A 1024-element high-performance silicon tactile imager

A 32×32-element capacitive silicon tactile imager, for use in precision robotics applications where high density and high resolution are important, is discussed. The silicon chip measures 1.6 cm×1.6 cm, and is organized in an X-Y matrix of 1024 capacitor elements on 0.5-mm centers. The process uses two boron diffusions (deep and shallow) followed by a silicon-to-glass electrostatic bonding step and subsequent unmasked wafer dissolution. This results in a thick center plate for the sense capacitor supported by thinner beams. Only four noncritical masking steps for silicon and two for glass are required. A measured force sensitivity of 0.27 pF/gmf/element, temperature sensitivity of less than 3o p.p.m./°C, and maximum operating force of ≈1 gm/element has been obtained. A discrete data acquisition system used with the device offers over 6 b of force resolution, and the imager can be read at a rate of 15-20 μs/element, offering an effective frame rate of 5.1 ms