Method of fabricating a complementary metal-oxide...

Details Method of fabricating a complementary metal-oxide... Method of fabricating a complementary metal-oxide...

1998-08-19

2001-06-05

Wilczewski, Mary (Department: 2822)

Semiconductor device manufacturing: process

Making device or circuit responsive to nonelectrical signal

Responsive to electromagnetic radiation

C438S069000, C438S199000

Reexamination Certificate

active

06242277

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Taiwan application serial no. 7109135, filed Jun. 9, 1998, the full disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method of fabricating a complementary metal-oxide-semiconductor (CMOS) sensor device, and more particularly, to a method of fabricating microlens on a color filter.
2. Description of Related Art
Conventionally, for a PC camera and a digital camera, CMOS sensors are frequently used. A typical CMOS sensor diode includes a sensor layer on the substrate. The sensor layer has different sensor areas to detect different color light. On the sensor layer, there is a passivation and there is a color filer on the passivation. Furthermore, a color filter is formed on the passivation. The incident light usual has different color and incident angles. As the incident light penetrates through the color filter, it is divided into three color light, such as red light, green light or blue light and then absorbed and sensed by the corresponding sensor area.
FIG. 1A
to
FIG. 1F
illustrates the process flow of fabricating a conventional CMOS sensor device. First, referring to
FIG. 1A
, on a substrate
100
, a passivation layer
102
is formed. A color filter
108
, including red filter
108
a
, green filter
108
b
and blue filter
108
c
, is formed on the passivation layer
102
. The color filter
108
is made from acrylic material. Next, a planarized layer
103
is formed over the passivation layer
102
and the color filter
108
. An opening
104
and an opening
106
are defined on the planarized layer
103
and the passivation layer
102
. The opening
104
is for connecting the pad and the opening
106
is for connecting the scribe. Then, a microlens resist layer
110
id
formed over the opening
104
, the opening
106
and the planarized layer
103
. It is observable that the microlens resist layer
110
has different thickness at different points.
Especially, the photoresist in the opening
104
has a thickness Hi of about 4-5 &mgr;m.
Next, referring to
FIG. 1B
, a photoresist layer
112
is formed and patterned on the microlens resist layer
110
. Then, referring to
FIG. 1C
, as the photoresist layer
112
as a mask, the microlens resist layer
110
is etched to expose the opening
104
and the opening
106
. Then, referring to
FIG. 1D
, the photoresist layer
112
is removed to expose the patterned microlens resist block
110
a.
The microlens resist block
110
a
is aligned to the color filter
108
. The microlens resist block
110
a
includes a number of protuberances
110
a.
The cross section of each protuberance
110
a
can be rectangle or polygon.
Next, referring to FIG.
1
E and
FIG. 1F
, an after-development-exposure step is performed so that the microlens resist blocks
110
a
becomes a number of semi-circle microlens
110
b.
Then, after curing treatment onto the semi-circle microlens
110
b,
conventional microlens structure of a color filter of a CMOS sensor device is accomplished.
However, the conventional process for forming CMOS sensor device has lots of drawbacks. For example, the thickness of the microlens resist layer
110
in the pad opening
104
is more than at other point for about 4-5 &mgr;m. As a result, the exposure energy required for different points has a great variety. If an exposure energy suitable for exposing the region around the color filter
108
is used, scum effect will occur in the pad opening due to insufficient energy. On the other hand, if an exposure energy suitable for exposing the region around the pad opening
104
is used, after exposure and development, the defined microlens resist block
110
a
will have shrinking size, even, of 2-3 &mgr;m. That is because of over-exposure. Especially for pixel size of less than 10 &mgr;m, error of 2-3 &mgr;m produces a great influence.
SUMMARY OF THE INVENTION
It is therefore an objective of the present invention to provide a method of fabricating a CMOS sensor device, by regional exposure and using one more step of photoresist coating and exposure. Certain predetermined regions can be exposed with larger dosage and longer period. Some other regions can be exposed with less dosage. Consequently, the size of the defined microlens resist block
110
a
will not shrink and also scum will not occur.
It is another an objective of the present invention to provide a method of fabricating a complementary metal-oxide-semiconductor (CMOS) sensor device. A planarized layer is formed on the substrate, and an opening is formed. A microlens resist layer is formed over the planarized layer, wherein the microlens resist layer has a bigger thickness in the opening than on the planarized layer. A first photoresist layer is formed on the microlens layer. The first photoresist layer has a pattern align to the color filter. A first exposure step is performed at least onto the microlens layer to form a first exposed portion, using the first photoresist layer as a mask, and the first photoresist layer is removed. A second photoresist layer is performed on the microlens resist layer. The second photoresist layer has a pattern align to the opening. A second exposure step is performed at least onto the microlens layer to form a second exposed portion, using the second photoresist layer as a mask, and the second photoresist layer is removed. A positive development step is performed to remove the first exposed portion and the second exposed portion of the microlens resist layer and to form a plurality of microlens blocks align to the color filter. An after-development-exposure step and a curing step are performed so that each of the microlens blocks forms a microlens. The microlens has a substantially rounded semi-circle structure.


REFERENCES:
patent: 5266501 (1993-11-01), Imai
patent: 5336367 (1994-08-01), Nomura
patent: 5470760 (1995-11-01), Nakai
patent: 5595930 (1997-01-01), Baek
patent: 5672519 (1997-09-01), Song
patent: 5677200 (1997-10-01), Park
patent: 6157017 (2000-12-01), Kim

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