what are Multicut vias & advantage of it?

What is the advantage of multicut vias over single cut vias?

Thanks
Kumar

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..

Hi pavan,
Thanks alot for the nice explanation. How do we calculate the resistance & capacitance of a VIA? Any idea?

Rgds,

Its simpler concept...via is a path for current to flow or a path of resistance...1 via=1 resistor...when you have 2 vias , we have 2 resistors in parallel..so more the no. of vias less is the resistance...but more no. of vias adds to cap value...:-|

kumar_eee said:

Hi pavan,
Thanks alot for the nice explanation. How do we calculate the resistance & capacitance of a VIA? Any idea?

Rgds,

Click to expand...

Your technology/PDK supplier should provide you with such information. Usually this data is placed in the "Design Rules" papers. You can find couple/fringe capacitance and resistance information for each layer/interlayer. Some fabs also provide with the Kelvin contact res vs current info.

hi,
agree with pavan,
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 .

To reduce the manufacture failure chance.

There is a tool called saturnpcb, in which you can calculate VIA properties.

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