Challenges

Polysilicon plug CMP is used in Front End Of Line (FEOL) DRAM processes for planarization at the critical contact level. Since measurements on test structures do not correlate well with in-die structures, in-die measurements are essential to controlling the process. The complex structure of the poly plug together with the oxide cap and stop layer that top the plug present a challenge to in-die measurements.

Solutions

Nova is the industry leader in CMP process control. Nova’s metrology solutions ensure precise in-die and test structure measurements of poly plugs. With high accuracy and throughput of up to 200 WPH, Nova’s Integrated Metrology (IM) enables closed loop control of the poly plug CMP process to provide uniformity - within wafer (between zones) and wafer-to-wafer. The implementation of Closed Loop Control (CLC) reduces the number of reworks and increases yield, while reducing CMP cycle times and increasing overall throughput. When lot-to-lot control is required, Nova’s Stand-alone metrology (SA) provides a cost effective solution with throughput of up to 150 WPH and industry-leading fleet (tool-to-tool) matching.

As device geometries continue to shrink, Nova’s metrology measurements are not restricted to solid pads, but can also be made on 2D and 3D test structures as well as in-die.