Improvement of Optical Efficiency and Crosstalk with A Trench Color Filter Scheme

• Main Authors: Lin, Che-Hung, 林哲宏
• Other Authors: Pan, Fu-Ming
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/snq97j

碩士 === 國立交通大學 === 工學院半導體材料與製程設備學程 === 106 === CMOS image sensors (CIS) offer the advantages of lower cost, lowe power consumption, portability and system on chip (SoC) characteristics than Charge Coupled Device (CCD). In the past few years, CIS has been widely applied to consumer products, security cameras, automotive and medical systems, Virtual Reality (VR) and mobile phones.Because of the strong demand for a smaller chip size and a higher resolution. To obtain a higher resolution at the same sensor size, the pixel size is needed to be shrunk. However, the scaling-down has two side effects: first, the amount of the incident light incident on each photodiode decreases, leading to a lower optical efficiency. Second, The optical crosstalk becomes more serious. In this thesis, we proposed an embeded trenched color filter structure to improve the optical efficiency and crosstalk. On the basis of the Snell’s law, we optimized the refractive index difference between the color filter and the surrounding dielectric films so that total internal reflection (TIR) of the incident light occurs, suppressing the optical crosstalk and increasing the optical efficiency. The Finite-Difference-Time-Domain (FDTD) software was used to simulate the optical efficiency and crosstalk in three filter structures: conventional, etched cavity and the embeded trenched structures to predict the performance of the image sensors. We then fabricated CIS sensors with the three structures at 0.11μm scale and measured the optical and crosstalk properties. The study shows that the embeded trenched structure outperforms the other two structures interms of the optical efficiency and the crosstalk. Compared with the conventional structure, the embedded trenched structure increases the optical efficiency by 35-39% and reduces the crosstalk by 0.6-0.7%. The embeded trenched structure has a higher optical efficiency that the etched cavity structure by 6-14% while is with a comparable crosstalk with the cavity one.