In below 90nm or in deep submircron nodes:
The contribution of interconnect delay in a timing path become significant and Coupling Cap component (Cc) in net delay can significantly alter slack values at an endpoint of a timing path.
So, RC corners have to be split up as per the contribution of each component Ground Capacitance (Cg) and Coupling capacitance (Cc).
So on top of the 2 conventional RC corners Cmax and Cmin, foundry came up with 2 more RC corners.
RC worst (also known as Delay corner) - Cc is min, Cg * R is max
RC best (also known as XTALK corner) - Cc is max. Cg * R is min
5 types of RC corners:
Cbest
Cworst
RCworst
RCbest
Typical
Cworst (Cmax corners):
Refers to corners which results max cap.
Corner has largest path delay for paths with short interconnect nets and can be used for max-path analysis.
RCworst (RC max corners):
Refers to corners which maximizes interconnect RC product.
Corner has largest path delay for paths with long interconnects and can be used for max-path analysis.
Cbest (Cmin corner):
Refers to corners with min cap
Interconnect Resistance is larget than the Typical corner.
Results in smallest delay for paths with short nets and can be used for min-path analysis.
RCbest (min interconnect RC product):
Refers to corners with min interconnect RC product.
Corresponds to min Resistance and larger than typical capacitance.
Results in smallest delay for paths with long interconnects and can be used for min-path analysis.
So there are 2 types of parasitics
1) C based
2) RC based
C-based means worst and best caps
RC-based means worst and best R in adjustment with C (RC product)
Based on experience, it was found that C-based extraction provides worst and best case over RC for internal timing paths because Capacitance dominates short wire. However, for large design, inter-block timing paths were often worst with RC worst parasitic since R dominates for long wires.
The contribution of interconnect delay in a timing path become significant and Coupling Cap component (Cc) in net delay can significantly alter slack values at an endpoint of a timing path.
So, RC corners have to be split up as per the contribution of each component Ground Capacitance (Cg) and Coupling capacitance (Cc).
So on top of the 2 conventional RC corners Cmax and Cmin, foundry came up with 2 more RC corners.
RC worst (also known as Delay corner) - Cc is min, Cg * R is max
RC best (also known as XTALK corner) - Cc is max. Cg * R is min
5 types of RC corners:
Cbest
Cworst
RCworst
RCbest
Typical
Cworst (Cmax corners):
Refers to corners which results max cap.
Corner has largest path delay for paths with short interconnect nets and can be used for max-path analysis.
RCworst (RC max corners):
Refers to corners which maximizes interconnect RC product.
Corner has largest path delay for paths with long interconnects and can be used for max-path analysis.
Cbest (Cmin corner):
Refers to corners with min cap
Interconnect Resistance is larget than the Typical corner.
Results in smallest delay for paths with short nets and can be used for min-path analysis.
RCbest (min interconnect RC product):
Refers to corners with min interconnect RC product.
Corresponds to min Resistance and larger than typical capacitance.
Results in smallest delay for paths with long interconnects and can be used for min-path analysis.
So there are 2 types of parasitics
1) C based
2) RC based
C-based means worst and best caps
RC-based means worst and best R in adjustment with C (RC product)
Based on experience, it was found that C-based extraction provides worst and best case over RC for internal timing paths because Capacitance dominates short wire. However, for large design, inter-block timing paths were often worst with RC worst parasitic since R dominates for long wires.
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