JPH02153893A - Mbe apparatus - Google Patents

Abstract

PURPOSE:To obtain an MBE apparatus capable of measuring the film thickness of growing crystal in situ by irradiating a substrate in a vacuum chamber with laser beam, separating the reflected light with a half-mirror and monitoring the reflected light wit a detector. CONSTITUTION:The intensity of a laser beam emitted from a laser source 1 is controlled with a neutral density filter 2 to a level to get the output of a detector 8 falling within a proper range. The intensity-controlled laser beam is transmitted through a half mirror 3 and a window 5 and radiated to a substrate 6 during the growth of crystal. The laser beam is reflected on the interface between the substrate and the grown film and on the surface of the grown film, passed through the window 5, reflected perpendicularly on the mirror 3, passed through a filter 7 adjusted to the wavelength of the laser beam and introduced into a detector 8. The output of the detector 8 is recorded with an output monitor 9. Since the interference condition of two laser beams changes with the growth of the film, the detector output recorded by the monitor has a pattern shown in the figure (lambda0 is wavelength of laser beam; n is refractive index of grown layer; Vg is rate of growth; DELTAt is time interval of interference pattern).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an MBE apparatus, and more particularly to an MBE apparatus having a function of in-situ observation of film thickness during growth.

[Conventional technology]

Conventionally, in MBE equipment, the function for in-situ observation of film thickness during crystal growth is the Y Demay (Y, Demay) function.
Journal of Crystal Growth (Jo
81 (1987), page 97.

As shown in FIG. 3, this device includes a xenon lamp 10,
An ellipsometer consisting of a rotating polarizer 11, an analyzer 12, a spectrometer or filter 13, and a detector 8 is an MBE in which a plane mirror 14 is provided in a vacuum chamber 4.
When combined with a device, it has the ability to observe the thickness of a film being grown on the substrate 6 on the spot. Here, the light from the xenon lamp polarized by the rotating polarizer is introduced through the window 5 of the vacuum chamber, reflected by the substrate 6, and irradiated onto the plane mirror 14. This plane mirror 1
The light reflected by 4 is reflected again by the substrate 6 and passes through the window 5 to the analyzer 12, spectrometer or filter 13.
and returns to the ellipsometer containing the detector 8.

[Problem to be solved by the invention]

However, in the MBE device having the above-mentioned film thickness observation function, the diameter of the vacuum chamber window 5 is small, so if you try to fit the incident light and the output light into the window at the same time, you have to delicately adjust the angle of the plane mirror 14. As is well known, the MBE apparatus includes a vacuum pump such as a cryopump that causes mechanical vibrations, so there is a drawback that the finely adjusted set angle of the plane mirror 14 may be deviated.

Furthermore, since the inside of the MBE apparatus is likely to be coated with various materials, the reflectance of the plane mirror 14 becomes poor, and the ellipsometer eventually stops functioning.

The purpose of the present invention is to directly irradiate a substrate with a laser beam without installing a plane mirror as described above in an MBE apparatus,
An object of the present invention is to provide an MBE apparatus that allows on-site observation of film thickness during crystal growth by detecting laser light reflected by a substrate.

[Means to solve the problem]

The MBE apparatus of the present invention includes a vacuum chamber having a window, a neutral density filter provided in front of the window, a semi-transparent mirror, and a substrate placed in the vacuum chamber for irradiating a laser beam through the window. The device includes a laser light source, a detector that detects the reflected laser light from the substrate separated by the semi-transparent mirror via a filter, and a monitor that records the output from the detector.

[Effect]

FIG. 1 is a block diagram of an embodiment of the present invention.

In FIG. 1, the same components as in the conventional example are given the same numbers as in FIG. 3 and will be explained.

The MBE apparatus of the present invention is composed of a laser light source 1, a neutral density filter 2, a semi-transparent mirror 3, a vacuum chamber 4, a vacuum chamber window 5, a substrate 6, a filter 7, a detector 8 and a detector output monitor 9. There is.

In FIG. 1, the intensity of the laser light from a laser light source 1 is adjusted by a neutral density filter 2 so that the output of a detector 8 falls within an appropriate range. The laser beam adjusted in this way is transmitted through the semi-transparent mirror 3 and the MBE.
Irradiation passes through the vacuum chamber window 5 of the apparatus and onto the substrate 6 during crystal growth. The laser beam is then reflected at the interface between the substrate and the grown film and the surface of the grown film, passes through the window 5 again, and reaches the semi-transparent mirror 3. The semi-transparent mirror 3 bends the laser beam at right angles and guides it to the detector 8 through a filter 7 matched to the wavelength of the laser beam.

The output of the detector 8 is recorded on an output monitor 9.

Since the interference conditions between the two reflected laser beams change as the film grows, the output monitor 9 obtains a detector output as shown in FIG. Here, λ0 is the wavelength of the laser beam, n is the refractive index of the grown film, Vg is the growth rate, and Δt is the time interval of the interference pattern. Therefore, the product of Vg and growth time is
This is the thickness of the grown film.

〔Example〕

Next, an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

In the embodiment shown in FIG. 1, 1 means that the wavelength λ0 is 10.6 μm.
Co2 laser light source, 2 has a light attenuation rate of 0.01 to 0.1
% neutral density filter 3 is transmittance/
Gold-deposited semi-transparent mirror with 50% weight resistance, 4 is Ribe
Vacuum chamber of company R's MBE equipment 5 is a Zn5e window, 6 is a CdTe substrate, 7 is a wavelength of 10.6μ! 8 is a HgCdTe infrared detector with a low noise amplifier and 9 is a chart recorder.

Using this example configured as described above, the film thickness during HgCdTe crystal growth was monitored. In the experiment, crystal growth was performed for 7 hours. The Δt calculated from the data recorded on the chart recorder is 49 minutes, and the wavelength λ of the 002 laser.

is 10.6 μm and the refractive index of the HgCdTe crystal is approximately 3.
6, the thickness of the grown HgCdTe crystal is calculated to be 12.6 μm. This value agrees well with the thickness of 13.0 μm obtained by cross-sectional observation of the opened crystal. As described above, the MBE apparatus having the film thickness monitor according to this embodiment is very effective in in-situ observation of crystal growth.

〔Effect of the invention〕

As explained above, according to the present invention, in an MBE apparatus, a substrate in a vacuum chamber is irradiated with a laser beam,
By monitoring the reflected light with a detector, the film thickness during crystal growth can be observed on the spot.

...Xenon lamp, 11...Rotating polarizer 1
2... Analyzer 13... Spectrometer or filter 14... Plane mirror.

Claims (1)

[Claims] a vacuum chamber having a window; a laser light source provided in front of the window for irradiating a laser beam onto a substrate placed in the vacuum chamber through a neutral density filter, a semi-transparent mirror, and the window; An MBE apparatus comprising: a detector that detects reflected laser light from a substrate separated by a transmissive mirror via a filter; and a monitor that records the output from the detector.