JPH0322410A - Formation of semiconductor thin film - Google Patents

Abstract

PURPOSE:To form a semiconductor film having a fine pattern without using lithographic technique by growing a GaAs film while irradiating a substrate with an argon laser beam from outside of a vacuum container in a metal organic molecular beam epitaxial process. CONSTITUTION:In an metal organic molecular beam epitaxial process(MOMBE), wherein a semiconductor thin film is formed on a single crystal substrate 5 by using a molecular beam of triethylgallium, which is an organic metal, and a molecular beam of a hydride obtained by heat decomposing arsine, a GaAs film is grown while irradiating a substrate 5 with an argon laser beam from outside of a vacuum container 1. In this MOMBE, the film is grown in a vacuum lower than 10<-4>Torr, so that the organic metal molecular beam reaches the substrate 5 without colliding on the residual gas, and individual organic metal molecules scarcely move on the substrate surface. Further, because a window 11 for introducing the laser beam is a flat plate, a fine optical pattern can be projected on the substrate without deformation. Thus, a semiconductor film with the fine pattern can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for forming a compound semiconductor thin film with a controlled structure at any location on a substrate.

(Conventional Technology) Semiconductor devices are becoming more sophisticated and highly functional as a trend of the times. Along with this, the structure of elements has become finer and more complex. In order to meet this demand, in the past, a film with a uniform thickness and composition was formed within the plane, and then an element structure having complex irregularities within the plane was fabricated using advanced lithography technology. Recently, attempts have been made to control the thickness at some locations within the plane of a thin film in order to simplify complex process steps. For example, Applied Physics Letters
ters) Volume 47, 1985, p. As stated in 95,
Using metal organic pyrolysis method (hereinafter abbreviated as MOCVD),
A technique has been developed in which when forming a GaAs film, the substrate is irradiated with an argon laser to form the film only on the irradiated area. The reason for this selection is that the organometallic material is decomposed by light irradiation. It has been reported that not only argon lasers but also low-pressure mercury lamps, excimer lasers, and the like are effective as light sources. however,
Excimer lasers have two drawbacks. First, since the wavelength of the laser matches the absorption wavelength of the organic metal, the organic metal is decomposed not only on the substrate but also in the atmosphere. Second, since it is a pulse oscillation laser, the energy of the pulse is very large, and the temperature rise due to laser irradiation is significant. Due to these drawbacks, a pattern with the same light distribution cannot be obtained.

(Problems to be Solved by the Invention) Up to now, MOCVD has been exclusively used for the film length method for selection and length by light irradiation. For this reason, there was a drawback that fine patterns could not be formed.

The reason is (a) Mocvo, the number 10-76 in the method
Since the film lengthening is performed in a hydrogen gas atmosphere at a pressure of 0 Torr, a flow of organic metal occurs on the substrate, and as a result, the shape of the selective membrane becomes gentle. (b) The lengthening container, that is, the reaction tube is made of glass. This is because the cylindrical shape of the substrate makes it impossible to project a fine optical interference pattern onto the substrate. Furthermore, whether or not selective strength is possible depends on the conductivity type of the substrate; it is possible with n-type substrates, but not with semi-insulating substrates. This is a major constraint when applying selection or length to devices.

(Objective of the Invention) The present invention was proposed in order to improve the above-mentioned drawbacks, and its purpose is to provide a semiconductor thin film form or method that can form a semiconductor film having a fine pattern without using lithography technology. It is in.

(Means for Solving the Problems) In order to achieve the above object, the present invention uses molecular beams of triethyl gallium (TEGa), an organic metal, and molecules of hydride obtained by thermally decomposing arsine (ASH3) in a vacuum container. In the organometallic molecular beam epitaxy method, in which a semiconductor thin film is formed on a single crystal substrate using a GaA
The gist of the invention is a semiconductor thin film structure or method that is characterized by performing S film lengthening.

(Function) The present invention combines the film length method with the organometallic molecular beam method (hereinafter referred to as MOMBE).
) is used, and MOMB[! Then 10-4To
Since film lengthening is performed at a vacuum degree of rr or less, the organometallic molecular beam reaches the substrate without colliding with residual gas, and individual organometallic molecules hardly move on the substrate surface. Furthermore, since the window through which the laser beam is introduced is a flat plate, it has the effect of projecting a minute optical pattern onto the substrate without deforming it. In other words, is the present invention MO? By irradiating an IBE with a ^r laser, a semiconductor thin film with a fine pattern can be changed.

(Example) Next, examples of the present invention will be described.

It should be noted that the embodiments are merely illustrative, and it goes without saying that various changes and improvements can be made without departing from the spirit of the present invention.

FIG. 1 is a structural diagram for explaining an embodiment of the present invention, and in the figure, 1 is a vacuum container, 2 is an arsine cylinder,
3 and 7 are mass flow controllers (hereinafter abbreviated as MFC)
, 4 is a pyrolysis cell, 5 is a GaAs substrate, 6 is an organometallic cylinder, 8 is an organometallic molecular beam cell, 9 is an argon laser, IO is a lens, and 11 is a window.

(Example 1) An example in which a spot-shaped GaAslli was selected or lengthened using an argon laser will be described. First, vacuum container l is 1 0
-'' Torr high vacuum. 100% arsine was used as the arsenic raw material Hi-4 dry gas.

The flow rate of arsine from cylinder 2 is 6cc using MFC3.
An arsenic molecular beam was formed in the pyrolysis cell 4, which was set at 950°C and heated at 950°C. Since hydrogen was produced during thermal decomposition, the degree of vacuum in the vacuum vessel increased to about 10-4 Torr.

The GaAs substrate 5 was heated to 600° C. while being irradiated with an arsenic molecular beam to clean the substrate surface, and the substrate temperature was lowered to 425° C. while being irradiated with an arsenic molecular beam. Triethyl gallium (hereinafter abbreviated as TEG) is an organic metal used as a raw material for gallium.
Open TEG cylinder 6 using , and check the flow rate? lFC
7, and the TEG molecular beam was irradiated toward the substrate from the organometallic molecular beam cell 8. In this way, we began to refine the GaAs film. After several minutes, a laser beam with an intensity of 500 mW was emitted from the argon laser 9.

The laser beam was focused using a lens 10 and irradiated perpendicularly onto the GaAs substrate through a window 11. At that time, the diameter of the laser beam was adjusted to 400 μm. An hour later T[! The supply of G was stopped, and the growth of the GaAs film was completed. At the same time, the laser beam irradiation also stopped. Spot-like protrusions were observed in the laser irradiated portion of the film thus produced.

FIG. 2 shows the height distribution of the spot cross section. Reflecting the laser light intensity distribution, there is a Gaussian distribution with a diameter of 400 μm.

As shown in the figure, the spot height increases in direct proportion to the laser intensity. This means that the increase in the growth rate of GaAs by this method is a photoreaction. Incidentally, the increase in growth rate due to argon laser irradiation was similarly observed when TEG was used as the gallium raw material and metallic arsenic was used instead of arsine as the arsenic raw material.

FIG. 3(A) shows the substrate temperature dependence of the elongation speed of the laser irradiated part and the non-irradiated part. The (TI) diagram shows the growth rate of the thin film on the substrate. From the above results, the effect of laser irradiation is preferably achieved when the substrate temperature is in the range of 400 to 550°C. This temperature dependence was exactly the same for n-type, p-type, and semi-insulating substrates.

FIG. 4 shows the relationship between laser power and selective elongation velocity.

The diameter of the laser beam in this case is 400 μm.

(Example 2) Next, an example in which a striped pattern is formed will be described. Fifth
The figure shows a diagram of the configuration of the device used in the present invention.

In the figure, l is a vacuum container, 2 is an arsine cylinder, 3 is a mass flow controller), 5 is GaAsaFi, 6
is an organometallic bomb, 7 is a mass flow controller, 8 is a molecular beam cell for organometallic, 9 is an argon laser, 10 is a lens, 11 is a window, l2 is a beam expander, l3
indicates a mask.

A GaAs substrate was prepared in the same manner as in Example 1, and TEG
A GaAs film was fabricated by irradiating with . However, once the laser beam is transferred to the beam expander 1,
The laser beam is enlarged to a diameter of 5 m using a lens 10, and then is diffracted by passing through a glass plate coated with metal in stripes with a pitch of 1 mm, that is, a mask, and then a diffraction pattern is formed on the substrate using a lens 10. focused.

7 Figure 6(a) shows the cross-sectional shape of the film in the laser irradiated area, and seven lines with a width of 90 μm can be seen. This shape matched well with the light intensity distribution shown in Figure ([I).

Therefore, by forming a desired pattern using various optical devices, a film having the desired pattern can be formed. In fact, as a result of forming a fine pattern using holographic technology, we were able to obtain a film with stripes of 4 chron pitch.

(Effects of the Invention) As explained above, according to the present invention, a monomer is produced using a molecular beam of triethyl gallium (TEGa), which is an organic metal, and a molecular beam of a hydride obtained by thermally decomposing arsine (ASH3) in a vacuum container. In the organometallic molecular beam epitaxy method for forming a semiconductor thin film on a crystal substrate, Ga is
By performing As film lengthening, a pattern having complex irregularities at desired locations on the substrate can be formed without using lithography technology. Optical/electronic integrated circuit (OEIC)
) is expected to be a key device in the future, but to fabricate it, it is necessary to repeat the film lengthening process several times.

Many crystal defects occur at the re-elongated interface, which is the biggest cause of deterioration in device performance. The method of the present invention is OEIC
If applied to
Since no defects are generated at the interface, it is extremely useful for improving the performance and reliability of devices.

In the example, an example of manufacturing GaAs was shown, but In
Selective strength has been confirmed in binary compounds such as P and GaP. From these results, it is easily predicted that it is possible to select ternary and quaternary compounds.

[Brief explanation of drawings]

Fig. 1 shows the apparatus used in the present invention, Fig. 2 shows the height distribution of the cross section of the spot, and Fig. 3 (a) shows the relationship between the elongation velocity of the laser irradiated part and the non-irradiated part and the substrate temperature, ([ I) is the growth rate of the thin film on the substrate, FIG. 4 is the relationship between laser power and selective growth rate, FIG. 5 is the apparatus used in the second embodiment of the present invention, and FIG. Cross-sectional shape of the film in the laser irradiated area, (
El) indicates the light intensity distribution. 1...Vacuum container, 2...Arsine cylinder, 3,7.
... Mass flow controller, 4... Pyrolysis cell, 5.
...GaAs substrate, 6...Organic metal cylinder, 8...
Organic metal cylinder, 9... Argon laser, 10...
・Lens, 11...Window, l2...Beam expander, 13...Mask.

Claims (1)

[Claims] Triethylgallium (TE), an organic metal, is
In the organometallic molecular beam epitaxy method, which forms a semiconductor thin film on a single crystal substrate using a molecular beam of Ga) and a molecular beam of hydride obtained by thermally decomposing arsine (AsH_3), an argon laser beam is applied to the substrate from outside the vacuum chamber. A semiconductor thin film forming method characterized by growing a GaAs film while irradiating the top.