U.S. patent application number 11/636349 was filed with the patent office on 2007-04-12 for image sensing device including image sensor with high dynamic range.
This patent application is currently assigned to C'EST IMAGE, Inc.. Invention is credited to Seung Hyun Cha, Yong Ahn Ha, Heung Sik Kim, Jin Heon Kim, Woo Hyun Kwon, Hak Dae Lee, Seung Chul Lee, Tae Sun Shin, Jong Sun Won, Ui Chol Yi.
Application Number | 20070080283 11/636349 |
Document ID | / |
Family ID | 36315345 |
Filed Date | 2007-04-12 |
United States Patent
Application |
20070080283 |
Kind Code |
A1 |
Kim; Heung Sik ; et
al. |
April 12, 2007 |
Image sensing device including image sensor with high dynamic
range
Abstract
An image sensor with a high dynamic range is provided. The image
sensor includes a semiconductor substrate, a plurality of
light-receiving elements formed on the semiconductor substrate, and
light-shield films formed on upper ends of some of the
light-receiving elements to partially block light incident upon
each of the some light-receiving elements. Hence, an image sensing
device including the image sensor can detect an accurate image
regardless of whether the environment is bright or dark.
Inventors: |
Kim; Heung Sik; (Seoul,
KR) ; Ha; Yong Ahn; (Daejeon-city, KR) ; Yi;
Ui Chol; (San Francisco, CA) ; Kim; Jin Heon;
(Seoul, KR) ; Kwon; Woo Hyun; (Seongnam-city,
KR) ; Won; Jong Sun; (Gunpo-city, KR) ; Lee;
Hak Dae; (Seoul, KR) ; Cha; Seung Hyun;
(Seoul, KR) ; Lee; Seung Chul; (Incheon-city,
KR) ; Shin; Tae Sun; (Seoul, KR) |
Correspondence
Address: |
THELEN REID & PRIEST, LLP
P. O. BOX 640640
SAN JOSE
CA
95164-0640
US
|
Assignee: |
C'EST IMAGE, Inc.
Seoul
KR
|
Family ID: |
36315345 |
Appl. No.: |
11/636349 |
Filed: |
December 7, 2006 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11177527 |
Jul 7, 2005 |
7154076 |
|
|
11636349 |
Dec 7, 2006 |
|
|
|
Current U.S.
Class: |
250/208.1 ;
257/E27.151; 257/E31.032; 257/E31.122 |
Current CPC
Class: |
H01L 27/14623 20130101;
H01L 31/02164 20130101; H01L 31/0352 20130101; H01L 27/14806
20130101 |
Class at
Publication: |
250/208.1 |
International
Class: |
H01L 27/00 20060101
H01L027/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 5, 2004 |
KR |
10-2004-0089774 |
Dec 24, 2004 |
KR |
10-2004-0112146 |
Claims
1. An image sensor comprising: a semiconductor substrate; a
plurality of light-receiving elements formed on the semiconductor
substrate; and light-shield films formed on upper ends of some of
the light-receiving elements to partially block light incident upon
each of the some light-receiving elements.
2. The image sensor of claim 1, wherein the light-receiving
elements include photo diodes that receive light.
3. The image sensor of claim 1, wherein lines of light-receiving
elements covered with the light-shield films and lines of
light-receiving elements on which no light-shield films are formed
are arranged in such a way that one line of light-receiving
elements covered with the light-shield film alternates with one
line of light-receiving elements on which no light-shield films are
formed.
4. The image sensor of claim 1, further comprising: a plurality of
first vertical transmission electrodes formed on the semiconductor
substrate, transmitting an electrical signal output from the
light-receiving elements covered with the light-shield films to the
outside; a plurality of second vertical transmission electrodes
formed on the semiconductor substrate, transmitting an electrical
signal output from the light-receiving elements having no
light-shield films thereon to the outside; a plurality of vertical
charge transmission units formed on the semiconductor substrate,
electrically connected to the light-receiving elements, and
transmitting charges received from the light-receiving elements; at
least one horizontal charge transmission unit formed on the
semiconductor substrate, electrically connected to the vertical
charge transmission units, and receiving charges received from the
vertical charge transmission units; and at least one horizontal
transmission electrode formed on the semiconductor substrate,
electrically connected to the horizontal charge transmission unit,
and transmitting an electrical signal received from the horizontal
charge transmission unit to the outside.
5. An image sensing device comprising: an image sensor comprising a
semiconductor substrate, a plurality of light-receiving elements
formed on the semiconductor substrate, and light-shield films
formed on upper ends of some of the light-receiving elements to
partially block light incident upon each of the some
light-receiving elements; a first analog-to-digital converter
converting an electrical signal received from the light-receiving
elements covered with the light-shield films into a digital signal;
a second analog-to-digital converter converting an electrical
signal received from the light-receiving elements having no
light-shield films thereon to a digital signal; a comparator
comparing values of the digital signals output from the first and
second analog-to-digital converters with a value of a reference
signal and detecting and outputting a signal greater than the
reference signal value and a signal smaller than the reference
signal value; and a digital-to-analog converter converting the
signals output by the comparator into analog signals.
6. The image sensing device of claim 5, further comprising: a first
amplification unit amplifying the electrical signal received from
the light-receiving elements covered with the light-shield films
and outputting the amplified signal to the first analog-to-digital
converter; and a second amplification unit amplifying the
electrical signal received from the light-receiving elements having
no light-shield films thereon and outputting the amplified signal
to the second analog-to-digital converter.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] The present application is a divisional application of U.S.
patent application Ser. No. 11/177,527, filed Jul. 7, 2005, which
in turn claims the benefit of priority based on Korean Patent
Application Nos. 10-2004-0089774, filed on Nov. 5, 2004, and
10-2004-0112146, filed on Dec. 24, 2004 in the Korean Intellectual
Property Office, the disclosures of which are incorporated herein
in their entirety by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an image sensing device,
and more particularly, to a pixel designed to increase a speed at
which charges are transmitted, an image sensor with a wide extended
dynamic range, and an image sensing device including the image
sensor.
[0004] 2. Description of the Related Art
[0005] An image sensor includes a plurality of pixels that receive
external light and produce electric charges, and converts an
optical image into an electrical signal.
[0006] FIG. 1 illustrates a semiconductor device 101 in which
pixels of a conventional charge coupling device (CCD) type imaging
device are formed. Referring to FIG. 1, the semiconductor device
101 includes a plurality of pixels 111, a plurality of vertical
transmission lines 161, and a single horizontal transmission line
171.
[0007] Each of the pixels 111 includes a photo diode area 121, a
transmission gate area 131 formed on one side of the photo diode
area 121, a vertical transmission area 141 formed adjacent to the
photo diode area 121, and a channel stop area 151 formed on the
three remaining sides of the photo diode area 121.
[0008] The vertical transmission lines 161 each include vertical
transmission areas 141 and are all connected to the horizontal
transmission line 171.
[0009] In the convention pixel 111, the photo diode area 121 has a
rectangular shape, and the transmission gate area 131 is formed on
a portion of a side of the photo diode area 121. Because the shape
of the photo diode area 121 is rectangular, charges generated in
the photo diode area 121 are collected at corners of the
rectangular photo diode area 121. The collection of the charges at
the corners of the rectangular photo diode area 121 delays
transmission of the charges generated in the pixels 111 to the
horizontal transmission line 171 via the vertical transmission
lines 161. This delayed transmission causes a reduction of the
speed of imaging by an imaging device.
[0010] In addition, since light-receiving elements included in a
conventional image sensor receive identical amounts of light, it is
difficult for the conventional image sensor to have a high dynamic
range. In a current situation, an image sensing device must use two
or more image sensors to obtain a high dynamic range. However, the
use of two or more image sensors increases the costs for
manufacturing the image sensing device, resulting in a high-priced
image sensing device.
SUMMARY OF THE INVENTION
[0011] The present invention provides a pixel structure that
improves a transmission speed.
[0012] The present invention also provides an image sensor that can
provide a high dynamic range at a low cost and an image sensing
device including the image sensor.
[0013] According to an aspect of the present invention, there is
provided a pixel of a charge coupling device (CCD) type imaging
apparatus formed on a semiconductor device, the pixel including: a
photo diode area formed in an oval shape, generating charges when
external light is incident upon the photo diode area; a channel
stop area formed in a semi-oval shape along one side of the photo
diode area, blocking external charges from flowing into the photo
diode area and internal charges from flowing out of the photo diode
area; a transmission gate area curved along the other side of the
photo diode area, controlling a transmission of the internal
charges generated in the photo diode area to the outside of the
transmission gate area; and a vertical transmission area formed
adjacent to the transmission gate area, transmitting charges
received from the transmission gate area to the outside of the
vertical transmission area.
[0014] A polysilicon layer may be formed in the transmission gate
area, and when a control signal is applied to the polysilicon
layer, the transmission gate area may be activated to transmit
charges generated in the photo diode area to the vertical
transmission area.
[0015] A polysilicon layer may be formed in the vertical
transmission area, and when a control signal is applied to the
polysilicon layer, the vertical transmission area may be activated
to transmit the charges received from the transmission gate area to
the outside of the vertical transmission area.
[0016] According to another aspect of the present invention, there
is provided an image sensor including: a semiconductor substrate; a
plurality of light-receiving elements formed on the semiconductor
substrate; and light-shield films formed on upper ends of some of
the light-receiving elements to partially block light incident upon
each of the some light-receiving elements.
[0017] The light-receiving elements may include photo diodes that
receive light.
[0018] Lines of light-receiving elements covered with the
light-shield films and lines of light-receiving elements on which
no light-shield films are formed may be arranged in such a way that
one line of light-receiving elements covered with the light-shield
film alternates with one line of light-receiving elements on which
no light-shield films are formed.
[0019] The image sensor may further include: a plurality of first
vertical transmission electrodes formed on the semiconductor
substrate, transmitting an electrical signal output from the
light-receiving elements covered with the light-shield films to the
outside; a plurality of second vertical transmission electrodes
formed on the semiconductor substrate, transmitting an electrical
signal output from the light-receiving elements having no
light-shield films thereon to the outside; a plurality of vertical
charge transmission units formed on the semiconductor substrate,
electrically connected to the light-receiving elements, and
transmitting charges received from the light-receiving elements; at
least one horizontal charge transmission unit formed on the
semiconductor substrate, electrically connected to the vertical
charge transmission units, and receiving charges received from the
vertical charge transmission units; and at least one horizontal
transmission electrode formed on the semiconductor substrate,
electrically connected to the horizontal charge transmission unit,
and transmitting an electrical signal received from the horizontal
charge transmission unit to the outside.
[0020] According to another aspect of the present invention, there
is provided an image sensing device including: the above-described
image sensor; a first analog-to-digital converter converting an
electrical signal received from the light-receiving elements
covered with the light-shield films into a digital signal; a second
analog-to-digital converter converting an electrical signal
received from the light-receiving elements having no light-shield
films thereon to a digital signal; a comparator comparing values of
the digital signals output from the first and second
analog-to-digital converters with a value of a reference signal and
detecting and outputting a signal greater than the reference signal
value and a signal smaller than the reference signal value; and a
digital-to-analog converter converting the signals output by the
comparator into analog signals.
[0021] The image sensing device may further include: a first
amplification unit amplifying the electrical signal received from
the light-receiving elements covered with the light-shield films
and outputting the amplified signal to the first analog-to-digital
converter; and a second amplification unit amplifying the
electrical signal received from the light-receiving elements having
no light-shield films thereon and outputting the amplified signal
to the second analog-to-digital converter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The above and other features and advantages of the present
invention will become more apparent by describing in detail
exemplary embodiments thereof with reference to the attached
drawings in which:
[0023] FIG. 1 illustrates a semiconductor device in which pixels of
a conventional charge coupling device (CCD) type imaging device are
formed;
[0024] FIG. 2 illustrates a structure of a pixel of a CCD type
imaging device according to an embodiment of the present
invention;
[0025] FIG. 3 is a cross-sectional view of the pixel of FIG. 2
taken along line 3-3;
[0026] FIG. 4 schematically illustrates a structure of a
semiconductor device including a plurality of pixels shown in FIG.
3;
[0027] FIG. 5 is a plan view conceptually illustrating an image
sensor according to another embodiment of the present invention;
and
[0028] FIG. 6 is a block diagram of an image sensing system
including the image sensor of FIG. 5.
DETAILED DESCRIPTION OF THE INVENTION
[0029] Hereinafter, the present invention will be described in
detail by explaining preferred embodiments of the invention with
reference to the attached drawings. Like reference numerals in the
drawings denote like elements.
[0030] FIG. 2 illustrates a structure of a pixel 201 of a charge
coupling device (CCD) type imaging device according to an
embodiment of the present invention. Referring to FIG. 2, the pixel
201 includes a photo diode area 211, a transmission gate area 221,
a vertical transmission area 231, and a channel stop area 241.
[0031] The photo diode area 211 produces charges when receiving
external light and accumulates the generated charges. The photo
diode area 211 has an oval shape.
[0032] The transmission gate area 221 is formed on one side of the
photo diode area 211. For example, the transmission gate area 221
is formed along one side of the photo diode area 211 to have an
oval shape. The transmission gate area 221 controls a transmission
of charges generated in the photo diode area 211 to the vertical
transmission area 231.
[0033] The vertical transmission area 231 is formed adjacent to the
transmission gate area 221. More specifically, the vertical
transmission area 231 is formed along one side of the transmission
gate area 221 to have an oval shape. The vertical transmission area
231 transmits charges received via the transmission gate area 221
or received from an external source to a horizontal transmission
line (not shown).
[0034] The channel stop area 241 is formed along the other side of
the photo diode area 211 to be curved. The channel stop area 241
stops external charges from flowing into the photo diode area 211
and charges generated in the photo diode area 211 from flowing out
of the photo diode area 211.
[0035] FIG. 3 is a cross-sectional view of the pixel 201 taken
along line 3-3. Referring to FIG. 3, a P-well region 305 is formed
on a semiconductor substrate 301. An N-type region 311 for forming
the photo diode area 211, a P-type region 321 for forming the
transmission gate area 221, an N-type region 331 for forming the
vertical transmission area 231, and a P-type region 341 for forming
the channel stop area 241 are formed in the P well region 305. A
silicon oxide layer 351 is formed to protect the regions 315, 321,
331, and 341.
[0036] More specifically, the semiconductor substrate 301 is formed
of N-type semiconductor.
[0037] The N-type region 311 is an N-type charge-accumulated region
that is formed in the photo diode area 211 and forms a PN junction
with the P well region 305, thereby accumulating charges generated
by incident light. The N-type region 311 is covered with a P-type
surface layer 315 with a high acceptor concentration to prevent an
increase of dark current produced by a depletion of an interface
between the photo diode area 211 and the silicon oxide layer
351.
[0038] The transmission gate area 221 is formed between the photo
diode area 211 and the vertical transmission area 231. The
transmission gate area 221 includes the P-type region 321, which is
a voltage control area that is doped with P-type boron and controls
a threshold voltage. A first polysilicon layer 361 is formed over
the P-type region 321.
[0039] The N-type region 331 is formed in the vertical transmission
area 231. The first polysilicon layer 361 and a second polysilicon
layer 371 are formed over the N-type region 331.
[0040] The channel stop area 241 is formed opposite to the
transmission gate area 221 and includes the P-type region 341. The
P-type region 341 is doped with high P-type boron.
[0041] When light is incident upon the photo diode area 211,
charges are generated and accumulated in the N-type region 311. At
this time, when a control signal is applied to the first
polysilicon layer 361, the P-type region 321 is activated to
thereby form a transmission channel. Accordingly, the charges
accumulated in the N-type region 311 are transmitted to the N-type
region 331 via the transmission channel. Thereafter, when the
application of the control signal is stopped, the P-type region 321
is inactivated, and so the transmission channel disappears. The
N-type region 311 produces and accumulates charges corresponding to
a next period.
[0042] The charges transmitted to the vertical transmission area
231 move parallel to each other in a vertical direction to be
transmitted to a horizontal transmission line (not shown). The
charges that have reached the horizontal transmission line are
transmitted horizontally until next charges are received from the
vertical transmission area 231. The horizontally transmitted
charges undergo an amplification process and are discharged to the
outside.
[0043] FIG. 4 schematically illustrates a structure of a
semiconductor device 401 including a plurality of pixels shown in
FIG. 2. Referring to FIG. 4, the semiconductor device 401 includes
a plurality of pixels 201, a plurality of vertical transmission
lines 411, and a single (or two) horizontal transmission line 421.
The pixels 201 are consecutively aligned between two vertical
transmission lines 411 to have a honeycomb configuration, thereby
increasing the integration.
[0044] FIG. 5 is a plan view conceptually illustrating an image
sensor 501 according to another embodiment of the present
invention. Referring to FIG. 5, the image sensor 501 includes a
semiconductor substrate 511, light-receiving elements 521 through
524, a plurality of vertical charge transmission units 531 through
534, horizontal charge transmission units 541 and 542, a plurality
of first vertical transmission electrodes 551, a plurality of
second vertical transmission electrodes 552, and horizontal
transmission electrodes 561 through 564. The light-receiving
elements 521 through 524, the vertical charge transmission units
531 through 534, the horizontal charge transmission units 541 and
542, the first vertical transmission electrodes 551, the second
vertical transmission electrodes 552, and the horizontal
transmission electrodes 561 through 564 are installed on the
semiconductor substrate 511.
[0045] The light-receiving elements 521 through 524 receive
external light, convert the light into an electrical signal, and
output the electrical signal. Each of the light-receiving elements
521 through 524 includes a photo diode that receives light. The
light-receiving elements 521 through 524 are divided into two types
of: light-receiving elements 522 and 524 on which light-shield
films 571 are mounted, respectively; and light-receiving elements
521 and 523 on which no light-shield films are mounted. The
light-receiving elements 522 and 524, respectively having the
light-shield films 571 and 572 thereon, receive a small amount of
light from an external source. The light-receiving elements 521 and
523, having no light-shield films thereon, receive a large amount
of light from the external source.
[0046] As shown in FIG. 5, the light-shield film 571 may be formed
with a size that can cover only a half of each of the
light-receiving elements 522 and 524. However, the light-shield
film 571 may have various sizes according to the purpose. For
example, the light-shield film 571 may have a size that covers only
1/3 of the area of each of the light-receiving elements 522 and
524. Alternatively, the light-shield film 571 may have a size that
covers only 114 of the area of each of the light-receiving elements
522 and 524. By including the light-receiving elements 522 and 524
on which the light-shield films 571 of different sizes and
selectively controlling operations of the light-receiving elements
522 and 524, the image sensor 501 can detect various images with
various characteristics and also variously analyze a single
image.
[0047] Lines 582 and 584, which include the light-receiving
elements 522 and the light-receiving elements 524, respectively,
having the light-shield film 571 thereon, and lines 581 and 583,
which include the light-receiving elements 521 and the
light-receiving elements 523, respectively, having no light-shield
film 571 thereon, are arranged on the semiconductor substrate 511
in such a way that a line covered with a light-shield film
alternates with a line having no light-shield film thereon. Hence,
the image sensor 501 can sense two types of optical images under an
identical condition when receiving light associated with an
external image.
[0048] The first vertical transmission electrodes 551 are
electrically connected to the light-receiving elements 522 and 524
on which the light-shield films 571 are formed. When being
connected to an external system (not shown), the first vertical
transmission electrodes 551 receive an electrical signal output
from the light-receiving elements 522 and 524 having the
light-shield film 571 thereon and transmit the electrical signal to
the external system.
[0049] The second vertical transmission electrodes 552 are
electrically connected to the light-receiving elements 521 and 523
on which no light-shield films are formed. When being connected to
the external system, the second vertical transmission electrodes
552 receive an electrical signal output from the light-receiving
elements 521 and 523 having no light-shield films thereon and
transmit the electrical signal to the external system.
[0050] The vertical charge transmission units 532 and 534 are
electrically connected to the light-receiving elements 522 and 524
having the light-shield film 571 thereon and transmits charges
received from the light-receiving elements 522 and 524 to the
horizontal charge transmission units 541 and 542.
[0051] The vertical charge transmission units 531 and 533 are
electrically connected to the light-receiving elements 521 and 523
having no light-shield films thereon and transmits charges received
from the light-receiving elements 521 and 523 to the horizontal
charge transmission units 541 and 542.
[0052] The horizontal charge transmission units 541 and 542 are
electrically connected to the vertical charge transmission units
531 through 534 and transmit the charges received from the vertical
charge transmission units 531 through 534 to the horizontal
transmission electrodes 561 through 564. Although the horizontal
charge transmission units 541 and 542 are formed on a top side and
a bottom side, respectively, of the vertical charge transmission
units 531 through 534 in FIG. 5, a single horizontal charge
transmission unit may be formed on the bottom side of the vertical
charge transmission units 531 through 534.
[0053] The horizontal transmission electrodes 561 through 564 are
electrically connected to the horizontal charge transmission units
541 and 542. When being connected to the external system, the
horizontal transmission electrodes 561 through 564 receive
electrical signals from the horizontal charge transmission units
541 and 542 and transmit the electrical signals to the external
system. The horizontal transmission electrodes 561 through 564 may
be connected to either only one sides or both sides of the
horizontal charge transmission units 541 and 542.
[0054] FIG. 6 is a block diagram of an image sensing system 601
according to an embodiment of the present invention. Referring to
FIG. 6, the image sensing system 601 includes the image sensor 50,
first and second amplification units 611 and 612, first and second
analog-to-digital converters (ADCs) 621 and 622, a comparator 631,
and a digital-to-analog converter (DAC) 641.
[0055] The image sensor 501 has already been described in detail
with reference to FIG. 5.
[0056] The first amplification unit 611 is electrically connected
to the first vertical transmission electrodes 551 of FIG. 5.
Because an electrical signal output from the first vertical
transmission electrodes 551 of FIG. 5 is very weak, the first
amplification unit 611 amplifies the electrical signal. Because the
number of first vertical transmission electrodes 551 is plural, the
first amplification unit 611 includes a plurality of amplifiers
connected to the plurality of first vertical transmission
electrodes 551 of FIG. 5.
[0057] The second amplification unit 612 is electrically connected
to the second vertical transmission electrodes 552 of FIG. 5.
Because an electrical signal output from the second vertical
transmission electrodes 552 of FIG. 5 is very weak, the second
amplification unit 612 amplifies the electrical signal. Because the
number of second vertical transmission electrodes 552 is plural,
the second amplification unit 612 includes a plurality of
amplifiers connected to the plurality of second vertical
transmission electrodes 552 of FIG. 5.
[0058] The first ADC 621 is connected to the first amplification
unit 611 and converts a signal output from the first amplification
unit 611 into a digital signal.
[0059] The second ADC 622 is connected to the second amplification
unit 612 and converts a signal output from the first amplification
unit 612 into a digital signal.
[0060] The comparator 631 compares the digital signals output from
the first and second ADCs 621 and 622 with a reference signal value
and detects a signal greater than the reference signal value and a
signal smaller than the reference signal value.
[0061] The DAC 614 converts the signals output from the comparator
63 into analog signals.
[0062] As such, the image sensing system 601 detects both a signal
with a high light amount and a signal with a low light amount from
the single image sensor 501, thus capturing an accurate image
regardless of a bright environment or a dark environment. Also, the
costs for manufacturing the image sensing system 601 can be
reduced.
[0063] As described above, the oval shape of the pixel 201 prevents
charges from being collected at one place within the photo diode
area 211, thus increasing a speed at which the charges generated in
the photo diode area 211 are transmitted to the vertical
transmission area 231 via the transmission gate area 221.
Consequently, an image sensing speed of a CCD type imaging device
increases.
[0064] In addition, because the image sensor 501 includes the
light-receiving elements 522 and 524 covered with the light-shield
films 571 and the light-receiving elements 521 and 523 having no
light-shield films thereon formed on the semiconductor substrate
511, the image sensing device 601 can detect an accurate image
regardless of whether the environment is bright or dark.
Furthermore, the costs for manufacturing the image sensing system
601 can be reduced.
[0065] While the present invention has been particularly shown and
described with reference to exemplary embodiments thereof, it will
be understood by those of ordinary skill in the art that various
changes in form and details may be made therein without departing
from the spirit and scope of the present invention as defined by
the following claims.
* * * * *