Semiconductor device manufacturing: process – Bonding of plural semiconductor substrates – Subsequent separation into plural bodies
Reexamination Certificate
2000-02-14
2002-04-23
Bowers, Charles (Department: 2813)
Semiconductor device manufacturing: process
Bonding of plural semiconductor substrates
Subsequent separation into plural bodies
C438S034000
Reexamination Certificate
active
06376333
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a technique by which a display panel which is flexible (having a flexibility) is provided, and more particularly to a technique by which a flexible active matrix liquid-crystal display unit is provided.
2. Description of the Related Art
There has been known a liquid-crystal display unit as a display unit which is small-sized, light in weight and of the thin type. This has a structure in which liquid crystal is interposed between a pair of translucent substrates which are bonded to each other at intervals of several &mgr;m and held in this state as the structure of a display panel. In the operation of the display unit, an electric field is applied to liquid crystal in a predetermined region so as to change its optical characteristics, whereby the presence/absence of a light transmitted through a panel and the amount of transmitted light are controlled.
As a technique by which the display characteristics of this liquid-crystal display unit is further enhanced, there has been known the active matrix display panel. This is to arrange switching thin-film transistors (in general, an amorphous silicon thin film is used) in the respective pixels disposed in the form of a matrix, and to control charges that takes in or out of the respective pixels by the thin-film transistors.
In order to improve the characteristics of the active matrix liquid-crystal display device, it is necessary to improve the characteristics of the thin-film transistor as used. However, under the existing circumstance, it is difficult to improve such characteristics in view of the relationship of the substrate as used.
What is required for the substrate used in the liquid-crystal display panel is such an optical characteristic that the substrate transmits a visible light. Substrates having such an optical characteristic are of a variety of resin substrates, a glass substrate, a quartz substrate, etc. Of them, the resin substrate is low in a heat-resistance, and therefore it is hard to manufacture the thin-film transistor on its surface. Also, the quartz substrate can withstand a high temperature of 1000° C. or more, however, it is expensive and causes an economical problem when the display unit is enlarged. For that reason, the glass substrate is generally used.
In order to improve the characteristics of the thin-film transistor, a silicon semiconductor thin film having a crystalline property need be used for the thin-film semiconductor that forms the thin-film transistor. However, in order to form the crystalline silicon thin film, a sample must be exposed to a high-temperature atmosphere, and in the case of using the glass substrate, there arises such a problem that the substrate is warped or deformed. In particular, when making the substrate large in area, that problem becomes remarkable.
As a technique by which a liquid-crystal display panel that solves such a problem and has a high display characteristic is obtained, there has been known a technique disclosed in Japanese Patent Unexamined Publication No. Hei 6-504139. This technique is that a thin-film transistor is manufactured by using a monocrystal silicon thin film formed through the SOI technique, etc., that thin-film transistor is peeled off from the substrate for an epitaxial growth, and the thin-film transistor is bonded to an arbitrary substrate having an optical characteristic as required, to thereby obtain a panel constituting a liquid-crystal display unit.
In the case of using this technique, since the monocrystal silicon thin film formed using a known SOI technique can be used, a thin-film transistor having a high characteristic can be obtained. Also, a substrate having a curved surface can be used.
In the technique disclosed in Japanese Patent Unexamined Publication No. Hei 6-504139, a thin-film transistor is manufactured using the SOI technique. However, in the SOI technique under the existing circumstance, it is difficult to form a monocrystal thin film in a large area of 10 inch diagonal or more.
For example, under the existing circumstance, the maximum monocrystal wafer is of 16 inches in size. In this case, the maximum square panel as obtained is of 16×(½)
−2
≈11 inch diagonal.
On the other hand, it is expected that the liquid-crystal display panel as required is of 20 or 30 inches or more in the diagonal dimension in the future. It is impossible to constitute such a large-sized liquid-crystal display panel through the method using the known SOI technique.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above, and an object of the present invention is to provide a technique by which a thin-film transistor having a high characteristic over a large area is manufactured.
Another object of the present invention is to provide a technique by which a display panel is obtained using that technique.
Still another object of the present invention is to provide a thin-film transistor and a display panel which are manufactured using the above-mentioned techniques.
In order to solve the above-mentioned problems, one aspect of the present invention has been achieved by the provision of a method of manufacturing a semiconductor device, comprising the steps of:
forming a first insulating film on a first substrate;
forming a second insulating film on the first insulating film;
forming an amorphous silicon film on said second insulating film;
holding a metal element that promotes the crystallization of silicon in contact with a surface of said amorphous silicon film;
crystallizing said amorphous silicon film through a heat treatment to obtain a crystalline silicon film;
forming a thin-film transistor using said crystalline silicon film;
forming a sealing layer that seals said thin-film transistor;
bonding a second substrate having a translucent property to said sealing layer; and
removing said first insulating film to peel off said first substrate.
A specified example of the above-mentioned structure is shown in
FIGS. 1
to
3
. First, in
FIG. 1
, a first insulating film (silicon oxide film)
102
that functions as a peeling layer is formed on a glass substrate
101
which forms a first substrate. Then, a silicon oxide film
103
is formed as a second insulating film. The silicon oxide films
102
and
103
are manufactured by different methods, respectively, and the first silicon oxide film
102
is made of a material which is readily removed by etching at a poststage.
Subsequently, an amorphous silicon film
104
is formed on a second insulating film
103
. Then, a solvent containing a metal element that promotes the crystallization of silicon therein is coated on the amorphous silicon film
104
, to thereby form a water film
105
, and a spin dry process is conducted using a spinner
106
into a state in which the metal element is brought in contact with the surface of the amorphous silicon film
104
.
Thereafter, a crystal silicon film
107
is obtained by conducting a heat treatment, and the crystalline silicon film
107
is formed into an active layer
108
, to thereby form a thin-film transistor as shown in
FIGS. 2A and 2B
. After the formation of the thin-film transistor, a layer
119
for sealing the thin-film transistor is formed. Then, a flexible translucent substrate
120
is bonded onto the layer
119
. Thereafter, the silicon oxide film which is of the first insulating film
102
forming a peeling layer is removed by conducting an etching process so that the glass substrate
101
is peeled off from the thin-film transistor.
Another aspect of the present invention has been achieved by the provision of a method of manufacturing a semiconductor device, which comprises the steps of:
forming a first insulating film on a first substrate having a groove formed in a surface thereof;
forming a second insulating film on said first insulating film;
forming an amorphous silicon film on said second insulating film;
holding a metal element that promotes the crystallization of silicon in contact with a surface of said amo
Arai Yasuyuki
Teramoto Satoshi
Yamazaki Shunpei
Bowers Charles
Fish & Richardson PC
Pert Evan
Semiconductor Energy Laboratory Co,. Ltd.
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