What is the 40nm BSI CMOS Image Sensor process flow?

The 40nm BSI (Backside Illuminated) CMOS Image Sensor process flow is a specialized semiconductor manufacturing sequence for high-performance image sensors. Unlike traditional front-side illuminated (FSI) architecture, BSI places the photodiode beneath the metal interconnect layers and receives light from the wafer backside, dramatically improving quantum efficiency and low-light performance. This flow contains 417 process steps and is entirely free to access.

What is the difference between BSI and FSI image sensors?

In FSI architecture, incident light must pass through the metal interconnect layers to reach the photodiode — metal lines block and reflect some light, reducing quantum efficiency. BSI flips the wafer so light enters directly from the backside into the photodiode, bypassing the metal stack. This gives BSI sensors significantly higher sensitivity at the same pixel size, making them ideal for smartphone cameras and low-light applications.

What is the role of Deep Trench Isolation (DTI) in the 40nm CIS flow?

Deep Trench Isolation (DTI) creates physical and optical barriers between adjacent pixel photodiodes in BSI CIS. The trenches are filled with low-refractive-index material, preventing photo-generated carriers from diffusing into neighboring pixels (electrical crosstalk) and blocking oblique light from crossing pixel boundaries (optical crosstalk). This is critical for maintaining image quality as pixel pitch shrinks.

What is the role of Color Filter Array (CFA) and microlens in CIS?

The Color Filter Array sits above each pixel, arranging red, green, and blue filters in a Bayer pattern (RGGB) so each pixel captures only one color. The microlens array sits above the CFA, focusing incident light onto each pixel's active area to improve light collection efficiency. In BSI architecture, the shorter optical path and absence of metal obstruction simplify CFA and microlens alignment and increase the fill factor.

What are the key modules in the 40nm CIS process flow?

Key modules include: STI (Shallow Trench Isolation), Well formation, Gate, PD (Photodiode formation), F-DTI (Frontside Deep Trench Isolation), PMD/Contact, multi-level metal interconnect (MET0-MET6), DBI (Direct Bond Interconnect — wafer bonding), backside thinning (THIN), backside passivation (BKPAS), LS Grid (Light Shield Grid), CFA (Color Filter Array), microlens (UOCL), and Bondpad. The flow spans 42 modules and 417 process steps.

40nm BSI CMOS Image Sensor - 40nm 工艺流程

优先加工绿色层可建立 CFA 结构的基准形貌，并提供物理边界，从而有助于为后续的红色和蓝色滤光片工艺最小化因对准偏差产生的串扰 [P2]。

在采用经典 Bayer 排列的互补金属氧化物半导体（CMOS）图像传感器中，绿色滤色阵列（CFA）通常最先进行加工，因为绿色像素占成像阵列的 50%，且在人类视觉感知中主导亮度信号 [P1, A1]。在对遮光栅格进行光刻前清洗后，涂覆绿色滤色树脂以填充预定义的栅格腔体 （工程实践）。优先加工绿色层可建立 CFA 结构的基准形貌，并提供物理边界，从而有助于为后续的红色和蓝色滤光片工艺最小化因对准偏差产生的串扰 [P2]。

**[高] 光学串扰与光谱偏移…

优先加工绿色层可建立 CFA 结构的基准形貌，并提供物理边界，从而有助于为后续的红色和蓝色滤光片工艺最小化因对准偏差产生的串扰 [P2]。

**[高] 光学串扰与光谱偏移…

40nm BSI CMOS Image Sensor登录后免费

工艺截面图

本步要点

原理展开

风险与挑战

40nm BSI CMOS Image Sensor登录后免费

工艺截面图

本步要点

原理展开

风险与挑战