The use of a black pigment polyimide, DARC~R300, as a light absorber on an optical sensor

摘要

In the design and fabrication of arrayed opto-electronic detection devices, it is critical to provide optical isolation between the individual array cells to prevent optical crosstalk between channels and contribution from stray light that would otherwise result in degraded signal-to-noise performance. To accomplish this, the light incident between the cells' optical apertures and around the periphery of the array must be blocked from entering the active semiconductor layers. One approach has been to use an opaque layer of metal, but this can lead to reflections and light trapping and ultimate absorption of this stray light in device active regions. Another approach is to use an absorbing material to block stray light. DARC300, a registered trademark of Brewer Science, is an optically absorbing, photo-definable polyimide designed for exactly this purpose. Presented here are the results of the DARC300 blocking layers, including a review of the process development and issues addressed along the way. The most prevalent issues with the DARC300 were the remnants of black pigments after develop, and the insufficiently developed features. A normalized spectral response of a 4-channel, fixed cavity, Fabry-Perot micro spectrometers, with and without the optical blocking layer between cells and around the periphery of the array are shown to greatly enhance device performance with the use of the DARC300 layer.