Design and Fabrication Technology of Low Profile Tactile Sensor with Digital Interface for Whole Body Robot Skin

• Published in: Sensors (Basel, Switzerland) Vol. 18; no. 7; p. 2374
• Main Authors: Makihata, Mitsutoshi, Muroyama, Masanori, Tanaka, Shuji, Nakayama, Takahiro, Nonomura, Yutaka, Esashi, Masayoshi
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 21-07-2018; MDPI
• Subjects: Adhesives; Application specific integrated circuits; benzocyclobutene; Bond strength; Bonding; Capacitance; Chemical-mechanical polishing; CMOS; Design; Diaphragms (mechanics); Digital technology; Integrated circuits; International conferences; MEMS-CMOS integration; Microelectromechanical systems; Packaging; Packet transmission; Polymers; Robots; Semiconductors; sensor network; Sensors; Silicon; Simulation; Skin; tactile sensor; Tactile sensors (robotics); through silicon via; Variation; wafer level packaging; United States > US; Japan; MEMS-CMOS integration; tactile sensor; benzocyclobutene; sensor network; through silicon via; wafer level packaging
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s18072374

Covering a whole surface of a robot with tiny sensors which can measure local pressure and transmit the data through a network is an ideal solution to give an artificial skin to robots to improve a capability of action and safety. The crucial technological barrier is to package force sensor and communication function in a small volume. In this paper, we propose the novel device structure based on a wafer bonding technology to integrate and package capacitive force sensor using silicon diaphragm and an integrated circuit separately manufactured. Unique fabrication processes are developed, such as the feed-through forming using a dicing process, a planarization of the Benzocyclobutene (BCB) polymer filled in the feed-through and a wafer bonding to stack silicon diaphragm onto ASIC (application specific integrated circuit) wafer. The ASIC used in this paper has a capacitance measurement circuit and a digital communication interface mimicking a tactile receptor of a human. We successfully integrated the force sensor and the ASIC into a 2.5 × 2.5 × 0.32.5×2.5×0.3 mm die and confirmed autonomously transmitted packets which contain digital sensing data with the linear force sensitivity of 57,640 Hz/N and 10 mN of data fluctuation. A small stray capacitance of 1.33 pF is achieved by use of 10 μm thick BCB isolation layer and this minimum package structure.