Image Processing Reference
In-Depth Information
Metal
wiring
layers
Silicon layer
thickness:
∼3 μm
PD
PD
PD
Metal
wiring
layers
PD
PD
PD
Silicon
substrate
thickness:
600-800 μm
Supporting substrate
(a)
(b)
FIGURE 5.67
Schematic diagram of a simplified cross-sectional view of (a) a surface illustrated sensor (FSI); (b) a backside
illuminated sensor (BSI).
Support substrate
Support substrate
Metal
wiring
layers
PD
PD
PD
PD
PD
PD
PD
PD
PD
Silicon
substrate
ickness: ∼3 μm
(a)
(b)
(c)
OCL
p
+
layer
Light shield film
Color filter
PD
PD
PD
PD
PD
PD
Support substrate
Support substrate
(d)
(e)
FIGURE 5.68
Conceptual diagram of the fabrication process of a BSI: (a) formation of circuitry and wiring on a silicon wafer;
(b) attachment of support substrate; (c) wafer thinning; (d) backside passivation and light shield formation;
(e) color filter and OCL formation.
shown in Figure 5.68b-d were newly added for BSIs. Image sensors are a kind of LSI and
have been naturally manufactured by technology cultivated in the LSI industry including
the fabrication process. Technologies inherent in image sensors hitherto include intrinsic
gettering (IG),
56
IG-epi wafers,
57
buried/pinned PDs, color filters, OCLs, glass-sealed pack-
ages, and so on. BSIs have a greatly expanded technological area endemic to image sensors
quantitatively and qualitatively. While newly added processes increase the manufacturing
cost, they should bring about benefits that outweigh this cost increase for the industry.
Figures 5.67 and 5.68 show conceptual drawings. High optical performances, such as
sensitivity, are expected of BSIs, especially in smaller size pixels.
