JP2699608B2 - Single crystal thin film forming method - Google Patents

Description

The present invention relates to a method for forming a single crystal thin film.

[Conventional technology]

Conventionally, in a semiconductor device, there has been a demand to grow a Si single crystal film or an Al single crystal film on an amorphous SiO ₂ film, and several methods have been tried for the Si single crystal film.

For example, after forming an exposed Si portion on the surface of a single crystal Si substrate having an amorphous SiO ₂ film on the surface, forming a polycrystalline Si film on the surface and heating the Si by irradiating an electron beam or a laser beam There is a technique of melting and growing a single crystal on an SiO ₂ film using the exposed Si portion as a seed crystal.

Also, after forming an exposed Si portion on the surface of a single-crystal SI substrate having an amorphous SiO ₂ film on the surface, an amorphous Si film is formed on the surface and the substrate is heated, and the exposed Si portion is used as a seed crystal to form a non-crystal. There is also a technique in which crystalline Si is single-crystallized on a SiO ₂ film in a solid phase.

[Problems to be Solved by the Invention] However, the above-mentioned thin film forming method has a problem that it is difficult to single-crystallize a film of a material different from the substrate.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for forming a single crystal thin film in which a film of a material different from a substrate can be single-crystallized on an amorphous thin film.

[Means for solving the problem]

The structure of the method for forming a single-crystal thin film of the present invention is such that, when a film is deposited on an amorphous thin film, an ion beam or an electron beam is irradiated from a plurality of directions at a low angle with the substrate surface on the substrate surface side. The irradiation direction is set so as to meet the channeling condition of the crystal of the film to be deposited.

In the present invention, the irradiation of the ion beam or the electron beam may be performed from a plurality of directions on the back side of the substrate.

[Action]

The principle of the present invention will be described with reference to FIGS. 2 (a) to 2 (d). The ion beam 3 is applied to the crystal 6 from a specific direction.
Irradiation (or electron beam 3a; the same applies hereinafter) causes a phenomenon called channeling (FIG. 2 (a)). On the other hand, the ion beam 3
Irradiates a non-channeling state as schematically shown in FIG. 2 (b).

In the channeling state and the non-channeling state, the scattering rate of ions (electrons) by the crystal is significantly different, and in the channeling state, the scattering of the crystal per unit volume is smaller. That is, the energy per unit volume that the crystal receives from the ion beam in the channeling state is smaller.

When a crystal is to be grown in a place previously irradiated with the ion beam 3, as shown in FIG. 2 (c), when the crystal grain initially grows in an island shape, the crystal orientation matches the channeling condition. The oriented crystal grains 7 receive less energy of the energy of the ion beam 3 than the crystal grains 8 under the non-channeling condition, so that they can be grown more stably. As shown in FIG. 2 (d), if the ion beam 3 is irradiated from a plurality of specific directions, the crystal grain 10 orientation that can grow more stably is determined to be one, and the orientation of the island-like crystal grain is changed. It will be aligned. Eventually, when the island-shaped crystal grains come into contact with each other, single crystallization proceeds.

However, if ion (electron) irradiation is performed from a high angle on the surface of the substrate, ions are implanted into the underlayer, so that a temperature rise or damage occurs in the underlayer, and the above-described effects are diminished. Therefore, it is necessary to irradiate ions (electrons) from a low angle on the substrate surface or from the rear surface of the substrate.

〔Example〕

1 (a) to 1 (c) are schematic perspective views for explaining an embodiment of the present invention, and show a case where an Al single crystal film is grown on an amorphous SiO ₂ film. First, as shown in FIG. 1 (a), an angle of 1 degree from the surface of a Si substrate 1 having a 500 nm thick SiO ₂ film 2 on the surface and 1.5 degrees from two directions so that the mutual angle is 70.53 degrees. 1 nm by vacuum evaporation of Al at a substrate temperature of 200 ° C. while irradiating a MeV, 0.1 mA / cm ² He ion beam 3
Initiate / sec deposition.

Next, as shown in FIG. 1 (b), the ion beam 3 is continuously applied to a thickness of 50 nm, which is considered to be in a state where the island-like crystal grains having a uniform orientation come into contact with each other and Al becomes a film. Thereafter, as shown in FIG. 1 (c), single crystal growth proceeds without irradiation with the ion beam 3.

In this case, an Al single crystal film is grown such that Al <110> is perpendicular to the substrate and Al <111> is perpendicular to the substrate surface.

In this embodiment, an electron beam (3a) can be used instead of the ion beam 3a. In this case, the irradiation electron beam corresponding to the ion beam of this embodiment is 20
It suffices that it is about 0 keV and about 0.1 mA / cm ² .

FIGS. 3A to 3C are schematic sectional views illustrating a second embodiment of the present invention. Also in this case, the Al single crystal film is grown on the amorphous SiO ₂ film. First, as shown in FIG. 3 (a), a 500 nm thick SiO ₂ film 2
200 keV, 0.1 mA / cm ² from two directions from the back side of the Si substrate 1 from which a part of
At a substrate temperature of 200 ° C., deposition of 1 nm / sec by vacuum evaporation of Al is started in a state where the electron beam 3a is irradiated.

Next, as shown in FIG. 3 (b), the electron beam 3a is irradiated to a thickness of 50 nm, which is considered that the island-shaped crystal grains having a uniform orientation come into contact with each other to form Al into a film. 3
As shown in FIG. 3C, single crystal growth proceeds without irradiation with the electron beam 3a.

In this case, an Al single crystal film grows in the direction perpendicular to the substrate, such as Al <110>, and in the direction along the substrate surface, Al <001>.

In this embodiment, the same ion beam 3 as in the first embodiment can be used instead of the electron beam 3.

〔The invention's effect〕

As described above, according to the present invention, there is an effect that a single crystal film of a substance different from the substrate can be grown on the amorphous thin film while controlling the crystal orientation.

[Brief description of the drawings]

1 (a) to 1 (c) are schematic perspective views illustrating an embodiment of the present invention in the order of steps, FIGS. 2 (a) to 2 (d) are cross-sectional views illustrating the principle of the present invention, and FIG. FIGS. 7A to 7C are perspective views for explaining a second embodiment of the present invention in the order of steps. 1 ... Si substrate, 2 ... SiO ₂ film, 3 ... Ion beam, 3a
...... Electron beam, 4 ... Evaporated Al atoms, 5 ... Evaporated Al, 6
... crystal, 7,8 ... crystal grains under channeling and non-channeling conditions, 9 ... substrate, 10 ... crystal grains grown stably.

Claims (2)

(57) [Claims] When depositing a film on an amorphous thin film, an ion beam or an electron beam is directly irradiated from a plurality of directions forming a low angle with the substrate surface on the substrate surface side, and the irradiation direction of the beam is deposited. A method for forming a single crystal thin film, characterized in that the direction is set so as to meet channeling conditions of the crystal of the film to be formed. 2. When depositing a film on an amorphous thin film, an ion beam or an electron beam is irradiated through the amorphous thin film from a plurality of directions forming a low angle with the substrate on the back surface of the substrate. A method for forming a single crystal thin film, wherein the irradiation direction is set to a direction that matches channeling conditions of a crystal of a film to be deposited.