Active solid-state devices (e.g. – transistors – solid-state diode – Non-single crystal – or recrystallized – semiconductor... – Amorphous semiconductor material
Reexamination Certificate
2000-01-05
2001-08-21
Abraham, Fetsum (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Non-single crystal, or recrystallized, semiconductor...
Amorphous semiconductor material
C257S072000, C257S347000, C257S351000, C257S357000, C257S350000
Reexamination Certificate
active
06278131
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device having a circuit comprising thin film transistor (hereinafter referred to as TFT). For example, it relates to structures of an electro-optical device which is typified of a liquid crystal display device or an EL display device and electric equipment which uses a semiconductor circuit and an electro-optical device or a semiconductor circuit of the present invention.
Note that through this specification, a semiconductor device indicates devices in general which may function by making use of semiconductor characteristics, and that electro-optical devices, semiconductor circuits, and electric equipments are all semiconductor devices.
2. Description of the Related Art
A thin film transistor (hereinafter referred to as TFT) can be formed on a transparent substrate, so that the development of applications to active matrix type liquid crystal displays (hereinafter referred to as AM-LCD) has been actively progressing. High mobility can be obtained in a TFT using a crystalline semiconductor film (typically polysilicon), so that it is possible to realize a high definition image display which integrates function circuits on the same substrate.
Basically in an AM-LCD, a pixel section which displays an image (also called a pixel matrix circuit), a gate driver circuit which drives TFT of each of the pixels arranged in the pixel section, and a source driver circuit, or a data driver circuit, which sends an image signal to each of the TFTs are formed on the same substrate.
In addition to the pixel section and driver circuits, in recent years a system-on-panel has been proposed, in which signal processing circuits such as a signal dividing circuit, a &ggr; compensation circuit, etc., are also formed on the same substrate.
However, it is difficult to satisfy all of the circuit specifications with TFTs having the same structure because the performance demanded by the circuits differs between the pixel section and the driver circuits. In other words, at present a TFT structure has not been established which will satisfy both a driver circuit, which places greater importance on high speed operation, and a pixel section, which places greater importance on high voltage resistance characteristics, at the same time.
The applicant of the present invention has already filed a constitution in which the gate insulating film thickness is made different for a TFT which structures a driver circuit (hereinafter referred to as driver TFT) and for a pixel TFT (see Japanese Patent Application Laid-Open No. Hei 10-056184 and the corresponding U.S. patent application Ser. No. 08/862,895). Specifically, the gate insulating film of the driver TFT is made thinner than the gate insulating film of the pixel TFT.
SUMMARY OF THE INVENTION
The present invention carries out a further improvement of a pixel section, based on the structure described in the above publications. Specifically, the present invention is to provide a structure for forming a storage capacitor which can secure a large capacity in a small area.
An object of the present invention is to provide an electro-optical device, typically an AM-LCD, which has high reliability, and which is formed by TFTs which are appropriately structured for the functions of each circuit of the electro-optical device. Still another object of the present invention is to increase the reliability of a semiconductor device (electric equipment) which has this type of electro-optical device as a display section.
According to an aspect of the structure of the invention disclosed in this specification, there is provided a semiconductor device having a driver circuit section and a pixel section on the same substrate, characterized in that:
a driver TFT of the driver circuit section, and a pixel TFT of the pixel section, each have a gate insulating film with a mutually differing film thickness; and
the film thickness of a dielectric of a storage capacitor formed in the pixel section is the same as the film thickness of the gate insulating film of the driver TFT.
Specifically, there is provided a semiconductor device having a driver circuit section and a pixel section on the same substrate, characterized in that:
the film thickness of a gate insulating film of a driver TFT of the driver circuit section is thinner than the film thickness of a gate insulating film of a pixel TFT of the pixel section; and
the film thickness of a dielectric of a storage capacitor formed in the pixel section is the same as the film thickness of the gate insulating film of the driver TFT.
In addition, another aspect of the structure of the present invention is characterized by comprising:
a first step of forming an amorphous semiconductor film on a substrate;
a second step of forming a crystalline semiconductor film, from the amorphous semiconductor film, by solid phase growth using an element selected from nickel, cobalt, palladium, germanium, platinum, iron, and copper;
a third step of patterning the crystalline semiconductor film, forming an active layer;
a fourth step of forming an insulating film on the surface of the active layer;
a fifth step of oxidizing the active layer by thermal oxidation process, after the fourth step;
a sixth step of doping a periodic table group
15
element or a periodic table group
13
element into the active layer, which has passed through the fifth step; and
a seventh step of performing heat treatment at a temperature of from 750 to 1150° C., after the sixth step.
In addition, according to another aspect of the structure of the present invention, there is provided a method of manufacturing a semiconductor device which includes a driver TFT and a pixel TFT on the same substrate, characterized by comprising:
a first step of forming an amorphous semiconductor film on a substrate;
a second step of forming a crystalline semiconductor film, from the amorphous semiconductor film, by solid phase growth using an element selected from nickel, cobalt, palladium, germanium, platinum, iron, and copper;
a third step of patterning the crystalline semiconductor film, forming an active layer of the driver TFT and an active layer of the pixel TFT;
a fourth step of forming a first insulating film on the active layer of the driver TFT and on the active layer of the pixel TFT;
a fifth step of etching the first insulating film, exposing the entire active layer of the driver TFT and a portion of the active layer of the pixel TFT;
a sixth step of forming a second insulating film, on the surface of the active layer exposed by the fifth step, by thermal oxidation process;
a seventh step of forming a wiring on the first insulating film and the second insulating film;
an eighth step of doping a periodic table group
15
element or a periodic table group
13
element into the active layer using the wirings as a mask; and
a ninth step of performing heat treatment at a temperature of from 750 to 1150° C., after the eighth step.
In addition, another aspect of the structure of the present invention is characterized by comprising:
a first step of forming an amorphous semiconductor film on a substrate;
a second step of forming a crystalline semiconductor film, from the amorphous semiconductor film, by solid phase growth using an element selected from nickel, cobalt, palladium, germanium, platinum, iron, and copper;
a third step of doping a periodic table group
15
element into the crystalline semiconductor film;
a fourth step of performing heat treatment onto the crystalline semiconductor film at between 500 and 650° C., after the third step;
a fifth step of patterning the crystalline semiconductor film, which has passed through the fourth step, forming an active layer;
a sixth step of forming an insulating film on the surface of the active layer;
a seventh step of oxidizing the active layer by thermal oxidation process, after the sixth step;
an eighth step of doping a periodic table group
15
element or a periodic table group
13
element into the active layer, after passing through the seventh ste
Fukunaga Takeshi
Koyama Jun
Shibata Hiroshi
Yamazaki Shunpei
Abraham Fetsum
Cook Alex McFarron Manzo Cummings & Mehler, Ltd.
Semiconductor Energy Laboratory Co,. Ltd.
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