Technology of spatial light modulators based on viscoelastic layers

Abstract

We present a novel technology for spatial light modulators based on electrostatic deformation of viscoelastic layers. To fabricate the modulator structure, we bond two silicon chips using an intermediate viscoelastic layer and then etch away the top chip. This results in a very high optical quality viscoelastic layer deposited directly on top of the bottom chip. Light modulation is achieved by deforming the deposited viscoelastic layer using electrodes integrated into the bottom chip. Before bonding, the top chip is coated with a 80nm layer of aluminum and 50nm layer of nitride, that serves as the etch stop and reflector at the silicon. The thin nitride layer functions as the etch stop. Special technology was developed for low-stress side and back etch protection of contact pads of the devices. The continuous reflective membrane results in a 100% optical fill factor, enabling the modulator to handle relatively high optical loads. Also, given a sufficient bias voltage, the voltages on the electrodes should be in the range of 15-30V, making integrated solutions possible. Applications lie in the field of optical communication networks and projection displays.