U.S. patent application number 12/192857 was filed with the patent office on 2009-02-05 for zone control heater plate for track lithography systems.
This patent application is currently assigned to SOKUDO CO., LTD.. Invention is credited to David H. Quach, Martin Jeff Salinas.
Application Number | 20090032522 12/192857 |
Document ID | / |
Family ID | 38895379 |
Filed Date | 2009-02-05 |
United States Patent
Application |
20090032522 |
Kind Code |
A1 |
Salinas; Martin Jeff ; et
al. |
February 5, 2009 |
ZONE CONTROL HEATER PLATE FOR TRACK LITHOGRAPHY SYSTEMS
Abstract
A substrate heater comprising a bake plate having an upper
surface, a lower surface and a peripheral side surface extending
between the upper and lower surfaces, the bake plate including at
least one heating element, at least one temperature sensor and a
plurality of wires including at least one wire coupled to the
heating element and at least one wire coupled to the temperature
sensor; a shield spaced apart from and generally surrounding the
lower and peripheral side surfaces of the bake plate, the shield
having an interior upper surface facing the lower surface of the
bake plate, an interior side surface facing the peripheral side
surface of the bake plate and a lower surface opposite the interior
upper surface; a patterned signal layer formed on the lower surface
of the shield, wherein the plurality of wires are electrically
coupled to a corresponding plurality of signal traces formed in the
patterned signal layer; and a connector, electrically coupled to
the plurality of signal traces in the patterned signal layer,
adapted to facilitate electrical connections to the plurality of
wires.
Inventors: |
Salinas; Martin Jeff; (San
Jose, CA) ; Quach; David H.; (San Jose, CA) |
Correspondence
Address: |
TOWNSEND AND TOWNSEND AND CREW, LLP
TWO EMBARCADERO CENTER, EIGHTH FLOOR
SAN FRANCISCO
CA
94111-3834
US
|
Assignee: |
SOKUDO CO., LTD.
Kyoto
JP
|
Family ID: |
38895379 |
Appl. No.: |
12/192857 |
Filed: |
August 15, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11483832 |
Jul 7, 2006 |
7427728 |
|
|
12192857 |
|
|
|
|
Current U.S.
Class: |
219/446.1 |
Current CPC
Class: |
H01L 21/67103 20130101;
H01L 21/67248 20130101; H05B 3/143 20130101 |
Class at
Publication: |
219/446.1 |
International
Class: |
H05B 3/68 20060101
H05B003/68 |
Claims
1. A substrate heater comprising: a bake plate having an upper
surface, a lower surface, and a peripheral side surface extending
between the upper and lower surfaces, the bake plate including at
least one heating element, at least one temperature sensor and a
plurality of wires including at least one wire coupled to the
heating element and at least one wire coupled to the temperature
sensor; a patterned signal layer formed on the lower surface of the
bake plate, wherein the plurality of wires are electrically coupled
to a corresponding plurality of signal traces formed in the
patterned signal layer; and a connector, electrically coupled to
the plurality of signal traces in the patterned signal layer,
adapted to facilitate electrical connections to the plurality of
wires.
2. The substrate heater set forth in claim 1 wherein the patterned
signal layer is sandwiched between first and second insulation
layers also formed on the lower surface of the bake plate.
3. The substrate heater set forth in claim 1 further comprising a
plurality of support posts that extend from the lower surface of
the bake plate.
4. The substrate heater set forth in claim 3 wherein the plurality
of support posts extend from a central portion of the bake
plate.
5. The substrate heater set forth in claim 1 further comprising a
ribbon cable electrically coupled between the plurality of signal
trances and the connector.
6. The substrate heater set forth in claim 1 wherein the patterned
signal layer comprises a first conductive layer and an overlying
second conductive layer separated by an insulation layer.
7. The substrate heater set forth in claim 6 wherein the first
conductive layer is electrically coupled to one or more wires
coupled to the heating element and the second conductive layer is
electrically coupled to one or more wires coupled to the
temperature sensor.
8. The substrate heater set forth in claim 1 wherein the bake plate
further includes a plurality of layers, the plurality of layers
including a conductive layer disposed over a layer having the at
least one heating element.
9. The substrate heater set forth in claim 8 wherein the layer
having the at least one heating element is sandwiched between first
and second insulation layers.
10. The substrate heater set forth in claim 1 further comprising a
shield spaced apart from and generally surrounding the lower and
peripheral side surfaces of the bake plate, the shield having an
interior upper surface facing the lower surface of the bake plate,
an interior side surface facing the peripheral side surface of the
bake plate, and a lower surface opposite the interior upper
surface.
11. A substrate heater comprising: a bake plate having an upper
surface, a lower surface, and a peripheral side surface extending
between the upper and lower surfaces, the bake plate including a
plurality of independently controllable heating zones, each of the
plurality of independently controllable heating zones including a
heating element, a temperature sensor, and a plurality of wires
including at least one wire coupled to the heating element and at
least one wire coupled to the temperature sensor; a patterned
signal layer formed on the lower surface of the bake plate, wherein
the plurality of wires included in each of the plurality of
independently controllable heating zones are electrically coupled
to a corresponding plurality of signal traces formed in the
patterned signal layer; and a connector electrically coupled to the
plurality of signal traces in the patterned signal layer and
adapted to facilitate electrical connections to the plurality of
wires.
12. The substrate heater set forth in claim 11 wherein the
patterned signal layer is sandwiched between first and second
insulation layers also formed on the lower surface of the bake
plate.
13. The substrate heater set forth in claim 11 further comprising a
plurality of support posts that extend from the lower surface of
the bake plate.
14. The substrate heater set forth in claim 13 wherein the
plurality of support posts extend from a centered, inner-most
heating zone of the plurality of independently controllable heating
zones.
15. The substrate heater set forth in claim 11 further comprising a
ribbon cable electrically coupled between the plurality of signal
traces and the connector.
16. The substrate heater set forth in claim 11 wherein the
patterned signal layer comprises a first conductive layer and an
overlying second conductive layer separated by an insulation
layer.
17. The substrate heater set forth in claim 16 wherein the first
conductive layer is electrically coupled to one or more wires
coupled to the heating elements and the second conductive layer is
electrically coupled to one or more wires coupled to the
temperature sensor.
18. The substrate heater set forth in claim 11 wherein the bake
plate further includes a plurality of layers including a conductive
layer disposed over a layer including the heating elements.
19. The substrate heater set forth in claim 18 wherein the bake
plate further includes a first insulation layer and a second
insulation layer, the layer having the heating elements being
sandwiched between the first insulation layer and the second
insulation layer.
20. The substrate heater set forth in claim 11 further comprising a
shield spaced apart from and generally surrounding the lower and
peripheral side surfaces of the bake plate, the shield having an
interior upper surface facing the lower surface of the bake plate,
an interior side surface facing the peripheral side surface of the
bake plate, and a lower surface opposite the interior upper
surface.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] The present application is a division of U.S. patent
application Ser. No. 11/483,832, filed on Jul. 7, 2006, entitled
"Zone Control Heater Plate for Track Lithography Systems," the
disclosure of which is hereby incorporated by reference in its
entirety for all purposes.
BACKGROUND OF THE INVENTION
[0002] The present invention relates generally to the field of
substrate processing equipment. More particularly, the present
invention relates to a method and apparatus for controlling the
temperature of substrates, such as semiconductor substrates, used
in the formation of integrated circuits.
[0003] Modern integrated circuits (ICs) contain millions of
individual elements that are formed by patterning the materials,
such as silicon, metal and/or dielectric layers, that make up the
integrated circuit to sizes that are small fractions of a
micrometer. A number of steps associated with the fabrication of
integrated circuits include heating the semiconductor substrate
upon which the ICs are formed. One example of a heating step
includes curing a photoresist film prior to a photolithography
process. A photoresist film can be cured, for example, by placing a
semiconductor substrate having an uncured photoresist film formed
thereon on a bake plate and heating the plate to a sufficiently
high temperature for a predetermined period of time.
[0004] Over the years there has been a strong push within the
semiconductor industry to shrink the size of semiconductor devices.
The reduced feature sizes have caused the industry's tolerance to
process variability to shrink, which in turn, has resulted in
semiconductor manufacturing specifications having more stringent
requirements for process uniformity and repeatability. One
manifestation of these more stringent requirements is the
desirability to precisely control the temperature of a
semiconductor substrate in a bake plate heating operation such as
the photoresist curing operation just described.
[0005] To this end, the industry has developed heater plates that
include multiple heater elements arranged in different zones. Such
an arrangement allowed one zone of the heater plate to be heated at
a slightly higher temperature than other zones to compensate for
temperature nonuniformities that may occur between different points
on the semiconductor substrate. FIG. 1 is a top plan view of an
example of a previously known bake plate that includes six
different electrically independently heating zones. As shown in
FIG. 1, bake plate 10 includes six independent heater zones
12.sub.1-12.sub.6 along with a corresponding number of temperature
sensors 14.sub.1-14.sub.6, one for each of the heater zones
12.sub.1-12.sub.6.
[0006] Depending on the type of temperature sensor used, each
sensor and independent heater zone requires at least three separate
wires and often five or more separate wires (e.g., a five wire
arrangement may use two wires for AC power connections to the
heater element and three wires for connections to the sensor).
Between the multiple zones used in many zone heater bake plates and
the fact that each zone often includes its own temperature sensor
having multiple dedicated wires, it can be appreciated that a zone
heater may readily have twenty, thirty or even more wires extending
from it. Effectively and efficiently managing such a large number
of wires presents challenges.
SUMMARY OF THE INVENTION
[0007] According to the present invention, methods and apparatus
related to substrate processing are provided. More particularly,
embodiments of the present invention pertain to a method and
apparatus for heating a substrate in a highly controllable manner
and provide an effective and efficient solution for managing the
large number of wires that may be required to effect such highly
controlled heating. While embodiments of the invention may prove to
be particularly useful in heating station of a track lithography
tool, other embodiments of the invention can be used in other
applications where it is desirable to heat substrates in a highly
controllable manner.
[0008] According to one embodiment a substrate heater comprising a
bake plate, a shield, a patterned signal layer formed on a lower
surface of the shield and a connector, electrically coupled to the
plurality of signal traces in the patterned signal layer, adapted
to facilitate electrical connections to the plurality of wires is
disclosed. The bake plate has an upper surface, a lower surface and
a peripheral side surface extending between the upper and lower
surfaces and includes at least one heating element and at least one
temperature sensor. A plurality of wires including at least one
wire coupled to the heating element and at least one wire coupled
to the temperature sensor are attached to the bake plate and
electrically coupled to a corresponding plurality of signal traces
formed in the patterned signal layer. The shield is spaced apart
from and generally surrounds the lower and peripheral side surfaces
of the bake plate. The shield has an interior upper surface facing
the lower surface of the bake plate, an interior side surface
facing the peripheral side surface of the bake plate and a lower
surface opposite the interior upper surface.
[0009] In another embodiment a substrate heater comprises a bake
plate having an upper surface, a lower surface and a peripheral
side surface extending between the upper and lower surfaces, the
bake plate including at least one heating element, at least one
temperature sensor and a plurality of wires including at least one
wire coupled to the heating element and at least one wire coupled
to the temperature sensor; a patterned signal layer formed on the
lower surface of the bake plate, wherein the plurality of wires are
electrically coupled to a corresponding plurality of signal traces
formed in the patterned signal layer; and a connector, electrically
coupled to the plurality of signal traces in the patterned signal
layer, adapted to facilitate electrical connections to the
plurality of wires.
[0010] In still another embodiment a substrate heater comprises a
bake plate having an upper surface, a lower surface and a
peripheral side surface extending between the upper and lower
surfaces, the bake plate including a plurality of independently
controllable heating zones, each zone including a heating element,
a temperature sensor and a plurality of wires including at least
one wire coupled to the heating element and at least one wire
coupled to the temperature sensor; a shield spaced apart from and
generally surrounding the lower and peripheral side surfaces of the
bake plate, the shield having an interior upper surface facing the
lower surface of the bake plate, an interior side surface facing
the peripheral side surface of the bake plate and a lower surface
opposite the interior upper surface; a patterned signal layer
formed on the lower of the shield, wherein the plurality of wires
associated with each independently controllable heating zone are
electrically coupled to a corresponding plurality of signal traces
formed in the patterned signal layer; and a connector, electrically
coupled to the plurality of signal traces in the patterned signal
layer, adapted to facilitate electrical connections to the
plurality of wires.
[0011] Various benefits and advantages that can be achieved by use
of the present invention will be described in detail throughout the
present specification and more particularly below in conjunction
with the following drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a simplified representative view of a previously
known zone heater bake plate;
[0013] FIG. 2 is a simplified cross-section of a substrate heater
according to an embodiment of the present invention;
[0014] FIG. 3 is an expanded view of portion A of substrate heater
20 shown in FIG. 2 according to an embodiment of the present
invention;
[0015] FIG. 4 is a bottom cross-sectional perspective view of
substrate heater 20 shown in FIG. 2 according to an embodiment of
the present invention; and
[0016] FIG. 5 is a simplified cross-sectional view of a portion of
a bake plate 22 including a proximity pin 25 that can be used to
space a wafer above the surface of the bake plate according to some
embodiments of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The present invention generally provides a method and
apparatus for heating substrates in a highly controllable manner.
While it is to be recognized that embodiments of the invention are
particularly useful for heating substrates according a particular
thermal recipe within a track lithography tool, other embodiments
of the invention can be used in other applications where it is
desirable to heat substrates in a highly controllable manner. Note
the terms "substrate" and "wafer" are sometimes used herein
interchangeably and are sometimes specifically used in reference to
a semiconductor wafer upon which integrated circuits are formed. A
person of skill in the art will recognize the present invention is
not limited to processing semiconductor wafers and can be used to
process any substrate for which a highly controlled thermal
treatment is desirable.
[0018] Reference is now made to FIG. 2, which is a simplified
cross-sectional view of a substrate heater 20 according to an
embodiment of the present invention. Substrate heater plate 20
includes a bake plate 22 and a heat shield 24. Bake plate 22
includes an upper substrate receiving surface 22a upon which a
substrate is placed during a heat treatment step and a lower
surface 22b. Bake plate 22 can be, for example, an aluminum plate
having a continuous upper surface with restive heater elements
bonded to its backside.
[0019] In some embodiments, a plurality of proximity pins
distributed across upper substrate receiving surface 22a can be
used to support a substrate in close proximity to upper surface 22a
during heat treatment. An example of a proximity pin 25 is shown in
FIG. 5. As shown in FIG. 5, proximity pin 25 may be, for example, a
sapphire ball placed in a trench 27 formed on upper surface 22a of
bake plate 22. When a wafer 15 is placed over the bake plate onto
proximity pin 25, pin 25 spaces the wafer a predetermined distance
(e.g., 100 .mu.m) above surface 22a. Details of proximity pins
appropriate for this purpose are set forth in U.S. application Ser.
No. 11/111,155, entitled "Purged Vacuum Chuck with Proximity Pins"
filed on Apr. 20, 2005 (Attorney Docket No.: A9871/T60200), which
is hereby incorporated by reference for all purposes.
[0020] Referring back to FIG. 2, lower surface 22b is spaced apart
from an upper surface 24a of the heat shield by a predetermined
distance, d. In one embodiment distance d is, for example, between
2 to 10 mm. A side peripheral surface 22c extends between upper
surface 22a and lower surface 22b. Several support pins 26 (two of
which are shown in FIG. 2) protrude from lower surface 22b
extending through heat shield 24 to support both bake plate 22 and
heat shield 24. Because the contact area between support pins 26
and bake plate 22 is minimized, thermal loss to the support pins is
also minimized. In embodiments where substrate heater 20 is
moveable along a z-axis, support pins 26 are operatively coupled to
an appropriate lift or motor. In other embodiments, support pins 26
may be coupled to a support base or similar element. In one
particular embodiment, three symmetrically placed support pins 26
are used to support bake plate 22, and the three pins all extend
from a centered, inner-most heating zone, such as zone 12 shown in
FIG. 1. In such an arrangement, the inner-most zone can be
controlled to heat the bake plate at a slightly elevated
temperature to compensate for heat loss through the support
pins.
[0021] Two temperature sensors 28.sub.1 and 28.sub.2 (e.g.,
resistance temperature detectors-"RTDs") that are operatively
coupled to measure temperature within two independently
controllable heating zones 30.sub.1 and 30.sub.2, respectively, are
shown in FIG. 2. Each temperature sensor 28.sub.1 and 28.sub.2 is
electrically coupled to a respective wire bundle 29.sub.1 and
29.sub.2, each of which typically includes between 3-8 separate
wires. Wire bundles 29.sub.1 and 29.sub.2 extend through a
pass-through opening in heat shield 24 and are coupled to a signal
layer formed on a lower surface of the heat shield as described
more fully with respect to FIG. 3.
[0022] Bake plate 22 may be, for example, a high performance,
multi-zone bake plate that can be used for post-exposure bake of
photoresist material in a track lithography tool. Thus, bake plate
22 may provide tight control over both spatial and temporal wafer
temperature profile as well as the flexibility to induce a
deliberate temperature non-uniformity in one area or zone of the
bake plate to compensate for variations in wafer temperature, such
as those due to wafer warp or other process variations in the wafer
flow. Towards this end, it is to be understood that other
independently controllable heating zones 30.sub.1 not shown in FIG.
2 may exist along with other temperature sensors 28.sub.1 and wire
bundles 29.sub.1. Also, in one embodiment there is at least one
proximity pin within each of the independently controlled heater
zones 30.sub.1.
[0023] Referring now to FIG. 3, which is an enlarged view of
portion A shown in FIG. 2, including bake plate 22 and heat shield
24. Heat shield 24 includes a cup-shaped shield 32, which may be
made, for example, from stainless steel or any other appropriate
material. Shield 32 is spaced apart from and generally surrounds
lower surface 22b and side surface 22c of bake plate 22. Shield 32
includes an interior upper surface 24a spaced apart from bake plate
lower surface 22b and an interior side surface 24c spaced apart
from bake plate side surface 22c. A patterned wiring layer 36 is
formed on the lower surface of shield 32. Wiring layer 36 is
sandwiched between an upper insulating layer 34 and a lower
insulating layer 38. In one embodiment, each insulating layer 34,
38 is a kapton layer and patterned wiring layer 36 includes a
plurality of patterned metal traces formed on one of the kapton
layers as is understood by a person of ordinary skill in the art.
In an alternative embodiment, wiring layers 36 may be a multilayer
structure having two or more signal layers separated by an
insulating layer. For example, in one embodiment a first layer may
be used for AC signals, a second wiring layer for RTD signals, and
a third grounding layer with each of the layers being separated by
a kapton or other insulting layer appropriate for use in the PCB
industry and high temperature applications.
[0024] The individual wires in each wire bundle 29.sub.1 are
coupled to wiring layer 36. For example, as shown in FIG. 3, bundle
of wires 29.sub.1 includes two wires 51, 52 that connect heater
element 30.sub.1 to an AC power supply and three wires 53, 54, 55
that connect temperature sensor 28.sub.1 to an appropriate
controller, e.g., a signal processor, that monitors the detected
temperature and varies the frequency (duty cycle) at which power is
supplied to heater element 30.sub.1 as appropriate. Each of wires
51-55 passes through a pass-through hole in shield 24 and is
coupled to an appropriate signal trace in wiring layer 36. Using,
for example, a high temperature solder connection or other
appropriate process. In the embodiment shown in FIG. 3, wires 51,
52 extend through through-hole 60 while wires 53, 54, 55 extend
through through-hole 62.
[0025] While not shown in FIG. 3, the signal traces within wiring
layer 36 that wires 51-55 are coupled to are electrically isolated
from each other. The patterned metal traces in wiring layer 36
route the signals for each of the various wires in wire bundles
29.sub.1, 29.sub.2 and 29.sub.i to a common area (shown in FIG. 4)
where they are electrically coupled, for example by a ribbon cable
70, to an appropriate multi-pin connector 72 as shown in FIG. 4,
which is a simplified bottom cross-sectional perspective view of
one embodiment of substrate heater 20 according to the present
invention. As shown in FIG. 4, wires for AC power (e.g., wires 56,
57) may be thicker than wires for 52, 53, 54 that couple one of the
temperature sensors to signal layer 36. In one embodiment, the AC
power wires are 26 gauge wires while the sensor signal wires are 30
gauge.
[0026] As shown in FIG. 3, bake plate 22 typically includes
multiple layers. For example, in one embodiment bake plate 22
includes a continuous upper aluminum plate 40 over a layer 42 of
resistive heating elements. Layer 42 includes separate heating
elements for each individual heating zone 30.sub.1 which are
sandwiched between insulation layers 44 and 46. Insulation layers
44, 46 can be formed from kapton or other suitable materials. In
one particular embodiment plate 40 consists of an aluminum 6061-T6
plate which acts as a low thermal mass for compensating for
temperature variations and each heating zone 30.sub.1 includes a
resistive heater laminated and bonded to the aluminum plate using
an all polyimide construction that allows operation up to
250.degree. C.
[0027] In some embodiments patterned signal layer 36 (along with
appropriate insulating layers 34, 38) can be formed on lower
surface 22b of bake plate 22 instead of on the lower surface of the
heat shield as shown in FIGS. 3 and 4. In such embodiments, heat
shield 24 is optional. When a sufficiently large number of metal
traces are formed on the bottom of bake plate 22, however, routing
the metal traces to a concentrated area on the bottom of the bake
plate for connection to a ribbon cable or similar mechanism may
result in small differences in the thermal characteristics of the
region of the bake plate above the concentrated metal traces as
compared to regions of the bake plate outside of this region. That
is, having a relatively high concentration of metal (even thin
metal traces) formed on one portion of the bake plate may result in
small differences in the thermal characteristics of that region of
the bake plate as compared to other regions that do not have such a
high concentration of metal formed on the lower surface. These
small differences may in turn adversely impact the temperature
uniformity of the bake plate. The inventors have found that forming
patterned signal layer 36 on the bottom of the heat shield, which
is separated from bake plate 22 by an air gap, as shown in FIGS. 3
and 4 eliminates thermal cross-talk between the metal traces in
signal layer 36 and the bake plate. Thus, embodiments of the
invention similar to that shown in FIGS. 3 and 4 which minimize or
eliminate such non-uniformities by thermally isolating signal layer
36 from bake plate 22 are sometimes preferred.
[0028] While the present invention has been described with respect
to particular embodiments and specific examples thereof, it should
be understood that other embodiments may fall within the spirit and
scope of the invention. For example, while one embodiment of the
bake plate described above included six independently controllable
heating zones, the present invention is applicable to bake plates
having more than six heating zones and less than six heating zones.
The scope of the invention should, therefore, be determined with
reference to the appended claims along with their full scope of
equivalents.
* * * * *