Critical dimension for trench and vias

1. A method of forming an integrated circuit (IC) comprising:

providing a test substrate;

etching the test substrate using a first etch process to form a plurality of test structures on the test substrate, wherein

a test structure comprises trenches and spaces between the trenches, and

different test structures of the plurality of test structures have different test structure dimensions;

determining a trench critical dimension (T CD ) of trenches in a via level of the IC using the plurality of test structures on the test substrate formed by the first etch process, wherein the T CD is equal to a selected test structure dimension of a selected test structure from the plurality of test structures on the test substrate, wherein the selected test structure has trenches and vias having substantially the same depth from the first etch process;

providing a partially processed substrate of the IC;

depositing a dielectric layer on the partially processed substrate;

forming the trenches using the T CD in a periphery of the substrate in the dielectric layer and vias in the dielectric layer, wherein the trenches and vias have substantially the same depth due to the T CD ;

filling the trenches and vias with a conductive material; and

continuing to process the substrate to complete forming the IC.

2. The method of claim 1 wherein the trenches in the via level serve as guard rings surrounding the periphery of the IC.

3. The method of claim 1 wherein the depths of vias and trenches are within 5% of each other.

4. The method of claim 1 wherein determining the T CD comprises forming the plurality of test structures comprising test trenches having a geometric pattern with components which are consistent with the trenches in the periphery of the substrate, wherein the plurality of test structures comprise the test trenches of varying widths and pitches.

5. The method of claim 4 wherein the geometric pattern of test trenches includes straight and angled components.

6. The method of claim 4 wherein the geometric pattern of test trenches includes straight, 45° and 90° components.

7. The method of claim 4 wherein the plurality of test structures comprise a plurality of open ended test trenches with straight and angled components.

8. The method of claim 4 wherein the plurality of test structures comprise:

a first set of first test structures, the first test structures each comprising a plurality of first test trenches having a same width, wherein different first test structures have different pitches; and

a second set of second test structures, the second test structures each comprising a plurality of second test trenches having a same pitch, wherein different second test structures have different widths.

9. The method of claim 8 wherein the geometric pattern of test trenches includes straight and angled components.

10. The method of claim 8 wherein the geometric pattern of test trenches includes straight, 45° and 90° components.

11. The method of claim 8 wherein the plurality of test structures comprise a plurality of open ended test trenches with straight and angled components.

12. The method of claim 1 wherein the plurality of test structures comprise:

a first set of first test structures, the first test structures each comprising a plurality of first test trenches having a same width, wherein different first test structures have different pitches; and

a second set of second test structures, the second test structures each comprising a plurality of second test trenches having a same pitch, wherein different second test structures have different widths.

13. The method of claim 12 wherein the geometric pattern of test trenches includes straight and angled components.

14. The method of claim 12 wherein the geometric pattern of test trenches includes straight, 45° and 90° components.

15. The method of claim 12 wherein the plurality of test structures comprise a plurality of open ended test trenches with straight and angled components.

16. A method of forming a device comprising:

providing a test substrate;

etching the test substrate using a first etch process to form a plurality of test structures on the test substrate, wherein

a test structure comprises trenches and spaces between the trenches, and

different test structures of the plurality of test structures have different test structure dimensions;

determining a trench critical dimension (T CD ) of trenches in a via level of the device using the plurality of test structures on the test substrate formed by the first etch process, wherein the T CD is equal to a selected test structure dimension of a selected test structure from the plurality of test structures on the test substrate, wherein the selected test structure has trenches and vias having substantially the same depth from the first etch process;

providing a dielectric layer on a substrate of the device; and

forming the trenches and vias in the dielectric layer, wherein the trenches are formed using the T CD , wherein the trenches and vias are formed with substantially the same depth due to the T CD .

17. The method of claim 16 wherein the trenches in the dielectric layer serve as guard rings surrounding the periphery of the device.

18. The method of claim 16 wherein depths of vias and trenches are within 5% of each other.

19. The method of claim 16 wherein determining the T CD comprises forming the plurality of test structures comprising test trenches having a geometric pattern with components which are consistent with the trenches in the periphery of the substrate, wherein the test structures comprise the test trenches of varying widths and pitches.

20. The method of claim 19 wherein the geometric pattern of test trenches includes straight and angled components.

21. The method of claim 19 wherein the geometric pattern of test trenches includes straight, 45° and 90° components.

22. A method of forming a device comprising:

providing a test substrate;

etching the test substrate using a first etch process to form a plurality of test structures on the test substrate, wherein different test structures of the plurality of test structures have different test structure dimensions;

determining a trench critical dimension (T CD ) of trenches in a via level of the device using the plurality of test structures on the test substrate formed by the first etch process, wherein the T CD is equal to a selected test structure dimension of a selected test structure from the plurality of test structures on the test substrate, wherein the selected test structure has trenches and vias having substantially the same depth from the first etch process; and

using the T CD to form trenches and vias in a via level in the device.