Marker structure and method for controlling alignment of layers of a multi-layered substrate
The invention includes a lithographic system having a first source for generating radiation with a first wavelength and an alignment system with a second source for generating radiation with a second wavelength. The second wavelength is larger than the first wavelength. A marker structure is provided having a first layer and a second layer. The second layer is present either directly or indirectly on top of said first layer. The first layer has a first periodic structure and the second layer has a second periodic structure. At least one of the periodic structures has a plurality of features in at least one direction with a dimension smaller than 400 nm. Additionally, a combination of the first and second periodic structure forms a diffractive structure arranged to be illuminated by radiation with the second wavelength.
1. A device, comprising:
a wafer positioned on a wafer table of a lithographic apparatus in a position for detecting light reflected off the wafer, the wafer comprising:
a first layer;
a second layer, wherein the second layer is placed over the first layer;
a first periodic structure formed on the first layer; and
a second periodic structure formed on the second layer, wherein at least one of the first periodic structure and the second periodic structure comprises a plurality of features having dimensions smaller than 400 nm and being oriented in at least one direction and wherein the second periodic structure is placed over the first periodic structure to form a diffractive structure.
2. The device according to claim 1 , wherein the diffractive structure is divided into at least a first segment and a second segment, wherein the first and second periodic structures within the first segment are shifted relative to each other in a first predetermined direction by a first predetermined amount and wherein the first and second periodic structures within the second segment are shifted relative to each other in a second predetermined direction by a second predetermined amount.
3. The device according to claim 1 , wherein one of said first and second periodic structures comprises a plurality of apertures.
4. The device according to claim 1 , wherein one of said first and second layers is a device layer with a periodic structure comprising a device structure.
5. The device according to claim 1 , wherein one of said first and second layers is a contact layer with a contact layer periodic structure comprising a plurality of contact holes, the other layer being a device layer with a device layer periodic structure comprising a plurality of gates.
6. The device according to claim 1 , further comprising at least one non-patterned intermediate layer between said first layer and said second layer.