Operating instructions

Process Description

Experimental results showed that good quality interfaces are obtained

when temperature is raised to a value lower than the eutectic

temperature (heating simultaneously from top/bottom), maintained

constant for short time to reach uniform heating of both wafers, than

increased again by heating both heaters to a temperature exceeding

the eutectic point with 10-20°C (depending on specific process

conditions and on substrates restrictions) followed by cooling down to a

temperature below the eutectic temperature.

A typical thermal profile of a eutectic wafer bonding process is shown in

fig. 6.

Figure 13 - Schematic thermal profile of a eutectic wafer bonding process

Eutectic wafer bonding does not require application of high contact

force. Due to the liquid phase formed during the process, high contact

force results always in metal squeezing out of the interface, resulting in

poor interface layer uniformity as well as contamination of the bond

tools and bond chamber. The role of the light contact force required is

just to ensure good contact of the two wafers and good contact of the

two heaters of the bonder with wafers’ back sides.

Eutectic wafer bonding is a good candidate to high-vacuum applications

as this process has a very low specific outgasing due to the use of only

high purity components. The liquid melt formed during process can only

enhance the high vacuum compatibility by allowing high quality sealing

even on non-perfect surfaces.

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