High resistance ionic current source
AssigneeNovellus Systems, Inc.
InventorsSteven T. Mayer, Jonathan D. Reid
Life of this patent
Estimating the term…
Abstract
A substantially uniform layer of a metal is electroplated onto a work piece having a seed layer thereon. This is accomplished by employing a “high resistance ionic current source,” which solves the terminal problem by placing a highly resistive membrane (e.g., a microporous ceramic or fretted glass element) in close proximity to the wafer, thereby swamping the system's resistance. The membrane thereby approximates a constant current source. By keeping the wafer close to the membrane surface, the ionic resistance from the top of the membrane to the surface is much less than the ionic path resistance to the wafer edge, substantially compensating for the sheet resistance in the thin metal film and directing additional current over the center and middle of the wafer.
Claims28
An apparatus for electroplating a substantially uniform layer of metal onto a conductive seed layer of a work piece surface having edge regions around a center region, the apparatus comprising:
- a) a plating chamber;
- b) a work piece holder for holding the work piece in the plating chamber at a position in alignment with an anode;
- c) electrical contacts arranged to make electrical connection to the seed layer at one or more locations on the edge regions;
- and
- d) an ionically resistive ionically permeable element configured for improving plating uniformity, the element having a porosity of 5% or less, and a thickness of between about 5 and 25 millimeters, wherein the element is positioned to have one surface facing the work piece surface, and located within about 5 millimeters of said work piece surface, when held in plating position by the work piece holder, and an opposite surface facing the anode during plating in the plating chamber, wherein the element does not increase the overall resistance of a plating system by more than 5 Ohms.
An apparatus for electroplating a substantially uniform layer of metal onto a conductive seed layer of a work piece surface having edge regions around a center region, the apparatus comprising:
- a) a plating chamber;
- b) a work piece holder for holding the work piece in the plating chamber at a position in alignment with an anode;
- c) electrical contacts arranged to make electrical connection to the seed layer at one or more locations on the edge regions;
- d) an ionically resistive ionically permeable element, configured for improving plating uniformity, wherein the element is positioned to have one surface facing the work piece surface, and located within about 5 millimeters of said work piece surface, when held in plating position by the work piece holder, and an opposite surface facing the anode during plating in the plating chamber, wherein the anode comprises at least two separate anode segments, controlled independently of one another, wherein the ionically resistive ionically permeable element has a porosity of 5% or less, and a thickness of between about 5 and 25 millimeters;
- (e) an insulating focusing wall around at least one of the anode segments, the wall focusing current from said anode segment in an electrolyte provided between the work piece and said anode segment during electroplating, wherein the wall is configured to confine ionic current from said anode segment and to limit interactions between anode segments.
An apparatus for electroplating a substantially uniform layer of metal onto a conductive seed layer of a work piece surface having edge regions around a center region, the apparatus comprising:
- a) a plating chamber;
- b) a work piece holder for holding the work piece in the plating chamber at a position in alignment with an anode;
- c) electrical contacts arranged to make electrical connection to the seed layer at one or more locations on the edge regions;
- d) an ionically resistive ionically permeable element, wherein the element is positioned to have one surface facing the work piece surface, and located within about 5 millimeters of said work piece surface, when held in plating position by the work piece holder, and an opposite surface facing the anode during plating in the plating chamber, wherein the ionically resistive ionically permeable element has a porosity of 5% or less, and a thickness of between about 5 and 25 millimeters;
- e) an iris, configured for dynamic movement during electroplating and positioned to restrict ionic current proximate the edge regions of the work piece surface to varying degrees during the course of electroplating.
Dependencies are inferred from the claim text.