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

Mitsutoshi Makihata,Shuji Tanaka,Yutaka Nonomura,Masayoshi Esashi,Masanori Muroyama,Takahiro Nakayama

doi:10.3390/s18072374

Abstract

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 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 m thick BCB isolation layer and this minimum package structure.

Highlights

Whole body tactile sensation is a desired function in the current movement of robots into our society to assist humans
Forming grooves before wafer bonding improves a yield significantly compared to the packaging method which forms through holes after bonding we have reported previously [6]
The concept of the tactile sensor chip with a communication function is proven by prototyping the new device chip composed of a silicon diaphragm and ASIC that are integrated and packaged by the batch fabrication

Summary

Introduction

Whole body tactile sensation is a desired function in the current movement of robots into our society to assist humans. In contrast to industrial robots, these robots are required to work safely in an uncontrolled environment and to have highly versatile capabilities of action [1]. There are a tremendous amount of studies and products that have been developed in the past thirty years. The majority of these tactile sensors are not considered to cover a whole body of a robot but designed to achieve the best performance as a single chip such as multi-axis sensing, high-density array, and flexibility [2]. The recent requirements for the whole body tactile sensor are a capability for large area sensing, satisfaction of both large number of sensor and rapid response time, and low cost. MEMS (Micro Electro Mechanical Systems) technology would fulfill these requirements

Methods

Results

Conclusion