JPH042553B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a molecular beam epitaxial growth method for controlling crystal growth of compound semiconductors.

(Prior art) The conventionally known molecular beam epitaxial growth method measures the intensity of the molecular beam and adjusts the heating temperature, opening time of the evaporation source storage container, etc. so that the intensity remains constant. Therefore, the film thickness and single atomic layer growth were controlled.

Furthermore, the opening time and opening diameter of the evaporation source storage container are actually controlled based on empirical factors.

Furthermore, as a method to control single atomic layer growth,
It has also been known to utilize reflection-type high-speed electron diffraction, in which electrons are ejected into the growth layer and reflected, and the growth status of the atomic layer is determined by the reflected electrons.

(Problems to be Solved by the Present Invention) As described above, the conventional method of measuring the intensity of molecular beams does not directly control the growth of crystals formed on the substrate, but indirectly measures the intensity of molecular beams. Since the control is based on various elements, there was a problem that it lacked accuracy.

In addition, the method of controlling the opening diameter and opening time of the evaporation source storage container is not based on direct information about the surface of the substrate, and has the same accuracy problem as measuring molecular beam intensity. It was hot.

Furthermore, when reflection-type high-speed electron diffraction is used, when the substrate is irradiated with electrons, trace amounts of carbon compounds remaining in the vacuum are decomposed and carbon is deposited on the substrate. This often left problems in quality control, such as impairing the purity of the atomic layer and causing lattice defects to occur in the atomic layer.

An object of the present invention is to provide a molecular beam epitaxial growth method that enables more accurate control by directly detecting the conditions on the substrate.

(Means for Solving the Problems) In the present invention, a substrate is installed in an ultra-high vacuum chamber, and an evaporation source storage container is provided to store an evaporation source for an atomic layer to be grown on the surface of the substrate. This method is based on the molecular beam epitaxial growth method, in which a monoatomic layer is grown on a substrate by evaporating a substance.

Based on the above-mentioned method, the present invention detects variations in the amount of infrared energy emitted from the substrate surface using an infrared radiation thermometer, and adjusts the opening diameter and opening time of the evaporation source storage container according to the changes in the detected energy. Another feature is that the crystal growth is controlled by adjusting the heating temperature and the like.

(Function) Since the present invention is configured as described above, a variation in the amount of infrared radiation energy from the outermost atomic layer of the substrate is detected by an infrared radiation thermometer. Then, the opening diameter, opening time, heating temperature, etc. of the evaporation source storage container are adjusted in accordance with the detected energy change.

(Effects of the Invention) According to the molecular beam epitaxial growth method of the present invention, crystal growth can be controlled by directly detecting changes in the state of the substrate. There will be nothing to do.

In addition, since changes in the amount of infrared energy are detected using an infrared radiation thermometer, for example, as described in Japanese Patent Application Laid-open No. 59-92998,
Compared to methods that measure the interference effect of infrared rays caused by differences in the refractive index of atomic layers, it is possible to control the growth of atomic layers with higher precision.

(Embodiment of the present invention) Inside the ultra-high vacuum chamber 1, a temperature controller 3 for heating the GaAs substrate 2 is provided, and evaporation source storage containers 4 and 5 are provided below the GaAs substrate 2.

One container 4 stores gallium Ga, and the other container 5 stores arsenic As.
Further, this container is heated by a heater (not shown) to evaporate gallium Ga and arsenic As, which are evaporation sources, and grow crystals on the surface of the GaAs substrate 2.

As mentioned above, above the containers 4 and 5 containing the evaporation sources, there are shutters 6 and 7 that open and close the openings of the containers 4 and 5.
The shutters 6 and 7 are arranged so that the opening time of the containers 4 and 5 can be adjusted, and the opening diameter thereof can also be adjusted.

Further, the ultra-high vacuum chamber 1 is provided with a viewing port 8, and an infrared radiation thermometer 9 is provided outside the viewing port 8.
This infrared radiation thermometer 9 is for detecting infrared energy radiated from the surface of the GaAs substrate 2.

In other words, any substance, if its temperature is above absolute zero, emits infrared rays corresponding to its own temperature. Therefore, if a predetermined atomic layer grows on the surface of the substrate 2, infrared rays corresponding to the atomic layer will be emitted. Its infrared radiation energy (W) is a function of absolute temperature (T°K), W
= εσT ⁴ (ε is emissivity, σ is Stephan-Boltzmann constant).

By detecting the temperature of the infrared rays according to this atomic layer,
It is this infrared radiation thermometer 9 that determines the growth status of the atomic layer.

Therefore, in order to grow crystals on the substrate 2, first, the GaAs substrate 2 is heated to 600°C using a temperature controller 3.
The oxide layer on the surface of the substrate is removed by heating to a certain degree.
When the oxide layer is removed in this way, the arsenic on the substrate 2 is scattered, so sufficient arsenic is irradiated to replenish it.

The outermost atomic layer on the surface of the substrate 2 from which the oxide layer has been removed in this manner becomes an arsenic atomic layer 10, as shown in FIG. 2a.

Next, the shutter 6 of the evaporation source container 4 is opened to start GaAs growth. In this case, the Ga atom is
It flies onto the arsenic atomic layer 10, which is the outermost atomic layer on the surface of the substrate 2 before growth, to form a gallium atomic layer 11.

Furthermore, since As atoms are attached only to the locations where the gallium atomic layer 11 is present, the above-mentioned shutter 6,
By alternately opening and closing 7, Fig. 2 a to c
As shown in FIG. 2, arsenic atomic layers 10 and gallium atomic layers 11 grow alternately.

During the above growth process, the heating temperature of the substrate 2 is kept constant by the temperature controller 3. However, the infrared emissivity from the surface differs depending on whether the atomic layer on the surface is the arsenic atomic layer 10 or the gallium atomic layer 11.

Therefore, by detecting this infrared energy with the infrared radiation thermometer 9, it is possible to grasp the growth status of the atomic layer. The atomic growth can be controlled by controlling the aperture diameter and opening time of the shutters 6 and 7 or the heating temperature of the evaporated substance, taking into account the growth situation of the atomic layer detected in this way.

FIG. 3 shows actual measurement results, and the fluctuation period of the output of the infrared radiation thermometer 9 is clarified. The number of atomic layers grown can be determined from the number of fluctuation cycles.

In the above embodiments, an atomic layer is grown on a GaAs substrate, but it goes without saying that the above method can be applied to all compound semiconductors such as ZnSe and InP, as well as to different metals.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a schematic diagram of a molecular beam epitaxial apparatus, and FIG.
-c is a cross-sectional view of a substrate on which an atomic layer has been grown, and FIG. 3 is a graph showing changes in the intensity of infrared radiation energy of the grown layer. 1... Ultra-high vacuum chamber, 2... Substrate, 4, 5... Evaporation source storage container, 10, 11... Atomic layer.

Claims (1)

[Claims] 1 A substrate is placed in an ultra-high vacuum chamber, and an evaporation source storage container is provided to store an evaporation source for the atomic layer to be grown on the surface of the substrate, and the substance in this container is evaporated to grow a monoatomic layer on the substrate. In the molecular beam epitaxial growth method, changes in the amount of infrared energy emitted from the substrate surface are detected with an infrared radiation thermometer, and the opening diameter, opening time, or heating of the evaporation source storage container is adjusted according to the changes in the detected energy. A molecular beam epitaxial growth method that controls crystal growth by adjusting temperature, etc.