Regeneration of chemical mechanical polishing pads in-situ

Details Regeneration of chemical mechanical polishing pads in-situ Regeneration of chemical mechanical polishing pads in-situ

1999-06-11

2001-10-02

Gulakowski, Randy (Department: 1746)

Cleaning and liquid contact with solids

Processes

Including regeneration, purification, recovery or separation...

C134S004000, C134S005000, C134S012000, C216S002000, C438S690000, C438S691000, C438S692000, C438S693000, C451S061000, C451S307000, C451S548000

Reexamination Certificate

active

06296717

ABSTRACT:

FIELD OF THE INVENTION
This invention is related generally to a method and a structure for chemically-mechanically polishing (CMP) the surface of a wafer, and more particularly, to a method of resurfacing and remolding in-situ a pad used for planarizing the surface of the wafer to eliminate the problem of pad aging due to extended use.
BACKGROUND OF THE INVENTION
In the Chemical Mechanical Polishing process, the surface of a semiconductor wafer is removed by holding the face of the wafer against a moving polishing pad coated with slurry (Note: a pad is a material that protects the surface of the polishing tool and facilitates the movement of the slurry underneath the wafer, while conforming itself to the surface of the wafer). With time, the surface of the pad produces changes which affect the polishing rate, uniformity, and defect densities on the wafer. To overcome the degradation in the surface properties of the pad, many of the pads used in the CMP process require conditioning, i.e., abrading and washing the surface of the pad to expose a fresh surface for polishing. However, the bulk properties affecting the ability of the pad to planarize a wafer change as the pad becomes thinner. Polishing each wafer on a freshly generated pad reduces wafer to wafer variability; however, it is unrealistic to change pads after each wafer due to the cost and tool down time.
Etchants have been used in the art to selectively planarize certain areas of a wafer, as described for instance in U.S. Pat. No. 5,348,615 to Gupta. Yet, such an approach is inadequate for the more versatile chemical mechanical polishing process which ideally requires a combination mechanical abrasive components as well as the chemical component (chemical components are not solely etchants), as will be described hereinafter when describing the present invention, and more specifically for supplying slurry for CMP, which by their inherent nature are not limited to localized sub-micron scale areas.
Several attempts have been tried in the past to achieve the stated goal as, for instance, in U.S. Pat. No. 5,283,989 to Hisasue et al. Therein is described the formation of ice particles used as an abrasive agent. Such a material lacks the necessary properties required to incorporate the abrasive component normally found in slurry to become pad material to regenerate the pad itself.
Mechanical grinding has, oftentimes, been successfully used to regenerate the surface of an object, as described, e.g. in U.S. Pat. No. 4,785,587 to Reich et al. However, this approach suffers from serious drawbacks, as for instance, by introducing micro-fractures which render the surface of the wafer unusable. Further, mechanical grinding by itself possesses certain disadvantages by not being simultaneously combined with chemical reaction, as required by CMP. Moreover, a mechanical approach is unable by itself to regenerate the resurfacing material between uses and to liquefy the binder for the polishing abrasive during use, although it would be equally acceptable for the pad to remain solid during the polishing process and then be resurfaced and refreshed by a process unrelated to the wafer polish before subsequent wafers are processed.
OBJECT OF THE INVENTION
Accordingly, it is an object of the invention to regenerate the surface of a polishing pad used for a CMP process.
It is another object of the invention to regenerate the surface by first depositing a liquid material onto the polishing table, by reducing the temperature of the material to a point where solidification takes place, and by using the solidified material as the polishing surface for the wafer.
It is a further object of the invention to quickly, easily and repeatably, resurface and refresh the surface of an object which requires polishing without introducing micro-fracture defects.
It is yet another object to achieve consistency and planarity of the surface by periodically removing some or all the material followed by redepositing additional material to maintain a fresh surface at all times.
It is still another object of the invention to generate a new surface without abrasive conditioning as performed today to eliminate concerns with pad contamination that can introduce defects.
It is a more particular object to use regenerated pads to reduce polisher downtime as pads could be fed continuously to the tool by bulk distribution, typical, as to what is used for slurry.
SUMMARY OF THE INVENTION
In one aspect of the invention, there is provided a method for remolding a chemical-mechanical polishing pad (CMP), the pad having a resilient, planar polishing surface, made of a material which is moldable at elevated temperatures.
The resilient, planar surface is characterized by having abrasives embedded therein, which becomes moldable at elevated temperatures.
In another aspect of the invention there is provided a method for regenerating in-situ a chemical mechanical pad that includes the steps of providing a liquid moldable material such as wax; filling a polish pad mold with liquid moldable material; and reducing the temperature to allow the moldable material to harden.
In essence, the core of the invention is to quickly, easily and repeatably resurface and refresh the surface on which the semiconductor wafer is to be polished by melting the top layer of the pad as a way of supplying slurry to the pad.


REFERENCES:
patent: 5692947 (1997-12-01), Talieh et al.
patent: 6022268 (2000-02-01), Roberts et al.
patent: 6099394 (2000-08-01), James et al.
patent: 11-151659 (1999-06-01), None

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