JPS6213017A - Semiconductor recrystallizing method - Google Patents

Abstract

PURPOSE:To form a recrystallized region of beautiful grain boundary free by sequentially laminating a noncrystalline silicon layer and a reflection-preventive film on an insulating layer, selectively forming an energy hard-transmitting film on the preventive film, and then emitting a laser light. CONSTITUTION:An insulating layer 2 is laminated on a silicon substrate 1, and a non-single crystalline silicon layer 3 and a reflection-preventive film 4 are grown on the layer 2. A silicon cap 6 is formed on the recrystallized region of grain boundary free to be formed on the preventive film, and swept while emitting an argon ion laser. At this time the film 4 has a function for absorbing most of the emitting energy to the lower layer 3, and an energy hard-transmitting film 6 has a function for reducing the energy absorbed to the layer 3. Thus, the cooling is advanced at the highest speed from the center under the cap 6, the crystal growing nuclide is generated here, and the approx. recrystalline of grain boundary free is formed on the region under the cap.

Description

[Detailed Description of the Invention] [Summary] Semiconductor integrated circuits are usually formed on a semiconductor substrate,
Gra-in Bound Free (Gra-in Bound
The so-called % SOI (Semiconductor On
Development of In5ula-tor technology is progressing.

The present invention describes an improvement in the method of recrystallizing semiconductors on insulating layers.

[Industrial application field]

The present invention relates to a method of growing a grain boundary free region of a semiconductor on an insulating layer without using a seed crystal, that is, forming a growth nucleus during the growth process to form a recrystallized region.

Sol technology is a new technology that significantly reduces stray capacitance because each transistor is formed on an insulating layer, and also eliminates the problem of insulation from adjacent functional elements, making semiconductor integrated circuits faster and more highly integrated. This is the key to contributing to the development of society.

Furthermore, it is attracting attention as a new technology that allows functional elements to be formed three-dimensionally in the vertical direction.

Several methods are being considered for forming a semiconductor grain boundary free region or a single crystal island on an insulating layer.

One of these methods is to open a partial region of an insulating layer formed on a crystalline semiconductor substrate, expose the surface of the substrate, and epitaxially form a single crystal on the insulating film while inheriting the crystallinity of the substrate. There are ways to grow it.

On the other hand, in order to increase the degree of freedom in design, a method has been developed in which a non-single crystal semiconductor layer is deposited on an insulating layer and then irradiated with a laser beam to recrystallize it.

Furthermore, research is also being conducted on a method in which oxygen ions are implanted at high energy into an existing semiconductor single crystal to form an insulating layer at a certain depth within the single crystal.

However, all of them have many technical problems, and further improvements are desired. In the present invention, improvements have been made in the method of recrystallizing the semiconductor layer deposited on the insulating layer in the Sol structure described above.

[Conventional technology]

A conventional method of growing a single crystal region by recrystallizing a semiconductor deposited layer on an insulating layer will be briefly described.

In this method, a patterned antireflection film is formed on a non-single crystal semiconductor layer deposited on an insulating layer, and a temperature distribution that facilitates the formation of crystal seeds is provided by laser irradiation to grow a single crystal. It is.

This will be explained in more detail with reference to a top view and a sectional view shown in FIGS.

An insulating layer 2 such as an oxide film is formed on a silicon substrate 1, and a non-single crystal silicon layer 3 to be recrystallized, such as a polysilicon or amorphous silicon layer, is grown on the insulating layer.

In the case of a polysilicon layer, an antireflection film 4 made of an oxide film, a nitride film, or the like is further laminated on the polysilicon layer. The anti-reflection coating is provided with patterned openings 5 to provide the desired temperature distribution and to form recrystallized regions.

When the laser sweeps the aperture 5 lengthwise, the polysilicon molten region under the antireflection coating cools slower than the aperture if the diameter of the laser beam is larger than the width of the aperture window.

This is because the absorption of light energy in the polysilicon layer under the anti-reflection film is greater than that in the opening, resulting in a higher temperature than in the center of the window.

Therefore, since only one crystal nucleus grows from the center of the opening toward the periphery of the opening, the generation of grain boundaries can be prevented.

[Problem that the invention seeks to solve]

The above-mentioned method of recrystallizing by laser irradiation using an antireflection film having openings utilizes the delicate temperature distribution of the non-single crystal silicon layer, which is quite difficult to control.

The temperature distribution is subtly affected by the structure of the semiconductor layer under the antireflection film or the structure of the laminated layers formed further below.

Particularly in the case of a three-dimensional IC structure that exhibits the characteristics of an SOI structure, this is particularly problematic because the silicon layer to be recrystallized and its underlying structure are often not simply flat surfaces.

As a result, seeds, that is, crystal growth nuclei are generated not only in one place but in multiple places, and the resulting recrystallized structure is
This results in the problem of crystals having complex grain boundaries.

In addition to this, the intensity distribution of the laser beam is usually considered to be a Gaussian distribution, but this is not necessarily simple, and a method that is easier to control and provides a desired temperature distribution is desired.

[Means for solving problems]

The above problem can be solved by sequentially laminating an amorphous silicon layer and an anti-reflection film on an insulating layer, selectively forming a camp layer of a film that is difficult to transmit energy such as polysilicon on the anti-reflection film, and then laser beams. The method of the present invention consists in recrystallizing the amorphous silicon under the cap layer.

[Function] The antireflection film has the function of absorbing most of the irradiation energy into the underlying amorphous silicon layer by controlling its material and film thickness.

Conversely, the energy-impermeable film also has the function of reducing the energy absorbed by the underlying amorphous silicon layer.

Due to the above features, the temperature rise due to laser beam irradiation is lower under the energy-resistant film than in other areas.
During cooling, cooling proceeds from the center. The generation of crystal growth nuclei and the progress of recrystallization become clear, and a beautiful grain boundary-free recrystallized region is formed.

〔Example〕

Figures 1 and 1 show a top view and a cross-sectional view for explaining the recrystallization method according to the present invention.

An insulating layer 2 is laminated on a silicon substrate 1 to a thickness of about 1 μm. The insulating layer is made of an insulating material such as 5iO7 or 5j3N4.

A non-single crystal silicon layer 3 is grown on the insulating layer to a thickness of approximately 4,000 layers. The non-single crystal silicon layer is made of polysilicon or amorphous silicon (a-3t) and is laminated by CVD, vapor deposition, sputtering, or the like.

Generally, a-3t grows at a low substrate temperature of 300° C. or lower, but polysilicon grows when the substrate temperature becomes higher.

An antireflection film 4 is grown on the entire surface of the non-single crystal silicon layer 3. The anti-reflection film is SiO□ film 41 and Si3N4 film 42.
The 5iOz film has a two-layer structure with a thickness of 3 through thermal oxidation.
00 people, S i 3 Na film is 300 people by CVD method
Let each person grow.

Grain boundaries to be formed on the anti-reflection film
A silicon cap 6 is formed in the free recrystallized region.

The silicon cap 6 is made of a polysilicon layer having a thickness of 2,500 to 4,000 nm, and is formed by growing silicon over the entire surface of the substrate by thermal CVD and patterning it into a desired shape.

The size of the silicon cap shown in the top view of FIG. 2 is rectangular with a diameter of approximately 10 to 20 μm.

Sweeping is performed while irradiating the substrate with an argon ion laser. At this time, the antireflection film 4 made of two layers of insulating films has the function of preventing reflection of the irradiated laser beam and absorbing approximately 97% of its energy into the amorphous silicon layer.

At this time, the silicon cap absorbs 40% of the laser beam.
energy is reflected, but 60% of the energy is absorbed by the cap and the underlying non-single crystal silicon layer.

That is, the silicon cap has the function of controlling the amount of energy rays absorbed by the amorphous silicon layer as an energy-resistant film.

Therefore, cooling proceeds fastest from the central part under the silicon cap, generating crystal growth nuclei there, and a grain boundary-free recrystallization region is formed in the region under the cap. .

〔Effect of the invention〕

As explained above, the recrystallization method on an insulating layer of the present invention makes it easy to control the temperature gradient that occurs in the recrystallized region, which greatly contributes to improving the yield of grain boundary-free region formation. be.

[Brief explanation of drawings]

Figure 1 (al, (bl) is a top view and cross-sectional view explaining the semiconductor recrystallization method according to the present invention, Figures 2 (a) and (b) are top views explaining the conventional semiconductor recrystallization method. and a cross-sectional view. In the drawings, 1 is a silicon substrate, 2 is an insulating layer, 3 is a non-single crystal silicon layer, 4 is an antireflection film, 5 is an opening, and 6 is an energy beam transmission film (silicon cap). ) are shown respectively.

Claims (1)

[Claims] A non-single-crystal silicon layer (3) and an anti-reflection film (4) are sequentially laminated on an insulating layer (2), and an energy ray-resistant film (6) is selected on the anti-reflection film. A semiconductor recrystallization method characterized by irradiating laser light after forming a semiconductor.