U.S. patent application number 13/669113 was filed with the patent office on 2013-05-16 for dual-bulb lamphead control methodology.
This patent application is currently assigned to Applied Materials, Inc.. The applicant listed for this patent is Sanjeev Baluja, Scott A. Hendrickson, Abhijit Kangude, Liliya Krivulina, Michael Martinelli, Thomas Nowak, Juan Carlos Rocha-Alvarez, YAO-HUNG YANG. Invention is credited to Sanjeev Baluja, Scott A. Hendrickson, Abhijit Kangude, Liliya Krivulina, Michael Martinelli, Thomas Nowak, Juan Carlos Rocha-Alvarez, YAO-HUNG YANG.
Application Number | 20130122611 13/669113 |
Document ID | / |
Family ID | 46064714 |
Filed Date | 2013-05-16 |
United States Patent
Application |
20130122611 |
Kind Code |
A1 |
YANG; YAO-HUNG ; et
al. |
May 16, 2013 |
DUAL-BULB LAMPHEAD CONTROL METHODOLOGY
Abstract
The present invention generally relates to methods of
controlling UV lamp output to increase irradiance uniformity. The
methods generally include determining a baseline irradiance within
a chamber, determining the relative irradiance on a substrate
corresponding to a first lamp and a second lamp, and determining
correction or compensation factors based on the relative
irradiances and the baseline irradiance. The lamps are then
adjusted via closed loop control using the correction or
compensation factors to individually adjust the lamps to the
desired output. The lamps may optionally be adjusted to equal
irradiances prior to adjusting the lamps to the desired output. The
closed loop control ensures process uniformity from substrate to
substrate. The irradiance measurement and the correction or
compensation factors allow for adjustment of lamp set points due to
chamber component degradation, chamber component replacement, or
chamber cleaning.
Inventors: |
YANG; YAO-HUNG; (Santa
Clara, CA) ; Kangude; Abhijit; (Santa Clara, CA)
; Baluja; Sanjeev; (Campbell, CA) ; Martinelli;
Michael; (Santa Clara, CA) ; Krivulina; Liliya;
(Sunnyvale, CA) ; Nowak; Thomas; (Cupertino,
CA) ; Rocha-Alvarez; Juan Carlos; (San Carlos,
CA) ; Hendrickson; Scott A.; (Brentwood, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
YANG; YAO-HUNG
Kangude; Abhijit
Baluja; Sanjeev
Martinelli; Michael
Krivulina; Liliya
Nowak; Thomas
Rocha-Alvarez; Juan Carlos
Hendrickson; Scott A. |
Santa Clara
Santa Clara
Campbell
Santa Clara
Sunnyvale
Cupertino
San Carlos
Brentwood |
CA
CA
CA
CA
CA
CA
CA
CA |
US
US
US
US
US
US
US
US |
|
|
Assignee: |
Applied Materials, Inc.
|
Family ID: |
46064714 |
Appl. No.: |
13/669113 |
Filed: |
November 5, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13011687 |
Jan 21, 2011 |
8309421 |
|
|
13669113 |
|
|
|
|
61416955 |
Nov 24, 2010 |
|
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|
Current U.S.
Class: |
438/7 ;
257/E21.328; 257/E21.529; 315/151 |
Current CPC
Class: |
H01L 21/67115 20130101;
H05B 41/3922 20130101; H05B 41/3921 20130101 |
Class at
Publication: |
438/7 ; 315/151;
257/E21.529; 257/E21.328 |
International
Class: |
H05B 37/02 20060101
H05B037/02; H01L 21/26 20060101 H01L021/26; H01L 21/66 20060101
H01L021/66 |
Claims
1. A method of controlling lamp output in a process chamber having
at least a first lamp and a second lamp, comprising: positioning a
first light pipe adjacent to an sensor; measuring the irradiance
from the first lamp through the first light pipe with the sensor,
wherein the first light pipe allows substantially only light from
the first lamp therethrough to be measured by the sensor;
positioning a second light pipe adjacent to the sensor; measuring
the irradiance from the second lap through the second light pipe
with the sensor, wherein the second light pipe allows substantially
only light form the second lamp therethrough to be measured by the
sensor; adjusting the irradiance of the first lamp based on the
measured irradiance of the first lamp; and adjusting the irradiance
of the second lamp based on the measured irradiance of the second
lamp.
2. The method of claim 1, wherein positioning the first light pipe
comprises: rotating a housing including the first light pipe; and
rotating the first lamp.
3. The method of claim 2, wherein positioning the second light pipe
comprises: rotating the housing including the second light pipe;
and rotating the second lamp.
4. The method of claim 3, wherein each of the first lamp and the
second lamp are coupled to the housing.
5. The method of claim 1, further comprising: determining a
compensation factor for the first lamp; and determining a
compensation factor for the second lamp.
6. The method of claim 1, wherein: measuring the irradiance from
the first lamp comprises rotating the first lamp during the
measuring; and measuring the irradiance from the second lamp
comprises rotating the second lamp during the measuring.
7. The method of claim 1, wherein adjusting the irradiance of the
first lamp comprises adjusting the irradiance of the first lamp
using a first closed-loop algorithm, and adjusting the irradiance
of the second lamp comprises adjusting the irradiance of the second
lamp using a second closed-loop algorithm.
8. A method of controlling lamp output in a process chamber having
at least a first lamp and a second lamp, comprising: positioning a
first light pipe coupled to a reflective housing adjacent to an
sensor; measuring the irradiance from the first lamp through the
first light pipe with the sensor, wherein the first light pipe
allows substantially only light from the first lamp therethrough to
be measured by the sensor; positioning a second light pipe coupled
to the reflective housing adjacent to the sensor; measuring the
irradiance from the second lap through the second light pipe with
the sensor, wherein the second light pipe allows substantially only
light form the second lamp therethrough to be measured by the
sensor; determining a compensation factor for the first lamp;
determining a compensation factor for the second lamp; adjusting
the irradiance of the first lamp based on the measured irradiance
of the first lamp; and adjusting the irradiance of the second lamp
based on the measured irradiance of the second lamp.
9. The method of claim 8, wherein the first lamp is coupled to the
reflective housing, and wherein positioning the first light pipe
comprises positioning the first lamp.
10. The method of claim 9, wherein the second lamp is coupled to
the reflective housing, and wherein positioning the second light
pipe comprises positioning the second lamp.
11. The method of claim 10, wherein: measuring the irradiance from
the first lamp comprises rotating the first lamp during the
measuring; and measuring the irradiance from the second lamp
comprises rotating the second lamp during the measuring.
12. The method of claim 8, wherein adjusting the irradiance of the
first lamp comprises adjusting the irradiance of the first lamp
using a first closed-loop algorithm, and adjusting the irradiance
of the second lamp comprises adjusting the irradiance of the second
lamp using a second closed-loop algorithm.
13. The method of claim 8, further comprising ultraviolet curing a
substrate disposed in the process chamber using the first lamp and
the second lamp.
14. A process chamber, comprising: an irradiance sensor; a
rotatable first lamp; a rotatable second lamp; a rotatable
reflective housing including a plurality of light pipes, wherein
each light pipe is positioned to allow substantially only light
from either the first lamp or second lamp therethrough to be
measured by the irradiance sensor.
15. The process chamber of claim 14, wherein the rotatable first
lamp and the rotatable second lamp are coupled to the rotatable
reflective housing.
16. The process chamber of claim 14, wherein the process chamber
consists of a single irradiance sensor.
17. The process chamber of claim 14, further comprising a substrate
support and quartz window disposed between the substrate support
and the rotatable reflective housing.
18. The process chamber of claim 17, wherein each of the first lamp
and the second lamp comprise a primary reflector to direct light
towards the substrate support.
19. The process chamber of claim 14, wherein interior surfaces of
the light pipes are textured.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. patent application
Ser. No. 13/011,687, filed Jan. 21, 2011, which claims benefit of
U.S. Provisional Patent Application Ser. No. 61/416,955, filed Nov.
24, 2010. Each of the aforementioned patent applications is herein
incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of the present invention generally relate to
methods of ultraviolet curing a substrate.
[0004] 2. Description of the Related Art
[0005] Materials such as silicon oxide, silicon carbide and
carbon-doped silicon oxide films find widespread use in the
fabrication of semiconductor devices. One approach for forming such
silicon-containing films on a substrate is through the process of
chemical vapor deposition (CVD). Subsequent to formation of the CVD
films, ultraviolet (UV) radiation can be used to cure and to
densify the deposited films.
[0006] One manner of supplying UV radiation to a substrate uses UV
radiation lamps. The bulbs used in UV lamp systems are consumable
items with their life determined by a number of factors, including
total hours of operation, number of starts, time in standby mode,
power level, and other conditions. As UV bulbs near the end of
their usable life, their output changes, thus affecting
substrate-to-substrate processing uniformity. Additionally, UV
bulbs within a chamber may not all be replaced simultaneously,
thus, UV bulbs within the same lamp head may have different output
levels. The non-uniform output within the chamber affects process
uniformity across the processed substrates.
[0007] Thus, there is a need to improve the control of UV bulb
output to increase process uniformity.
SUMMARY OF THE INVENTION
[0008] The present invention generally relates to methods of
controlling UV lamp output to increase irradiance uniformity. The
methods generally include determining a baseline irradiance within
a chamber, determining the relative irradiance on a substrate
corresponding to a first lamp and a second lamp, and determining
correction or compensation factors based on the relative
irradiances and the baseline irradiance. The lamps are then
adjusted via closed loop control using the correction or
compensation factors to individually adjust the lamps to the
desired output. The lamps may optionally be adjusted to equal
irradiances prior to adjusting the lamps to the desired output. The
closed loop control ensures process uniformity from substrate to
substrate. The irradiance measurement and the correction or
compensation factors allow for adjustment of lamp set points due to
chamber component degradation, chamber component replacement, or
chamber cleaning.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] So that the manner in which the above recited features of
the present invention can be understood in detail, a more
particular description of the invention, briefly summarized above,
may be had by reference to embodiments, some of which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this invention and are therefore not to be considered limiting of
its scope, for the invention may admit to other equally effective
embodiments.
[0010] FIG. 1 is a partial schematic illustration of a tandem
process chamber configured for UV curing.
[0011] FIG. 2A is a schematic illustration of one of the UV cure
chambers of the tandem process chamber of FIG. 1.
[0012] FIG. 2B is a schematic illustration of a bottom view of a UV
lamp head for a UV cure chamber.
[0013] FIG. 2C is a schematic illustration of a secondary reflector
for a UV cure chamber.
[0014] FIG. 3 is a flow chart illustrating one embodiment for
adjusting UV intensity within a UV cure chamber.
[0015] FIG. 4 is a flow chart illustrating another embodiment for
adjusting UV intensity within a UV cure chamber.
[0016] To facilitate understanding, identical reference numerals
have been used, where possible, to designate identical elements
that are common to the figures. It is contemplated that elements
disclosed in one embodiment may be beneficially utilized on other
embodiments without specific recitation.
DETAILED DESCRIPTION
[0017] The present invention generally relates to methods of
controlling UV lamp output to increase irradiance uniformity. The
methods generally include determining a baseline irradiance within
a chamber, determining the relative irradiance on a substrate
corresponding to a first lamp and a second lamp, and determining
correction or compensation factors based on the relative
irradiances and the baseline irradiance. The lamps are then
adjusted via closed loop control using the correction or
compensation factors to individually adjust the lamps to the
desired output. The lamps may optionally be adjusted to equal
irradiances prior to adjusting the lamps to the desired output. The
closed loop control ensures process uniformity from substrate to
substrate. The irradiance measurement and the correction or
compensation factors allow for adjustment of lamp set points due to
chamber component degradation, chamber component replacement, or
chamber cleaning.
[0018] Embodiments of the present invention may be practiced in the
NANOCURE.TM. chamber available from Applied Materials, Inc., of
Santa Clara, Calif. It is contemplated that other chambers,
including those from other manufacturers, may also benefit from
embodiments described herein.
[0019] FIG. 1 is a partial schematic illustration of a tandem
process chamber 100 configured for UV curing. An exemplary tandem
process chamber is the PRODUCER.TM. chamber available from Applied
Materials, Inc., of Santa Clara, Calif. The tandem process chamber
100 includes two UV cure chambers 101 each adapted to process one
or more substrates therein. Each of the UV cure chambers are
generally separated by a wall (not shown). The tandem process
chamber 100 includes a body 102 and lid 104 that is hinged to the
body 102. Coupled to the upper surface of the lid is a first lower
housing 106a and a second lower housing 106b. Each of the lower
housings 106a, 106b are adapted to hold a secondary reflector
therein. Positioned above each of the lower housings 106a, 106b are
upper housings 108a, 108b, respectively. Each upper housing 108a,
108b is rotatable and has a lamp head positioned therein to provide
UV radiation through the lower housings 106a, 106b and into the
body 102 in which one or more substrate may be positioned to
receive the UV radiation.
[0020] FIG. 2A is a schematic illustration of one of the UV cure
chambers 101 of the tandem process chamber 100 of FIG. 1. The UV
cure chamber 101 includes a UV lamp head 210, a secondary reflector
220, a quartz window 222, a substrate support 224, and controllers
229. The UV lamp head 210 is disposed within the upper housing 108a
and includes two UV lamps 212a and 212b. Each UV lamp 212a, 212b
includes a UV bulb 214a, 214b. A primary reflector 216a is
positioned above and around the UV bulb 214a and is adapted to
direct UV radiation from the UV bulb 214a through the quartz window
222 towards the substrate support 224. Similarly, a primary
reflector 216b is positioned above and around the UV bulb 214b and
is adapted to direct UV radiation from the UV bulb 214b through the
quartz window 222 towards the substrate support 224. The output or
intensity of the UV bulbs 214a and 214b is controlled by respective
controllers 229. Although each UV lamp 212a, 212b of each UV cure
chamber 101 is shown as having its own controller 229, it is
contemplated that a single controller may used to control all
aspects of the tandem process chamber 100.
[0021] A secondary reflector 220 is located within the lower
housing 106a and is positioned between the UV lamp head 210 and a
semiconductor substrate 226. The secondary reflector 220 is coupled
to the lower surface of the UV lamps 212a and 212b, and is
rotatable with the lamps 212a and 212b which are coupled to the
rotatable upper housings 108a, 108b. The lower edge of the
secondary reflector 220 has an inner diameter that is smaller than
a diameter of the substrate 226 so there is no optical gap between
the secondary reflector 220 and the outside diameter of the
substrate 226 as viewed from the direction of the lamp head 210.
The secondary reflector 220 has a channeling effect reflecting UV
radiation that would otherwise fall outside the boundary of the
primary reflectors' flood pattern so that such radiation impinges
upon the substrate 226 being UV cured. Thus, the intensity of the
energy distributed to the substrate 226 is increased. The secondary
reflector 220 alters the flood pattern of the UV lamps 212a, 212b
from a substantially rectangular area to a substantially circular
shape that corresponds to the substantially circular shape of the
substrate 226. A sensor 225 is coupled to the interior surface of
the lower housing 106a and is positioned to sense UV radiation
through holes disposed in the secondary reflector 220 as the
secondary reflector 220 rotates.
[0022] The quartz window 222 is positioned between the lamp head
210 and the substrate 226. A small gap 228 exists between the
bottom of the secondary reflector 220 and the quartz window 222 to
allow for air flow around the secondary reflector 220 to facilitate
cooling. Air flow may be provided to the secondary reflector and/or
the quartz window through one or more openings disposed in the
lower housing 106a.
[0023] The UV bulbs 214a and 214b are microwave arc lamps; however,
other types of UV sources are contemplated, including pulsed xenon
flash lamps or high-efficiency UV light emitting diode arrays. The
UV bulbs 214a and 214b are sealed plasma bulbs filled with one or
more gases such as xenon or mercury for excitation by power
sources, such as microwave generators. The microwave generators
include one or more magnetrons to excite the gases within the UV
bulbs 214a and 214b. Alternatively, radio frequency (RF) energy
sources may be used to excite the gases within the UV bulbs 214a
and 214b. The RF excitation can be capacitive or inductive;
however, an inductively coupled plasma bulb can more efficiently
generates greater bulb brilliancy by generation of denser
plasma.
[0024] Desirably, the UV bulbs 214a and 214b emit light across a
broad band of wavelengths from 180 nm to 400 nm. The gases selected
for use within the UV bulbs 214a and 214b generally determine the
wavelengths of radiation emitted. Since shorter wavelengths tend to
generate ozone when oxygen is present within the UV cure chamber
101, UV light emitted by the UV bulbs 214a and 214b is tuned to
predominantly generate broadband UV light above 200 nm to avoid
ozone generation during cure processes.
[0025] FIG. 2B is a schematic illustration of a bottom view of a UV
lamp head 210 for a UV cure chamber 101. The UV lamp head 210
houses two lamps 212a, 212b, each of which contains an elongated UV
bulb 214a, 214b. The bulbs generate UV radiation which is directed
to the substrate 226 by the primary reflectors 216a, 216b and the
secondary reflector 220. The primary reflector 216a is formed from
a portion 260a and a portion 261a with a gap therebetween.
Similarly, the primary reflector 216b is formed from a portion 260b
and a portion 261b with a gap therebetween. Although the UV lamp
head 210 is shown as containing two elongated bulbs, it is
contemplated that the UV lamp head 210 may contain more than two
bulbs.
[0026] FIG. 2C is a schematic illustration of a secondary reflector
220 for a UV cure chamber 101. The secondary reflector 220 is
oriented in the chamber such that a portion 238 is located adjacent
to the lamp 212a, and a portion 240 is located adjacent to the lamp
212b. The secondary reflector not only directs UV radiation towards
the substrate 226, but also allows for measurement of UV radiation
intensity generated or reflected by different components within the
UV cure chamber 101. The secondary reflector 220 includes light
pipes 230-235 to monitor separate components within the UV cure
chamber 101. Although the term "pipe" is used, the light pipes
230-235 may simply be holes disposed through the wall of the
secondary reflector 220, and may or may not include an elongated
tube coupled to the outer wall of the secondary reflector. A sensor
225 adapted to measure UV radiation intensity is coupled to a lower
housing adjacent the secondary reflector 220. The sensor 225 is
positioned to receive UV radiation exiting each of the light pipes
230-235 while the secondary reflector 220 rotates during
processing. The sensor 225 is connected to the controllers 229 and
is adapted to provide UV intensity information to the controllers
229.
[0027] The amount of UV radiation reaching the substrate is
function of UV radiation emitted from the UV bulbs 214a, 214b as
well as the light reflected from the portions 260a, 260b, 261a, and
261b of the primary reflectors 216a, 216b. This function is
generally empirically determined, and it is to be understood that
this function is generally different for each individual UV cure
chamber 101. The function varies depending on the type of UV bulb
used, the reflectivity of the primary and secondary reflectors,
position of the substrate relative to the UV bulbs and reflectors,
and chamber dimensions, among other factors.
[0028] Each light pipe 230-235 is coupled to the secondary
reflector 220 at an angle which allows only light from the one
specific chamber component to pass therethrough and contact the
sensor 225 as the light pipes 230-235 rotate past the stationary
sensor 225. Depending on the thickness of the wall of the secondary
reflector 220 in the region of an individual light pipe, the length
of the light pipe may be extended by inserting an aluminum tube
into the hole or slot formed through the wall of the secondary
reflector 220. To reduce the effects of reflectance within the
light pipe and to ensure that only radiation rays within the
particular angle of acceptance reach the sensor 225, the interior
surfaces of a light pipe may be lined or coated with an appropriate
light absorbing material. Alternatively, the interior surface of a
light pipe may be treated to have a roughened or textured surface
to dissipate, via multiple reflections, unwanted light that
contacts the wall of the light pipes 230-235.
[0029] In monitoring the individual components of the UV cure
chamber 101, it is desirable that the light pipes 230-235 allow
only rays generated by or reflected by the desired component to
reach the sensor at the end of the light pipe that monitors that
component. In some instances it may not be practical to design the
light pipe such that 100 percent of the rays reaching the sensor
225 are from a single component. Instead, the light pipe may be
designed so that a suitably high percentage, e.g., 80 percent or 90
percent of the rays that reach the sensor 225 are from the desired
component. In such a design, the controllers 229 should be able to
account for the portion of the sensed light which is from an
undesired component.
[0030] During processing, the lamps 212a, 212a, as well as the
secondary reflector coupled thereto rotate while providing UV
radiation to the substrate 226. As the light pipes 230-235 rotate
past the sensor 225, UV output or reflectance of specific chamber
components is determined. To increase the accuracy of the sensor
measurements (e.g., increase the number of sampling points), the
rotational speed of the lamps 212a, 212b and the secondary
reflector 220 may be reduced when any of the light pipes 230-235
are adjacent to the sensor 225. For example, when any of the light
pipes 230-235 are passing by the sensor 225, the secondary
reflector may rotate at about 0.1 to about 0.2 revolutions per
minute. When any of the light pipes are not adjacent the sensor 225
(e.g., the area of the secondary reflector 220 between the light
pipes 230-235), the secondary reflector may rotate at greater than
one revolution per minute, for example, at about one to about two
revolutions per minute. Thus, the rotational speed of the lamps
212a, 212b and the secondary reflector 220 are variable.
[0031] In the embodiment of FIG. 2C, the light pipe 230 monitors
the reflectance of the portion 260a of the primary reflector 216a.
The light pipe 231 monitors the reflectance of the portion 261a of
the primary reflector 216a. The light pipe 232 monitors the
reflectance of the portion 261b of the primary reflector 216b. The
light pipe 233 monitors the reflectance of the portion 260b of the
primary reflector 216b. The light pipes 234 and 235 monitor the
intensity of the UV bulbs 214a and 214b, respectively.
[0032] The ability of the secondary reflector 220 to monitor the UV
radiation generated by or reflected by individual components allows
for monitoring and compensation of those components within the UV
chamber 101. Monitoring of individual components is desirable since
light reflectance or generation of these components decreases with
time. For example, material may accumulate on the surface of the
primary reflectors 216a, 216b, which decreases the amount and/or
intensity of reflected UV radiation directed towards the substrate
226. Also, material may accumulate on the surface of the quartz
window 222 thereby decreasing the amount of UV radiation passing
therethrough and reaching the substrate 226. Further, the intensity
of the UV bulbs 214a, 214b decreases as the UV bulbs 214a, 214b
approach their useful life. However, since the secondary reflector
220 allows the intensity of the individual components within the UV
chamber to be monitored, a correction factor can be adjusted to
account for the decreasing efficiency of the components. Thus,
substrate 226 can receive a uniform amount of UV radiation, thereby
increasing process uniformity, even though light reflectance or
generation of some components has decreased.
[0033] In a typical UV curing process, a single UV radiation sensor
located within the UV curing chamber measures the overall level of
UV radiation within the chamber. For example, the sensor may
indicate that the level of UV radiation within the chamber is too
low, in which case, the power applied to the UV lamps is increased
in order to increase the level of UV radiation within the chamber.
A first problem with the typical UV curing process is that the
sensor measures overall UV intensity, and not the intensity of
individual components. Thus, if one UV bulb is nearly burned out,
or if one reflector is covered in particle accumulation and has
lost its ability to efficiently reflect UV radiation, the sensor is
unable to identify the decreasing efficiency of the component.
Secondly, since the typical UV curing process is unable to detect
the UV radiation reflected or generated by individual components,
the typical UV process is unable to adjust process parameters to
account for the decreasing efficiency of a single component.
Rather, the typical UV process just applies more power to the
system as a whole to adjust the UV intensity within the chamber,
and does not take into account the amount of power being applied to
individual UV bulbs. This results in non-uniform irradiation of the
substrate and decreased process uniformity
[0034] FIG. 3 is a flow chart illustrating one embodiment for
adjusting UV intensity within a UV cure chamber 101. In step 340, a
baseline irradiance is established. The baseline irradiance is the
irradiance on the substrate corresponding to optimal performance of
all chamber components. Generally, the baseline irradiance
corresponds to 100 percent lamp performance. However, during
processing, the UV lamps 212a and 212b are set to a set point less
than 100 percent to allow for adjustment in response to component
degradation. For example, during processing, the UV lamps 212a,
212b may be set at about 80 percent of maximum power.
[0035] As substrates are processed within the UV cure chamber 101,
the efficiency of individual chamber components decreases. Thus,
the amount of UV radiation reaching the substrate 226 also
decreases. The secondary reflector 220 and the sensor 225
positioned thereby allow for measurement of the decreasing
efficiency of the system, and correspondingly, the amount of UV
radiation reaching the substrate 226. In step 341, the amount of UV
radiation being delivered to the substrate 226 by a first lamp is
measured via the secondary reflector 220 and the sensor 225
positioned near the secondary reflector 220. The amount of UV
radiation reaching the substrate 226 is determined by measuring the
decreasing efficiency of individual chamber components. The
measured irradiance reaching the substrate 226 for a given lamp is
referred to as the relative irradiance. Prior to processing, the
relative irradiance is equal to the process set point, since no
degradation of chamber components has yet occurred. In step 342,
the amount of UV radiation being delivered to the substrate 226 by
a second lamp is measured via the secondary reflector 220 and the
sensor 225. Additionally, the relative irradiance for the second
lamp is also determined. Generally, steps 341 and 342 occur
simultaneously; however, it is contemplated that steps 341 and 342
may occur successively.
[0036] In step 343, a lamp compensation factor is determined for
each of lamps 212a and 212b. The lamp compensation factor is the
relative irradiance divided by the baseline irradiance. In step
344, the controllers 229 containing a closed-loop algorithm adjust
the power applied to each of lamps 212a and 212b. The target point
for the controller is equal to the original set point (e.g., 80
percent) divided by the lamp compensation factor. Thus, as more
substrates are processed and the efficiency of the chamber
components decreases, the controllers 229 increase the set point
(since the lamp control factor is generally less than 1). Although
the set point is increased, the chamber efficiency has decreased;
therefore the total amount of UV radiation reaching the substrate
226 remains constant from process to process. Steps 341-344 may be
performed real time, or every few substrates, or as desired.
Generally, step 340 is performed at the beginning of a process to
establish the desired amount of UV radiation reaching the substrate
226 for a specific process recipe.
[0037] As described in relation to FIG. 3, each of the lamps 212a
and 212b is controlled by its own closed-loop algorithm stored on
the controllers 229. Since the process chamber 100 includes two UV
cure chambers 101, the tandem process chamber 100 includes four
controllers 229. It is contemplated that the lamps 212a, 212a may
contain more than one bulb 214a, 214b each, in which case, the
controllers 229 could provide closed loop control for each bulb or
for each lamp 212a, 212b individually.
[0038] The control process outlined in FIG. 3 allows for uniform
irradiation of a substrate 226 regardless of the condition of the
chamber components, since each of the lamps 212a, 212b can be
individually controlled and compensated for specific component
degradation. This is desirable since chamber components do not
always degrade at that same rate. For example, if the bulb 214a
burns out prior to the bulb 214b, then the bulb 214a will be
replaced with a new (and brighter bulb). Thus, the irradiation
provided by the new bulb and the bulb 214b would not be equivalent.
However, using the control process outlined in FIG. 3, the output
of the new bulb and the bulb 214b could be adjusted using
compensation factors to ensure that UV irradiation across the
substrate 226 is uniform. The control process of FIG. 3 would
likewise apply to the replacement of other chamber components, such
as the magnetrons or the primary reflectors 216a, 216b.
Additionally, the control process of FIG. 3 is beneficial when
chamber components may be cleaned at different rates.
[0039] FIG. 4 is a flow chart illustrating another embodiment for
adjusting UV intensity within a UV cure chamber. In step 450, a
baseline irradiance is established similar to step 340. In step
451, a relative irradiance corresponding to a first lamp is
determined, similar to step 341. In step 452, a relative irradiance
corresponding to a second lamp is determined, similar to step 342.
Steps 451 and 452 generally occur simultaneously; however, it is
contemplated that steps 451 and 452 may occur successively.
[0040] In step 453, a lamp variance correction factor is
determined. The lamp variance correction factor is the factor by
which the set point of lamp 212a or 212b, whichever has the lower
relative irradiance, must be adjusted so that both lamps 212a and
212b have the same relative irradiance. In step 454, the lamp
variance correction factor is applied so that both lamps 212a and
212b have the same relative irradiance. Thus, even though the
relative irradiance may not be equal to the baseline irradiance, at
least the irradiance across the substrate 226 is uniform.
[0041] In step 455, both of the lamps 212a and 212b are adjusted
simultaneously to the desired UV output. This can be accomplished
by determining a compensation factor as described in steps 343 and
344. Alternatively, since the lamps 212a and 212b have the same UV
irradiance output (due to the applied lamp variance correction
factor), the lamp head 210 can be adjusted in response to the
signal from a single UV sensor. Furthermore, since the lamps 212a
and 212b have previously been adjusted to the same relative
irradiance, the change in UV irradiance across the substrate is
uniform as the controller adjusts the output of the lamps 212a and
212b. This results in a more uniform curing across the processed
substrate since the rate of change of each lamp is approximately
equal. After adjusting the outputs of lamps 212a and 212b for a
first UV cure chamber 101, the process is repeated for a second UV
cure chamber 101. Desirably, the output of lamps 212a and 212b in
each of the UV cure chambers 101 is equal.
[0042] Benefits of the present invention include closed loop
control of UV cure processes within a UV cure chamber.
Additionally, the condition and efficiency of chamber components
can be monitored during processing, and decreases in efficiency can
be compensated for by applying correction factors. Furthermore, the
application of the correction factors allows uniform UV lamp
output, as well uniform UV lamp head output, thereby increasing
process uniformity.
[0043] While the foregoing is directed to embodiments of the
present invention, other and further embodiments of the invention
may be devised without departing from the basic scope thereof, and
the scope thereof is determined by the claims that follow.
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