JPH0745356B2 - 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> For example, when a GaAs thin film is formed on a Si substrate by the MBE method or MOCVD method, simply epitaxially growing it may cause threading dislocations or the like due to mismatch of lattice constant, difference in polarity or thermal expansion coefficient, etc. Crystal lattice defects occur. Therefore, in order to reduce such threading dislocations, the strained superlattice method has heretofore been used in which several combination thin films such as InGaAs and GaAs or AlGaAs and GaAs are laminated.

Repeated heat treatment (annealing) is performed during film formation.

Doping impurities such as Si at a high concentration.

Etc. are adopted.

<Problems to be Solved by the Invention> By the way, according to the strained superlattice method, not only the number of elements constituting the thin film is increased, but also the structure of the device and the control of film formation become very complicated.

Further, according to the annealing method, it takes a considerable time to return the substrate to the low temperature after the substrate is heated to the high temperature, and the impurities are diffused. Moreover, since the annealing temperature is higher than the temperature at the time of film formation, there are many restrictions on the manufacturing process.

Furthermore, according to the high-concentration doping method, an element such as Si is additionally required, and the crystallinity may be lowered due to the impurity diffusion of the high-concentration layer.

The present invention has been made in view of the above problems, and it is a simple procedure and a high-quality Ga with few threading dislocations in a short time.
It is intended to provide a method capable of producing an As thin film and the like.

<Means for Solving the Problems> In the thin film manufacturing method according to the present invention, a plurality of vapor deposition materials are evaporated by heating in a vacuum atmosphere, and the plurality of vapor deposition particles are irradiated on the surface of the substrate, and thus the substrate is exposed. In the method of forming a thin film composed of a compound of a plurality of vapor deposition particles on the surface, by changing the irradiation energy to the substrate of the plurality of vapor deposition particles, on the substrate surface, the compound of the compound by low energy irradiation first. It is characterized in that the layers are stacked to form a layer of the compound by high energy irradiation as a buffer layer, and then a layer of the compound by low energy irradiation.

<Operation> By changing the irradiation energy of the vaporized particles to the substrate, a layer formed by low energy irradiation, a layer formed by high energy irradiation, and a layer formed by low energy irradiation are laminated on the substrate surface.
The dislocations generated at the interface with the substrate at the time of stacking the first layer and the second layer bend at the interface with the upper layer in the direction along the interface, thereby reducing threading dislocations. Moreover, by making the energy of the vaporized particles that first irradiate the substrate low, damage to the substrate surface can be reduced.

<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 material is blown out from the injection holes 21a and 31a, respectively, to form a cluster (lumped atomic group), which advances in the vacuum chamber 1,
Both of the clusters reach the same substrate S installed in the same vacuum chamber 1.

On the cluster traveling path between each evaporation source 2, 3 and the substrate S,
The ionization units 4 and 5 and the acceleration electrodes 6 and 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 the shutters 8 and 9, the substrates S of the clusters from the evaporation sources 2 and 3 are disposed. You can choose to proceed to.

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 cluster is configured to be positively ionized by attracting and irradiating the cluster from each evaporation source 2, 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 including, 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. Next, with each of the evaporation sources 2 and 3 being driven, and with only the ionization section 5 on the As evaporation source side being driven, only the shutter 9 on the As evaporation source side is opened, and a voltage of about 1.3 kV is applied to the surface of the substrate S. Accelerated As
The surface of the substrate S is cleaned by irradiation with cluster ions (a).

Next, the driving of the ionization section 5 on the As evaporation side is stopped, and
The shutter 8 on the Ga evaporation source side is opened, and the surface of the substrate S is irradiated with Ga and As clusters without ionizing and accelerating, and the first buffer layer B ₁ is laminated on the surface of the substrate S (b). The thickness of the buffer layer B ₁ is about ₁ to 1.5 μm.

Next, the ionization units 4 and 5 are driven to irradiate the surface of the substrate S with Ga and As cluster ions accelerated at a voltage of about 1.3 kV, and the first buffer layer B ₁ on the substrate S is irradiated. The second buffer layer B ₂ is laminated (c). This buffer layer
The film thickness of B ₂ is also about 1 to 1.5 μm.

Then, the driving of the ionization sections 4 and 5 is stopped, and Ga and As clusters are irradiated onto the surface of the substrate S without ionizing and accelerating them to epitaxially grow a GaAs thin film on the second buffer layer B ₂ (d). The thickness of this GaAs thin film T is 1 to 1.5
It is about μm.

By the way, Ga and As cluster ions are accelerated and irradiated at 1.3 kV on the Si substrate surface, and then the respective clusters are irradiated without ionization and acceleration, and GaAs is grown on the Si substrate by two-step growth. Forming a thin film,
When a TEM (Transmission Electron Microscope) image was taken, dislocations generated at the interface between the Si substrate and the GaAs film (buffer layer) as shown in the drawing in Fig. It was confirmed that the amount decreased in the vicinity of the interface between the layer and the main layer. This is because a force for laterally bending dislocations acts on the interface between the buffer layer and the main film formation layer.

On the other hand, a GaAs thin film is formed on the Si substrate surface by two-step growth without ionizing and accelerating Ga and As.
When the TEM image of the GaAs thin film was photographed, the dislocation state shown in the drawing of FIG. 4 could be observed. As is clear from comparison between FIG. 4 and FIG. 3, the GaAs film first deposited on the Si substrate has less damage to the Si substrate surface without ionization and acceleration, and also has a dislocation density. Few.

From these observations and examination results, it can be said that the method of the present invention according to the above procedure is an effective thin film manufacturing method for obtaining a good quality GaAs thin film with less damage on the Si substrate surface and less threading dislocations.

In the above procedure, if the steps (c) and (d) are repeated, the number of opportunities for laterally bending dislocations increases, and threading dislocations can be further reduced.
In this case, the film thickness in each step is reduced so that the total film thickness is about 4 μm.

In the steps (b) and (d), Ga and As
Although the clusters are irradiated onto the substrate without ionization / acceleration, for example, the ions in each cluster may be accelerated to low energy, for example, accelerated to about 0.1 kV and irradiated onto the substrate surface. In short, the incident energy of each cluster on the substrate in the step (d) 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, it is possible to obtain a high-quality thin film in which the number of threading dislocations is extremely small only by changing the irradiation energy of evaporated particles to the substrate. With this, for example, when forming a GaAs thin film on a Si substrate,
Both the facilitation of the film forming process and the shortening of the film forming time can be achieved, and unnecessary elements are not mixed into the constituent elements of the thin film.

[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. 3 and 4 are TEM images of GaAs thin films formed on a Si substrate by two-step growth. 1 ...... vacuum chamber 2 ...... Ga evaporation source 3 ...... As evaporation sources 4,5 ...... ionizer 6,7 ...... accelerating electrode S ...... Si substrate B _1, B ₂ ...... buffer layer T ...... GaAs thin film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroyuki Kishihara, No. 1 Nishinokyo Kuwabara-cho, Nakagyo-ku, Kyoto City, Kyoto Prefecture Shimazu Corporation Sanjo Factory (72) Inventor Yu Kobayashi, Nishinokyo-Kuwabara-cho, Nakagyo-ku, Kyoto, Kyoto Stock Shimadzu Corporation Sanjo Factory (56) References JP-A-59-204282 (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, by changing the irradiation energy to the substrate of the plurality of vapor deposition particles, on the substrate surface, a layer of the compound by low energy irradiation first, then a layer of the compound by high energy irradiation. A method of manufacturing a thin film, characterized in that the respective layers are formed as a buffer layer, and further, a layer of the compound is formed by low-energy irradiation, and the layers are stacked.