Structures and methods for testing integrated circuits and via chains therein

1. A structure for testing an integrated circuit comprising:

a semiconductor substrate;

a first via chain disposed over the semiconductor substrate, wherein the first via chain includes a first sequence of segments interconnected at N via regions by a first via arrangement, wherein the first via arrangement includes M N first vias at each respective via region in the first via chain;

a second via chain disposed over the semiconductor substrate, wherein the second via chain includes a second sequence of segments interconnected at N via regions by a second via arrangement different from the first via arrangement, wherein the second via arrangement includes M N +K N second vias at each via region in the second via chain, wherein K N ≧1 for at least one via region, and wherein the second sequence of segments is substantially the same as the first sequence of segments; and

a voltage sensing apparatus in electrical connection with each via chain and configured to drive a first constant current through the first via chain and to drive a second constant current through the second via chain to measure a differential voltage between the via chains.

2. The structure of claim 1 further comprising a controller configured to calculate a resistance of the vias in the first via chain from differential voltage.

3. The integrated circuit testing structure of claim 1 wherein the voltage sensing apparatus comprises a first four-terminal sensing apparatus connected to the first via chain and configured to drive the first constant current through the first via chain to measure a first voltage drop across the first via chain and a second four-terminal sensing apparatus connected to the second via chain and configured to drive the second constant current through the second via chain and to measure a second voltage drop across the second via chain.

4. The structure of claim 1 wherein:

the second via chain and the first via chain are electrically connected in series;

the first constant current is the second constant current;

the voltage sensing apparatus includes a first force connection and a second force connection configured to drive the second constant current through the second via chain and the first via chain;

the voltage sensing apparatus includes a first sense connection, a second sense connection, and a third sense connection;

the voltage sensing apparatus is configured to measure a second voltage drop across the second via chain with the first sense connection and the second sense connection; and

the voltage sensing apparatus is configured to measure a first voltage drop across the first via chain with the second sense connection and the third sense connection.

5. The structure of claim 1 wherein the first via chain comprises two first via chains and the second via chain comprises two second via chains, and wherein the structure further comprises an amplifier bridge including a first via chain—second via chain path and a second via chain—first via chain path formed from the first via chains and the second via chains, wherein the voltage sensing apparatus includes a first force connection and a second force connection configured to drive a constant current through the amplifier bridge, and a first voltage sense connection and a second sense connection configured to measure the differential voltage between the first via chain of the first via chain—second via chain path and the second via chain of the second via chain—first via chain path.

6. The structure of claim 1 wherein:

the first via chain and the second via chain each extend in a longitudinal direction; and

the vias in each via region are arranged in a linear layout substantially perpendicular to the longitudinal direction.

7. The structure of claim 1 wherein:

the first via chain and the second via chain each extend in a longitudinal direction;

a selected via region Z in the first via chain includes two vias and the corresponding selected via region Z in the second via chain includes three vias;

the two vias in the selected via region Z in the first via chain are arranged in a first linear layout substantially perpendicular to the longitudinal direction; and

two outer vias in the selected via region Z in the second via chain are arranged in a second linear layout equivalent to the first liner layout and a third via is positioned between the two outer vias.

8. The structure of claim 1 wherein:

the first via chain and the second via chain each extend in a longitudinal direction; and

the vias in each via region are arranged in a linear layout substantially parallel or coincident with the longitudinal direction.

9. The structure of claim 1 wherein:

the first via chain and the second via chain each extend in a longitudinal direction;

a selected via region Z in the first via chain includes two vias and the corresponding selected via region Z in the second via chain includes three vias; and

the two vias in the selected via region Z in the first via chain are arranged in a first linear layout substantially parallel or coincident with the longitudinal direction; and

two outer vias in the selected via region Z in the second via chain are arranged in a second linear layout equivalent to the first liner layout and a third via is positioned between the two outer vias.

10. A structure for testing a via chain comprising:

a first via chain having N via regions, wherein each via region includes M N vias;

a second via chain having N via regions, wherein each via region includes M N +K N vias and wherein:

K N ≧2 for at least two via regions when M N =1;

K N ≧1 for at least three via regions when M N =1; or

K N ≧1 for at least seven via regions when M N =2; and

a voltage sensing apparatus in electrical connection with each via chain and configured to drive a first constant current through the first via chain and to drive a second constant current through the second via chain to measure a differential voltage between the first via chain and the second via chain.

11. The structure of claim 10 further comprising a controller configured to calculate a resistance of the vias in the first via chain from the differential voltage.

12. The structure of claim 10 wherein the voltage sensing apparatus comprises a first four-terminal sensing apparatus connected to the first via chain and configured to drive the first constant current through the first via chain to measure a first voltage drop across the first via chain and a second four-terminal sensing apparatus connected to the second via chain and configured to drive the second constant current through the second via chain to measure a second voltage drop across the second via chain.

13. The structure of claim 10 wherein:

the second via chain and the first via chain are electrically connected in series;

the first constant current is the second constant current;

the voltage sensing apparatus includes a first force connection and a second force connection configured to drive the second constant current through the second via chain and the first via chain;

the voltage sensing apparatus includes a first voltage sense connection, a second sense connection, and a third sense connection;

the voltage sensing apparatus is configured to measure a second voltage drop across the second via chain with the first sense connection and the second sense connection; and

the voltage sensing apparatus is configured to measure a first voltage drop across the first via chain with the second sense connection and the third sense connection.

14. The structure of claim 10 wherein the first via chain comprises two first via chains and the second via chain comprises two second via chains, and wherein the structure further comprises an amplifier bridge including a first via chain—second via chain path and a second via chain—first via chain path formed from the first via chains and the second via chains, wherein the voltage sensing apparatus includes a first force connection and a second force connection configured to drive a constant current through the amplifier bridge, and a first voltage sense connection and a second sense connection configured to measure the differential voltage between the first via chain of the first via chain—second via chain path and the second via chain of the second via chain—first via chain path.

15. The structure of claim 10 wherein:

the first via chain and the second via chain each extend in a longitudinal direction; and

the vias in each via region are arranged in a linear layout substantially perpendicular to the longitudinal direction.

16. The structure of claim 10 wherein:

the first via chain and the second via chain each extend in a longitudinal direction;

for corresponding selected via regions Z in the first via chain and the second via chain M Z =2 and K Z =1;

the two vias in the selected via region Z in the first via chain are arranged in a first linear layout substantially perpendicular to the longitudinal direction; and

two outer vias in the selected via region Z in the second via chain are arranged in a second linear layout equivalent to the first liner layout and a third via is positioned between the two outer vias.

17. The structure of claim 10 wherein:

the first via chain and the second via chain each extend in a longitudinal direction; and

the vias in each via region are arranged in a linear layout substantially parallel or coincident with the longitudinal direction.

18. The structure of claim 10 wherein:

the first via chain and the second via chain each extend in a longitudinal direction;

for corresponding selected via regions Z in the first via chain and the second via chain M Z =2 and K Z =1;

the two vias in the selected via region Z in the first via chain are arranged in a first linear layout substantially parallel or coincident with the longitudinal direction; and

two outer vias in the selected via region Z in the second via chain are arranged in a second linear layout equivalent to the first liner layout and a third via is positioned between the two outer vias.

19. A method for testing an integrated circuit, the method comprising:

providing a semiconductor substrate disposed with a first via chain and a second via chain, wherein the first via chain includes a first sequence of segments interconnected at N via regions by a first via arrangement, wherein the first via arrangement includes a selected number of first vias at each respective via region in the first via chain, wherein the second via chain includes a second sequence of segments interconnected at N via regions by a second via arrangement different from the first via arrangement, wherein the second via arrangement includes a selected number of second vias at each respective via region in the second via chain, and wherein the second sequence of segments is substantially the same as the first sequence of segments;

driving a first constant current through the first via chain;

driving a second constant current through the second via chain, wherein the second constant current is equal to the first constant current; and

calculating a resistance of the first vias in the first via chain.

20. The method of claim 19 wherein calculating a resistance of the first vias in the first via chain comprises:

calculating a first resistance in the first via chain;

calculating a second resistance in the second via chain; and

subtracting the second resistance from the first resistance to calculate the resistance of the first vias in the first via chain.