Method and semiconductor structure for monitoring etch characteristics during fabrication of vias of interconnect structures
By forming a trench-like test opening above a respective test metal region during the etch process for forming via openings in a dielectric layer stack of sophisticated metallization structures of semiconductor devices, the difference in etch rate in the respective openings may be used for generating a corresponding variation of electrical characteristics of the test metal region. Consequently, by means of the electrical characteristics, respective variations of the etch process may be identified.
1. A method, comprising:
forming a via opening in a dielectric layer formed on an etch stop layer formed above a first region and a second region of a semiconductor device according to a first etch process;
forming a test opening commonly with said via opening in said dielectric layer according to said first etch process, said test opening having at least one lateral dimension that is greater than a lateral dimension of said via opening;
obtaining electric measurement data from a metal region located below said test opening; and
estimating at least one characteristic of said first etch process on the basis of said electric measurement data.
2. The method of claim 1 , wherein forming said via opening and said test opening comprises etching through said dielectric layer and stopping said first etch process prior to etching through said etch stop layer within said via opening in said first region.
3. The method of claim 1 , wherein said electric measurement data comprises a measurement value related to an electric conductivity of said metal region.
4. The method of claim 1 , further comprising estimating an etch rate of said etch stop layer on the basis of said electric measurement data.
5. The method of claim 1 , further comprising forming at least one further test opening in said second region, said at least one further test opening having lateral dimensions differing from the lateral dimensions of said test opening, and obtaining electric measurement data from said at least one further test opening.
6. The method of claim 1 , further comprising performing a second etch process to etch through said etch stop layer in said first region and controlling said second etch process on the basis of said electric measurement data.
7. The method of claim 1 , further comprising controlling at least one process parameter of said first etch process on the basis of said at least one estimated characteristic.
8. The method of claim 5 , further comprising filling said test opening and said at least one further test opening at least partially with a conductive substance prior to obtaining said electric measurement data.
9. The method of claim 8 , wherein obtaining said electric measurement data comprises determining a resistance of the test opening and said at least one further test opening based on said conductive substance.
10. The method of claim 1 , further comprising processing one or more substrates with said first etch process and controlling at least one process parameter of said first etch process on the basis of said at least one electric characteristic when processing said one or more substrates.
11. The method of claim 8 , further comprising removing said conductive substance from said test opening and said at least one further test opening.
12. A method, comprising:
performing a first etch process to form a via opening having a first lateral dimension and a first test opening having a second lateral dimension greater than said first lateral dimension in a dielectric layer stack of a semiconductor device, said dielectric layer stack comprising an etch stop layer, said first etch process being controlled to stop prior to etching through said etch stop layer in said via opening; and
determining at least one first electric property of a metal region formed below said first test opening.
13. The method of claim 12 , further comprising estimating at least one first characteristic of said first etch process on the basis of said at least one first electric property.
14. The method of claim 12 , further comprising performing a second etch process to etch through said etch stop layer in said via opening and controlling said second etch process on the basis of said at least one first electric property.
15. The method of claim 14 , wherein controlling said second etch process comprises controlling an etch time of said second etch process.
16. The method of claim 12 , further comprising selecting said second lateral dimension so as to result in etching through said etch stop layer in said first test opening during said first etch process.
17. The method of claim 12 , further comprising forming a plurality of second test openings, each of said second test openings having lateral dimensions other than said second and said first lateral dimensions.