Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – On insulating substrate or layer
Reexamination Certificate
1998-07-24
2001-06-26
Chaudhuri, Olik (Department: 2823)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
On insulating substrate or layer
Reexamination Certificate
active
06251715
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin film transistor-liquid crystal display (hereinafter referred to as a TFT-LCD) and a manufacturing method of the same.
2. Description of the Related Art
A conventional TFT-LCD consists of a gate electrode, an insulating layer, a semiconductor layer, a source/drain electrode, a passivation layer, and a pixel electrode layer.
Amorphous silicon is generally used as the semiconductor layer. The amorphous silicon has a mobility in the range of 0.5-1.0 [cm
2
/Vsec]. However, the mobility of the amorphous silicon is too low to drive a TFT, since the mobility needed for driving a TFT is 50-150 [cm
2
/Vsec].
Therefore, a TFT using amorphous silicon must have a driving IC outside of a liquid crystal panel to drive the TFT. But using a driving IC is troublesome. Accordingly, it would be preferable for TFTs to use a semiconductor layer made from poly silicon, which has a high mobility of around 50-150[m
2
/Vsec].
A poly silicon TFT preferably has grains that are large. It is also desirable that the grains and the space between the grains do not have defects, and that the surface has minimal roughness.
In attempting to obtain these characteristics, fabrication sequences for semiconductor layer of a conventional poly silicon TFT-LCD will now be described.
FIGS. 1A-2E
show cross-sectional views of a fabrication sequence for a conventional poly silicon TFT-LCD.
FIG. 1A
illustrates a substrate
102
.
FIG. 1B
illustrates depositing an amorphous silicon
104
on the substrate
102
.
FIG. 1C
shows annealing the amorphous silicon with a temperature in the range of 500-700° C. to transform the amorphous silicon
104
to a poly silicon
106
having increased grain size.
FIG. 1D
illustrates patterning the poly silicon
106
to obtain a patterned layer
106
A.
Annealing of the patterned poly silicon
106
A is illustrated in
FIG. 1E
, with a temperature in the range of 800-1100° C. to obtain patterned poly silicon layer
106
B having improved crystallization characteristics.
FIGS. 2A-2F
show cross-sectional views of another fabrication sequence for a conventional poly silicon TFT-LCD.
FIG. 2A
illustrates a substrate
202
, on which there is deposited an amorphous silicon
204
, as shown in FIG.
2
B.
FIG. 2C
illustrates depositing a photoresist
205
, patterning the photoresist
205
, and implanting ions in the amorphous silicon
204
.
FIG. 2D
illustrates annealing the amorphous silicon
204
with a temperature in the range of 500-700° C. to transform the amorphous silicon
204
to a poly silicon
206
having increased grain size.
FIG. 2E
illustrates patterning the poly silicon
206
to obtain a patterned layer
206
A, which is then further annealed as illustrated in
FIG. 2F
with a temperature in the range of 800-1100° C. to obtain patterned poly silicon
206
B having improved crystallization characteristics.
FIGS. 3A-3D
show cross-sectional views of another fabrication sequence for a conventional poly silicon TFT-LCD.
FIG. 3A
illustrates a substrate
302
, on which there is deposited a poly silicon
306
, as shown in FIG.
3
B.
FIG. 3C
illustrates implanting ions in the poly silicon
306
and annealing the poly silicon
306
with a temperature in the range of 500-700° C.
FIG. 3D
illustrates patterning a poly silicon
306
to obtain a patterned layer
306
A.
The above-described conventional poly TFT-LCD is not perfectly crystallized, therefore, additional time is needed for heating and annealing.
SUMMARY OF THE INVENTION
The objective of the present invention is to provide a poly silicon TFT-LCD and a manufacturing method of the same for fully crystallizing an active portion of a semiconductor layer by positioning a seed in a desired position.
In order to achieve the above object, and others, the poly silicon TFT-LCD according to the present invention includes a seed layer pattern which is formed on the substrate.
A silicon layer which is formed by epitaxial growth on the seed layer pattern is fully crystallized due to the presence of the seed layer pattern, so that the crystallization growth pattern begins at the seed layer and occurs outward therefrom.
A method of the above described poly silicon TFT-LCD includes depositing a seed layer on a substrate and then forming a seed layer pattern by etching the seed layer. Thereafter, a silicon layer is deposited over the seed layer. Ions are then implanted in the silicon layer, which is thereafter annealed. Accordingly, a silicon layer having a large grain size is obtained.
In another embodiment, a trench formed in a substrate acts as a seed layer so that a silicon layer having a larger grain size is obtained. A method for manufacturing a poly silicon TFT-LCD according to this embodiment includes forming a trench by etching a substrate and depositing a silicon layer over the substrate and within the trench. Thereafter, annealing of the silicon layer is performed to obtain a larger grain size. The silicon layer is then patterned and etched to form a silicon layer pattern.
In still another embodiment, a method for manufacturing a poly silicon TFT-LCD according to the present invention deposits an amorphous silicon on a substrate. This amorphous silicon is transformed to a poly silicon layer using solid phase crystallization. A seed layer is formed by etching the poly silicon layer. Thereafter, a amorphous silicon is deposited on the poly silicon layer and the amorphous silicon is then transformed to an active poly silicon using solid phase crystallization.
In still another embodiment, a method for manufacturing a poly silicon TFT-LCD according to the present invention deposits a seed layer of amorphous silicon on a substrate and then an active amorphous silicon layer thereon. This amorphous silicon is transformed to a poly silicon layer using a laser to melt completely parts of the active layer which exist on region adjacent the seed layer to form a laser crystallized active region.
The seed layer pattern, in all of the above embodiments can be formed of a singular or multiple patterned portions that are preferably positioned in a location that corresponds with the position of the source and drain electrodes of the TFT-LCD that are part of the silicon layer disposed in order to maximize the grain size of the active portion of the TFT-LCD transistor.
REFERENCES:
patent: 4732659 (1988-03-01), Schachter et al.
patent: 5318919 (1994-06-01), Noguchi et al.
patent: 5389580 (1995-02-01), Miyasaka
patent: 5508216 (1996-04-01), Inoue
patent: 5531182 (1996-07-01), Yonehara
patent: 5637515 (1997-06-01), Takemura
patent: 5858820 (1999-01-01), Jung et al.
patent: 6069370 (2000-05-01), Hayama et al.
Hwang Chang-Won
Jin Yong-suk
Jung Byung-hoo
Lee Joo-hyung
Chaudhuri Olik
Coleman William David
Pillsbury & Winthrop LLP
Samsung Electronics Co,. Ltd.
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