Process control using non-zero order diffraction
A method of controlling a manufacturing process, the method including the steps of a) providing a testing area with a periodic structure, where the periodic structure includes a series of sets of patterned features, b) illuminating the periodic structure with a light, thereby producing a non-zero order diffraction signal, c) collecting the diffraction signal to produce a test signature, d) matching the test signature with a reference signature, where the reference signature was previously produced by performing steps a), b), and c) with respect to a reference structure that is at least similar to the periodic structure, and e) controlling a manufacturing process using a control setting set associated with the matching reference signature.
1. A method of controlling a manufacturing process, the method comprising the steps of:
a) providing a testing area with a periodic structure having a period d, wherein within each period d the periodic structure includes a plurality of alternating lines and spaces therebetween, and wherein said lines and spaces within said each period d have a monotonically increasing width;
b) illuminating the periodic structure with a light, thereby producing a plurality of non-zero order diffraction signals;
c) collecting the diffraction signals to produce a test signature;
d) matching the test signature with a reference signature; and
e) controlling a manufacturing process using a control setting set associated with the matching reference signature.
2. The method according to claim 1 , wherein the manufacturing process is a lithography process, and wherein the control setting set includes any of exposure energy and focus conditions of exposing light.
3. The method according to claim 1 , wherein the periodic structure is present on a semiconductor wafer.
4. The method according to claim 1 , wherein any of steps a), b), c), d) and e) are performed to control a lithography process applied to structures progressing on a production line.
5. The method according to claim 1 and further comprising selecting a wavelength of said light, wherein the non-zero order diffraction signal is produced when the light of the selected wavelength illuminates the periodic structure.
6. The method according to claim 1 wherein the illuminating is performed at a first angle with respect to the periodic structure, wherein the collecting is performed at a second angle with respect to the periodic structure, and wherein the illuminating and the collecting are performed at different points in space.
7. The method according to claim 1 , wherein the reference signature was previously produced by performing steps a), b), and c) with respect to a reference structure.
8. The method according to claim 1 wherein said plurality of non-zero order diffraction signals includes positive and negative diffraction orders and the test signature includes a differential signal obtained from corresponding positive and negative diffraction orders.
9. The method according to claim 1 wherein the providing comprises providing the periodic structure having a period d that is greater than a wavelength A of the light divided by two.
10. The method according to claim 1 , wherein the illuminating comprises selecting a wavelength λ of the light, and wherein λ˜d.
11. The method according to claim 1 , wherein the reference signature was previously produced by using a theoretical model.
12. The method according to claim 1 , wherein said positive (+) and negative (−) diffraction orders includes +1 and −1 diffraction orders.
13. The method according to claim 1 , wherein said positive (+) and negative (−) diffraction orders includes higher diffraction orders.