JPS61132591A - Device for controlling intensity of particle beam in particle beam epitaxial apparatus - Google Patents

Abstract

PURPOSE:To control the mixed crystal ratio of a compound semiconductor in high accuracy, and to obtain a crystal having high quality, by detecting the fluorescent light emitted from the particle beam excited with monochromatic light radiation, and controlling the intensity of the particle beam according to the detected signal. CONSTITUTION:The beam-source chamber 12 and the growth chamber 13 of the vacuum chamber 10 of a particle beam epitaxial growth apparatus are evacuated, the cooling wall 11 separating both chambers is filled with a refrigerant such as liquid N2, etc., and the substrate 2 is heated at a prescribed temperature via the substrate-supporting table. Particle beams are emitted from the particle beam sources 30, 40, and only the desired kinds of particle beams 26a, 26b are transmitted through the shutter 20 and the holes 16 to the surface of the substrate 2. The particle beams 26a, 26b are irradiated with monochromatic light 54 emitted from the light source 50 such as a xenon lamp, etc., and monochromatized with a spectrometer 52, and the emitted fluorescent light is detected by the fluorescent light detectors 56a, 56b, and fed back through the optical fiber 57a, 57b and the photometers 58a, 58b to the mass-flow controllers 31, 41 to effect the growth of the crystal under definite particle beam intensity.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is an apparatus for epitaxially growing a compound semiconductor such as a group IV compound semiconductor on a substrate. This invention relates to a device for controlling intensity.

(Prior Art) A particle beam epitaxial apparatus has been proposed in which a particle beam of molecules, atoms, ions, or radicals is irradiated onto a substrate to cause epitaxial growth under an ultra-high vacuum. If a compound is to be grown using such a particle beam epitaxial apparatus, the particle beam intensity for each component element must be precisely controlled in order to accurately control the mixed crystal ratio.

(Problems to be Solved by the Invention) Generally, in order to control the deposited film thickness or grown film thickness using the vapor deposition method or the molecular beam epitaxial growth method, a crystal oscillation type film thickness monitor, nude ion gauge, or quadrupole mass analyzer is used. is used. These film thickness monitors and the like are installed on the side or rear of the substrate for vapor deposition or growth. In vapor deposition methods and molecular beam epitaxial growth methods, evaporated particles fly over a wider area than the substrate, so the deposition rate or growth rate can be monitored with a film thickness monitor installed outside the substrate. In the particle beam epitaxial apparatus, the particle beam that flies to the substrate is limited to a relatively narrow area, so the growth rate cannot be monitored with a film thickness monitor or the like installed outside the substrate.

Therefore, it has been proposed to use an atomic absorption method as one method for measuring the intensity of particle beams flying toward the substrate. However, when the particle beam density hitting the substrate becomes extremely thin, such as in particle beam epitaxial growth, the atomic absorption method lacks sensitivity and poses a practical problem. Therefore, there is a demand for the development of a particle beam intensity measuring device with even higher sensitivity.

What has not yet been invented is a particle beam intensity that can improve the sensitivity of particle beam intensity measurements in particle beam epitaxial equipment, accurately control the single particle beam intensity of each component element, and grow high-quality compound semiconductor crystals. The purpose of this invention is to provide a control device.

(Means for solving problems) The present invention relates to a particle beam epitaxial apparatus.

The apparatus of the present invention, which detects the particle beam intensity with high sensitivity by irradiating monochromatic light onto a particle beam to excite it and detecting the generated fluorescence, will be explained with reference to FIG. 1 showing one embodiment. an excitation source 50.2 that irradiates the particle beams 26a and 26b reaching the particle beams 26a and 26b with monochromatic light 54 necessary for excitation of the particle beams;
52, detectors 5.6a, 56b, 58a, and 58b that detect fluorescence generated from the excited particle beam, and the particle beam generation intensity of the particle beam source 30.40 based on the detection signal intensity of the detectors. and means 31 and 41 for controlling the same.

(Function) When the particle beams 26a, 26b are irradiated with monochromatic light 54 of the required wavelength, they emit fluorescence with a wavelength specific to the element of the particle beams 26a, 26b, but the intensity of this fluorescence depends on the particle beam density. is proportional to. Therefore, the detectors 56a, 56b, 5
8a and 58b detect the intensity of the fluorescence, and control means 31
．． 41 so that the fluorescence intensity is constant.
Since the particle beam is controlled at 0°40, the intensity of the particle beam hitting the substrate 2 is constant.

(Example) First, FIG. 2 shows an outline of an example of a particle beam epitaxial apparatus to which the present invention is applied.

In this particle beam epitaxial device, a vacuum chamber 1
0 is connected to the radiation source chamber 12 by the cooling wall 11 provided at an angle.
and a growth chamber 13.

The cooling wall 11 is hollow inside and can be filled with a refrigerant such as liquid nitrogen, and includes a refrigerant inlet (as shown) and a gas exhaust port for vaporized refrigerant (as shown). The cooling wall 11 has a large group 1 for passing the particle beam from the radiation source chamber 12 to the growth chamber 13.
6 and a hole for shutter operation, etc., is drilled through it as necessary.

The radiation source chamber 12 includes a plurality of particle radiation sources, such as symbols 28a and 2.
8b, a shutter 20 for selecting one particle beam and an exhaust port 21 connected to a high vacuum pump are provided. It is provided at a position slanting and facing the cooling wall 11 so that unnecessary reflected particle beams 23 generated by being reflected by the cooling wall 11 or the shutter 20 can be effectively discharged.

The growth chamber 13 is provided with a substrate 2 fixed to a substrate support (as shown) and an exhaust port 25 connected to a high vacuum pump independent of the vacuum system of the radiation source chamber 12. Particle beam sources 28a and 28 are provided on the surface of the substrate 2 through a large group 16 of cooling walls 11.
A useful particle beam 26 is incident from the surface of the substrate 2, but the 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 and is effectively discharged from the substrate 2.
The fixation angle is set.

During operation of this particle beam epitaxial apparatus, the source chamber I2
Then, unnecessary particle beams that do not pass through the large group 16 of the cooling ff1ll are reflected by the shutter 20 or the cooling wall 11 and are discharged to the exhaust port 21, or are adsorbed to the cooling wall 11 which is cooled to the temperature of liquid nitrogen or other refrigerant. Source room 1
A high vacuum of 2 is maintained. In the growth chamber 13, crystal growth is performed on the substrate 2 by the useful particle beam 26 that has passed through the large group 16, but unnecessary particle beams that are not used for crystal growth among the single particle beams 26 become reflected particle beams 27. The high vacuum of the growth chamber 13 is maintained by being exhausted to the exhaust port 25 or being adsorbed by the cooling wall 11. In the growth chamber 13, the amount of the particle beam 26 that enters through the large group 16 is smaller than the amount of the particle beam 22 that enters the source chamber 12, and the growth chamber 13 and the source chamber 12 are separated from each other by the large group 16. However, since the diameter of this large group 16 is extremely small compared to the total area of the cooling wall 11, differential pumping is performed between the growth chamber 13 and the radiation source chamber 12, so that the growth chamber 13 has a higher height. It becomes a vacuum,
The area around the substrate 2 is maintained at a high vacuum of, for example, 10-'' Torr.

FIG. 1 schematically shows the particle beam epitaxial apparatus shown in FIG. 2 in which a particle beam intensity control device of one embodiment is provided. Particle beam 26a reaching substrate 2
, 26b is composed of a powerful light source 50 and a spectrometer 52 that separates the light from the light source 50 into monochromatic light 54. As the light source 50, for example, a xenon lamp, a low pressure mercury lamp, a medium pressure mercury lamp, or an ultra-high pressure mercury lamp can be used. A laser device can also be used as an excitation source for emitting monochromatic light 54. Monochromatic light 54 from the spectrometer 52 is irradiated into the growth chamber 13 through a quartz window (as shown).

Reference numerals 56a and 56b are fluorescence detection ends that receive fluorescence emitted by the particle beams 26a and 26b when excited by the monochromatic light 54, and the tips thereof are oriented toward the particle beams 26a and 26b, respectively, so that the fluorescence can be effectively received. It spreads out like a cap. The fluorescence received by the fluorescence detection ends 56a and 56b.

Photometer 58 by optical fibers 57a and 57b, respectively
a, led to 58b. The photometers 58a, 58b are equipped with filters to block scattered light from the light guided by the optical fibers 57a, 57b. The output signals of the photometers 58a and 58b are respectively input to the mass flow controller 31.41 of the particle beam source 30.40, and the mass flow controller 3
1.41 controls the particle beam generation amount of each particle beam source 30.40 so that the output signals of the photometers 58a and 58b are constant.

FIG. 1 also shows, among the particle beam sources controlled by the present invention,
A system using a gaseous raw material is exemplified as a particularly preferable particle beam source.

30 is an electron ionization source that uses ions generated by electron bombardment as a particle beam, and includes a mass flow controller 31 that controls the flow rate of source gas, a particle beam generation aperture 32 that converts the controlled source gas into a beam, and An ionization chamber 33 that ionizes a particle beam by irradiating it with an electron beam, an electrode 34 that accelerates and converges the ionized particle beam, an exhaust port 35 that discharges unnecessary particle beams, and a magnetic field that applies a magnetic field to separate ions. An application means 36 is provided.

In this electron ionization radiation source 30, a particle beam formed into a beam by a single particle beam generation aperture 32 is ionized as it passes through an ionization chamber 33, accelerated and focused by an electrode 34, and unnecessary ions are separated by a magnetic field, making it useful. Only these ions become particle beams and are introduced into the growth chamber 13.

40 is a photoionization radiation source that uses ions and radicals generated by light irradiation as a particle beam, and like the electron ionization radiation source 30, it is equipped with a mass flow controller 41 and a particle beam generation aperture 42; includes a photoionization chamber 43, which irradiates light such as Ar laser light instead of electron beam irradiation 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, unnecessary ions from the particle beam ionized or radicalized in the photoionization chamber 43 are separated by a quadrupole mass filter 44, and only useful ions and radicals are separated from the particle beam. Then, it is introduced into the growth chamber 13.

As a particle beam source, as long as the emission intensity of the particle beam can be controlled, in addition to a type that uses a gaseous raw material as shown in the example, a solid source such as that used in conventional molecular beam epitaxial equipment can be used. Knudsencel can also be used. When a gaseous raw material is used, a turbo-molecular pump capable of continuous operation is most preferable as a high-vacuum pump.

The type and number of particle beam sources provided in such a particle beam epitaxial apparatus can be arbitrarily selected depending on the type of crystal to be grown.

To perform epitaxial growth using the particle beam epitaxial apparatus shown in FIG. 1 equipped with this particle beam intensity control device, the source chamber 12 and the growth chamber 13 are evacuated, and the cooling wall 11 is filled with a coolant such as liquid nitrogen. Then, the substrate 2 is heated to a predetermined temperature through the substrate support. After that, particle beam source 30.4
Particle beams are emitted from zero, a desired large group 16 is opened with a shutter, and only desired types of particle beams 26a and 26b are incident on the surface of the substrate 2. At this time, light from a light source 50 such as a xenon lamp is converted into monochromatic light 54 by a spectrometer 52 as a particle beam 2.
6a, 26b, and the resulting particle beams 26a, 26
Fluorescence from b is detected by fluorescence detection ends 56a, 56b, optical fibers 57a, 57b, and 3'6m total 58a, 58b.
The particles are then fed back to the mass flow controllers 31 and 41 to perform growth while keeping the particle beam generation intensity from the particle beam sources 30 and 40 constant. The particle beams 26a, 26b
When a predetermined amount of growth has been achieved, the next particle beam is selected by operating the shutter to change the group 16 to be opened, and the fluorescence from the particle beam due to the excitation of the monochromatic light 54 is detected again. Growth is performed again while controlling the generation intensity to a constant value. This operation is repeated to grow an epitaxial layer of the compound.

(Effects of the Invention) By using the particle beam intensity control device of the present invention, it is possible to detect extremely low concentration particle beams, accurately control the mixed crystal ratio of compound semiconductors, and create high-quality crystals. It becomes possible.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing a particle beam epitaxial apparatus equipped with an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view showing a particle beam epitaxial apparatus to which the present invention is applied. 2... Board, 12... Source room,
13...growth chamber, 26a, 26b-particle beam, 30,40...particle beam source, 31,32.
...Mass flow controller, 50...
・Light source, 52... Spectrometer. 54... Monochromatic light, 56a, 56b...
- Fluorescence detection end, 57a, 57b... Optical fiber, 58a. 58b...Photometer.

Claims (1)

[Claims] (1) An excitation source that irradiates a particle beam reaching a substrate with monochromatic light necessary for excitation of the particle beam in a particle beam epitaxial device, a detector that detects fluorescence generated from the excited particle beam, and the detector. A particle beam intensity control device comprising: means for controlling the particle beam generation intensity of a particle beam source based on the detection signal intensity of the particle beam source.