Multi-cut vias are a DFM technique to increase the Yield for UDSM processes.
In a IC, a via is used to connect a metal track of one metal layer with a metal track of another metal layer. Generally, for signal lines other than the power lines, one via is provided for each connection point. Such via is called a "single-cut via".
With decreasing technology nodes in IC industry, the metal width gets reduced, and also the cross-sectional area of a via will decrease. Accordingly, in the manufacturing process, it has become difficult to form a via of a desired pattern. In a worst case scenario, an open failure occurs in the single-cut via formation part and thus the desired device operation cannot be implemented, resulting in a lower yield.
Further, as the cross-sectional area of a via decreases, the delay time in signal lines increases, and disconnection rate also increases due to electro-migration. This causes lowering of device reliability.
As a way out of these issues, multiple vias may be provided in parallel for each connection point. Such via is called a "multi-cut via". If two vias are provided for each connection point, such via is called a "double-cut via" . After layout, single-cut vias are replaced with multi-cut vias as many as possible so that the device reliability improves.
Hope it clarifies..