U.S. patent application number 11/524390 was filed with the patent office on 2007-03-08 for semiconductor processing temperature control.
Invention is credited to Boris Atlas.
Application Number | 20070051818 11/524390 |
Document ID | / |
Family ID | 28039218 |
Filed Date | 2007-03-08 |
United States Patent
Application |
20070051818 |
Kind Code |
A1 |
Atlas; Boris |
March 8, 2007 |
Semiconductor processing temperature control
Abstract
A temperature control system having a re-circulation loop that
uses valves to selectively circulate a temperature control fluid
through a cooling system, through a heating system, or through a
through passage so as to controlling the temperature of the
temperature control fluid, which, in turn, controls the temperature
of a target. A temperature sensor monitors the target's
temperature. A controller controls valve operation in response to
the temperature measured by the temperature sensor to obtain a
predetermined target temperature. Beneficially, the controller
controls the target's temperature according to a predetermined
temperature profile. Continuous etching along a predetermined
temperature profile is possible.
Inventors: |
Atlas; Boris; (San Jose,
CA) |
Correspondence
Address: |
MCKENNA LONG & ALDRIDGE LLP
1900 K STREET, NW
WASHINGTON
DC
20006
US
|
Family ID: |
28039218 |
Appl. No.: |
11/524390 |
Filed: |
September 21, 2006 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10983248 |
Nov 8, 2004 |
|
|
|
11524390 |
Sep 21, 2006 |
|
|
|
10097603 |
Mar 15, 2002 |
6822202 |
|
|
10983248 |
Nov 8, 2004 |
|
|
|
Current U.S.
Class: |
236/1C ; 219/494;
257/E21.579; 438/714; 62/160 |
Current CPC
Class: |
H01L 21/31111 20130101;
H01L 21/76808 20130101; H01L 21/31133 20130101; H01L 21/67248
20130101; G05D 23/20 20130101 |
Class at
Publication: |
236/001.00C ;
219/494; 438/714; 062/160 |
International
Class: |
G05D 23/12 20060101
G05D023/12; F25B 13/00 20060101 F25B013/00; H05B 1/02 20060101
H05B001/02; H01L 21/302 20060101 H01L021/302; F24F 11/053 20060101
F24F011/053 |
Claims
1-22. (canceled)
23. A method of forming a contact comprising: providing a silicon
layer with a copper plug embedded therein; providing a metal
hardmask over the copper plug; depositing a resist layer over the
metal hardmask; a first etch step for etching a first opening in
the resist layer at a first temperature; and a second etch step for
etching the metal hardmask at a second temperature wherein the same
etchant is used for the first etch step and the second etch
step.
24. A method of forming a contact according to claim 23, wherein
the first temperature and the second temperature are different.
25. A method of forming a contact according to claim 23, wherein
the first and second etch steps are continuously performed in one
vessel.
26. A method of forming a contact according to claim 23, further
comprising completely removing the resist layer during the second
etch step.
27. A method of forming a contact according to claim 23, further
comprising sequentially providing a first nitride layer, a first
polyimide layer, a second nitride layer, a second polyimide layer,
before providing said metal hardmask.
28. A method of forming a contact according to claim 27, further
comprising sequentially and continuously etching the second
polyimide layer, the second nitride layer, the first polyimide
layer and the first nitride layer to form an opening to expose said
copper plug.
29. A method of forming a contact according to claim 27, wherein
the first polyimide layer and the second polyimide layer are etched
at said first temperature.
30. A method of forming a contact according to claim 28, wherein
the first nitride layer and second nitride layer are etched at said
second temperature.
31. A method of forming a contact according to claim 29, wherein
the second polyimide layer, the second nitride layer, the first
polyimide layer and the first nitride layer are etched in the same
vessel and using the same etchant.
32. A method of forming a contact according to claim 30, further
comprising electroplating copper in said opening.
Description
BACKGROUND OF THE INVENTION
[0001] This application is a divisional of prior application Ser.
No. 10/983,248, filed Nov. 8, 2004, which is a continuation of
prior application Ser. No. 10/097,603, filed Mar. 15, 2002, now
U.S. Pat. No. 6,822,202.
FIELD OF THE INVENTION
[0002] The present invention relates to semiconductor processing
temperature control. More specifically, it relates to controlling
the temperature of a semiconductor processing device (target) using
a temperature control fluid that is selectively heated and cooled.
The temperature of the semiconductor processing device (target) is
variable over time according to a predetermined temperature
profile.
DISCUSSION OF THE RELATED ART
[0003] Semiconductor device manufacturing involves a large number
of processing steps, such as semiconductor crystal growth, wafer
cutting, wafer polishing, doping, material depositions, oxide
growths, masking, and etching. Because modem semiconductors must be
low cost and highly reliable, rapid fabrication with high device
yields and with tight tolerances is critical. That generally
requires automated equipment and processes in specially designed
clean rooms.
[0004] While clean rooms are generally successful, they are
expensive to build and operate, with the cost being highly
dependent on floor space. Thus, only the processing steps that must
be performed in a clean room are usually performed there.
Furthermore, it is beneficial to minimize the device processing and
wafer handling steps required to be performed in a clean room. Many
of the steps performed in clean rooms require heating and/or
cooling. For example, since etching is highly temperature
dependent, the etching temperature of each etching step (there
might be several) must be carefully controlled. Increasing etching
difficult is that as semiconductors get denser, the need for
accurate temperature control becomes greater. Thus, a semiconductor
wafer might be etched at a carefully controlled first temperature,
then etched at a carefully controlled second temperature, and then
etched at a carefully controlled third temperature, and so on.
[0005] In prior art semiconductor processing, multiple etchings
typically required the semiconductor wafers being processed to be
moved between different etching vessels that are maintained at
different temperatures. This increased the risk of wafer
contamination, necessitated multiple etching vessels and
temperature control systems, increased processing time, and
increased the required clean room floor space. An alternative was
to etch the semiconductor wafers in one vessel at one temperature,
remove the semiconductor wafers, change the vessel's temperature,
re-insert the semiconductor wafers, and then repeating the process
as required. Semiconductor wafer removal was required because it
was very difficult or impossible to rapidly change a vessel's
temperature, and because it was very difficult or impossible to
control the temperature's rate of change.
[0006] In clean rooms, temperature control is usually achieved by
pumping a temperature control fluid through a semiconductor
processing vessel, chamber, tool, device, or assembly, all of which
are generically referred to hereinafter as targets. The temperature
control fluid is usually heated or cooled using a heat exchanger,
with heat flow being dependent on temperature requirements.
Typically, electrically controlled valves are used to adjust the
control fluid's flow through a heat exchanger. Thus, prior art
semiconductor process temperature controls use various types of
pipes, pumps, thermostats, heat exchangers, temperature
controllers, refrigeration units, heaters, valves, and temperature
control fluids.
[0007] While beneficial, prior art semiconductor process
temperature controls usually either cooled or heated targets, but
not both. Systems that both heated and cooled usually used separate
temperature control fluids. That is, a fixed volume of temperature
control fluid was used for heating, while another fixed volume was
used for cooling. Such systems required multiple circulation pipes
through the targets, which increased cost and reduced
reliability.
[0008] However, U.S. Pat. No. 6,026,896 discloses a semiconductor
process temperature control system in which control valves switch
the temperature control fluid that passes through the target
(reference FIG. 3, valve 74, and the supporting text of U.S. Pat.
No. 6,026,896). U.S. Pat. No. 6,026,896 thus teaches selectively
controlling the temperature control fluid (heated or cooled) that
flows through the target. While the system disclosed in U.S. Pat.
No. 6,026,896 is beneficial, multiple pumps, numerous control
valves, and extensive piping are still required. Furthermore,
temperature adjustment and regulation requires rapid valve
switching and flushing of the temperature control fluid. This can
detrimentally impact reliability because of thermal stresses and
pressure mismatches between the heating and cooling subsystems.
Furthermore, mass mixing between the heated and cooled temperature
control fluids leads to increased power consumption because
previously heated temperature control fluid must be cooled, while
previously cooled temperature control fluid must be heated.
[0009] Therefore, a semiconductor temperature process control
system that can heat and cool using the same temperature control
fluid would be beneficial. Even more beneficial would be a
semiconductor temperature process control system that uses only one
volume of temperature control fluid and that requires only one
temperature control fluid pump. Still more beneficial would be a
semiconductor temperature process control system that uses only one
volume of temperature control fluid, that uses only one temperature
control fluid pump, and that has reduced thermal shock and reduced
valve switching. More beneficial yet would be an efficient
semiconductor temperature process control system that uses only one
volume of temperature control fluid, that uses only one temperature
control fluid pump, and that has low thermal shock and reduced
valve switching. Such a system having variable temperatures that
change according to well-defined temperature profiles
(well-controlled rates of temperature change) would be highly
beneficial in that such would enable continuous etching of a
semiconductor wafer at different temperatures that change according
to a predetermined temperature profile.
SUMMARY OF THE INVENTION
[0010] The following summary of the invention is provided to
facilitate an understanding of some of the innovative features
unique to the present invention, and is not intended to be a full
description. A full appreciation of the various aspects of the
invention can be gained by taking the entire specification, claims,
drawings, and abstract as a whole.
[0011] Accordingly, the principles of the present invention are
directed to a semiconductor process temperature control system that
heats and cools a target using one temperature control fluid.
Beneficially, the principles of the present invention are
implemented using a re-circulation loop that is pressurized by one
pump (or one pumping system). The principles of the present
invention can be implemented with low thermal shock and reduced
valve switching, and thus with improved reliability. Furthermore,
the principles of the present invention can be implemented with
relatively high efficiency.
[0012] A semiconductor process temperature control system according
to the principles of the present invention includes a
re-circulation loop for retaining and circulating a volume of
temperature control fluid such that the temperature control fluid
is in thermal communication with a target whose temperature is
being controlled. The temperature control fluid is circulated
through the re-circulation loop by a fluid pump. The re-circulation
loop includes control valves that selectively enable some of the
temperature control fluid to flow through a cooling heat exchanger,
through a heating heat exchanger, or through neither heat
exchanger. The control valves are controlled by a controller, which
receives temperature information that is related to the temperature
of the target from at least one temperature sensor. Based on the
temperature information, some of the temperature control fluid is
passed through a selected heat exchanger such that the target
achieves a predetermined temperature. Beneficially the controller
further receives time information from a timer. In such cases, the
controller controls the flow of the temperature control fluid such
that the temperature of the target follows a predetermined
temperature profile. This enables continuous etching of a
semiconductor wafer at different temperatures that change according
to a well-defined temperature profile.
[0013] Beneficially, the re-circulation loop retains a volume of
temperature control fluid such that the temperature control fluid
can change temperatures relatively rapidly. Furthermore, the
re-circulation loop beneficially passes only part of the
temperature control fluid through a heat exchanger. This reduces
thermal stress and stabilizes re-circulation loop pressures.
[0014] Furthermore, the temperature sensor is beneficially located
such that it accurately senses a temperature that is related to the
target. To that end, the temperature sensor beneficially senses the
target temperature, the temperature of an object in thermal
communication with the target, or the temperature of the
temperature control fluid as the temperature control fluid leaves
the target area.
[0015] A semiconductor process temperature control system according
to the principles of the present invention enables beneficial
semiconductor processing methods. For example, a method of
continuously etching a semiconductor wafer includes etching a
semiconductor wafer at a first temperature, adjusting the etch
temperature along a well-defined temperature profile to a second
temperature while continuing to etch, and subsequently etching the
semiconductor wafer at the second temperature. Beneficially,
etching is performed at the first temperature for a predetermined
time, and then at the second temperature for another predetermined
period of time. Furthermore, the etching temperature during the
temperature adjustment from the first temperature to the second
temperature beneficially occurs over a predetermined time.
[0016] A semiconductor process temperature control system according
to the principles of the present invention can include multiple
individual temperature control systems that share heating and/or
cooling resources. The temperature profiles of a plurality of
targets can be controlled. Of course, a plurality of temperature
sensors for sensing the temperatures of the individual targets, a
plurality of temperature control units for controlling the
temperatures of the individual targets, and a plurality of
re-circulation loops for isolating the temperature control fluids
for the individual targets are required. Such re-circulation loops
can include circulation pumps and control valves.
[0017] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are intended to provide further explanation of
the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and together with the description serve to explain
the principles of the invention.
[0019] In the drawings:
[0020] FIG. 1 is a schematic diagram of a temperature control
system that is in accord with the principles of the present
invention;
[0021] FIG. 2 illustrates a temperature profile of a target during
etching;
[0022] FIG. 3 is a schematic diagram of a temperature control
system that is in accord with the principles of the present
invention and that includes multiple temperature controlled
targets; and
[0023] FIGS. 4A-4F illustrate a fabrication process that benefits
from temperature control systems that are in accord with the
principles of the present invention.
[0024] FIG. 5 illustrates a fabrication process that benefits from
temperature control systems that are in accord with the principles
of the present invention.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT
[0025] Reference will now be made in detail to an illustrated
embodiment of the invention, the example of which is shown in the
accompanying drawings.
[0026] FIG. 1 illustrates a semiconductor process temperature
control system 10 that is in accord with the principles of the
present invention. The semiconductor process temperature control
system 10 both heats and cools a target 12, as required, using a
temperature control fluid in a re-circulation loop 14. The
re-circulation loop 14 includes a through passage 16, a cooling
passage 18, and a heating passage 20. The temperature control fluid
is pumped through the re-circulation loop 14 by a pump 22.
[0027] Still referring to FIG. 1, the through passage 16, the
cooling passage 18, and the heating passage 20 are in parallel.
They meet at a first branch 24 and at a second branch 26. The
through passage 16 transports some of the temperature control fluid
directly from the first branch 24 to the second branch 26. The
cooling passage 18 includes a cooling valve 28 and a cooling heat
exchanger 30 that is cooled by lines 31 that transport a
refrigerated cooling fluid. The cooling valve 28 is electrically
operated under the control of a controller 32. The heating passage
20 includes a heating valve 36 and a heating heat exchanger 38. The
heating heat exchanger receives power or heat on lines 39. For
example, the lines 39 might be electrical wires that supply power
to a resistive heat source in the heating heat exchanger 38, or the
lines 39 might transport a heated fluid through the heating heat
exchanger. The heating valve 36 is also electrically operated under
the control of the controller 32.
[0028] The controller 32 receives temperature information from at
least one temperature sensor 40. That temperature sensor is in
thermal communication with the target 12 such that target
temperature information is available to the controller 32. The
temperature sensor 40 could be in direct thermal contact with the
target 12, in thermal contact with a material in or on the target,
or in thermal contact with the temperature control fluid,
beneficially as the temperature control fluid leaves the target
area. More than one temperature sensor 40 can supply information to
the controller 32.
[0029] In operation, the controller 32 is programmed to set the
temperature of the target 12 at predetermined temperatures at
predetermined times, with the temperatures always being greater
than the lowest temperature achievable from the cooling heat
exchanger 30, but always less than the highest temperature
achievable from the heating heat exchanger 38. If the temperature
information from the temperature sensor 40 shows that the target
temperature is less than the programmed temperature at the
particular moment in time, the controller 32 opens the heating
valve 36. This enables some of the temperature control fluid to
flow through the heating heat exchanger 38, which heats the
temperature control fluid. That heated temperature control fluid
then mixes with the temperature control fluid that passes through
the through passage 16, thus causing the temperature of the
temperature control fluid to rise. This causes the target
temperature to rise. When the target temperature is correct, the
controller 32 closes the heating valve 36.
[0030] Alternatively, if the temperature information from the
temperature sensor 40 shows that the target temperature is greater
than the programmed temperature at the particular instant, the
controller opens the cooling valve 28. This enables some of the
temperature control fluid to flow through the cooling heat
exchanger 30, which cools the temperature control fluid. That
cooled temperature control fluid mixes with the temperature control
fluid that passes through the through passage 16, thus causing the
temperature of the temperature control fluid to drop. This causes
the target temperature to drop. When the target temperature is
correct, the controller 32 closes the cooling valve 28.
[0031] The controller 32 beneficially proportionally controls the
temperature. That is, if a desired temperature is far from the
measured temperature, the controller 32 causes significant heating
or cooling. Then, as the current temperature approaches the desired
temperature the rate of heating/cooling decreases.
[0032] Furthermore, the controller 32 beneficially can be
programmed such that the target temperature changes over time
according to a predetermined temperature profile. This is extremely
beneficial in some applications. For example, FIG. 2 illustrates a
desired temperature profile of a target in which (or by which) a
semiconductor wafer is being etched. Assume that the semiconductor
wafer is to be etched at different rates at different times using
the same etchant. Further assume, as is usually the case, that the
etch rate is temperature dependent. At time 0, the semiconductor
process temperature control system 10 sets the target 12 at a first
temperature, say 80.degree. C., which induces a desired first etch
rate. After a time T1, the etch rate ideally should be at a second
temperature, say 40.degree. C., which induces a second etch rate.
As an instantaneous temperature change is not possible, shortly
before time T1 (at say T1-) the controller 32 begins adjusting the
flow of the temperature control fluid in a controlled manner
through the cooling valve 28. This controlled adjustment enables a
repeatable temperature change profile. This enables the etch
process designer to implement a continuous etch system having known
etch characteristics along a temperature change. After some
temperature adjustment time, say at time T1+, the target
temperature is at the second temperature and etching continues at
the second etch rate.
[0033] Later, say at time T2, the etch rate should changes to a
third rate. Shortly before time T2 (at say T2-) the controller 32
begins adjusting the flow of the temperature control fluid in a
controlled manner through the cooling valve 28. This adjusts the
target temperature along a predetermined and repeatable temperature
profile curve to a third temperature, say 20.degree. C., which
induces a third etch rate. After some temperature adjustment time,
say at time T2+, the target temperature is at the third
temperature. Finally, at a later time, say at time T3, the etch
rate should change back to the first rate. Then, shortly before
time T3 (at say T3-) controller 32 begins adjusting the flow of the
temperature control fluid in a controlled manner through the
heating valve 36. This adjusts the target temperature along a
predetermined and repeatable temperature profile curve back to the
first temperature. After some temperature adjustment time, say at
time T3+, the target temperature is back at the first temperature.
To assist ease of operation, and to enable changes in the
temperature profiles, the controller 32 beneficially operates under
software control. An example of an etch process that benefits from
continuous etching along a controlled temperature profile is
provided subsequently.
[0034] Turning back to FIG. 1, the blending of heated/cooled
temperature control fluid with temperature control fluid that
passes through the through passage 16 enables both heating and
cooling with the same temperature control fluid. Furthermore, sharp
thermal shocks and pressure disturbances are avoided. Additionally,
the closed re-circulation loop 14 minimizes the volume of
temperature control fluid that must be heated and cooled to change
the temperature of the target 12. This enables relatively rapid
temperature changes, which can be important in applications like
that described above with reference to FIG. 2 (and subsequently
described with reference to FIGS. 4A-4F). Additionally, only one
pump (or pump system) is required for both heating and cooling.
Another benefit of the semiconductor process temperature control
system 10 is that rapid switching of the valves 28 and 36 are not
required to maintain a fixed temperature. That is, if both valves
are closed the only temperature control fluid that is circulated is
through the through passage 16. If that temperature control fluid
is at or near the desired fixed temperature, cycling between
heating and cooling is not required.
[0035] FIG. 3 illustrates a multiple target temperature control
system 100 that is in accord with the principles of the present
invention. The target temperature control system 100 is essential
comprised of paralleled temperature control systems 10. However,
the temperature control system 100 can control the temperatures of
multiple targets 12. Each target has its own re-circulation loop 14
with through passage 16, cooling passage 18, and heating passage
20. Furthermore, each target 12 has an associated volume of
temperature control fluid that is pumped through the target's
associated re-circulation loop 14 by a pump 22. Additionally, each
re-circulation loop 14 includes a first branch 24, a second branch
26, a cooling valve 28, a cooling heat exchanger 30 cooled by lines
31, and a heating valve 36. However, the temperature control system
100 beneficially includes a single heat exchanger 38 and a single
cooling source 50. As shown, each target 12 also has an associated
temperature sensor 40 that feeds temperature information to a
temperature control unit 32. There might be one temperature control
unit 32 or multiple temperature control units.
[0036] Still referring to FIG. 3, the cooling heat exchanger 50
cools a refrigerated cooling fluid in lines 31. The refrigerated
cooling fluid in lines 31 subsequently cool fluids in the
individual re-circulation loops 14 (a set for each target) via
cooling heat exchangers 30. Similarly, the heat exchanger 38 heats
the heating fluids in each of the individual re-circulation loops
14.
[0037] It is more economical to locate as much of each temperature
control unit as possible outside of the clean room. Thus, FIG. 3
shows much of the heating and cooling units being located in a
utility room 64, which is beneficially outside of clean rooms that
house the targets 12.
[0038] As previously noted, the temperature control units 10 and
100 are highly beneficial in that they enable continuous etching of
a target 12 as the target's temperature is adjusted in accord with
a predetermined temperature profile. This enables a new level of
semiconductor fabrication performance. For example, FIG. 4A through
4F illustrate a special contact formation process that benefits
from the principles of the present invention. The process begins
with a structure as shown in FIG. 4A. That structure includes a
copper plug 44 embedded in a silicon layer 42. Over the copper plug
44 and silicon layer 42 is a first nitride layer 46. Over the first
nitride layer 46 is a first polyimide layer 48, which is capped by
a second nitride layer 52. Over the second nitride layer 52 is a
second polyimide layer 54, which is capped by a metal hardmask
56.
[0039] Referring now to FIG. 4B, processing begins by depositing a
resist layer 58 on the metal hardmask 56 at a temperature of
40.degree. C., and then by etching the resist layer 58 to form an
opening 60. Turning now to FIG. 4C, after the opening 60 is formed,
the opening is driven toward the copper plug 44. First, the
temperature of the structure is changed to 50.degree. C. and an
aperture is formed through the metal hardmask 56. This removes the
remaining photoresist 58. Then, the temperature is adjusted to
40.degree. C. and the second polyimide layer 54 is etched. Then,
the temperature is adjusted once again to 50.degree. C. and the
second nitride layer 52 is etched. Then, the temperature is
adjusted once again to 40.degree. C. and the first polyimide layer
48 is etched. Finally, the temperature is adjusted once again to
50.degree. C. and the first nitride layer 46 is etched. This
exposes the copper plug 44. It should be noted that etching is
continuous, with only the etch temperature being changed.
[0040] Referring now to FIG. 4D, another photoresist layer 68 is
then deposited on the exposed portion of the copper plug 44 and on
the exposed portion of the metal hardmask 56. The photoresist layer
is then patterned to widen expose part of the metal hardmask 56
adjacent the opening 60. Next, referring to FIG. 4E, the
temperature of the structure is raised to about 40.degree. C. and
the photoresist layer 68 is removed. This results in exposed top
portions of the metal hardmask 56 and of the second nitride layer
52. Then, the temperature of the structure is changed to room
temperature. Referring now to FIG. 4F, copper is then electroplated
into the opening 60 to form the now finished contact 44.
[0041] It should be noted that all the foregoing processes are
implement temperature selective etching. Furthermore, all etching
performed with reference to FIG. 4C is performed continuously.
[0042] The embodiments and examples set forth herein are presented
to best explain the present invention and its practical application
and to thereby enable those skilled in the art to make and utilize
the invention. Those skilled in the art, however, will recognize
that the foregoing description and examples have been presented for
the purpose of illustration and example only. Other variations and
modifications of the present invention will be apparent to those of
skill in the art, and it is the intent of the appended claims that
such variations and modifications be covered. The description as
set forth is not intended to be exhaustive or to limit the scope of
the invention. Many modifications and variations are possible in
light of the above teaching without departing from the spirit and
scope of the following claims. It is contemplated that the use of
the present invention can involve components having different
characteristics. It is intended that the scope of the present
invention be defined by the claims appended hereto, giving full
cognizance to equivalents in all respects.
* * * * *