U.S. patent application number 15/295236 was filed with the patent office on 2017-02-02 for substrate processing and alignment.
The applicant listed for this patent is Erich Thallner. Invention is credited to Erich Thallner.
Application Number | 20170033053 15/295236 |
Document ID | / |
Family ID | 38478128 |
Filed Date | 2017-02-02 |
United States Patent
Application |
20170033053 |
Kind Code |
A1 |
Thallner; Erich |
February 2, 2017 |
SUBSTRATE PROCESSING AND ALIGNMENT
Abstract
A substrate can efficiently be manufactured by separating the
alignment and the actual processing when an alignment mark is
provided, which is fixed with respect to the substrate and when
position information on a position of a process area on the
substrate is retrieved with respect to the alignment mark before
the substrate is processed. During the processing alignment can
then be performed by redetermining the position of the alignment
mark only once and by using the stored position information on the
position of the process area.
Inventors: |
Thallner; Erich; (Scharding,
AT) |
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Applicant: |
Name |
City |
State |
Country |
Type |
Thallner; Erich |
Scharding |
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AT |
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Family ID: |
38478128 |
Appl. No.: |
15/295236 |
Filed: |
October 17, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11715525 |
Mar 7, 2007 |
9478501 |
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15295236 |
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60780574 |
Mar 8, 2006 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B82Y 10/00 20130101;
G03F 7/70141 20130101; H01L 23/544 20130101; G03F 9/7076 20130101;
H01L 21/67259 20130101; G03F 9/7046 20130101; G03F 9/7088 20130101;
H01L 21/681 20130101; H01L 2223/54426 20130101; H01L 21/304
20130101; H01L 2924/0002 20130101; H01L 2223/54413 20130101; G03F
7/0002 20130101; B82Y 40/00 20130101; H01L 21/6835 20130101; H01L
2223/54453 20130101; H01L 21/67742 20130101; H01L 2924/00 20130101;
H01L 2924/0002 20130101 |
International
Class: |
H01L 23/544 20060101
H01L023/544; H01L 21/68 20060101 H01L021/68; G03F 7/20 20060101
G03F007/20; H01L 21/677 20060101 H01L021/677; H01L 21/683 20060101
H01L021/683; H01L 21/67 20060101 H01L021/67; H01L 21/304 20060101
H01L021/304 |
Claims
1. A method for manufacturing a device using a substrate, the
method comprising: determining a position of an alignment mark
being fixed with respect to the substrate; determining position
information on the position of a process area with respect to the
alignment mark using information determined within the process area
of the surface of the substrate, and storing the determined
position information as stored position information in a
computer-readable information structure in form of a memory at a
substrate support structure; redetermining the position of the
alignment mark; aligning the position of the process area using
information derived from the redetermined position of the alignment
mark and from the position information on the position of the
process area; and processing the process area; wherein the stored
position information are transferrable together with the
substrate.
2. The method in accordance with claim 1, wherein transferring the
stored position information together with the substrate enables to
separate the aligning process from the processing of the process
area.
3. The method in accordance with claim 1, wherein the stored
position information are transferred anytime between determining
the position of the alignment mark and processing the process
area.
4. The method in accordance with claim 1, wherein the process area
comprises a first process area and a second process area, the
method further comprising: determining the position information on
the position of the first process area and on the position of the
second process area with respect to the alignment mark using
topographic information determined within the process areas of the
surface of the substrate; aligning the position of the first
process area using information derived from the redetermined
position of the alignment mark and from the position information on
the position of the first process area; processing the first
process area; aligning the second process area using information
derived from the position information on the position of the second
process area; and processing the second process area.
5. The method in accordance with claim 4, further comprising: using
a nano-imprinting technique for processing the first process area
and the second process area.
6. The method in accordance with claim 1, further comprising:
storing the determined position information on the position of the
first process area and on the position of the second process
area.
7. The method in accordance with claim 1, further comprising:
storing or transporting the substrate and the alignment mark
between the steps of determining the position of the alignment mark
and redetermining the position of the alignment mark.
8. The method in accordance with claim 1, in which the step of
determining the position of the alignment mark comprises a
detection of mechanical structures within the alignment mark by an
atomic force microscope.
9. The method in accordance with claim 1, further comprising:
providing the alignment mark fixing the substrate to a substrate
support having applied thereon the alignment mark.
10. The method in accordance with claim 9, in which the fixing is
performed by application of a vacuum between the substrate and the
substrate support.
11. The method in accordance with claim 9, in which the fixing of
the substrate to the substrate support is making use of temporal
wafer bonding techniques.
12. The method in accordance with claim 1, further comprising:
generating the alignment mark, on the substrate.
13. The method in accordance with claim 1, in which the step of
determining the position information on the position of the second
area comprises: determining relative position information on a
relative position of the second process area with respect to the
first process area; and deriving the position information on the
position of the second process area using the position information
on the position of the first process area and the relative position
information.
14. The method in accordance with claim 1, in which additional tag
information of a computer-readable information tag associated to
the substrate is stored in the step of storing the position
information, to allow for the association of the stored position
information to the substrate.
15. The method in accordance with claim 1, in which the step of
determining the position information on the position of the first
process area and on the position of the second process area
comprises: identifying the first and the second process area by
comparing the determined information with stored reference
information.
16. The method in accordance with claim 1, in which the
determination of the position information uses optical patterns or
nano-structured surfaces as the information determined within the
process areas of the surface of the substrate.
17. A substrate support structure adapted to allow determination of
position information on a position of a process area on the surface
of a substrate, comprising: a substrate support including an
alignment mark comprising a surface structure or an optical
pattern, the surface structure including information; a substrate,
being reversibly fixed to the substrate support, such that the
substrate is in fixed orientation with respect to the alignment
mark; and a computer-readable information structure in form of a
memory for storing information associated to the substrate, wherein
the stored information comprise determined position information on
the position of a process area with respect to the alignment mark,
and wherein the stored position information are transferrable
together with the substrate.
18. The substrate support structure in accordance with claim 17, in
which information on an absolute position of the alignment mark is
coded within a pattern of the surface structure of the alignment
mark.
19. The substrate support structure in accordance with claim 17, in
which the information comprises structure sizes smaller than 100
nm.
20. An apparatus for processing a substrate, the apparatus
comprising: a calibration unit for determining the position of the
alignment mark; a position measuring unit for determining
information of the surface of the substrate and for deriving the
position information on the position of a process area using
information on the determined position of the alignment mark and
the information determined within the process area, and for storing
the determined position information as stored position information
in a computer-readable information structure in form of a memory at
a substrate support structure, wherein the stored position
information are transferrable together with the substrate; a
processing device for processing the process area; a recalibration
unit for redetermining the position of the alignment mark; and an
alignment unit for performing an alignment of the processing device
and the process area using information derived from the
redetermined position of the alignment mark and from the position
information on the position of the process area.
21. The apparatus in accordance with claim 20, wherein the process
area comprises a first process area and a second process area,
wherein the position measuring unit is configured for determining
information of the surface of the substrate and for deriving the
position information on the position of the first process area and
on the position of the second process area using topographic
information on the determined position of the alignment mark and
the information determined within the process areas; wherein the
processing device is configured for processing the first and the
second process areas; wherein the alignment unit is configured for
performing an alignment of the processing device and the first
process area using information derived from the redetermined
position of the alignment mark and from the position information on
the position of the first process area and for performing an
alignment of the processing device with the second process area
using information derived from the position information on the
position of the second process area.
22. The apparatus in accordance with claim 21, wherein the
processing device is configured for processing the first and the
second process areas using nano-imprinting-techniques.
23. The apparatus in accordance with claim 21, in which the
position-measuring unit is adapted such that the determining of the
position information of the second process area comprises: deriving
a relative position information on a relative position of the
second process area with respect to the position of the first
process area; and deriving the position information on the position
of the second process area using the position information on the
position of the first process area and the relative position
information.
24. The apparatus in accordance with claim 21, in which the
position measuring unit is adapted to derive the position
information on the position of the first process area and on the
position of the second process area by identifying the first and
the second process area comparing the determined information with
stored reference information.
25. The apparatus in accordance with claim 21, in which the
position measuring unit is configured to derive the position
information using optical patterns or nano-structured surfaces as
the information determined within the process areas of the surface
of the substrate.
26. A substrate support structure adapted to allow determination of
position information on a position of a process area on the surface
of a substrate, comprising: a substrate support including an
alignment mark comprising a surface structure or an optical
pattern, the surface structure including information, the substrate
support being configured to reversibly fix a substrate thereto,
such that the substrate is in fixed orientation with respect to the
alignment mark; and a computer-readable information structure in
form of a memory for storing information associated to the
substrate, wherein the stored information comprise determined
position information on the position of a process area with respect
to the alignment mark, and wherein the stored position information
are transferrable together with the substrate.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. Ser. No.
11/715,525, filed Mar. 7, 2007 and claims priority from U.S.
Provisional Patent Application No. 60/780,574, which was filed on
Mar. 8, 2006, both of which are incorporated herein by reference in
its entirety.
TECHNICAL FIELD
[0002] The present invention relates to the processing of
substrates and in particular to a concept for precise and efficient
alignment of substrates with respect to processing units.
BACKGROUND
[0003] Continuing progress in the semiconductor industry is leading
to ever-smaller structures that have to be processed on the surface
of a substrate, such as a silicon wafer. Presently, structures that
are to be processed on the surface of a wafer are transferred to
the wafer by photolithographic methods, i.e. by projecting the
structures through a mask on the wafer surface. This is normally
done using ultra-violet light that allows, due to its short wave
length, the generation of small structures and can at the same time
be used to activate material, such as photo resistive coatings of
the wafer. The desire to further decrease size of the semiconductor
structures thus leads to the problem of projecting structures of
the size of hundreds of nanometers or possibly even of tens of
nanometers to the wafer surface. The transfer of the desired
structure from the mask to the surface of the wafer was
continuously developed and an on-going decrease of structure size
was accomplished in the past using different physical effects, such
as decreasing the structure size using media of high refraction
index in between the mask and the wafer. Nonetheless, the limit of
the optical transfer processes seems to be nearly reached.
[0004] Several different approaches to further decrease the
structure size in the future are discussed. Particularly attractive
are so-called nano-imprinting techniques that achieve the
application of the structures on the waver surface by a printing
technique, comparable to a normal stamp. On the one hand, stamps of
solid material, typically of metal such as nickel, can be applied
to mechanically imprint a structure on the surface. On the other
hand, one may use stamps of soft materials, such as PDMS
(Polydimethylsiloxan), that can transfer Thiole to the surface of
the wafer, which may prevent the surface from chemical etching.
Using nano-imprinting techniques, structure sizes can easily go
down to the nanometer scale, i.e. transistors with gate lengths in
the 10 nm-regime become feasible.
[0005] Typically, the production of a semiconductor device
comprises several consecutive steps of different processes, such as
edging or photolithography, wherein each of the steps has to be
precisely aligned with the preceding step to produce a functional
semiconductor device. It may be noted that also the production of
microscopic mechanical elements on substrates is a field of high
commercial interest and shares the same demands on high alignment
precision of consecutive production steps. It is evident that a
transition to future structures, for example, by nano-imprinting,
will further increase the accuracy demands of the alignment
processes.
[0006] During the processing of a semiconductor device alignment of
the semiconductor with respect to processing devices is normally
required several times during the production. This is typically
done using marks which are imprinted on the surface of the wafer A
typical computer processor has only an active area of several
hundreds of mm.sup.2, whereas a waver may be as big as 30 cm in
diameter. That is only a small fraction of the wafer size is
processed in a single photolithographic step and thus the complete
wafer is processed by a sequence of consecutive photolithographic
steps across the wafer surface. Once the complete wafer surface is
processed, one proceeds to a next production step, transferring
more structures on the wafer. That is, each wafer segment or
process area (corresponding to the size of a single
photolithographic step) has to be aligned with the processing unit
in the next step of the process for guaranteeing a fully functional
device.
[0007] This is normally done by marks surrounding the individual
process areas and that allow for an adjustment of the process unit
with respect to the process area before processing the wafer.
Normally, the marks are detected and adjusted by optical methods
that provide sufficient accuracy for the optical processing
techniques currently available. For further proceeding technology,
i.e. decreasing the structure sizes into the nanometer regime, the
precision of these alignment procedures is insufficient.
[0008] One further problem of the marks surrounding the process
areas is that these marks have to be transferred or refreshed after
each single production step, since the marks themselves may be
erased or falsified by certain process steps, such as sputtering or
edging. Therefore, the marks themselves have to be transferred to
each consecutive production step, which may yield accumulating
errors during the production, decreasing the efficiency of
correctly manufactured semiconductor devices on the wafer. Apart
from these principle problems of the prior art, there are also
technical problems, such as the space that is required for the
prior art optical alignment systems. When using nano-imprinting
methods for the production the very first production step can
principally be performed without alignment. However, when it comes
to consecutive production steps, alignment is still required even
with higher accuracy, when using the nano-imprinting technique with
its structure sizes in the nm-regime.
[0009] The space-problems (related to the space required for
alignment systems close to the process units) tend to increase when
going to nanometer-scales, since then, systems that are able to
adjust on a nanometer scale are rather big (compared to the size of
the device that has to be structured). In the case of
nano-imprinting, an alignment system operating on a nanometer scale
that is incorporated into the processing unit (stamp) is presently
not feasible. An atomic force microscope is a high precision
measurement tool, that is probing the surface of a material by a
mechanical probe which has a tip of the size of essentially one
atomic diameter (in the order of 10.sup.-10 nm). Although the tip
itself and the needle having this tip, is normally rather small,
the read-out is performed with an optical laser system that detects
the tip movement by a change of the position of a reflected laser
spot on an imaging device. To detect movements of several
nanometers, the dimensions of the read-out system have to be rather
big, thus making it infeasible to incorporate them into the process
unit that stamps the surface of a wafer.
[0010] One further big disadvantage of the prior art method is that
the alignment (adjustment) of the process unit with respect to the
wafer and the processing itself is done in a sequential manner,
i.e. one alignment step is preceding each processing step, which is
putting limits to the overall efficiency of a production process
using prior art alignment.
[0011] This is especially true. when either the processing or the
adjustment is consuming much more time than its counterpart, which
means that in the view of overall processing time for a single
wafer, a lot of time is wasted awaiting the end of one particular
process step.
SUMMARY
[0012] According to an embodiment, a method for manufacturing a
device using a substrate may have the steps of: determining a
position of an alignment mark being fixed with respect to the
substrate; determining position information on the position of a
first process area and on the position of a second process area
with respect to the alignment mark using topographic information
determined within the process areas of the surface of the
substrate; redetermining the position of the alignment mark;
aligning the position of the first process area using information
derived from the redetermined position of the alignment mark and
from the position information on the position of the first process
area; processing the first process area using a nano-imprinting
technique; aligning the second process area using information
derived from the position information on the position of the second
process area; and processing the second process area using the
nano-imprinting technique.
[0013] According to another embodiment, a substrate support
structure adapted to allow determination of position information on
a position of a process area on the surface of a substrate may
have: a substrate support having an alignment mark having a surface
structure, the surface structure having topographic information; a
substrate, being reversibly fixed to the substrate support, such
that the substrate is in fixed orientation with respect to the
alignment mark; and a computer-readable information structure,
allowing to carry information associated to the substrate.
[0014] According to another embodiment, an apparatus for processing
a substrate may have: a calibration unit for determining the
position of the alignment mark; a position measuring unit for
determining topographic information of the surface of the substrate
and for deriving the position information on the position of a
first process area and on the position of a second process area
using information on the determined position of the alignment mark
and the topographic information determined within the process
areas; a processing device for processing the first and the second
process areas using nano-imprinting-techniques; a recalibration
unit for redetermining the position of the alignment mark; and an
alignment unit for performing an alignment of the processing device
and the first process area using information derived from the
redetermined position of the alignment mark and from the position
information on the position of the first process area and for
performing an alignment of the processing device with the second
process area using information derived from the position
information on the position of the second process area.
[0015] The present invention is based on the finding that a
substrate can efficiently be manufactured separating the alignment
and the actual processing, when an alignment mark is provided,
which is fixed with respect to the substrate and when position
information on a position of a process area on the substrate is
retrieved with respect to the alignment mark before the substrate
is actually processed. During the processing, alignment can then be
performed by redetermining the position of the alignment mark and
by using the stored position information.
[0016] In one embodiment of the present invention a substrate, that
is to be processed, is provided together with an associated
alignment mark, which is fixed with respect to the substrate.
Additionally, position information on the position of process areas
on the substrate is provided together with the substrate, wherein
the position information is given with respect to the alignment
mark (for example a two-dimensional alignment mark, that defines a
coordinate system on the surface of the substrate). In other words,
a substrate, that has been completely mapped, i.e. the position
information of the process areas of the substrate with respect to
the alignment mark is provided for a subsequent manufacturing step.
The position of the one or more alignment marks on the substrate
may be according to the specific implementation requirements. One
choice may be to place the marks close to the border of a wafer
where normally some unused space remains due to the usually
rectangular geometry of devices manufactured on the substrate and
the circular geometry of the wafer itself.
[0017] Therefore, during the actual processing, only a single
measuring step is to be performed. Specifically, the position of
the alignment mark has to be redetermined, when the substrate is
inserted into the processing unit. Knowing the position of the
alignment mark and having the stored position information on the
process areas, the single process areas can be aligned with a
process unit with high accuracy, which can for example be performed
by a state of the art air-cushioned process table.
[0018] In another embodiment of the present invention, the
substrate is mounted to a substrate support which that has
incorporated the alignment mark. The connection between the
substrate and the substrate support is such that the substrate can
be removed from the substrate support without damage, such that a
substrate may be used independently from the substrate support
after a given production step. Using such a substrate support has
the great advantage, that the substrate can be stabilized against
mechanical distortions. Furthermore, the substrate can be aligned
and then stored together with the substrate support, wherein the
alignment (the information of the position of the process areas
with respect to the alignment mark) are persistent in time. Hence,
the substrate and the substrate support may even be stored or
transported to another place, without using the alignment
information.
[0019] It is a great advantage that the measuring (aligning) of the
substrate can be separated from the processing itself, yielding a
much higher overall process performance. This is of particular
interest when either the processing or the aligning takes much more
time than the corresponding step. Applying prior art techniques
would then result in a waste of time since the sequential prior art
approach would lead to unwanted wait cycles either during the
processing or during the alignment.
[0020] In a further embodiment of the present invention, the
alignment information is stored in a memory associated to the
aligned substrate. Transferring the stored information together
with the substrate is enabling a production process where the
alignment is separated from the processing. In a further embodiment
of the present invention, the substrate support comprises a memory
device that holds the calibration information for the substrate
attached to the particular substrate support.
[0021] In a further embodiment, the substrate support is having an
identification mark, which is preferably machine-readable (for
example a bar-code) and which is stored together with the alignment
information (for example in a data base) to allow for a later
association of stored alignment data with a particular
substrate.
[0022] In a further embodiment of the present invention, the
alignment mark is built by a nano-structured surface on either the
substrate or the substrate support such that the detection of the
alignment mark can be performed with an accuracy better than 10
nanometers, for example by an atomic force microscope (AFM). To
this end the alignment mark has topographic information comprising
surface structures with structure sizes smaller than preferably 100
nm. In a further preferred embodiment, the structure sizes are
smaller than 20 nm.
[0023] In a further embodiment of the present invention, the
inventive concept is incorporated into a process unit which is used
to process a substrate using nano-imprinting techniques and
provides the alignment accuracy making high-precision
nano-imprinting possible.
[0024] In a further embodiment of the present invention, the
position information is received and stored as topographic
information, i.e. a three-dimensional surface image of the surface
of a substrate is produced within a coordinate system that is
related to the position of the alignment mark. Using a topographic
information rather than individual alignment marks has the great
advantage that even a miss-aligned first production step would not
yield a broken device, since the position information for the
following production step is retrieved from the topographic
information produced by the previous (possibly misaligned)
production step.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Preferred embodiments of the present invention are
subsequently described by referring to the enclosed drawings,
wherein:
[0026] FIG. 1 shows an example of an inventive apparatus for
providing position information on a surface of a substrate;
[0027] FIG. 2 shows a further embodiment of an inventive apparatus
for providing position information;
[0028] FIG. 3 shows an example for an inventive substrate support
structure;
[0029] FIG. 4 shows an example of an inventive apparatus for
processing a substrate;
[0030] FIG. 5 shows an example for providing position information
with respect to an alignment mark;
[0031] FIG. 6 shows an example of using provided position
information;
[0032] FIG. 7 shows an example for an inventive method for
manufacturing a device; and
[0033] FIG. 8 shows an example for an inventive method for
providing position information.
DETAILED DESCRIPTION
[0034] FIG. 1 shows an example of an inventive apparatus for
providing position information on the position of process areas on
the surface of a substrate. FIG. 1 shows a two-dimensional act of
the apparatus in the direction perpendicular to the surface of the
substrate. An enclosure 1 defines an enclosed process volume, which
may be temperature stabilized and decoupled from the environment
for allowing a precise measurement. Shown are furthermore an
air-cushioned table 2, a substrate support 3, a substrate 5, a
first alignment mark 6a, a second alignment mark 6b, a calibration
unit 7, and a position-measuring unit 8. The substrate 5 is
attached to the substrate support 3 in a reversible way, that is by
means of a fixation that can be removed without damaging the
substrate 5. As indicated in FIG. 1, this may for example be
performed by using partly evacuated structures underneath the
substrate 5 pulling the substrate to the surface of the substrate
support 3.
[0035] Alternatively, other ways to temporarily fix the substrate
to the substrate support, which is also called temporary bonding,
are of course also suited to implement the inventive concept. This
can for example be achieved by "gluing" the parts together using
melted wax, or by using special adhesive foils.
[0036] The substrate support 3 further comprises first and second
alignment marks 6a and 6b, which are in a fixed position relative
to the substrate 5. The substrate support 3 is mounted to the
air-cushioned table 2, which can be moved with high precision
(nanometer scale). The position-measuring unit comprises a
calibration sensor 9a, an auxiliary calibration sensor 9b, a
position sensor 10a, and an auxiliary position sensor 10b.
[0037] As already mentioned, the substrate 5 is fixed with respect
to the first and second alignment mark 6a and 6b. To reproducibly
map the surface of the substrate 5 in a fixed coordinate system,
the coordinate system shall be defined by the first and the second
alignment mark 6a and 6b. Therefore, the position of the alignment
mark with respect to the substrate 5 has to be determined
unambiguously. To achieve this, alignment mark 6a is measured by
the calibration sensor 9a. In the shown example, the alignment mark
6a comprises a nano-structured surface that is probed with an
atomic force microscope (the calibration sensor 9a). The
calibration mark 6a is adapted to provide the position information
in one dimension. Relative position measurement is possible by
counting the number of bumps the atomic force microscope
(calibration sensor 9a) is passing while the air-cushioned table 2
is moving. An absolute position information could then be gathered
straight forwardly by counting the number of bumps from the
beginning of the measurement. Alternatively the absolute position
could be coded within the calibration mark 6a by varying the shape
of the individual bumps or for example by having bumps of different
lengths within the direction of the movement. The detection of the
position of the alignment mark by probing a specific topographic
structure of the surface is just one possibility. Alternative
methods of measuring absolute or relative positions or distances
are equivalently suited to implement the inventive concept.
[0038] To define a complete coordinate system on the surface of the
substrate support 3, a second alignment mark 6b may be present on
the substrate support 3, which can be detected either by a further
atomic force microscope or for example by a calibration unit 7 that
incorporates optical read-out, as indicated in FIG. 1. As indicated
by the auxiliary calibration sensor 9b, the position of the first
alignment mark 6a may also be alternatively determined by an
optical read-out system. Once the alignment marks are detected and
hence the coordinate system on the substrate support 3 is
established, the surface of the substrate 5 can be measured by a
scanning technique with respect to the established coordinate
system. Having a high precision air-cushioned table 2, the scanning
could for example be done by a controlled movement of table No. 2.
During the stepwise movement, the position sensor 10a is able to
measure the position information of the substrate 5 with high
precision in the a coordinate system defined with nanometer
precision and therefore allows for a later precise reproduction of
the properties of the substrate.
[0039] The position information measured with the inventive
apparatus could for example be the position of previously applied
topographic information on the surface of the substrate 5, such as
imprinted marks. The advantage is obviously that once the
coordinate system on the wafer support is known and the position
information is recorded in the so defined coordinate system, a
processing of the wafer surface or of distinct areas of the wafer
surface can be performed without individually aligning the surface
areas of the wafer. On the contrary, a single determination of the
position of the alignment marks 6a and 6b is enough to address
every single process area on the surface of the substrate 5
(wafer).
[0040] It is one big advantage of the inventive concept that the
high-precision alignment (measuring of surface criteria of the
substrate 5) can be separated from processing. If either the
alignment or the processing consumes much more time, this
separation can yield a high gain in overall process performance.
For example, a single apparatus for providing position information
according to FIG. 1 may be used to align the substrates for a
number of processing units.
[0041] Although, the inventive apparatus of FIG. 1 may be used to
determine the position of special marks that are imprinted on the
surface of the substrate for alignment reasons, it is a preferred
embodiment of the present invention that the position information
determined is topographic information of structures previously
applied to the surface of the substrate.
[0042] This has the great advantage that even in the case where a
preceding processing step or even the very first processing step
produced a structure on the surface of the substrate that is
deviating from its design-position, a measurement of the topography
of the substrate 5 will allow for a precise alignment. Such, the
following processing can take place at a position yielding a fully
functional device. In the prior art technique, where every
processing step is aligned with imprinted alignment marks on the
surface of the substrate a small misalignment of a single step of
the production would lead to an unusable device and would therefore
decrease the overall production efficiency.
[0043] The inventive concept provides a possibility to align
structures without having to introduce special marks on the surface
of a substrate. This further avoids problems with the marks
themselves, which might be rendered unusable by certain processes,
such as coating the whole wafer with insulating layers, which might
potentially also cover the alignment marks or decrease the
precision with which the alignment marks can be found by prior art
optical alignment systems.
[0044] Having the fragile substrate 5 on a substrate support 3 has
the additional obvious advantage that the substrate 5 can be
transported without the danger of destroying the substrate 5 during
the transport. Furthermore, if the topographic data is stored in a
memory, which is associated to the substrate 5, the substrate
support 3 can, together with the mounted substrate 5, be stored in
a storage space prior to the use of the substrate 5. Then a
possibility must be provided to unambiguously identify the system
of substrate 5 and substrate support 3. Therefore, there may be
additional computer-readable marks applied to the substrate support
3, such as for example bar-codes or RFID-tokens, whose reading can
be stored together with the topographic or position information in
a data base. After storage, the position information can then
easily be retrieved by a processing station that reads the
computer-readable token and may then read the appropriate position
information from a data storage.
[0045] In a further embodiment of the present invention some memory
device is incorporated into the substrate support 3 such that the
position information measured can be directly stored in the
substrate support used to transport and store the substrate 5.
[0046] FIG. 2 shows a further embodiment of the present invention
incorporating a different position-measuring unit 8, which may also
serve as an example to retrieve the position information as
suggested by the inventive concept.
[0047] The embodiment shown in FIG. 2 is based on FIG. 1 and
therefore the identical parts are labeled with the same numbers and
the description of those parts is identically exchangeable within
the description of the two figures.
[0048] FIG. 2 differs from FIG. 1 in that the position-measuring
unit is having an atomic force microscope as calibration sensor 9a
and an optical read-out system 10b such as a convocal microscope as
a position sensor to measure the surface of the substrate 5. Apart
from the embodiment shown in FIG. 2, every different sensor
combination is also suited to implement the inventive concept of
providing position information on a surface of a substrate.
[0049] FIG. 3 shows a face on view of an example of an inventive
substrate support 3.
[0050] The substrate support 3 comprises several alignment marks
12a to 12d and concentric vacuum structures 14 that may be used to
fix the substrate 5 on the wafer support 3. The alignment marks 12a
to 12d are shown schematically only. They may for example be
implemented as optical patterns or as nano-structured surfaces.
When an atomic force microscope is used to calibrate the position
of the substrate support 3, it is also possible that the inherent
surface properties of the substrate support 3 are used for the
calibration without the need of applying specific calibration
marks. This is possible since an atomic force microscope may probe
the surface of a substrate support 3 on an atomic scale and
therefore the inherent "finger print" of a specific surface area of
the substrate support 3 may also be used as reference mark to
calibrate the position of the substrate support 3.
[0051] The use of an inventive substrate support 3 has a number of
major advantages. Evidently, a wafer and in particular a thinned
wafer is protected from damage by being transported, stored, or
processed when mounted to a substrate support 3. Since the
substrate support 3 defines the coordinate system in which
topographic or position information of the wafer surface is
recorded and stored, a wafer or substrate 3 can advantageously be
aligned and stored in a protected manner for later use. To allow
for storage and later use of an already aligned substrate 5, the
substrate support 3 may also comprise an identification tag 16 that
allows unambiguous identification of the specific substrate support
and the wafer or substrate 5 mounted to it. As an example, the
identification tag 16 is implemented to be a bar code.
Alternatively, every other method of uniquely identifying the
device is also possible, such as RFID-units or optical patterns. In
a further preferred embodiment of the present invention the
substrate support 3 further comprises a memory area in which the
calibration data, i.e. the position information on the surface of
the substrate 5 can be stored. This has the advantage that a
database, associating specific substrates with measured information
is made unnecessary, simplifying the overall handling of
pre-calibrated substrates 5 and substrate supports 3.
[0052] When using a vacuum system as indicated by the vacuum
structures 14 to fix the substrate 5 on the substrate support 3,
additional structures may be incorporated into the substrate
support 3 to keep the vacuum during transport or during storage.
This may for example be a vacuum tank or a small vacuum pump that
may be energized by an accumulator battery.
[0053] The number of alignment marks placed on the surface of the
substrate support 3 is variable, a typical choice could be to place
them at the four corners of the substrate support, such as shown in
FIG. 3. Principally, a single alignment mark having a
two-dimensional pattern that can be unambiguously identified is
enough to define a coordinate system, in which the topographic
information or the position information of the surface of the
substrate 3 can be measured.
[0054] FIG. 4 shows an example of an inventive apparatus for
processing a substrate. The substrate 5 to be processed is mounted
on the substrate support 3 and is already calibrated (aligned),
i.e. position information on the surface of the substrate 5 is
available during the processing. FIG. 4 shows a housing 20 in which
the active components are placed and which may be used as a vacuum
chamber to have the processes in a vacuum.
[0055] FIG. 4 is further showing a process unit 22, calibration
sensors 24a and 24b, an air-cushioned table 26, and an ID-reader
28. The ID-reader 28 may for example be an optical read-out system
to identify the substrate support 3 by an imprinted bar code on the
surface of the substrate support 3. The calibration sensors 24a and
24b are fixed with respect to the process unit 22 and are used to
determine the position of the alignment marks 6a and 6b of the
substrate support 3. Once the alignment marks are detected by the
calibration sensors 24a and 24b, the coordinate system in which the
position information or the topographic information on the surface
of the substrate 5 is available, is defined. Thus, the substrate 5
can be aligned to the unit 22 with a precision in the nanometer
regime, since the coordinate system is known with nanometer
precision and a movement of the air-cushioned table 26 with the
same precision is possible.
[0056] In the example shown, the process unit 22 comprises a vacuum
volume 30, a metallic membrane 32, and a stamp unit 34. The
nano-structured stamp unit 34 is adapted to print structures onto a
specific process area of the surface of the substrate 5. To do the
printing, a small increase of pressure is applied within the vacuum
chamber 30 such that the stamp unit 34 moves down towards the
surface of the substrate 5.
[0057] Using the inventive concept, it is advantageously possible
to subsequently process a complete substrate surface with only
having one alignment or calibration step performed using the
calibration sensors 24a and 24b. Furthermore, as the process unit
covers an area of the substrate 5 that is much bigger than the
actual processed area given by the stamp unit 34, only the use of
the inventive concept enables a production using a process unit 22
as sketched without wasting a lot of surface are of the substrate
5. This is possible according to the present invention since the
structures used for the alignment are placed outside the area of
the actual substrate, in contrast to prior art techniques that rely
on special marks imprinted on the substrate itself.
[0058] FIGS. 5 and 6 illustrate, how the position information may
be determined by the inventive concept and how the determined
position information may later on be used during the processing in
a highly efficient manner.
[0059] FIG. 5 shows a simplified sketch of a substrate support 40
with a wafer 42 mounted to the substrate support 40. In the shown
example, the substrate support 40 comprises three alignment marks
44a to 44c illustrated in a simplified manner. The surface of the
wafer 42 has a first process area 46a and a second process area
46b, whose positions shall be measured and stored for later
processing. When the position of the alignment marks are
determined, a right-handed coordinate system 48 is defined, in
which the position information on the position of the first and the
second process areas 46a and 46b shall be derived. This can, for
example, be achieved by taking a topographic image of the surface
of the complete wafer 42 and identifying previously applied
structures within the process areas 46a and 46b by image processing
techniques. Since the topographic information is scanned within the
coordinate system 48, vectors 50a and 50b pointing for example to
two edges of the process area 46a can easily be derived. In this
example, the position information on the position of the process
areas is stored as two-dimensional vectors in the coordinate system
48.
[0060] FIG. 6 shows the situation in an apparatus for manufacturing
a device using the substrate 42 mounted on the substrate support
40. The position information provided for the manufacturing is the
position vectors 50a and 50b, describing the position of the first
process area 46a in the coordinate system 48 of the substrate
support 40. The substrate support 40 is mechanically introduced
into a process volume 52 having the process coordinate system 54,
which may be used to calculate the movement of an air-cushioned
table 26.
[0061] Hence the problem of alignment consists of the determination
of the position information on the position of the first process
area 46a in the process coordinate system 54. When determining the
position of the alignment marks 44a to 44c, the coordinate system
48 of the substrate support 40 can be redetermined within the
process coordinate system 54. The relative orientation of the
coordinate system 48 with respect to the process coordinate system
54 can be characterized by one translation vector 56 and one
rotation angle 58. Having the translation vector 56 and the
rotation angle 58 determined (alignment), the position vectors 50a
and 50b can easily be transformed into the process coordinate
system 54. For determining the position of the first process area
46a in the process coordinate system 54, the determination of the
alignment marks 44a to 44c and the knowledge of the position
vectors 50a and 50b are required. Once the position of the
alignment marks has been determined for the alignment of the first
process area 46a, only the stored position information on the
further process areas (such as the second process area 46b) is
required to align those further to areas.
[0062] It may be noted that only two process areas are shown in
FIGS. 6a and 6b to simplify the drawing. However, in real
implementations the wafer surface is packed with process areas as
dense as possible to allow for the cheapest possible production of
the single device. The inventive concept is of course applicable
for any number of process areas on a substrate.
[0063] FIG. 7 illustrates an inventive method for manufacturing a
device by means of a flow-chart.
[0064] In a first providing step 70 a substrate, an associated
alignment mark, which is fixed with respect to the substrate and
position information on a position of a first and a second process
area on a surface of the substrate is provided.
[0065] In a coordinate determination step 72, the position of the
alignment mark is determined.
[0066] Then, the position of the first process area is aligned in a
first alignment step 74, using information derived from the
determined position of the alignment mark and from the position
information on the position of the first process area provided.
[0067] Finally, in a second alignment step 76, the position of the
second process area is aligned, using (information derived from the
position information on the position of the second process area
provided.
[0068] FIG. 8 illustrates an inventive method for providing
position information on a position of a first process area and on a
position of a second process area on a surface of a substrate using
an alignment mark, which is fixed with respect to the
substrate.
[0069] In a first coordinate determination step 80, the position of
the alignment mark is determined.
[0070] In a consecutive alignment step 82 position information on
the position of the first process area and on the position of the
second process area is determined using the position of the
alignment mark.
[0071] In a storing step 84, the position information on the
position of the first and on the position of the second process
area is stored in association with the substrate processed.
[0072] Summarizing, the present invention suggests a substrate
support, which is introduced into an apparatus for providing
position information, where it may be fixed to a table that can be
adjusted in the x and the y-coordinate and which can furthermore be
rotated by an angle .PHI.. The fixing is typically performed in
vacuum. On top of the adjustable table typically a measurement unit
is placed, which can detect topographic information on the surface
of a wafer and in particular of structures applied to this surface
by different methods. Examples of methods for determining this
information are confocal microscopy or raster techniques using
atomic force microscopes or atomic force needles. The so determined
topographic information (height coordinate), which are determined
over the full area of the table are stored together with the
horizontal coordinates in a storage location, such as a computer.
The information can later be read-out by a separate apparatus for
processing a substrate. Since the measurement of the structures and
the actual processing may consume different amounts of time, it is
thus advantageously possible to optimize the overall process
performance (time) by combining an appropriate number of
measurement and process units. The determination of the position
information may generally be achieved by any suitable method known.
This could for example also be a measurement of 2 dimensional
information, such as taking high resolution images of the surface
with optical imaging systems, for example using thinned fibers.
[0073] Thus, the separation of measurement and processing increases
the overall process throughput. After the measurement of a
structured wafer, the wafer is submitted together with the wafer
support to a process unit.
[0074] A process unit consists of a table that can be adjusted in
x, y, and .PHI.. The wafer support (wafer transport tool WTT) is
fixed to that table, wherein the fixation may be performed by
evacuating a volume between the wafer support and the table. The
actual process unit (for example a nano-stamp) is situated on the
top of the wafer transport tool. This may for example be a
nano-stamp, which is placed in a microscopic distance above the
previously created structures of the calibrated wafer. The stamp
may for example be air-cushioned, that is flying on top of the
wafer by the force of an air cushion, which may be created by small
air injectors. Preferably, the process volume in which the
processing is performed is evacuated to avoid enclosures of air on
a surface of the substrate, when the surface is stamped.
[0075] The movement of the table in the process unit is computed by
a control unit, which uses the position information generated in a
measurement unit and the coordinates determined by probing the
alignment marks on the wafer transport tool. Since topographic
information of the single devices as well as the specific
parameters (position of alignment marks) of the wafer transport
tool have been processed during the alignment, it is possible for
the process unit to precisely process the individual process areas
of single devices, once the wafer transport tool has been uniquely
identified by for example an identification tag. Adjusting single
devices individually is thus no longer necessary during the actual
processing. Furthermore, since wafer transport tools can be
uniquely identified by ID-tags, one single measure-station may
supply numerous process units. It is furthermore possible to
combine measurement and processing into one single evacuated
volume. On the other hand, it is a big advantage of the inventive
concept, that the wafer transport tools may be stored in
appropriate housings before being finally processed by a process
unit.
[0076] Although the fixation of a substrate (wafer) on a substrate
support has been previously described mainly by use of vacuum
techniques, it is also possible to use any other temporal bonding
technique to fix the substrate on the substrate support. This may
for example be achieved by using wax, which glues together the
substrate and the substrate support and which may be heated up for
the removal of the substrate. Another technique known is using a
foil that connects the substrate and the substrate support due to
adhesive forces.
[0077] Furthermore, the geometrical shape of the substrate support
is by no means restricted to be rectangular as in the above
examples. It is going without saying that an inventive substrate
support may have any other shape without limiting its
functionality.
[0078] In the embodiments discussed in accordance with the
preceding drawings, an alignment mark, which is either being placed
on a substrate support or on the substrate itself is applied to the
substrate or the substrate support in an orientation pointing to
the surface of the substrate. It is of course possible to place the
alignment mark at any other position that can be read-out by a high
precision read-out such as an atomic force microscope. In
particular, it may be advantageous to place the mark on the side of
the substrate support that is opposite to the substrate itself,
allowing for a laterally more compact implementation of the
inventive concept. The alignment mark may also be placed on the
backside of the substrate or the substrate support. It may be noted
that it is also possible to apply the alignment mark on the surface
of the substrate in the very first production step (for example by
nano-imprinting) such that all following production steps align to
those alignment marks.
[0079] Although an extremely high position accuracy can be achieved
by use of atomic force microscopes, the use of an atomic force
microscope is not mandatory to implement the inventive concept.
Alternatively, any other read-out technique, for example capacitive
coupling on a microscopic scale, may be used to precisely determine
the position of the alignment marks.
[0080] While the foregoing has been particularly shown and
described with reference to particular embodiments thereof, it will
be understood by those skilled in the art that various other
changes in the form and details may be made without departing from
the spirit and scope thereof. It is to be understood that various
changes may be made in adapting to different embodiments without
departing from the broader concepts disclosed herein and
comprehended by the claims that follow.
* * * * *