CMP Process Control With iAPC Segmented Modeling to Achieve Desired With-in-Wafer Uniformity and Geometry Across Consumable Life

The with-in-wafer uniformity and geometry of the CMP process varies across the life of consumables. The pre layer geometry and thickness significantly affect the post CMP process uniformity and geometry of the wafer. Inconsistency in post CMP wafer uniformity and geometry affects downstream process margin which leads to various yield issues like open or short circuit between contact to gate. Wafer geometry is measured, and out-of-control wafers are reworked to be within specified control limits. OOC and rework in CMP due to consumable caused variations in CMP and upstream process contribution to variation. To reduce rework, CMP is normally employed with process controls like APC (Advanced Process Control) and Endpoints. APC can be effective if integrated closely with CMP system with reduced delays in feedback, while Endpoints are challenging, since the oxide CMP layer is required for an endpoint within the layer (i.e., stop in layer), which makes it inaccurate and small changes in underlying layer properties affect endpoints to be less accurate. iAPC (integrated Advanced Process Control) is tightly integrated with the CMP polishing systems, which reduces feedback delays with a faster interface with the tool to achieve better process control. Modeling strategy of iAPC for CMP is discussed here in detail to achieve desired process control across consumable life and across tool pool. The modeling approach is segmented by modeling across wafer radial regions to include significance of polishing head’s zone to zone interaction and to get the wafer’s geometry characteristics on each region with consumable influenced by each polishing head zone. Thickness Out-of-Control (OOC) is significantly reduced with iAPC segmented modeling, and the model of identical process schemes is grouped together for continuous feedback across consumable life, which will be discussed in later sections of this paper.