JPH0755879B2 - Thin film manufacturing method - Google Patents

Description

The present invention relates to a method for forming a GaAs thin film or the like on a substrate.

<Prior Art> As a semiconductor, GaAs is expected to be applied to high-speed functional devices and optical functional devices. This GaAs has been tried to be thinned by various methods such as MBE method and MOCVD method.
In these cases, a GaAs substrate, a Si substrate or the like is used as the substrate for forming the thin film. In particular, in the case of a Si substrate, since most of the semiconductor elements currently in practical use are Si devices, the functions of these devices and the GaA device can be combined, so various applications are considered. (May 26, 1989, Textbook of the Society of Applied Physics, Crystal Engineering Subcommittee, 92nd Meeting) By the way, when Ga and As are grown heteroepitaxially on a Si substrate, their lattice constant mismatch, polarity and thermal expansion coefficient Due to the difference between the above, a good quality GaAs thin film cannot be obtained. Therefore, conventionally, for example, a so-called two-step growth method of forming a buffer layer on the surface of a substrate at a low temperature and then forming a film on the buffer layer at a high temperature, a method of using a strained superlattice as a buffer, or a MEE method (migration)・ Various methods such as enhanced epitaxy have been tried.

<Problems to be Solved by the Invention> However, according to the above-mentioned three methods, the number of dislocations, that is, threading dislocations, appearing on the surface of the obtained GaAs thin film is very large, and practical film quality is not obtained. is the current situation.

An object of the present invention is to provide a method capable of producing a high quality thin film of GaAs or the like with few threading dislocations.

<Means for Solving the Problems> In the thin film manufacturing method according to the present invention, a plurality of vapor deposition materials are heated in a vacuum atmosphere to be vaporized, and a plurality of vapor deposition particles are irradiated on the substrate surface, thereby the substrate surface. In the method of forming a thin film made of a compound of a plurality of vapor deposition particles on the substrate, the irradiation energy of the plurality of vapor deposition particles to a substrate is changed, and a layer of the compound by high energy irradiation is previously formed on the substrate surface. Then, the layers of the compound are sequentially stacked by low energy irradiation to form a film.

<Operation> When the irradiation energy of the vaporized particles to the substrate is changed and a layer by high energy irradiation and a layer by low energy irradiation are stacked on the substrate surface, dislocations occurred at the interface with the substrate when the first layer is stacked. Bends in the direction along this interface at the interface with its upper layer, which reduces threading dislocations.

<Examples> Examples of the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic configuration diagram of a thin film manufacturing apparatus used for carrying out the method of the present invention.

Two evaporation sources, a Ga evaporation source 2 and an As in the vacuum chamber 1.
An evaporation source 3 is provided. Each of the evaporation sources 2 and 3 contains a vapor deposition material Ga or As inside, and crucibles 21 and 31 having injection holes 21a and 31a in the upper wall body, and lateral sides of the respective crucibles 21 and 31. Heating filament 22 surrounding the periphery,
32, etc., and is configured to vaporize the vapor deposition material inside by heating the crucibles 21, 31 with the heating filaments 22, 32, respectively. Then, the vaporized vapor deposition material is blown out from the injection holes 21a and 31a to form a cluster (lumped atomic group) and advances in the vacuum chamber 1, and both clusters are the same substrate S installed in the same vacuum chamber 1. To reach.

On the cluster advancing path between each evaporation source 2, 3 and the substrate S, an ionization section 4, 5 and an acceleration electrode 6, 7 are sequentially arranged. Further, shutters 8 and 9 are provided between the acceleration electrodes 6 and 7 and the substrate S, respectively.
By operating 8, 9 it is possible to select the progress of the cluster from each evaporation source 2, 3 to the substrate S.

Each of the ionization units 4 and 5 includes ionization filaments 4a and 5a and grids 4b and 5b, and the like.
The thermoelectrons generated by energizing the
The clusters are configured to be positively ionized by attracting and colliding with the clusters from the respective evaporation sources 2 and 3 by b.

The substrate S and the acceleration electrodes 6 and 7 are placed at the ground potential.
Further, a variable DC power source (not shown) is provided between each acceleration electrode 6, 7 and each evaporation source 2, 3, respectively.
It is possible to give a potential difference of arbitrary magnitude between the two so that they have a positive potential. Then, due to the electric field formed by this potential difference, the ionization section 4,
The clusters positively ionized in 5 are accelerated to form an ion beam, which collides with the surface of the substrate S.

The substrate S is held at a predetermined position in the vacuum chamber 1 by a holder 10 equipped with, for example, a heater and a thermocouple, and is maintained at a temperature suitable for film formation.

Now, a procedure for forming a GaAs thin film on a Si substrate using the apparatus described above will be described with reference to FIG.

First, the pre-processed Si substrate S is mounted on the holder 10 in the vacuum chamber 1, the chamber is evacuated, and then the temperature of the substrate S is maintained at a temperature suitable for film formation. Then, with each evaporation source 2, 3 and each ionization unit 4, 5 being driven, only the shutter 9 on the As evaporation source 3 side is opened, and As cluster ions accelerated to a voltage of about 1.3 kV on the surface of the substrate S. Is irradiated to clean the surface of the substrate S (a).

Next, the shutter 8 on the Ga evaporation source 2 side is opened, and the surface of the substrate S is irradiated with Ga and As cluster ions accelerated at a voltage of about 1.3 kV, respectively, and the buffer layer B is laminated on the surface of the substrate S ( b). The thickness of the buffer layer B is about 1.5 μm.

Next, by stopping the driving of the ionization units 4 and 5, and lowering the evaporation sources 2 and 3 to the ground potential, Ga and As
The surface of the substrate S is irradiated with the clusters without ionization / acceleration to grow a GaAs thin film T on the buffer layer B previously stacked (c). The thickness of this thin film is also about 1.5 μm.

Through the above procedure, TE of GaAs thin film grown on Si substrate
A sketch of an M (transmission electron microscope) image is shown in FIG.

The dislocations generated at the interface between the Si substrate and the GaAs film (buffer layer) are reduced at the interface due to changes in ionization and acceleration, that is, near the interface between the buffer layer and the main layer. this is,
This is because a force for laterally bending dislocations acts on the interface between the buffer layer and the main film formation layer. Therefore, as is clear from this TEM image, the method of the present invention is of good quality with few threading dislocations.
It turns out that this is an effective method for obtaining an As thin film.

In the above procedure, if the steps (b) and (c) are repeated, the chance of laterally bending dislocations increases, and threading dislocations can be further reduced.

Further, in the step (c), the Ga and As clusters are irradiated onto the substrate without ionization / acceleration, but for example, the ions of each cluster are accelerated by low energy, for example,
The substrate surface may be irradiated with acceleration at about 0.1 kV. In short, the incident energy of each cluster on the substrate in the step (c) may be selected to be an optimum value capable of obtaining a good quality thin film.

In the above, an example in which the method of the present invention is carried out using a thin film manufacturing apparatus based on the ion cluster beam method has been described, but the present invention is not limited to this, and for example, ion
It is needless to say that the present invention can be carried out by using another thin film manufacturing apparatus capable of arbitrarily changing the irradiation energy of evaporated particles to the substrate, such as a thin film manufacturing apparatus based on the plating method.

<Effects of the Invention> As described above, according to the method of the present invention, the irradiation energy of vaporized particles to the substrate is changed so that a layer formed by high energy irradiation and a layer formed by low energy irradiation are stacked. It is possible to obtain a good quality thin film of which the number is extremely small, which makes it possible to form a practical GaAs thin film on a Si substrate, for example. This expands the possibility of realizing various semiconductor devices that combine the functions of Si devices and the functions of GaAs devices.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of the procedure of the method of the present invention, and FIG. 2 is a schematic configuration diagram of an apparatus used for carrying out the present invention. FIG. 3 is a TEM image of a GaAs thin film grown on a Si substrate by the method of the present invention. 1 ... Vacuum chamber 2 ... Ga evaporation source 3 ... As evaporation source 4,5 ... Ionization part 6,7 ... Acceleration electrode S ... Si substrate B ... Buffer layer T ... GaAs thin film

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kiyoshi Ogawa 1 Nishinokyo Kuwabara-cho, Nakagyo-ku, Kyoto City, Kyoto Prefecture Shimadzu Corporation Sanjo Factory (72) Inventor Hiroyuki Kishihara 1-chome Nishinokyo-Kuwabara-cho, Nakagyo-ku, Kyoto Prefecture Kyoto Stock Shimadzu Corporation Sanjo Factory (56) Reference JP-A-50-32875 (JP, A) JP-A-1-157406 (JP, A) JP-A-53-99762 (JP, A) JP-A-2-180793 (JP, A)

Claims (1)

[Claims] 1. A thin film made of a compound of a plurality of vapor deposition particles on a substrate surface by evaporating a plurality of vapor deposition materials by heating in a vacuum atmosphere and irradiating the substrate surface with the plurality of vapor deposition particles. In the method of forming a layer, the irradiation energy of the plurality of vapor-deposited particles to a substrate is changed, and a layer of the compound is first irradiated with high energy and then a layer of the compound is irradiated with low energy on the substrate surface. 2. A method of manufacturing a thin film, which comprises stacking and forming a film.