Dyed red, green, and blue photoresist for manufacture of high-resolution color filter arrays for image sensors

Abstract

We are developing a set of dyed red, green, and blue color filter coatings for the fabrication of high resolution CCD and CMOS image sensor arrays. The resists contain photosensitive polymer binders and various curing agents, soluble organic dyes, and solvents. The new dyed photoresists are sensitive to i-line radiation, primarily at 365 nm, and are negative-working, requiring less than 500 mJ of exposure energy for patterning. The coatings are developed in standard Tetramethylammonium Hydroxide (TMAH) developers. Many dyes were examined in order to achieve the desired spectral properties as well as the meet the solvent solubility and thermal stability requirements. Computer modeling was utilized to determine the correct proportions of dye(s) in each resist, after which the modeling results were verified by actual formulation and testing. Thermal stability of the dyes was determined using isothermal. Thermogravimetric Analysis (TGA) at 200°C for 30 minutes. The dyes were evaluated in both traditional (free radical) and novel polymer systems to see if adequate sensitivity, resolution, and feature quality could be obtained. The studies showed that traditional free radical-based photochemistries are marginal at best for high resolution (1-2 micron) applications. To overcome this limitation, a new polymer system having photodimerizable functional units and acid functional groups was developed to impart photosensitivity and developer solubility, respectively. This system, which does not use free radical-initiated photopolymerization as a mechanism for patterning, shows low exposure dose requirements and is capable of resolving features less than 2 micron in size.