Heterogeneous Integration of LSI Amplifier and the Tactile Sensor Using Stacking and Through-Si-Via Techniques

Abstract

We have developed the tactile sensor using the microcantilevers with strain gauge film which can detect normal and shear forces simultaneously. In this work, the tactile sensor and the IC amplifier have been integrated heterogeneously to shorten the wire length by chip-on-chip stacking and reduce the noise in the output voltage. Standard deviation of the noise can be reduced from 27.6 mV to 3.3 mV by heterogeneous integration of the tactile sensor and the IC amplifier using Au wire bonding. By this heterogeneous integration, the device size and wiring numbers can be reduced, and installation of more sensors is allowed on fingertips of the robot. Moreover, through-silicon-via (TSV) holes were fabricated to mount an IC amplifier on the backside of the sensor chip, instead of using Au wires. Although TSV can be fabricated successfully, resistance to sacrificial etching process is problem. As a result, Si3N4 used instead of SiO2 has improved insulation between TSVs.

Fabrication and Noise Reduction of the Miniature Tactile Sensor Using Through-Silicon-Via Connection with Signal Amplifier

“…So, Au was deposited because the electrical disconnection frequently occurs at the step of TSV. 29) After the additional deposition, electrical connection was improved, and all of the 30 points were connected. Figure 5 shows the cross sectional view of the fabricated TSVs.…”

“…The tip height of the microcantilevers is 20-30 m. The Si 3 N 4 , NiCr, Au, and Cr films have enough durability against BHF solution for 5 h. It was found that fabricated TSVs have enough tolerance to the fabrication process of the microcantilevers. 29) The microcantilevers were covered with PDMS (Toray Dow Corning Silpot184). At first, PDMS thick film of about 40 m thickness is spin-coated to improve the robustness of tactile sensor.…”

“…IC amplifier chip was mounted on the frontside of the tactile sensor chip (chip stacking). 29) In this work, the tactile sensor using TSV connection has been fabricated to mount an IC amplifier on the backside of the sensor chip instead of using Au wires.…”