Method of manufacturing a color filter

A method for manufacturing a color filter including the steps of: coating a photosensitive resin subject to dyeing on a substrate; forming a pattern on the photosensitive resin layer; dyeing the resultant patterned layer with a coloring matter; forming a condenser lens with transparent and dyeing resistant resin on the surface of the dyed pattern layer; and repeating the above processes at least two times eventually to form at least three colored pattern layers. By the method, since the entire thickness of the color filter is reduced and the layer construction is simplified, light transmittance is increased, the sensitivity of the photocell is enhanced as well as materials curtailed.

FIELD OF THE INVENTION 
The present invention relates to a method for manufacturing a color filter, 
and more particularly to a method for manufacturing color filter having a 
condenser lens to improve a sensitivity. 
BACKGROUND OF THE INVENTION 
Recently, according to the increased demand of a video camera for use in 
the home, it has been required that the video camera be smaller in size 
and lighter in weight. Therefore, as a pickup device of a video camera, a 
conventional pickup tube has been changed to a solid state image sensing 
device. In a charge coupled device or metal oxide semiconductor type solid 
state image sensing device in which high density semiconductor technolgy 
is adopted, the tendency of color conversion is accelerated and the 
resolution is rapidly enhanced according to the progress of high density 
technology in the semiconductor field. 
A color solid state image sensing device has been embodied by adopting a 
color filter on the photocell array region in the form of a matrix. The 
color filter has at least three coloring pattern groups, each having color 
resolution characteristics different from one another. In the case of a 
combination of three primary colors, the color filter has red, blue and 
green coloring pattern groups, and in the case of a combination of 
complementary colors, it has cyan, yellow and magenta coloring pattern 
groups. Accordingly, to manufacture the color filter on the photocell 
array region of the solid state image sensing device, processes of coating 
photosensitive resins, exposure, development, dyeing and color mixture 
prevention should be carried out at least three times. Accordingly, the 
color filter has a structure in which a plurality of layers are laminated 
so that it becomes very thick. Therefore, in such a thick color filter the 
quantity of transmitted light eventually arriving at the photocell array 
is decreased, thereby lowering the sensitivity of the solid state image 
sensing device. 
To solve the problem of the decrease of light transmittance due to the 
thickness of the color filter, Japanese patent laid-open publication No. 
61-199659 discloses a technique for enhancing the sensitivity by focusing 
the light onto each photocell after forming the condenser lens array on a 
surface of the color filter to be overlapped with the photocell array. 
However, this system is very complicated in its structure. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide a method for 
manufacturing a color filter in which the quantity of transmitted light 
can be increased. 
Another object of the present invention is to provide a method for 
manufacturing a color filter which can improve the sensitivity of a solid 
state image sensing device. 
Yet another object of the present invention is to provide a method for 
manufacturing an economical color filter by the simplification of the 
manufacturing process and the curtailment of materials. 
For carrying out the above and other objects, the method for manufacturing 
the color filter according to the present invention comprises the steps 
of: (a) coating a photosensitive resin subject to dyeing on a substrate; 
(b) exposing and developing a predetermined pattern on the photosensitive 
resin layer formed in the above process and leaving the predetermined 
pattern; (c) dyeing the patterned layer with a predetermined coloring 
matter; (d) forming a condenser lens having a predetermined radius of 
curvature on the surface of the dyed pattern layer; and repeating the 
above-mentioned serial processes (a) to (d) at least two times eventually 
to form at least three colored pattern layers. 
Here, when a semiconductor substrate is used as a solid state image sensing 
device, before coating of the photosensitive resin, a surface planarizing 
process and a process for coating a bonding pad protection layer are first 
carried out. At this time, optimum focusing is obtained by controlling the 
thickness of a planarizing layer. 
And, heat resistant and dyeing resistant materials are used for forming the 
condenser lens. Accordingly, the condenser lens has a color mixture 
prevention function, so that the intermediate layers for the color mixture 
prevention can be removed, thereby reducing the entire thickness of the 
color filter. 
These and other objects, features and advantages of the present invention 
will become more apparent upon consideration of the following description 
of the preferred embodiments of the present invention taken in conjunction 
with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION 
To begin with, prior to explaining the preferred embodiment according to 
the present invention, a method for manufacturing a conventional color 
filter will be explained below with reference to FIG. 1A to FIG. 1E. 
Referring to FIG. 1A, the reference numeral 1 designates a semiconductor 
substrate of the solid state image sensing device having prominences and 
recesses in the upper portion thereof. The semiconductor substrate 1 is a 
portion of the photocell array region and has photocells 1a, 1b and 1c in 
the respective recesses. The photocells are photodiodes formed in the 
semiconductor substrate 1. In the prominence of the semiconductor 
substrate 1, an insulating layer and a conductive layer for wiring are 
formed. On the upper surface of the semiconductor substrate in which the 
prominence and recess portions are formed, a planarizing layer 2 is formed 
by coating an organic high polymer material such as a polyimide, and then 
a protective layer 3 having dyeing resistance is coated for protecting a 
bonding pad which is not shown. The protective layer 3 prevents the 
bonding pad from corrosion during the formation of the colored pattern 
discussed later. 
Referring to FIG. 1B, on the surface of the protective layer 3, the 
photosensitive resin such as a gelatin or casein containing chlorine 
dichromate is coated and then a first colored pattern 4 is formed by 
exposing and developing the predetermined portion of the layer 3 to be 
left via photolithographic process. Thereafter, a color mixture prevention 
material such as a polyglicidyl methacrylate is coated on the surface of 
the resultant structure in which the first colored pattern 4 is formed. By 
the process shown in FIG. 1B, the first color pattern layer 4 is formed on 
the protective layer 3 and is disposed above the photocell 1a. 
If the process of FIG. 1B is twice repeated sequencially with respect to 
photocells 1b and 1c, a second colored pattern layer 6, an intermediate 
layer 7, a third colored pattern layer 8 and an intermediate layer 9 are 
sequentially formed as shown in FIG. 1C and FIG. 1D. 
Referring to FIG. 1E, on a surface of the resultant structure in which the 
first, second and third colored pattern layers 4,6 and 8, and intermediate 
layers 5, 7 and 9 are formed by the above processes, a focus controlling 
layer 10 is formed by coating such materials as polyglicidyl methacrylate 
with a predetermined thickness. Thereafter, a transparent resin material 
such as an acrylic resin is coated on the focus controlling layer 10 and 
then patterned to be overlapped with the photocells by the 
photolithographic process and heated at a predetermined temperature to 
reflow, and then softbaked. Thus, a condenser lens having a predetermined 
radius of curvature can be obtained (Refer to Japanese Patent laid-open 
No. 60-60757). 
As illustrated, in FIG. 1A to FIG. 1E, since the color filter mounted on 
the solid state image sensing device has at least three intermediate 
layers for preventing color mixture, the entire structure thereof becomes 
very thick, measuring about 10 to 12 .mu.m. Accordingly, an optical path 
leading to the photocell is complicated and the sensitivity is lowered due 
to the reduction of the light transmitted. 
Also, since many steps of processes are needed to manufacture the color 
filter and a plurality of the intermediate layers should be formed, it has 
such problems that operation efficiency is lowered and waste of materials 
occurs. 
Next, a specific embodiment of the present invention will be explained with 
respect to FIGS. 2A to 2D. 
The process illustrated in FIG. 2A is the same as that of FIG. 1A. 
The process illustrated in FIG. 2B is the same as that of FIG. 1B except 
that the intermediate layer 5 for preventing the color mixture is replaced 
by a condenser lens 11a. In more detail, after coating the photosensitive 
resin on the protective layer 3 and leaving the first colored pattern 
layer 4 through the exposure and development process, the condenser lens 
11a is formed with a transparent resin on the first colored pattern layer 
having good heat resistance and dyeing resistance through the known lens 
forming technology. Accordingly, the condenser lens 11a has a color 
mixture prevention function as well as focusing function, thereby 
preventing the color mixture of the first colored pattern layer 4 during 
the next dyeing process. 
In FIG. 2C and FIG. 2D, a second colored pattern layer 6, a condenser lens 
11b, a third colored pattern layer 8 and a condenser lens 11c are formed 
by sequentially repeating such process as shown in FIG. 2B. Here, base 
resistant material can be used for forming the condenser lenses 11a, 11b 
and 11c. Also, if the condenser lenses 11a, 11b and 11c are formed with 
the photosensitive resin, it is preferable to use a photosensitive resin 
having a radiation sensitivity characteristic different from that of the 
colored pattern layers 4, 6 and 8, in view of the simplication of the 
process. 
As mentioned above, according to the present invention, the coating process 
of the color mixture preventing intermediate layers 5, 7 and 9 is no 
longer necessary after forming colored pattern layers 4, 6 and 8, but 
instead the condenser lenses are formed one by one directly on the colored 
pattern layer, thereby preventing the occurance of the undesirable color 
mixture. As a result, the intermediate layers 5, 7 and 9 can be removed, 
so that entire thickness of the color filter can be reduced to 5.about.6 
.mu.m. 
Therefore, according to the present invention, since the entire thickness 
of the color filter is reduced and the layer construction is simplified, 
light transmittance is increased and, the sensitivity of the photocell is 
enhanced as well as materials curtailed.