Low Temperature Bonding Using In-Situ Radical Activation

Abstract

A tool for performing surface activation using radicals (RAD activation), followed by the subsequent, in-situ, low temperature bonding of wafers, was presented previously (1). This paper reports on the further characterization of the (RAD) tool and the importance of water vapor in the activation / bond chamber. The tool uses the diffusion of radicals across the wafer surfaces to activate those surfaces. Because the activation is performed in-situ in an aligner-bonder, the activated surfaces do not get the opportunity to adsorb any atmospheric contaminants between activation and bonding and this results in more reproducible interfaces from bond to bond. Results for various bonded wafers are presented in terms of bond quality and bond strength. These results demonstrate the importance of the wafer separation during the activation process, in order to minimize the process time, and the need for a controllable / variable source of H 2 O in the activation gas in order to maximize bond strength. .

A Review of Hydrophilic Silicon Wafer Bonding

“…2008 is the year of the first full paper publication detailing the radical (or RAD) ring by T. Rogers and N. Aitken. 113 The RAD ring itself -which is a structure designed to allow only the neutral species created in a discharge to reach the wafer surface -is described and initial results are published. These conclude that the RAD ring is capable of producing bonds of equal strength to plasma activated wafers.…”