Semiconductor device manufacturing: process – Chemical etching – Combined with the removal of material by nonchemical means
Reexamination Certificate
2000-05-22
2001-03-27
Powell, William (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Combined with the removal of material by nonchemical means
C156S345420, C216S088000, C438S745000
Reexamination Certificate
active
06207572
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of chemical mechanical polishing. More particularly, the present invention relates to a method and apparatus for polishing a semiconductor wafer to a high degree of planarity and uniformity. This is achieved when the semiconductor wafer is polished with pads at high bi-directional linear or reciprocating speeds.
BACKGROUND OF THE INVENTION
Chemical mechanical polishing (CMP) of semiconductor wafers for VLSI and ULSI applications has important and broad application in the semiconductor industry. CMP is a semiconductor wafer flattening and polishing process that combines chemical removal of semiconductor layers such as insulators, metals, and photoresists with mechanical buffering of a wafer surface. CMP is generally used to flatten/polish wafers after crystal growing during the wafer fabrication process, and is a process that provides global planarization of the wafer surface. For example, during the wafer fabrication process, CMP is often used to flatten/polish the profiles that build up in multilevel metal interconnection schemes. Achieving the desired flatness of the wafer surface must take place without contaminating the desired surface. Also, the CMP process must avoid polishing away portions of the functioning circuit parts.
Conventional systems for the chemical mechanical polishing of semiconductor wafers will now be described. One conventional CMP process requires positioning a wafer on a holder rotating about a first axis and lowered onto a polishing pad rotating in the opposite direction about a second axis. The wafer holder presses the wafer against the polishing pad during the planarization process. A polishing agent or slurry is typically applied to the polishing pad to polish the wafer. In another conventional CMP process, a wafer holder positions and presses a wafer against a belt-shaped polishing pad while the pad is moved continuously in the same linear direction relative to the wafer. The so-called belt-shaped polishing pad is movable in one continuous path during this polishing process. These conventional polishing processes may further include a conditioning station positioned in the path of the polishing pad for conditioning the pad during polishing. Factors that need to be controlled to achieve the desired flatness and planarity include polishing time, pressure between the wafer and pad, speed of rotation, slurry particle size, slurry feed rate, the chemistry of the slurry, and pad material.
Although the CMP processes described above are widely used and accepted in the semiconductor industry, problems remain. For instance, there remains a problem of predicting and controlling the rate and uniformity at which the process will remove materials from the substrate. As a result, CMP is a labor intensive and expensive process because the thickness and uniformity of the layers on the substrate surface must be constantly monitored to prevent overpolishing or inconsistent polishing of the wafer surface.
Accordingly, an inexpensive and more consistent method and apparatus for polishing a semiconductor wafer are needed.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method and apparatus that polishes a semiconductor wafer with uniform planarity.
It is another object of the present invention to provide a method and apparatus that polishes a semiconductor wafer with a pad having high bi-directional linear or reciprocating speeds.
It is yet another object of the present invention to provide a method and apparatus that reduces the size of the polishing station thereby reducing the space and cost of such station.
It is another object of the present invention to provide a method and apparatus that eliminates or reduces the need for pad conditioning.
It is yet another object of the present invention to provide a method and apparatus for efficiently loading and unloading a semiconductor wafer onto a wafer housing.
These and other objects of the present invention are obtained by providing a method and apparatus that polishes a wafer with a pad having high bi-directional linear speeds. In summary, the present invention includes a polishing pad secured to a timing belt mechanism that allows the pad to move in a reciprocating manner, i.e. in both forward and reverse directions, at high speeds. The constant forward and reverse movement of the polishing pad as it polishes the wafer provides superior planarity and uniformity across the wafer surface. The wafer housing of the present invention can also be used to securely hold the wafer as it is being polished.
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Nutool, Inc.
Pillsbury Winthrop LLP.
Powell William
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