PVD System aids 300 mm power device manufacturing.
SPTS is to launch its Sigma fxP physical vapour deposition (PVD) system (shown below) for 300mm power device manufacturing.
Available system options include modules for frontside thick aluminium processing and backside metal deposition on ultra-thin wafers. The new system is designed to address the technical challenges customers face as they scale power PVD processes up to 300mm wafer size.
In a discrete MOSFET power device, current passes through the silicon substrate so electrical contacts are required on both sides of the wafer. Due to the high currents involved, thick aluminium alloy layers are deposited on the front side of the wafer (typically over 4 µm rather than less than 1 µm for mainstream silicon interconnects).
However, depositing thick films puts unusually large heat loads on process chamber hardware, potentially resulting in film contamination from outgassing in the chamber furniture.
This contamination can lead to the formation of aluminium whiskers/extrusions in the growing film that can ultimately result in device killer defects. In traditional front end fab deposition equipment, a common technique to mitigate this issue is to reduce film deposition rates with a corresponding reduction on system productivity.
However, SPTS says the Sigma fxP design overcomes that challenge without compromising throughput. Sigma fxP users routinely deposit thick aluminium layers at above 1.4 µm/min without any yield destroying whiskers or extrusions.
With frontside processing complete, wafers are thinned down to 50 µm or less to reduce "˜on-state' resistance and solder metal layers are deposited on the backside. No supporting carrier substrates are used and the ultra-thin, large area wafer will deform under the influence of uncontrolled film stresses, with miss-handling a potential consequence.
The Sigma fxP carries thin wafer handling hardware and uses film deposition stress control techniques to deliver high throughput processes with low wafer bow.
SPTS says that currently, seven out of the top ten power device manufacturers, and major foundries use the Sigma fxP as the process tool for power PVD processing. With power device manufacturing moving to 300mm format wafers, SPTS has successfully transferred its process knowledge and capability to the new platform.
"We are pleased to offer customers a complete solution for 300 mm Power PVD processing," says Chris Jones, product marketing manager at SPTS. "Sigma fxP systems are in full production for frontside thick Al and thin wafer backside processing. We are prepared to support the IDMs and foundries as they make the transition from 150 and 200mm wafer formats to 300mm."
