Fabrication and characterization of a low-temperature hermetic MEMS package bonded by a closed-loop AuSn solder line

Abstract

In this paper, we present a hermetic MEMS package bonded by a closed-loop 8OAu20Sn solder line. We designed three different test specimens including a substrate-heated specimen without an interconnection line (SHX), a substrate-heated specimen with an interconnection line (SHI), and a locally heated specimen with an interconnection line (LHI). A pressurized helium leak test was carried out to evaluate the hermetic seal along a critical pressure test to measure bonding strength. In the bonding process, the substrate heating methods (SHX, SHI) require 400 degrees C and 40 min, while the local heating method (LHI) requires a heater power of 6.76 W for 4 min. In the hermeticity test, SHX, SHI, and LHI show leak rates of 8.4 +/- 6.7x10(-10) mbar-l/s, 13.5 9.8x10(-10) mbar-l/s, and 18.8 +/- 9.9x10(-10) mbar-l/s, respectively, for the same internal volume of 6.89 +/- 0.2x10(-6) l. In the critical pressure test, no fracture was found in the bonded specimens at an applied pressure of 1 +/- 0.1 MPa. From these results, we determine an approximate bonding strength of the test specimen as 3.53 +/- 0.07 MPa. We have experimentally verified that LHI shows the potential of hermetic MEMS packaging with an interconnection line and a bonding process for mass production that requires little time.