U.S. patent application number 14/041744 was filed with the patent office on 2015-01-22 for cmos image sensor having optical block area.
This patent application is currently assigned to POSTECH ACADEMY-INDUSTRY FOUNDATION. The applicant listed for this patent is POSTECH ACADEMY-INDUSTRY FOUNDATION, SK hynix Inc.. Invention is credited to Young Woong DO, Hae Wook HAN, Do Hwan KIM, Won Jun LEE, Su Hwan LIM.
Application Number | 20150021604 14/041744 |
Document ID | / |
Family ID | 52301664 |
Filed Date | 2015-01-22 |
United States Patent
Application |
20150021604 |
Kind Code |
A1 |
KIM; Do Hwan ; et
al. |
January 22, 2015 |
CMOS IMAGE SENSOR HAVING OPTICAL BLOCK AREA
Abstract
A CMOS image sensor includes an active pixel structure suitable
for sensing light incident from outside and converting a sensed
light into an electrical signal, and an optical block structure
suitable for blocking a visible light and passing a UV light to
check and evaluate an electrical characteristic of the active pixel
area. The UV pass filter includes first and second insulation
layers comprising an insulator, and a metal layer formed between
the first and second insulation layers.
Inventors: |
KIM; Do Hwan; (Gyeonggi-do,
KR) ; LIM; Su Hwan; (Gyeonggi-do, KR) ; HAN;
Hae Wook; (Gyeonggi-do, KR) ; DO; Young Woong;
(Gyeonggi-do, KR) ; LEE; Won Jun; (Gyeonggi-do,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
POSTECH ACADEMY-INDUSTRY FOUNDATION
SK hynix Inc. |
Gyeongsangbuk-do
Gyeonggi-do |
|
KR
KR |
|
|
Assignee: |
POSTECH ACADEMY-INDUSTRY
FOUNDATION
Gyeongsangbuk-do
KR
SK hynix Inc.
Gyeonggi-do
KR
|
Family ID: |
52301664 |
Appl. No.: |
14/041744 |
Filed: |
September 30, 2013 |
Current U.S.
Class: |
257/48 |
Current CPC
Class: |
H01L 27/14623 20130101;
H01L 27/14625 20130101; H01L 27/14621 20130101 |
Class at
Publication: |
257/48 |
International
Class: |
H01L 27/146 20060101
H01L027/146 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 18, 2013 |
KR |
10-2013-0084455 |
Claims
1. A CMOS image sensor comprising: an active pixel structure
suitable for sensing light incident from outside and converting a
sensed light into an electrical signal; and an optical block
structure suitable for blocking a visible light and passing a UV
light to check and evaluate an electrical characteristic of the
active pixel area, wherein the optical block structure comprises a
UV pass filter comprising: first and second insulation layers
comprising an insulator, and a metal layer formed between the first
and second insulation layers.
2. The CMOS image sensor of claim 1, wherein the metal layer
comprises a plurality of metal chips and spaces surrounding each
metal chip.
3. The CMOS image sensor of claim 2, wherein the metal chips have a
width larger than the space.
4. The CMOS image sensor of claim 2, wherein the metal chips have
the same shape.
5. The CMOS image sensor of claim 2, wherein the metal chips are
arranged in a direction substantially parallel to the first and
second insulation layers.
6. The CMOS image sensor of claim 1, wherein the metal layer is
formed by a metal including a plurality of holes inside the
metal.
7. The CMOS image sensor of claim 6, wherein the holes have a
diameter larger than a space between the respective holes.
8. The CMOS image sensor of claim 6, wherein the holes have the
same shape.
9. A CMOS image sensor comprising: an active pixel structure
suitable for sensing light incident from outside and converting a
sensed light into an electrical signal; and an optical block
structure suitable for blocking a visible light and passing a UV
light to check and evaluate an electrical characteristic of the
active pixel area, wherein the optical block structure comprises a
UV pass filter comprising: a plurality of insulation layers
comprising an insulator, respectively, and a plurality of metal
layers formed between the first and second insulation layers,
respectively.
10. The CMOS image sensor of claim 9, wherein each metal layer
comprises a plurality of metal chips and spaces surrounding each
metal chip.
11. The CMOS image sensor of claim 10, wherein the metal chips have
a width larger than the space.
12. The CMOS image sensor of claim 10, wherein the metal chips have
the same shape.
13. The CMOS image sensor of claim 10, wherein the metal chips are
arranged substantially in a direction parallel to the insulation
layers.
14. The CMOS image sensor of claim 9, wherein each metal layer is
formed by a metal including a plurality of holes inside the
metal.
15. The CMOS image sensor of claim 14, wherein the holes formed in
each of the metal layers have a diameter larger than the space
between the holes.
16. The CMOS image sensor of claim 14, The CMOS image sensor of
claim 12, wherein the holes have the same shape.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority of Korean Patent
Application No. 10-2013-0084455, filed on Jul. 18, 2013, which is
incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTIONS
[0002] 1. Field of the Invention
[0003] The embodiments of the present invention relate to an image
sensor, and more particularly, to a CMOS image sensor having an
optical block area set in a pixel array.
[0004] 2. Description of the Related Art
[0005] With the development of electronic communication, digital
devices having a digital processing function, such as digital
cameras, mobile phones, game machines, and micro cameras, have been
rapidly spread. Most of the digital devices include an image sensor
required for taking an image.
[0006] The image sensor senses an image. Specifically, the image
sensor converts an image inputted as light from outside into an
electrical signal and transmits the electrical signal to a digital
processing device. Examples of the image sensor may include a
charge coupled device (CCD) image sensor and a complementary metal
oxide semiconductor (CMOS) image sensor.
[0007] The CCD image sensor includes a photodiode, a CCD, and a
signal detection circuit, which are formed over a P-type impurity
layer. The photodiode serves to convert light incident from outside
into an electric charge, the CCD serves to transmit the electric
charge to the signal detection circuit, and the signal detection
circuit serves to convert the electric charge into a voltage.
[0008] The CMOS image sensor includes CMOS transistors each
configured in a complementary manner to join a PMOS (P channel
Metal Oxide Semiconductor) transistor and an NMOS (N channel Metal
Oxide Semiconductor) transistor, in order to convert an input image
into an electrical signal. The CMOS image sensor has an advantage
in which it has high integration degree and low power
consumption.
[0009] The image sensor includes a. light sensing unit configured
to receive light incident from outside and generate and store
photo-charges. The image sensor further includes a color filter
disposed over the light sensing unit. The color filter may have
three colors of red, green, and blue or three colors of yellow,
magenta, and cyan.
[0010] In particular, the CMOS image sensor includes an optical
block area for blocking light from being irradiated onto pixels.
The pixels formed in the optical block area are optional pixels for
black level correction, and are used for controlling a pixel
output. Since the optical block area uses a pixel output as an
offset value in a dark state, the optical block area is generally
implemented in a state in which the introduction of light is
blocked, As such, the pixels in the optical block area determine
the offset value in place of main pixels. Thus, when an asymmetry
occurs between the main pixels and the pixels in the optical block
area, the noise characteristic of the image sensor may be seriously
degraded.
[0011] Furthermore, the pixels in the optical block area receive
plasma damage after a back-end process, or particularly, after an
etching process. In order to cure the plasma damage, UV erase, that
is, UV anneal may be performed. At this time, the pixels in the
optical block area have a UV curing effect different from the main
pixels, because UV light is blocked during the curing process.
Thus, the dark current characteristic of the pixels in the optical
block area may differ, and a serious asymmetry may occur between
the pixels. As a result, the noise characteristic of the CMOS image
sensor may be degraded.
SUMMARY OF THE INVENTION
[0012] Accordingly, the embodiments of the present invention has
been made in an effort to resolve the concerns occurring in the
related art, and an object of the embodiment of the present
invention is to provide a CMOS image sensor including a filter
capable of equalizing a UV curing effect applied to pixels formed
in an optical block, area to a UV caring effect applied to main
pixels formed in an active pixel area.
[0013] According to an embodiment of the present invention, a CMOS
image sensor may include an active pixel structure suitable for
sensing light incident from outside and converting a sensed light
into an electrical signal, and an optical block structure suitable
for blocking a visible light and passing a UV light to check and
evaluate an electrical characteristic of the active pixel area. The
UV pass filter may include first and second insulation layers
comprising an insulator, and a metal layer formed between the first
and second insulation layers.
[0014] According to another embodiment of the present invention, a
CMOS image sensor may include an active pixel structure suitable
for sensing light incident from outside and converting a sensed
light into an electrical signal, and an optical block structure
suitable for blocking a visible light and passing a UV light to
check and evaluate an electrical characteristic of the active pixel
area. The UV pass filter may include a plurality of insulation
layers comprising an insulator, respectively, and a plurality of
metal layers formed between the first and second insulation layers,
respectively.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The above objects, and other features and advantages of the
present invention will become more apparent after a reading of the
following detailed description taken in conjunction with the
drawings, in which:
[0016] FIG. 1 is a block diagram illustrating a CMOS image sensor
in accordance with an embodiment of the present invention;
[0017] FIG. 2 is a plan view illustrating a pixel array of FIG.
1;
[0018] FIG. 3A is a side cross-sectional view illustrating an
embodiment of an optical block area illustrated in FIG. 2;
[0019] FIG. 3B is a side cross-sectional view illustrating an
embodiment of the optical block area illustrated in FIG. 2;
[0020] FIG. 4A is a plan view illustrating an embodiment of a metal
layer illustrated in FIG. 3A;
[0021] FIG. 4B is a plan view illustrating an embodiment of the
metal layer illustrated in FIG. 3A;
[0022] FIG. 4C is a plan view illustrating the embodiment of the
metal layer illustrated in FIG. 3A;
[0023] FIG. 4D is a plan view illustrating the embodiment of the
metal layer illustrated in FIG. 3A;
[0024] FIG. 5A is a plan view illustrating an embodiment of the
metal layer illustrated in FIG. 3A;
[0025] FIG. 5B is another plan view illustrating the embodiment of
the metal layer illustrated in FIG. 3A;
[0026] FIG. 5C is another plan view illustrating the embodiment of
the metal layer illustrated in FIG. 3A;
[0027] FIG. 5C is another plan view illustrating the embodiment of
the metal layer illustrated in FIG. 3A;
[0028] FIG. 6 illustrates a state in which UV light is applied to
the pixel array illustrated in FIG. 2; and
[0029] FIG. 7 is a graph illustrating the relationship between the
transmittance of UV light and the size of metal layers of FIGS. 4A
to 4D.
DETAILED DESCRIPTION
[0030] Reference will now be made in greater detail to a preferred
embodiment of the invention, an example of which is illustrated in
the accompanying drawings. Wherever possible, the same reference
numerals will be used throughout the drawings and the description
to refer to the same or like parts. It is also noted that in this
specification, "connected/coupled" refers to one component not only
directly coupling another component but also indirectly coupling
another component through an intermediate component. In addition, a
singular form may include a plural form as long as it is not
specifically mentioned in a sentence.
[0031] FIG. 1 is a block diagram of a CMOS image sensor in
accordance with an embodiment of the present invention. Referring
to FIG. 1, the CMOS image sensor 101 includes a pixel array 111, an
address decoder 121, a column buffer 131, an analog digital
converter (ADC) 141, and a controller 151 that are formed on a
semiconductor substrate 105.
[0032] The pixel array 111 includes a plurality of light sensing
elements, that is, a plurality of pixels. The light sensing element
may be implemented with a photo transistor, a photo diode, a photo
gate, a pinned photo diode, or the like. The light sensing elements
may be arranged in a matrix shape. The structure of the pixel array
will be described in detail with reference to FIG. 2.
[0033] The address decoder 121 is configured to decode an address
signal received from the controller 151 and designate a
corresponding light sensing element among the light sensing
elements included in the pixel array 111.
[0034] The column buffer 131 is configured to buffer and output
signals outputted by the column from the pixel array 111 according
to the control of a signal outputted from the controller 151.
[0035] The ADC 141 is configured to receive the signals outputted
from the column buffer 131, convert the received signals into
digital signals, and transmit the digital signals to the controller
151.
[0036] The controller 151 is configured to receive a signal
inputted from outside and control the address decoder 121, the
column buffer 131, and the ADC 141. Furthermore, the controller 151
is configured to receive a digital signal outputted from the ADC
141 and transmit the received signal to an external device, such as
a display to store or display an image.
[0037] FIG. 2 is a plan view of the pixel array 111 of FIG. 1.
Referring to FIG. 2, the pixel array 111 is divided into an active
pixel area 211 and an optical block area 221.
[0038] The active pixel area 211 is configured to sense light
incident from outside, convert the sensed light into an electrical
signal, and output the electrical signal to the column buffer 131.
The active pixel area 211 includes a plurality of main light
sensing elements, that is, main pixels arranged in a matrix
shape.
[0039] The optical block area 221 is arranged to surround the
active pixel area 211. The optical block area 221 is configured to
block light incident from outside and check and evaluate an
electrical characteristic of the active pixel area 211, that is, a
dark noise characteristic based on dark current. In other words,
the optical block area 221 may check and evaluate the dark noise
characteristic based on a dark current. Based on the evaluation
result, the optical block area 221 compensates for a current value
corresponding to the dark current of the main pixels in the active
pixel area 211, thereby preventing dark noise from occurring in the
image sensor. The horizontal and vertical sizes of the optical
block area 221 may be arbitrarily set according to process
parameters.
[0040] FIG. 3A is a side cross-sectional view of an embodiment of
the optical block area 221 illustrated in FIG. 2. Referring to FIG.
3A, the optical block area 221 includes a micro-lens 311, a color
filter 321, a UV pass filter 331, and a pixel layer 341. The
micro-lens 311, the color filter 321, and the UV pass filter 331
are sequentially stacked over the pixel-layer 341.
[0041] The micro-lens 311 may condense light incident from outside.
The color filter 321 may include a filter that passes visible light
from the light incident through the micro-lens 311. The color
filter 321 may be implemented with any one of a red filter that
passes only red light in the visible light, a green filter that
passes only green light in the visible light, and a blue filter
that passes only blue light in the visible light. If necessary, the
color filter 321 may include any one of a cyan filter, a yellow
filter, and a magenta filter.
[0042] The micro-lens 311 and the color filter 321 may not be
provided in the optical block area 221, depending on cases.
[0043] The UV pass filter 331 may block visible light front the
light, which is incident on the optical block area 221 from outside
and passes through the color filter 321, and may pass only UV
light. The UV pass filter 331 includes first and second insulation
layers 333 and 334.
[0044] The first and second insulation layers 333 and 334 are
formed over the pixel layer 341. The first and second insulation
layers 333 and 334 may protect optical black pixels formed over the
pixel layer 341 from the external environment. That is, the first
and second insulation layers 333 and 334 may prevent the optical
black pixels from being damaged by an external impact or physical
force. Each of the first and second insulation layers 333 and 334
may include an oxide layer including oxide (SiO.sub.2), a nitride
layer including nitride, or a composite layer including oxide and
nitride.
[0045] A metal layer 336 is formed between the first and second
insulation layers 333 and 334. The metal layer 336 may block
visible light, which is incident on the first and second insulation
layers 333 and 334 from, outside, from being transmitted to the
pixel layer 341. The metal layer 336 may include gold (Au), silver
(Ag), copper (Cu), or aluminum (Al). As the visible light incident
from outside is blocked from being transmitted to the pixel layer
341 by the metal layer 336, optical black pixels (not illustrated)
formed in the pixel layer 341 may generate optical black signals
having a dark level.
[0046] FIG. 3B is a side cross-sectional view of an embodiment of
the optical block area 221 illustrated in FIG. 2. Referring to FIG.
3B, the UV pass filter 332 includes a plurality of insulation
layers 333 to 335 and a plurality of metal layers 336 and 337. FIG.
3B illustrates only three insulation layers and two metal layers
for illustrative purpose. Between the insulation layers 333 to 335,
the metal layers 336 and 337 are respectively formed.
[0047] As the UV pass filter 332 includes the metal layers 336 and
337, the visible light blocking effect increases. In the present
embodiment, three or more metal layers may be provided. At this
time, the metal layers 336 and 337 may be arranged at even
intervals from each other. Each of the insulation layers 336 and
337 may include an oxide layer, a nitride layer, or a composite
layer of oxide and nitride. Each of the metal layers 336 and 337
may include Au, Ag, Cu, or Al.
[0048] FIG. 4A is a plan view of an embodiment of the metal layer
336 illustrated in FIG. 3A. Referring to FIG, 4A, the metal layer
336 includes a plurality of metal chips 421. The metal chips 421
may have a square plate shape and may be arranged in a matrix
shape. Through spaces 411 between the metal chips 421, UV light
incident on the optical block area 221 of FIG. 2 from outside may
reach the pixel layer 341 of FIG. 3A. The horizontal or vertical
size of the square metal chips 421 may be set to 80 nm, the space
411 between the metal chips 421 may be set to 30 nm, the thickness
of the metal chip 421 may be set to 1,400 .ANG., and the thickness
of the metal layer 336 may be set to 1,500 to 3,500 .ANG..
[0049] FIG. 4B is another plan view of an embodiment of the metal
layer 336 illustrated in FIG. 3A. Referring to FIG. 4B, the metal
layer 336 includes a plurality of metal chips 431. The metal chips
431 may have a rectangular plate shape, and may be arranged in a
matrix shape. Through the spaces 411 between metal chips 431, UV
light incident on the optical block area 221 of FIG. 2 from outside
may reach the pixel layer 341 of FIG. 3A. The horizontal length of
the rectangular metal chips 431 may be set to 80 nm, the space 411
between the metal chips 431 may be set to 30 nm, the thickness of
the metal chips 431 may be set to 1,400 .ANG., and the thickness of
the metal layer 336 may be set to 1,500 to 3,500 .ANG..
[0050] FIG. 4C is another plan view of an embodiment of the metal
layer 336 illustrated in FIG. 3A. Referring to FIG. 4C, the metal
layer 336 includes a plurality of metal chips 441. The metal chips
441 may have a circular plate shape and may be arranged in a matrix
shape. Through spaces 411 between the metal chips 441, UV light
incident on the optical block area 221 of FIG. 2 from outside may
reach the pixel layer 341 of FIG. 3A. The diameter of the circular
metal chip 441 may be set to 80 nm, the space 411 between the
circular metal chips 441 may be set to 30 nm, the thickness of the
metal chip 441 may be set to 1,400 .ANG., and the thickness of the
metal layer 336 may be set to 1,500 to 3,500 .ANG..
[0051] FIG. 4D is another plan view of an embodiment of the metal
layer 336 illustrated in FIG. 3A. Referring to FIG. 4D, the metal
layer 336 includes a plurality of metal chips 451. The metal chips
451 may have a regular-triangle plate shape and may be arranged in
a matrix shape. Referring to FIG. 4D, the metal chips 451 may be
arranged reversely to each other in a vertical direction. Through
spaces 411 between the metal chips 451, UV light incident on the
optical block area 221 of FIG. 2 from outside may reach the pixel
layer 341 of FIG. 3A. The height of the regular triangle of the
metal chip 451 may be set to 80 nm, the space 411 between the metal
chips 451 may be set to 30 nm, the thickness of the metal chip 451
may be set to 1,400 .ANG., and the thickness of the metal layer 336
may be set to 1,500 to 3,500 .ANG.. FIG. 4D illustrates the metal
chips that may have a regular-triangle plate shape. However, the
shape of the metal chips 451 is not limited to the
regular-triangle, and may be set to various other types of
triangles, such as an isosceles triangle and a right-angled
triangle.
[0052] The embodiments of FIGS. 4A to 4D may be applied in the same
manner to the metal layers 336 and 337 of FIG. 3B.
[0053] The metal chips 421, 431, 441, and 451 formed in the metal
layer 336 according to the embodiments of the present invention may
be formed in various shapes including the shapes of the embodiments
of FIGS. 4A to 4D.
[0054] FIG. 5A is a plan view of an embodiment of the metal layer
336 illustrated in FIG. 3A. Referring to FIG. 5A, the metal layer
336 may be formed in a net shape. That is, the metal layer 336 may
have a metal area 511 and a plurality of square holes 521 arranged
in a matrix shape. Through the square holes 521, UV light incident
on the optical block area 221 of FIG. 2 from outside may reach the
pixel layer 341 of FIG. 3A. The horizontal or vertical length of
the square hole 521 may be set to 80 nm, the pitch between the
square holes 521 may be set to 30 nm, and the thickness of the
metal layer 336 may be set to 1,400 .ANG..
[0055] FIG. 5B is another plan view of an embodiment of the metal
layer 336 illustrated in FIG. 3A. Referring to FIG. 5B, the metal
layer 336 may be formed in a net shape. That is, the metal layer
336 may have a metal area 511 and a plurality of rectangular holes
531 arranged in a. matrix shape. Through the rectangular holes 531,
UV light incident on the optical block area 221 of FIG. 2 from
outside may reach the pixel layer 341 of FIG. 3A. The horizontal
length of the rectangular hole 531 may be set to 80 nm, the pitch
between the rectangular holes 531 may be set to 30 nm, and the
thickness of the metal layer 336 may be set to 1,400 .ANG..
[0056] FIG. 5C is another plan view of an embodiment of the metal
layer 336 illustrated in FIG. 3A. Referring to FIG. 5C, the metal
layer 336 may be formed in a net shape. That is, the metal layer
336 may have a metal area 511 and a plurality of circular holes 541
arranged in a matrix shape. Through the circular holes 541, UV
light incident on the optical block area 221 of FIG. 2 from outside
may reach the pixel layer 341 of FIG. 3A. The diameter of the
circular hole 541 may be set to 80 nm, the pitch between the
circular holes 541 may be set to 30 nm, and the thickness of the
metal layer 336 may be set to 1,400 .ANG..
[0057] FIG. 50 is another plan view of an embodiment of the metal
layer 336 illustrated in FIG. 3A. Referring to FIG. 5D, the metal
layer 336 may be formed in a net shape. That is, the metal layer
336 may have a metal area 511 and a plurality of regular-triangle
holes 551 arranged in a matrix shape. As illustrated in FIG. 5D,
the regular-triangle holes 551 may be arranged reversely to each
other in a vertical direction. Through the regular-triangle holes
531, UV light incident on the optical block area 221 of FIG. 2
from, outside may reach the pixel layer 341 of FIG. 3A. The height
of the regular triangle of the hole 551 may be set to 80 nm, the
pitch between the regular-triangle holes 551 may be set to 30 nm,
and the thickness of the metal layer 336 may be set to 1,400 .ANG..
FIG. 5D illustrates the regular-triangle holes 551. However, the
holes 551 are not limited to the regular-triangle, but may be
formed in various triangle shapes including an isosceles triangle
and a right-angled triangle.
[0058] The embodiments of FIGS. 5A to 5D may be applied in the same
manner to the metal layers 336 and 337 illustrated in FIG. 3B.
[0059] The holes 521, 531, 541, and 551 formed in the metal layer
336 according to the embodiments of the present invention may be
applied to various shapes including the embodiments illustrated in
FIGS. 5A to 5D.
[0060] FIG. 6 illustrates a state in which UV light is applied to
the pixel array 111. Referring to FIG. 6, when UV light is applied
to the pixel array ill, the UV light reaches the pixel layer 351
through the micro-lens 311 and the color filter 321, which are
formed in the active pixel area 211. Similarly, the UV light
reaches the pixel layer 341 through the micro-lens 311, the color
filter 321, and the UV pass filters 331 and 332, which are formed
in the optical block area 221.
[0061] As the UV pass filters 331 and 332 are provided in the
optical block area 221 according to the embodiments of the present
invention, UV light applied to the optical block area 221 from
outside may reach the pixel layer 341 formed in the optical block
area 221 through the UV pass filters 331 and 332.
[0062] Specifically, in order to prevent plasma damage, which
occurs after a back-end process, or particularly, after an etching
process, a curing process using UV light may be performed. For
example, when UV light having a low energy of 4.3 to 8.8 eV may be
irradiated onto the pixel array 111 for tens of seconds, an anneal
effect may occur through injection of photo-electrons generated
from silicon. Furthermore, ions caused by plasma are erased or
detrapped in a state where they are trapped in an interface
state.
[0063] During the curing process using UV light, the optical black
pixels formed in the optical block area 221 have the same curing
effect as the main pixels formed in the active pixel area 211.
Thus, since the pixels in the optical block area 221 have the same
dark current characteristic as the pixels in the active pixel area
211, a serious asymmetry between the pixels disappears. As a
result, the image noise characteristic may be improved. That is,
the degradation of the image noise characteristic may be
prevented.
[0064] FIG. 7 is a graph illustrating the relationship between the
transmittance of UV light and the size of the metal layers 421 to
451 of FIGS. 4A to 4D. Referring to FIG. 7, it may be seen that the
transmittance increases with the decrease in the sixe of the metal
layers 421 to 451. That is, when the metal layers 421 to 451 have a
small size (711), the transmittance is higher than when the metal
layers 421 to 451 have a large size (721).
[0065] The embodiments of present invention may be applied to a
process of fabricating a device, which performs a curing process
using UV light, for example, a flash memory semiconductor
device.
[0066] According to the embodiments of the present invention, the
CMOS image sensor includes the UV pass filter formed in the optical
block area. That is, the optical block area blocks visible light
and passes UV light.
[0067] As the optical block area is formed to pass UV light, UV
light incident on the optical block area is irradiated onto the
pixels formed in the optical block area through the optical block
area, when the UV curing process is performed on the CMOS image
sensor. That is, the pixels formed in the optical block area may
have the same curing effect as the pixels formed in the active
pixel area through the UV curing process.
[0068] Thus, as the pixels in the optical block area have the same
dark current characteristic as the pixels in the active pixel area,
a serous asymmetry between the pixels disappears. As a result, the
image noise characteristic of the CMOS image sensor may be
improved.
[0069] Although a various embodiments of the present invention have
been described for illustrative purposes, those skilled in the art
will appreciate that various modifications, additions and
substitutions are possible, without departing from the scope and
the spirit of the invention as disclosed in the accompanying
claims.
* * * * *