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 o 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.

Fabrication of Tapered 3D Microstructure Arrays Using Dual-Exposure Lithography (DEL)

“…When the wait time was introduced between exposures (on top of the mask rotation time) (Dome to Bullet, Bell to Pillar, Figure 2 F), the resulting microstructures became much taller with a nearly four times (Bullet; height 75 µm), and three times (Pillar; height 110 µm) increase, indicating much deeper SU-8 micro-pockets. This result is likely caused by the free-radical quenching during photopolymerization, as reported in previous studies [ 49 , 50 , 51 , 52 ]. We speculate that through the wait-time (on top of mask rotation time), the free radicals formed during the first exposure could have likely been quenched and reduced the number of free radicals present for further resist polymerization.…”

Centimeter scale color printing with grayscale lithography

“…The conventional color filter arrays for imaging sensors and flat panel display are usually manufactured by using dye-doped color resist 33 – 35 However, the chemical dyes usually have poor durability, and the fabrication of the color filters involves multiple photolithography processes. In comparison, the spatially variant large area F–P cavities can be used to design the color filter arrays.…”

Smartphone instrument for portable enzyme- linked immunosorbent assays

“…CMOS sensors, like those found in most smartphone devices, are wavelength-independent photon collectors that are converted into RGB pixels via physical filters. These filters are comprised of colored dyes that each have their own spectral response [17], and an additional infrared cutoff filter with a response that provides a sharp drop in transmittance that can vary even among batches of identical cameras by 10 nm [18]. In such a system, light intensity and color are intrinsically intertwined as they both rely on the number of photons captured by the RGB pixels compared to that of their adjacent neighbors.…”