U.S. patent application number 13/524914 was filed with the patent office on 2012-10-04 for plasma processing apparatus and plasma processing method.
This patent application is currently assigned to Hitachi High-Technologies Corporation. Invention is credited to Kousa Hirota, Masahiro Sumiya, Motohiro Tanaka.
Application Number | 20120252200 13/524914 |
Document ID | / |
Family ID | 42398059 |
Filed Date | 2012-10-04 |
United States Patent
Application |
20120252200 |
Kind Code |
A1 |
Sumiya; Masahiro ; et
al. |
October 4, 2012 |
PLASMA PROCESSING APPARATUS AND PLASMA PROCESSING METHOD
Abstract
A plasma processing apparatus includes a processing chamber
arranged in a vacuum vessel. A wafer placed on a sample stage in
the processing chamber is processed using a plasma formed in the
processing chamber. Before etching the film layers provided on the
wafer composed of a metal substance and an underlying oxide film or
a material having a high dielectric constant, another wafer,
provided on surface thereof a film composed of a metal of the same
kind as the metal substance, processed and particles of the metal
are deposited on an inner wall of said processing chamber.
Inventors: |
Sumiya; Masahiro; (Hikari,
JP) ; Tanaka; Motohiro; (Kudamatsu, JP) ;
Hirota; Kousa; (Kokubunji, JP) |
Assignee: |
Hitachi High-Technologies
Corporation
Tokyo
JP
|
Family ID: |
42398059 |
Appl. No.: |
13/524914 |
Filed: |
June 15, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12393254 |
Feb 26, 2009 |
8236701 |
|
|
13524914 |
|
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Current U.S.
Class: |
438/585 ;
257/E21.19 |
Current CPC
Class: |
H01L 21/31122 20130101;
H01L 21/32136 20130101; H01J 37/32972 20130101; H01J 37/32935
20130101 |
Class at
Publication: |
438/585 ;
257/E21.19 |
International
Class: |
H01L 21/28 20060101
H01L021/28 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 30, 2009 |
JP |
2009-018958 |
Claims
1-16. (canceled)
17. A plasma processing method for plasma etching a first wafer by
a plasma formed in a processing chamber, the first wafer being
provided with a film including a metal substance, and an oxide film
beneath the film including the metal substance or a film including
a high dielectric constant material beneath the film including the
metal substance, the method comprising steps of: plasma processing
a second wafer to provide a film on a surface thereof, the film
including a metal of the same kind as the metal substance; and
after plasma processing the second wafer, etching the first
wafer.
18. The plasma processing method according to claim 17, wherein
said plasma processing of said second wafer is adjusted such that,
by detecting an amount of the metal substance deposited in said
processing chamber using a light emission in said processing
chamber, the detected amount of said metal substance reaches an
amount necessary to stabilize an etching rate of the first
wafer.
19. The plasma processing method according to claim 17, wherein
said processing of said second wafer comprises: plasma processing
by using a gas equivalent to a gas used for etching said film
including the metal substance; and plasma processing by using a gas
equivalent to a gas used for etching said film including the high
dielectric constant material.
20. The plasma processing method according to claim 17, wherein
said film including said metal substance includes TiN, said
material having a high dielectric constant is HfO.sub.2 and the
HfO.sub.2 is etched using BCl.sub.3 gas.
21. A plasma processing method for plasma etching a first wafer by
a plasma formed in a processing chamber, the first wafer being
provided with a film including a metal substance, the method
comprising steps of: plasma processing a second wafer to provide a
film on a surface thereof, the film including a metal of the same
kind as the metal substance; and after plasma processing the second
wafer, etching the first wafer.
Description
INCORPORATION BY REFERENCE
[0001] The present application claims priority from Japanese
application JP-A-2009-018958 filed on Jan. 30, 2009, the content of
which is hereby incorporated by reference into this
application.
BACKGROUND OF THE INVENTION
[0002] This invention relates to a plasma processing apparatus or a
plasma processing method for processing, using a plasma formed in a
processing chamber in a vacuum vessel, a plurality of film layers
arranged on the surface of a substrate-like sample such as a
semiconductor wafer arranged in the processing chamber, or in
particular, to a plasma processing method suitable for the surface
treatment of a semiconductor substrate or the like using
plasma.
[0003] The recent fine patterning of semiconductor devices has come
to require a higher dimensional accuracy, i.e. a higher CD
(critical dimension) accuracy for the etching process to transfer a
mask formed by lithography to an underlying film. In the mass
production field, the problem is critical ho secure the CD
reproducibility in addition to high CD controllability. Generally,
the CD is changed in the etching process by the fact that the
reaction products generated from the materials to be processed are
deposited on an inner wall of the etching chamber, the fact that
the internal members of the chamber are consumed due to a long-term
use and the fact that the temperature of the internal members of
the chamber is changed, which in turn changes the sticking
probability of the radicals to the inner wall of the chamber,
resulting in a change in the plasma state having an effect on the
etching performance.
[0004] In micro transistors, the capacity of a gate insulating film
is required to be increased to control the short channel effect,
and this problem has conventionally been solved by reducing the
thickness of a gate oxide film. A decreased thickness of the gate
oxide film, however, increases leak current, and therefore,
materials having high dielectric constants (hi h-k) have been
introduced for the gate insulating film. The hafnium oxide film
(HfO.sub.2) is an example of the high-k material replacing the
oxide film. Due to the incompatibility as materials between the
polysilicon (poly-Si) electrode and hafnium oxide (HfO.sub.2),
however, the prior art requires a structure formed of a metal film
having a proper work function. Among the various metal materials
used for this purpose, TiN or La is a choice as described in
Semiconductor International, Vol. 2008/1, pp. 20-27.
[0005] In the conventional plasma processing apparatus, cleaning
operation is conducted using the plasma for each wafer or lot. For
example, plasma containing fluorine (F), chlorine (Cl) or oxygen
(O) is used mainly for the cleaning process to remove carbon (C),
oxide film, poly-Si and the nitride film. On the other hand, the
metal or the like (for example, Al), which generated by the
consumption of the inner wall materials of the etching chamber and
may be deposited on the chamber interior, is difficult to remove by
the cleaning using the plasma alone. A technique is now under
study, therefore, by which seasoning or the like process is
executed before etching the product wafer to maintain a constant
internal atmosphere of the chamber.
[0006] The method described in JP-A-2004-031308 is known as such a
conventional technique. According to the disclosure of this
conventional technique, the seasoning process is executed to
deposit a reaction product containing Si as a component on the
inner wall surface of the processing chamber of the vacuum vessel
before etching the silicon wafer in the processing chamber using
the plasma formed in the particular processing chamber. In etching
the polysilicon (poly-Si) film to form the gate of the
semiconductor device, for example, a method is disclosed in which
the silicon wafer is seasoned by forming a plasma using a HBr,
Cl.sub.2 or O.sub.2 gas or a mixture gas thereof, or the wafer
deposited with an Al film is etched with a plasma generated by a
mixed gas of SF.sub.6 and Cl.sub.2 to form an AlF film on the
surface of the quartz member in the processing chamber immediately
after wet cleaning of the processing chamber.
[0007] Also, as described in J. Vac. Sci. Technol. B24, 2191
(2060), a metal material (for example, TiN), if etched, is attached
to the inner wall of the chamber and often difficult to completely
remove by the cleaning with the plasma using the gas system
described above.
SUMMARY OF THE INVENTION
[0008] The conventional techniques described above pose a problem
as they fail to take the following points into full consideration.
Specifically, when etching the film layers formed of a metal
material and a material of high dielectric constant, the metal
substances contained in these materials may be left in the
processing chamber, and this residue is liable to change the
performance including the shape and CD value during or as the
result of the subsequent process or with an increase in the number
of wafers, thereby leading to a lower yield.
[0009] The object f this invention is to provide a plasma
processing apparatus and a plasma processing method in which the
performance variations are suppressed.
[0010] In order to achieve the object described above, according to
one aspect of the invention, there are provided a plasma processing
apparatus and a plasma processing method in which before a wafer,
having materials to be processed as a stack layer structure
consisting of a film made of a metal and a film made of a high-k
material, is processed, a wafer, having the surface thereof
consisting of a metal film of the same kind as the metal material
contained in the aforementioned layer structure, is processed. In
this way, the amount of the metal remaining in the processing
chamber is stabilized and the process variation is suppressed.
Also, the amount of metal substances remaining in the processing
chamber may be monitored and the processing conditions regulated by
monitoring the plasma emission.
[0011] More specifically, in order to achieve the object described
above, according to another aspect of the invention, there is
provided a plasma processing apparatus comprising a processing
chamber arranged in a vacuum vessel, wherein the wafer placed on a
sample stage arranged in the processing chamber processed using the
plasma formed in the processing chamber, and wherein before etching
the film layers including a film having a metal substance arranged
on the wafer and an underlying oxide film or a material having a
high dielectric constant, another wafer with the surface thereof
having a film containing a metal of the same kind as the metal
substance described above is processed so that particles or a
compound of the metal is deposited on the inner wall of the vacuum
vessel.
[0012] According to still another aspect of the invention, there is
provided a plasma processing method for processing the wafer on a
sample stage in a processing chamber in a vacuum vessel by forming
a plasma in the processing chamber, comprising a step in which
before etching the film layers including a film having a metal
substance arranged on the wafer and an underlying oxide or a
material having a high dielectric constant, another wafer with the
surface thereof having a film containing a metal of the same kind
as the metal substance described above is processed so that
particles or a compound of the metal is deposited on the inner wall
of the vacuum vessel.
[0013] Further, the object described above is achieved by
controlling the processing of another wafer based on the result of
detecting the metal substance using the light emission in the
processing chamber.
[0014] Further, the object described above is achieved by
processing the film layers of another wafer in at least two steps
using a gas equivalent to the gas used to etch the film layers of
the aforementioned wafer.
[0015] Furthermore, the object described above is achieved by
setting a time ratio of each step at not more than .+-.20% of a
time ratio for etching the film layers of the aforementioned
wafer.
[0016] Furthermore, the object described above is achieved by
processing another wafer after the wet cleaning of the interior of
the processing chamber.
[0017] In addition, the object described above is achieved by using
at least BCl.sub.3 gas to etch the metal substance containing TiN
and the HfO.sub.2 material having a high dielectric constant.
[0018] Other objects, features and advantages of the invention will
become apparent from the following description of the embodiments
of the invention taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a longitudinal sectional view of a microwave ECR
etching apparatus according to an embodiment of the invention.
[0020] FIG. 2 is a longitudinal sectional view schematically
showing the structure of the materials to be processed according
the embodiment shown in FIG. 1.
[0021] FIG. 3 is a graph showing the result of measured poly-Si
etch rate after wet processing in the case of processing the
materials to be processed which have a stack structure containing a
metal and a high-k material according to the prior art.
[0022] FIG. 4 is a graph showing the result of placing, in the
processing chamber, test samples of the same kind of material as
the inner wall of the processing chamber and of measuring the
surface of each sample using XPS (X-ray photoelectron spectroscopy)
in the case where the film layers containing a metal film 203 and
the film layers not containing the metal film 203 are
processed.
[0023] FIG. 5 is a graph showing the result of the measured etching
rate of the poly-Si film of another wafer after continuously
etching a plurality of wafers, being the etching time of the metal
film and the high-k film in the film layers on the wafer of FIG. 2
as a parameter.
[0024] FIG. 6 is a graph showing the change with time of the
emission intensity attributable to Ti in the case where the plasma
is formed using a processing gas containing BCl.sub.3 according to
the embodiment shown in FIG. 1.
[0025] FIG. 7 is a graph showing the change in the etching rates in
three cases according to the embodiment shown in FIG. 1, i.e. the
case in which the seasoning process is not executed before
processing the materials to be processed on the surface of the
product wafer 112, the case in which only the process of the TiN
etching step is executed, and the case in which the poly-Si film
203 is etched after executing the seasoning process on another
wafer having the TiN film and the high-k film, and at the same
time, judging the end point of the seasoning with the plasma
emission.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0026] Embodiments of the invention are explained below with
reference to the drawings.
Embodiments
[0027] Embodiments of the invention are explained below with
reference to FIGS. 1 to 7. FIG. 1 is a longitudinal sectional view
schematically showing configuration of the plasma processing
apparatus for processing wafers by forming a plasma using ECR
(Electron Cyclotron Resonance) with a microwave according to an
embodiment of the invention. FIG. 1 schematically shows a vacuum
vessel, a processing chamber arranged in the vacuum vessel, a
sample stage arranged in the processing chamber, electrodes, means
arranged on the outer periphery and above the vacuum vessel to
supply electric and magnetic fields and a power supply for
supplying power to these component elements. It is apparent to
those skilled in the art that any of these component parts can be
deleted or any other equipment or devices can be added in
accordance with the required performance or specification to such
an extent as not to have an extremely adverse effect on the
operation and advantages of the apparatus embodying the
invention.
[0028] In the plasma processing apparatus shown in FIG. 1, a discal
shower plate 102 (formed of, for example, quartz or yttrium having
a plurality through holes at least at the center thereof to pass
the gas) and a dielectric window 103 (of quartz, for example) to
introduce a etching gas into a cylindrical processing chamber 104
in the vacuum vessel 101 are arranged above the vacuum cylindrical
vessel 101 with an open top. The interior and exterior of these
component parts are hermetically sealed to form a ceiling and a
processing chamber 104. A gas source 105 for supplying the etching
gas communicates with the space between the shower plate 102 and
the dielectric window 103 thereby to supply the etching gas.
[0029] A vacuum exhaust system is connected to the lower part of
the vacuum vessel 101 through a vacuum exhaust port 106 facing the
bottom surface of the processing chamber 104, so that the interior
of the processing chamber 104 can be exhausted and its pressure is
reduced (not shown). In order to transmit an electric field into
the processing chamber 104 to generate the plasma in the processing
chamber 104, a waveguide 107 for propagating the electromagnetic
wave (the microwave in this embodiment) is arranged above the
dielectric window 103. The lower end portion of the waveguide 107
is coupled to a cylindrical space facing the upper surface of the
discal dielectric window 103.
[0030] The electric field propagated to the waveguide 107 (or an
antenna) is formed by the oscillation of an electric field source
109 The radio wave supplied into the processing chamber 104, though
not specifically limited by the operation or advantages of 2.45 GHz
according to this embodiment. This microwave is generated by the
electric field source 109, propagated in the waveguide 107,
transmitted from the upper surface of and through the dielectric
window 103 and the underlying shower plate 102, and introduced into
the processing chamber 104 onto a substantially circular upper
surface of an apparently cylindrical wafer mounting electrode 111
constituting a sample stage arranged in the lower part of the
processing chamber 104.
[0031] A magnetic field generating coil 110 to form a magnetic
field in the processing chamber 104 is arranged around and on the
upper outer periphery of the processing chamber 104. The electric
field generated by the electromagnetic wave source 109 and supplied
into the processing chamber 104 interacts with the magnetic field
similarly supplied into the processing chamber 104 to excite the
processing gas and generate the plasma in the processing chamber
104. As described above, the wafer mounting electrode 111 is
arranged in the lower part of the processing chamber 104 in the
vacuum vessel 101, facing to the shower plate 102. The upper
surface of the wafer mounting electrode 111 is covered with a
dielectric film (not shown) formed by spraying a dielectric
material, and a conductive film of a metal such as tungsten
arranged in the dielectric film is connected to a DC power supply
116 through a high-frequency filter 15.
[0032] Further, a discal member formed of a conductive metal such
as aluminum or titanium is disposed on the wafer mounting electrode
111, and connected with a high-frequency power supply 114 through a
matching circuit 113. Also, a spiral or concentric multiple
refrigerant path 117 is disposed in the wafer mounting electrode
111 of a metal material. This refrigerant path 117 is coupled to a
refrigerant pipe. The refrigerant pipe is coupled to both a
temperature controller 118 and a heater 119, which in turn is
connected to a heater controller 120. Also, a temperature sensor
121 is arranged on the wafer mounting electrode 111, and the signal
from the temperature sensor 121 is transmitted to the heater
controller 120 to control the output of the heater 19 and the
temperature setting of the temperature controller 118 for
controlling the temperature of the refrigerant in such a manner as
to achieve the desired temperature of the wafer 112. With this
configuration, the temperature of the refrigerant in the apparatus
and hence the wafer mounting electrode 111 are controlled.
[0033] An emission spectrometer 123 adapted to measure the light
emission in the processing chamber 104 is coupled to the outer wall
of the vacuum vessel 101 making up the processing chamber 104. The
emission spectrometer 123 is connected to an emission data
processing unit 124. The light from the plasma emitted in the
process is supplied to the emission spectrometer 123 through a
window formed of a material such as quartz formed on the side wall
of the vacuum vessel 101. In this way, the emission data is
numerically analyzed by the emission data processing unit 124.
[0034] The wafer 112 transported into the processing chamber 104 is
placed on a dielectric film on the upper surface of the wafer
mounting electrode 111 and adsorbed onto the wafer mounting
electrode 111 by the electrostatic force generated by the DC
voltage applied to the film-like internal electrode from a DC power
supply 116. Under this condition, the temperature is adjusted, and
a desired etching gas is supplied from a gas source 105 into the
processing chamber 104 through the shower plate 102. At the same
time, the gas in the processing chamber 104 is discharged from the
vacuum exhaust port 106 by the vacuum exhaust unit thereby to
control the internal pressure of the vacuum vessel 101 at a desired
value. The gas is excited by the electric and magnetic fields
supplied into the processing chamber 104, so that the plasma is
formed in the processing chamber 104. Once the plasma is formed, a
high-frequency power is applied from the high-frequency power
supply 114 connected to the wafer mounting electrode 111 and a bias
potential is formed on the upper surface of the wafer 112. Thus,
ions are attracted onto the upper surface of the wafer 112 from the
plasma thereby to start the etching process on the wafer 112.
[0035] FIG. 2 schematically shows a structure of materials to be
processed in the apparatus according to this embodiment shown in
FIG. 1. In FIG. 2, the materials to be processed form film layers
stacked on the upper surface of the wafer 112. FIG. 2 schematically
shows the shape of a part of the film layers after the process.
[0036] The film layers shown in FIG. 2 are formed of multiple or
four layers, as an example, stacked on a upper surface of the
silicon 205 of the wafer 112 forming the base. These layers form a
stack structure including a mask 201 such as a resist (PR) or a
hard mask (SiO.sub.2, SiN or SiON), an underlying poly-Si
(polysilicon) film 202, a film 203 containing a metal material (for
example, TiN, hereinafter referred to as a metal film), and a
high-k film 204 (for example, HfO.sub.2).
[0037] This film layer structure, which is to produce the gate
structure of the semiconductor device, is formed by a predetermined
process before the etching process, and unrequired portion of the
mask 201 is removed by lithography. Each of these films shown in
FIG. 2, though formed of a single layer, may alternatively be
formed of multiple layers. Especially, the metal film 203 may be
formed of multiple layers including upper and lower layers of
different materials. Also, the kind of the material, the number of
layers stacked and the thickness of the metal film 203 are varied
in the NMOS and PMOS portions in accordance with the specification
of the semiconductor device to be manufactured.
[0038] Each film stacked is processed in accordance with a
predetermined etching recipe describing the gas composition, the
supplied gas amount, the pressure and the processing time at least
a part of which is different. Also, the mask 201, simply using the
PR in the microprocessing process introduced recently, is
insufficient in thickness and etching resistance, and therefore, a
hard mask of amorphous carbon (ACL), SiN or SiON and SiO.sub.2 may
be disposed under the PR, and under and with these layers as a
mask, a poly-Si film 202 a metal film 203 may be further etched
thereunder. Here, explanation of the etching process for the mask
201 is omitted.
[0039] A mixture gas of Cl.sub.2 and fluorine (F)-containing gas
(CF.sub.4, for example) or a mixture gas of Cl.sub.2 and HBr is
used as an etching gas for the poly-Si film 202. If required,
O.sub.2 gas may be also used.
[0040] Next, in the first step of etching the metal film 203 (for
example, TiN), the wafer bias is increased to a relatively high
value and thus the ion energy is increased to remove a naturally
oxidized film formed in the boundary of the metal film 203 (the
boundary surface formed between the surfaces of the materials of
the upper and lower films, which may include a single layer or
about several atomic layers of other materials). HBr or Ar, which
is generally used as the processing gas in this process, may be
replaced with a gas of another system.
[0041] After removing the naturally oxidized film, the Cl.sub.2 gas
or a mixture gas of Cl.sub.2 and HBr is mainly supplied as a
processing gas to etch the metal film 203. According to this
embodiment, the metal film 203, which is small in thickness as
compared with other films, is etched by adjusting the wafer bias
value via the power from the high-frequency power supply 114 to
maintain the ion energy at a comparatively low level.
[0042] Next, the BCl.sub.3 gas or the mixture gas of BCl.sub.3 and
Cl.sub.2 is used for etching the high-k film (for example,
HfO.sub.2) formed of a material of a high dielectric constant. In
this step, a satisfactory etching characteristic (shape,
selectivity) can be achieved by using a relatively low ion
energy.
[0043] In the prior art, once the number of etched wafers reached a
predetermined number, the interior of the processing chamber 104 is
subjected to cleaning such as wet cleaning, followed by the process
of familiarizing the interior of the processing chamber 104 by
etching a non-metal wafer such as a Si, PR or oxide film wafer to
season the surface of the internal members of the processing
chamber 104, only after which the wafers are processed as a
product. FIG. 3 is a graph showing the result of measuring the
poly-Si etch rate after wet cleaning in the case where a plurality
of wafers provided thereon with the materials processed having a
metal/high-k stack structure were processed according to the prior
art.
[0044] According to this prior art, the etching rate is changed
with the increase in the number of wafers processed. Especially,
the etching rate is sharply increased very early in the initial
period of the process, after which the etching rate is settled. For
this reason, a great shape difference occurs between the product
wafer etched immediately after the cleaning and a subsequent
product wafer processed after a predetermined number of wafers
processed in stable state.
[0045] To find the cause of this difference, the present inventors
placed two test samples of the same kind of material as the inner
wall of the processing chamber, one having layers containing the
metal film 203 and the other having the layers not containing the
metal film 203, in the processing chamber, processed the respective
test samples, and measured the surfaces of the respective samples
using XPS (X-ray photoelectron spectroscopy). As a result, as shown
in the graph of FIG. 4, Ti was detected from the sample of which
the layers containing the metal film 203 were processed. Further,
an increased amount of fluorine (F) was detected from the sample of
which the layers containing the metal film 203 were processed.
[0046] FIG. 5 is a graph showing the result measuring, after
etching a plurality of wafers (about ten wafers in the case under
consideration) continuously, the etch rate of the poly-Si film 202
of another wafer 112 in the layers shown in FIG. 2, with a ratio of
the etching time of the metal film 203 and that of the high-k film
204 as a parameter. In FIG. 5, the dotted line indicates the etch
rate of the poly-Si film 202 settled after the wafer 112 is
processed for a long time.
[0047] As shown in FIG. 5, the shorter the etching time of the
high-k film 204, the higher the etching rate, and vice versa. Also,
the etching rate is saturated after the lapse of a certain etching
time of the high-k film 204. According to this embodiment, TiN is
etched as a material of the metal film 203 using the processing gas
containing HBr/Cl.sub.2. Further, the processing gas containing
BCl.sub.3/Cl.sub.2 is used for etching the high-k film 204. After
processing the layers, a Si wafer is placed on the electrode and
exposed to the Ar discharge, after which the surface of the Si
wafer was measured by TRXF (Total reflection X-ray fluorescence).
The amount of Ti detected in each case is plotted along the right
axis.
[0048] According to this embodiment, the metal material Ti detected
is considered to be attributed to the fact that the Ti or the Ti
compound left as particles in the processing chamber 104 is
scattered and deposited on the wafer 112 by sputtering of Ar. Thus,
it is considered to indicate the amount Ti left in the processing
chamber 104. Therefore, the etch rate of the poly-Si film 202 is
considered to be elated with the amount of Ti remaining in the
processing chamber 104.
[0049] Further, as shown also in FIG. 4, the amount of F is also
increased as the result of Ti remaining in the processing chamber
104. To investigate the cause of this phenomenon, detailed
examination of the XPS measurement result (not shown) indicates
that he peak of Ti--O bond as well as the peak of Ti--F bond is
observed at the Ti2p peak and an energy shift toward a low binding
energy is seen for the peak of F1s. Therefore, is considered to be
coupled with some metal, and in this case, the present inventors
considered that the Ti--F bond exists. This can also explain the
phenomenon that the substance making up the inner wall surface of
the processing chamber 104 is fluorized by Ti remaining in the
processing chamber 104 and F in the plasma is increased, result ng
in an increased rate at which the poly-Si film is processed.
[0050] Generally, the Ti--F and Ti--O bonds are stable and
considered difficult to remove with the cleaning using the plasma
as in the prior art. In view of this, according to his embodiment,
before processing the materials to be processed to obtain the
product wafer 112, the seasoning process is carried out by
processing a wafer having on the surface thereof the same substance
as the material of the metal (for example, TiN) film 203 contained
in the materials to be processed, thereby depositing the same metal
substance (for example, Ti) on the interior of the processing
chamber 104. As a result, the composition of the gas being
processed in the processing chamber 104 can be stabilized. This
preliminary cleaning according to the present embodiment is
conducted after wet cleaning of the surface of the materials in the
processing chamber 104 before processing the product wafer 112.
[0051] The seasoning process according to this embodiment may use a
plurality of wafers 112 with TiN formed on the surface thereof. In
other words, the seasoning process may be conducted repeatedly in
advance. In the process, a plurality of wafers having different
film layers may be continuously processed. The amount of the metal
substance (Ti) remaining in the processing chamber 104 can be
detected by generating the plasma on or without the wafer 112 used
for seasoning and by using the light emission of the plasma. With
reference to FIG. 6, the detection of this metal substance is
explained.
[0052] FIG. 6 is a graph showing a change in the emission intensity
with time attributable to Ti in the case where the plasma is
generated using the processing gas containing BCl.sub.3 according
to the embodiment shown in FIG. 1. According to this embodiment,
the emission intensity is analyzed using the light emission data
processing unit 124. Especially, the arithmetic unit placed in the
light emission data processing unit 124 reads the light emission
data which is stored in a storage unit placed in the light emission
data processing unit 124 and which is detected during the etching
process of the wafer 112 provided with the metal substance on the
surface thereof, and performs a specific arithmetic operation
including a process of integration of the data on the emitted light
of the wavelength corresponding to a predetermined metal substance.
In this way, a value indicating the amount of Ti remaining in the
processing chamber 104 is calculated and output as a signal thereby
to detect the Ti amount.
[0053] As described above, with the increase in the amount of Ti
deposited on the inner surface of the processing chamber 104 or
left in the processing chamber 104 by processing the wafer 112, the
rate at which the wafer 112 having the materials to be processed is
subsequently etched undergoes a change. Once the amount of Ti
exceeds a particular value, the saturated state is reached, in
which the processing rate approaches a predetermined value To
determine the Ti amount associated with the saturated state, the
data on the light emission from the interior of the processing
chamber 104 is firstly acquired and analyzed in the case where the
wafer 112 is etched with the surface film containing the metal
substance for so long time as to reach the saturated state, and
this emission intensity is compared with the emission intensity
acquired at e preliminary etching of the wafer with the surface
film containing the metal substance (Ti) conducted immediately
after the wet cleaning, thereby to detect the end point of the
seasoning process conducted until the etching rate is saturated. In
place of the gas system containing BCl.sub.3 used in this
embodiment, the measurement can be conducted using a gas system
using a rare gas such as Ar.
[0054] FIG. 7 is a graph showing changes in the etching rate in
three cases according to the embodiment shown in FIG. 1, i.e. the
case in which the seasoning process is not executed before
processing the materials to be processed on the surface of the
product wafer 112, the case in which only the process of the TiN
etching step is executed using the wafer provided with the TiN film
on the surface thereof, and the case in which the poly-Si film 203
is etched after executing the seasoning process in the etching step
of the TiN film and the high-k film using a wafer having the TiN
film and the high-k film on the surface thereof and judging the end
of the seasoning with the plasma emission. In the case where the
TiN and high-k process is executed, its rate variation is smallest
among the three cases described above and the process is executed
in a stable manner. As explained above, the high-k etching step
uses the processing gas containing BCl.sub.3 as a component, and in
the process using this gas, the Ti remaining in the processing
chamber 104 is removed by BCl.sub.3.
[0055] This indicates that in order to adjust the amount of Ti
remaining in the processing chamber 104, it is important to adjust
the time ratio between the TiN film etching step and the high-k
film etching step or the discharge condition in the preliminary
seasoning process, based on the signal obtained from the result of
detecting the plasma emission. In this way, the amount of the metal
substance (Ti) remaining or deposited in the processing chamber 104
can be controlled to the desired amount by the preliminary
seasoning process.
[0056] In controlling the amount of Ti left in the processing
chamber 104, the process is executed at the time ratio of the
etching process of the TiN film/high-k film during the Ti seasoning
within 20% or equal to the time ratio between the process of the
high-k film 204 and the process of the metal film 203 in the
etching of the wafer 112 having the materials to be processed and
having the aforementioned film layer structure. In this way, the
distribution of Ti remnants accumulated in the processing chamber
104 during the seasoning can be made equivalent to the value for
actual processing of the materials to be processed. This is also
achieved by making the film configuration on the wafer surface in
the preliminary seasoning process equivalent to that of the
materials to be processed including the metal film 203 on the one
hand, and by making the emission in y of the metal substance from
the plasma in the processing chamber 104 in the TiN/high-k process
during the seasoning, equal to the emission intensity of the plasma
obtained with the stable processing conditions such as the etching
rate, especially at the time of processing the product wafer 112
having the materials to be processed on the other hand.
Furthermore, a similar purpose can be attained by setting the
condition of the process including the composition of the
processing gas used for the film processing in the preliminary
seasoning process, equal or substantially equal to the condition
for the process of the wafer 112 having the materials to be
processed.
[0057] The preliminary seasoning process described above is
configured of two or more steps. By executing this process, the
amount or the distribution of Ti remaining in the processing
chamber 104 can be controlled with high accuracy for an improved
process stability.
[0058] As described above, according to this embodiment, before
processing the materials to be processed having the stack structure
of the metal film 203 and the high-k film 204, another wafer,
having on the surface thereof a film containing the metal substance
of the same kind as the material of the metal film 203 contained in
the materials to processed is processed, and the film is etched.
Further, the amount of the metal substance remaining in the
processing chamber 104 is detected by monitoring the light emission
in the processing chamber, or by adjusting the processing condition
by use of the detection result, the residual amount of the metal
substance in the processing chamber 104 is stabilized and the
resulting change in shape obtained by processing can suppressed. In
this way, the stability of the CD value after the process can be
improved. Thus, the apparatus or the method for the etching process
suppressing the process yield reduction and having a smaller
secular variation can be provided.
[0059] Also, since the amount of the metal substance remaining in
the processing chamber 104 is stabilized, the process variation
which otherwise might be caused by the metal substance is
suppressed, thereby making it possible to suppress the CD
variation.
[0060] According to the embodiments described above, the ECR plasma
equipment is described especially. Nevertheless, this invention is
applicable with equal effect by using other plasma generating
apparatuses or methods such as the inductively-coupled plasma (ICP)
or the capacitance-coupled plasma (CCP).
[0061] It should be further understood by those skilled in the art
that although the foregoing description has been made on
embodiments of the invention, the invention is not limited thereto
and various changes and modifications may be made without departing
from the spirit of the invention and the scope of the appended
claims.
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