Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2001-08-16
2002-04-09
Ngô, Ngân V. (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S292000, C257S432000, C438S059000, C438S065000, C438S069000, C438S073000
Reexamination Certificate
active
06369417
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a semiconductor device, and, more particularly, to a CMOS image sensor capable of preventing a surface of a metal line therein from being damaged or contaminated, thereby improving performance of a semiconductor memory device.
BACKGROUND OF THE INVENTION
As is well known, an image sensor is an apparatus generating image data by sensing a light beam reflected from an object. An exemplary image sensor fabricated by a complementary metal oxide semiconductor (CMOS) technology is called a CMOS image sensor.
Generally, the CMOS image sensor includes a plurality of unit pixels, each unit pixel including a light sensing element and a plurality of transistors. The light sensing element, such as a photodiode, senses an incident light beam and generates photoelectric charges corresponding to the amount of the incident light beam received. The transistors perform switching operations to control transfer of the photoelectric charges.
FIGS. 1A
to
1
D are cross-sectional views showing sequential steps of fabricating a conventional CMOS image sensor. Here, reference numerals
100
and
150
represent a unit pixel area and a pad area, respectively. For convenience purposes, the distance between the unit pixel area
100
and the pad area
150
has been truncated by a split view.
Referring to
FIG. 1A
, a series of operations are carried out to provide a semiconductor structure that has a metal line
101
on an upper portion thereof, the metal line
101
extending from the unit pixel area
100
into the pad area
150
. After forming an anti-reflection layer
102
of about 300 Å on the metal line
101
, an oxide layer
103
and a nitride layer
104
, together forming a passivation layer, are stacked on the entire structure extending from the unit pixel area
100
into the pad area
150
.
Referring to
FIG. 1B
, the nitride layer
104
, the oxide layer
103
and the anti-reflection layer
102
are selectively etched to expose a portion of the metal line
101
and create a pad open area
105
.
Referring to
FIG. 1C
, a dyed photoresist
106
is coated on the entire structure. Then, an exposure and development operation is carried out to form a color filter
106
over a light sensing region of the CMOS image sensor. At this time, a portion of the dyed photoresist
106
, i.e., the photoresist pattern
106
b,
covering the pad open portion
105
, is removed during the develop operation. Then, a thermal treatment is performed at a temperature of 145° C. to 150° C.
Referring to
FIG. 1D
, after patterning the color filter
106
A, the resulting structure is soaked in a developing solution. This soaking step erodes a portion of the surface of the metal line
107
, leaving a high resistance oxide layer
108
. This high resistance oxide layer
108
forms a poor contact with any metal ball connected thereto for driving the circuit.
It is, therefore, desirable to have a CMOS image sensor capable of preventing a surface of a metal line from being damaged, oxidized, or otherwise contaminated, thereby improving the performance of the semiconductor memory device.
SUMMARY OF THE INVENTION
In accordance with an aspect of the invention, there is provided a CMOS image sensor comprising: a semiconductor structure, wherein the semiconductor structure includes a unit pixel area and a pad area; a metal line formed on the pad area, wherein a portion of the metal line is exposed; a passivation layer formed on the unit pixel area and on the metal line such that the exposed portion of the metal line is left exposed; a planarized photoresist formed on a portion of the passivation layer; a micro-lens formed on a portion of the planarized photoresist; and an oxide layer formed on the micro-lens, the photoresist, and the passivation layer such that the exposed portion is left exposed.
In accordance with another aspect of the invention, there is provided a method for fabricating a CMOS image sensor, comprising the steps of: a) providing a semiconductor structure, wherein the semiconductor structure includes a metal line formed on an upper portion of the semiconductor structure; b) forming a passivation layer on the metal line; c) forming a planarized photoresist on a portion of the passivation layer; d) forming a micro-lens on a portion of the planarized photoresist; e) forming an oxide layer on the micro-lens, the photoresist, and the passivation layer; and f) forming a pad open mask and etching the oxide layer and the passivation layer to expose a portion of the metal line.
REFERENCES:
patent: 5986297 (1999-11-01), Guidash et al.
patent: 6180969 (2001-01-01), Yang et al.
Hyundai Electronics Industries Co,. Ltd.
Marshall Gerstein & Borun
Ngo Ngan V.
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