JPS59128292A - Method for crystallizing thin film - Google Patents

Abstract

PURPOSE:To crystallize semiconductor films left on the flat surface of a substrate in the form of rectangles or stripes, by depositing an insulating film such as a silicon oxide film or a silicon nitride film and by carrying out beam annealing. CONSTITUTION:Thin films 2 of an amorphous or polycrystalline semiconductor are left on a flat glass substrate 1 in the form of rectangles each having <=mum width. An insulating film 4 having 0.1-1mum thickness such as a silicon oxide film or a silicon nitride film is deposited on the whole surface of the substrate 1 by CVD or other method, and beam annealing with laser or electron beams is carried out to crystallize the thin films 2. At this time, edges 5 of the films 2 act as positions where nuclei for growth by recrystallization are stable, so the thin films 2 are converted into crystallized thin films 20 each consisting of coarse grains.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for crystallizing a semiconductor thin film, and in particular to a method for crystallizing a semiconductor thin film.
r) Concerning the method of realizing the structure.

S'OI is attracting attention as a technology that enables improved cylindrical performance, increased areal density, and lower cost of semiconductor devices.

Techniques for this include, for example, a method in which a semiconductor thin film on an oxide model on a semiconductor single-crystal substrate is crystallized on an oxidized film using the substrate as a seed crystal, and a method such as graph-o-epitaxy. Graphoepitaxy is an epoch-making method that allows a single crystal growth layer to be obtained on a substrate such as glass, and an example of the process is shown in FIG. FIG. 1(a) shows, for example, grooves 5 on the surface of a glass substrate 1.
A cross-section of the formed part is shown. A desired shape of the groove 6 is selected depending on the crystal orientation of the thin film to be crystallized. ψ1”Eha,
When it is (100), it has a rectangular or nutrig-like planar shape,
It has a rectangular cross-sectional shape. The width of the hook is 2 to 50 μm,
The depth is 13.1 to 1 μm and is created by photolithographic dry etching at m%. Next, as shown in FIG. 1(b), a semiconductor thin film 2 of amorphous silicon (a-8i), polycrystalline silicon, or the like is deposited on the side surface of the substrate 1.

Furthermore, the thin film is rapidly melted and recrystallized by a so-called beam annealing method using a laser, Oniko ray, Lang source, heater, etc. At this time, the grooves 5 of the substrate 1 function to stabilize the recrystallized growth nuclei, so that the crystal direction of the recrystallized thin film 20 is aligned (see FIG. 1(C)).

However, in this method, the depth of the groove 3 formed in the substrate 1 must be controlled by etching time, and since the entire surface is crystallized at once, the strain in the thin film 2 is large, and in some cases There are problems such as the crank not engaging.

The present invention was made in view of the above-mentioned problems, and an object of the present invention is to obtain a semiconductor thin film that is easily crystallized. In the present invention, on a substrate having a flat surface,
This method attempts to crystallize the semiconductor thin film by leaving the semiconductor thin film in a rectangular or nutrified shape, then depositing an insulating film such as a suspended silicon film or a silicon nitride cord pattern, and beam annealing. At this time, the insulating film at the end of the conductor thin film acts in the same manner as the grooves in the substrate of graphite epitaxy, making it possible to change the crystal direction of the growth nuclei.

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

FIG. 2 shows a schematic diagram of each step of the thin film crystallization method according to the present invention. FIG. 2(a) is a schematic plan view, in which a
-Si or polycrystalline Si semiconductor thin film 2 is left in a rectangular shape. In addition to the above-mentioned glass, the substrate 1 includes a semiconductor wafer such as No. 81 coated with an anti-reflection film, and a semiconductor wafer. Compounds of aluminum chloride and the like can be used depending on the purpose. The thin film 2 is limited to a rectangular shape as shown in FIG. 2(a), but various combinations of rectangular shapes with parallel or ip-intersecting sides, various thicknesses, or a seven-tripe shape can be used. The width of at least 10,000 of the thin film 2 is selected to be about the width of a graphite epitaxy groove, for example, 50 μm or less. Considering the ease of recrystallization in the post-process 7J, the narrower the width, the more desirable it is, and a maximum of 2-10 μm is selected. It is preferable that the end surface 5 of the thin film 2 be perpendicular to the surface of the substrate 1, and the thin film 2 can be selectively etched by a method such as ion etching or reactive ion etching. At this time, since the substrate 1 and the thin film 2 are made of different materials, there are advantages that a large selective etch ratio can be achieved and that the etch end point can be automatically detected. Thin film 2
The thickness is desirably about the depth of a groove in graphoepitaxy, and is selected, for example, from 1 to 1.11 μm. FIG. 2(b) shows a cross section of a substrate 1 as shown in FIG. 2(a) with an insulating film 4 deposited over the entire surface. The insulation @4 is usually made of oxide w<5jo2), nitride film, or a multilayer film thereof, and is formed to a thickness of about 1 to 1 μm by CVD or the like. By depositing this insulating film 4, an insulating wall is formed on the end face 5 of the thin@2, which functions as the groove end of graphoepitaxy. 4 insulating films, 'semiconductor'vw
A material that does not easily deform even when the film 2 is melted, or a material that is transparent to the fcld near-anneal beam is suitable, and aluminum oxide or the like may also be used. After the process shown in FIG. 2(b), when beam annealing is performed, the thin film 2 is crystallized into a single crystal. ! : becomes □ (Figure 2 (C)). As mentioned above, beam annealing is effective using a laser (CWI or bulk), a lamp, a heater, an electron beam, etc., and it is necessary to melt the thin film 2 once and recrystallize it. At that time, the insulating film 4 and the thin film 2
Since the end face 5 moves as a stable position for recrystallization growth nuclei, the thin film 2 transforms into a crystalline thin film 2o whose grain size is J larger. In some cases, all of the island-shaped N-2 can be made into a single crystal,
In that case, the width of the thin film is preferably 10 μm or more. Thereafter, a conductor device such as an island crystal cell 1fi 20 tK-transinuta is fabricated, and an IC having an SOI structure can be realized.

The present invention has further developments as follows. After the process shown in FIG. 2(C), the insulating film 4 is removed and the semiconductor thin film 2 (
a-8j, or polycrystalline 5i) 12 (FIG. 2(d)). If necessary, the second leakage film 12 and the crystalline thin film 20 may be doped with different impurities or at different densities, or the crystalline thin film 2o may be doped with impurities selectively. Thereafter, as shown in FIG. 2 (θ), the first thin film 12 is grown using the crystal thin film 20 as a growth nucleus by VC and annealing.
is crystallized to form a crystal thin film 22 all over the substrate 1.

For annealing, the aforementioned beam irradiation or thermal furnace annealing can be used, and the second thin film 12 can be crystallized by solid phase epitaxy without necessarily needing to be melted. In the case of melting, the beam wavelength, output, time, and film thickness are selected so that at least a part of the crystallized thin 1 odor 20 remains as a solid. The spacing between the island crystal thin films 1 and 20 is usually selected to be about the same or smaller than the width of the thin film 200, and the narrower the distance, the better the time required for annealing the crystallization of the second thin film 12 and the better the crystallinity. This annealing is performed when the width is 10 μm, for example, when laser annealing is performed, A
U0W laser with a diameter of 50μm and a laser output of 10W
It can be carried out at a yarn yarn speed of 1Q □ mm/see, and thermal furnace annealing can be carried out, for example, in hydrogen at 1100° C. for 30 minutes. According to the present invention, when the thin film 2 is crystallized by the first beam annealing, the thin film 2 is divided into islands, so the strain that occurs in the crystallized thin Il#20 is small, and defects such as cranks do not occur. Hateful. In addition, when crystallizing the second thin film 12 by the second annealing, the temperature can be lowered according to the in-phase shrimp, so there is less distortion, even if the semiconductor thin film is crystallized over the entire surface of the substrate. It also has the advantage that defects such as cranks are less likely to occur. In addition, as an example, although we have mainly discussed Sl, [11-4, II-V
It also applies to other semiconductor materials such as 1st class.

The present invention is industrially very important because it is relatively easy to realize an SOI structure, which improves the performance, increases the degree of integration, and lowers the cost of semiconductor devices.

[Brief explanation of the drawing]

Shima 1 Figures (a) to (c) are cross-sectional views for explaining an example of a conventional graphoepitaxy process. Figures 2(a) to 2(,) are diagrams for explaining the present invention in detail.
b) to (e) are cross-sectional views. 1... Glass 7 substrate, 2... Semiconductor thin film, 5...
- Groove, 4... Insulating pattern, 5... Thin film end face, 20... Crystallized thin film, 12... Second semiconductor thin film. No. Im (α゛) Cabinet Cb) (C) No. 2 L, :i ″′-I

Claims (2)

[Claims] (1) 50 μm of amorphous or polycrystalline semiconductor thin film
a step of leaving a nutripe-like or rectangular island-like shape having a width of m or less on the surface of a substrate made of a substance different from the thin film;
In the step of depositing an insulating film on the thin film and the substrate, the boundary between the thin film and the insulating film is A method for crystallizing a thin film, comprising the step of crystallizing the thin film by causing at least a portion of the thin film to act as a stable position for forming growth nuclei. (2) removing the insulating layer after crystallizing the thin film, and further adding a second semiconductor thin film that is amorphous or polycrystalline;
! The method for crystallizing a thin film according to claim 1, comprising: depositing Q, crystallizing the second thin film using the crystallized thin film as a nucleus by beam irradiation or annealing;