JPS6237922A - Semiconductor substrate - Google Patents

Abstract

PURPOSE:To control a temperature distribution with high accuracy, by forming a metal thin film on an insulative substrate, forming an insulating film thereon, forming a semiconductor film which is melted and solidified thereon, while extending the selective band of a heating source. CONSTITUTION:A metal thin film 11 is formed on an insulative substrate 10, and an insulating film 12 is formed on the metal thin film 11. Moreover, a semiconductor film 13 which is melted and solidified is formed on an insulative film 2. Then the thermal rays are absorbed not only by the semiconductor film 13 but also by the metal thin film 11, so that the selection range of laser ray wavelength is extended. Thereby, a temperature distribution is controlled with high accuracy and good reproducibility.

Description

Detailed Description of the Invention Industrial Application Field 2 =-i The present invention relates to a semiconductor substrate that provides a high-performance thin film transistor formed on an insulating substrate. It can be applied to active devices for other purposes.

Conventional technology The technology of annealing polycrystalline Si or amorphous Si grown on a quartz substrate with a laser beam, an electron beam, or a hot wire using a heater to form a single crystal reduces parasitic capacitance because it is formed on an insulating substrate. It has the characteristics that it is possible to obtain a high-speed transistor. Furthermore, since it is a transparent substrate, it is considered to be a promising matrix active element for display elements. On the other hand, in order to form a single crystal by annealing, control of temperature distribution is important.

In particular, in order to obtain a large-area single crystal thin film with little dalein,
In order to reduce the number of crystal nuclei during melting and solidification, it is necessary to increase the temperature distribution within the thin film surface at the periphery. An example is shown in FIG. 1o is an insulating substrate, 13 is a semiconductor film, and 14 is a protective film that prevents the semiconductor film from being deformed and scattered when it is melted and solidified.

20.21 can control the temperature distribution during melting and solidification by irradiating the peripheral area with laser light. However, this method requires two laser light sources and is expensive, and in order to obtain a single crystal thin film with few grains, it is necessary to precisely control the position of the single crystal thin film, which has disadvantages in terms of reproducibility. Figure 6 shows another conventional example, where 23 is a uniform laser beam, 24
26 is an anti-reflection film against laser light. With this configuration, the temperature distribution of the semiconductor film 13 has the advantages that the temperature becomes high because more laser light is absorbed in the periphery, and the antireflection films 24 and 25 can be formed with high precision, resulting in good reproducibility. have. However, in such a configuration, the wavelength of the laser light source 230 needs to have a sufficient absorption coefficient in the semiconductor film 13, which limits the selection of lasers and makes it difficult to obtain an optimal temperature distribution for single crystallization. This involves complications such as the need to optically determine the thickness of the antireflection films 24 and 25.

Problems to be Solved by the Invention As described above, with conventional semiconductor substrates, in order to improve the crystallinity of the semiconductor film, the equipment is expensive, the reproducibility is poor, and the selection of laser light is limited. It had the following drawbacks.

The present invention has been made in view of these points, and aims to provide a semiconductor substrate that can be supplied in large quantities at low cost by controlling temperature distribution with a simple configuration and providing versatility in heating sources. .

Means for Solving the Problems In order to solve the above problems, the present invention forms a metal thin film on an insulating substrate, forms an insulating film on it, and further forms a semiconductor film that is melted and solidified on top of it. It consists of a configuration.

Effects The present invention has the above-mentioned configuration, which expands the selection range of heating sources, so temperature distribution can be controlled with high precision and good reproducibility.Since there is a metal conductor on the bottom surface of the semiconductor film, it is possible to reduce substrate bias when transistors etc. are completely formed on the semiconductor film. Various positive effects are expected, such as the ability to improve mobility.

5 Page Embodiment FIG. 1 shows a semiconductor substrate which is the basic structure of the present invention. 1o is an insulating substrate, 5in2゜Al2O3,
Any material may be used as long as it is made of AeN, BNSIC, or a mixture thereof, and does not change shape, peel, or crack when the semiconductor film 13 is heated by the hot wire 16. 11 is a metal thin film made of high melting point materials such as Mo and Ta.
, W, and their silicide compounds are most suitable; however, any material having a higher melting point than the semiconductor film 13 may satisfy the requirements of the present invention. 12 is a first insulating film TE5in2.
It is made of Si3N4°Al2O3, etc., and has the function of preventing mutual diffusion between the semiconductor film 13 and the metal thin film at high temperatures. The semiconductor film 13 is Si, Go GaAs, GaP.
, lCdTa.

There are Cd5a and their mixed crystal materials, but sl.

Ge and mixed crystal materials thereof are particularly suitable because they have a low vapor pressure when heated and can be easily formed into single crystals. 14 is a protective film which has the function of preventing the semiconductor film 13 from changing its shape or scattering when heated, and 5102 and 1203 are suitable. 16.16 are both ray 6...-noza light or heat ray. In the present invention, these thermal rays are absorbed not only by the semiconductor film 13 but also by the metal thin film 11, so that the selectivity of the wavelength of the laser beam is expanded. For example, CO
Conventionally, the oscillation wavelength of 2 lasers, etc. is 10.2 μm.
However, in the present invention, it can be used because it is absorbed by the metal thin film 11, as it is not absorbed by a semiconductor film such as Si or Ge. It is also possible to improve the crystallinity of the semiconductor film 13 via the first insulating film 12 by heating the metal thin film 11 as shown at 16 in FIG.

The manufacturing method of the present invention shown in FIG. 1 will be described.

For example, fused quartz made of SiO2 is used as the insulating substrate 1o. Since the metal thin film 11 is a high melting point material, Mo
, Ta, W or their silicide compounds by the sputtering method.
Formed to a film thickness of m. The thickness of the metal thin film 11 is 0.05μ
Below m, the absorption coefficient of laser light or heat rays deteriorates. Moreover, if the film thickness is thicker than 1.0 μm7·-1, cracks or peeling will easily occur when the semiconductor film 13 is melted and solidified due to the difference in thermal expansion coefficient. The first insulating film 12 is made of 5i02.5iNz by a chemical vapor deposition method or a sputter-linda method.

Al2O2 etc. are formed. For example, when forming the S1 thin film, the semiconductor film 13 is formed by decomposing 5IH4 using a chemical vapor phase method or a plasma chemical vapor phase method.

Other methods include the electron beam evaporation method using Si as an evaporation source, and the snot-driving method using Si as a target. As long as the film thickness is within the range where cracks do not occur during melting and solidification (0.01 to 1.0
μm is suitable.

The protective film 14 is made of 5102 wo by chemical vapor deposition.
．． What is necessary is just to form 2-1.0/im. When the semiconductor substrate thus formed is irradiated with a laser beam or a hot ray 16 from a heater, at least the metal thin film 11
is heated, and the semiconductor film 13 is melted at a certain amount of heat or more. By removing the laser beam or the heat rays 15, 16i, the semiconductor film 13 is recrystallized, and its crystallinity is improved compared to when it was formed. Furthermore, if the temperature distribution is optimized, even a single crystal thin film can be obtained. This semiconductor film 13 with improved crystallinity has a high mobility of 100 to 450 i/v@Sec, and can be used as a substrate of a high-performance transistor. 'T! In this structure, since the heat absorbing material is the metal film 11, an inexpensive laser light source such as a C02 laser can be used as the laser light source, so it has great industrial significance. Furthermore, it is possible to apply an electric field to the metal thin film 11 when a transistor is formed on the semiconductor film 13, and an improvement in mobility can be expected.

FIG. 2 shows another embodiment of the present invention, in which an inexpensive glass substrate is used as the insulating substrate 10. The softening point of glass substrates varies depending on the material, but is generally between 450 and 80.
0''C is lower than the melting point of the semiconductor film 13, so a second insulating film 17 is required to moderate the temperature.A film such as 5in2.A/!206 is suitable for the second insulating film.
The temperature distribution control is facilitated by forming the insulating film 17 so as to be thicker than the first insulating film 12.

FIG. 3 shows another embodiment of the present invention in which the metal thin film 11 is patterned to give the semiconductor film 13 a temperature distribution during melting and solidification. Since the heat absorption source is the metal thin film 11, the temperature at the periphery of the semiconductor film 13 rises, and melting and solidification occurs from the center.

Therefore, with this configuration, it is easy to obtain a single crystal film as shown in the conventional example.

Effects of the Invention As described above, according to the present invention, it is possible to provide a semiconductor substrate on which high-performance transistors can be manufactured because the temperature distribution can be controlled with high precision and good reproducibility with a simple structure. In addition, it has effects such as expanding the selection range of heating sources and providing a semiconductor substrate that can produce a substrate bias effect, and is extremely effective as a semiconductor substrate for high-speed image scanners and active elements for displays.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a semiconductor substrate according to an embodiment of the present invention;
Fig. 2 is a sectional view of another embodiment of the present invention using glass as the insulating substrate, and Fig. 3 is a cross-sectional view of another embodiment of the present invention in which a pattern is formed on a metal thin film to control temperature distribution. Figure 4 is a cross-sectional view of a conventional example in which temperature distribution is controlled using two laser beams, and Figure 6 is a cross-sectional view of a conventional example in which temperature distribution is controlled using an anti-reflection film. be. 1o...Insulating substrate, 11...Metal thin film, 12...First insulating film, 13...Semiconductor film, 14... Protective film, 15.16...
. . . Laser light or heat ray, 17 . . . Second insulating film. Name of agent: Patent attorney Toshio Nakao and 1 other person12
-11 ya I'T, ma 1 phantom 1 f,) - 11 and a half +hg 14--1f January change 15.1 stitches - Shi-pu) Irin□ Figure 5

Claims (4)

[Claims] (1) A metal thin film formed on an insulating substrate, a first insulating film formed to cover the metal thin film, and a semiconductor film melted and solidified on the insulating film to improve crystallinity. A semiconductor substrate characterized by: (2) The semiconductor substrate according to claim 1, wherein the metal thin film is made of Mo, Ta, W, and silicide compounds thereof. (3) The semiconductor substrate according to claim 1, wherein another insulating film is formed between the insulating substrate and the metal thin film. (4) Claim 1, characterized in that the semiconductor film is made of Si, Ge, or a mixed crystal thereof.
Semiconductor substrate described in Section 1.