3. Design and fabrication
The AMIS 0.35 μm CMOS process has been used to realize the chip. Two photodiodes in series together with
current-to-voltage converter are designed into one unit cell. Two of these are required in the 2×2 detector array
configuration. The differential photodiode is detected when the shadow is projecting on either surface of
photodiodes while the series equivalent photodiode voltage and current is powering the readout circuit. The
photodiode area is 550×350 μm2. With this dimension of photodiode, the photocurrent is large enough for electrical
powering of the amplifier. IC compatible micromachining for fabrication of the pole has not yet been included in the
initial devices. The package has been modified to include a pattern to cast a shade on the diode array in the initial
experiments.