Structure and method to improve overlay performance in semiconductor devices
In an exemplary method, a first layer is formed on a substrate. First overlay marks are formed in a first zone of the first layer. A non-transparent layer is formed on top of the first layer. At least a portion of the non-transparent layer is removed from an area above the first zone of the first layer. This provides optical access to the first overlay marks. A second layer is formed on top of the non-transparent layer. Second overlay marks are formed in a second zone of the second layer. Position information is obtained from each of the first overlay marks and the second overlay marks.
1. A multilayer device, comprising:
a substrate having a top surface and a bottom surface;
a first layer on top of the substrate, the first layer having a top surface and a bottom surface, wherein the bottom surface of the first layer contacts the top surface of the substrate, and wherein first overlay marks are located in a first zone of the first layer;
first intermediate layers on top of the first layer and the first overlay marks, each of the first intermediate layers having a top surface and a bottom surface, wherein the bottom surface of each layer contacts the top surface of an adjacent layer;
a non-transparent layer on top of the first intermediate layers, the non-transparent layer having a top surface and a bottom surface, wherein the bottom surface of the non-transparent layer contacts the top surface of the first intermediate layers;
a window located in a preselected area of the non-transparent layer, the preselected area being vertically aligned on the first zone of the first layer;
second intermediate layers on top of the window and the non-transparent layer, each of the second intermediate layers having a top surface and a bottom surface, wherein the bottom surface of each layer contacts the top surface of an adjacent layer; and
a second layer on top of the second intermediate layers, the second layer having a top surface and a bottom surface, wherein the bottom surface of the second layer contacts the top surface of the second intermediate layers, and wherein second overlay marks are located in a second zone of the second layer,
wherein the first overlay marks and the second overlay marks provide position information for structural features on the substrate.
2. The multilayer device according to claim 1 , wherein the non-transparent layer comprises a metal layer.
3. The multilayer device according to claim 1 , wherein the widow is filled with an interlayer dielectric material.
4. The multilayer device according to claim 1 , wherein the first overlay marks and the second overlay marks are made of different materials.
5. The multilayer device according to claim 1 , wherein the first overlay marks and the second overlay marks have different patterns.
6. The multilayer device according to claim 1 , wherein the first overlay marks and the second overlay marks provide position information by balancing optical contrast intensity between the first overlay marks and the second overlay marks.