JPS6354715A - Beam annealing of semiconductor thin-film - Google Patents

Abstract

PURPOSE:To mass-produce a recrystallized semiconductor thin-film having a large area with excellent reproducibility by depositing an insulating film and a metallic film onto a semiconductor thin-film in succession and conducting specific scanning, projecting energy beams from the back of a transparent insulating substrate. CONSTITUTION:An amorphous or polycrystalline semiconductor thin-film 2, an insulating film 3 and a metallic film 4 are deposited onto a transparent insulating substrate 1 successively, and a first recrystallized region 101 is formed through scanning in the X direction, irradiating said semiconductor thin-film 2 with first energy beams 10 from the back of the substrate 1. A second recrystallized region 201 is shaped through scanning in the X direction, irradiating one part of the first recrystallized region 101 and said semiconductor thin-film 2 adjacent on the Y direction side along the X direction to the region 101 with second energy beams 20 from the back of the substrate 1. In such a beam annealing method for the semiconductor thin-film 2, the second beams 20 have intensity distribution or beam width distribution gradually increasing along the Y direction, and part of the first recrystallized region 101 is irradiated with a section having small intensity or beam width.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for recrystallizing an amorphous or polycrystalline semiconductor thin film on a transparent insulating substrate using an energy beam such as a laser.

[Summary of the invention]

The present invention is a method of enlarging a single crystal region of a recrystallized semiconductor thin film by beam annealing. After sequentially depositing an amorphous or polycrystalline semiconductor thin film, an insulating film, and a metal film on a transparent insulating substrate, a first energy beam is irradiated onto the semiconductor thin film from the back side of the substrate while scanning in the X direction to form a first energy beam that will become a seed crystal. 1. Form a recrystallized region. A second recrystallized region is formed by scanning in the X direction while irradiating a second energy beam onto a part of the first recrystallized region and the semiconductor thin film adjacent to the region from the back surface of the substrate. The second beam has an intensity distribution or a beam width distribution that gradually increases along the Expanding. To further enlarge the recrystallized region, scanning is performed in the X direction with the n-th beam having the same intensity distribution or shape as the second beam. Although the first, second, and nth beams can be irradiated to different parts of the three semiconductor films at the same time, the temperature distribution can be made uniform by the metal film.

[Conventional technology]

Beam annealing including laser annealing is SO
(silicon on in5ulator) technology is about to be used in three-dimensional integrated circuits. As a beam annealing method, Nikkei Electronics 1985
(1) Changing the beam intensity (2) Changing the beam intensity by providing a reflective or absorbing film on the surface of the semiconductor film (3) Changing the way heat escapes There are ways to make a difference. An example of method +11 is shown in FIG. 2+al, which shows a cross section where the a-5i film 2 on the insulating substrate 1 is irradiated with the laser beam 10 to form the first recrystallized region 101. The first beam 1o is scanned in the X direction and has an intensity distribution (t·0) 10 in the X direction as shown in FIG.

Since the intensity (temperature) at the center of the beam is lower than that at the ends, recrystallization starts from the center and a single crystal region 102 is formed.
The ends become polycrystalline regions 103 and 104. Immediately after the beam irradiation, at 1=0, the temperature distribution becomes 10, which reflects the intensity distribution, but after the elapse of time, at t=tl, the temperature distribution becomes 1, which is below the melting point Lm, reflecting the distribution 10. FIG. 2 (in el, the second recrystallized region 201 is scanned by the second beam 20)
This is an example in which it is provided adjacent to 1. The second beam 20 has an intensity distribution 20 that gradually becomes stronger in the X direction as shown in FIG.
) Temperature distribution 200 (t
= tl), a large oak value occurs. Second recrystallization region 20
Although the single crystal region 202 in the first recrystallized region 101 is connected to the interface 120 with that 102 in the first recrystallized region 101 without defects, a grain boundary 121 is generated inside the single crystal region 202. This problem is particularly important for the first. Irradiation time interval L1 of second beam 10°20
This tends to occur when the time is short, less than a few seconds. That is, it becomes a problem during mass production.

[Problem that the invention seeks to solve]

The present invention has been made in order to reduce the influence of the temperature distribution of the beam annealing immediately before the above description. The purpose is to promote a beam annealing method that can mass-produce large-area recrystallized semiconductor thin films with good reproducibility.

[Means for solving problems]

In order to reduce the influence of the temperature distribution of the immediately preceding beam annealing, in the present invention, an insulating film, a gold film, and a metal film are sequentially deposited on the three semiconductor films. The energy beam is irradiated from the back side of the two insulating substrates. ! The J-body thin film is irradiated with a first energy beam while being scanned in the X direction to form a first recrystallized region that will become a seed crystal.

A second recrystallized region is formed by scanning in the X direction while irradiating a part of the first recrystallized region and the semiconductor thin film with the second energy beam. The second beam has an intensity distribution or a beam width distribution that gradually increases along the Expanding. To further enlarge the recrystallized region, scanning is performed in the X direction with the n-th beam having the same intensity distribution or shape as the second beam. The first, second, and n-th beams can be simultaneously irradiated onto different parts of the semiconductor thin film, thereby increasing mass productivity.

[Effect]

In the conventional method example shown in FIG. 2, heat radiation after beam annealing is performed on the substrate side. Generally, insulating substrates have poor thermal conductivity, so the temperature distribution during annealing tends to remain unchanged. In the present invention, heat is dissipated from the gold rA film and the substrate side. Moreover, because of the metal film, heat is radiated laterally, and the temperature distribution tends to be uniform. Therefore, the temperature rise of the semiconductor thin film during irradiation with the second beam tends to reflect the beam intensity distribution, and grain boundaries are less likely to occur.

〔Example〕

FIG. 1 shows the beam annealing process and temperature distribution according to the present invention. 1(a) is a cross section of a transparent insulating substrate 1 on which an a-5i film 2.5i02 film 3 and a metal film 4 are sequentially deposited. The first energy beam 10 is fixedly scanned in the x direction, and
The intensity distribution or shape is chosen so as to form a temperature distribution 10 (t=o) shown in FIG.

The a-5i film 2 melts first in the region above the melting point Tm.
This becomes a recrystallized region 101. The first beam IO is set such that the temperature at the center is lower than at the ends, and recrystallization starts from the center. As a result, the first recrystallized region 101 is divided into the first single crystal region 102 at the center and the polycrystalline region 103.1 at the end.
Consists of 04. When time t1 elapses after irradiation of the first beam 10, a-5
The i-film 2 has a gentle temperature distribution 11 (t-
tl). In the first (C), the second beam 2 at t=tl
2 shows a cross section in which a second recrystallized region 201 is formed by irradiating 0 from the surface of the substrate 1. The second beam 20 has an intensity distribution or shape that inherently provides the temperature distribution 20 (t=tl) shown in FIG.
Since there is an influence of the temperature distribution 11 (t=tl), the annealing is substantially performed with the added temperature distribution 200 (t=t1). Since the temperature distribution 11 is gentle, the synthetic temperature distribution 200 is also smooth, and the second recrystallized region 201 grows using the first single crystal region 102 as a seed, and the second single crystal region 202 without defects is formed at the interface 120.

As time further elapses and t=t2, the a-5i film 2 has a smooth temperature distribution 21 (t, t2). Figure 1te
1 shows a cross section in which a third recrystallized region 301 is formed using the third beam 30. The third beam 2o is heated so as to give the same original temperature distribution 30 (t=t2) as in the annealing by the second beam 2o.
The shape of the beam 30 is also selected to achieve a smooth composite temperature distribution 3
00 is obtained. A third single crystal region 302 with a defect-free interface 230 is obtained. Similarly, by scanning in the X direction with the n-th beam, a large-area single crystal thin film can be formed.

The transparent insulating substrate 1 used here is quartz, glass, sapphire, spinel, etc., and in the case of low melting point glass, etc.
It is desirable to coat the surface with an i02 film, a SiN film, or the like. The a-5t film 2 can be deposited by PCVD, sputtering, photo-CVD, etc., and is preferably thin from the viewpoint of heat capacity, and usually has a thickness of 300 nm.
Selected below 0A. When the a-5i film 2 contains hydrogen, etc., the temperature is 500 to 80% before depositing the next insulation film 3 and metal film 4.
Furnace annealing is performed at approximately 0°C or beam annealing is performed to an extent that does not melt. The insulating film 3 has a melting point higher than the melting point Tm of the semiconductor thin film 2, such as a 5i02 film or a SiN film. The thickness is selected from the viewpoint of heat conduction, and is 500 to 100 mm.
It is about OA. The metal 4 is made of a high melting point metal such as MO, W, or Ta, or a two-layer film of a high thermal conductivity metal such as AI, Au, Ni, or Cu, and is as thick as 5000A or more. Energy beams include Ar and CW.

A laser beam that passes through the substrate, such as He-Cd CW, Nd-YAG, or excimer laser beam, is used. 2nd, 3rd, nth
Beam 20, 30. , , , the intensity or the beam width in the X direction gradually increases in the first, second, n-1th single crystal regions 102, 202 . , , , is irradiated with small intensity or width to remelt it.

In the present invention, heat dissipation after beam annealing is very quick, so two lasers are provided for the first and second beams, and two beams can be scanned simultaneously. Immediately after the first beam scans, for example, an IC
Since the second beam can be irradiated with a delay of J11, the throughput of the device is high. This also applies to the second, third, and n-th beams. In addition to using multiple lasers, there is also a method that uses beam splitting. When annealing is performed by reciprocating the beam in the X direction, first, for example, the first, second, and third beams are scanned in the +X direction, then the substrate is moved in the X direction, and the second and third beams are used to scan the substrate in the -X direction. scan. Further, by moving the substrate in the X direction and scanning in the X direction with the second and third beams, a recrystallized semiconductor thin film with a large area can be obtained.

〔Effect of the invention〕

According to the present invention, heat dissipation after beam irradiation is performed quickly due to the metal film, and the temperature distribution of the semiconductor thin film becomes smooth.

The beam irradiation immediately after is affected by this temperature distribution.
Therefore, grain boundaries are less likely to occur within the recrystallized thin film. As a result, a recrystallized semiconductor thin film with a large area and few defects can be obtained with high throughput.

Although the recrystallization of the a-5i film has been mainly described above, the present invention can also be applied to polycrystalline Si and other semiconductor thin films. As a result, high-speed transistors can be highly integrated on a transparent insulating substrate, resulting in SOS (SILICON ON 5AP)
-P[I? An IC that applies four drops to E) can be made at low cost.

[Brief explanation of drawings]

Figure 1 shows a cross-sectional view of the process of beam annealing according to the present invention and the temperature distribution in the y-direction within the semiconductor thin film; Distribution is shown. 1...Substrate 2...a-5i film 3...5
102 film 4...Metal film lO...First beam 20...Second beam 30...Third beam 101...First recrystallization region 102...First single crystal 9■ region 103 , 104, 20.1, 30, 1... Polycrystal region 201... Second recrystallized region 202... Second single crystal region 301... Third recrystallized region 302... Third single crystal region Crystal region 120.230...Interface 121...Grain boundary or above Applicant: Seiko Electronic Industries Co., Ltd. Agent Patent attorney: Tsutomu Mogami (and 1 other person) 'Den\ (-'-・,・heel) Figure 1 1. Beam annealing method of the present invention); 7. Bu■20
1 Y position Y position Figure 2, conventional beam annealing method Ryj4Y position Yh2 position

Claims (4)

[Claims] (1) A first step of sequentially depositing an amorphous or polycrystalline semiconductor thin film, an insulating film, and a metal film on a transparent insulating substrate, and irradiating the semiconductor thin film from the back surface of the substrate with a first energy beam in the x direction. a second step of forming a first recrystallized region by scanning a part of the first recrystallized region from the back surface of the substrate;
A second layer is formed on the semiconductor thin film adjacent to the y-direction side along the direction.
In a beam annealing method for a semiconductor thin film comprising a third step of irradiating an energy beam and scanning in the x direction to form a second recrystallized region, the second beam has an intensity distribution that gradually increases along the y direction or has a beam width distribution,
A beam annealing method for a semiconductor thin film, characterized in that a portion of a first recrystallized region is irradiated with a portion having a small intensity or beam width. (2) Following the third step, an n-th (n is an integer of 3 or more) energy beam having the same intensity distribution or beam width distribution as the second beam is applied to the n-1 recrystallized region from the back surface of the substrate. and an (n+1)th step of forming an n-th recrystallized region by scanning in the x-direction while irradiating the semiconductor thin film adjacent to the region in the y-direction along the x-direction. A beam annealing method for a semiconductor thin film according to scope 1. (3) A beam annealing method for a semiconductor thin film according to claim 1 or 2, wherein the first and second beams are simultaneously irradiated onto different parts of the semiconductor thin film. (4) A beam annealing method for a semiconductor thin film according to any one of claims 1 to 3, characterized in that said second and n-th beams are simultaneously irradiated to different parts of said semiconductor thin film.