wider area than the substrate, so the deposition rate or growth rate can be monitored using a film thickness monitor installed outside the substrate. However, in the above-mentioned particle beam epitaxial growth method proposed by the present inventor, the particle beam that flies to the substrate passes through the hole in the cooling wall and is restricted to a relatively narrow area, so the particle beam is placed outside the substrate. The growth rate cannot be monitored using a film thickness monitor. (Objective) An object of the present invention is to provide a method for simultaneously controlling the growth rate for each element or molecule in a particle beam epitaxial apparatus. (Structure) The growth rate control method of the present invention uses atomic absorption spectroscopy, in which a particle beam incident on a substrate is irradiated with light from a light source section of an atomic absorption spectrometer, and the transmitted light is detected by a light detection section. This is a growth rate control method in which the particle dose generated by the particle beam source is controlled by the output signal of the photodetector. (Example) FIG. 1 shows an outline of a particle beam epitaxial apparatus to which the present invention is applied. In this particle beam epitaxial apparatus, a vacuum chamber 10 is separated into a radiation source chamber 12 and a growth chamber 13 by an inclined cooling wall 11. The cooling wall 11 is hollow inside and can be filled with a refrigerant such as liquid nitrogen, and is provided with a refrigerant inlet 14 and a gas exhaust port 15 for vaporized refrigerant. A group of holes 16 for passing the particle beam from the radiation source chamber 12 to the growth chamber 13 and holes for operating the shutter, etc., are drilled through the cooling wall 11 as required. The radiation source chamber 12 includes a plurality of particle radiation sources, for example, symbol 1.
7 to 19, a shutter 20 for selecting a particle beam and an exhaust port 21 connected to a high vacuum pump
The exhaust port 21 is connected to the cooling wall 11 where the unnecessary part of the particle beam 22 from each particle beam source 17 to 19 is located, or if the shutter 20 is installed parallel to the cooling wall 11, the exhaust port 21 is connected to the cooling wall 11. 11 or unnecessary reflected particle beam 23 generated by being reflected by the shutter 20
It is provided at a position facing the cooling wall 11 so that it can be effectively discharged. The growth chamber 13 has a substrate 2 and an exhaust port 25 connected to a high vacuum pump independent of the vacuum system of the radiation source chamber 12.
is provided. A cooling wall 1 is provided on the surface of the substrate 2.
A useful particle beam 26 is incident from the particle beam sources 17 to 19 through the hole group 16 of No. 1, but an unnecessary reflected particle beam 27 generated by reflection from the surface of the substrate 2 is reflected in the direction of the exhaust port 25. The fixation angle of the substrate 2 is set so that the substrate 2 can be effectively discharged. Reference numeral 28 denotes light from a light source for atomic absorption spectroscopy of the present invention, which is incident across the particle beam 26 just before reaching the substrate 2, and the transmitted light is detected by a photodetector 29. The output signal is the particle beam source 17
-19, and the amount of particle beam emission is controlled. The light 28 has different wavelengths depending on the type of particle beam, and each particle beam source 17
19 are individually controlled by signals from the photodetector 29. During operation of this particle beam epitaxial apparatus, in the radiation source chamber 12, unnecessary particle beams that do not pass through the hole group 16 of the cooling wall 11 are reflected by the shutter 20 or the cooling wall 11 and are discharged to the exhaust port 21. A high vacuum is maintained in the radiation source chamber 12 by adsorption to the cooling wall 11 which is cooled to the temperature of liquid nitrogen or other refrigerant. In the growth chamber 13 , crystal growth is performed on the substrate 2 by the useful particle beam 2 that has passed through the hole group 16 , but unnecessary particle beams that are not used for crystal growth among the particle beams 26 are reflected particle beams 27 . The high vacuum of the growth chamber 13 is maintained by being discharged to the exhaust port 25 or being adsorbed to the cooling wall 11 . In the growth chamber 13, the amount of the particle beam 26 that enters through the hole group 16 is smaller than the amount of the particle beam that enters the radiation source chamber 12, and the growth chamber 13 and the source chamber 12 are connected to the hole group. 16, the diameter of this hole group 16 is extremely small compared to the total area of the cooling wall 11, so the growth chamber 13 and the radiation source chamber 12
Differential pumping is performed between the growth chambers 13 and 13, resulting in a higher vacuum in the growth chamber 13, thereby keeping the area around the substrate 2 even more clean. The cooling wall 11 also serves as a source chamber 12 and a growth chamber 13.
It serves to create a high vacuum inside the vacuum chamber 10 by adsorbing water, carbon dioxide, etc. inside. In order to perform epitaxial growth using this particle beam epitaxial apparatus, a radiation source chamber 12 and a growth chamber 13 are required.
is evacuated, the cooling wall 11 is filled with a coolant such as liquid nitrogen, and the substrate 2 is heated to a predetermined temperature through the substrate support 24. After that, particle beam source 17~
A particle beam 22 is ejected from 19, a desired hole group 16 is opened with a shutter 20, and only the desired type of particle beam 26 is incident on the surface of the substrate 2, and the particle beam is detected by a signal from a photodetector 29 using atomic absorption spectroscopy. Growth is performed while controlling the emission speed of the source to be constant. When the particle beam 26 has grown a predetermined amount, the shutter 20 is operated to change the hole group 16 to be opened, the next particle beam 26 is selected, and the signal from the photodetector 29 is used to select the particle beam source. The epitaxial layer of the compound is grown by repeating the operation of growing again while controlling the emission speed of the compound to be constant. Particle beam sources 17 to 19 may be of a type that uses gaseous raw materials as described below, as long as the emission speed of the particle beam can be controlled, or solid sources such as those used in conventional molecular beam epitaxial equipment. A Knudsen cell using raw materials can also be used, and the type and number of particle beam sources can be arbitrarily selected depending on the type of crystal to be grown. When using a gaseous raw material, a turbo-molecular pump capable of continuous operation is most preferred as a high-vacuum pump. Among the particle beam sources controlled by the present invention, a particularly preferable particle beam source using a gaseous raw material is illustrated in FIG. 30 is an electron ionization source that uses ions generated by electron bombardment as a particle beam, and a mass flow controller 3 that controls the flow rate of source gas.
1. A particle beam generation aperture 32 that turns the controlled source gas into a beam; an ionization chamber 33 that ionizes the particle beam by irradiating it with an electron beam; an electrode 34 that accelerates and focuses the ionized particle beam; It is provided with an exhaust port 35 for discharging the particle beam, and a magnetic field applying means 36 for applying a magnetic field to separate ions.
In this electron ionization source 30, a particle beam formed into a beam by a particle beam generation aperture 32 is sent to an ionization chamber 33.
The particle beam 22 is ionized, accelerated and focused by the electrode 34, unnecessary ions are separated by a magnetic field, and only useful ions are introduced into the growth chamber 13 as a particle beam 22. 40 is a photoionization radiation source that uses ions and radicals generated by light irradiation as a particle beam,
Similar to the electron ionization source 30, it includes a mass flow controller 41 and a particle beam generation aperture 42, but
In the case of this radiation source, a photoionization chamber 43 is provided, and instead of electron beam irradiation, light such as Ar laser light is irradiated to ionize or radicalize the particle beam. 44 is a quadrupole mass filter for separating and selecting ions, and 45 is an exhaust port for discharging unnecessary particles.
In this photoionization radiation source 40, a photoionization chamber 43
Unnecessary ions from the ionized or radicalized particle beam are separated by a quadrupole mass filter 44, and only useful ion and radical particle beams are introduced into the growth chamber 13 as a particle beam 22. The main raw material gases that can be used with these particle beam sources are shown in the table below, and the compounds grown using these raw material gases include InP,
Examples include GaAs, AlGaAs, GaInAsP, AlInGaN, and other binary, ternary, or quaternary semiconductor compounds (Al, In, Ga, Sb, As).

[Table] A system diagram of one embodiment of the method of the present invention is shown in FIG. As a particle beam source, in addition to the electron ionization source 30 and photoionization source 40 shown in FIG. 2, a Langmuir cell (or Knudsen cell) 60 used in a molecular beam epitaxial apparatus is used. do. Reference numeral 62 denotes an atomic absorption spectrometer used in the method of the present invention, which measures the particle dose by atomic absorption spectroscopy of the particle beam just before it reaches the substrate 2 in the growth chamber 13, and uses that signal to control the electron ionization source 30 and photoionization. These particle beam sources 3 are controlled by controlling the respective mass flow controllers 31 and 41 of the radiation source 40 and the cell controller 61 of the Knudsen cell 60.
The particle doses emitted from 0, 40, and 60 are controlled to be constant. For example, a laser may be used as the light source of the atomic absorption spectrometer 62 and guided to the vicinity of the substrate 2 using an optical fiber. 66 is a turbo molecular pump that evacuates the radiation source chamber 12 to a high vacuum;
2, and is equipped with a rotary pump 68 as an auxiliary pump. 69 is a vacuum valve. A turbo molecular pump 70 evacuates the growth chamber 13 to a high vacuum, and is provided in the growth chamber 13 via a gate valve 71, and is equipped with a rotary pump 72 as an auxiliary pump. 73 is a vacuum valve. (Effects) By the atomic absorption spectroscopy of the present invention, it has become possible to control the growth rate of a particle beam epitaxial device for each element. In addition, unlike quartz crystal oscillation monitors, atomic absorption spectroscopy does not have a lifespan limited by the thickness of a deposited film, so it can be used continuously for a long time.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a particle beam epitaxial apparatus to which the method of the present invention is applied, FIG. 2 is a schematic diagram of a particle beam epitaxial apparatus showing an example of a particle beam source controlled by the method of the present invention, and FIG. The figure is a block diagram showing one embodiment of the method of the present invention. 2... Substrate, 11... Cooling wall, 12... Radiation source chamber, 13
... Growth chamber, 17-19, 30, 40, 60... Particle beam source, 26... Particle beam, 28... Light of atomic absorption spectrometer, 29... Photodetector.

Claims (1)

[Scope of Claims] 1. A radiation source chamber having a particle beam source and a shutter for selecting a particle beam, and a growth chamber for accommodating a substrate are provided with mutually independent exhaust systems, and these radiation source chamber and growth chamber are In a particle beam epitaxial apparatus, in which the particles incident on the substrate are separated by a cooling wall provided at an angle with respect to the particle beam flow and have holes for passing the particle beam from the particle beam source to the substrate. The method is characterized in that the radiation is irradiated with light from a light source section of an atomic absorption spectrometer, the transmitted light is detected by a light detection section, and the particle dose generated by the particle beam source is controlled by the output signal of the light detection section. Growth rate control method.