U.S. patent application number 10/478285 was filed with the patent office on 2004-07-01 for device for accommodating disk-shaped objects and apparatus for handling objects.
Invention is credited to Chung, Hin Yiu, Drechsler, Martin, Graf, Ottmar, Grandy, Michael, Mantz, Paul, Niess, Jurgen, Pelzmann, Arthur.
Application Number | 20040126213 10/478285 |
Document ID | / |
Family ID | 7685532 |
Filed Date | 2004-07-01 |
United States Patent
Application |
20040126213 |
Kind Code |
A1 |
Pelzmann, Arthur ; et
al. |
July 1, 2004 |
Device for accommodating disk-shaped objects and apparatus for
handling objects
Abstract
A device for receiving plate-shaped objects, preferably
semiconductor wafers, for the thermal treatment thereof, enabling
the processing of wafers made of connecting semiconductors in a
particularly simple manner. The inventive device offers high
productivity and low risk of damage as a carrier has at least two
recesses for respectively receiving an object. The recesses on the
carrier can preferably be provided with covers. Preferably, support
pins are provided for loading and unloading purposes. The carrier
and the support pins can move in a vertical direction in relation
to each other. A handling device for objects is also disclosed.
Inventors: |
Pelzmann, Arthur; (Gunzburg,
DE) ; Drechsler, Martin; (Memmingen, DE) ;
Niess, Jurgen; (Sontheim, DE) ; Grandy, Michael;
(Senden, DE) ; Chung, Hin Yiu; (Elchingen, DE)
; Mantz, Paul; (Ehingen, DE) ; Graf, Ottmar;
(Bergatreute, DE) |
Correspondence
Address: |
Robert W Becker & Associates
Suite B
707 Highway 66 East
Tijeras
NM
87059
US
|
Family ID: |
7685532 |
Appl. No.: |
10/478285 |
Filed: |
November 18, 2003 |
PCT Filed: |
May 2, 2002 |
PCT NO: |
PCT/EP02/04790 |
Current U.S.
Class: |
414/416.01 |
Current CPC
Class: |
H01L 21/6835 20130101;
H01L 21/68735 20130101; H01L 2221/68313 20130101; H01L 21/68771
20130101; H01L 21/68764 20130101; H01L 21/67109 20130101; H01L
21/68742 20130101 |
Class at
Publication: |
414/416.01 |
International
Class: |
B65B 021/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 18, 2001 |
DE |
101 24 647.1 |
Claims
1. Device for accommodating disk-shaped objects, preferably
semiconductor wafers, for the thermal treatment thereof,
characterized by a carrier having at least two recesses
respectively receiving an object.
2. Device according to claim 1, characterized by at least one cover
for covering at least one recess.
3. Device according to claim 1 or 2, characterized in that the
carrier and/or at least one of the covers is made of graphite,
sapphire, quartz, boron nitride, aluminum nitride, silicon, silicon
carbide, silicon nitride, ceramic and/or metal.
4. Device according to one of the preceding claims, characterized
in that the carriers and/or the covers have a thermal capacity
between 0.2 J/gK and 0.8 J/gK.
5. Device according to one of the preceding claims, characterized
in that the carrier and/or the covers have a thermal capacity
between 10 W/mK and 180 W/mK.
6. Device according to one of the preceding claims, characterized
in that at least parts of the carrier and/or of the covers are
coated.
7. Device according to one of the preceding claims, characterized
in that at least portions of the carrier and/or of the covers are
transparent.
8. Device according to one of the preceding claims, characterized
in that gas atmospheres that differ from one another are provided
in the individual recesses.
9. Device according to one of the preceding claims, characterized
in that the objects are disposed in one plane.
10. Device according to one of the preceding claims, characterized
in that the objects are disposed in at least two planes that are
parallel to one another and are spaced from one another.
11. Device according to claim 10, characterized in that at least
two recesses have different depths.
12. Device according to one of the preceding claims, characterized
in that at least one object rests flat upon a base surface of the
recess.
13. Device according to one of the claims 1 to 10, characterized in
that at least one object is spaced from the base surface of the
recess.
14. Device according to claim 13, characterized in that at least
one object rests upon support elements.
15. Device according to claim 13, characterized in that at least
one object rests in its edge region.
16. Device according to one of the preceding claims, characterized
in that at least one recess has a conical configuration in at least
its outer region.
17. Device according to one of the preceding claims, characterized
in that at least one recess has a concave configuration.
18. Device according to one of the preceding claims, characterized
in that at least two recesses have different dimensions.
19. Device according to one of the preceding claims, characterized
in that at least two of the objects have different dimensions.
20. Device according to one of the preceding claims, characterized
in that the objects are combination semiconductors.
21. Device according to one of the preceding claims, characterized
in that at least two of the objects have different materials.
22. Device according to one of the preceding claims, characterized
in that the objects are at least partially coated.
23. Device according to one of the preceding claims, characterized
in that the object material is non-homogeneous.
24. Device according to one of the preceding claims, characterized
by support pins for the loading of the carrier with objects and/or
covers.
25. Device according to claim 24, characterized in that the support
pins pass through the carrier.
26. Device according to claim 24 or 25, characterized in that the
pins have different heights.
27. Device according to one of the claims 24 to 26, characterized
in that the support pins for the covers are higher than for the
objects.
28. Device according to one of the claims 24 to 27, characterized
in that at least one support pin for the covers is provided
externally of the carrier.
29. Device according to one of the claims 24 to 28, characterized
in that the carrier and the support pins are movable relative to
one another in the vertical direction.
30. Device according to claim 29, characterized in that the support
pins are movable vertically downwardly for the placement of the
objects into the recesses and/or for the placement of the covers
upon the carrier.
31. Device according to claim 29, characterized in that the support
pins are movable vertically upwardly for raising the objects out of
the recesses and/or for raising the covers from the carrier.
32. Device according to claim 29, characterized in that the carrier
is movable vertically.
33. Device according to one of the preceding claims, characterized
by a gripper having suction devices for the deposit of the objects
into the recesses and/or upon the support pins, and/or for the
removal of the objects from the recesses and/or from the support
pins.
34. Device according to one of the preceding claims, characterized
by a rotary device for the rotation of the carrier about a vertical
axis.
35. Device according to one of the preceding claims, characterized
in that the carrier can be loaded within a process chamber.
36. Device according to one of the preceding claims, characterized
in that the carrier can be loaded externally of the process
chamber.
37. Device according to one of the preceding claims, characterized
by an automatic loading and unloading device.
38. Handling apparatus having at least one transport arm that is
provided with at least one support device for the support, via
vacuum, of at least one object that is to be handled, characterized
by a vacuum control device for the alteration of the vacuum as a
function of the weight of the object.
39. Handling apparatus according to claim 38, characterized in that
the vacuum control device includes a vacuum source and vacuum
change-over devices.
40. Handling apparatus according to claim 38 or 39, characterized
in that the vacuum change-over device is provided with switches for
the change-over between lines with and without vacuum
regulators.
41. Handling apparatus according to one of the claims 38 to 40,
characterized in that the vacuum control device has at least two
separate vacuum systems.
42. Handling apparatus according to one of the preceding claims,
characterized in that the vacuum ratio for the objects that are to
be handled and that have different weights is in a range of from 10
to 10,000.
43. Handling apparatus according to one of the claims 38 to 42,
characterized in that an object with lesser weight is a
semiconductor wafer, and an object with greater weight is a
semiconductor wafer receptacle.
44. Handling apparatus according to one of the claims 38 to 43,
characterized in that the support device is differently embodied
for the different objects.
45. Handling apparatus according to one of the claims 38 to 44,
characterized in that a three-point support device is provided.
46. Handling apparatus according to one of the claims 38 to 45,
characterized in that support devices are provided on both sides of
the transport arm.
47. Handling apparatus according to claim 38 to 46, characterized
in that one side of the transport arm has support devices for the
object with greater weight, and its other side has support devices
for the object of lesser weight.
48. Handling apparatus according to claim 46 or 47, characterized
in that the transport arm is rotatable about 180.degree. relative
to its longitudinal axis.
49. Handling apparatus according to one of the claims 38 to 48,
characterized in that at least two transport arms are provided, of
which at least one is provided for the support of objects having
greater weight and at least one further one is provided for the
support of objects of lesser weight.
50. Handling apparatus according to one of the claims 38 to 49,
characterized in that the vacuum control device is controllable as
a function of a prescribed program sequence.
51. Handling apparatus according to one of the claims 38 to 50,
characterized by a sensor that measures the weight of the object
that is to be handled, and with the output signal of which the
vacuum control device can be controlled.
Description
[0001] The present invention relates to a device for accommodating
disk-shaped objects, preferably semiconductor wafers, for the
thermal treatment thereof. The invention also relates to a handling
apparatus for objects.
[0002] For the industrial manufacture of electronic components,
semiconductor materials having a disk-shaped configuration, so
called wafers, are subjected to thermal treatments. Especially the
thermal processing of objects, such as wafers, by means of rapid
heating units, also known as RTP units (Rapid Thermal Processing)
is continuously being emphasized. The main advantage of RTP units
is their high throughput, which is based upon the possibility of
being able to very rapidly heat up the wafers. Heating rates of up
to 300.degree. C./s can be achieved in RTP units.
[0003] An RTP unit essentially comprises a transparent process
chamber in which a wafer that is to be processed can be disposed
upon suitable support devices. Furthermore, in addition to the
wafer, diverse auxiliary elements, such as, for example, a
light-absorbing plate, a compensation ring that spans the wafer, or
a rotation or tilting device for the wafer can be disposed in the
process chamber. The process chamber can be provided with suitable
gas inlets and outlets in order to be able to produce a prescribed
atmosphere within the process chamber in which the wafer is to be
processed. The wafer is heated by a thermal radiation that issues
from a heating device that can be disposed either above the wafer
or below the wafer or on both sides, and is composed of a plurality
of lamps, rod or point-type lamps, or a combination thereof. The
overall arrangement can be surrounded by an external chamber, the
inner walls of which are entirely or at least partially
reflective.
[0004] In alternative RTP units, the wafer is placed upon a heating
plate or susceptor, and is heated by a thermal contact with this
susceptor.
[0005] With connecting or combination semiconductors, such as III-V
or II-IV semiconductors, such as, for example, GaN, InP, GaAs or
tertiary compounds such as, for example, InGaAs or quaternary
compounds such as InGaAsP, there is, however, the problem that
generally one component of the semiconductor is volatile and upon
heating of the wafer evaporates out of the wafer. There results
predominantly in the edge region of such wafers a heating zone with
a reduced concentration of the evaporated-out component. The result
is an alteration of the physical characteristics, such as, for
example, the electrical conductivity, of the wafer in this region,
which can make the wafer unusable for the production of electrical
components.
[0006] From the two publications U.S. Pat. No. 5,872,889 A and U.S.
Pat. No. 5,837,555 A, which originate with the applicant, it is
known to dispose wafers of combination semiconductors in a closed
receptacle of graphite for the thermal treatment. Due to its
stability at high temperatures, graphite is particularly suitable
for such receptacles. The wafer is placed upon a support that has a
recess for accommodating the wafer. Placed over the recess is a
lid-like cover, so that a closed space results in which the wafer
is disposed. This graphite receptacle in which the wafer is
contained is subjected to a thermal treatment in the process
chamber of an RTP unit. In this way, a diffusing-out of a component
of the combination semiconductor is suppressed, and the wafer can
be safely processed.
[0007] The described graphite receptacle is predominantly used for
processing wafers of a combination semiconductor having diameters
of 200 mm and 300 mm. However, very common are also wafers of
combination semiconductors having small diameters of 50 mm, 100 mm,
or 150 mm.
[0008] It is an object of the present invention to provide a device
with which wafers of combination semiconductors can be safely
processed in a simple manner and at high productivity.
[0009] Pursuant to the invention, this object is realized by a
carrier having at least two recesses for respectively receiving a
wafer. With such carriers, a plurality of wafers can be processed
simultaneously. In contrast to the known treatment methods, this
means a considerable increase of the throughput of an RTP unit, and
represents a significant economical advantage.
[0010] Pursuant to one particularly advantageous embodiment, the
inventive device has at least one cover for covering at least one
recess in order to provide an essentially closed-off space about
the objects.
[0011] For example, a single large cover is possible that covers
all of the recesses of the carrier with the wafers contained
therein. However, alternatively each recess could also be covered
by individual covers. It is also possible that one of the covers
simultaneously covers any desired number of recesses, although more
than one and not all of them, or any desired number of the recesses
can be individually covered and the remainder of the recesses can
remain uncovered. Such a cover can be combined in any desired
manner with other similar covers as well as with individual covers
for a respective recess and with non-covered recesses.
[0012] The carrier that is provided with the recesses is preferably
made of graphite, sapphire, quartz, boron nitride, aluminum
nitride, silicon, silicon carbide, silicon nitride, ceramic or
metal. Similarly, at least one of the covers can be made of
graphite or sapphire or quartz or boron nitride or aluminum nitride
or silicon or silicon carbide or silicon nitride or ceramic or
metal. However, not only the carrier but also at least one or all
of the covers can also be made of the aforementioned materials.
[0013] For RTP processes, advantageously carriers are used having
at least one cover that has a low specific thermal capacity,
preferably 0.2 to 0.8 J/gK, of the carrier and/or of at least one
cover. For this reason, the carrier should have as low a thickness
as possible.
[0014] Similarly, carriers having at least one cover are
advantageous where the carrier and/or at least one of the covers
has a high thermal conductivity, preferably 10 to 100 W/mK.
[0015] At least parts of the carrier, or parts of one of the
covers, or parts of the carrier and parts of one of the covers, are
preferably coated. For example, it can be advantageous to at least
partially provide an inner surface of one or of all of the
recesses, as well as a surface that covers the recess of one or
more of the covers, with a coating that is inert to chemical
processes that take place within the covered recesses during the
processing of the wafer, whereas external surfaces of the carrier
remain uncoated in order to have desired absorption characteristics
relative to the thermal radiation. In other cases, for example
local optical characteristics of carrier and covers can be achieved
by suitable area wise coatings of the outer surfaces.
[0016] Similarly, it can be advantageous to make at least parts of
the carrier, or parts of at least one of the covers or parts of the
carrier and parts of at least one of the covers, transparent for
the thermal radiation by making them, for example, of quartz or
sapphire. The covers, as well as parts of the carrier that
correspond to the base surfaces of the recesses, are advantageously
nontransparent for the thermal radiation, while the other parts of
the carrier are transparent.
[0017] It is furthermore possible to produce predetermined
atmospheres within covered recesses. Depending upon the type of
wafer that is to be processed, a different atmosphere can exist in
each covered recess. For example, if in at least one first recess a
InP wafer is processed, a phosphorous-containing atmosphere exists
in the recess. In at least one second recess in which a GaAs wafer
is to be processed, an arsenic-containing atmosphere exists.
Finally, in at least one third, optionally not covered recess a
wafer can be processed that comprises silicon, in other words not a
combination semiconductor.
[0018] At least some of the wafers accommodated by the carrier can
be at least partially coated. However, the volume material of at
least one of the wafers can also vary in zones in that the wafer is
provided, for example, with an implanted layer.
[0019] The inventive carrier for a plurality of wafers, which are
subjected to a thermal treatment in common in a process chamber,
makes it possible during the same process stage to achieve
different process results with the same course of the thermal
radiation for each wafer. Depending upon the coating or
transparency of local regions of the carrier and/or of the
corresponding cover, locally different optical conditions can be
achieved that lead to different temperatures in the interior of the
covered recesses. Thus, each wafer experiences an individual
process temperature, although the course of the thermal radiation
is the same for all wafers. Thus, with one processing stage it is
possible not only to simultaneously treat a plurality of wafers,
but in so doing the wafers can even be subjected to different
processes. This means that wafers of different materials can be
treated simultaneously.
[0020] The recesses in the carrier preferably have the same depth,
so that after loading of the carrier the wafers are all disposed
parallel and in the same plane.
[0021] However, it can also be advantageous to vary the depths of
the recesses. In this case, although the wafers are always disposed
parallel to one another, they are offset with respect to height and
are disposed at different planes.
[0022] For cylindrical recesses having flat horizontal bases, the
wafers rest flat on the base of the recess.
[0023] A support of the wafers within at least one recess is
advantageously selected, whereby a contact between wafer and the
base of the recess is avoided. This is advantageously achieved by
pin-shaped support elements that are disposed in the recess and
which accommodate the wafer. With the same depth of the recesses
but different lengths of the support elements, the wafers can then
be disposed at planes of different heights.
[0024] Another preferred possibility of arranging the wafers such
that a contact with the base of the recess is avoided is to support
the rim portion of the wafer. This is achieved by making at least
one recess so that it tapers conically inwardly. In this way, an
inwardly beveled edge of the recess is obtained that leads to a rim
support of a wafer. Pursuant to another embodiment, at least one
recess has a concave configuration that again leads to supporting
the rim of the wafer on the edge of the recess. Depending upon the
design of the conical and of the concave recesses, the wafer can be
placed at different heights.
[0025] To load the carrier, the wafers are advantageously
sequentially placed via a gripper directly into the recesses or
onto support pins. Suitable for this purpose are grippers having
suction devices that draw the wafers against them. This can be
effected via a suction device that operates according to the
Bernoulli principle.
[0026] Support pins are advantageously provided for the loading of
the carrier and preferably extend through the carrier. These
support pins advantageously have different heights for different
recesses in order not to obstruct a loading of the recesses that
are remote from the gripper by the support pins that are provided
for loading the recesses that face the gripper.
[0027] Similarly, the covers can be placed upon support pins that
either extend through the carrier or are disposed entirely
externally of the carrier. The support pins for the covers are
advantageously longer than the support pins for the wafers.
[0028] The support pins and the carrier are preferably vertically
movable relative to one another.
[0029] As soon as the wafers are placed upon the support pins, the
support pins move downwardly through the carrier, as a result of
which the wafers are raised from the support pins and are deposited
in the recesses associated with them. Alternatively, the carrier
could also be moved upwardly.
[0030] Another preferred method for loading the carrier
sequentially rotates the carrier about a vertical axis in order to
respectively rotate the recess that is to be loaded to the
gripper.
[0031] As soon as the carrier is loaded with the wafers, the
corresponding covers can either be place directly upon the carrier
or upon support pins by the gripper if they were not already placed
upon appropriate support pins prior to the wafers.
[0032] A loading of the carrier is preferably effected within the
process chamber. However, it can also be loaded externally of the
process chamber and can subsequently be introduced into the process
chamber for the thermal treatment.
[0033] A plurality of such carriers with covers can, for example,
advantageously be stacked one above or next to each other within a
process chamber for a thermal treatment.
[0034] The loading and unloading of the carrier with the substrates
and/or covers is preferably effected with an automatic loading and
unloading unit which can be appropriately controlled in
correspondence to the loading and unloading processes.
[0035] The inventive device is preferably, although not
exclusively, particularly suitable for wafers of combination
semiconductors having predominantly small diameters. The thermal
treatment of the semiconductor wafers is preferably effected in RTP
units in which prescribed environmental conditions and temperature
profiles can be set. In this connection, during the treatment the
carrier is extensively stable at the environmental conditions and
the temperatures.
[0036] Semiconductor wafers, especially combination semiconductor
wafers, as they were previously described, are relatively thin and
have thicknesses of 50 to 500 .mu.m, and customarily 200 .mu.m.
These wafers are therefore very susceptible to breakage during the
handling, so that with the conventional handling by hand or with
handling apparatus, such as robots and the like, breakage of the
wafers frequently occurs, thus considerably reducing the yield
during the manufacture of the semiconductors. Especially with
semiconductor wafers that are used for expensive components, such
as, for example, laser diodes, this is particularly evident, since
a two-inch wafer for this purpose has a value in the range of
25,000.
[0037] As already indicated previously, the wafers are treated in
receptacles that are made, for example, of graphite and are
introduced into a process chamber for the treatment of the wafers.
These so-called graphite boxes have a weight of 200 to 2,000 g,
depending upon the number and the size of the wafers that are to be
accommodated in the boxes.
[0038] Not only the wafers but also the receptacles themselves are
manually handled with such units, since with conventional handling
apparatus it is not possible on the one hand to handle the very
thin semiconductor wafers that have a weight in the range of 0.1 to
20 g, and on the other hand to handle the receptacles that in
contrast are heavy, without having a high reject rate due to
breakage of wafers.
[0039] It is therefore furthermore an object of the present
invention to provide a handling apparatus with which objects having
different weights can be securely and reliably handled.
[0040] Pursuant to the invention, the stated object is realized
with a handling apparatus having at least one transport arm, which
in turn has at least one support device for supporting, via vacuum,
at least one object that is to be handled, by a vacuum control
device for altering the vacuum as a function of the weight of the
object.
[0041] Due to the inventive feature of providing a vacuum control
device via which the vacuum of support devices on the transport
arms can be set, controlled or regulated as a function of the
weight of the object, it is now possible to transport and handle,
with one and the same handling apparatus, objects having very
different weights. For example, with the inventive handling
apparatus it is possible to undertake the handling and the
transport of wafers and wafer receptacles while avoiding manual
handling, and in particular in such a way that on the one hand, for
example, relatively heavy receptacles can be handled with the same
handling apparatus as are the very thin, breakable wafers having a
low weight while avoiding breakage of the wafers. The inventive
handling apparatus thus enables, for example, not only the loading
and unloading of receptacles into or out of the process chamber,
but also the loading and unloading of the thin, breakable wafers
into and out of the receptacle. Aside from the fact that in so
doing the possibility of a complete automation of the processing of
semiconductor wafers, especially also in conjunction with thermal
treatments, is provided, this takes place with a single handling
apparatus, so that equipment costs can thereby be kept low. With
the process automation that has become possible with the inventive
handling apparatus, the production yield is significantly increased
since breakage of wafers, as frequently occurs during manual
loading and unloading of the receptacle and of the process chamber,
is avoided or at least significantly reduced. A treatment unit
having the inventive handling apparatus is therefore amortized
considerably earlier than are conventional treatment units due to
the low rejection rate and the rapid and reliable handling,
especially if the unit is used for manufacturing very expensive
components.
[0042] Pursuant to one preferred embodiment of the invention, the
vacuum control device includes only one vacuum source and vacuum
change-over devices, for example line change-over switches, for
switching between a line with and without a vacuum regulator. In
this way, only one vacuum source is required, whereby the vacuum
regulator is preferably an adjustable valve. Pursuant to an
alternative embodiment, at least two separately controllable vacuum
systems are provided.
[0043] Pursuant to one advantageous embodiment of the invention,
the pressure ratio for the objects that are to be handled and that
have different weights is in a range of from 10 to 10,000. This
vacuum ratio is essentially a function of the weight ratio of the
objects that are to be handled and also of the design of the
support devices.
[0044] Pursuant to a very advantageous embodiment of the invention,
an object having a low weight is a silicon semiconductor wafer, and
an object having a greater weight is a receptacle in which the
wafers are disposed during at least one treatment step. Receptacles
of this type have been described previously by way of example.
[0045] Although the support devices for objects having different
weights can be embodied in the same manner, it is, however,
advantageous pursuant to a further embodiment of the invention to
also embody the support devices differently for the different
objects, especially for objects having different weights. The
support devices are preferably so-called pads or support cushions
that are connected via a line with a vacuum source or a vacuum
system. The individual support devices or pads can be supplied with
the same vacuum, or they can also be supplied with respectively
different vacuums, which in this case, however, requires
appropriate control elements, such as, for example, valves or
separate vacuum systems.
[0046] In this connection, the support devices are preferably
adapted to the objects having different weights, for example also
to the shape and surface structure of the objects. For example, for
supporting the receptacle generally larger support surfaces are
required than for supporting the light wafers. For example, it is
advantageous for wafers to select the diameter of the support
devices or pads to be approximately 3 mm, or the surface upon which
the vacuum acts per pad to be approximately 0.1 cm.sup.2. The shape
of the pads is to be selected in conformity with the prescribed
requirements, and it can be round or rectangular or have some other
configuration. However, the pads are preferably round, since here
the ratio surface/rim is the greatest, and in so doing even at a
low suction power of the vacuum source a reliable holding of the
object, for example the wafer, is ensured.
[0047] So that a wafer having a weight of, for example, 0.1 g to
0.5 g can be reliably held, the contact pressure produced by the
pads, and via which the wafer is pressed against the support, must
be great enough that the frictional force resulting from the
contact pressure is greater than the forces produced by
acceleration of the transport arm or the acceleration due to
gravity, which act upon the object, for example the wafer. With
wafers this is achieved, for example, via a vacuum of approximately
0.005 bar (this corresponds to an absolute pressure of 0.995 bar),
if the (horizontal) acceleration forces acting upon the wafer are
less than 1 g. In this connection, one must take into account the
frictional coefficient between wafer and support, which can again
be a function of wafer temperatures.
[0048] If the vacuum is greater, i.e. the absolute pressure
smaller, the wafer will still always be reliably held, in other
words, the acceleration force can exceed 1 g, although there then
exists the danger of wafer breakage.
[0049] In general, the pad pressure that is to be selected is to be
adapted to the maximum acceleration that occurs, as a result of
which it is advantageous if the pressure is preferably controllable
or regulatable. A vacuum that is too great is to be avoided. The
adaptation of pressure can be effected not only prior to the start
of the movement sequence but also during the movement itself. The
maximum permissible acceleration of the wafer is a function of the
thickness of the wafer and its diameter, the material and the type
of wafer surface in the support region, in other words, also
whether or not a structured or unstructured support region is
provided.
[0050] If wafers having unstructured support regions are handled,
an arrangement of the pads at approximately {fraction (2/3)} of the
wafer radius-relative to the center of the wafer-is preferably
selected. In this way, the wafer is supported in a manner that is
as free of stress as possible. With structured support regions, the
pads preferably support the rim region of the wafer.
[0051] The inventive handling apparatus is preferably provided with
a three-point support device for the object having greater weight
and/or for the object with lesser weight.
[0052] As already indicated, in this connection the support devices
for the different objects, and in particular those having different
weights, preferably have different configurations.
[0053] The support devices for the objects that in particular
differ with regard to their weight can both be disposed on one side
of the transport arm. Pursuant to a particularly advantageous
embodiment of the invention, however, support devices are provided
on both sides of the transport arm. This makes it possible to hold
the objects that are to be handled during the handling process on
the upper side or on the underside of the transport arm depending
upon the given conditions. Pursuant to a further embodiment of the
invention, it is particularly advantageous if there is provided on
one side of the transport arm support devices for the heavier
object and on the other side support devices for the lighter
object. The one side, for example the upper side, has a first
support or pad structure or support surface structure, for example
for supporting receptacles, while on the underside of the transport
arm there is provided a second support or pad structure, for
example for supporting the wafer. For example, the wafer is held
from below and the receptacle from above, or vise versa. With such
an embodiment of the inventive handling apparatus, it is also
possible to eliminate a vacuum control and to operate both support
devices with the same vacuum, since the holding forces are
determined or codetermined by the differing pad structures,
especially the differing surface conditions. In addition, the
frictional coefficients of the support surfaces can differ from
above and below.
[0054] Pursuant to a further very advantageous embodiment of the
invention, the transport arm is rotatable by 180.degree. relative
to its longitudinal axis.
[0055] As a result, the side with the support device adapted to a
corresponding object can be rotated upwardly or downwardly.
[0056] Pursuant to a further embodiment of the invention, at least
two transport arms are provided, of which at least one is provided
for supporting a heavier object and at least one further one is
provided for supporting a lighter weight object. In this way, the
support devices are respectively provided on their own transport
arm separately from one another for the respective different
objects.
[0057] Pursuant to a further advantageous embodiment of the
invention, the vacuum control device can be controlled as a
function of a prescribed program sequence. Alternatively or in
addition to this possibility, it is particularly advantageous if a
sensor, for example a wire strain gauge, is provided for measuring
the weight of the object that is to be handled. The result of this
weight measurement, in other words the output signal of the sensor,
is subsequently utilized for controlling the vacuum control device.
In this connection, the sensor can be provided directly on the
transport arm or it is, however, also possible to first slightly
raise the object, the weight of which is to be determined, whereby
the support pressure for supporting the object is determined as a
measure for the weight of the object. By determining its individual
weight, the object is reliably held during the movement. With this
individual support pressure, the object is then moved. In addition
to the actual support pressure, it is also possible to select or
set the maximum acceleration, a selection of a previously fixed
trajectory of the object, the speed or some other movement
parameter. In this way, it is also possible to control so-called
edge grippers that grasp the rim of the object, for example a wafer
or a box, and fix the object at the rim in order to achieve a
localized fixing of the object in position relative to the handling
apparatus. Such a firm holding can be effected, for example,
mechanically, wherein the term "holding pressure" is also to be
understood to mean a mechanical contact pressure of mechanical
parts of the handling apparatus against the object.
[0058] The present invention will be explained in greater detail
subsequently with the aid of preferred embodiments of the invention
in conjunction with the drawings, in which:
[0059] FIG. 1 is a schematic cross-sectional illustration through a
rapid heating unit;
[0060] FIGS. 2a) and 2b) show a carrier for accommodating up to
seven wafers, in plan and in cross-section along the section line
indicated in FIG. 2a);
[0061] FIG. 3a) to 3f) show various embodiments of the cover of
recesses in the carrier;
[0062] FIG. 4 shows two illustrations of alternative combinations
of recess with wafer and cover;
[0063] FIG. 5 shows various embodiments for recesses;
[0064] FIG. 6 shows a mechanism for the loading and unloading of
the carrier;
[0065] FIG. 7 shows a schematic illustration of a transport arm of
an inventive handling apparatus in plan;
[0066] FIG. 8 shows a side view of the transport arm illustrated in
FIG. 7;
[0067] FIG. 9 shows the schematic illustration of an embodiment of
a vacuum control device;
[0068] FIGS. 10a) and 10b) show schematic illustrations of a
transport arm, which is rotatable about it longitudinal axis, in
plan from above and below.
[0069] FIG. 1 schematically shows a typical unit 1 for the rapid
thermal treatment of objects, preferably disk-shaped semiconductor
wafers 2. The wafer 2 is placed upon a holding or support device 3
which can, for example, be pin-shaped support elements or a device
upon which the wafer is peripherally disposed, or some other type
of wafer support. The wafers 2, including the support device 3, are
disposed in the interior of a process chamber 4. The process
chamber 4 is a transparent chamber that is preferably manufactured
at least in part of transparent quarts. Not indicated are inlets
and outlets for process gases by means of which a gas atmosphere
that is suitable for the process can be produced. Mounted above
and/or below and/or to the side--the latter not being indicated
here--of the process chamber 4 are banks of lamps 5 and 6. These
are preferably a plurality rod-shaped tungsten-halogen lamps that
are disposed parallel to one another; However, other lamps could
also be utilized. Alternative embodiments of the chamber eliminate
either the upper bank of lamps 5 or the lower bank of lamps 6
and/or the laterally disposed lamps. By means of the
electromagnetic radiation emitted from the lamps, the object 2, for
example a wafer, is heated. The entire arrangement can be
surrounded by an external furnace chamber 7, the inside of the
walls of which can be at least partially provided with a reflective
surface, and they can preferably be made of a metal such as steel
or aluminum. Finally also present is a measurement device, which
preferably comprises two non-contact measurement devices 8 and 9.
The measurement devices 8 and 9 are preferably two pyrometers;
however, CCD monitors or sensors, or other devices for registering
radiation, can also be used.
[0070] In order to be able to successfully thermally treat
connecting ofrcombination semiconductors in such a unit, the
semiconductors must be enclosed in a container in order to
counteract a decomposition of the semiconductor material. FIG. 2a)
illustrates in plan a preferred round disk-shaped carrier 10. FIG.
2b) shows a cross-section through the carrier 10 along the dot-dash
line in FIG. 2a).
[0071] The carrier 10 has a plurality of circular recesses 11 to 17
of the same diameter in an upper disk surface 18 for respectively
receiving a wafer. However, different diameters for the recesses
are also possible. In this connection, one recess 12 is centrally
disposed in the carrier 10, while the remaining six recesses 11,
13, 14, 15, 16 and 17 surround the central recess 12 along a circle
that is concentric to the central recess 12 and to the edge of the
carrier. The diameter of the carrier 10 is preferably 200 mm, and
the diameter of the same size recesses is preferably 52 mm.
[0072] The carrier 10 is preferably made of graphite, sapphire,
quartz, boron nitride, aluminum nitride, silicon, silicon carbide,
silicon nitride, ceramic or metal. The upper side 18, as well as
the underside 19 of the carrier, are advantageously finely blasted
with glass beads in order to ensure an optical homogeneity on the
upper side 18 and on the underside 19.
[0073] To obtain closed containers or receptacles for the wafers 3
deposited in the recesses 11 to 17, the latter are provided with at
least one cover, which can also be finely blasted with glass beads.
In FIG. 3a), all of the recesses 11 to 17, with the wafers
contained therein, are covered by means of a large cover 20. In
another preferred form of the cover shown in FIG. 3b), the recesses
11 to 17 are individually provided with covers 21 to 27. In FIG.
3c) the recesses 14 and 13 are covered by the cover 28, the
recesses 11 and 17 are covered by the cover 29, and the recesses
15, 12 and 16 are covered by the cover 30. FIG. 3b) shows an
alternative form of the cover, where one of the covers can
simultaneously cover an arbitrary member of recesses, however more
than one and not all of them. Here the recesses 15, 12, 16, 11 and
17 are covered by the cover 31, and the recesses 14 and 13 are
covered by the cover 28. In FIG. 3e), a cover for several recesses
is combined with individual covers, with the recesses 15, 12 and 16
being covered by the cover 30, while the recesses 14, 13, 11 and 17
are covered by the corresponding covers 24, 23, 21 and 27. FIG. 3f)
finally shows a combination of individual covers, covers for a
plurality of recesses, and non-covered recesses. Thus, as in FIG.
3e), the recesses 15, 12 and 16 are covered by one cover 30, the
recesses 14 and 13 are covered by the corresponding individual
covers 24 and 25, while the recesses 11 and 17 remain uncovered. In
general, covers for any number of recesses can be combined in any
desired manner with individual covers as well as with non-covered
recesses.
[0074] The covers are not limited to an upper surface 18 of the
carrier 10, and can project laterally beyond the cover 10.
[0075] As with the cover 10, at least one of the covers shown in
the FIG. 3 can be made of graphite, sapphire, quartz, boron
nitride, aluminum nitride, silicon, silicon carbide, silicon
nitride, ceramic or metal. However, not only the carrier 10 but
also at least one of the covers can also be made of the
aforementioned materials.
[0076] For RTP processes, one advantageously selects carriers 10
having at least one cover that has a low specific thermal capacity
of the carrier and/or of at least one cover. The thermal capacity
is preferably between 0.8 J/gK and 0.2 J/gK. For this reason, the
carrier 10 should have as small a thickness as possible that does
not exceed 5 mm. A carrier thickness of up to 3 mm is
preferred.
[0077] Similarly, carriers 10 having at least one cover are
advantageous where the carrier 10 and/or at least one of the covers
has a high thermal conductivity. The thermal conductivity is
preferably between 10 W/mK and 180 W/mK.
[0078] The covers can, as the cover 33 shown in FIG. 4a), be placed
upon the carrier 10 and cover the recess 32 with the wafer 2
disposed therein. The cover 33 is preferably provided with
knob-shaped formations 34 or similar corresponding devices that fit
precisely in corresponding depressions 35 on the upper surface 18
of the carrier 10 and fix the cover 33 in place to prevent it from
slipping. However, such devices can also be dispensed with.
[0079] Preferred is an embodiment where the recess 32, as shown in
FIG. 4b), is provided with an indentation 36 that surrounds it in
the manner of a ring and in which the cover 33 is accommodated. The
depth of the indentation 36 is advantageously the same as the
thickness of the cover 33 in order to provide a flushness with the
upper surface 18 and to ensure a planar upper surface of the
carrier 10. At least portions of the carrier 10, or portions of one
of the covers 20 to 31, or portions of the carrier 10 and portions
of at least one of the covers 20 to 31, are advantageously coated.
Thus, for example, it can be advantageous to provide an inner
surface of one or of all of the recesses 11 to 16, as well as a
surface of one or more covers 20 to 31 that cover the recess, at
least partially with a specific layer that is inert to chemical
processes that occur while processing the wafer 3 within the
covered recess 11 to 16, while external surfaces of the carrier 10
remain uncoated in order to exhibit desired absorption
characteristics relative to the heat radiation. In other cases, for
example local optical characteristics of the carrier 10 and the
covers 20 to 31 can be achieved by suitable coating of regions of
the outer surfaces.
[0080] Similarly, it can be advantageous if at least portions of
the carrier 10, or portions of one of the covers 20 to 31, or
portions of the carrier 10 and portions of one of the covers 20 to
31, are transparent for the heat radiation by making them, for
example, of quartz or sapphire. The covers 20 to 31 as well as
parts of the carrier 10 that correspond to the base surfaces of the
recesses, are advantageously non-transparent for the heat
radiation, while the other parts of the carrier 10 are
transparent.
[0081] In a preferred embodiment of the carrier 10, all of the
recesses 20 to 31 have the same depth. In this way the loaded
wafers 2 have a parallel orientation and are all in one plane and
at the same height.
[0082] However, it can sometimes also be advantageous for the
depths of the recesses 20 to 31 to differ. In this case, although
the wafers 2 are always still parallel, they are offset from one
another in height and are disposed at various planes.
[0083] A support of the wafers 2 is advantageously selected within
at least one of the recesses 11 to 17 to avoid a contact between
the wafer and the base of the recess. As shown in FIG. 5a), this is
advantageously achieved by pin-shaped support elements 37 that are
disposed within a recess 32 and by which the wafer 2 is
accommodated. With recesses having the same depth but with
different lengths of support elements 37, the wafers 2 can then be
disposed at different planes in each recess.
[0084] FIG. 5b) shows another preferred possibility for disposing
the wafer 2 in such a way that a contact with a base of the recess
32 is avoided. Here the wafer 2 is supported in its rim region in
that the recess 32 tapers conically inwardly. In this way there is
achieved an inwardly beveled edge of the recess 32 that enables a
rim support of the wafer.
[0085] With another embodiment shown in FIG. 5c), a recess 32 is
concavely configured, which again leads to a supporting of the rim
of the wafer 2 upon the edge of the recess 32. Depending upon the
design of the conical and of the concave recesses 32, one can place
the wafers at different heights.
[0086] To load the carrier 10, a gripper is utilized that operates,
for example, via a suction device, for example according to the
Bernoulli principle. This gripper successively receives the wafers
2 and places them into the recesses 11 to 17.
[0087] Pursuant to another embodiment, the wafers 2 are placed upon
support pins 38, as shown in FIG. 6a). The support pins 38 are
guided through bores 39 that are provided in the base of each
recess 32. Similarly, the covers 33 can be disposed on support pins
40. The support pins 40 are either guided through the bores 41, as
illustrated in FIG. 6a) and that extend through the carrier 10
beyond the recesses 32, or the support pins 42 extend entirely
externally of the carrier 10. The support pins 38 advantageously
have different heights for different recesses in order not to
hinder a loading of the recesses that are remote from the gripper
by the support pins that are provided for loading the recesses that
face the gripper. For the same reasons, the support pins 40 for the
covers 33 can have different lengths. The support pins 40 are
preferably all higher than are the support pins 38.
[0088] Pursuant to another embodiment, the carrier 10 is rotated
about a vertical axis for the loading. In this way, the recess 32
that is to be loaded at any given time can always face the
gripper.
[0089] As soon as the wafers 2 are placed upon the support pins 38,
and the covers 33 are placed upon the support pins 40, these pins
are moved downwardly through the carrier 10, as a result of which
the wafers 10 are raised from the support pins 38, and the covers
33 are raised from the support pins 40. The wafers 2 are thereby
placed into the recesses associated with them. Alternatively, the
carrier 10 can also be moved upwardly.
[0090] The loading of the wafer 10 can be effected not only within
the process chamber 4, but also externally of the process chamber
4.
[0091] The transport arm 41, which is illustrated in FIGS. 7 and 8,
of the inventive handling apparatus, as is used, for example, in
conjunction with the handling of wafers and receptacles during
thermal treatment processes, typically has a width b of
approximately 35 mm, which is less than the diameter of an object,
for example a wafer 42 or a receptacle, that is illustrated in
dashed lines. In this way, the wafer, which is stacked and
accommodated in cassettes such that it is spaced from adjacent
wafers, can be removed from the cassettes and after the processing
can again be placed therein. The thickness d (see FIG. 8) of the
transport arm 41 is in the range of 1 to 5 mm, and is typically 2
mm. The thickness is such that the transport arm 41 fits between
two adjacent wafers that are disposed in the cassettes, and can
hence remove a wafer 42 from the cassette. The length of the
transport arm 41 is selected in conformity with the requirements,
and the same is true with the cross-sectional and thickness
profile. The typical length of a transport arm 41 in the
aforementioned embodiment is between 20 and 70 cm.
[0092] Pursuant to the embodiment illustrated in FIGS. 7 and 8, the
wafer is supported by three support devices 43-1, 43-2, 43-3, which
are also known as pads, and which in the illustrated embodiment are
also provided for the support of a (not-illustrated) receptacle.
Alternatively, it is also possible to provide different support
devices or pads for the wafers on the one hand and the receptacle
on the other hand.
[0093] Provided in the transport arm 41 are vacuum or underpressure
lines 44 that connect the pads 43-1, 43-2, 43-3 with a vacuum or
underpressure source 45 via a connecting line 46. Provided in one
vacuum line 44 to one of the pads 43-2 is a vacuum control element
47, for example a controllable valve.
[0094] The transport arm 41 is connected via a securement element
48 with non-illustrated components and movement elements of the
handling device. Similarly extending in the securement element 48
are vacuum lines or channels 49, those ends of which face away from
the transport arm being connected to the connecting line 46.
[0095] As already described previously in detail, the pads 43-1,
43-2, and 43-3 can have shapes, masses and designs that are adapted
in conformity to the conditions in order to reliably support the
wafer as well as the receptacle that is to be handled.
[0096] Pursuant to a further embodiment of the invention, the
vacuum control element 47 is adapted to apply a vacuum to one of
the pads that differs from that applied to the remaining pads, if
this is necessary.
[0097] In addition, individual vacuum control elements can be
respectively provided for each of the pads. A vacuum control device
51 can be provided in the connecting line 46, for example between
the transport arm 41 and the underpressure or vacuum source 45. One
embodiment for this is schematically illustrated in FIG. 9. In the
connecting line 46, between the vacuum source 45 and the vacuum
lines 44 of the transport arm 41, two parallel vacuum lines 52 and
53 are provided in the vacuum control device 51 and can be
selectively switched into the vacuum line 46 via a first and a
second change-over switch 54, 55. The first vacuum line 52 serves
for conveying the vacuum made available from the vacuum source 45
without change to the vacuum lines 44 of the transport arm 41. In
contrast, provided in the second vacuum line 53 of the vacuum
control device 51 is a vacuum regulator 56 that alters the vacuum
in the second connecting line 53.
[0098] In the illustrated embodiment the switching of the
change-over switches 54 and 55 is effected via a computer that is
controlled by instruction software and is schematically provided
with the reference numeral 57 and makes available to an interface
58 of the vacuum control device 51 the appropriate program
instructions, which then pass in the form of control signals to the
change-over switches 54 and 55 via electrical lines 59 and 60.
[0099] Instead of controlling the change-over switches 54 and 55 by
means of a program, it is also possible to control the switching of
the output signal of the weight sensor that detects the weight of
the object that is to be handled.
[0100] With an object 42 that is to be handled that has a
relatively high weight, a relatively high vacuum, i.e. a relatively
small absolute pressure, is applied to the support devices 43-1,
43-2, 43-3 in that the first vacuum line 52, which does not have a
vacuum regulator, is connected with the vacuum source 45 via the
switch position of the change-over switches 54 and 55 illustrated
in FIG. 9. In the case of the temperature treatment of wafers, this
object--as previously described in detail--is a receptacle in which
at least one wafer is contained, and which, for example, is made of
graphite, silicon carbide or aluminum nitride.
[0101] Such a receptacle of graphite can, pursuant to further
embodiments, also be coated with the materials silicon carbide or
aluminum nitride. Due to the relatively high vacuum, the receptacle
is securely and reliably pressed against and held on the support
device via the pads 43-1, 43-2, 43-3 during the handling and
transport process.
[0102] If, however, with the same handling apparatus an object
having a lesser weight, for example a semiconductor wafer having a
weight of 0.1 to 20 g, is to be transported or handled, the
change-over switches 54 and 55 are switched over into the position
in which the pads 43-1, 43-2, and 43-3 communicate with the
pressure source 45 via the second connecting line 53. In this
second connecting line 53, the vacuum is reduced by the vacuum
regulator 56, in other words the absolute pressure is increased, so
that the application pressure is less for the wafer than for the
receptacle. This vacuum is thus adapted to the wafer and is so low
that the danger of breakage due to too great of a vacuum at the
pads is prevented.
[0103] In FIGS. 10a and 10b an embodiment is illustrated for a
transport arm 41 that has a respective support apparatus on both
sides that can differ from one another, for example, with regard to
the number of pads 61-1, 61-2, 61-3, 62, the structure thereof, the
form thereof and/or the dimensions thereof. Whereas in FIG. 10a a
pad structure is illustrated that essentially corresponds to the
embodiment of FIG. 7, and is provided for supporting objects having
little weight, for example wafers, the other side of the transport
arm 41 has a pad structure that, for example, has only one
relatively large surfaced, round pad that is connected to only one
vacuum line and is provided, for example, for an object having a
high weight, for example for a wafer receptacle or a graphite
box.
[0104] As indicated by the arrow of rotation 63, with this
embodiment the transport arm 41 can be rotated about its axis 64 by
180.degree., so that depending upon whether the object with great
weight or the object with lesser weight is to be supported and
handled, one of the two side of the transport arm 41 can be
selectively used.
[0105] If the handling apparatus is used in the semiconductor
industry, the material thereof, and in particular the material of
the transport arm 41, should be suitable for this application, and
preferably comprises sapphire, ceramic and/or quartz, of a
combination of these materials. These materials furthermore have
the advantage that the loading and unloading of a process chamber
can be effected at temperatures of up to 700.degree. C. Due to the
high modulus of elasticity, sapphire and ceramic also have the
further advantage of a high rigidity, i.e. the transport arm 41,
even if a receptacle having a weight of 200 g is placed thereupon,
bends or bows only slightly, if at all. The surface of the
transport arm 41 should be as smooth as possible. This, and as
unitary a design of the transport arm 41 as possible, facilitates
the cleaning and reduces a possible transport of particles into the
process chamber.
[0106] Although the invention was described with the aid of
preferred embodiments, it is not limited to the concrete
embodiments. For example, the carrier 10 can have an angled shape.
Similarly, the recesses can have an angular shape. In addition, the
number of recesses is not limited to seven. Also with carriers
having round recesses the diameter of the recesses can differ from
52 mm in order to also be able to accommodate wafers of 100 mm or
150 mm. A carrier can, for example, also have recesses having
different dimensions. Furthermore, individual features of the above
described embodiments can be combined or exchanged with one another
in any compatible manner.
[0107] The inventive handling apparatus is also not limited to the
features and design of the described embodiments. For example it is
also possible to support the objects, for example, the wafers or
receptacles, on the support devices in such a way that the suction
is effected via the Bernoulli effect, in other words, in that
vacuum is supplied to the holding devices or pads, so that a
Bernoulli effect results. In this case, acceleration forces in the
horizontal direction must be provided via additional auxiliary
means, which, for example, can be edge boundaries via which the
objects can be fixed in position relative to the transport arm
41.
* * * * *