Causes and Prevention of Temperature-Dependent Bubbles in Silicon Wafer Bonding

Abstract

Unbonded areas or bubbles generated at the interface of bonded silicon wafers in the temperature range of 200-800°C have been investigated. Experiments described in this paper demonstrate that the desorption of hydrocarbon contamination at the silicon wafer surfaces appears to be a necessary condition for the formation of these bubbles. SIMS data also indicate the existence of hydrocarbons at the bonding interface. It is speculated that hydrocarbon gas such as CH4 is required for bubble nucleation and that either CH4 or H2 itself or a mixture of both gases is contained in these bubbles. Finally, methods to prevent the formation of these bubbles are presented.

Volker Lehmann: An Unconventional Scientist

“…He wrote a number of well-cited papers in this area (6,7). However, his scientific heart was still pounding for the electrochemistry of silicon.…”

<title>Silicon grisms fabricated by anisotropic wet etching and direct silicon bonding for high-resolution IR spectroscopy</title>

“…Direct silicon bonding refers to the adhesion mechanism of two mirror-polished, flat and clean silicon surfaces, brought into contact at room temperature, due to short range intermolecular forces, as the van der Walls forces [16][17] ; to strengthen the bond across the interface the bonded wafers have to undergo a heating step at high temperature 18 .…”

Strain analysis of InP/InGaAsP wafer bonded on Si by X-ray double crystalline diffraction

“…However, if the bonded materials have different expansion coefficients, thermal strain will develop in the course of annealing and cooling. Furthermore, a big internal strain will severely affect the bonding quality and induce a high density of dislocations [12][13][14], even result in the failure to bond [15]. Therefore, it is important to study the strain of bonded wafers and the distribution of stresses, and to put forward an effective method to reduce these stresses.…”