U.S. patent application number 10/509656 was filed with the patent office on 2005-04-28 for processor.
This patent application is currently assigned to Tokyo Electron Limited. Invention is credited to Goto, Toshio, Hori, Masaru, Ishii, Nobuo.
Application Number | 20050087296 10/509656 |
Document ID | / |
Family ID | 33045140 |
Filed Date | 2005-04-28 |
United States Patent
Application |
20050087296 |
Kind Code |
A1 |
Goto, Toshio ; et
al. |
April 28, 2005 |
Processor
Abstract
A processing apparatus includes a vessel (1) which accommodates
a target object (W), ultraviolet light-generating means (41) for
outputting ultraviolet light (UV) toward an atmosphere (P)
containing radicals in the vessel (1), ultraviolet light-receiving
means (42) for receiving the ultraviolet light (UV) passing through
the atmosphere (P), and analysis control means (43, 44) for
obtaining a density of the radicals in the atmosphere (P) on the
basis of an output signal from the ultraviolet light-receiving
means (42), to control a process parameter. The density of the
radicals can be held at a constant level, and process
reproducibility can be improved.
Inventors: |
Goto, Toshio; (Nisshin-shi,
JP) ; Hori, Masaru; (Nisshin-shi, JP) ; Ishii,
Nobuo; (Amagasaki-shi, JP) |
Correspondence
Address: |
CROWELL & MORING LLP
INTELLECTUAL PROPERTY GROUP
P.O. BOX 14300
WASHINGTON
DC
20044-4300
US
|
Assignee: |
Tokyo Electron Limited
3-6, Akasaka 5-chome Minato-ku
Tokyo
JP
|
Family ID: |
33045140 |
Appl. No.: |
10/509656 |
Filed: |
September 29, 2004 |
PCT Filed: |
March 26, 2003 |
PCT NO: |
PCT/JP03/03714 |
Current U.S.
Class: |
156/345.24 |
Current CPC
Class: |
C23C 16/482 20130101;
H01J 37/32935 20130101; H01L 21/67253 20130101 |
Class at
Publication: |
156/345.24 |
International
Class: |
C23F 001/00 |
Claims
1. A processing apparatus characterized by comprising: a vessel
which accommodates a target object; ultraviolet light-generating
means for outputting ultraviolet light or vacuum ultraviolet light
toward an atmosphere containing radicals in said vessel;
ultraviolet light-receiving means for receiving the ultraviolet
light or vacuum ultraviolet light passing through the atmosphere;
and analysis control means for obtaining a density of the radicals
in the atmosphere on the basis of an output signal from said
ultraviolet light-receiving means, to control a process
parameter.
2. A processing apparatus according to claim 1, characterized in
that said analysis control means obtains an attenuation amount of
the ultraviolet light or vacuum ultraviolet light passing through
the atmosphere on the basis of the output signal from said
ultraviolet light-receiving means, and obtains the density of the
radicals in the atmosphere from the attenuation amount.
3. A processing apparatus according to claim 1, characterized by
comprising: means for intermittently outputting the ultraviolet
light or vacuum ultraviolet light toward the atmosphere and
outputting an ultraviolet light presence/absence signal indicating
presence/absence of the ultraviolet light or vacuum ultraviolet
light; and means for obtaining a difference calculated by
subtracting a light reception amount of said ultraviolet
light-receiving means obtained when the ultraviolet light or vacuum
ultraviolet light is absent from a light reception amount of said
ultraviolet light-receiving means obtained when the ultraviolet
light or vacuum ultraviolet light is present on the basis of the
ultraviolet light presence/absence signal, and obtaining the
density of the radicals in the atmosphere from the difference.
4. A processing apparatus according to claim 1, characterized by
comprising means for causing the ultraviolet light or vacuum
ultraviolet light output from said ultraviolet light-generating
means to pass through a plurality of optical paths and to be
received by said ultraviolet light-receiving means.
5. A processing apparatus according to claim 4, characterized by
comprising modulators arranged to said optical paths respectively
and having modulation frequencies that are different from each
other.
6. A processing apparatus according to claim 1, characterized in
that said vessel has a window through which the ultraviolet light
passes, and said window is heated.
7. A processing apparatus according to claim 1, characterized in
that said vessel has a window through which the ultraviolet light
passes, and said window has a cylindrical structure.
8. A processing apparatus according to claim 1, characterized by
comprising: temperature measuring means for measuring a temperature
of molecular or atomic radicals in the atmosphere, and said
analysis control means controls the process parameter on the basis
of the output signal from said ultraviolet light-receiving means
and a measurement result of said temperature measuring means.
9. A processing apparatus according to claim 8, characterized in
that said temperature control means includes laser beam generating
means for generating a laser beam toward the atmosphere, laser beam
receiving means for receiving the laser beam passing through the
atmosphere; and analysis means for obtaining an attenuation amount
spectrum of the laser beam passing through the atmosphere on the
basis of an output signal from said laser beam receiving means, and
obtaining a temperature of molecular or atomic radicals in the
atmosphere from a pattern of the attenuation amount spectrum.
10. A processing apparatus according to claim 9, characterized by
comprising: means for intermittently outputting the laser beam
toward the atmosphere and outputting a laser beam presence/absence
signal indicating presence/absence of the laser beam; and means for
obtaining a spectrum of a difference calculated by subtracting a
light reception amount of said laser beam receiving means obtained
when the laser ultraviolet beam is absent from a light reception
amount of said laser beam receiving means obtained when the laser
beam is present on the basis of the laser beam presence/absence
signal, and obtaining a temperature of the molecular or atomic
radicals in the atmosphere from a pattern of the spectrum.
11. A processing apparatus according to claim 8, characterized in
that said temperature measuring means measures a light emission
spectrum of the molecular or atomic radicals in the atmosphere, and
obtains a temperature of the molecular or atomic radicals in the
atmosphere from an obtained spectrum pattern.
12. A processing apparatus according to claim 9, characterized by
comprising means for causing the laser beam output from said laser
beam generating means to pass through a plurality of optical paths,
and to be received by said laser beam means.
13. A processing apparatus according to claim 12, characterized by
comprising modulators arranged to said optical paths respectively
and having modulation frequencies that are different from each
other.
14. A processing apparatus according to claim 9, characterized in
that said vessel has a window through which the laser beam passes,
and said window is heated.
15. A processing apparatus according to claim 9, characterized in
that said vessel has a window through which the laser beam passes,
and said window has a cylindrical structure.
16. A processing apparatus according to claim 1, characterized in
that the radicals are atomic radicals.
17. A processing apparatus according to claim 16, characterized in
that the atomic radicals include any one element selected from Si,
N, O, F, H, and C.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a processing apparatus for
performing processes in an Si-containing atmosphere.
[0002] In the manufacture of a semiconductor device, flat panel
display, and organic EL (electro luminescent panel) display, plasma
processing apparatuses are widely used to perform processes such as
formation of an insulating film, e.g., an oxide film, crystal
growth of a semiconductor layer, etching, and ashing. A
high-frequency plasma CVD apparatus will be described as a prior
art example of the plasma processing apparatus. FIG. 6 is a diagram
showing the arrangement of the main part of a conventional
high-frequency plasma CVD (Chemical Vapor Deposition)
apparatus.
[0003] The CVD apparatus shown in FIG. 6 includes a process chamber
101 and a plasma source which generates plasma P with high
frequency. The chamber 101 accommodates a susceptor 102 for placing
a substrate W thereon. The susceptor 102 incorporates a heater 103
which heats the substrate W to a predetermined temperature. An
exhaust port 104 is formed in the lower portion of the chamber 101.
The chamber 101 is evacuated by a vacuum pump (not shown)
communicating with the exhaust port 104.
[0004] The plasma source includes an antenna 121 which supplies
high frequency into the chamber 101, and a gas introducing nozzle
111 which introduces source gases into the chamber 101. The antenna
121 is arranged in the upper space in the chamber 101 to oppose the
susceptor 102, and is connected to a high-frequency power supply
(not shown) through a high-frequency waveguide 124.
[0005] When an Si (silicon) thin film is to be formed on the
substrate W, the interior of the chamber 101 is evacuated, and the
substrate W is heated by the susceptor 102 to about 400.degree. C.
Then, as source gases, SiH.sub.4 and SiF.sub.4 are introduced
through the gas introducing nozzle 111. When high frequency is
supplied from the antenna 121, SiH.sub.4 and SiF.sub.4 dissociate
to form SiH.sub.x and SiF.sub.x (x=1, 2, and 3) radicals. The
radicals react on the surface of the substrate W to form an Si thin
film (this is described in, e.g., "The 62nd Symposium of the
Society of Applied Physics, Digest 14a-ZF-3", September 2001,
p.736).
[0006] In this manner, radicals are directly concerned in thin film
formation using a plasma. This also applies to a process such as
etching or ashing.
[0007] When the same process is performed with one plasma
processing apparatus under the same conditions, however, each time
the process is performed, the plasma state changes, and the process
reproducibility is poor. When the same process is performed with
different apparatuses under the same conditions, the plasma state
differs among the apparatuses, and it is difficult to perform the
process with good reproducibility. Consequently, individual
substrates W cannot be processed uniformly.
SUMMARY OF THE INVENTION
[0008] The present invention has been made to solve the above
problems, and ahs as its object to improve the process
reproducibility.
[0009] According to the findings of the inventor of the present
invention, when a process is to be performed in an Si-containing
atmosphere, to monitor Si is effective in realizing the process
with good reproducibility. In particular, Si has an absorption
spectrum in an ultraviolet region, and can be measured highly
sensitively with a simple method. The present invention has been
made based on these findings.
[0010] More specifically, the characteristic feature of a
processing apparatus according to the present invention resides in
comprising a vessel which accommodates a target object, ultraviolet
light-generating means for outputting ultraviolet light or vacuum
ultraviolet light toward an atmosphere containing radicals in the
vessel, ultraviolet light-receiving means for receiving the
ultraviolet light or vacuum ultraviolet light passing through the
atmosphere, and analysis control means for obtaining a density of
the radicals in the atmosphere on the basis of an output signal
from the ultraviolet light-receiving means, to control a process
parameter.
[0011] The analysis control means may obtain an attenuation amount
of the ultraviolet light or vacuum ultraviolet light passing
through the atmosphere on the basis of the output signal from the
ultraviolet light-receiving means, and obtain the density of the
radicals in the atmosphere from the attenuation amount.
[0012] The processing apparatus described above may further
comprise means for intermittently outputting the ultraviolet light
or Vacuum ultraviolet light toward the atmosphere and outputting an
ultraviolet light presence/absence signal indicating
presence/absence of the ultraviolet light or vacuum ultraviolet
light, and means for obtaining a difference calculated by
subtracting a light reception amount of the ultraviolet
light-receiving means obtained when the ultraviolet light or vacuum
ultraviolet light is absent from a light reception amount of the
ultraviolet light-receiving means obtained when the ultraviolet
light or vacuum ultraviolet light is present on the basis of the
ultraviolet light presence/absence signal, and obtaining the
density of the radicals in the atmosphere from the difference.
[0013] The processing apparatus described above may have means for
causing the ultraviolet light or vacuum ultraviolet light output
from the ultraviolet light-generating means to pass through a
plurality of optical paths and to be received by the ultraviolet
light-receiving means. Modulators having modulation frequencies
that are different from each other may be arranged to the optical
paths respectively.
[0014] In the processing apparatus described above, the vessel may
have a window through which the ultraviolet light passes, and the
window may be heated. Alternatively, the window may have a
cylindrical structure.
[0015] The processing apparatus described above may further
comprise temperature measuring means for measuring a temperature of
molecular or atomic radicals in the atmosphere, and the analysis
control means may control the process parameter on the basis of the
output signal from the ultraviolet light-receiving means and a
measurement result of the temperature measuring means.
[0016] The temperature measuring means may include laser beam
generating means for generating a laser beam toward the atmosphere,
laser beam receiving means for receiving the laser beam passing
through the atmosphere, and analysis means for obtaining an
attenuation amount spectrum of the laser beam passing through the
atmosphere on the basis of an output signal from the laser beam
receiving means, and obtaining a temperature of molecular or atomic
radicals in the atmosphere from a pattern of the attenuation amount
spectrum. Also, the temperature measuring means may further include
means for intermittently outputting the laser beam toward the
atmosphere and outputting a laser beam presence/absence signal
indicating presence/absence of the laser beam, and means for
obtaining a spectrum of a difference calculated by subtracting a
light reception amount of the laser beam receiving means obtained
when the laser ultraviolet beam is absent from a light reception
amount of the laser beam receiving means obtained when the laser
beam is present on the basis of the laser beam presence/absence
signal,; and obtaining a temperature of the molecular or atomic
radicals in the atmosphere from a pattern of the spectrum.
[0017] Alternatively, the temperature measuring means may measure a
light emission spectrum of the molecular or atomic radicals in the
atmosphere, and may obtain a temperature of the molecular or atomic
radicals in the atmosphere from an obtained spectrum pattern.
[0018] The processing apparatus described above may have means for
causing the laser beam output from the laser beam generating means
to pass through a plurality of optical paths, and to be received by
the laser beam means. Modulators having modulation frequencies that
are different from each other may be arranged to the optical paths
respectively.
[0019] In the processing apparatus described above, the vessel may
have a window through which the laser beam passes, and the window
may be heated. Alternatively, the window may have a cylindrical
structure.
[0020] In processing apparatus described above, the radicals may be
atomic radicals, and may include any one element selected from Si,
N, O, F, H, and C.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a diagram showing the arrangement of a
high-frequency plasma CVD apparatus according to the first
embodiment of the present invention;
[0022] FIG. 2 is a diagram showing the arrangement of a
high-frequency plasma CVD apparatus according to the second
embodiment of the present invention;
[0023] FIG. 3 is a diagram for explaining an example of a
high-frequency plasma CVD apparatus according to the third
embodiment of the present invention;
[0024] FIG. 4 is a diagram for explaining another example of the
high-frequency plasma CVD apparatus according to the third
embodiment of the present invention;
[0025] FIGS. 5A to 5C are graphs for explaining an example of
two-dimensional parameter control; and
[0026] FIG. 6 is a diagram showing the arrangement of the main part
of a conventional high-frequency plasma CVD apparatus.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] The embodiments of the present invention will be described
in detail with reference to the accompanying drawings. Embodiments
in which the present invention is applied to high-frequency plasma
CVD apparatuses which form an Si thin film will be described.
First Embodiment
[0028] FIG. 1 is a diagram showing the arrangement of a
high-frequency plasma CVD apparatus according to the first
embodiment of the present invention. A process chamber 1 serving as
a processing vessel accommodates a susceptor 2 for placing thereon
a glass substrate W as a target object. An electrostatic chuck or
mechanical chuck (not shown) to bring the glass substrate W into
tight contact with the susceptor 2 is prepared for the susceptor 2.
The susceptor 2 incorporates a heater 3 for heating the glass
substrate W to a predetermined temperature. The temperature of the
heater 3 is changed in accordance with a control signal S5 output
from a controller 44 (to be described later). An exhaust port 4 is
formed in the lower portion of the chamber 1, and is connected to a
vacuum pump 4A. The vacuum pump 4A adjusts the pressure in the
chamber 1 in accordance with a control signal S6 output from the
controller 44.
[0029] A gas introducing nozzle 11 is arranged in the upper portion
of the chamber 1. The nozzle 11 is connected to a gas introducing
pipe 13 through a valve 12. The gas introducing pipe 13 is
connected to gas supply sources 16A, 16B, and 16C through valves
14A, 14B, and 14C and mass flow controllers (MFCs) 15A, 15B, and
15C, respectively. The gas supply sources 16A to 16C respectively
supply SiH.sub.4, H.sub.3, and SiF.sub.4 as source gases. The MFCs
15A to 15C respectively adjust the flow rates of the source gases
in accordance with control signals S1 to S3 output from the
controller 44.
[0030] A disk antenna 21 is arranged in the upper space in the
chamber 1 to oppose the susceptor 2. A round ground plate 23 is
arranged on the disk antenna 21 through a quartz plate 22. The disk
antenna 21 and ground plate 23 are connected to the inner and outer
conductors, respectively, of a coaxial waveguide 24. The coaxial
waveguide 24 is connected to a high-frequency power supply 26
through a rectangular waveguide 25. The output power of the
high-frequency power supply 26 is changed in accordance with a
control signal S4 output from the controller 44. The rectangular
waveguide 25 or coaxial waveguide 24 is provided with a load
matching unit 27.
[0031] The CVD apparatus further includes a radical density
measuring means employing absorption spectroscopy. Absorption
spectroscopy is a method of measuring the absolute density of atoms
or molecules with a predetermined level contained in a plasma on
the basis of the attenuation amount of light passing through the
plasma by utilizing the fact that the light absorption wavelength
changes depending on the level of the atoms or molecules. With this
method, the density of Si radicals can be measured easily at high
sensitivity.
[0032] The radical density measuring means according to this
embodiment includes a hollow cathorde lamp (HCL) 41 arranged
outside the chamber 1, an input light guide 41A for connecting the
hollow cathode lamp 41 and chamber 1, a chopper (modulator) 45
provided to the input light guide 41A, an ultraviolet
light-receiving section 42 arranged outside the chamber 1, an
output light guide 42A for connecting the ultraviolet
light-receiving section 42 and chamber, and a radical density
calculating section 43 electrically connected to the output of the
ultraviolet light-receiving section 42.
[0033] The input light guide 41A and output light guide 42A are
arranged on one straight line intersecting the central axis of the
chamber 1. The heights of the input light guide 41A and output
light guide 42A are set in accordance with the height of a plasma P
generated between the disk antenna 21 and susceptor 2.
[0034] The hollow cathode lamp 41 operates as an ultraviolet
light-generating section which outputs ultraviolet light UV having
Si radical absorption wavelengths of 288.2 nm and 251.6 nm. In the
plasma, the two wavelengths can be utilized. In a process of
extracting Si radicals generated by the plasma, however, only 251.6
nm can be utilized. The former case also has a better sensitivity
with 251.6 nm. A ring dye laser oscillator may be used in place of
the hollow cathode lamp 41.
[0035] The chopper 45 pulse-modulates the ultraviolet light UV
output from the hollow cathode lamp 41. The chopper 45 outputs to
the ultraviolet light-receiving section 42 a trigger signal
(ultraviolet light present/absent signal) S10 synchronized with the
ON/OFF operation of the pulse-modulated ultraviolet light UV.
[0036] The ultraviolet light-receiving section 42 receives the
ultraviolet light UV output from the chamber 1. The ultraviolet
light-receiving section 42 discriminates light received when the
ultraviolet light UV is present (ON state) and light received when
the ultraviolet light UV is absent (OFF state) from each other on
the basis of the trigger signal S10 input from the chopper 45. The
ultraviolet light-receiving section 42 calculates the difference
obtained by subtracting the light reception amount obtained when
the ultraviolet light UV is absent from the light reception amount
obtained when the ultraviolet light UV is present, and outputs the
resultant value to the radical density calculating section 43.
While the process gas is not introduced and the plasma P is not
generated, the light reception amount of the ultraviolet light UV
is measured in advance and set in the radical density calculating
section 43, prior to the process, as the light emission amount of
the ultraviolet light UV.
[0037] The radical density calculating section 43 calculates the
attenuation amount of the ultraviolet light UV-passing through the
plasma on the basis of the light emission amount of the ultraviolet
light UV input in advance and the output signal from the
ultraviolet light-receiving section 42, to calculate the density of
the Si radicals contained in the plasma P from the attenuation
amount, and outputs the calculated density to the controller
44.
[0038] The controller 44 controls parameters for plasma generation
so that the radical density calculated by the radical density
calculating section 43 becomes close to a preset value. More
specifically, the controller 44 outputs the control signal S6 to
the vacuum pump 4A to control the gas pressure in the chamber 1.
The controller 44 also outputs the control signals Si to S3 to the
MFCs 15A to 15C, respectively, to control the adjustment of their
flow rates. The controller 44 outputs the control signal S4 to the
high-frequency power supply 26 to control the output power. The
controller 44 also outputs the control signal 5 to the power supply
of the heater 3 to control the temperature of the heater 3, thus
adjusting the temperature of the susceptor 2.
[0039] The radical density calculating section 43 and controller 44
form an analysis control means. The analysis control means includes
a computer and has an arithmetic processing unit, storage,
operation unit, and input/output interface unit. The storage stores
measurement data, data necessary for calculating the radical
density, and a control program. The arithmetic processing unit
calculates the radical density in accordance with the control
program, and controls the operation of the entire apparatus as will
be described later. Data can be input from the operation unit. When
the input/output interface unit is connected to another management
system or the like, the analysis control means can communicate with
it.
[0040] The control reference value may be set outside the
apparatus, or may be acquired by the apparatus itself. When the
control reference value is to be set outside the apparatus, for
example, it is set from the operation unit by the operator, or from
a central control unit via the input/output interface unit. When
the control reference value is to be acquired by the apparatus
itself, for example, a value obtained after the lapse of a specific
period of time since the start of the process is set as the
reference value. If there is a preprocess, the value obtained in
the preprocess is set as the reference value.
[0041] Ultraviolet light transmission windows 5A and 5B made of
quartz are respectively formed at the distal ends of the light
guides 41A and 42A, that is, the boundary of the interiors of the
input light guide 41A and chamber 1 and that of the interiors of
the output light guide 42A and chamber 1. If a pollutant that
absorbs the ultraviolet light UV attaches to the transmission
windows 5A and 5B, an error occurs in the measurement result of the
radical density. In order to prevent this, the transmission windows
5A and 5B may be heated to a high temperature of about 200.degree.
C. to 400.degree. C., so the pollutant may not attach to them
easily. Alternatively, the transmission windows 5A and 5B may be
formed of capillary plates each having a cylindrical structure with
an aspect ratio of 3 or more. The capillary plates may have
bottoms.
[0042] The operation of the plasma processing apparatus according
to this embodiment will be described.
[0043] The glass substrate W is arranged on the susceptor 2 and is
brought into tight contact with it by an electrostatic chuck or the
like. The substrate temperature is set to 400.degree. C. with the
heater 3. The interior of the chamber 1 is evacuated with the
vacuum pump 4A. Source gases are introduced into the chamber 1 from
the nozzle 11 with flow rates of
SiH.sub.4/H.sub.2/SiF.sub.4=5/200/30 sccm (standard cubic
centimeter/minute) to maintain the pressure in the chamber 1 at 1.5
Pa. In this state, a high frequency with power of 800 W is supplied
into the chamber 1. Then, SiH.sub.4 and SiF.sub.4 dissociate to
form SiH.sub.x and SiF.sub.x (x=1, 2, and 3) radicals. These
radicals react on the surface of the substrate W to deposit Si.
[0044] When performing this process, the density of the Si radicals
contained in the plasma (atmosphere) P is measured. First, the
hollow cathode lamp 41 outputs ultraviolet light UV having
wavelengths of 288.2 nm and 251.6 nm. The chopper 45
pulse-modulates the ultraviolet light UV and outputs it
intermittently toward the plasma P in the chamber 1. The
ultraviolet light UV passes through the chamber 1 horizontally in
the direction of diameter. When the ultraviolet light UV having the
wavelengths of 288.2 nm and 251.6 nm pass through the plasma P, it
is partly absorbed by the Si radicals contained in the plasma P and
reaches the ultraviolet light-receiving section 42.
[0045] The ultraviolet light-receiving section 42 discriminates,
from the trigger signal S10 based on the ON/OFF states of the
ultraviolet light UV input from the chopper 45, light received when
the ultraviolet light UV is present (ON state) and light received
when the ultraviolet light UV is absent (OFF state) from each
other, and calculates a difference obtained by subtracting the
light reception amount obtained when the ultraviolet light UV is
absent from the light reception amount obtained when it is present.
Thus, background light, e.g., light emitted by the plasma P itself,
which is not pertinent to the ultraviolet light UV is removed, and
the light reception amount of the ultraviolet light UV can be
obtained.
[0046] The radical density calculating section 43 obtains the
attenuation amount of the ultraviolet light UV on the basis of the
light emission amount of the ultraviolet light UV input in advance
and the output signal from the ultraviolet light-receiving section
42, and calculates the density of the Si radicals from the
attenuation amount. The controller 44 controls the parameters for
plasma generation so that the obtained radical density becomes
close to the preset value.
[0047] Alternatively, the trigger signal S10 may be supplied to the
radical density calculating section 43, and the radical density
calculating section 43 may perform arithmetic processing to remove
the influence of the background light on the ultraviolet light
UV.
[0048] In this CVD apparatus, plasma generation is controlled by
adjusting the gas pressure, the gas mixing ratio, the flow rate of
the entire gas mixture, and the high-frequency power, and
temperature of the susceptor 2.
[0049] When the gas pressure is to be adjusted, the control signal
S6 to be supplied to the vacuum pump 4A is controlled. When the
radical density is high, the gas pressure is increased. When the
radical density is low, the gas pressure is decreased.
[0050] When the gas mixing ratio and the flow rate of the entire
gas mixture are to be adjusted, the control signals S1 to S3 to be
output to the MFCs 15A to 15C are controlled to adjust the flow
rates of SiH.sub.4, H.sub.2, and SiF.sub.4. When the radical
density is high, the mixing ratio of SiH.sub.4 to SiF.sub.4 is
decreased, or the entire flow rate is decreased. When the radical
density is low, the mixing ratio of SiH.sub.4 to SiF.sub.4 is
increased, or the entire flow rate is increased.
[0051] When the high-frequency power is to be adjusted, the control
signal S4 to be output to the high-frequency power supply 26 is
controlled. When the radical density is high, the supply power is
decreased to suppress plasma generation. When the radical density
is low, the supply power is increased to promote plasma
generation.
[0052] To adjust the temperature of the susceptor 2, the control
signal S5 to be output to the power supply of the heater 3 is
controlled. When the radical density is high, the temperature of
the susceptor 2 is increased to increase the gas temperature, thus
suppressing Si deposition. When the radical density is low, the
temperature of the susceptor 2 is decreased to decrease the gas
temperature, thus promoting Si deposition.
[0053] These control operations are performed by combining
proportional control, derivative control, and integral control.
[0054] When the radical density is maintained at a constant level
in this manner, the process reproducibility is improved, so that a
uniform Si thin film can be formed on the individual glass
substrates W.
[0055] In this embodiment, the ultraviolet light UV is used for
measuring the radical density. Alternatively, vacuum ultraviolet
light VUV can be used. This also applies to other embodiments to be
described later. When the vacuum ultraviolet light VUV is to be
used, the interior of the input light guide 41A connected between
the hollow cathode lamp 41 and chamber 1 and the interior of the
output light guide 42A connected between the ultraviolet
light-receiving section 42 and chamber 1 are set at a vacuum state,
so that attenuation of the vacuum ultraviolet light VUV can be
suppressed.
[0056] In this embodiment, the density of the atomic Si radicals is
measured. Alternatively, the density of molecular SiH.sub.x and
SiF.sub.x (x=1, 2, and 3) radicals may be measured to control
parameters for plasma generation. Alternatively, all these density
measurements may be performed to control parameters for plasma
generation.
Second Embodiment
[0057] The volume of the chamber 1 is constant. Under a constant
pressure, the density of radicals contained in the plasma P is
inversely proportional to the temperature of a gas containing
molecular or atomic radicals. For example, the higher the gas
temperature, the lower the radical density. Also, the higher the
gas temperature, the higher the radical speed. When measuring the
radical density by absorption spectroscopy, as the gas temperature
increases, the number of radicals appearing on the optical path of
the ultraviolet light UV increases. Then, the attenuation amount of
the ultraviolet light UV passing through the plasma P increases, so
that the radical density is measured to be larger than it actually
is. Accordingly, to perform parameter control based on the plasma
density more accurately, the gas temperature must be considered. A
high-frequency plasma CVD apparatus that has such a function will
be described.
[0058] FIG. 2 is a diagram showing the arrangement of a
high-frequency plasma CVD apparatus according to the second
embodiment of the present invention. FIG. 2 shows a section
perpendicular to the central axis of a chamber 1. The same
constituent elements as those shown in FIG. 1 are denoted by the
same reference numerals.
[0059] The CVD apparatus according to this embodiment has a gas
temperature measuring means in addition to a radical density
measuring means. The molecule level changes in accordance with the
temperature. Also, light absorption wavelength changes in
accordance with the molecule level. The gas temperature measuring
means utilizes these facts to measure the temperature of a gas
contained in the plasma on the basis of the attenuation amount of
light passing through the plasma. More specifically, the gas
temperature measuring means includes a laser beam output section 51
arranged outside the chamber 1, a laser beam receiving section 52,
and a gas temperature calculating section (analyzing means) 53.
[0060] The laser beam output section 51 sweeps with an output laser
beam L having a wavelength of 251.6 nm as the center. As the laser
beam output section 51, a ring dye laser oscillator or the like is
used. The laser beam L output from the laser beam output section 51
is input to the chamber 1 through a laser beam transmission window
6A formed in the side wall of the chamber 1.
[0061] The laser beam receiving section 52 receives the laser beam
L output from the chamber 1 through a laser beam transmission
window 6B formed in the side wall of the chamber 1, and outputs the
light reception amount to the gas temperature calculating section
53. While the process gas is not introduced and the plasma P is not
generated, the light reception amount of the ultraviolet light UV
is measured in advance and set in the gas temperature calculating
section 53, prior to the process, as the light emission amount of
the laser beam L.
[0062] The transmission windows 6A and 6B are made of quartz and
arranged at opposite positions through the central axis of the
chamber 1. The optical path of the laser beam L is set at the same
height as that of the optical path of the laser beam L used for
radical density measurement. The transmission windows 6A and 6B
have the same arrangement as that of the ultraviolet light
transmission windows 5A and 5B described in the first embodiment,
so no pollutant attaches to them. More specifically, the
transmission windows 6A and 6B may be heated to a high temperature
of about 200.degree. C. to 400.degree. C., or be formed of
capillary plates each having a cylindrical structure with an aspect
ratio of 3 or more. The capillary plates may have bottoms.
[0063] The gas temperature calculating section 53 obtains the
attenuation amount spectrum of the laser beam L passing through the
plasma on the basis of the light emission amount of the laser beam
L input in advance and the output signal from the laser beam
receiving section 52 and the radical absorption profile for the
wavelength from the pattern of the attenuation amount spectrum, to
calculate the temperature of the gas contained in the plasma P, and
outputs the calculated temperature to a controller 44A. In the same
manner as in radical density measurement, a chopper is arranged in
the optical path between the laser beam output section 51 and
chamber 1. In the laser beam receiving section 52, the light
reception amount obtained when the laser beam L is absent is
subtracted from the light reception amount obtained when the laser
beam L is present. Thus, the influence of background light is
removed, so that an accurate temperature is calculated.
[0064] The controller 44A controls parameters for plasma
generation, on the basis of output signals from a radical density
calculating section 43 and the gas temperature calculating section
53, by considering the temperature error in the radial density
measured by absorption spectroscopy.
[0065] When temperature correction of parameter control is
performed in this manner, the process reproducibility can be
further improved.
[0066] In this embodiment, the calculation result of the gas
temperature calculating section 53 is output to the controller 44A.
Alternately, the calculation result may be output to a radical
density calculating section to perform temperature correction of
the radical density. The corrected radical density may be output to
a controller 44, and parameter control may be performed in the same
manner as in the first embodiment.
Third Embodiment
[0067] FIG. 3 is a diagram for explaining an example of a
high-frequency plasma CVD apparatus according to the third
embodiment of the present invention. FIG. 3 shows a section
perpendicular to the central axis of a chamber 1. The same
constituent elements as those shown in FIG. 1 are denoted by the
same reference numerals. For the descriptive convenience, FIG. 3
shows an X-Y coordinate system having the center of the chamber 1
as the origin.
[0068] In this embodiment, a plurality of optical paths of
ultraviolet light UV used for radical density measurement are set
on a plane parallel to the stage surface of a susceptor 2. For
example, as shown in FIG. 3, when the respective optical paths are
to be set parallel to the X-axis, the absolute values of the
Y-coordinates of the respective optical paths are set to be
different from each other.
[0069] Input mirrors 61A, 61B, 61C, 61D, 61E, 61F, and 61G which
reflect UV output from a hollow cathode lamp 41 and guide it to the
corresponding optical paths so that the ultraviolet light UV passes
through the respective optical paths, output mirrors 62A, 62B, 62C,
62D, 62E, 62F, and 62G which reflect the ultraviolet light UV
passing through the respective optical paths and guide it to an
ultraviolet light-receiving section 42, and ultraviolet light
transmission windows 5 arranged on the respective optical paths are
provided. The reflection surfaces of the input mirrors 61A to 61G
and of the output mirrors 62A to 62G are sequentially rotated so
that the ultraviolet light sequentially passes through the
respective optical paths. Thus, the plurality of optical paths can
be set by time division.
[0070] The radical density calculated from the ultraviolet light UV
passing through each optical path represents the integral value of
the radical density on the optical path. Hence, assuming that the
radicals are distributed concentrically around the central axis of
the chamber 1, the radical densities of the respective beams of the
ultraviolet light UV passing through the plurality of optical paths
may be obtained and subjected to Abel conversion, so that a
two-dimensional radical density distribution can be obtained. Since
Abel conversion can be applied to a cylindrical shape, in this
case, the shape of the chamber 1 is preferably cylindrical. Also,
the number of optical paths equal to or larger than the amount of
the resolution of the radical density distribution or more is
necessary.
[0071] Parameter control for plasma generation is performed
two-dimensionally on the basis of the obtained radical density
distribution, so that the process reproducibility can be further
improved. To perform parameter control for plasma generation
two-dimensionally, for example, a plurality of gas introducing
ports for introducing source gases into the chamber 1 are formed in
the radial direction of the chamber 1, so that the gas flow rates
for the respective gas introducing ports can be controlled
individually. Also, a plurality of heaters to be incorporated in
the susceptor 2 are arranged concentrically. The temperatures of
the respective heaters should be able to be controlled
individually.
[0072] For example, assume that as a result of Abel conversion, a
high-density radical density distribution is obtained at the
central portion of the chamber 1, as shown in FIG. 5A. In this
case, control is performed to decrease the flow rate of the gas
toward the central portion of the chamber 1, as shown in FIG. 5B,
so that the closer to the peripheral portion, the larger the gas
flow rate. Thus, the radical density distribution becomes uniform,
as shown in FIG. 5C.
[0073] A plurality of optical paths can be set by frequency
division. In this case, choppers (modulators) 63A, 63B, 63C, 63D,
63E, 63F, and 63G which perform CW modulation (Carrier Wave
modulation) for the ultraviolet light UV are arranged on the
respective optical paths. The modulation frequencies of the
choppers 63A to 63G are different from each other. As the input
mirrors 61A to 61G, those which reflect part of the ultraviolet
light and transmit the remaining ultraviolet light are used. The
ultraviolet light UV which has passed through each optical path has
a different carrier wave frequency. Thus, in the ultraviolet
light-receiving section 42, the ultraviolet light UV is separated
by the carrier wave frequency. The radical densities are obtained
from the respective separated beams of the ultraviolet light, and
are subjected to Abel conversion, so that a two-dimensional radical
density distribution can be obtained.
[0074] If a plurality of ultraviolet light transmission windows for
radical density measurement are arranged in the axial direction (Z
direction) of the chamber 1, and the radical density distribution
in the Z direction is measured, a three-dimensional radical density
distribution can be obtained. When parameter control for plasma
generation is performed based on this radical density distribution,
the process reproducibility can be further improved.
[0075] In the same manner as in the case described above wherein
the two-dimensional radical density distribution is measured, a
plurality of optical paths may be set for a laser beam L used for
gas temperature measurement on a plane parallel to the stage
surface of the susceptor 2 by time division or frequency division.
The two-dimensional gas temperature distribution may be obtained
from the laser beam L passing through the respective optical paths.
The parameters for plasma generation may be controlled by
considering the temperature error of the two-dimensional radical
density distribution. To cause the laser beam L to pass through the
respective optical paths, mirrors or/and choppers may be used in
the same manner as in radical density measurement.
[0076] Furthermore, a three-dimensional gas temperature
distribution may be obtained, and the parameters for plasma
generation may be controlled by considering the temperature error
of the three-dimensional radical density distribution described
above.
Fourth Embodiment
[0077] According to the fourth embodiment of the present invention,
the electron temperature of a plasma P is estimated from the
radical density measured in the first embodiment. Parameters for
plasma generation are controlled such that the estimated electron
temperature becomes close to a preset value.
[0078] For example, SiH.sub.4 and SiF.sub.4 decompose in accordance
with the following reaction formulae. Figures in parentheses
indicate dissociation energies.
1 (1) SiH.sub.4 .fwdarw. SiH.sub.3 + H (8.75 eV) SiH.sub.4 .fwdarw.
SiH.sub.2 + 2H (9.47 eV) SiH.sub.4 .fwdarw. SiH + 3H (9.47 eV)
SiH.sub.4 .fwdarw. Si + 4H (10.33 eV) (2) SiF.sub.4 .fwdarw.
SiF.sub.3 + F (7.25 eV) SiF.sub.4 .fwdarw. SiF.sub.2 + 2F (4.6 eV)
SiF.sub.4 .fwdarw. SiF + 3F (6.8 eV) SiF.sub.4 .fwdarw. Si + 4F
(6.0 eV)
[0079] As is apparent from the above reaction formulae, to
decompose SiH.sub.4 and SiF.sub.4 to Si, high-energy electrons are
necessary. Accordingly, the electron energy, i.e., the electron
temperature can be estimated by measuring the behavior (magnitude
of the density) of the Si radicals. As described above, the
electron temperature is a parameter that is very significant in
determining dissociation.
Fifth Embodiment
[0080] According to the fifth embodiment of the present invention,
parameters for plasma generation are controlled to decrease the Si
radical density measured in the first embodiment.
[0081] Si has a high reaction constant, and accordingly reacts
as:
Si+SiH.sub.4.fwdarw.Si.sub.2H.sub.4
Si+SiF.sub.4 .fwdarw.Si.sub.2F.sub.4
[0082] to generate high-order molecular radicals one after another.
Accordingly, information on the behavior of high-order radicals can
be obtained by measuring the density of the Si radicals. The
high-order radicals generate dust and particles. Therefore, when
control is performed to decrease the Si radical density, generation
of high-order radicals is suppressed, and dust or the like can be
prevented.
Sixth Embodiment
[0083] The present invention can also be applied to a
high-frequency plasma etching apparatus. An embodiment of the
high-frequency plasma etching apparatus will be described as the
sixth embodiment.
[0084] To etch an Si thin film or SiO.sub.2 thin film, Cl.sub.2 or
C.sub.xF.sub.y (e.g., CF.sub.4, C.sub.4F.sub.8, or C.sub.5F.sub.7)
is used as an etching gas. At this time, the following reactions
take place on the thin film:
Si+Cl.sub.2.fwdarw.SiCl.sub.2 or Si+4Cl.fwdarw.SiCl.sub.4
SiO.sub.2+CF.sub.2.fwdarw.SiF.sub.2+CO.sub.2
[0085] By-products generated in these reactions are SiCl.sub.2,
SiCl.sub.4, SiF.sub.2, and SiF.sub.4. These by-products decompose
in the plasma during the etching process to generate Si radicals.
Therefore, in the etching process, when the Si radical density is
measured and parameters for plasma generation are controlled, the
process reproducibility and etching characteristics can be ensured
and controlled.
[0086] The above embodiments exemplify high-frequency plasma
apparatuses. The present invention can also be applied to any
plasma apparatus such as a capacitive coupling type plasma
apparatus, induction coupling type plasma apparatus, or ECR plasma
apparatus. Note that such apparatus is aimed at generating a plasma
which uses a gas containing at least Si or a plasma with which
by-products containing at least Si are generated from a solid
surface.
[0087] The present invention is not limited to a process using a
plasma, but can also be applied to a process in which a gas
dissociates in an atmosphere to generate Si. For example, the
present invention can be applied to a CatCVD or a CVD utilizing a
catalyst. The present invention is not limited to a process using a
gas, but can also be applied to, e.g., sputtering.
[0088] The present invention can also be applied to a nitriding
process containing N.sub.2 gas for an Si substrate (layer) or
SiO.sub.2 film, or an oxidizing process containing O.sub.2 gas for
an Si substrate (layer). In the nitriding process or oxidizing
process, the present value of N radical or O radical density
directly contributing to the reaction can be measured, and control
operation can be performed to make the density constant. Thus, a
sufficient effect can be obtained. To measure the N radical
density, vacuum ultraviolet light having a wavelength of
approximately 120 nm is used. To measure the O radical density,
vacuum ultraviolet light having a wavelength of approximately 130
nm is used. Regarding an N-based gas, for example, the light
emission spectrum of N radicals is measured. The rotational
temperature can be obtained from the intensity distribution of the
envelopes of the light emission spectrum. In an equilibrium state,
the rotational temperature coincides with a translational
temperature. Hence, the N radical density can be
temperature-corrected with the obtained gas temperature.
[0089] To measure the F or H radical density, ultraviolet light
having a wavelength of approximately 96 nm or 121.6 nm may be used,
and control operation may be performed such that the respective
densities become constant. This also applies to C radicals. Control
operation based on the result of density measurement is
possible.
* * * * *