Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2001-08-29
2003-12-09
Jackson, Jerome (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S293000, C257S010000, C257S233000
Reexamination Certificate
active
06661046
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an image sensor, and, more particularly, to an image sensor having a convex-shape color filter pattern that acts as a micro-lens, thereby achieving improved optical transmittance.
BACKGROUND OF THE INVENTION
As is well known, an image sensor is an apparatus for sensing a light beam reflected from an object to generate image data. An image sensor fabricated by using complementary metal oxide semiconductor (CMOS) technology, for example, is called a CMOS image sensor.
Generally, the CMOS image sensor includes a plurality of unit pixels, including a light sensing element and a plurality of transistors. The light sensing element, such as a photodiode, senses the incident light beam and generates photoelectric charges corresponding to the amount of the incident light beam sensed. The transistors perform switching operations to control transfer of the photoelectric charges.
FIG. 1
is a circuit diagram showing a conventional unit pixel
10
contained in a CMOS image sensor. Here, a reference symbol ML represents a load transistor for controlling a current that flows via an output node NO of the unit pixel
10
. The unit pixel
10
includes a photodiode
12
and four transistors: a transfer transistor MT, a reset transistor MR, a drive transistor MD and a select transistor MS. Reference numerals TX, RX and SX denote control signals to turn on and off the transistors MT, MR and MS, respectively.
The photodiode
12
senses an incident light to generate photoelectric charges. The transfer transistor MT, coupled between the photodiode
12
and a sensing node NS, transfers the photoelectric charges to the sensing node NS. The reset transistor MR, coupled between a power terminal VDD and the sensing node NS, transfers a reset voltage level from the voltage source to the photodiode
12
and the drive transistor MD.
The drive transistor MD, whose drain is coupled to the power terminal VDD, amplifies a voltage level at the sensing node NS to output an amplified signal. The select transistor MS, coupled between the drive transistor MD and the output node NO, performs a switching operation to output the amplified signal as image data via the output node NO.
FIG. 2
is a cross-sectional view showing a conventional CMOS image sensor, where a field oxide layer
21
, a transfer transistor
22
and a photodiode
23
are formed on a semiconductor substrate
20
. An insulating layer
24
and a color filter
25
are sequentially formed on the entire semiconductor structure. Additionally, an over coating layer (OCL)
26
for planarization is formed on the color filter
25
, and a micro-lens
27
is formed on the OCL
26
.
In such conventional sensors, since the color filter
25
, the OCL
26
and the micro-lens
27
are formed by using separate photoresist layers, an exposure step and a development step are carried out for each layer. It is, therefore, difficult to selectively replace a defective layer among the stacked photoresists. Additionally, the optical transmittance is low in such multilayer CMOS image sensors and residual products that affect sensor performance can occur during fabrication.
SUMMARY OF THE INVENTION
In accordance with an aspect of the present invention, a CMOS image sensor is provided which comprises: a semiconductor structure; an insulating layer formed on the semiconductor structure, wherein the insulating layer has a trench; and a convex-shaped color filter pattern formed on the insulating layer and covering the trench.
In accordance with an aspect of the present invention, a method is provided for fabricating a CMOS image sensor. The method comprises the steps of: a) providing a semiconductor structure; b) forming an insulating layer on the semiconductor structure; c) selectively etching the insulating layer to form a trench; d) coating a dyed photoresist on the insulating layer, wherein the dyed photoresist covers the trench; e) carrying out an exposure operation and a development operation on the dyed photoresist to thereby obtain a color filter pattern; and f) performing a thermal treatment, so that the color filter pattern develops a convex shape.
REFERENCES:
patent: 5371397 (1994-12-01), Maegawa et al.
patent: 6002145 (1999-12-01), Niisoe
patent: 6031512 (2000-02-01), Kadota et al.
patent: 6194244 (2001-02-01), Yamaguchi et al.
patent: 2001061056 (2001-07-01), None
Hyundai Electronics Industries Co,. Ltd.
Jackson Jerome
Marshall & Gerstein & Borun LLP
Nguyen Joseph
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