Mask alignment scheme for laterally and totally dielectrically isolated integrated circuits

Claim 3

The method according to claim 1 wherein each leg of said X is formed by two spaced parallel lines and said adjusting step positions said corners of said rectangle in the space between said parallel lines.

Claim 4

In a process for fabricating dielectrically isolated islands on a substrate including masking a first surface of a starting material to expose moat areas, etching said exposed areas to form said islands of starting material an insulating layer on the surface of said starting material and moats, overfilling said moats with a support material, removing portions of said starting material from a second surface opposite said first surface sufficiently to expose said support material at a new second surface, and forming devices in the new second surface of said starting material, the improvement comprising a mask alignment indicia formed and aligned by: forming a rectangular aperture in said mask to expose an indicia area on said first surface of said starting material; etching said exposed indicia area to form an indicia hole; overfilling said indicia hole with said support material; removing said starting material from said second surface sufficiently to expose a rectangle of said support material of said indicia hole at said new second surface; forming an X indicia on a mask used to form said devices in said second surface, the legs of said X represent the diagonals of said rectangle; and aligning said mask and said substrate by positioning the legs of said X on the four corners of said rectangle.

Claim 5

In a process for fabricating dielectrically isolated islands on a substrate including masking a first surface of a starting material to expose moat areas, etching said exposed areas to form said islands of starting material an insulating layer on the surface of said starting material and moats, overfilling said moats with a support material, removing portions of said starting material from a second surface opposite said first surface sufficiently to expose said support material at a new second surface, and forming devices in the new second surface of said starting material, the improvement comprising a mask alignment indicia formed and aligned by: forming a rectangular aperture in said mask to expose an indicia area on said first surface of said starting material; etching said exposed indicia area to form an indicia hole; overfilling said indicia hole with said support material; removing said starting material from said second surface sufficiently to expose a rectangle of said support material of said indicia hole at said new second surface; forming an X indicia on a mask used to form said devices in said second surface, the legs of said X represent the diagonals of said rectangle; and aligning said mask and said substrate by positioning the legs of said X on the four corners of said rectangle.

Claim 6

The process according to claim 3 wherein said aperture is square and said resulting exposed support material of said indicia hole is square.

Claim 7

The process according to claim 4 wherein said starting material has a crystal orientation resulting in an anisotropic etch.

Claim 8

The process according to claim 3 wherein said X is formed from the area between adjacent sides of four orthogonally aligned triangles with adjacent apex.

Claim 9

The process according to claim 6 wherein said aligning positions the four corners in the area between the sides of said triangles.

Claim 10

In a process for fabricating laterally dielectrically isolated islands in a first layer on a substrate including masking a first surface of said first layer to expose moat areas, etching said exposed areas to form said islands of said first layer, forming an insulating layer on the surface of said moats, overfilling said moats with fill material, removing said fill material down to the surface of said first layer and forming devices in the surface of said first layer, the improvement comprising a masking alignment indicia formed and aligned by: forming a rectangular aperture in said mask to expose an indicia area on said first surface of said first layer; etching said exposed indicia area to form an indicia hole; overfilling said indicia hole with said fill material; removing said fill material down to said surface of said first layer to form a rectangular fill material indicia in the surface of said first layer; forming an X indicia on a mask used to form said devices in said second surface, the legs of said X represent the diagonals of said rectangle; and aligning said mask and said substrate by positioning the legs of said X on the four corners of said rectangle.

Claim 11

In a process for fabricating laterally dielectrically isolated islands in a first layer on a substrate including masking a first surface of said first layer to expose moat areas, etching said exposed areas to form said islands of said first layer, forming an insulating layer on the surface of said moats, overfilling said moats with fill material, removing said fill material down to the surface of said first layer and forming devices in the surface of said first layer, the improvement comprising a masking alignment indicia formed and aligned by: forming a rectangular aperture in said mask to expose an indicia area on said first surface of said first layer; etching said exposed indicia area to form an indicia hole; overfilling said indicia hole with said fill material; removing said fill material down to said surface of said first layer to form a rectangular fill material indicia in the surface of said first layer; forming an X indicia on a mask used to form said devices in said second surface, the legs of said X represent the diagonals of said rectangle; and aligning said mask and said substrate by positioning the legs of said X on the four corners of said rectangle.

Claim 12

The process according to claim 8 wherein said aperture is square and said resulting indicia is square.

Claim 13

The process according to claim 9 wherein said starting material has a crystal orientation resulting in an anisotropic etch.

Claim 14

The process according to claim 8 wherein each leg of said X indicia is formed by two spaced parallel lines and said aligning step positions said corners of said rectangle in the space between said parallel lines.