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:
grouping multiple layers of a semiconductor production flow, the layers for each group using a same reticle technology or process for patterning of a corresponding reticle pattern and/or having differences in reticle transmission or reflection of a corresponding reticle pattern formed on a transmissive or reflective reticle, respectively (RT) less than a predetermined value;
ordering the layers according to an order of the semiconductor production flow, identifying as consecutive layers each two layers for which the second layer comes after the first layer in the layer order and for which the overlay error between the two layers must not exceed a predetermined value;
placing the layers on plural 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 on the reticles of the reticle set for overlay by rearranging the layers to create chains of consecutive critical layers that are placed in the same image field on different reticles; and
optimizing placement of the critical layers for overlay by simultaneously, with the creation of the one or more chains of consecutive critical layers, minimizing the difference between indices corresponding to the layer order between layers in same reticles.
2. The method according to claim 1 , the method comprising optimizing placement of the layers for overlay by maximizing a length of one or more chains of consecutive layers that are placed in a same image field on different reticles.
3. The method according to claim 1 , the method comprising optimizing placement of the layers for overlay by creating one or more chains of consecutive layers that are placed in a same image field or in one or more image fields that are rotated by one or more angles relative to the same image field.
4. The method according to claim 3 , wherein the one or more chains of consecutive layers are at one or more positions corresponding to a position of the same image field with respect to rotation by the one or more angles around a center point of the reticle.
5. The method according to claim 4 , wherein the percentage of the one or more chains of consecutive layers in the same image field is 67%.