JPS63196032A - Crystallization of semiconductor thin film - Google Patents

Abstract

PURPOSE:To make it possible to form a single crystal thin film having a large grain diameter by a method wherein a mask layer is selectively formed on the amorphous semiconductor thin film which is partially crystallized, and after said film has been brought in the amorphous state again, it is crystallized for the second time. CONSTITUTION:A process wherein a semiconductor thin film brought into an amorphous state is formed on an insulative substrate 1, a process wherein a part of said thin film 3 is crystallized by annealing, a process wherein the photoresist layer 5 which becomes a mask layer is selectively formed on the partially crystallized region of the semiconductor thin film, namely, crystalline nuclei 4, a process wherein the semiconductor thin film 3 of the part not covered by said mask layer 5 is brought into the amorphous state again, and a process in which the semiconductor thin film 3 is crystallized by performing annealing again are performed. To be more precise, first, the annealing operation is discontinued at the point of time when the crystalline nuclei 4 are partially generated on the amorphous semiconductor thin film 3, then using the photoresist layer 5 formed on the crystal nuclei 4 as a mask, other layer 5 is brought back to the initial state, and as annealing is then performed again, recrystallization makes preferentially from the crystal nuclei 4 which is generated already, and the single crystal semiconductor thin film 7 having large grain diameter can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for crystallizing a semiconductor thin film using solid phase growth.

[Summary of the invention]

The present invention is a method for forming a single crystal thin film using a solid phase growth method, in which a mask layer is selectively formed on a partially crystallized amorphous semiconductor thin film, and after the film is made amorphous again. By crystallizing it again, a single crystal thin film with a large grain size can be obtained.

[Conventional technology]

Conventionally, a polycrystalline (poly)Si layer is formed on an insulating substrate such as quartz by the CVD (chemical vapor deposition) method, and then made into an amorphous state by implanting silicon St'' ions. , a method (solid phase growth method) has been proposed in which a single crystal Si thin film is obtained by solid phase epitaxial growth using annealing.

[Problem that the invention seeks to solve]

According to the conventional solid phase growth method described above, after annealing 5ii
Even if crystallization occurs in a part of the film, a large number of crystal nuclei will occur irregularly in the surrounding area, so single crystal Sir! There was a problem that a film could not be obtained.

In view of the above-mentioned points, the present invention provides a crystallization method capable of obtaining a single crystal semiconductor thin film having a large grain size.

[Means for solving problems]

The method for crystallizing a semiconductor thin film according to the present invention includes a step of forming an amorphous semiconductor layer (31) on an insulating substrate (11), and at least one of the steps of forming an amorphous semiconductor layer (31) on an insulating substrate (11). The process of crystallizing the partially crystallized region by annealing, and the partially crystallized region of the semiconductor thin film, that is, the crystal nucleus (4)
A step of selectively forming a photoresist layer (5) as a mask layer on top, and a semiconductor layer (1I!) in the portion not covered with this mask layer (5). ! There are two steps: a step of making the semiconductor thin film (3) amorphous again, and a step of crystallizing the semiconductor thin film (3) again by annealing.

The amorphous semiconductor thin film (3) may be formed by forming a polycrystalline semiconductor thin film (2) on the insulating substrate +11 and then performing appropriate ion implantation to make it amorphous.
Or! The amorphous semiconductor thin film (3) may be formed directly on the quartz substrate (11) as a substrate, and the mask layer selectively formed on the crystal nucleus (4) may be
) to form a crystal nucleus (4), then a semiconductor thin film (
3) It can be formed by forming a negative photoresist layer (5) thereon, exposing it to light from the back side of the quartz substrate (tl), and developing it.

[For production]

According to the present invention, annealing is first interrupted when crystal nuclei (4) are partially formed in the amorphous semiconductor thin film (3), and then the photoresist layer (5) formed on the crystal nuclei (4) is is used as a mask to return the other regions to the initial amorphous state, and then annealing is performed again.
Recrystallization proceeds preferentially from 4), and a single crystal semiconductor thin film (7) having a size that cannot be obtained by conventional methods is obtained.

〔Example〕

The present invention will be described in detail with reference to the drawings.

First, as shown in FIG. 1A, CvD is deposited on a quartz substrate +11.
A polycrystalline (poly)Si II film with a thickness of about 800
2), silicon St'' is ion-implanted (for example, 2 Xl0IS/cm'', 40 keV) to make it amorphous. Alternatively, an amorphous Si thin film may be formed directly on the quartz substrate 11) by plasma CVD.

Next, as shown in FIG. 1B, the quartz substrate (1) is placed in a furnace and annealed, and the amorphous Si thin film (3
), the annealing is interrupted under conditions that produce partially crystallized regions, ie, crystal nuclei (4), for example, at 600° C. for 5 hours.

Next, as shown in FIG. 1C, S i 71119 (3
After forming a negative photoresist layer (5) on the entire surface of the quartz substrate [11], a g-line (436 nm) (6
Irradiate 1. During this irradiation, as shown in Figure 2, the transmittance of the Si thin film in the amorphous state (see curve A in the same figure) is very small, but the transmittance of the part where the crystal nuclei (4) are generated is S
Since the transmittance of the i-thin film (see curve B in the same figure) is relatively good, the g-line (6) passes through the crystal nucleus (4) and passes through the crystal nucleus (
4) Only the top photoresist layer (5) can be exposed.

Next, as shown in the first diagram, a development process is performed to form crystal nuclei (
4) Selectively form a photoresist layer (5) on top.

Next, as shown in FIG. 1E, silicon ions (for example, 2 /
cm", 40 keV). During this ion implantation, the photoresist layer (5) on the crystal nucleus (4) serves as a mask,
The portions of the Si thin film not covered with the photoresist layer (5) can be selectively made amorphous. That is, through this step, the portions of the Si thin film that have not been recrystallized in the annealing step shown in FIG. 1B but are no longer in a completely amorphous state return to the initial amorphous state.

Next, as shown in FIG. 1F, after removing the photoresist layer (5), the quartz substrate (1) is placed in the furnace and the
During this solid phase annealing, solid phase annealing is performed at 00°C.
While crystal nuclei for recrystallization are newly generated in the Si thin film (3) which has returned to its original amorphous state, recrystallization from the crystal nuclei (4) generated in the first annealing is preferentially performed. As the process progresses, a single crystal Tll film (7) with a large grain size is obtained.

〔Effect of the invention〕

According to the present invention, it is possible to obtain a single crystal semiconductor thin film having a large grain size that cannot be obtained by conventional methods.

[Brief explanation of the drawing]

1A to 1F are process diagrams of the example, and FIG. 2 is a graph showing the measured transmittance of the Si3 film in an amorphous state and a crystallized state with respect to wavelength. +1) is a quartz substrate, c) is a poly-Si thin film, (3) is an amorphous SJ thin film, (4) is a crystal nucleus, (5) is a photoresist layer, (6) is a g-line, (sword is a single crystal thin film It is.

Claims (1)

[Claims] A step of forming an amorphous semiconductor thin film on an insulating substrate; a step of crystallizing at least a portion of the amorphous semiconductor thin film; and a step of crystallizing the semiconductor thin film. A semiconductor thin film comprising the steps of selectively forming a mask layer on a region, again amorphizing the semiconductor thin film in a portion not covered with the mask layer, and crystallizing the semiconductor thin film. Crystallization method.