System and method of modelling capacitance of on-chip coplanar transmission line structures over a substrate

1. A method, implemented by a computer device, of modeling capacitance for a subject structure comprising a pair of long conductors surrounded by a dielectric material and supported by a substrate, wherein the capacitance of the conductors is a function of current frequency, the method comprising:

receiving, at said computer device, parameters characterizing said

surrounding dielectric material of said subject structure as a first dielectric with a first permittivity (ε 1 ) and the substrate as a second dielectric with a second permittivity (ε 2 );

providing, at said computer device, a known capacitance (C 2 ) value of a basis structure characterized as having a surrounding dielectric material of same first permittivity (ε 1 ) and a substrate of a second permittivity (ε 2 ) different than said second permittivity of said subject structure and having a same cross-sectional geometry of said subject structure;

modeling, at said computer device, the capacitance (C 1 ) of said subject structure for values of the first and second permittivity (ε 1 , ε 2 ) based on known capacitance (C 2 ) computed for said basis structure with the same first permittivity (ε 1 ) and a different second permittivity (ε 2 ),

and using said modeled capacitance (C 1 ) for design of an integrated circuit having said subject structure.

2. A method as claimed in claim 1 , wherein the known capacitance is computed for a basis structure with the same cross-section geometry as the subject structure.

3. A method as claimed in claim 1 , wherein the first permittivity does not depend on frequency and the second permittivity does depend on frequency.

4. A method as claimed in claim 1 , wherein the modelled capacitance is high frequency capacitance.

5. A method as claimed in claim 1 , wherein the capacitance of the subject structure is modelled from the capacitance of one or more basis structures using an extrapolation or interpolation formula.

6. A method as claimed in claim 1 , wherein the input information for the method includes: the first permittivity ε 1 of The first dielectric of both the subject structure and the basis structure, the second permittivity ε 2 of The second dielectric of the basis structure, and the cross-sectional geometry of the subject or basis structure.

7. A method as claimed in claim 1 , wherein The known capacitance is provided by one of an Electro-Magnetic solver, an analytical formula, a quasi-analytical formula, and look-up tables.

8. A method as claimed in claim 1 , wherein the surrounding dielectric material is an insulating material and the substrate behaves as a conductor at low frequencies and as a dielectric at very high frequencies.

9. A method as claimed in claim 1 , wherein the dielectric is an oxide dielectric and the substrate is a silicon substrate.

10. A method as claimed in claim 1 , wherein the pair of long conductors each have a width and metal layer thickness of the same order.

11. A method as claimed in claim 1 , wherein the pair of long conductors are spaced apart by a distance of the same order as the width and thickness of the conductors.

12. A method as claimed in claim 1 , wherein the cross-section of each of the long conductors is constant along the length.

13. A method as claimed in claim 1 , wherein each of the long conductors is formed of a single conductor or more than one parallel conductor.

14. A method as claimed in claim 1 , wherein the structure comprises on-chip coplanar transmission lines over a conductive substrate.