JP2861345B2 - Method for manufacturing semiconductor film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention forms a polycrystalline Si thin film to be a semiconductor active layer when an electronic device is manufactured by integrating elements such as thin film transistors on an insulating substrate. To a manufacturing method.

(Prior art) Conventionally, as a manufacturing method of forming a polycrystalline Si thin film on an insulating substrate, an amorphous Si thin film is deposited on the insulating substrate, and a heat treatment such as a furnace annealing method or a laser annealing method is performed. Accordingly, a method of polycrystallizing by spontaneously growing a solid phase around a nucleus contained in an amorphous Si thin film has been used. However, in the above method, the position and the number of polycrystallized grains are difficult to control because of the spontaneous solid phase growth, and it is difficult to make large grains due to poor crystallinity of the grains. Was.

Therefore, in recent years, heat treatment has been performed on Si
A method has been proposed in which a nucleus is formed by crystallization by an aggregation reaction, and a polycrystal is grown around the nucleus.

In this method, a Si thin film deposited on an insulating substrate is finely patterned into a plurality of dot-separated shapes, followed by heat treatment, nucleation of crystalline Si by an agglutination reaction, and CVD using individual crystalline Si as nuclei. A polycrystal is grown around the nucleus by vapor phase growth by a method. According to this method, it is easy to control the number and position of crystal Si nuclei,
There is an advantage that large grains can be obtained.

(Problems to be Solved by the Invention) However, according to the above-described method, a high-temperature process for raising the temperature of the insulating substrate to a high temperature (700 to 1000 ° C.) is required when performing vapor phase growth. In a large-area device such as a liquid crystal display, since a glass substrate that cannot be subjected to a high-temperature process is used as an insulating substrate, there is a problem that the above method cannot form a polycrystalline Si thin film on a glass substrate. .

The present invention has been made in view of the above circumstances, and has as its object to provide a method for manufacturing a semiconductor film capable of forming a polycrystalline Si thin film composed of a large aggregate of grains on a glass substrate.

(Means for Solving the Problems) A method for manufacturing a semiconductor film according to the present invention for solving the problems of the above conventional example is characterized by comprising the following steps.

As a first step, a single domain nucleus made of crystalline Si is formed by an agglomeration reaction by finely patterning a Si thin film deposited on an insulating substrate into a plurality of dot-separated shapes and performing heat treatment.

As a second step, an amorphous Si film is formed so as to cover the single domain nucleus.

As a third step, heat treatment is performed in a temperature range higher than the melting point of amorphous Si and lower than the melting point of crystalline Si, and the amorphous Si is melt-crystallized around the single domain nucleus.
The whole film is made of polycrystalline Si.

(Function) According to the method of the present invention, the amorphous Si film deposited so as to cover the single domain nucleus is made of amorphous Si by utilizing the fact that the melting point of amorphous Si is different from that of crystalline Si. Is performed in a temperature range higher than the melting point of the crystalline Si and lower than the melting point of the crystalline Si. According to this process, when Si that has temporarily become a liquid phase becomes a solid phase, it is melted and recrystallized around the single domain nucleus that remains as a solid phase, and the entire amorphous Si film becomes large grains. Polycrystalline Si having the following formula:

Example An example of a method for manufacturing a semiconductor film according to the present invention will be described with reference to FIGS.

An amorphous Si film 2 is deposited on a glass substrate 1 by LPCVD to a thickness of 200 ° (FIGS. 1 (a) and 2 (a)). Next, the amorphous Si thin film 2 is formed to a thickness of 5 μm by photolithography.
A plurality of dot separating portions 2a having a size of 3 × 3 μm at a pitch are finely patterned into a plurality of rows (FIGS. 1 (b) and 2 (b)).

Excimer laser light (KrF, wavelength 24
When heat treatment is performed by irradiating 8 nm and an energy density of 400 mJ / cm ² ), the dot separation part 2 a is melted and becomes a liquid phase. At this time, since the volume of each liquid phase is small, the liquid phase aggregates due to surface tension, and when cooled from the glass substrate 1 side, when the liquid phase becomes a solid phase, a single domain nucleus composed of a single crystal having a diameter of 0.7 μm or less is formed. 2b
(FIG. 1 (c), FIG. 2 (c)). Before the heat treatment, the dot separation part 2a is amorphous, but after the heat treatment and cooling, the dot separation part 2a becomes a single domain nucleus composed of single crystal Si because of its small volume.

Next, an amorphous Si film 3 is deposited on the glass substrate 1 to a thickness of 1000 ° by LPCVD so as to cover the single domain nucleus 2b (FIGS. 1 (d) and 2 (d)). )).

Excimer laser light (KrF, wavelength 24
Heat treatment is performed by irradiating 8 nm with an energy density of 350 mJ / cm ² ). This heat treatment controls the energy density of the laser beam so that the temperature is higher than the melting point of amorphous Si (1350 ° K) and lower than the melting point of crystalline Si (1683 ° K). By this process, only the amorphous Si film 3 is melted without melting the single domain nucleus 2b, and when the temporarily liquid Si is cooled from the glass substrate 1 side to become a solid, A plurality of domains 3a melt and recrystallize around each single domain nucleus 2b existing in a phase. This melt recrystallization is considered to be a mechanism of rapid cooling after heat treatment, the solidified part from the liquid phase releases solidification energy, and the surrounding amorphous pair is melted. Is crystal growth from the liquid phase, and it is considered that the domain grain boundary portion at which the temperature is lowered is solid phase growth.
Then, by this melt recrystallization, large grains 4 of 2 to 4 μm having a plurality of domains 3a are formed, whereby polycrystalline Si can be formed over the entire amorphous Si film 3 (FIG. 1 ( e), FIG. 2 (e)).

Since the laser beam used in the heat treatment in the above-described semiconductor film manufacturing method reaches only the deposited amorphous Si film 3 portion, the glass substrate 1 can be heated even if the amorphous Si film 3 portion becomes high temperature. Does not cause thermal damage. Therefore, a polycrystalline Si thin film can be formed on the glass substrate 1 without deteriorating the glass substrate 1. In addition to the laser annealing method, a flash annealing method in which light from a halogen lamp is condensed and irradiated may be used.

(Effects of the Invention) According to the method of the present invention, an amorphous Si film deposited to cover a single domain nucleus is made amorphous by utilizing the fact that the melting point of amorphous Si is different from that of crystalline Si. Heat treatment is performed in a temperature range higher than the melting point of crystalline Si and lower than the melting point of crystalline Si. According to this process, when Si that temporarily becomes a liquid phase becomes a solid phase, it is melted and recrystallized around the single domain nucleus existing as a solid phase, so that a glass substrate that cannot be subjected to a high-temperature process The entire amorphous Si film deposited on the substrate can be polycrystalline Si having large grains. Therefore, a high-quality semiconductor film can be manufactured over a glass substrate.

[Brief description of the drawings]

1 (a) to 1 (e) are cross-sectional explanatory views of a manufacturing process of a semiconductor film according to a method embodiment of the present invention, and FIGS. 2 (a) to 2 (e).
FIG. 3 is an explanatory plan view of a manufacturing process of a semiconductor film according to a method embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Glass substrate 2 ... Amorphous Si film 2a ... Dot separation part 2b ... Single domain nucleus 3 ... Amorphous Si film 3a ... Domain 4 ... Grain

Claims (1)

(57) [Claims] A step of finely patterning an Si thin film deposited on an insulating substrate into a plurality of dot-separated shapes, and forming a single domain nucleus made of crystalline Si by an agglutination reaction by performing a heat treatment; A step of depositing amorphous Si so as to cover one domain nucleus, and performing a heat treatment in a temperature range higher than the melting point of amorphous Si and lower than the melting point of crystalline Si to melt around the single domain nucleus Converting the entire amorphous Si film into polycrystalline Si by recrystallization.