U.S. patent application number 11/113026 was filed with the patent office on 2005-09-01 for plasma processing method.
Invention is credited to Ichimaru, Tomoyoshi, Ikuhara, Shoji, Kagoshima, Akira, Yamamoto, Hideyuki, Yoshigai, Motohiko.
Application Number | 20050189320 11/113026 |
Document ID | / |
Family ID | 32926388 |
Filed Date | 2005-09-01 |
United States Patent
Application |
20050189320 |
Kind Code |
A1 |
Ichimaru, Tomoyoshi ; et
al. |
September 1, 2005 |
Plasma processing method
Abstract
A plasma processing method for performing plasma processing on a
sample in accordance with a process recipe with the sample being
placed on a sample table in which each of a plurality of areas is
temperature-controlled by a temperature controller. The process
recipe includes a plurality of temperature setting parameters for
the sample table, and the plasma processing is performed on the
sample in accordance with the process recipe which is prepared for
each of a plurality of process steps.
Inventors: |
Ichimaru, Tomoyoshi;
(Kudamatsu, JP) ; Yoshigai, Motohiko; (Hikari,
JP) ; Yamamoto, Hideyuki; (Kudamatsu, JP) ;
Ikuhara, Shoji; (Hikari, JP) ; Kagoshima, Akira;
(Kudamatsu, JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET
SUITE 1800
ARLINGTON
VA
22209-3873
US
|
Family ID: |
32926388 |
Appl. No.: |
11/113026 |
Filed: |
April 25, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11113026 |
Apr 25, 2005 |
|
|
|
10377885 |
Mar 4, 2003 |
|
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Current U.S.
Class: |
216/59 ;
156/345.27 |
Current CPC
Class: |
H01L 21/67253 20130101;
H01J 37/32935 20130101; H01L 21/67248 20130101; H01L 21/67069
20130101 |
Class at
Publication: |
216/059 ;
156/345.27 |
International
Class: |
C23F 001/00 |
Claims
1-4. (canceled)
5. A plasma processing method for performing plasma processing on a
sample in accordance with a process recipe with the sample being
placed on a sample table in which each of a plurality of areas is
temperature-controlled by a temperature control means, wherein the
process recipe includes a plurality of temperature setting
parameters for the sample table, and the plasma processing is
performed on the sample in accordance with the process recipe which
is prepared for each of a plurality of process steps.
6. A plasma processing method for performing plasma processing on a
sample in accordance with a process recipe with the sample being
placed on a sample table in which each of a plurality of areas is
temperature-controlled by a temperature control means, wherein the
process recipe includes a plurality of temperature setting
parameters for the sample table, and the plasma processing is
performed on the sample in accordance with the process recipe for
which at least one of set temperatures of the temperature setting
parameters is altered in response to a processing result of a
preceding process performed on the sample, the processing result
being obtained prior to the plasma processing.
7. The plasma processing method according to claim, wherein the
temperature control of the sample table is performed by using a
sample temperature measurement means or a sample table temperature
measurement means.
8. The plasma processing method according to claim 5, wherein the
plurality of areas are an inner part and an outer part of the
sample table.
9. The plasma processing method according to claim 6, wherein the
temperature control of the sample table is performed by using a
sample temperature measurement means or a sample table temperature
measurement means.
10. The plasma processing method according to claim 6, wherein the
plurality of areas are an inner part and an outer part of the
sample table.
11. The plasma processing method according to claim 7, wherein the
plurality of areas are an inner part and an outer part of the
sample table.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a plasma processing
apparatus and, more particularly, to a plasma processing apparatus
capable of performing temperature control of a sample table for
placing thereon a sample such as a semiconductor wafer for plasma
processing.
[0002] For example, Japanese. Patent Laid-open No. 2002-76103
discloses that, for the purpose of improving an accuracy in etching
a semiconductor wafer, an interior of a sample table for placing
thereon a sample is divided into two parts of an inner part and an
outer part, and coolants having different temperatures are supplied
separately to the inner part and the outer part to perform the
etching with a temperature gradient being applied to the sample
table, thereby processing a surface of the semiconductor wafer
uniformly.
[0003] An example of process recipes which have heretofore been
used in the plasma processing apparatus is shown in FIG. 7. As is
apparent from FIG. 7, temperatures set by a temperature control
unit are irrespective of the etching recipe, and the set
temperature of the inner part of the table is always 20.degree. C.
and the set temperature of the outer part of the table is always
0.degree. C. It is possible to achieve a uniformity in final
etching amounts of the semiconductor wafer surface by positively
applying the temperature gradient to the sample table as mentioned
above, not by setting the whole sample table to a uniform
temperature.
[0004] A comparison between final etching amounts of (a) a case of
setting the whole sample table to 20.degree. C. and (b) final
etching amounts of a case of setting the inner part to 20.degree.
C. and the outer part to 0.degree. C. is shown in FIG. 8. A final
etching distribution in the case of (a) is in the shape of an
inversed U (a curve), while that in the case of (b) is uniform.
This is because, when a plurality of temperature settings for the
sample table are varied from one another, considerable changes are
expected to occur in a reaction on and adsorption to sidefaces of
an etching pattern although only minor changes occur in
compositions of injected radicals and ions, influence of a density
distribution of plasma, and intensity of the injections. That is to
say, a reaction rate is increased with the temperature rise of the
sample table and an adhesion coefficient of reaction products to
the sidefaces is decreased. As a result, the sidefaces become
thinner by the temperature rise to thereby enable a reduction in
the etching amount. On the other hand, on a periphery of the
etching pattern, the final etching amount is increased because
re-adhesion of the reaction products is likely to occur due to the
temperature decrease of the semiconductor wafer.
[0005] In order to achieve high-performance and low power
consumption of semiconductor devices, a gate length of the
semiconductor devices is being made shorter every year. Since the
gate length is an important dimension which determines a device
characteristic, it is called a CD (critical dimension) value or an
etching amount. An allowable deviation of the gate length in a gate
etching process is on the order of a several nanometers, and a
slightest deviation in the manufacture process can cause defects in
the products. Further, since a diameter of the sample is being made
larger and larger, a difference between an etching result of a
central part of the sample and an etching result of a peripheral
part of the sample is likely to occur. Therefore, there is a demand
for elaborate temperature control which is suitable for the
process.
SUMMARY OF THE INVENTION
[0006] The present invention has been made in view of the above
problems, and an object of the invention is to provide a plasma
processing apparatus capable of performing temperature control of a
sample table depending on a process performed on a sample for
plasma processing.
[0007] The present invention employs the following means in order
to solve the above problems.
[0008] The object of the present invention is achieved by a plasma
processing apparatus for performing plasma processing on a sample
in accordance with a process recipe with the sample being placed on
a sample table in which each of a plurality of areas is
temperature-controlled by a temperature control means, wherein the
process recipe includes a plurality of temperature setting
parameters for the sample table, and the plasma processing is
performed on the sample in accordance with the process recipe which
is prepared for each of a plurality of process steps.
[0009] Further, the above object is achieved by a plasma processing
apparatus for performing plasma processing on a sample in
accordance with a process recipe with the sample being placed on a
sample table in which each of a plurality of areas is
temperature-controlled by a temperature control unit, wherein the
process recipe includes a plurality of temperature setting
parameters for the sample table, and the plasma processing is
performed on the sample in accordance with the process recipe in
which at least one of set temperatures of the temperature setting
parameters is altered in response to a processing result of a
preceding process performed on the sample, the processing result
being obtained prior to the plasma processing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Other objects and advantages of the invention will become
apparent from the following description of embodiments with
reference to the accompanying drawings in which:
[0011] FIG. 1 is a diagram showing an example of an etching
apparatus to which the present invention is applied;
[0012] FIG. 2 is a diagram showing an example of process recipes
according to the present invention;
[0013] FIG. 3 is a diagram showing an example of an etching system
using the etching apparatus to which the present invention is
applied;
[0014] FIG. 4 is a flowchart from a step of photolithography to a
step of altering a set temperature of a temperature control
unit;
[0015] FIG. 5 is a flowchart from a step of inputting measured mask
dimensions to a step of calculating a temperature correction
value;
[0016] FIG. 6 is a diagram showing an example of an etching
apparatus, to which the present invention is applied, including a
wafer temperature sensor;
[0017] FIG. 7 is a diagram showing an example of conventional
process recipes; and
[0018] FIG. 8 is a diagram showing a comparison between final
etching amounts of a case of controlling the whole sample table to
have a uniform temperature and final etching amounts of a case of
applying a temperature gradient to the sample table.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] A first embodiment of the present invention will hereinafter
be described with reference to accompanying drawings.
[0020] FIG. 1 is diagram showing an example of an etching apparatus
to which the present invention is applied.
[0021] A sample to be etched such as a wafer 2 is placed on a
sample table 10 in an etching reactor 1. Various etching gases are
supplied to the etching reactor 1 from cylinders 3 via valves 4.
The etching reactor 1 has an air-tight structure so as to create a
vacuum atmosphere by evacuating the reactor 1 using a vacuum pump
(not shown) via an exhaust port 5 extending to a peripheral bottom
of the etching reactor 1. A plasma generation source 6 is used for
generating plasma 7 in the etching reactor 1. A high frequency
power source 9 for applying injection energy to ions in the plasma
7 and a direct current power source 11 used for electrostatically
attracting the wafer 2 on an electrode are connected with an
electrode support shaft 8 for supporting the electrode. Coolant
circulation paths 12 and 13 used for controlling a temperature of
the sample table 10 are provided at an outer peripheral part of the
sample table 10, and coolant circulation paths 14 and 15 for
controlling a temperature of the sample table 10 are provided at an
inner peripheral part of the sample table 10. One end of each of
the coolant circulation paths 12 and 13 is connected to a
temperature control unit 16, and one end of each of the coolant
circulation paths 14 and 15 is connected to a temperature control
unit 17.
[0022] Although two temperature control units are used for
controlling the temperatures in the present embodiment, a plurality
of coolants may be prepared by using one temperature control unit
and a temperature converter which is provided at a position midway
of a circulation path.
[0023] FIG. 2 is a diagram showing an example of process recipes in
the first embodiment of the present invention.
[0024] In a typical plasma processing apparatus, a controller
microcomputer for a plasma processing apparatus controls devices
and components required for the process in accordance with a
process recipe in which many processing parameters such as
processing time, a pressure in the vacuum reactor, power to be
supplied to the plasma generation unit, process gas flow rates, and
high frequency power to be applied to the sample table are
preset.
[0025] Also, in the case where the plasma processing for one
substrate is performed through a plurality of divided process steps
in such a manner that processing on a resist layer is performed in
STEP 1, processing on a SiN layer is performed in STEP 2, and
processing on a polysilicon layer is performed in STEP 3, the
devices and components are controlled for processing in accordance
with parameter settings of a process recipe for the next process
step every time the process steps are switched from one to
another.
[0026] The present invention enables an optimum temperature control
of the sample table for each of the process steps in view of the
process steps and types of layers by allowing a plurality of
temperature setting parameters for the sample table to be included
in each of the process recipes for the process steps and by
associating the sample table with the process recipes. Thus, it is
possible to control the final etching amount of the wafer
surface.
[0027] In addition, it is unnecessary to stop the temperature
control of the sample table during a halt of the processing on the
sample, and it is possible to perform the temperature control
continuously on the set temperatures which have been employed in
the preceding process step. Also, it is possible to perform the
temperature control in advance of processing on a next sample by
setting the temperatures to the set temperatures which will be
employed in a first process step of the processing on the next
sample.
[0028] A second embodiment of the present invention will
hereinafter be described with reference to the accompanying
drawings.
[0029] In general, it is usual to use the same recipe in the bulk
production which is operated with the same process. This is because
satisfactory reproducibility is achieved if plasma characteristic
and so forth are kept at a constant level. Further, an alteration
in a recipe (hereinafter referred to as "plasma recipe") which
influences on the plasma characteristic can be a waste of data
which have been accumulated by now. To find out a new optimum
process recipe we must have trial and error for which a
considerable time and cost will be spent. However, even if the
etching process is performed by using the same plasma recipe, it is
difficult to attain a constant etching result in some cases due to
various disturbances such as changes with time and variation in
production caused in the subsequent process step. Therefore, the
following configuration is employed in the present embodiment in
view of the above problems.
[0030] FIG. 3 is a diagram showing an example of an etching system
using an etching apparatus to which the present invention is
applied.
[0031] An inspection device 31 is a CD-SEM (also called "length
measuring SEM") for measuring an etching amount of a sample of a
preceding process step or a film thickness measurement instrument
for measuring a layer thickness, the CD-SEM and the instrument
being used prior to performing an etching process. An inspection
device 32 serves to measure a final etching amount (etching amount
after the etching process). In the present embodiment, both of the
inspection devices 31 and 32 are CD-SEMs.
[0032] A database 33 accumulates relational expressions in which a
set temperature of the sample table to be altered is calculated if
an inspection result obtained by the aforementioned inspection and
a target etching amount which is an initial design value are given.
Also, every time the etching process is performed, the database 33
accumulates data other than those described above, such as an
etching amount of each of the layers in a preceding process (before
the etching process), a final etching amount, a final shape (shape
after the etching process), plasma emission during the process, and
an etching rate.
[0033] A flowchart from a step of photolithography to a step of
changing the set temperature by the use of the temperature control
unit is shown in FIG. 4.
[0034] A sample which has been subjected to a photolithography
process (Step 41) undergoes the processing on a plurality of zones
of ZONE 1 and ZONE 2 branched for pre-measurement (hereinafter
referred to as "CD pre-measurement") of mask dimensions using the
CD-SEM 31 (Steps 42 and 43). Temperature correction value of the
respective zones to be altered are calculated from the CD
pre-measurement results and the data stored in the database 33
including the target etching amounts, the types of the layers to be
processed, etc. (Steps 45 and 46). The set temperatures are altered
after comparing the calculated temperature correction values with
the set temperatures defined in the plasma recipe (Step 47).
[0035] Although the sample table temperature is divided into the
inner part temperature and the outer part temperature in the
present embodiment, the present invention is not limited thereto,
and it is possible to perform the temperature control by dividing
the sample table into a larger number of areas.
[0036] A flowchart from a step of inputting measured mask
dimensions to a step of calculating temperature correction values
is shown in FIG. 5.
[0037] First of all, the target final etching amounts are inputted
into the database 33 (Step 52). The mask dimensions of the
respective zones are measured to be inputted into the database 33
(Step 51). Then, the measured mask dimensions of the respective
zones are compared with the target final etching amounts. A rate
correction value of each of the zones can be calculated by, for
example, dividing each of differences obtained by the comparison by
the etching time of STEP 1 (Steps 53 and 54). As is apparent from
FIG. 5., since the mask dimension measurement value (a) is larger
than the target final etching amount (b), the etching process must
be performed to be larger than the normal etching amount. Then,
temperature correction values of the respective zones are
calculated from the calculated rate correction values and the
relational expressions of the types of the layers to be processed
and the temperatures of the sample table stored in the database 33
(Step 55).
[0038] An alteration unit (not shown) or the like for altering the
set temperatures based on the database 33 and the temperature
correction values may be provided either in the etching apparatus
or in the inspection device. Alternatively, the alteration unit may
be connected with a host computer or the like which is linked to a
network of a semiconductor manufacture line.
[0039] In the present invention, even if a deviation from a target
etching amount occurs on a product during a process preceding to
the etching process, such as a photolithography process, it is
possible to perform etching including corrections for achieving
initial design values in the etching process owing to the
above-described configuration. Further, if the result of the
etching is inspected, the inspection result is compared with the
target final etching amount to thereby judge whether or not the
current set temperatures of the sample table are proper, and then
the temperatures are properly altered until the desired etching
amount is achieved, it is also possible to assimilate machine
differences among etching apparatuses.
[0040] Further, since the variations in semiconductor surfaces,
such as U-shape distribution and inversed U-shape distribution, are
suppressed in the present embodiment by properly altering the
temperatures of the sample table without altering the plasma recipe
which influences on the plasma characteristic, the present
embodiment is free from serious side effects.
[0041] In addition, although the case where the plasma recipe is
not altered is described in the present embodiment, it is apparent
that the present invention is applicable to apparatuses in which
the plasma recipe is altered during the processing.
[0042] A third embodiment of the present invention will hereinafter
be described with reference to the accompanying drawings.
[0043] FIG. 5 is a diagram showing an example of an etching
apparatus, to which the present invention is applied, including a
wafer temperature sensor 62.
[0044] Conventional temperature control units for the sample table
perform a temperature control with respect to set temperatures by
monitoring coolants or the like by using a temperature sensor which
is provided in the temperature control units. However, the
temperatures of the coolants monitored by the temperature control
unit can sometimes differ from actual temperatures of a backface of
a wafer. Also, for a comparison between a first wafer and a
twenty-fifth wafer after the start of processing, for example, the
twenty-fifth wafer tends to be high in temperature due to radiation
heat from the etching reactor. Furthermore, since heat input is
greater on an outer peripheral part of the wafer, the temperature
of the outer peripheral part tends to be higher than that of a
central part of the wafer. Therefore, in the present embodiment,
the temperatures of the backface of the wafer are directly measured
by the use of the wafer temperature sensor 62 or an electrode
temperature sensor (not shown) to provide the measurement results
as monitor values of the temperature control unit, thereby
improving an effect of controlling an etching amount of the wafer
surface in each of processes, each of process steps, and each of
layers.
[0045] While the invention has been described in its preferred
embodiments, it is to be understood that the words which have been
used are words of description rather than limitation and that
changes within the purview of the appended claims may be made
without departing from the true scope and spirit of the invention
in its broader aspects.
* * * * *