Patent ID: 8198150

Claim:
A method of forming a semiconductor die comprising: etching a bottom side opening in a silicon region and into a first well, the silicon region having a first conductivity type, a top surface, and a bottom surface, the bottom side opening extending from the bottom surface of the silicon region through the silicon region and into the first well, the first well touching the silicon region, and having a top surface that touches the top surface of the silicon region, a bottom surface spaced apart from the bottom surface of the silicon region, and a dopant concentration greater than a dopant concentration of the silicon region; the opening having an end surface spaced apart from the top surface of the first well and the bottom surface of the silicon region; forming a metallic material on the bottom surface of the silicon region and in the bottom side opening to fill up the bottom side opening, the metallic material including aluminum that touches the silicon region and the first well; removing the metallic material from the bottom surface of the silicon region to form a first plug that touches the silicon region and the first well, the first plug having a side wall; and heating the die to a temperature for a predetermined period of time to grow spikes that extend away from the side wall of the first plug in all directions into the silicon region and the first well.