JPS6046019A - Noncrystal substrate with single crystal silicon thin film and its manufacture - Google Patents

Abstract

PURPOSE:To enable application to improvement of performance of a switching element for picture element control, the transmission type and the larger picture of a display or to a three-dimensional circuit element related to a display of liquid crystal, EL, fluorescence, etc. by having a single crystal silicon thin film of more than a specific value width. CONSTITUTION:A noncrystal substrate which has a single crystal silicon thin film of more than 20mum width is used. Minute silicon nuclear crystal particles are also formed on a noncrystal film 2 such as silicon oxide or silicon nitride or on a noncrystal solid such as glass which is formed on a glass or other solid 1 and around the particles, a polycrystalline silicon thin film 3 or a noncrystal silicon thin film 7 consisting of more minute particles is formed and the film absorb minute silicon particles from around due to thermal annealing causing crystal growth of nuclear crystal particles to a monocrystal 4 of large area whereby the noncrystal substrate with the single crystal silicon thin film is manufactured.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention provides a single crystal silicon thin film that can be used for switching elements and three-dimensional circuit elements for controlling picture elements in display panels such as liquid crystal, EL, and fluorescent. Related to an amorphous substrate and its manufacturing method 0 Structure of conventional examples and problems thereof In recent years, display devices have become increasingly important in the information society, and are used in communication, information processing, Widely used in fields such as home appliances. Among these, there are great expectations for LCD displays, especially LCD TVs, because they can be driven at low voltages and have the potential to become small TVs or wall-mounted TVs, but it is important to improve contrast and response speed. has become a major technical challenge. As a countermeasure to this problem, active matrix displays have been developed in which each picture element incorporates a switching element and a storage capacitor, and efforts have been made to improve the duty ratio. However, in order to increase the size of LCD televisions, the development of a substrate equipped with a large number of high-performance picture element control elements is still an important technical issue. Types of switching elements for pixel control include MOS type, which uses a single crystal silicon wafer, and TF type, which uses a glass substrate.
There are the T type and the SOS type, in which a sapphire single crystal is used as the display substrate and a silicon single crystal is attached thereon.

However, each has its own problems, and efforts are being made to improve them. For example, in a MOS type that uses a silicon wafer, the switching elements of each picture element have excellent characteristics, but because the silicon wafer is used as a substrate, it is limited to a reflective type and cannot be used as a transmissive type.
The drawback is that the screen cannot be made larger because there is a limit to the size of the wafer. In the SOS type, a sapphire single crystal is used for the substrate, and single crystal silicon is epitaxially grown on it, and the switching element is made using this, so a transmission type is possible, and the characteristics of the switching element are also good. , sapphire single crystal is extremely expensive;
Also, like silicon wafers, there is a problem that large area products cannot be manufactured. In addition, systems using glass substrates are currently being actively studied because they allow for larger screens, transmission types, and lower costs. However, how to make high-performance switching elements on glass substrates has become an important technical issue. Therefore, as a semiconductor, CdS
E, Te, amorphous silicon, polycrystalline silicon, etc. have been studied, and now the amorphous silicon method and the polycrystalline silicon method are becoming mainstream. However, in polycrystalline silicon, the mobility of electrons is low due to the presence of many grain boundaries, and if the mobility is increased by increasing the size of the crystal grains and reducing the number of grain boundaries, variations in characteristics between each switching element will occur. There are problems that arise. Furthermore, although the device characteristics of amorphous silicon are more uniform than those of polycrystalline silicon, there are problems in that the mobility of electrons is extremely low and the switching speed is low. Therefore, it is most desirable if a single crystal silicon thin film can be formed on a transparent glass plate.

Conventionally, attempts have been made to form silicon single crystals with an area large enough to form switching elements on glass substrates using methods such as laser annealing and electron beam annealing. μm, length 20μ
The result is a polycrystalline thin film consisting of large, elongated silicon crystal grains of about 1.0 m in diameter, and a single-crystalline silicon thin film with an area capable of forming a switching element has not been obtained. Recently, a long depression of more than ten micrometers is formed in an amorphous insulating film such as silicon oxide or silicon nitride, and the polycrystalline silicon film formed there is laser annealed in the length direction. With a method of
It is now possible to obtain single crystal silicon of about m.

However, a wide single crystal film has not been obtained. In addition, with the aim of realizing three-dimensional circuit elements, attempts have been made to attach an amorphous insulating film such as silicon oxide or silicon nitride to a single crystal silicon wafer, and then form single crystal silicon on top of the amorphous insulating film.

As a method for this purpose, a method has been attempted in which polycrystalline silicon or amorphous silicon thin film formed on an amorphous insulating film is made into a single crystal by a method such as laser annealing or electron beam annealing. At present, a hole is made in the amorphous insulating film and a part of polycrystalline silicon or amorphous silicon is brought into contact with the single crystal silicon of the substrate, and a single crystal is grown using the single crystal silicon of the substrate as a seed. There is a method of forming a long depression of more than 10 micrometers on an amorphous insulating film, and then converting the polycrystalline silicon or amorphous silicon formed there into a single crystal by laser annealing or electron beam annealing. is being attempted. As a result, an elongated strip-shaped single crystal with a width of about 10 μm and a length of several hundred μm has been obtained, but a single crystal thin film with l], which is effective for device fabrication, has not been fabricated.0 Purpose of the Invention The present invention relates to displays such as liquid crystal, EL, and fluorescent, and is concerned with improving the performance of switching elements for pixel control, mounting peripheral electronic circuits on substrates, and making transmissive displays and larger screens. Another object of the present invention is to provide an amorphous substrate provided with a single-crystal silicon thin film, which can be applied to three-dimensional circuit elements, and a method for manufacturing the same.

Structure of the Invention In the present invention, the amorphous substrate has a single crystal silicon thin film with a diameter of 20 μm or more. Furthermore, the present invention provides a method for forming a micro-area of polycrystalline silicon or amorphous silicon on an amorphous film such as silicon oxide or silicon nitride formed on a glass plate or other solid, or on an amorphous solid such as glass. The thin film is single-crystalized by an annealing method such as laser annealing to form minute single-crystal silicon particles (nucleus crystal particles), and then polycrystalline silicon or amorphous silicon consisting of finer silicon particles is formed around the crystal particles. It is characterized by forming a silicon thin film and thermally annealing it in a solid state to absorb surrounding fine silicon particles and grow the core crystal particles to form a large-area single crystal. .

Description of Examples (Example 1) As shown in FIG. 1(-), a silicon oxide film 2 is formed on a quartz glass substrate 1 by a sputtering method, and a polycrystalline silicon film with a thickness of about 1 μm is further formed on the silicon oxide film 2. The thin film 3 was formed using a sputtering method.

Next, as shown in FIG.
1. After forming a rectangular polycrystalline silicon thin film 3' of 8 μm x 100 μm in the form of an island using the lithography method, the periphery of the island-like polycrystalline silicon thin film 2 was filled with a silicon oxide thin film 2 using the sputtering method. In this state, a CW argon laser was scanned in the length direction of the island to perform melting annealing. Except for the vicinity of the starting point and the vicinity of the other end, the entire grain became a single crystal grain 4 without grain boundaries. Next, as shown in FIG. 1 (Φ), the peripheral part of the single crystal silicon and the silicon oxide film were removed by photolithography to form a rectangular single crystal silicon island of 5 μth x so μm. Filled with silicon oxide 2 by sputtering, and again by photolithography, a rectangular hole 5 of 50 μm x 70 μm containing single crystal silicon was formed as shown in Fig. 1(e).
Amorphous silicon 7 was formed in the hole 5 with the photoresist still attached. Excess amorphous silicon 1 on the photoresist 6 was removed by lift-off to obtain a sample having the structure shown in FIG. 1(f) t(q). FIG. 1(q) is a plan view of FIG. 1(f) viewed from direction A. When this was brought into the solid state and annealed, the entire hollow island became a single crystal (the first
Figure (h)).

(Example 2) As shown in FIG. 2(-), a silicon nitride thin film 8 having a thickness of approximately 1 μm was formed on a quartz glass substrate 1 by sputtering. In this film, as shown in Fig. 2Bb),
A rectangular hole of 8 μm x 100 μm was made by photolithography, and an amorphous silicon film was formed as shown in FIG. 1(C) with photoresist 6 attached as shown in the same figure. After removing the amorphous silicon other than the hole part along with the photoresist, a silicon nitride film 8 was formed by sputtering to form a sample with a structure in which the amorphous silicon islands 7' were embedded as shown in FIG. 1(d). Obtained. In this state, CW
When an argon laser was scanned in the length direction of the silicon island to perform melt annealing, the entire island became a single crystal except for the area near the tip of the silicon island, which is the starting point of laser annealing, and the area near the other end. Figure 1 (e)).

Hereinafter, in the same process as in the example, 60 μm × 70 μm O
A rectangular single crystal silicon thin film was obtained.

(Example 3) As shown in FIG. 3(a), a silicon oxide film 2 is formed on a single crystal silicon 9 by sputtering, and then, as shown in FIG. 3(b), a silicon oxide film 2 of 8 μm is formed by photolithography.
A hole of m×100 μm was made. Next, Figure 3 (p)
As shown, an amorphous silicon film 7 was formed with the photoresist 6 attached. Thereafter, after removing most of the amorphous silicon together with the photoresist 6, a silicon oxide film 2 was formed by sputtering, and the amorphous silicon islands 7' were embedded as shown in FIG. 3(d). A sample of the structure was obtained. In this state, when the CW argon laser was scanned in the length direction of the amorphous silicon island to melt and anneal it, the entire silicon island was melted, except for the tip of the silicon island, which is the starting point of laser annealing, and the vicinity of the other end. It became a single crystal. Hereinafter, by the same process as Examples 1 and 2, 60 μm × 7
A 0μm rectangular single-crystalline silicon thin film is connected to single-crystalline silicon through an amorphous silicon film.

formed on a wafer.

In the above example, an amorphous silicon oxide or silicon nitride film is applied to the surface of amorphous quartz glass, but other types of glass or other amorphous solids may be used as long as they are heat resistant. But it's okay. In the case of a dense amorphous solid, a single crystal silicon film can be formed without forming an amorphous film.

Furthermore, as shown in the example, in the case of a crystalline solid such as a single crystal silicon wafer, it is necessary to attach an amorphous film to the surface. A single crystal silicon film can also be formed via an amorphous film.

In the example, after the island-shaped polycrystalline or amorphous silicon is single-crystalized by melting laser annealing, the peripheral part is removed by photolithography, which removes the slightly disordered crystal orientation in the peripheral part. This is to obtain high quality core crystal particles. This is not necessary if a perfect single crystal can be obtained by melting laser annealing. In addition, in the examples, laser annealing is used to grow the core crystal grains, but in this case, since crystal growth is performed by annealing in the same phase state, other annealing methods, such as simple laser annealing, are used. Methods such as heating can also be applied. Further, by using the manufacturing method of the present invention, a single crystal silicon thin film with an even larger area can be created by repeating the same process.

In the embodiment, a sputtering method is used as a thin film forming method, but other thin film forming methods such as low pressure CVD, ion beam evaporation, MBE, etc. can also be used.

Effect of the invention According to the present invention, the following effects can be expected.

That is, silicon single crystal thin films having a size sufficient to form switching elements for controlling picture elements of displays using liquid crystal, EL, fluorescent, etc. can be formed by regularly arranging them on a glass substrate. Since the material is silicon, switching transistors can be easily formed in these island-like portions using known silicon processes. Furthermore, since it is made of single-crystal silicon, it can be expected to have much better performance than polycrystalline silicon thin films or amorphous silicon thin films, and peripheral circuits for display driving can also be fabricated on the same glass substrate. Furthermore, since it is a glass substrate, it is possible to make the panel larger and to make it a transmissive type, and it can be used for manufacturing large-screen liquid crystal televisions. Furthermore, since a single crystal silicon thin film can be formed on single crystal silicon via an amorphous insulating film, it is promising for three-dimensional circuit elements. Furthermore, the method of the present invention can be applied not only to the formation of single-crystal silicon thin films but also to the production of other materials, such as germanium single-crystal thin films. .

[Brief explanation of drawings]

Figures 1 (a) to (h), Figures 2 (a) to (e), and Figures 3 (a) to (d) show single crystal silicon thin films on amorphous substrates in embodiments of the present invention. It is a diagram showing the manufacturing process of. 1...1 quartz glass, 2...amorphous silicon oxide, 3 and 3'...polycrystalline silicon, 4...monocrystalline silicon, 7 ...Amorphous silicon, 7...Amorphous silicon, 8...
...Amorphous silicon nitride, 9...Single crystal silicon wafer. Name of agent: Patent attorney Toshio Nakao and 1 other person13
S2 figure 3 figure Q

Claims (3)

[Claims] (1) An amorphous substrate provided with a single crystal silicon thin film having a width of 20 μm or more. (2) Fine silicon core crystal particles are formed on an amorphous film such as silicon oxide or silicon nitride formed on glass or other solid material, or on an amorphous solid such as glass, and the particles are Forming a polycrystalline silicon thin film or amorphous silicon thin film consisting of finer particles around the periphery,
By thermally annealing this, the surrounding fine silicon particles are absorbed and the crystal growth of the core crystal particles occurs, resulting in a large-area single crystal. A method for manufacturing quality substrates. (3) Glass film is an amorphous insulating film such as silicon oxide or silicon nitride formed on an amorphous film such as silicon oxide or silicon nitride formed on another solid, or on an amorphous solid such as glass. forming micro-indentations,
A thin film of polycrystalline silicon or amorphous silicon is formed therein, and this is annealed using a method such as laser annealing to form minute nuclear crystal grains, and then polycrystalline silicon is formed around the core crystal grains. It is characterized by forming a silicon thin film or an amorphous silicon thin film, and then thermally annealing it to absorb surrounding fine silicon particles and grow the core crystal grains to form a large-area single crystal. A method for manufacturing an amorphous substrate provided with a single-crystal silicon thin film according to claim 2.