U.S. patent application number 09/302392 was filed with the patent office on 2001-06-07 for method and apparatus for reducing non-uniformity area effects in the manufacture of semiconductor devices.
Invention is credited to SCHULZE, STEFFEN, ZACH, FRANZ.
Application Number | 20010003033 09/302392 |
Document ID | / |
Family ID | 23167560 |
Filed Date | 2001-06-07 |
United States Patent
Application |
20010003033 |
Kind Code |
A1 |
SCHULZE, STEFFEN ; et
al. |
June 7, 2001 |
METHOD AND APPARATUS FOR REDUCING NON-UNIFORMITY AREA EFFECTS IN
THE MANUFACTURE OF SEMICONDUCTOR DEVICES
Abstract
The non-uniformity edge effect that can affect the quality of
chips near the edge of a semiconductor wafer of various steps in
the manufacture of integrated circuits is reduced. This is achieved
by increasing the field area exposed by a step and repeat printer
only when printing squares for chips located near the wafer edge.
As a result there is also printed for processing an additional
non-functional area outside the functional area to reduce the
non-uniformity effect. This increases throughput of the printing
apparatus.
Inventors: |
SCHULZE, STEFFEN;
(WAPPINGERS FALLS, NY) ; ZACH, FRANZ; (WAPPINGERS
FALLS, NY) |
Correspondence
Address: |
SIEMENS CORPORATION
INTELLECTUAL PROPERTY DEPARTMENT
186 WOOD AVENUE SOUTH
ISELIN
NJ
08830
|
Family ID: |
23167560 |
Appl. No.: |
09/302392 |
Filed: |
April 30, 1999 |
Current U.S.
Class: |
430/311 ;
430/396 |
Current CPC
Class: |
G03F 7/70433 20130101;
G03F 7/70425 20130101; G03F 7/70066 20130101 |
Class at
Publication: |
430/311 ;
430/396 |
International
Class: |
G03F 007/20 |
Claims
What is claimed is:
1. A method for the step and repeat printing of squares on a
circular semiconductive wafer that comprises the step of adjusting
the reticle used to control the field exposure area of each square
printed to add extra non-functional exposure field area to the
regular functional 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.
2. The method of claim 1 in which the added field area exposed is
printed in essentially the same pattern as the regular field area
exposed.
3. The method of claim 1 in which, when diced, the wafer is diced
uniformly, thereby excluding in the final dice the area of the
extra exposure.
4. A reticle for use in step-and-repeat printer comprising a main
section that is patterned for patterning functional areas of the
wafer on which the printer is to be done and auxiliary sections
that are patterned for patterning non-functional edge areas of the
wafer.
5. A reticle in accordance with claim 4 in which the pattern
printed on the non-functional area is designed for compensating for
non-uniformity edge effect in subsequent processing of the
wafer.
6. The method of step-and-repeat printing of patterns on
semiconductive wafer for use in the manufacture of integrated
circuit devices that include processing steps that are vulnerable
to an edge effect, said method comprising printing in areas of the
wafer expected to be free of said edge effect a first pattern and
printing in the areas expected to be vulnerable to said effect an
enlarged pattern.
Description
FIELD OF INVENTION
[0001] 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
[0002] 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 dice 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.
[0003] Basic to the processing, is the 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.
[0004] 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
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.
[0005] 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.
[0006] 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.
[0007] It is 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.
[0008] 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 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 remains
fixed during the printing of a wafer.
[0009] 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
[0010] 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 that 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 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.
[0011] 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.
[0012] 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 for
later processing can ameliorate the edge effect in later
processing.
[0013] The invention will be better understood from the following
more detailed description taken with the drawing.
BRIEF DESCRIPTION OF THE DRAWING
[0014] FIG. 1 will be helpful in explaining the wafer edge effect
that the invention seeks to minimize;
[0015] FIG. 2 shows a typical reticle for use in printing a desired
exposure product pattern on a wafer; and
[0016] FIG. 3 shows an example of a reticle including the product
pattern and an extra region of fill pattern for use selectively
when printing squares on a die area that is close to a wafer edge,
to extend the field area exposed into the surplus edge area of the
wafer thereby to overcome the edge effect in later processing and
to make such squares useful without the need for printing
non-functional squares.
DETAILED DESCRIPTION
[0017] FIG. 1 shows a circular wafer 10, typically a slice of
monocrystalline silicon about 8 inches in diameter, over which are
shown printed a series of squares 12 corresponding to the chips to
be diced from the wafer 10. As seen, there are some incomplete
squares that extend beyond the edge of the wafer 10 and so are
non-functional. Additionally, there is a surplus edge region of the
wafer 10 that cannot be used for chips, represented by that
included within the dashed line 14. Squares that extend beyond the
dashed line 14 are also not useable. In addition, there are also
some squares that are wholly within the dashed line 14 but
sufficiently close to the edge that they ordinarily would not be
useable because of the non-uniformity area effects discussed above.
The invention involves using the area outside the fully printed
squares and within the dashed line 14 to reduce the non-uniformity
large area effect on such chip.
[0018] FIG. 2 shows a typical reticle 20 for use in a conventional
step-and-repeat printer used for patterning a standard
all-functional square pattern. The reticle typically includes a
frame 21 that is used to support the patterned mask 22 that
typically is of a size to pattern an area corresponding to a single
die into which the wafer will be diced after most of the wafer
scale processing is done. Generally the reticle will be used with
an exposure tool that comprises a set of blades that are adjusted
to expose as much of the reticle as is needed for the size of the
area being pointed. Generally this setting of the blades is kept
fixed for the printing of the entire wafer.
[0019] FIG. 3 shows a reticle 30 modified for use in the method of
the invention.
[0020] It includes a frame 31 that is used to support a patterned
mask that includes a main section 32 and two auxiliary sections 34A
and 34B that advantageously are spaced from the main section by
narrow corridors 35A and 35B. The main section 32 corresponds to
the area of a fully functional square that is to be printed in
regions free of any edge effects, and when such squares are being
printed, the blades of the exposure tool are set appropriately. The
extra section is patterned much in the manner of the main section
but will be used to print non-functional edge regions. The
patterned areas of the reticle are shown cross-hatched. When the
edges of the wafer are being printed, the setting of the exposure
tool is increased to permit printing of these extra areas. The
narrow unpatterned corridors advantageously are used as guides to
facilitate the dicing of the wafer and may sometimes be
unnecessary.
[0021] In some instances, it may be advantageous to provide extra
fill sections along all four sides rather than two sides as shown.
The exposure tool would then need to be modified appropriately. A
software program would be used to change the blade settings
appropriately.
[0022] It should be noted that there should be distinguished the
situation where there may be printed on the periphery of the wafer
patterns that are useful for alignment or testing proposes.
[0023] By this expediment, it becomes unnecessary to provide extra
unusable squares to pattern non-functional areas to compensate for
the non-uniformity area effect described. It is sufficient merely
to use selectively larger squares when patterning squares at the
wafer edge to overcome the non-uniformity area effect.
[0024] It is to be understood that the specific embodiment
described is merely illustrative of the general principles. For
example the invention should be useable with wafer shapes that are
non circular. Similarly c pattern printed could have various
shaped, and so the term "square" to denote the pattern area printed
in each step is intended to be independent of the shape of the area
being printed in each step.
* * * * *