1

CMOS IMAGE SENSOR

SEIED MANOOCHEHR HOSEINI

University of TEHRAN-IRAN

Supervisor : Dr. FAKHRAEI

In the Name of GOD advanced VLSI class presentation

2

Applications

3

The imaging system

[1]

4

FILL Factor

Optically Sensitive Area~30% of Total Pixel Area

[3]

5

Increase of FILL Factor

[2]

6

Microlens and Colour Filter

[3]

7

Colour Filter Response

[3]

8 [2]

2.0

3.0

4.05.0

1.0

10.0

’02 ’03 ’04 ’05 ’06 ’07 ’08

Pix

el p

itch

, u

m

5.6um (0.3M pixel)

3.8um (1.3M pixel)

2.8um (2M pixel)

< 1.8um

2.2um (7.2M pixel)

< 1.5um

Year

This Work

CMOS Image Sensor Trend

9

A typical 3T pixel

10

4T Architecture

11

4T Shared Pixel Architecture

12

Pixel-level charge summation for sub-sampling.

[2]

13

VDD

RGTG1

SELTG2

TG3

TG4

R11

G21

R31

G41

APS_OUT1

Sum of signal =

Sum of noise = N2

N2

NNSNR log1032log20

By pixel summation SNR increase by 3dB

[2]

14

R Gr R Gr

Gb B Gb B

Gb B Gb B

R Gr R Gr

Ra

mp

Ge

n. Savg

Savg

Average signal =

Average noise =

NNSNR log1032log20

2

N

N

By clumn wise averanging SNR increase by 3dB

[2]

15

Old and new GNOX process; improvement of random noise by reducing the trap effect on SF transistor.

[2[,]4]

16

Increase light gathering power by 20% pixel height shrink

[2]

17

SNR Increase With New Sub-Sampling

[2]

18

Implementation of average filter by MATLAB software

Original image

Use average filtering

19

Implementation of average filter by MATLAB software

Original image

Use average filtering

20

4-shared pixel architecture High fill factor (57%)

with SNR max of 41dB under the full-resolution operation. Pixel level charge summation Increase 6dB in SNR Noise reduction technology SF trap treatment to reduce 1/f noise

21

REFRENSES

[1 ]A. El Gamal and H. Eltoukhy, “CMOS Image Sensor,” IEEE Circuit and Devices Magazine, vol. 21, no. 3, pp. 6-20, May-June, 2005.

[2 ]Young Chan Kim, Yi Tae Kim, Sung Ho Choi, Hae Kyung Kong, Sung In Hwang, Ju Hyun Ko, Bum Suk Kim, Tetsuo Asaba, Su Hun Lim, June Soo Hahn, Joon Hyuk Im, Tae Seok Oh, Duk Min Yi, Jong Moon Lee, Woon Phil Yang, Jung Chak Ahn, Eun Seung Jung, Yong Hee Lee .

Samsung Electronics, Kiheung, Korea“1/2-inch 7.2MPixel CMOS Image Sensor with 2.25µm Pixels Using 4-Shared Pixel Structure for

Pixel-Level Summation .” ISSCC 2005.[3 ]CMOS Image Sensors : Lenses and Filters on Silicon // Lindsay Grant, ST Microelectronics

Robert Henderson, University of Edinburgh [4 ]J.Y. Kim, et al., “Characterization and Improvement of Random Noise in 1/3.2” UXGA CMOS

Image Sensor with 2.8µm Pixel using 0.13µm Technology,” IEEE Charge-Coupled Devices and Advanced Image Sensors, pp. 149-152, 2005.