Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2000-04-27
2002-04-23
Tran, Minh Loan (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S291000, C257S292000, C257S432000, C257S440000
Reexamination Certificate
active
06376872
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to light-sensitive devices, and more particularly, to a focusing and color-filtering structure for use in a semiconductor light-sensitive device, such as a CMOS (complementary metal-oxide semiconductor) light-sensitive device and a method of fabricating the same.
2. Description of Related Art
A digital camera, or a PC (personal computer) camera, is a digital photographic apparatus that can produce photographed images directly in digital form instead of on traditional films, thus allowing immediate computer processing of the photographed images. A conventional digital camera typically includes an array of light-sensitive cells, such as CMOS (complementary metal-oxide semiconductor) light-sensitive diodes, which can convert the light incident thereon into analog electrical signals that can be further converted into digital form. These CMOS light-sensitive diodes are formed on a semiconductor substrate. Further, a focusing and color-filtering structure is formed over the CMOS light-sensitive diodes for focusing the incident light onto the corresponding light-sensitive diodes and also for separating the incident light into the three primary components, i.e., red (R), green (G), and blue (B) components prior to the light being detected by the light-sensitive diodes.
A conventional focusing and color-filtering structure for a CMOS light-sensitive device is illustratively depicted in the following with reference to
FIGS. 1A-1B
.
As shown in
FIG. 1A
, the CMOS light-sensitive device is constructed on a semiconductor substrate
10
. A passivation layer
12
is formed over the substrate
10
. Next, a plurality of color-filter layers
14
are formed over the passivation layer
12
, each of the color-filter layers
14
consisting of a red-filter region (not shown), a green-filter region (not shown), and a blue-filter region (not shown), which are formed, for example, from acrylic materials of the respective color-filtering qualities. A planarization layer
16
is then deposited over the color-filter layers
14
.
It is illustratively shown in
FIG. 1A
that the part of the planarization layer
16
that is deposited over the area where the color-filter layers
14
are located (hereinafter referred to as the filter area) and the part of the planarization layer
16
that is deposited over the area beyond the filter area (hereinafter referred to as the non-filter area) would have uneven thicknesses, resulting in a slope (as indicated by the reference numeral
18
in
FIG. 1A
) at the border between the filter area and the non-filter area. The forming of this slope
18
would cause some undesired drawbacks to the focusing and color-filtering structure, which will be described later.
Referring next to
FIG. 1B
, in the subsequent step, an array of microlenses
19
are formed over the planarization layer
16
, with each of the microlenses
19
being aligned with one of the color-filter layers
14
. The microlenses
19
are each used to focus the light incident thereon through the color-filter layers
14
onto the corresponding one of the light-sensitive diodes (not shown) in the substrate
10
. This completes the fabrication of the CMOS light-sensitive device. The microlenses
19
, the planarization layer
16
, and the color-filter layers
14
are in combination referred to as a focusing and color-filtering structure for the CMOS light-sensitive device.
One drawback to the foregoing focusing and color-filtering structure, however, is that some of the microlenses
19
that are disposed on the slope
18
will have their optical axis slanted and thus misaligned with their corresponding light-sensitive diodes, thus resulting in a shift in the focused point. Moreover, since those of the microlenses
19
on the slope
18
are somewhat lower in position than those of the microlenses
19
that are not, the photographed image can be defocused, thus resulting in a blurred image. Still moreover, since those of the microlenses
19
on the slope
18
are somewhat inclined sidewards, the ambient scattering light from the side can easily enter into these microlenses
19
on the slope
18
, thus resulting in an undesired reception of unwanted light that would further degrade the quality of the photographed image.
SUMMARY OF THE INVENTION
It is therefore an objective of the present invention to provide an improved focusing and color-filtering structure for CMOS light-sensitive device and a method of fabricating the same, which can allow the planarization layer mentioned in the foregoing background section to be formed with a substantially uniformly flat top surface without having slopes, thus allowing the subsequently formed microlenses to be all disposed upright in position without being slanted.
In accordance with the foregoing and other objectives of the present invention, an improved focusing and color-filtering structure for CMOS light-sensitive device and a method of fabricating the same are provided.
The focusing and color-filtering structure of the invention includes the following constituent elements: a passivation layer formed over the substrate; an array of color-filter layers formed over a selected area on the passivation layer; at least one dummy pattern layer formed over the passivation layer surrounding the array of color-filter layers; a planarization layer covering all of the color-filter layers and the dummy pattern layer; and an array of microlenses formed over the planarization layer, with each of the microlenses being aligned with one of the underlying color-filter layers.
The method of the invention for fabricating the foregoing focusing and color-filtering structure includes the following steps of:
(1) forming a passivation layer over the substrate;
(2) forming an array of color-filter layers over a selected area on the passivation layer;
(3) forming at least one dummy pattern layer over the passivation layer surrounding the array of color-filter layers;
(4) forming a planarization layer which covers all of the color-filter layers and the dummy pattern layer; and
(5) forming an array of microlenses over the planarization layer, with each of the microlenses being aligned with one of the underlying color-filter layers.
REFERENCES:
patent: 5256592 (1993-10-01), Matsushita
patent: 5426058 (1995-06-01), Nakai et al.
patent: 5965939 (1999-10-01), Kim et al.
patent: 62242360 (1987-10-01), None
patent: 6132515 (1994-05-01), None
patent: 7311310 (1995-11-01), None
patent: 9-96716 (1997-04-01), None
patent: 9-325206 (1997-12-01), None
Lin Wei-Chiang
Pai Yuan-Chi
Christie Parker & Hale LLP
Tran Minh Loan
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