Highly reliable, cost effective and thermally enhanced AuSn die-attach technology

A method for manufacturing a Si circuit die to be attached to a heat sink, wherein said circuit die is sawed from a wafer, comprising the steps of:

• reducing the thickness of said wafer by mechanical grinding,
• applying an isotropic wet chemical etching to the wafer to eliminate crystal defects,
• evaporating adhesion and diffusion barrier metals on the backside of said wafer,
• evaporating Au and Sn on the backside of the wafer, wherein the weight proportion of Au, is equal to or larger than 85%, and
• sawing the wafer into circuit dies.

A Si circuit die comprising:

• a layer of adhesion and diffusion barrier metals on a backside of said die to be attached to a heat sink,
• a stack of alternating layers of Au and Sn, where a first layer in said stack, which adjacent to said layer of diffusion barrier metals, is an Au layer and the final layer in said stack is an Au layer,
• wherein
• the weight percentage of Au in relation to Sn in said stack is equal to or larger than 85%.