Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Reexamination Certificate
1999-04-30
2001-08-07
Duda, Kathleen (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
C430S311000, C430S396000
Reexamination Certificate
active
06270947
ABSTRACT:
FIELD OF INVENTION
This invention relates to the manufacture of integrated circuit devices, and more particularly, to the manner in which patterns are printed on a semiconductive wafer to define how the wafer will eventually be diced to provide the individual chips in which the integrated circuits are formed.
BACKGROUND OF THE INVENTION
In the manufacture of integrated circuit devices, it is customary to do most of the processing of the devices on a wafer scale in a large wafer, typically many inches in diameter, and after such processing to dive the wafer into individual chips, each typically a square or rectangle in shape and a fraction of an inch on a side, for completion of the final steps of the processing, such as the provision of terminal connections and packaging.
Basic to the processing, is the water use of a step and repeat printer to print, in a layer of photoresist, the appropriate patterns of the various photoresist masks that are used to localize the effect of the many processing steps.
Generally the shape of the wafer being processed is circular, while the shape of the chips after dicing is essentially square or rectangular. Accordingly the area generally printed in each step generally is either a square or a rectangle. It will be convenient in this description to describe the area printed in each step as a square, although it is to be understood that this term as used here in, includes rectangular areas. Because the wafer is circular and the areas exposed by each step are square, there will be a width around the periphery (edge) of the wafer that, if printed, would yield incomplete squares that would be useless as chips. Additionally, there is a region around the wafer edge that is also useless because of a high density there of various forms of defects.
Moreover, presently in the manufacture of state of the art semiconductive devices there are numerous processes, such as electrochemical chemical polishing and some etching, that depend on substantial uniformity over large areas to provide uniform results over the area processed. With such processes, there tends to be a non-uniformity area effect that causes a difference in results with respect to complete squares close to the wafer periphery because of the discontinuity such periphery provides.
To counter these various edge effects, the step and repeat process is often extended to print squares that extend beyond the area free of such effects, even though it is known that these squares will not provide functional chips. Printing these non-functional squares extends the overall exposure time for printing of a wafer and so decreases the throughput of a given exposure machine. Because of the high cost of the exposure machines, this can be a significant extra expense factor in the manufacture of integrated circuits.
It is also a fact that many integrated circuit devices do not utilize the full exposure field of the equipment available. In particular some scanning equipment, such as deep-ultra violet printers, offer large exposure fields for printing chip squares that often cannot be fully used because the final product made has to fit closely the exposure field of tools, used for other processes in the manufacture, that have much smaller exposure fields.
Because of this, printing equipment now available typically includes provision for controlling the field exposure area of the step pattern or square by providing an exposure tool that controls the size of the area printed. This includes use of movable blades that can be adjusted to set the effective field exposure area of the printing reticle just to that needed for the square being printed. This setting generally remains fixed during the printing of a wafer.
The present invention employs a patterning strategy that better copes with the wafer edge problem described by use of the extra exposure area available in such printing equipment.
SUMMARY OF THE INVENTION
The basic strategy of the invention is to use the extra exposure field area generally available in step and repeat printing apparatus to print squares with enlarged patterned areas selectively near the wafer edge. These extend into the useless wafer edge region that will not normally yield useful chips. In particular, an improvement in efficiency is achieved by controlling the blades positioned on the exposure tool of the printer to increase selectively the opening that determines the size of the field area being exposed. When there is printed a square in a region of the wafer that normally would be useless because of the edge effects, the exposure tool selectively is opened wider so that a wider area of the reticle is opened and extra fill pattern is also being printed to include normally non-useable wafer edge area. The inclusion of such enlarged patterned area can be expected to reduce the non-uniformity area edge effect in subsequent vulnerable processing steps and improve the yield of useful chips. Squares of the smaller standard regular product pattern are printed in wafer regions free of the edge effect. As a result, in the case of a printer, although the printing time of such enlarged edge squares is slightly increased because of the extra area being exposed, this extra time should be much less than would have been required to print and process squares that included non-functional edge areas, as has been done in the past, to avoid the non-uniformity edge effect. The extra area included in the enlarged squares along the wafer edge is removed when the wafer is finally diced so that these chips are now of standard size,
Viewed from one aspect, the present invention is directed to a method for the step and repeat printing of squares on a circular semiconductive wafer that comprises the step of adjusting the exposure tool used to control the field exposure area of each square printed to add extra exposure field area to the regular field area of the square selectively at squares exposed adjacent to an edge of the wafer, whereby there is ameliorated area non-uniformity effects in later processing steps of such squares. This extra exposure field area is eliminated when that enlarged square is diced so that there is formed therefrom a chip of the same size as the chips formed from the standard squares.
Viewed from another aspect, the invention is a step-and-repeat printing system that uses a printer with an exposure tool whose setting can be adjusted in the course of printing a product pattern on a wafer. This permits printing extra area of a reticle that is appropriately patterned . This extra pattern is printed in areas of the wafer where such printing can ameliorate the edge effect in later processing.
The invention will be better understood from the following more detailed description taken with the drawing.
REFERENCES:
patent: 3582215 (1971-06-01), Loomis
patent: 4668089 (1987-05-01), Oshida et al.
patent: 5545498 (1996-08-01), Konno
patent: 5811211 (1998-09-01), Tanaka et al.
patent: 5894056 (1999-04-01), Kakizaki et al.
patent: 6027843 (2000-02-01), Kojima et al.
patent: 6040096 (2000-03-01), Kakizaki et al.
Schulze Steffen
Zach Franz
Braden Stanton C.
Duda Kathleen
Infineon - Technologies AG
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