Electrical, Mechanical, and Hermetic Properties of Low-Temperature, Plasma Activated Direct Silicon Bonded Joints

Abstract

The electrical, mechanical, and hermeticity properties of low-temperature, plasma activated direct silicon bonds were investigated. On individual dies with a bonding area ranging from 1-4 mm 2 , the bonded interface was found to have a capacitance ranging from 2.62 pF/mm 2 -2.89 pF/mm 2 at 1 kHz. Linear I-V curves showed ohmic behavior without hysteresis. A resistance around 2.2 and a current density of 1.1 × 10 4 A/m 2 was measured at DC. We speculate that the capacitive and resistive responses are related to traps that are formed during the plasma activation process. The applied bonding process resulted in hermetic sealing with 100% yield on 2 × 481 dies. The maximum leak rate of the seals was 2.4 × 10 −11 mbar·l·s −1 , but could be significantly lower. No gross leaks were observed following a steady-state life test, a thermal shock test, and a moisture resistance test applied on 100 dies.

A Comparative Study: Void Formation in Silicon Wafer Direct Bonding by Oxygen Plasma Activation with and without Fluorine

“…Plasma activated bonding is one of promising candidates in wafer bonding field. [1][2][3] In the past decade, much progress in terms of plasma generation, plasma treatment parameters, and annealing conditions has been achieved to allow high strength bonding at low temperatures with minimal defects. 4 Since wafer bonding is often used as a middle process during device manufacturing, subsequent heating (so-called "annealing") processes are inevitable for bonded wafers.…”