Semiconductor device manufacturing: process – Making device or circuit responsive to nonelectrical signal – Responsive to electromagnetic radiation
Reexamination Certificate
1998-08-17
2001-06-26
Meier, Stephen D. (Department: 2822)
Semiconductor device manufacturing: process
Making device or circuit responsive to nonelectrical signal
Responsive to electromagnetic radiation
C438S060000, C438S069000, C438S075000
Reexamination Certificate
active
06251700
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Taiwan application Ser. No. 87109588, filed Jun. 16, 1998, the full disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a method of manufacturing complementary metal-oxide-semiconductor (CMOS) photosensitive devices. More particularly, the present invention relates to a method of manufacturing the color filter of a CMOS photosensitive device that reduces the number of fabricating steps, and thus saves processing time and production cost.
2. Description of Related Art
CMOS diode devices are commonly used inside conventional PC cameras and digital cameras. In general, a CMOS diode device comprises a photosensitive layer on a wafer substrate, and there are various light-sensitive regions in the photosensitive layer for the purpose of sensing different colors of light. Furthermore, a color filter is formed above the photosensitive layer, and a film is formed to cover the color filter. In general, light of different colors comes from various directions. When the incoming light passes through the color filter, it is filtered into three colors, for example, red, green and blue, and then is absorbed and detected by the corresponding light-sensitive regions of the photosensitive layer.
FIG. 1
is a flow chart showing the manufacturing steps for fabricating a conventional CMOS photosensitive device. First, in step
10
, a first passivation layer is formed over a wafer substrate. Next, a photolithographic process
11
is carried out to form a patterned photoresist layer on the first passivation layer. Thereafter, the first passivation layer is etched in operation
12
using the photoresist layer as a mask. Subsequently, a melting, operation
13
is carried out by heating the first passivation layer. Next, step
14
is carried out to form color filters over the first passivation layer. The color filters are used to filter incoming light so that monochromatic light of different colors is produced. After that, step
15
is carried out to form a planar second passivation layer over the color filters. Then, another photolithographic operation
16
is performed, forming another patterned photoresist layer over the second passivation layer. Next, the second passivation layer is etched in operation
17
, using the photoresist layer as a mask. Finally, step
18
is carried out in which micro-lenses are formed on top of the second passivation layer, in locations that correspond to the color filters.
FIGS. 2A through 2K
are cross-sectional views showing the progression of manufacturing steps in fabricating a CMOS photosensitive device according to a conventional method. First, as shown in
FIG. 2A
, a wafer substrate
20
is provided, and a patterned first passivation layer
21
is formed over the wafer substrate
20
. Next, as shown in
FIG. 2B
, a first photoresist layer
22
is formed over the first passivation layer
21
, and then the first photoresist layer
22
is patterned. Next, as shown in
FIG. 2C
, using the patterned first photoresist layer
22
as a mask, the first passivation layer
21
is etched to form an opening
23
that exposes a portion of the wafer substrate
20
. The opening
23
is used as a connection pad in subsequent step. Next, as shown in
FIG. 2D
, the first photoresist layer
22
is removed.
Next, as shown in
FIG. 2E. a
transparent layer
24
having a planar surface is formed over the first passivation layer
21
, the wafer substrate
20
and into the opening
23
. Subsequently, as shown in
FIG. 2F
, color filters including a red filter region
25
a
, a green filter region
25
b
and a blue filter region
25
c
are formed over the planar transparent layer
24
. The color filters are made from a material including acrylic. Next, as shown in
FIG. 2G
, a second passivation layer
26
having a planar surface is formed over the red filter region
25
a
, the green filter region
25
b
, the blue filter region
25
c
and the transparent layer
24
. Next, as shown in
FIG. 2H
, a second photoresist layer
27
is formed over the second passivation layer
26
, and then the second photoresist layer
27
is patterned.
Next, as shown in
FIG. 21
, using the patterned second photoresist layer
27
as a mask, the second passivation layer
26
and the transparent layer
24
are etched to form an opening
23
a
that exposes the wafer substrate
20
. The opening
23
a
serves as a connection pad in subsequent steps. Next, as shown in
FIG. 2J
, the second photoresist layer
27
is removed. Finally, as shown in
FIG. 2K
, micro-lens
29
a
,
29
b
and
29
c
are formed over the second passivation layer
26
. Micro-lens
29
a
,
29
b
and
29
c
are located above the red filter region
25
a
, the green filter region
25
b
and the blue filter region
25
c
, respectively. In this manner, fabrication of a conventional CMOS photosensitive device is complete.
However, the above method of forming a CMOS photosensitive device has a number of defects, including:
1. The manufacturing operation involves lot of steps. In particular, after the color filters
25
are formed over the first passivation layer
24
, another photolithographic and etching operation for another passivation layer has to be carried out. Therefore, cycle time and hence the production cost is increased.
2. The pad opening
23
formed early in the process and may lead to pad charge or pad pit problems when the photoresist is reworked.
In light of the foregoing, there is a need to provide an improved method of manufacturing a CMOS photosensitive device.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a method of fabricating a CMOS photosensitive device that combines a two-step pad opening operation into one so that only one photolithographic and etching operation of the passivation layer is necessary after the color filters are formed. With this arrangement, the number of fabrication steps is reduced. Moreover, pad charge and pad pit problems are also avoided.
To achieve these and other advantages and in accordance with the purpose of the invention. as embodied and broadly described herein, the invention provides a method of fabricating a CMOS photosensitive device. In this method, a wafer substrate is provided and then a first passivation layer is formed over the wafer substrate. Next, the first passivation layer is heated so that it melts. The purpose of melting the first passivation layer is to densify it and relieve its internal stress. The first passivation layer is made from a material that includes silicon nitride or silicon oxide. Thereafter, color filters including a red filter region, a green filter region and a blue filter region are formed over the first passivation layer. The color filters are used to filter out monochromatic light of different colors. The color filters are made from a material that includes acrylic. Subsequently a second passivation layer having a planar top surface is formed over the color filters. The second passivation layer is made from a material that includes silicon nitride or silicon oxide.
Next, photolithographic and etching operations are carried out to form an opening through the second passivation layer and the first passivation layer exposing the substrate wafer. Finally, a micro-lens layer is formed over the second passivation layer such that an individual micro-lens is positioned above each color filter. The micro-lenses can be formed using photoresist material.
It is to be understood that both the foregoing general description and the following detailed description are exemplary. and are intended to provide further explanation of the invention as claimed.
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patent: 4749662 (1988-06-01), Custode
patent: 5216414 (1993-06-01), Fukutani
patent: 5266501 (1993-11-01), Imai
patent: 5404005 (1995-04-01), Shimomura et al.
patent: 5554446 (1996-09-01), Matsushima et al.
patent: 5561319 (1996-10-01), Owens et al.
patent: 5593913 (1997-01-01), Aoki
patent: 5595930 (1997-01-01), Baek
pate
Lin Wei-Chiang
Pai Yuan-Chi
Goodwin David
Meier Stephen D.
Thomas Kayden Horstemeyer & Risley LLP
United Microelectronics Corp.
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