US 6,020,263 AGranted

Method of recovering alignment marks after chemical mechanical polishing of tungsten

AssigneeTaiwan Semiconductor Manufacturing Company, Ltd.

InventorsTsu Shih, Chen-Hua Yu

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Abstract

This invention describes a method of forming alignment marks which will be preserved after contact holes in a dielectric have been filled with barrier metal and contact metal and the wafer has been planarized. The alignment marks are formed by filling alignment lines, formed in the dielectric when the contact holes are formed, with barrier metal and contact metal. The alignment lines and contact holes are filled with metal at the same time. After the wafer has been planarized, using a method such as chemical mechanical polishing, a small thickness of the dielectric is etched back using vertical dry anisotropic etching which will not remove either the contact metal or barrier metal. This leaves barrier metal and contact metal extending above the plane of the dielectric forming alignment marks. These alignment marks are preserved after subsequent processing steps, such as deposition of a layer of electrode metal.

Claims18

Dependent claims

A method of forming alignment marks, comprising the steps of:

providing a semiconductor wafer having a primary surface;
providing alignment regions within said semiconductor wafer;
providing integrated circuit regions within said semiconductor wafer;
forming a layer of dielectric, having a first thickness, on said primary surface of said semiconductor wafer wherein said layer of dielectric covers said alignment regions of said semiconductor wafer and said layer of dielectric covers said integrated circuit regions of said semiconductor wafer;
forming alignment lines in that part of said layer of dielectric covering said alignment regions of said semiconductor wafer;
forming contact holes in that part of said layer of dielectric covering said integrated circuit regions of said semiconductor wafer;
forming a layer of barrier metal over said semiconductor wafer after forming said alignment lines and said contact holes in said layer of dielectric;
forming a layer of contact metal over said semiconductor wafer after forming said layer of barrier metal over said semiconductor wafer;
removing that part of said layer of barrier metal, that part of said layer of contact metal, and that part of said layer of dielectric which is greater than a first distance above said primary surface of said semiconductor wafer, wherein said first distance is less than said first thickness, thereby leaving said barrier metal and said contact metal only in said alignment lines and said contact holes;
and
back etching a second thickness from that part of said layer of dielectric covering said alignment regions of said semiconductor wafer without removing any part of said barrier metal or said contact metal filling said alignment lines, wherein said second thickness is between about 1000 and 1400 Angstroms and is less than said first distance, thereby leaving part of said barrier metal and said contact metal extending said second thickness above said layer of dielectric forming alignment marks.

8 more elements

A method of forming photoresist masks, comprising the steps of:

providing a semiconductor wafer having a primary surface;
providing alignment regions within said semiconductor wafer;
providing integrated circuit regions within said semiconductor wafer;
forming a layer of dielectric, having a first thickness, on said primary surface of said semiconductor wafer wherein said layer of dielectric covers said alignment regions of said semiconductor wafer and said layer of dielectric covers said integrated circuit regions of said semiconductor wafer;
forming alignment lines in that part of said layer of dielectric covering said alignment regions of said semiconductor wafer;
forming contact holes in that part of said layer of dielectric covering said integrated circuit regions of said semiconductor wafer;
forming a layer of barrier metal over said semiconductor wafer after forming said alignment lines and said contact holes in said layer of dielectric;
forming a layer of contact metal over said semiconductor wafer after forming said layer of barrier metal over said semiconductor wafer;
removing that part of said layer of barrier metal, that part of said layer of contact metal, and that part of said layer of dielectric which is greater than a first distance above said primary surface of said semiconductor wafer, wherein said first distance is less than said first thickness, thereby leaving said barrier metal and said contact metal only in said alignment lines and said contact holes;
back etching a second thickness from that part of said layer of dielectric covering said alignment regions of said semiconductor wafer without removing any part of said barrier metal or said contact metal filling said alignment lines, wherein said second thickness is between about 1000 and 1400 Angstroms and is less than said first distance, thereby leaving part of said barrier metal and said contact metal extending said second thickness above said layer of dielectric forming alignment marks;
forming a layer of photoresist on said semiconductor wafer after forming said alignment marks;
providing a projection stepper;
providing a projection mask having a pattern;
exposing said pattern in said layer of photoresist formed on said semiconductor wafer using said projection stepper, said projection mask, and said alignment marks wherein said alignment marks are used to align said pattern to said semiconductor wafer;
and
developing said layer of photoresist thereby forming a photoresist mask having said pattern.

13 more elements

Dependencies are inferred from the claim text.