Patent ID: 7052464

Claim:
An alignment method comprising the following steps: laying out a pattern representing a hexagonal arrangement of cMUT elements having axes of symmetry, said laid-out pattern comprising a first set of graphical data; processing said first set of graphical data to rotate said pattern by a predetermined angle relative to a fixed rectilinear frame of reference having two mutually orthogonal axes, said predetermined angle being selected so that an axis of symmetry of said hexagonal arrangement of hexagonal cMUT elements is aligned with an axis of a first fixed rectilinear frame of reference; laying out a first alignment key having an axis aligned with an axis of said fixed first rectilinear frame of reference, said laid-out alignment key comprising a second set of graphical data; transferring said rotated pattern and said first alignment key to a mask; and placing said mask over a substrate comprising a hexagonal arrangement of CMOS cells having axes of symmetry respectively aligned with the axes of a second fixed rectilinear frame of reference, and a second alignment key having an axis aligned with an axis of said second fixed rectilinear frame of reference, said mask being placed so that said first alignment key is aligned with said second alignment key.