Design And Fabrication of Condenser Microphone Using Wafer Transfer And Micro-electroplating Technique

TL;DR

This paper introduces a new fabrication process for condenser microphones using wafer transfer and micro-electroplating, demonstrating how design parameters influence sensitivity and frequency response.

Contribution

It presents a novel fabrication method and analyzes the effects of design parameters on microphone performance, achieving a flat frequency response up to 20 kHz.

Findings

Sensitivity of -45.3 dB/Pa at 24 V bias

Flat frequency response up to 20 kHz

Microfabrication process using wafer transfer and electroplating

Abstract

A novel fabrication process, which uses wafer transfer and micro-electroplating technique, has been proposed and tested. In this paper, the effects of the diaphragm thickness and stress, the air-gap thickness, and the area ratio of acoustic holes to backplate on the sensitivity of the condenser microphone have been demonstrated since the performance of the microphone depends on these parameters. The microphone diaphragm has been designed with a diameter and thickness of 1.9 mm and 0.6 $\mu$m, respectively, an air-gap thickness of 10 $\mu$m, and a 24% area ratio of acoustic holes to backplate. To obtain a lower initial stress, the material used for the diaphragm is polyimide. The measured sensitivities of the microphone at the bias voltages of 24 V and 12 V are -45.3 and -50.2 dB/Pa (at 1 kHz), respectively. The fabricated microphone shows a flat frequency response extending to 20 kHz.