Balancing planarization of layers and the effect of underlying structure on the metrology signal

A method of fabricating underlying structures in a wafer that balances planarization and optical metrology characteristics, the method comprising:

• fabricating one or more underlying structures with a predetermined design in a wafer, the predetermined design selected to meet planarization objectives and optical metrology objectives, the optical metrology objectives comprising quality of reflected metrology signal,
• planarizing a surface of a layer of the wafer, the planarized surface of the layer of the wafer having planarization characteristics, and
• fabricating a target periodic structure in the wafer;
• wherein the planarization characteristics of the planarized surface of the layer of the wafer meet the planarization objectives and wherein quality of a reflected metrology signal off the target periodic structure meet the optical metrology objectives.

A method of fabricating underlying structures in a wafer that balances planarization and optical metrology characteristics, the method comprising:

• fabricating one or more underlying structures with a predetermined design in a wafer, the predetermined design selected to meet planarization objectives and optical metrology objectives, the optical metrology objectives comprising quality of reflected metrology signal,
• planarizing a surface of a layer of the wafer, the planarized surface of the layer of the wafer having planarization characteristics, and
• fabricating a target periodic structure in the wafer;
• wherein the planarization characteristics of the planarized surface of the layer of the wafer meet the planarization objectives and wherein quality of a reflected metrology signal off the target periodic structure meet the optical metrology objectives;
• and
• wherein the one or more underlying structures in the wafer are underlying periodic structures, the periodicity of the underlying periodic structures positioned perpendicular to the direction of periodicity of the target periodic structure of the wafer.

A method of fabricating underlying structures in a wafer that balances planarization and optical metrology characteristics, the method comprising:

• fabricating one or more underlying structures with a predetermined design in a wafer, the predetermined design selected to meet planarization objectives and optical metrology objectives, the optical metrology objectives comprising quality of reflected metrology signal,
• planarizing a surface of a layer of the wafer, the planarized surface of the layer of the wafer having planarization characteristics, and
• fabricating a target periodic structure in the wafer;
• wherein the planarization characteristics of the planarized surface of the layer of the wafer meet the planarization objectives and wherein quality of a reflected metrology signal off the target periodic structure meet the optical metrology objectives;
• and
• wherein the one or more underlying structures in the wafer comprises a first layer of underlying periodic structure and a second layer of underlying periodic structure, the periodicity of the first layer of underlying periodic structure and the second layer of underlying periodic structure being positioned perpendicular to the direction of periodicity of the target periodic structure of the wafer.

A method of designing underlying structures in a wafer that balances planarization and optical metrology characteristics, the method comprising:

• fabricating underlying structures including one or more random shapes and one or more spaces, the one or more random shapes varying in size and/or shape;
• comparing planarization characteristics of the underlying layers of the wafer to preset standard planarization characteristics;
• fabricating target structures in the target layer of the wafer;
• measuring a reflected metrology signal off a calibration test area of the target layer of the wafer to obtain a calibration metrology signal, the calibration test area having an unpatterned underlying structure;
• and
• selecting an underlying structure of the underlying structures of one or more random shapes that yields a reflected metrology signal off the target structure that is closest to the calibration metrology signal, the selected underlying structure having planarized layers that meet the preset standard planarization characteristics.

A method of designing underlying structures in a wafer that balances planarization and optical metrology characteristics, the method comprising:

• fabricating underlying structures with one or more periodic structures, the one or more periodic structures having one or more lines and one or more spaces in one or more underlying layers of a wafer;
• comparing planarization characteristics of one or more planarized layers of the wafer to preset standard planarization characteristics;
• fabricating target structures in the target layer of the wafer;
• measuring a reflected metrology signal off a calibration test area of the target layer of the wafer to obtain a calibration metrology signal, the calibration test area having an unpatterned underlying structure;
• and
• selecting an underlying structure of the underlying structures with one or more periodic structures that yields a reflected metrology signal off the target structure that is closest to the calibration metrology signal, the selected underlying structure having one or more planarized layers that meet the preset standard planarization characteristics.

A method of selecting an underlying structure design that balances planarization and optical metrology objectives for a target structure, the method comprising:

• fabricating underlying structures in underlying layers of a wafer, the underlying structures designed to balance planarization and optical metrology objectives;
• measuring planarization characteristics of the underlying layers of the wafer;
• fabricating a target structure in a target layer of the wafer;
• measuring optical metrology characteristics of the target structure;
• and
• comparing the planarization characteristics of the underlying layers to the planarization objectives and the optical metrology characteristics of the target structure to the optical metrology objectives.

A system for selecting an underlying structure design that balances planarization and optical metrology objectives for a target structure, the system comprising:

• a wafer fabricator, for fabricating underlying structures in underlying layers of a wafer, the underlying structures designed to balance planarization and optical metrology objectives, and for fabricating target structures in a target layer of the wafer;
• a planarizer for planarizing a surface of one or more layers of the wafer, the planarized surface of the layer of the wafer having planarization characteristics;
• a layer profiler for measuring the planarization characteristics of planarized surfaces of the wafer;
• an optical metrology device for projecting a signal on the target structure in the target layer of the wafer and for processing the reflected signal from the target structure in the target layer of the wafer;
• and
• a design selector for the selecting the design of an underlying structure that yields a reflected metrology signal off the target structure that is closest to the calibration metrology signal and that meets planarization objectives;
• wherein the wafer fabricator fabricating underlying structures in underlying layers of the wafer, the planarizer planarizing the surface of one or more underlying layers of the wafer, the layer profiler measuring the planarization characteristics of planarized surfaces of the wafer, the wafer fabricator fabricating the target structures in the target layer of the wafer, the optical metrology device projecting metrology signals on the target structures in the target layer of the wafer and processing the reflected metrology signals from the target structures, the design selector compares the reflected metrology signal off the target structure to a calibration metrology signal, the calibration metrology signal being the reflected metrology signal off a target structure with an unpatterned underlying layer, and selects a design of the underlying structure that yields a reflected metrology signal that is closest to the calibration metrology signal and where the planarized surfaces of the wafer associated with the selected design of the underlying structure meet the planarization objectives.

A computer-readable storage medium containing computer executable code to select an underlying structure design that balances planarization and optical metrology objectives for a target structure by instructing a computer to operate as follows:

• comparing planarization characteristics of underlying layers of the wafer to preset standard planarization characteristics;
• measuring a reflected metrology signal off a calibration test area of a target layer of the wafer to obtain a calibration metrology signal, the calibration test area having an unpatterned underlying structure;
• and
• selecting a design of an underlying structure, the underlying structure having a target structure that yields a reflected metrology signal off the target structure closest to the calibration metrology signal and having the planarization characteristics of planarized underlying layers meet the preset standard planarization characteristics.