Cross technology reticle (CTR) or multi-layer reticle (MLR) CDU, registration, and overlay techniques
View Patent ↗Methods for reducing reticle transmission differences and for optimizing layer placement for overlay in MTRs and CTRs are disclosed. Embodiments include providing a reticle having a prime area and a frame area surrounding the prime area; determining RT differences across the prime area; and providing RT adjustment structures on the reticle to decrease the RT differences. Other embodiments include grouping multiple layers of a semiconductor production flow, the layers for each group having an RT difference less than a predetermined value; and placing the layers on plural ordered reticles of a reticle set, each reticle having multiple image fields, by selecting, for each reticle, layers from a single group and optimizing placement of the layers for overlay. Other embodiments include selectively rotating image fields on a reticle having multiple image fields to improve overlay, or optimizing placement of DDLs on CTRs by placing each design orientation on a different reticle.
1. A method comprising:
providing a transmissive or reflective reticle having a frame area and a prime area, the frame area surrounding the prime area;
determining differences in RT (reticle transmission or reflection for a transmissive or reflective reticle, respectively) across the prime area; and
providing disposable RT adjustment structures in the prime area in dummy filled regions on the reticle to decrease or increase the RT differences,
wherein the reticle comprises a multilayer reticle (MLR),
wherein determining RT differences comprises determining RT differences between different layers of the MLR, and
wherein the RT is adjusted subsequent to a determination of an average RT tuning of respective layers of the MLR.
2. The method according to claim 1 , wherein RT adjustment elements in the frame area differ in size from RT adjustment elements in the prime area.
3. The method according to claim 1 , wherein:
determining RT differences comprises determining RT differences in different dies of a single image field; and
providing RT adjustment structures comprises providing different numbers of RT adjustment elements in different dies.
4. The method according to claim 3 , wherein providing RT adjustment structures further comprises providing RT adjustment elements at different locations within different dies.
5. The method according to claim 1 , wherein providing RT adjustment structures comprises providing RT adjustment elements in an empty image field.
6. The method according to claim 5 , further comprising providing RT adjustment elements in an area around the prime area of the empty image field.
7. A method comprising:
providing a transmissive or reflective reticle having a frame area and a prime area, the frame area surrounding the prime area;
determining differences in RT (reticle transmission or reflection for a transmissive or reflective reticle, respectively) across the prime area; and
providing disposable RT adjustment structures in the prime area in dummy filled regions on the reticle to decrease or increase the RT differences,
wherein the reticle comprises a cross technology reticle (CTR),
wherein determining RT differences comprises determining RT differences between image fields of different technology nodes on the reticle, and
wherein the RT is adjusted subsequent to a determination of layer pairing.