Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With microwave gas energizing means
Reexamination Certificate
1999-03-18
2001-11-13
Hiteshew, Felisa (Department: 1765)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With microwave gas energizing means
C438S691000, C118S300000
Reexamination Certificate
active
06315858
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a gas polishing apparatus having a gas nozzle device to produce a flat surface by removing surface structures on a workpiece such as semiconductor wafer using a reactive gas, or conversely, to fabricate a given surface structure on the work surface.
2. Description of the Related Art
As the density of circuit integration in semiconductor devices becomes ever higher, circuit patterns are becoming finer and interline spacing narrower. Accompanying this trend, the depth of focus become very shallow in photolithographic reproduction of circuit patterns, and it requires that the surface of the wafer placed at the focal plane of a stepper must be microscopically flat to produce the required degree of image sharpness.
A method of producing such a flat surface on a wafer is known as a chemical mechanical polishing (CMP) in which a work surface of a wafer which is held in a wafer holding device is pressed and rotated against an abrading surface of a polishing table while supplying a polishing solution at the abrading interface.
However, the CMP process is designed to produce flatness by polishing the entire surface of a wafer as a whole, and therefore, it is not suitable for removing macroscopic surface irregularities, such as those shown in
FIG. 25
, and results in removal of much quantity of material and is thus time-consuming.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a polishing apparatus and a polishing method to replace or to be used in association with a conventional chemical mechanical polishing method to produce a high quality flat surface in a more efficient manner.
The first aspect of the present invention is a nozzle device, disposed to face a work surface of a workpiece, for performing gas polishing by ejecting a reactive polishing gas to the work surface comprising: a nozzle assembly comprising nozzles having a plurality of differing diameters; and a nozzle selection device for selecting an operative nozzle having a desired diameter from the nozzle assembly and ejecting the polishing gas through a selected nozzle.
Thus, a proper nozzle diameter can be selected to form a proper diameter of gas flow suitable for providing a proper gas polishing condition required for respective workpieces.
The nozzle assembly may include a nozzle plate provided with the nozzles having a plurality of differing diameters, and a valving device disposed rotatably relative to the nozzle plate for selectively operating one nozzle for ejecting the polishing gas.
Another aspect of the present invention is a nozzle device, disposed to face a work surface of a workpiece, for performing gas polishing by ejecting a reactive polishing gas from a nozzle to the work surface, wherein the nozzle includes a nozzle diameter varying device for varying a diameter of a nozzle opening for ejecting the polishing gas.
Still another aspect of the present invention is a nozzle device for ejecting a reactive polishing gas towards a work surface of a workpiece, comprising: a nozzle assembly including a plurality of nozzles arranged at a specific spacing; and a flow control device to adjust individual gas flow through each of the nozzles.
When the workpiece is placed in a reduced pressure polishing chamber, such a nozzle device enables adjustment of the pressure, flow speed, flow volume, and polishing duration individually for each of the plurality of nozzles to correspond to the degree of polishing required in each location on the work surface. This approach permits a given area of the work surface to be processed at one time.
The amount of material to be removed can be predetermined by measuring the fine surface structures of the workpiece and computing the respective amounts. A remote sensor may be provided at the tip of each nozzle to measure the surface structure and the polishing requirements can be determined in real-time to adjust the flow conditions while performing the gas polishing process described above.
It is preferable to increase the profile shaping capability of the nozzle device by performing polishing of local areas on the work surface, therefore, the nozzle shape and diameter should be chosen to suit the local polishing requirements. For example, in order to avoid affecting areas other than a targeted area, an exhaust opening may be provided near the gas exit. Also, for a similar purpose, nozzles may be operated intermittently to produce pulsed ejection to improve the control over the amount of gas ejected in a pulsed mode.
The nozzles may be distributed over an area corresponding to the entire surface of the work surface. In such a case, the entire surface of the work surface can be polished in one operation. The nozzles may also be distributed over an area corresponding to a sector of the workpiece. Such a structure of the nozzle device will enable complete polishing of a work surface in a number of stages equaling the number of sectors.
The flow control device may have a valve for each nozzle to individually close or open the gas supply tubes which supply a polishing gas, and the valve may be provided integrally with the nozzle assembly. This design minimizes the amount of residual gas trapped in the space between the shutter disc and the nozzle end to improve control precision.
The nozzle assembly may be provided with a nozzle position adjusting device to adjust a spacing between the nozzles. Accordingly, the nozzle separation distance can be adjusted to suit the polishing parameters such as the size of the workpiece, polishing conditions and purpose of polishing to perform polishing optimized to local requirements.
In the nozzle device, the nozzles may be separated by a distance D given by a relation: 0.9d/1.177<D≧1.1d/1.177 where d is half of a width of a recess profile produced by a single nozzle. Such a design produces a flat bottom in the etched profile so that a large area of the work surface may be processed efficiently.
The nozzle spacing D may be selected such that D<d/1.177 where d is half of a width of a recess structure produced by a single nozzle. By using a nozzle device of such a design, the surface profile produced by a nozzle assembly is deeper than that produced by the single nozzle. Therefore when the sizes of the surface irregularities are large, D<d/1.177 should be used. For a nozzle spacing D′ for processing even a larger area, a relation be such that D′=d′/1.177 (±10%) where d′is half of the width for a single nozzle. Under these conditions, a deeply etched area of a large diameter having a flat bottom can be produced.
The nozzles may be distributed in a plane such that each nozzle forms an apex of an equilateral triangle. By so doing, the distance between the adjacent nozzles becomes equal so that uniform polishing can be performed effectively.
The flow control device may have a valve for individually closing or opening gas supply tubes for supplying the polishing gas to each nozzle, and the valve may be provided in proximity to the nozzle assembly. This design minimizes the amount of residual gas trapped in the space between the valve and the nozzle end to improve control precision.
The polishing apparatus described above may be combined with an associated mechanical chemical polishing device. Such an apparatus enables production of a localized polishing of a work surface to polish surface structures or to prepare the work surface for their removal, and then the gas polished work surface can be subjected to a CMP process to remove residual irregularities. The combined approach will enable efficient attainment of a high degree of flatness on a workpiece.
Another embodiment of the present invention is a method for polishing a work surface of a workpiece comprising the steps of: placing a plurality of nozzles to face the work surface; and performing polishing by periodically flowing a specific amount of a reactive polishing gas in pulsed modes through nozzles while controlling a flow rate of the polishing
Fukunaga Akira
Kobayashi Yo-ichi
Miyoshi Kaori
Shinozuka Shyuhei
Deo Duy-Vu
Ebara Corporation
Hiteshew Felisa
Wenderoth , Lind & Ponack, L.L.P.
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