U.S. patent application number 15/987982 was filed with the patent office on 2018-09-20 for device and method for aligning substrates.
The applicant listed for this patent is Erich THALLNER. Invention is credited to Erich THALLNER.
Application Number | 20180269096 15/987982 |
Document ID | / |
Family ID | 46262111 |
Filed Date | 2018-09-20 |
United States Patent
Application |
20180269096 |
Kind Code |
A1 |
THALLNER; Erich |
September 20, 2018 |
DEVICE AND METHOD FOR ALIGNING SUBSTRATES
Abstract
A device for aligning and bringing a large-area substrate into
contact with a carrier substrate comprising: a substrate holding
means for attaching the substrate ; a carrier substrate holding
means for attaching the carrier substrate; detection means for
detection of a peripheral contour of the substrate attached to the
substrate holding means and detection of a peripheral contour of
the carrier substrate attached to the carrier substrate holding
means relative to a contact plane of the substrate with the carrier
substrate; aligning means for aligning the substrate relative to
the carrier substrate; and contacting means for bringing the
substrate into contact with the carrier substrate.
Inventors: |
THALLNER; Erich; (St.
Florian, AT) |
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Applicant: |
Name |
City |
State |
Country |
Type |
THALLNER; Erich |
St. Florian |
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AT |
|
|
Family ID: |
46262111 |
Appl. No.: |
15/987982 |
Filed: |
May 24, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14406790 |
Dec 10, 2014 |
10014202 |
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PCT/EP2012/061109 |
Jun 12, 2012 |
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15987982 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 21/67121 20130101;
H01L 21/681 20130101; H01L 21/67346 20130101; H01L 21/67736
20130101; Y10T 428/21 20150115; H01L 21/682 20130101; H01L 21/68
20130101 |
International
Class: |
H01L 21/68 20060101
H01L021/68; H01L 21/677 20060101 H01L021/677; H01L 21/673 20060101
H01L021/673; H01L 21/67 20060101 H01L021/67 |
Claims
1. A device for detecting positions of a substrate and a carrier
substrate fixed to the substrate, the device comprising: a first
substrate holder configured to fix the substrate; and detecting
means for at least sectionwise detecting positions of the fixed
substrate and for at least sectionwise detecting positions of the
fixed carrier substrate.
2. The device according to claim 1, wherein a distance between a
peripheral edge of the substrate and a peripheral edge of the
carrier substrate in a radial direction from respective centers of
the substrate and the carrier substrate is in a range of 5 .mu.m to
10 .mu.m.
3. The device according to claim 1, wherein the first substrate
holder is fixed in a carrier unit, the carrier unit being
configured to move the first substrate holder in x- and
y-directions.
4. The device according to claim 3, wherein the carrier unit is
further configured to rotate the first substrate holder.
5. The device according to claim 1, wherein the first substrate
holder is fixed in a carrier unit, the carrier unit comprising the
detecting means.
6. The device according to claim 5, wherein the detecting means is
configured to scan the fixed substrate and the fixed carrier
substrate in a narrow band range in a vertical direction.
7. The device according to claim 6, wherein the detecting means
scans the fixed substrate and the fixed carrier substrate
simultaneously.
8. The device according to claim 1, wherein the detecting means
comprises one or more optical scanning units that are configured to
detect the positions of the fixed substrate and the positions of
the fixed carrier substrate.
9. The device according to claim 8, wherein the optical scanning
units are further configured to simultaneously scan respective
peripheral contours of the fixed substrate and the fixed carrier
substrate.
10. The device according to claim 9, wherein the optical scanning
units comprise respective distance-measuring elements that are
configured to continuously determine a distance from the peripheral
contours to the respective distance-measuring elements.
11. The device according to claim 9, wherein the optical scanning
units are further configured to produce a gap profile that
simultaneously measures respective outside geometries of the fixed
substrate and the fixed carrier substrate to calculate an outside
diameter of the substrate and the carrier substrate that is the
greatest and a distance from the respective peripheral contours of
the fixed substrate and the fixed carrier substrate with respect to
one another.
12. A method for detecting positions of a substrate and a carrier
substrate, comprising: fixing the substrate to a first substrate
holder; fixing the carrier substrate to the substrate; and at least
sectionwise detecting positions of the fixed substrate and at least
sectionwise detecting positions of the fixed carrier substrate.
13. The method according to claim 12, wherein the sectionwise
detecting positions of the fixed substrate and the sectionwise
detecting positions of the fixed carrier substrate are
simultaneously performed.
14. The method according to claim 12, wherein the sectionwise
detecting positions of the fixed substrate and the sectionwise
detecting positions of the fixed carrier substrate comprise
scanning the fixed substrate and the fixed carrier substrate in a
narrow band range in a vertical direction.
15. The method according to claim 12, wherein the sectionwise
detecting positions of the fixed substrate and the sectionwise
detecting positions of the fixed carrier substrate comprise
optically scanning respective peripheral contours of the fixed
substrate and the fixed carrier substrate simultaneously.
16. The method according to claim 15, wherein the optically
scanning comprises producing a gap profile that simultaneously
measures respective outside geometries of the fixed substrate and
the fixed carrier substrate to calculate an outside diameter of the
substrate and the carrier substrate that is the greatest and a
distance from the respective peripheral contours of the fixed
substrate and the fixed carrier substrate with respect to one
another.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 14/406,790, filed Dec. 10, 2014, which is a U.S. National Stage
of International Application No. PCT/EP12/61109, filed Jun. 12,
2012, said patent application hereby fully incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] This invention relates to a device for aligning and bringing
a large-area substrate into contact with a carrier substrate for
the further processing of the substrate as well as a corresponding
process.
BACKGROUND OF THE INVENTION
[0003] The back-thinning of wafers is often necessary in the
semiconductor industry and can be done mechanically and/or
chemically. For back-thinning, the wafers are generally temporarily
attached to a carrier system, by various methods of attachment. As
carrier systems, films or wafers made of, for example, silicon,
silicon alloys such as SiC, SiN, etc., ceramics,
(glass-fiber-reinforced) plastics, graphite, sapphire, metals,
glasses or composite materials are used. At the end of the
back-thinning process and the post-processing, the back-thinned
wafers are mounted on film holders, and then the carrier is
removed.
[0004] Whenever a working of the substrate that goes beyond the
back-thinning is necessary, rigid carrier systems, namely carrier
substrates, are used. Examples of such working steps after
back-thinning are: metallization, dry etching, wet etching, laser
processing, lithography, oven processes, doping, etc.
[0005] In the case of a rigid carrier substrate, the product
substrate that is to be worked is typically connected by an
adhesive layer to the carrier substrate.
[0006] The carrier substrate is to impart adequate mechanical
stability to the substrate that is to be worked in order to be able
to be worked in related process steps or process devices. In the
case of a temporary connection, target thicknesses are now: between
30 and 100 .mu.m. In the future, thinner product substrates are
targeted between 1 .mu.m and 50 .mu.m; in the case of a permanent
connection, still thinner product substrates are possible, which
are physically limited only by the requirements as regards the
height of a transistor with connections. The minimal thicknesses of
a product substrate are between 0.001 .mu.m and 5 .mu.m.
[0007] Some of the above-mentioned working steps require an exact
positioning of the substrates or the carrier within the
corresponding devices.
[0008] In this case, product substrates with a nominal 300 mm
+/-200 .mu.m, for example, are bonded to the carrier substrate with
301 mm +/-200 .mu.m. This is done as a precautionary measure in
order to adequately protect, and in particular to support, wafers
in the edge areas that are to be back-thinned or that are
back-thinned. Because of this measure, the carrier substrate is,
however, unattached in the edge area in various working steps, in
particular in sputter processes, galvanic deposition and etching
processes.
[0009] Because of the carrier substrates mentioned in the state of
the art, several problems result. Deposition processes, etchings on
the edge of the carrier substrate, etc., result in the carrier
substrate edge being heavily contaminated.
[0010] After detaching from the product substrate, this
contaminated edge area must be purified, at great expense in cost
and labor. Often, the defective carrier substrate edge is the sole
factor that limits the service life of the carrier substrate. The
additional costs for an end product follow from, the costs of the
carrier substrate, its recycling costs, and the number of reuse
cycles. By this previously used process, a purification step of the
carrier substrate is very costly. As a result, in many cases, the
carrier substrate is not reused.
[0011] The more advantageous the carrier substrate, the less
critical is a small number of reuse cycles; for example, at least
ten reuse processes are desired for carrier substrate production
costs of around 20 .
[0012] The more costly the carrier substrate, the more important is
its long service life (=large number of reuse cycles). For example,
1,000 reuse processes are desired for carrier substrate production
costs of around 2,000 .
[0013] Properties that can make a carrier substrate costly in the
first production are, e.g.: [0014] Starting material, [0015]
Precise geometry: low TTV (Total Thickness Variation), e.g., <1
.mu.m necessary to be able to smooth and polish the product as
precisely as possible to the desired thickness, [0016]
Pretreatments that make possible a subsequent detaching of the
temporary bond.
[0017] Because of these problems, very costly carrier substrates
are frequently not used at all, even though they had useful
properties for other process steps.
[0018] In the process steps cited below, very stringent
requirements exist as regards the accuracy of the alignment of two
wafers: [0019] In the case of plasma working of back-thinned wafers
on carrier substrates, an eccentricity produces an uneven discharge
of the plasma. Discharges that are produced (breakdowns because of
high electrical field density--arcing) can cause damage to products
and plasma process chambers. Special advantages in plasma and
sputter processes are achieved because of the possibility of using
a carrier substrate that is the same as/smaller than the product
substrate. [0020] In the case of lithographic exposure on so-called
scanners and steppers, inadequately adjusted bond pairs are not
loaded with sufficient accuracy. The referencing (pre-alignment) of
the bond pair is done based on the outside contour. The outside
contour of a (much) larger carrier substrate, however, does not
correspond to the position of the passmarks on the product
substrate as long as the adjustment of the two outside contours is
not precise, or the outside contour of the product substrate cannot
be used. The passmarks are thus not in the "capture range" of the
microscope, and a laborious search must be made for them. This
leads to losses in time, production throughput and productivity in
these systems.
[0021] An advantage of this invention is a device and a process for
aligning and bringing substrates into contact, wherein a more exact
and more efficient alignment and bringing substrates into contact
with a carrier substrate is made possible.
[0022] This advantage is achieved with the features of the claimed
invention. Advantageous further developments of the invention are
indicated in the subclaims. Also, all combinations that comprise of
at least two of the features indicated in the specification, the
claims and/or the figures fall within the scope of the invention.
In the indicated ranges of values, values that lie within the
above-mentioned limits are also to be disclosed as boundary values
and can be claimed in any combination.
SUMMARY OF THE INVENTION
[0023] The invention is based on the idea of achieving a more exact
alignment by--in particular electronic--detection (detection means)
of outside contours of the substrates to be aligned and brought
into contact, as well as processing (control means) of the detected
outside contours in control signals for alignment (alignment means)
of the substrates. According to the invention, the alignment is
preferably done continuously when substrates are moved on one
another to bring them into contact. Moreover, it is conceivable to
examine the alignment accuracy with the same detection means and
optionally to perform a renewed alignment.
[0024] Substrates are defined as product or carrier substrates used
in the semiconductor industry. The carrier substrate serves as an
enhancement of the function substrate (product substrate) in the
different working steps, in particular during back-thinning of the
function substrate. Suitable substrates, in particular wafers, come
either with smoothing ("flat") or grooves ("notch").
[0025] As an independent invention, a product (or a
substrate-carrier substrate combination) is provided, which is
comprised of a carrier substrate and a substrate, which have been
aligned, brought into contact and prefixed with one another and/or
bonded with the device according to the invention and/or the
process according to the invention and are distinguished in that
the diameter d2 of the carrier substrate is minimally smaller than
the diameter d1 of the product substrate. According to the
invention, it is thus ensured that the carrier substrate during the
processing of the product substrate is exposed to no contamination,
fouling or unintentional treatment, etc., whatsoever and therefore
can be reused more frequently.
[0026] Although the embodiment, according to the invention, is
primarily suitable to align a carrier substrate that is smaller as
far as the diameter d2 is concerned, relative to a substrate that
is larger as far as the diameter d1 is concerned, a device
according to the invention can also be used to align carrier
substrates toward one another, where the carrier substrates are
larger than or the same size as the substrates that are to be
bonded.
[0027] By the detection means being rotatable relative to the
substrate and/or relative to the carrier substrate by rotational
means, and/or adjustable parallel to the contact plane relative to
the substrate and/or relative to the carrier substrate by an
adjustment system in the X- and/or Y-direction, the alignment can
be implemented efficiently and precisely.
[0028] According to an advantageous embodiment of the invention,
the detection means are attached to a carrier unit that is designed
in particular to be annular in sections and that can be arranged at
least in sections on the peripheral side with respect to the
substrate and/or carrier substrate.
[0029] Thus, an integration according to the invention of the
detection means is possible in an efficient way.
[0030] Advantageously, the carrier unit is attached between the
carrier substrate holding means and the substrate holding means, in
particular with contacting means attached in-between, preferably in
the form of a Z-adjustment unit and/or with a base plate attached
in-between. In this way, an especially efficient configuration of
the invention is provided.
[0031] In this case, in further development of the invention, it is
advantageous when the adjustment system is attached directly
between the base plate and the carrier unit. Thus, a direct action
on the carrier unit, together with the substrate holding means
attached thereto, is conceivable.
[0032] According to another advantageous embodiment of the
invention, the peripheral contour and the peripheral contour (both
peripheral contours) are detectable at the same time, with the
same, one or more, detection means, preferably microscopes. In this
way, the number of costly detection means can be reduced without
sacrificing speed.
[0033] The alignment of a substrate can also be done in a substrate
stack as a carrier substrate. In this respect, a substrate stack is
defined as an amount of already worked, for example back-thinned,
substrates, which are bonded with one another permanently.
According to the invention, this substrate stack, when it is thick
enough, can serve as a carrier substrate.
[0034] The use of a mechanical alignment system (adjustment system
and rotation means) is preferred both for the substrate and for the
carrier substrate in connection with an optical distance-measuring
system. In this respect, it is of special advantage when this
alignment system is integrated in a unit for bonding or prefixing
the substrates.
[0035] The invention thus allows an exact, quick and economical
alignment of two substrates (substrate and carrier substrate) with
respect to one another, without having to refer to the alignment
marks. According to the invention, carrier substrates can therefore
dispense with alignment marks, so that the latter can be produced
more advantageously.
[0036] In addition, because of this invention, repeated use of the
carrier substrate is possible, without the latter having to be
purified by labor-intensive and costly processes.
[0037] Moreover, the possibility arises of
incorporating/integrating the device according to the invention in
a bonder.
[0038] With this invention, the different diameters of the
substrates at several points of the periphery (peripheral contours)
are taken into consideration, and a more precise positioning is
made possible. Such consideration is not possible in the case of
other mechanical and/or optical positioning processes. At the same
time, a faster alignment than in the case of (purely) mechanical
alignment is made possible.
[0039] The process underlying the invention and the device
according to the invention make possible the necessary accuracies,
in particular <50 .mu.m, and in particular to achieve a higher
rotational accuracy on the periphery, which is a weak point in the
case of previous mechanical processes. Very precise grooves can be
assigned on the periphery of the substrate (so-called "notches") of
the substrate and carrier substrate.
[0040] Advantageously, the grooves are located in such a position
that they are detected by at least one detection means. Any
detection means whose direction of measurement is parallel or
almost parallel to the substrate normal can determine a rotational
mis-orientation quickly by the position of the grooves. Similar
considerations apply to substrates with flats or any other grooves
or deviations from a predetermined ideal geometry of the substrate
in question, which can be used for rotational alignment.
[0041] The process according to the invention is in particular a
dynamic, optical scanning process with software-controlled
optimization of the detected/measured data.
[0042] In an advantageous embodiment of the invention, the carrier
substrate and the function substrate are attached in each case to
separate, mechanically movable holding devices (substrate holding
means/carrier substrate holding means). In this respect, chucks
with vacuum holding devices are provided. Other holding devices,
such as adhesive materials, mechanical clamps, or electrostatic
holding devices, can be provided. Also, instead of the carrier
substrate, production substrates can also be provided. Also,
repeatedly bonded or back-thinned multi-layer substrates can be
adjusted/aligned with this process.
[0043] Advantageously, one of the two substrates is attached on a
fastening system (in particular a carrier substrate holding means)
that can move in the z-direction. The other substrate is attached
on a rotatable chuck (in particular a substrate holding means). The
latter is fastened in a mechanical adjustment unit (in particular a
carrier unit), which can be adjusted in the x- and y-direction.
On/in this mechanical adjustment unit, there are one or more
optical scanning units (detection means), which detect(s) (scan(s))
the two substrates, simultaneously, in a narrow band range in the
vertical direction. As a result, a gap profile is produced that
simultaneously detects/measures the outside geometry (peripheral
contours) of the two substrates. This gap profile produces the
largest outside diameter of the respective substrate and the
distance between the individual substrates and the measuring points
or measuring sections.
[0044] These scanning units of the detection means advantageously
rotate in the mechanical adjustment unit in--or parallel to--the
contact plane in order to make possible a detection of several
peripheral sections of the peripheral contours of the substrates.
By the rotation of the scanning units, it is possible to measure
the outside geometry of the two substrates and at the same time to
determine the position of the two substrates with respect to one
another. The rotation can describe a full circle or else only
sectors/detection sections. For less precise adjustment
requirements, rotation of the scanning units can be eliminated. It
is also possible not to rotate the scanning units, but rather to
rotate the two substrates in the case of stationary scanning
units.
[0045] As an alternative, several scanning units can also be
arranged in a stationary manner around the two substrates, in
particular at least 3, in order to determine the position and the
diameter of the two outside contours (or idealized circles that
correspond in software). In this case, a rotation of substrates
and/or scanning units can be omitted, and a slight rotation of one
substrate relative to the other substrate is sufficient to align
the notches or the flats in the rotational direction in the contact
plane.
[0046] As an alternative, the scanning units can be arranged
approximately at right angles to the substrate plane from above or
below and can detect the edges of the peripheral contours of the
substrates. In a special case, these are microscopes that provide
an optical image of the two wafer edges for measurement and
evaluation.
[0047] One or more of these microscopes can be arranged to be
movable according to the invention (rotating around fixed/standing
substrates) or stationary (with rotating substrates).
[0048] In another special case, at least three microscopes are
arranged in a stationary manner on the periphery above and/or below
the substrates. Both peripheral edges are visible via the
microscopes (optionally by refocusing because of the Z-distance
(crosswise to the X- and Y-direction or contact plane), which could
exceed the depth of focus. The substrate with the larger diameter,
which could obscure the view on the peripheral edge of the smaller
substrate, can be moved a certain distance by the alignment means
and can thus be made visible and positionable. The image
information of the two peripheral edges is converted into a piece
of positional information, and the substrates can be aligned
precisely with respect to one another.
[0049] By software, the necessary calculation of the adjustment
paths of the mechanical adjustment elements (alignment means) in
the X- and Y-direction as well as the necessary rotation of the
substrates can be calculated. This calculation and measurement can
be continuously measured and corrected everywhere during the
Z-movement (contacting means), i.e., the mechanical engagement of
the two substrates.
[0050] Because of this online measuring process, it is possible to
correct possible deviations during or after the assembly of the
substrates or to ensure optimization by separating the units and
providing for renewed alignment and bringing into contact.
[0051] Because of the device according to the invention and the
process according to the invention, it is also possible to align
precisely greatly different substrates, such as different diameters
or different geometries, for example round substrates with respect
to rectangular substrates.
[0052] According to a further development of the invention, it is
advantageous when the substrate is back-thinned after being brought
into contact, whereby the diameter d1 is reduced by the shape of
the cross-section of the substrate on its peripheral contour, in
particular to d1<=d2. As a result, the simple further processing
of the substrate-carrier substrate combination, in particular in
known and standardized units, is made possible.
[0053] In this case, it is of special advantage when the substrate
has an annular shoulder that is produced in particular by providing
an edge radius and/or by looping back the peripheral contour. The
latter can be produced in a simple way and contributes to the
further optimization of the production process according to the
invention.
[0054] By an annular width dR of the shoulder being larger than or
equal to the difference between d1 and d2, the diameter of the
substrate can be reduced to the diameter d2 of the carrier wafer or
smaller, so that in the further processing, an optimal support of
the product substrate is ensured.
[0055] According to another advantageous embodiment of the
invention, it is provided that during back-thinning, a thickness
D.sub.1 of the substrate is reduced up to or over the shoulder.
[0056] The device according to the invention is further developed
wherein the detection means are designed to detect the shape of the
cross-section of the substrate on its peripheral contour in such a
way that the back-thinning of the substrate can be controlled so
that the diameter d1 is reduced, in particular to d1<=d2. By the
detection of the shape of the cross-section, a profile of the
cross-sectional contour viewed from the side, i.e., along the
thickness D1 of the substrate, an exact control of the
back-thinning process can be carried out according to the
invention.
[0057] To the extent that existing device features and/or device
features in the following figure description are disclosed, the
latter are also to be regarded as disclosed as process features and
vice versa.
[0058] Further advantages, features and details of the invention
follow from the following description of preferred embodiments and
based on the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0059] FIG. 1a is a schematic cross-sectional view of a device
according to the invention in a first embodiment,
[0060] FIG. 1b is a schematic overview of the device according to
FIG. 1a,
[0061] FIG. 2a is a schematic cross-sectional view of a device
according to the invention in a second embodiment,
[0062] FIG. 2b is a schematic overview of the device according to
FIG. 2a,
[0063] FIG. 3a is a schematic cross-sectional view of a process
step of an embodiment of a product according to the invention
(substrate-carrier substrate combination) before the bonding
step,
[0064] FIG. 3b is a schematic cross-sectional view of a process
step of an embodiment of a product according to the invention after
the bonding step,
[0065] FIG. 3c is a schematic cross-sectional view of a process
step of an embodiment of a product according to the invention after
the back-thinning,
[0066] FIG. 4a is a schematic cross-sectional view of a process
step of an embodiment of a product according to the invention
before the bonding step,
[0067] FIG. 4b is a schematic cross-sectional view of a process
step of an embodiment of a product according to the invention after
the bonding step, and
[0068] FIG. 4c is a schematic cross-sectional view of a process
step of an embodiment of a product according to the invention after
the back-thinning.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0069] In the figures, advantages and features of the invention are
characterized with these reference numbers that are identified in
each case according to embodiments of the invention, whereby
components or features with the same function or components or
features whose function has the same effect are characterized with
identical reference numbers.
[0070] The figures show a device and a process, which make it
possible to align substrates 2, 5 (or substrate stacks) with
respect to one another via peripheral edges 2u, 5u. The process
according to the invention is a dynamic, optical scanning process
with software optimization of the measured data.
[0071] In FIGS. 1a and 1b, a product substrate is attached as
substrate 2 to a substrate holding means 1 (chuck). The substrate
holding means 1 is adjustable in the Z-direction via an adjustment
unit 3 (contacting means), i.e., crosswise to a contact plane
between the substrate 2 and a carrier substrate 5.
[0072] Above the substrate holding means 1, there is another chuck
(carrier substrate holding means 4) with the carrier substrate 5
attached thereto. The carrier substrate holding means 4 is
connected to a mechanical unit (carrier unit 7) via a rotational
guide (rotational means 6). This mechanical carrier unit 7 is
connected to a base plate 9 via guides (adjustment system 8 for
adjustment in the X- and Y-direction). This adjustment system 8
makes it possible that the mechanical carrier unit 7 can be moved
in the X- and Y-direction, specifically controlled via a control
system, not shown.
[0073] Technically, the only important thing is producing a
relative movement between the substrates 2, 5.
[0074] This carrier unit 7 has an annular, preferably circular,
guide element 10. A distance-measuring element 11 (detection means)
is located on the guide element 10. The detection means are
advantageously positioned in the contact plane of the two
substrates 2, 5, and all distances are measured/detected at a
specific angular range by the distance-measuring element.
[0075] As a result, in this scanned angular range, a distance
profile is produced that assigns the position of the substrates 2,
5 to the instantaneous position of the scanning unit (detection
means).
[0076] In the area of the circular guide element 10, the detection
means have additional measuring means 12. The measuring means 12
define the precise position of the scanning unit 11 on the
periphery of the substrates 2, 5. An evaluation unit of the
measuring means 12 is advantageously integrated in the assigned
distance-measuring elements. This is advantageous when several
distance-measuring elements are used.
[0077] In an independent embodiment according to the invention, a
carrier substrate 5 is used, which has a slightly smaller diameter
d2 than the diameter d1 of the product substrate 2. Thus, the
carrier substrate 5, primarily the carrier substrate edge
(peripheral edge 5u) is protected from additional process steps,
and the carrier substrate 5 can be used preferably several times
without additional purification steps. According to the invention,
even very costly and complex carrier substrates 5 can thus be used
many times.
[0078] If the carrier substrate 5, unlike previous common practice
in the semiconductor industry, is not larger but rather smaller (or
within the scope of manufacturing tolerances is of equal size) than
the product substrate 2, no purification process of the carrier
substrate edge 5u is required, and the edge area of the carrier
substrate 5 remains free of contamination, since the product
substrate 2 serves as a cover for the carrier substrate 5 and/or
the carrier substrate edge 5u, and this carrier substrate 5 is not
exposed to the effects of the working. The carrier substrate 5 can
therefore be reused without a purification step.
[0079] The difference between the (mean) diameter d1 of the product
substrate 2 and the (mean) diameter d2 of the carrier substrate 5
is less than 500 .mu.m, preferably less than 400 .mu.m, more
preferably less than 300 .mu.m, most preferably less than 200
.mu.m, and with utmost preference less than 100 .mu.m.
[0080] In the case of product substrate diameters and carrier
substrate diameters of the same size and because of manufacturing
tolerances, a case can also arise where the diameter d2 of the
carrier substrate 5 is minimally (within the manufacturing
tolerance) larger than the diameter d1 of the product substrate 2.
It is important according to the invention that protection of the
carrier substrate edge 5u is adequately provided by the shadowing
action of the product substrate edge 2u of the, in this case,
smaller product substrate 2 (not indicated).
[0081] In order to achieve the required accuracy of the edge
overlap, the edge agreement (edge extension of the product
substrate 2) is in particular precise to within 5 .mu.m to 10 .mu.m
(concentric). In other words, the distances between the peripheral
edges 2u, 5u deviate from one another in the radial direction from
the center of the substrates 2, 5 by at most the above-mentioned
values.
[0082] According to the invention, the carrier substrate 5 is
smaller than the product substrate 2 by 0 .mu.m to 500 .mu.m, so
that the mechanical support of the mechanically critical edge area
2u of the product substrate 2 remains adequate.
[0083] For reasons of cost and production throughput, positioning
on passmarks within the carrier substrate 5 is preferably not
provided. Therefore, all adjustments according to the invention are
made between structured product substrate and unstructured carrier
substrate according to the substrate edges 2u, 5u of the substrates
2, 5.
[0084] Since the substrate edges 2u, 5u of the substrates 2, 5 can
be associated with considerable manufacturing tolerances, a precise
positioning is especially critical, especially when very precise
positionings below 20 .mu.m are required.
[0085] Therefore, accuracies according to the invention of +/-5
.mu.m to +/-20 .mu.m and rotational accuracies of +/-5/10 .mu.m
equivalent on the notch (if present on the carrier substrate) or on
the flat are required.
[0086] The carrier substrate holding means 4 is mounted to rotate
by the rotational means 6 and is connected via the carrier unit 7
to the adjustment system 8, which makes possible a translational
movement of the carrier unit 7 and thus the carrier substrate
holding means 4. One (or more) optical scanning unit(s) 15, 15' are
located in the carrier unit 7.
[0087] The scanning unit 15, 15' is able to detect, in particular
to scan, the peripheral contours 2u, 5u of the two substrates 2, 5
at least in sections. The distance-measuring system 11 allows the
continuous determination of the distance from the
distance-measuring system 11 to the peripheral contours 2u, 5u.
[0088] As a result, a gap profile is produced, which simultaneously
measures/detects the outside geometry of the two substrates 2, 5.
This gap profile produces both the largest outside diameter of the
respective substrate 2, 5 and the distance from the peripheral
contours 2u, 5u of the individual substrates 2, 5 with respect to
one another. The scanning units 15, 15' preferably rotate along the
guide elements 10 in the mechanical device.
[0089] Because of the rotation of the scanning units 15, 15', it is
possible to measure the substrate edges 2u, 5u of the two
substrates 2, 5 and at the same time to determine the position of
the two substrates 2, 5 relative to one another. The scanning units
15, 15' can move along a closed circle if the guide 10 is closed,
or only along circular segments 10, as shown in the embodiment in
FIG. 1b. For fewer precise adjustment requirements, the rotation of
the scanning units 15, 15' can be eliminated. It is also possible
not to rotate the scanning units 15, 15' but rather to rotate the
two substrates 2, 5 in the case of stationary scanning units 15,
15', by corresponding contacting means 3 having rotational
units.
[0090] In the embodiment according to FIGS. 2a and 2b, the scanning
units can be optics 13, 13', 13'', 13''', whose optical axes are
approximately at right angles to the substrate surface of the
substrate 2. In one embodiment, the scanning units are microscopes
that supply an optical image of the substrate edges and thus the
peripheral contours 2u, 5u for measuring and evaluation.
[0091] One or more of these optics 13, 13', 13'', 13''' can in turn
be arranged to be movable (rotating around the standing substrates
2, 5) or stationary (with rotating substrates 2, 5).
[0092] In another embodiment, at least four optics 13, 13', 13'',
13''' are arranged in a stationary manner on the periphery above
and/or below the substrates 2, 5. Both substrate edges 2u, 5u are
visible through the optics 13, 13', 13'', 13''' (optionally with
refocusing because of the Z-distance, which could exceed the depth
of focus).
[0093] In this embodiment, it is advantageous when the carrier
substrate 5 lies with the lower diameter d2 in the optical path
between the optics 13, 13', 13'', 13''' and the substrate 2 with
the larger diameter d1, so that for the optics 13, 13', 13'',
13''', both peripheral contours 2u, 5u with corresponding alignment
of the two substrates 2, 5 with respect to one another are visible
at the same time.
[0094] Should the optics be sensitive to an electromagnetic
irradiation, for which the substrates that are used are
transparent, the substrate 2 with the larger diameter d1 can also
be located closer to the respective optics. By way of example,
silicon wafers that are transparent to infrared radiation can be
mentioned.
[0095] Mathematically, the adjustment of the two substrates 2, 5
with respect to one another can be done based on any adjustment
calculation, preferably by the least squares method. The optics or
distance-measuring systems are preferably to be designed in such a
way that the recorded data are digitized and can be forwarded to a
corresponding computer.
[0096] Corresponding software in the computer (control system) is
able to control the X- and/or Y- and/or rotational units in such a
way that a continuous matching of the alignment of the two
peripheral contours 2u, 5u with respect to one another is carried
out specifically until the corresponding adjustment calculation of
the software yields a parameter that is a measurement of the
accuracy of the adjustment calculation, which value drops below a
threshold value specified by the user.
[0097] FIGS. 3a-3b show a shortened process for the production of a
product according to the invention (substrate-carrier substrate
combination) with the carrier substrate 5, whose diameter d2--at
least before the back-thinning process (FIGS. 3a-3b)--is smaller
than the diameter d1 of the substrate 2. After an alignment and
bonding process according to the invention (FIG. 3b), a
back-thinning process of the substrate 2 (FIG. 3c) is carried
out.
[0098] The substrate 2 is connected to the carrier substrate 5 by
an adhesive layer 14, which is attached to the substrate 2 before
the bonding, in particular to an adhesive surface with a diameter
d3, which is between the diameter d2 of the carrier substrate 5 and
the diameter d1 of the substrate 2, and preferably corresponds to
the diameter d2 of the carrier substrate 5.
[0099] In the embodiment according to FIG. 3, the carrier substrate
5 has a very small edge radius, while the substrate 2 has a very
large edge radius. In the embodiment according to the invention,
two advantages are thus obtained. First, the relatively small edge
radius of the carrier substrate 5 contributes to the fact that a
support surface 5o supporting the substrate 2 after incorporation
on the carrier substrate 5 as much as possible reaches a support
edge 2k of the peripheral contour 2u, which has the result of an
advantageous support of the product substrate 2 by the carrier
substrate 5. The adhesive layer 14 does not have a significant
effect on the support; in particular, the latter has at least the
diameter d3 that is equal to the diameter d2 of the carrier
substrate 5.
[0100] Because of the edge radius, the substrate 2 has an annular
shoulder 2a on its peripheral contour at least on the contact side
of the substrate 2 with the carrier substrate 5, and said shoulder
has an annular width dR that corresponds to at least the difference
between the diameters d2 and d1. The shoulder 2a is distinguished
in this embodiment by continuous reduction of the thickness D.sub.1
of the substrate 2 in the direction of the peripheral contour 2u
and/or by continuous reduction of the diameter of (at most) the
mean diameter d1 up to a diameter dk on the contact side 2o. The
shoulder 2a can be defined in particular by the adhesive layer 14,
in particular by a diameter d3 of the adhesive layer 14.
[0101] In addition, the relatively large edge radius of the product
substrate 2 makes it possible that the diameter d1 of the product
substrate 2 by itself is matched to the diameter d2 of the carrier
substrate 5 by the back-thinning and the shape of the cross-section
of the peripheral contour 2u by the looping-back being carried out
up to at least the shoulder 2a. After an alignment and bonding
process according to the invention (FIG. 3b), a back-thinning
process of the substrate 2 (FIG. 3c) is carried out at least to
above the shoulder of the peripheral contour 2u, i.e., at least up
to the shoulder 2a'.
[0102] It would also be conceivable that the edge radius of the
product substrate 2 is very small, which would increase the usable
surface of the product substrate 2, primarily in the case of very
large wafers, and thus would increase the yield of functional
units, for example chips, 16, provided on the product substrate
2.
[0103] FIGS. 4a-4b show another shortened process of a product
according to the invention (substrate-carrier substrate
combination) with a carrier wafer 5', whose diameter d2 is smaller
than the diameter d1 of a substrate 2'. The edge of the (product)
substrate 2' was looped back according to the invention on the
peripheral contour 2u by an annular width dR to achieve an effect
similar to the effect of the larger edge radius in the embodiment
according to FIGS. 3a to 3c. In this connection, an annular
shoulder 2a is produced. The looping-back is produced in particular
by a process that is known in the industry under the name
"edge-trimming."
[0104] The diameter d2 of the carrier wafer 5' advantageously
equals the diameter d1 of the substrate 2 reduced by the annular
width dR of the circular ring. After an alignment and bonding
process according to the invention (FIG. 4b), a back-thinning
process of the substrate 2' is carried out (FIG. 4c) at least up to
the looped-back section of the peripheral contour 2u, i.e., at
least up to the shoulder 2a'.
[0105] Both products according to the invention have the property
that after the back-thinning, the diameter d2 of the carrier wafer
5, 5' and the diameter d1 of the substrate 2, 2' have a smaller
difference, approximately equal, or the diameter d1 is even smaller
than the diameter d2, by the back-thinning process resulting in a
reduction of the diameter d1 of the substrate 2, 2' because of the
edge shape of the substrate 2, 2'.
[0106] The edge shapes of the substrates are determined by SEMI
standards. There are substrates with different edge profiles
provided for special objects. These edge profiles are produced by
special machines. The shape of the edges is of importance for the
chip yield. To be able to process as many chips as possible on a
substrate, chips must also be produced on the outermost edge areas.
Therefore, it is useful according to the invention to make the edge
geometry as square as possible, or at least rounded with the
smallest possible radius of curvature. As a result, preferably a
wafer is produced with as large an area of use as possible.
[0107] The different wafer edge profiles are defined in the SEMI
standard. The different wafer edge profiles can adopt very
complicated shapes and are described in the rarest cases by a
single parameter. According to the invention, the edge radius is
defined as a parameter that results in a significant rounding of
the wafer edge profile.
[0108] For an embodiment according to the invention, in which the
product wafer is to have as many functional units as possible, the
characteristic edge radius is less than 1 mm, preferably less than
0.5 m, more preferably less than 0.1 mm, most preferably less than
0.001 mm, and with utmost preference equal to 0 mm.
[0109] For an embodiment according to the invention in which the
product wafer is reduced in its thickness by processes after the
bonding process, the calculation of the characteristic edge radius
has to be carried out based on the end thickness of the product
wafer or the diameter of the carrier substrate and/or product
substrate. The characteristic edge radius is larger than 0 mm,
preferably larger than 0.001 mm, more preferably larger than 0.1
mm, most preferably larger than 0.5 mm, and with utmost preference
larger than 1 mm.
[0110] For an embodiment according to the invention, in which the
carrier wafer is optimally to support the product wafer by as large
a surface as possible, the characteristic edge radius of the
carrier wafer is smaller than 1 mm, preferably smaller than 0.5 mm,
more preferably smaller than 0.1 mm, most preferably smaller than
0.001 mm, and with utmost preference equal to 0 mm.
REFERENCE SYMBOL LIST
[0111] 1 Substrate Holding Means
[0112] 2, 2' Substrate
[0113] 2o Contact Side
[0114] 2a, 2a' Shoulder
[0115] 2k, 2k' Support Edge
[0116] 3 Contacting Means
[0117] 4 Carrier Substrate Holding Means
[0118] 5, 5k' Carrier Substrate
[0119] 2u, 5u Peripheral Contours
[0120] 5o Support Surface
[0121] 6 Rotational Means
[0122] 7 Carrier Unit
[0123] 8 Adjustment System
[0124] 9 Base Plate
[0125] 10 Guide Elements
[0126] 11 Distance-Measuring Elements
[0127] 12 Measuring Means
[0128] 13, 13', 13'', 13''' Optics
[0129] 14 Adhesive Layer
[0130] 15, 15' Scanning Unit
[0131] 16 Functional Units
[0132] d1, d2, d3, dk Mean Diameter
[0133] dR Mean Annular Width
[0134] D.sub.1 Thickness
* * * * *