U.S. patent application number 11/574571 was filed with the patent office on 2008-06-05 for ashing method and ashing apparatus.
Invention is credited to Katsuhiro Yamazaki.
Application Number | 20080132078 11/574571 |
Document ID | / |
Family ID | 35999787 |
Filed Date | 2008-06-05 |
United States Patent
Application |
20080132078 |
Kind Code |
A1 |
Yamazaki; Katsuhiro |
June 5, 2008 |
Ashing Method And Ashing Apparatus
Abstract
An ashing device and ashing method that can positively remove
resist from a wafer while preventing degradation of the film
material properties of exposed porous Low-K film on the wafer. The
ashing device of the present invention introduces a gas to a
dielectric plasma generating chamber 14, excites said gas to
generate a plasma, and performs plasma processing using said gas
plasma on a processing work S in use of a Low-K film. The ashing
gas introduced from a gas regulator 20 is an inert gas to which
H.sub.2 has been added. The configuration is formed so that plasma
is generated from the gas blend, and the resist is removed by the
hydrogen radicals generated.
Inventors: |
Yamazaki; Katsuhiro;
(Kanagawa, JP) |
Correspondence
Address: |
SNELL & WILMER LLP (OC)
600 ANTON BOULEVARD, SUITE 1400
COSTA MESA
CA
92626
US
|
Family ID: |
35999787 |
Appl. No.: |
11/574571 |
Filed: |
December 14, 2004 |
PCT Filed: |
December 14, 2004 |
PCT NO: |
PCT/JP04/18629 |
371 Date: |
September 5, 2007 |
Current U.S.
Class: |
438/710 ;
156/345.35; 257/E21.218; 257/E21.256 |
Current CPC
Class: |
G03F 7/427 20130101;
H01L 21/31138 20130101 |
Class at
Publication: |
438/710 ;
156/345.35; 257/E21.218 |
International
Class: |
H01L 21/3065 20060101
H01L021/3065 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 1, 2004 |
JP |
2004-254248 |
Claims
1. An ashing method of introducing a gas to a plasma generating
chamber formed at least in part of a dielectric material, exciting
said gas to generate a plasma, and performing plasma processing
using said gas plasma on a processing subject in use of a Low-K
film, said method comprising the steps of: introducing an inert gas
to which H.sub.2 has been added to said plasma generating chamber
at a ratio of between 10% and 20%; and; generating plasma by
exciting said inert gas and removing resist on said processing
subject by hydrogen radicals that are generated.
2. (canceled)
3. The ashing method according to claim 1, wherein H.sub.2O is
added to said inert gas to which H.sub.2 has been added, plasma is
generating using this gas blend, and the resist on said processing
subject is removed by hydrogen radicals that are generated.
4. The ashing method according to claim 3, wherein H.sub.2O is
added to said inert gas at a ratio of between 0.1% and 5%.
5. The ashing method according to claim 1, wherein O.sub.2 is added
to said inert gas to which H.sub.2 has been added, plasma is
generated by using this inert gas, and the resist on said
processing subject is removed by hydrogen radicals that are
generated.
6. The ashing method according to claim 5, wherein O.sub.2 is added
to said inert gas at a ratio of between 0.01% and 0.1%.
7. An ashing device that introduces a gas to a plasma generating
chamber formed, at least in part, of dielectric material, excites
said gas to generate a plasma, and performs plasma processing using
said gas plasma on a processing subject in use of Low-K film,
wherein said gas introduced to said plasma generating chamber is an
inert gas to which H.sub.2 has been added at a ratio between 1% and
20%.
8. (canceled)
9. The ashing device according to claim 7, wherein H.sub.2O is also
added to said inert bas to which H.sub.2 has been added.
10. The ashing device according to claim 9, wherein said H.sub.2O
is added at a ratio of between 0.1% and 5%.
11. The ashing device according to claim 7, wherein O.sub.2 is also
added to said inert gas to which H.sub.2 has been added.
12. The ashing device according to claim 11, wherein said O.sub.2
is added at a ratio of between 0.01% and 0.1%.
13. The ashing device according to claim 7, wherein said inert gas
comprises He.
14. The ashing device accordingly to claim 7, wherein the
positional relationship between said processing subject and said
plasma generating chamber is arranged to prevent linear irradiation
so that ultraviolet light included in said plasma does not directly
radiate onto the processing subject from said plasma generating
chamber.
15. The ashing method according to claim 1, wherein H.sub.2O is
added to said inert gas to which H.sub.2 has been added, plasma is
generating using this gas blend, and the resist on said processing
subject is removed by hydrogen radicals that are generated.
16. The ashing method according to claim 1, wherein O.sub.2 is
added to said inert gas to which H.sub.2 has been added, plasma is
generated by using this inert gas, and the resist on said
processing subject is removed by hydrogen radicals that are
generated.
17. (canceled)
18. The ashing device according to claim 7, wherein O.sub.2 is also
added to said inert gas to which H.sub.2 has been added.
19. The ashing device according to claim 9, wherein the inert gas
comprises He, and the positional relationship between said
processing subject and said plasma generating chamber is arranged
to prevent linear irradiation so that ultraviolet light included in
said plasma does not directly radiate onto the processing subject
from said plasma generating chamber.
20. The ashing device according to claim 9, wherein the inert gas
comprises He, and the positional relationship between said
processing subject and said plasma generating chamber is arranged
to prevent linear irradiation so that ultraviolet light included in
said plasma does not directly radiate onto the processing subject
from said plasma generating chamber.
21. The ashing device according to claim 10, wherein the inert gas
comprises He, and the positional relationship between said
processing subject and said plasma generating chamber is arranged
to prevent linear irradiation so that ultraviolet light included in
said plasma does not directly radiate onto the processing subject
from said plasma generating chamber.
22. The ashing device according to claim 12, wherein the inert gas
comprises He, and the positional relationship between said
processing subject and said plasma generating chamber is arranged
to prevent linear irradiation so that ultraviolet light included in
said plasma does not directly radiate onto the processing subject
from said plasma generating chamber.
Description
TECHNICAL FIELD
[0001] The present invention relates to an ashing device for
peeling photoresist that is used as a mask when making a circuit on
a wafer in a semiconductor wafer process, and more particularly to
technology to prevent reduction of the ashing rate and increase the
life of a plasma generating chamber member.
BACKGROUND TECHNOLOGY
[0002] LSI (Large Scale Integration) circuits are semiconductor
integrated circuits which have over 1000 elements, and ULSI or the
like are those which have over one million elements stored on a
single chip, and in recent years, 100 million or more elements have
been formed on a single chip.
[0003] This type of ULSI cannot be accommodated simply by
miniaturizing elements on a plane, so multiple layer wiring
construction with a plurality of overlapping layers of wiring has
become essential. A multiple layer wiring construction increases
the capacitance between layers and causes the elements to have
longer signal delay times, so in order to reduce the capacitance
between layers, a low dielectric constant interlayer insulating
film (hereinafter referred to as Low-K film) is used as an
insulating film between layers.
[0004] Incidentally, the ashing process that removes the unneeded
resist mask after patterning conventionally uses oxygen (O.sub.2)
plasma. However, the dielectric constant of Low-K films is
dramatically increased by ashing with oxygen plasma. In particular,
interlayer insulating films which use porous materials with a low
relative dielectric constant have a plurality of fine air voids
which are exposed (large relative surface area), so the resistance
to highly reactive oxygen plasma is extremely low, the film
properties are easily degraded, and the degradation due to oxygen
plasma is very significant.
[0005] Therefore, technology has been developed to prevent
degradation of a Low-K film by performing ashing using plasma
produced from a gas blend containing nitrogen and hydrogen but no
oxygen (Refer to Patent Reference 1), or to perform ashing using an
oxygen-free plasma from a gas containing hydrogen and a gas
containing fluorine (Refer to Patent Reference 2).
[0006] Patent Reference 1: Japanese Laid-open Patent Application
2002-261092
[0007] Patent Reference 2: Japanese Laid-open Patent Application
2001-110775
[0008] With the wafer ashing process when the aforementioned Low-K
film is used as an interlayer insulation film, removing the resist
by conventional ashing using oxygen (O.sub.2) plasma is not
suitable, so ashing gas conditions that are completely different
from conventional are required, and plasma processing has been
performed using hydrogen (H.sub.2), nitrogen (N.sub.2), or ammonia
(NH.sub.3) and the like. However, there are problems with the
processing capability of the plasma processing equipment when these
ashing gas conditions are used.
[0009] In other words, with a gas blend of nitrogen and hydrogen
disclosed in Patent Reference 1, as shown in FIG. 4 for example,
the ashing rate is high, but as shown in FIG. 3, there is a large
increase in the dielectric constant. Furthermore, with a gas blend
of gases containing hydrogen and gases containing fluorine
according to Patent Reference 2, there is a dramatic increase in
the dielectric constant and the film properties may be
degraded.
DISCLOSURE OF THE INVENTION
[0010] The present invention was proposed in order to resolve the
problems with the aforementioned conventional technology, and an
object of the present invention is to provide an ashing device and
ashing method which can positively remove resist from the wafer
while preventing degradation of film properties for Low-K film
(especially Low-K film that uses porous material) that is exposed
on the wafer. Note, in the following description, weight ratios
expressed as percentages are on a mass basis unless otherwise
noted.
[0011] In order to accomplish the aforementioned object, the
present invention is an ashing method of introducing a gas to a
plasma generating chamber formed at least in part of a dielectric
material, exciting the gas to generate a plasma, and performing
plasma processing using the gas plasma on a processing subject in
use of a Low-K film, the method comprising the steps of:
introducing an inert gas to which H.sub.2 has been added to the
plasma generating chamber; generating plasma by exciting the inert
gas; and removing resist that is on the processing subject by
hydrogen radicals that are generated.
[0012] With this embodiment, if an inert gas to which H.sub.2 has
been added is used as the ashing gas, the change in the dielectric
constant will be minimal, and the ashing rate will be high. Because
the ashing rate can be increased while reducing the increase in the
dielectric constant by using an inert gas to which H.sub.2 has been
added as the ashing gas, degradation of the film properties of a
porous Low-K film can be prevented, and resist can positively be
removed from the wafer.
[0013] In a preferred embodiment, H.sub.2 is added to an inert gas
at a ratio of between 1 and 20%. In the aforementioned embodiment,
if the ratio of H.sub.2 added to the inert gas is in a range
between 1 and 20%, the change in the ashing rate compared to the
change in H.sub.2 will be within the range permitted by the
processing capability, and the ashing process will be stable.
[0014] In a preferred embodiment, H.sub.2O is added to the inert
gas to which H.sub.2 has been added, plasma is generated using the
gas blend, and the resist on the processing subject is removed by
the hydrogen radicals that are generated. Furthermore, the
preferred embodiment is characterized by also adding H.sub.2O to
the inert gas to which H.sub.2 has been added.
[0015] In this embodiment, deactivation of the H radical is
dramatically reduced by adding H.sub.2O to the inert gas, and as a
result, the amount of H radical that reaches the wafer can be
increased. Thereby, the peeling residual can be improved without
extending the processing time. An additional effect is that a
reducing effect on the dielectric material section as well as on
other materials of the plasma generating chamber inner surface or
the like can be minimized or prevented, thus contributing to
increased life of the plasma generating chamber member.
[0016] In a preferred embodiment, H.sub.2O is added to the inert
gas at a ratio of between 0.1 and 5%. In this embodiment,
deactivation of the H radical is dramatically reduced by adding
between 0.1 and 5% H.sub.2O to the inert gas, and as a result the
amount of H radical that reaches the wafer can be increased.
Thereby, the peeling residual can be improved without extending the
processing time. An additional effect is that a reducing effect on
the dielectric material section as well as on other materials of
the plasma generating chamber inner surface or the like can be
minimized or prevented, thus contributing to increased life of the
plasma generating chamber member.
[0017] In a preferred embodiment, O.sub.2 is added to the inert gas
to which H.sub.2 has been added, plasma is generated using this
inert gas, and the resist on the processing subject is removed by
hydrogen radicals that are generated. In this embodiment,
deactivation of the H radical is dramatically reduced by adding
O.sub.2 to the inert gas, and as a result the amount of H radical
that reaches the wafer can be increased. Thereby, the peeling
residual can be improved without extending the processing time. An
additional effect is that a reducing effect on the dielectric
material section as well as on other materials of the plasma
generating chamber inner surface or the like can be minimized or
prevented, thus contributing to increased life of the plasma
generating chamber member.
[0018] In a preferred embodiment, O.sub.2 is added to the inert gas
at a ratio of between 0.01 and 0.1%. In this embodiment,
deactivation of the H radical is dramatically reduced by adding
between 0.01 and 0.1% O.sub.2 to the inert gas, and as a result the
amount of H radical that reaches the wafer can be increased.
Thereby, the peeling residual can be improved without extending the
processing time. An additional effect is that a reducing effect on
the dielectric material section as well as on other materials of
the plasma generating chamber inner surface or the like can be
minimized or prevented, thus contributing to increased life of the
plasma generating chamber member.
[0019] In a preferred embodiment, the inert gas is consisting of
He. In this embodiment, He causes the level of metastable state
energy to be high, and for instance, even if trace amounts of
H.sub.2 are added, the startup of the in the ashing rate will be
fast. Furthermore, He is an atom with a mass essentially equal to
that of H.sub.2, so the gas diffusion will be favorable, and the
distribution of the ashing process on the wafer surface can be
expected to be uniform. Furthermore, a stable processing operation
can be performed.
[0020] In a preferred embodiment, the positional relationship
between the processing subject and the plasma generating chamber is
arranged to prevent linear irradiation so that ultraviolet rays
included in the plasma do not directly radiate onto the processing
subject from the plasma generating chamber. In this type of
embodiment, the ultraviolet rays included in the plasma that is
generated in the plasma generating chamber will be eliminated prior
to reaching the processing subject, and only radicals will be
supplied to the surface of the processing subject. Therefore, the
increase in the dielectric constant of the processing subject
caused by impingement of ultraviolet light on the processing
subject can be reduced.
[0021] With the present invention as described above, the ashing
rate can be increased while an increase in the dielectric constant
can be minimized by using a gas blend of H.sub.2 and inert gas as
the ashing gas. Therefore, degradation of the film properties of
Low-K film (especially Low-K film which uses porous materials) can
be prevented, and resist can positively be removed from the wafer.
Furthermore, if He is used as the inert gas, favorable results with
no change in the dielectric constant can be achieved.
[0022] Furthermore, deactivation of H radical can be dramatically
minimized by adding H.sub.2O or O.sub.2 to the gas blend of H.sub.2
and inert gas, and as a result, the peeling residue can be improved
for the same processing time because the level of H radical that
reaches the wafer is increased, and furthermore as an additional
result, reducing of the material on the inner surface of the plasma
generating chamber can be reduced, thus contributing to the
extended life of the plasma generating chamber materials.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a block diagram showing the first embodiment of
the present invention;
[0024] FIG. 2 is a diagram showing the change in the ashing rate
when H.sub.2 is added to the inert gas;
[0025] FIG. 3 is a diagram showing the change in the dielectric
constant when H.sub.2 is added to the inert gas;
[0026] FIG. 4 is a diagram showing the changes to the ashing rate
when H.sub.2 is added to the inert gas;
[0027] FIG. 5 is a partial expanded diagram showing the structure
of the first embodiment of the present invention;
[0028] FIG. 6 is a partial expanded diagram showing an alternate
example of the first embodiment of the present invention;
[0029] FIG. 7 shows the change in the ashing rate when H.sub.2O is
added to a gas blend of H.sub.2 and He; and
[0030] FIG. 8 is a diagram showing the change in the dielectric
constant when H.sub.2O or O.sub.2 is added to a gas blend of
H.sub.2 and He.
BEST MODE FOR CARRYING OUT THE INVENTION
[0031] Next, the mode for carrying out the present invention
(hereinafter referred to as embodiment) will be described in detail
while referring to the drawings. Note, in the following
description, weight ratios expressed as percentages are on a mass
basis unless otherwise noted.
First Embodiment
[0032] The ashing device of the present embodiment provides a
process chamber 2 which is a vacuum chamber 1 inside a vacuum
chamber 1 as shown in FIG. 1. A support stand 3 is provided in the
process chamber 2, and the processing subject S is placed on the
support stand 3. Note, the support stand 3 has a temperature
control mechanism not shown in the drawings, and the temperature of
the processing subject S can be controlled by this temperature
control mechanism. The processing subject includes silicon wafers
for manufacturing semiconductor devices and glass substrates for
liquid crystal display devices.
[0033] An exhaust port 5 is formed in the bottom plate 4 of the
vacuum chamber 1, and an exhaust pipe 6 connected to a vacuum pump
(not shown in the drawings) on one end is attached to the exhaust
port 5. Furthermore, a gas injection port 8 is formed in the center
of the upper lid 7 which forms the top plate of the vacuum chamber
1, and a gas injection pipe 9 made of a fluorine based resin is
attached to the gas injection port 8.
[0034] A plasma generating chamber member 10 is connected to the
gas injection pipe 9. Quartz (SiO.sub.2), alumina
(Al.sub.2O.sub.3), sapphire, or aluminum nitride or the like can be
used as the dielectric material which forms the plasma generating
chamber member 10.
[0035] Furthermore, a sealing member 11 is attached to the other
end of the plasma generating chamber member 10, and the inside of
the sealing member 11 forms a gas flow path 19. A gas transport
pipe 18 is connected to the sealing member 11, and a gas regulator
20 that supplies ashing gas to the plasma generating chamber member
10 is provided on the other end of the gas transport pipe 18.
[0036] A radical generating means comprising a microwave waveguide
pipe 12, or in other words a plasma generating unit 13, is provided
along the plasma generating chamber member 10 so as to encompass
the plasma generating chamber member 10, and a plasma generating
chamber 14 is formed inside the plasma generating chamber member 10
which is encompassed by the plasma generating unit 13. Therefore,
the plasma generating chamber 14 is provided on the outside of the
vacuum chamber 1. The microwave generating unit 15 is connected to
the microwave waveguide pipe 12.
[0037] Furthermore, a gas storage chamber 16 is formed on the top
of the process chamber 2 and a shower nozzle 17 is provided in
order to uniformly supply the radicals (etching seed) injected into
the process chamber 2 through the gas injection port 8 formed in
the upper lid 7 (top plate) of the vacuum chamber 1 across the
whole surface of the processing subject S. Furthermore, a plurality
of gas spray holes are formed in the shower nozzle 17.
[0038] This embodiment is characterized by the fact that the
composition ratio of the ashing gas introduced to the plasma
generating chamber member 10 is controlled by the gas regulator 20
when ashing is performed using the aforementioned ashing device. In
other words, the ashing gas used in the present embodiment is an
inert gas to which H.sub.2 has been added. Plasma is generated
using this gas blend, and the resist is removed by the hydrogen
radicals that are generated. The inert gas used may be for instance
helium (He) or argon (Ar).
[0039] The ratio of H.sub.2 gas in the ashing gas is within a range
between 1 and 20% of the total mass flow, but, is preferably
approximately 5% or higher which is essentially the saturation
level for the ashing rate (A/R) as shown in FIG. 2.
[0040] Furthermore, the rise in the ashing rate will be fast even
when trace amounts of H.sub.2 are added because He has a higher
metastable state energy than does Ar. Therefore, when the H.sub.2
ratio is in a range around 5%, the rate saturated He will have less
variation compared to the relative change of H.sub.2, which is
preferable. Furthermore, He is an atom with a mass essentially
equal to that of H.sub.2, so the gas diffusion will be favorable
compared to when Ar is used, and the distribution of the ashing
process on the wafer surface can be expected to be uniform.
Therefore the use of He is preferable in order to achieve a stable
process.
[0041] Therefore, as shown in FIG. 2, favorable results can be
obtained for the damage (degradation) to the Low-K film without
changing the dielectric constant when He or Ar with H.sub.2 added
is used as the ashing gas. In contrast, when 5% O.sub.2 is added to
He to make the ashing gas, the ashing rate will be high as shown in
FIG. 4, but there will be problems with a significant increase in
the dielectric constant as shown in FIG. 3.
[0042] Furthermore, as shown in FIG. 3, when 5% N.sub.2 is added to
He to make the ashing gas, the change in the dielectric constant
was minimal, but as shown in FIG. 4, the ashing rate was less than
half that when the ashing gas is He or Ar with 5% H.sub.2 added. In
other words, when N.sub.2 is used, the Low-K film will be not be
damaged, but there will be problems with processing capacity for
the resist removing equipment. Furthermore, when N.sub.2 with 5%
H.sub.2 is used as the ashing gas, the ashing rate will be similar
to the case where 5% H.sub.2 is added to He or Ar, but there will
be a significant increase in the dielectric constant.
[0043] On the other hand, as shown in FIG. 3, if an inert gas such
as He or Ar with 5% H.sub.2 added is used as the ashing gas, the
change in the dielectric constant will be minimal, and as shown in
FIG. 4, the ashing rate will be high. Therefore, by using a gas
blend of He or Ar with H.sub.2 as the ashing gas, the ashing rate
can be increased and the increase in the dielectric constant can be
kept minimal, so degradation of the film properties for porous
Low-K films can be prevented, and resist can positively be removed
from wafers.
[0044] Note, the total flow of the ashing gas can be 1 slm
(standard liter/minute) or higher, but as the flow rate increases,
the ashing rate can be increased, so using a rate of approximately
7 slm is preferable. Furthermore, the processing pressure can be
within a range between 50 Pa and 200 Pa.
[0045] Furthermore, when ultraviolet light contacts with a Low-K
film, the dielectric constant will increase. The effect of the gas
composition ratio is stronger than the effect of ultraviolet light
described above, but with Low-K films which use a porous material
with a low dielectric constant (K=2 or lower), the effect is
remarkable. Therefore, with this embodiment, the ultraviolet light
is shielded to prevent direct irradiation of ultraviolet light from
the plasma generating unit on to the processing subject, so the
positional relationship between the processing subject and the
plasma generating unit is arranged so that there will not be linear
irradiation.
[0046] Specifically, as shown in FIG. 5, a bend is provided between
the plasma generating chamber 14 and the gas injection tube 9 or
the gas injection port 8, so ultraviolet light will not directly
impinge on the processing subject S. Furthermore, a construction
where the ultraviolet light is shielded such as by applying an
ultraviolet light absorbing material to the shower nozzle 17 is
also possible. Thereby the ultraviolet rays included in the plasma
generated in the plasma generating chamber 10 will be eliminated
prior to reaching the processing subject S, and only radicals will
be supplied through the shower nozzle 17 to the surface of the
processing subject S in the process chamber 2.
[0047] Note, the present embodiment described the case of a CDE
(chemical dry etching) device, but the aforementioned shielding
construction of the present invention is not restricted to this,
and for instance, the down-flow type dry etching device shown in
FIG. 6 has an overlapping construction where the position of the
holes of the shower nozzle (punching plate) are staggered, and
thereby, direct radiation by ultraviolet light onto the processing
subject S can be prevented. Furthermore, similar to as shown above,
an ultraviolet light can be absorbed by applying an ultraviolet
light absorbing material to the shower nozzle.
Second Embodiment
[0048] The ashing device according to the second embodiment adds a
change to the composition of ashing gas that is injected from the
gas regulator 20 in the first embodiment. Specifically, a
composition where between 0.01% and 0.1% O.sub.2 or between 1% and
5% H.sub.2O is added to the H.sub.2 and He gas blend. Note, other
components are similar to the aforementioned first embodiment and
have been omitted from the description.
[0049] With a resist ashing process where a Low-K film is exposed
on the processing subject S (wafer), peeling residue occurs after
ashing in a process where an H.sub.2 and He gas blend is used as
the ashing gas. If the plasma generating chamber member 10 is made
from SiO.sub.2 as described above, when a gas containing H.sub.2 is
supplied from the gas regulator 20 and the hydrogen plasma is
excited in the plasma generating chamber 14 over a discharge time
of several tens of hours, the SiO.sub.2 that forms the plasma
generating chamber member 10 will be reduced to Si. When the
SiO.sub.2 is converted to Si by reduction from the hydrogen plasma,
the H radicals required for ashing will be dramatically
deactivated. Therefore, the ashing rate will normally be reduced
after several tens of hours, and therefore peeling residual will
occur after ashing. This peeling residual can be eliminated by
extending the processing time, but this will reduce the efficiency
of the processing operation.
[0050] With this embodiment, between 1 and 5% H.sub.2O is added to
the gas blend of H.sub.2 and He in order to prevent this peeling
residual. If H.sub.2O is added in this manner, oxygen plasma will
be generated in the plasma generating chamber 14. Furthermore,
reduction of the dielectric material (discharge tube and dielectric
material window) of the plasma generating chamber member 10 will be
prevented by the oxygen plasma, and the dielectric material will be
reoxidized. Therefore, the deactivation of H radical will be
dramatically reduced, and as a result, the amount of H radical that
reaches the wafer will be increased so peeling residual can be
resolved without increasing the processing time. An additional
effect is that the reducing effect on the dielectric material
section as well as on other materials of the plasma generating
chamber member 10 inner surface or the like can be minimized or
prevented, thus contributing to increased life of the plasma
generating chamber member 10.
[0051] FIG. 7 shows the change in the dielectric constant of a
Low-K film and the change in the ashing rate for the case where
H.sub.2O is added. Furthermore, FIG. 8 shows the change in the
dielectric constant when O.sub.2 is added as compared to
H.sub.2O.
[0052] As can be seen from FIG. 7, the ashing rate can be increased
to 1000 nm/min or higher by adding H.sub.2O to the gas blend of
H.sub.2 and He. This is due to the aforementioned increase in the
amount of H radical reaching the wafer in conjunction with the
effect of the oxygen radical generated. Therefore, the peeling
residual on the wafer can be eliminated without extending the
processing time. Furthermore, as shown in FIG. 8, when 0.1 to 5% of
H.sub.2O is added, there is almost no change in the dielectric
constant of the Low-K film, and favorable film properties are
obtained.
[0053] Similarly, when O.sub.2 is added in order to eliminate the
peeling residual without extending the processing time, there will
be a change to the material properties of the Low-K film when a
small amount of approximately 1% of O.sub.2 is added, but as can be
seen in FIG. 8, use of O.sub.2 is possible if the amount added is
approximately 0.1%.
[0054] The reason that the permissible range for the amount of
O.sub.2 added is narrower than that of H.sub.2O is not definitely
understood, but is thought to be affected by the difference in the
life of the O.sub.2 radical generated when O.sub.2 is added and
when H.sub.2O is added, and to the difference that the activity
level (reactivity) towards Low-K film has on the change in the
dielectric constant. With Low-K films with lower dielectric
constants which use porous materials, a change in the dielectric
constant can easily occur, so the amount of O.sub.2 added is
preferably 0.01% or less.
[0055] In this manner, when H.sub.2O is added, or when O.sub.2 is
added, the change in the dielectric constant will be similar, but
the ashing rate will be superior if O.sub.2 is added. On the other
hand, the amount of O.sub.2 added must be held to very small
quantities, and the range across which the dielectric constant will
not rise is narrow, between 0.01 and 0.1%. Therefore, minute
changes in the flow rate during the actual processing operation can
have a major impact on the increase in the dielectric constant. In
contrast, when H.sub.2O is added, the range that can be permitted
is broad, between 0.1 and 5%, so even if the flow rate or the like
varies somewhat during the actual processing operation, the effect
on increasing the dielectric constant will be minimal, and the
processing operation can be stable.
[0056] As described above, deactivation of H radical can be
dramatically reduced by adding either between 0.01% and 0.1% of
O.sub.2 or between 0.1 and 5% of H.sub.2O to the gas blend of
H.sub.2 and He that is injected from the gas regulator 20, and as a
result, the amount of H radical that reaches the wafer can be
increased. Thereby, the peeling residual can be improved without
extending the processing time. An additional effect is that the
reducing effect on the dielectric material section as well as on
other materials of the plasma generating chamber inner surface or
the like can be minimized or prevented, thus contributing to
increased life of the plasma generating chamber materials.
Other Embodiments
[0057] Note, the ashing device and ashing method of the
aforementioned embodiments can not only be used for resist ashing
on a wafer, but for instance can also be used as an etching device
and etching method for removing spontaneously generated oxides or
for directly etching Low-K films.
[0058] Furthermore, in the aforementioned embodiments, an example
where Ar or He is used as the inert gas was presented, and He was
described as being particularly preferable, but Ne may also be used
in place of the Ar, and although processing uniformity will be lost
by using heavy gases such as Kr (krypton), Xe (xenon), and Rn
(radon), a similar effect can be anticipated.
[0059] With the aforementioned embodiments, the use of a chemical
dry etching device or a down-flow type dry etching device was
described, but the present invention can be achieved not only by
these devices, but by any device that can perform ashing primarily
using radicals, and is preferably a device that can shield
ultraviolet light.
BRIEF DESCRIPTION OF THE DRAWINGS
[0060] FIG. 1 is a block diagram showing the first embodiment of
the present invention;
[0061] FIG. 2 is a diagram showing the change in the ashing rate
when H.sub.2 is added to the inert gas;
[0062] FIG. 3 is a diagram showing the change in the dielectric
constant when H.sub.2 is added to the inert gas;
[0063] FIG. 4 is a diagram showing the changes to the ashing rate
when H.sub.2 is added to the inert gas;
[0064] FIG. 5 is a partial expanded diagram showing the structure
of the first embodiment of the present invention;
[0065] FIG. 6 is a partial expanded diagram showing an alternate
example of the first embodiment of the present invention;
[0066] FIG. 7 shows the change in the ashing rate when H.sub.2O is
added to a gas blend of H.sub.2 and He; and
[0067] FIG. 8 is a diagram showing the change in the dielectric
constant when H.sub.2O or O.sub.2 is added to a gas blend of
H.sub.2 and He.
* * * * *