JPS59193022A - Heating of thin film - Google Patents

Abstract

PURPOSE:To enable to heat selectively only the desired part of a thin film formed on a substrate by obtaining intense absorption of a laser beam according to the interference effect by a method wherein film thickness of the heating necessitating part of the thin film is so selected as to make light volume of the laser beam to irradiate therein large, and the laser beam is made to irradiate thereto. CONSTITUTION:A thin film 2 having the refractive index of n2 and having film thickness of (d) is interposed between layers 1, 3 having respectively the refractive indexes of n1, n3, and monochromatic light 4 having the wavelength of lambda is irradiated from the layer 1 side. When relation n1, n3<n2 exists between the refractive indexes, and the expression 1 of 2d=Nlambda/n2 (N is a natural number) is satisfied, light volume made to enter in the film 2 becomes to the maximum according to the interference effect. Moreover when the expression 2 of 2d= (N+1/2)lambda/n2 is satisfied, light volume to transmit in the film 2 becomes to the maximum. When the interference effect of a small absorption coefficient can be obtained according to the expressions 1, 2 thereof, by controlling film thickness (d) of the thin film 2, ON, OFF control of heating to the same incident light volume of the laser beam can be attained. Namely, it is favorable to satisfy the expression 1 when heating is necessary, and to satisfy the expression 2 when heating is unnecessary.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of heating a thin M formed on a substrate using laser light.

Backlighting technology and its problems For example, forming polysilicon on a substrate and performing heat treatment.As in the case of forming Kyop1 crystalline silicon, heating a thin film deposited on a substrate and crystallization,
Recrystallization, annealing, etc. may be performed. Conventional heating methods used in such cases include di-heater heating,
Lamp irradiation heating, electron beam irradiation heating, laser beam irradiation heating, etc. are known.

However, in heater heating and lamp irradiation heating, not only the thin film but also the substrate on which it is deposited are heated, so it is difficult to use a heat-sensitive material for the substrate or to attach the above-mentioned material to the substrate. I can't. Although electron beam irradiation heating and laser beam irradiation heating can heat only a thin film, only the layered portion of the thin film is heated, and it is difficult to heat the entire film in the thickness direction. Further, when a plurality of R films are stacked, it is impossible to heat only a desired intermediate layer by electron beam irradiation heating. In laser light irradiation heating, the wavelength of the laser light can be used to obtain large optical absorption in the thin film being heated. However, when heating only the intermediate layer as described above, the light absorption of each layer on the irradiation side (upper side) of the intermediate layer must be small.

Purpose of the Invention The present invention is capable of selectively heating only a desired portion in the case of a single-layer thin film, and uniformly heating the entire thickness of the film, and in the case of a multi-layer thin film. The present invention provides a thin film heating method using laser light that can selectively heat only a desired portion of a desired intermediate layer.

Summary of the Invention The present invention is designed to perform laser beam illumination by selecting the thickness of the heated portion of the thin film and utilizing the interference effect.

Example As shown in FIG. 1, the refractive index n1. Monochromatic light (4) with a wavelength λ is applied to the IN film (2) having a film thickness d1 and a refractive index n2 disposed between the layer (1) (3+)
) side fc, when n1+n3<n2 is satisfied, the amount of light injected into the thin film (2) becomes maximum due to the interference effect. When satisfying also, the amount of light transmitted through the thin film (2) becomes maximum.

According to the above formulas ① and ②, if the extinction coefficient is relatively small and an interference effect is obtained, by controlling the film thickness d of the thin film (2), the heating will be 0N-O for the same amount of incident laser light.
It can be seen that FF control or TiI function is possible.

In other words, if heating is required, d
If you choose d and do not require heating, it is good to choose d so as to satisfy formula (■). Furthermore, if the film thickness cannot be freely selected, the wavelength λ may be selected to satisfy the equation 0 or the equation (2).

An exciting thin film heating method applying the above method will be described below.

Example 1 In a single layer structure in which a single layer of thin film (6) is deposited on a substrate (5) as shown in FIG.
When the thin film (6) is uniformly irradiated with 7), the entire thin film (6) can be heated by selecting the film thickness d so as to satisfy the above equation 0.

This method is not much different from conventional single-beam irradiation heating and laser beam irradiation heating, but in contrast to these, heating is performed only in the central area, in case 8 of the method of the present invention, heating is performed in the film thickness direction. It is advantageous in that it can be heated as a whole.

Example 2 When a thin film (8) is deposited in a single layer on a substrate (5) as shown in FIG.
When selectively heating only part 8a), the above part (8a)
) is selected so as to satisfy equation 0, and the other parts (
The film thickness d2 in 8b) should be selected to satisfy the formula (2). In addition to the condition of formula (■), dl is dl<2. (
n' refractive index). When dl is this value, the interference effect is no longer limited, and the maximum amount of transmitted light can be obtained as in equation (2). In addition, d for one thin film (8)
Selection of l and dl can be performed by etching or the like.

In this way, selective heating of the single-layer thin film (8) can be achieved by using light or electron beams 0N-OF' even with conventional methods.
This can be done by F control, but if the part (8a) that requires heating is a fine turn, the device will be large-scale. According to the method of the present invention, heating of fine nodules can be easily performed by using a conventionally known photoringraph technique or the like.

Example 6 As shown in FIG. 4, when the thin film has a multilayer structure consisting of an upper layer (9), an intermediate layer H), and a lower layer U, this is a method in which only the intermediate layer (lO) is heated. In this case, when the absorption coefficient of the intermediate layer (10) and the layer on the irradiation side of the laser beam (7), that is, the upper layer (9), is relatively small and an interference effect is obtained, the upper layer (9) The film thickness d1 satisfies the formula ■ or (h<-
The film thickness j of the intermediate layer α0) can be selected so as to satisfy Σi, and the film thickness d2 of the intermediate layer α0) can be selected so as to satisfy the equation 0. Although FIG. 4 shows the case of a six-layer structure, in the case of two layers or four or more layers, only an arbitrary intermediate layer can be heated based on the same idea. Also, in Figure 4, if only the upper layer (9) is heated, m? Follow the method described in l11.

Furthermore, if heating only the lower layer (Lυ, dll a2
It is sufficient to make it such that d3n1 satisfies the equation (2) or dl(-1d2 (2,), and the equation (2).

The method described above makes it possible to heat the intermediate layer of a 7+ multilayer structure, which is difficult to do with the prior art.

When heating only a desired portion of any layer other than the top layer N in the multilayer structure described above, Example 4.5 described below can be used.
．． 6 methods are performed.

Embodiment 4 FIG. 5 shows a case where only the shaded portion (11a) of the lower layer (1υ) is heated, and FIG. 6 shows a case where only the shaded portion (10a) of the middle layer is heated.

In this example, the film thickness of the upper layer (9) is partially d, , d,
By changing to
Ila) (10a) only is heated. That is, the portion (11a) of the upper layer (9) to be heated (
The film thickness d7 of the portion (9a) corresponding to 10a) is selected to a value that satisfies Equation 0, and the film thickness d1 of the other portion (9b) is selected to a value that satisfies Equation 0. Note that by selecting dl and dl to the above values, the dl portion (9b) is heated, but the method according to this embodiment is used when there is no problem even if the above portion (9b) is heated. .

Embodiment 5 This method is basically the same as the embodiment shown in FIG. 6 described above, and in FIGS.
The film thickness of the layer (11) (101) in which 11a) (10a) exists is partially changed according to the above-mentioned portions (11a) (10a), and the layer above this layer (11) uoJ [7th
In the figure, the middle layer and upper layer (9), in Figure 8, the upper layer (9)]
The film thickness is changed depending on the portions (11a) and (10a). In addition, in the figure, d1. d2. d5 is 0
dl, d2. It is assumed that d3 is selected so as to satisfy the formula 0.

Example 6 The part to be heated (11a) as shown in FIG. 2 and FIG.
This is to partially change the thickness of the layer circle [0] where (10a) exists and the layer above it.

Example 7 Using a method that combines all of Examples 4.5.6, by selecting the film thickness of each layer (9) uO)αυ as shown in FIG. i can be heated. According to this method, multiple layers in a multilayer structure can be simultaneously heated with one irradiation, and each layer can be partially heated.

Example Amorphous silicon (a-8i) deposited on a glass substrate was heated (activated, polycrystallized) using a YAG laser. The same equipment and equipment were used in the two experimental examples described below. The substrate is a soda-free glass substrate (21nchφxO, 5s+s+t) that has been optically polished.
The thin film A-8i, 5in2 was deposited by GD and OVD methods. Each production condition is the same as the lower garment.

A YAG laser is used as the laser oscillator, and the wavelength is 1.0.
6μ, beam diameter I 008m, pulse 12KHz,
The irradiation energy is 1 J/cyt2 or less. The substrate holder can hold the substrate in place using a vacuum chuck.

It is movable in 5X-Y directions by a pulse motor. The laser beam was fixed so that it was incident perpendicularly to the substrate, and the substrate was moved to irradiate the entire surface. Also a
The -Si layer used was not only one made of deposited stone, but also one in which P ions were implanted by ion implantation to aid optical absorption. Here, the conditions for ion implantation are that the acceleration voltage is 10
0 to 250 KeV, dose ft 2 x 10 15 / 2 degrees. Using such equipment, the following two examples of a single layer structure and a laminated structure were tested.

(1) In the case of a single layer structure, as shown in Figure 12, a glass substrate (1511Ca-Si
A layer in which only layer (■6) was deposited was used. At this time,
j Give a uniform gradient to the return thickness d, d = 400 nm
~800 nm. When this sample was irradiated with a constant energy (0.6 J/crrL2) teleser light f over the entire surface Vc, it was confirmed that only the beveled edge portion near the film thickness of 450 nm in d and d km[, JOr+m] was heated. This heated portion appears to be polycrystalline, and the visible light transmittance changes by 9% and the specific resistance decreases between the other portions and the beveled edge portion. Here, even though the entire surface of the substrate was irradiated, only a part was heated, and that part was made to have a film thickness of 450 nm, 60 Or+m, and i degrees, and the other parts did not change at all. It is clear that this is due to an interference effect since there is no difference in the film thickness, and the film thickness corresponds to N=3.4 in each equation 0.

(2) In the case of a laminated structure, as shown in FIG.
6) was deposited, and a SiO2 layer (L7) was laminated thereon. Here, the 5102 layer (17) is also a −S
Similar to the i-layer haze, the film thickness is given a gradient from %100 to 2001.
Distributed over 1 m. If uniform irradiation is performed in this state,
Similarly to the case of the p-single layer structure, it was confirmed that the a-Si layer (16) with a thickness of 600 nm in d-45Dnyr+ and d-d was heated. Until now, irradiation was performed from the thin film side, but similar results were obtained when irradiation was performed from the glass substrate (15) side. (S stacked here
The iO2 layer (17) has a thickness of 100 to 2LJDnmT, and the refractive index of 5in2(7) is 1.45, so the thickness of the iO2 layer (17) is 2d(λ/n+s*), and there is almost no absorption. ) Effects of the invention (1) Conventional laser beam heating could not use wavelengths with weak optical absorption, but in the present invention, by controlling the film thickness, strong absorption can be achieved due to interference effects. It became possible to heat the product.

(2) Rather than heating the entire substrate as in heater heating or lamp heating, only the parts that require heating can be heated preferentially.

(3) Conventional laser beam heating and electron beam heating heat only the surface layer, but in the present invention, each layer of the intermediate layer below the narrow surface can also be heated by 0.1.

(4) It is possible to uniformly irradiate the entire area with a laser beam by simply etching the two-dimensionally distributed areas that require heating in advance, and it is possible to use a beam shielding film like conventional laser heating or electron beam heating. There is no need to provide Also, there is no need for the beam 0N-01;'F.

(5) The six-dimensional distribution of the parts of the laminated thin film that require heating can be achieved simply by uniformly irradiating the entire surface, which is impossible with other methods.

[Brief explanation of the drawing]

FIG. 1 is a side view of a thin film for detailed explanation of the present invention;
2 to 11 are side views showing the structure of a thin film deposited on a substrate showing an embodiment of the invention. Figure 7.8 shows the fifth example, Figures 9 and 10 show the sixth example, and Figure 7.8 shows the fifth example.
FIG. 1 shows the seventh embodiment. FIGS. 12 and 16 are side views showing the structure of the thin film used in the experiment. In addition, in the symbols used in the drawings, (7)...... Laser light (8)...
・・・・・・Thin film (1:Ia)・・・・・・Part to be heated (9
)...... Upper layer (9a)... Part to be heated (10).
・・・・・・・・・Middle class (10a)・・・・・・
Part to be heated (11): Lower layer (11a): Part to be heated. Agent Souvenir Katsu Tsune Kao Yoshi Otosugi Ura Toshiki

Claims (1)

[Claims] A method for heating a thin film, in which the thickness of a portion of the thin film that requires heating is selected so that the amount of laser light injected into the portion is equal to that of the thin film, and the thin film is irradiated with laser light.