U.S. patent application number 10/043180 was filed with the patent office on 2002-09-12 for method for manufacturing a semiconductor device.
This patent application is currently assigned to Hitachi, Ltd.. Invention is credited to Itabashi, Naoshi, Kofuji, Naoyuki, Mori, Masahito, Tsutsumi, Takashi.
Application Number | 20020125206 10/043180 |
Document ID | / |
Family ID | 26611025 |
Filed Date | 2002-09-12 |
United States Patent
Application |
20020125206 |
Kind Code |
A1 |
Kofuji, Naoyuki ; et
al. |
September 12, 2002 |
Method for manufacturing a semiconductor device
Abstract
Provided are an etching method which uses an additive gas stably
suppliable also in future, is reduced in the problem of particle
contamination, is free from the problem of removability of
side-wall protection film and has high shape controlling capacity,
and a manufacturing method a highly-reliable semiconductor device
by using this etching method. This etching method comprises
depositing metal film including an aluminum over a semiconductor
device and etching the metal film with a plasma of a mixture gas
containing a Cl.sub.2 gas, a BCl.sub.3 gas and a CH.sub.2Cl.sub.2
gas.
Inventors: |
Kofuji, Naoyuki; (Tama,
JP) ; Mori, Masahito; (Hachioji, JP) ;
Itabashi, Naoshi; (Hachioji, JP) ; Tsutsumi,
Takashi; (Kawasaki, JP) |
Correspondence
Address: |
Miles & Stockbridge P.C.
Suite 500
1751 Pinnacle Drive
McLean
VA
22102-3833
US
|
Assignee: |
Hitachi, Ltd.
|
Family ID: |
26611025 |
Appl. No.: |
10/043180 |
Filed: |
January 14, 2002 |
Current U.S.
Class: |
216/2 ; 216/67;
216/77; 257/E21.311 |
Current CPC
Class: |
H01L 21/32136 20130101;
C23F 4/00 20130101 |
Class at
Publication: |
216/2 ; 216/67;
216/77 |
International
Class: |
C23F 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 17, 2001 |
JP |
2001-281001 |
Mar 12, 2001 |
JP |
2001-068030 |
Claims
What is claimed is:
1. A manufacturing method of a semiconductor device, which
comprises depositing metal film including an aluminum over a
semiconductor substrate, and etching the metal film with a plasma
of a mixture gas containing a Cl.sub.2 gas, a BCl.sub.3 gas and a
CH.sub.2Cl.sub.2 gas.
2. A method of claim 1, wherein the pressure of the mixture gas is
not greater than 1.5 Pa but 0.6 Pa or greater.
3. A method of claim 1, wherein the CH.sub.2Cl.sub.2 gas has a
purity of 99.99% or greater.
4. A method of claim 1, wherein the plasma is generated using an
electromagnetic wave within a frequency range of 300 MHz to 1
GHz.
5. A manufacturing method of a semiconductor device, which
comprises forming a multilayer interconnection of metals including
aluminum over a semiconductor substrate, wherein upon etching of
the metal multilayer interconnection, a plasma of a mixture gas
containing a Cl.sub.2 gas, a BCl.sub.3 gas and a CH.sub.2Cl.sub.2
gas is used.
6. A method of claim 5, wherein the pressure of the mixture gas is
not greater than 1.5 Pa but 0.6 Pa or greater.
7. A method of claim 5, wherein the CH.sub.2Cl.sub.2 gas has a
purity of 99.99% or greater.
8. A method of claim 5, wherein the plasma is generated using an
electromagnetic wave within a frequency range of 300 MHz to 1
GHz.
9. A manufacturing method of a semiconductor device, which
comprises forming metal films by stacking a TiN film, an Al film
and a TiN film successively over a semiconductor substrate, and
etching the metal films with a plasma of a mixture gas of a
Cl.sub.2 gas, a BCl.sub.3 gas and a CH.sub.2Cl.sub.2 additive gas,
wherein the CH.sub.2Cl.sub.2 gas is added in an amount of 0 to 4%
upon etching of the TiN film, whereas the amount of the
CH.sub.2Cl.sub.2 gas is increased to 5 to 30% during etching of the
Al film.
10. A manufacturing method of a semiconductor device, which
comprises depositing metal film including an aluminum over a
semiconductor substrate, forming a resist mask over the metal film,
etching the metal film with a plasma of a mixture gas of a Cl.sub.2
gas, a BCl.sub.3 gas and a CH.sub.2Cl.sub.2 gas, and removing the
resist mask with a plasma of a mixture gas containing an F element
and an O element.
11. A manufacturing method of a semiconductor device, which
comprises depositing metal film including an aluminum over a
semiconductor substrate, forming patterns at a wiring pitch less
than 500 nm over the metal film, and etching the metal film with a
plasma of a mixture gas containing a Cl.sub.2 gas, a BCl.sub.3 gas
and a CH.sub.2Cl.sub.2 gas.
12. A manufacturing method of a semiconductor device, which
comprises depositing metal film including an aluminum over a
semiconductor substrate, forming, over the metal film, first mask
patterns at a first wiring pitch and second mask patterns at a
second wiring pitch wider than the first wiring pitch, and etching
the metal films with a plasma of a mixture gas containing a
Cl.sub.2 gas, a BCl.sub.3 gas and a CH.sub.2Cl.sub.2 gas.
13. A manufacturing method of a semiconductor device, which
comprises depositing metal film including an aluminum over a
semiconductor substrate, forming, over the metal film, first
patterns at a first wiring pitch and second patterns at a second
wiring pitch wider than the first wiring pitch, and etching the
metal film with a plasma of a mixture gas containing a Cl.sub.2
gas, a BCl.sub.3 gas and a CH.sub.2Cl.sub.2 gas.
14. A manufacturing method of a semiconductor device, which
comprises forming metal films over a semiconductor substrate by
stacking a TiN film, an Al film and a TiN film one after another,
and etching the metal films with a plasma of a mixture gas
containing a Cl.sub.2 gas, a BCl.sub.3 gas and an additive gas
obtained by diluting a CH.sub.2Cl.sub.2 gas with a dilution gas,
wherein the mole concentration of the CH.sub.2Cl.sub.2 gas after
dilution with the dilution gas is 10% to 100%.
15. A manufacturing method of a semiconductor device, which
comprises depositing metal film including an aluminum over a
semiconductor substrate, and etching the metal film with a plasma
formed, in a plasma etching system for generating a plasma by using
an UHF-range electromagnetic wave, from a mixture gas containing a
Cl.sub.2 gas, a BCl.sub.3 gas and a CH.sub.2Cl.sub.2 gas.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a manufacturing method of a
semiconductor device, particularly to a manufacturing method of a
semiconductor device, which comprises, during manufacture of the
semiconductor device, plasma etching metal films including aluminum
(Al).
[0002] In plasma etching of a metal material, it is the common
practice to use a plasma of a mixture gas of Cl.sub.2 and BCl.sub.3
which are leading etching gases.
[0003] For microfabrication process, in addition to such gases, a
CCl.sub.4 gas, a CHCl.sub.3 gas, an N.sub.2 gas, a CHF gas or a gas
obtained by diluting a flammable and explosive CH gas to not
greater than an explosion limit is usually added as a shape
controlling gas, in other words, as an under cut preventive gas. In
Japanese Patent Application Laid-Open No. 251984/1997, proposed is
a method of adding a CHBr gas as a shape controlling gas.
[0004] Among the shape controlling gases to be added upon plasma
etching of a metal material, production of a CCl.sub.4 gas is
limited because it is an ozone depleting substance. Production of a
CHCl.sub.3 gas tends to be decreased owing to its
carcinogenicity.
[0005] In a gas such as CHF gas containing an F element, AlF
generated upon etching reaction forms particles having a large
particle size. These particles cause a yield reduction so that this
gas is not suited for mass production. Also in the case of an
N.sub.2 gas, AlN generated upon etching reaction forms particles so
that it is not suited for mass production.
[0006] A Br-containing gas such as CHBr gas forms, on the side
walls of a minute pattern during etching, a markedly strong
side-wall protection film for shape control. This side-wall
protection film cannot be removed by treatment with a chemical
liquid. A diluted CH gas,on the other hand, contains only several
percent of a C element having a shape controlling action so that it
is accompanied with such a drawback as small shape controlling
effects.
SUMMARY OF THE INVENTION
[0007] An object of the present invention is to provide an etching
method which uses a gas suppliable stably also in future, is
reduced in the problem of particle contamination, is free from the
difficulty in removal of side-wall protection films, and has high
shape controlling capacity, and a manufacturing method of a highly
reliable semiconductor device by using this etching method.
[0008] In the present invention, a CH.sub.2Cl.sub.2 gas is used as
an additive gas for shape control. Described specifically, a metal
material is etched by a plasma of a mixture of a Cl.sub.2 gas, a
BCl.sub.3 bas and a CH.sub.2Cl.sub.2 gas.
[0009] The specific and typical constitution of the present
invention will next be described. In one aspect of the present
invention, there is thus provided a manufacturing method of a
semiconductor device which comprises depositing metal film
including an aluminum over a semiconductor substrate and etching
the metal film by using a plasma of a mixture of a Cl.sub.2 gas, a
BCl.sub.3 gas and a CH.sub.2Cl.sub.2 gas.
[0010] In another aspect of the present invention, there is also
provided a manufacturing method of a semiconductor device, which
comprises, upon formation of multilayer interconnects of an
aluminum-containing metal over a semiconductor substrate, etching
of the metal interconnects by using a plasma of a mixture of a
Cl.sub.2 gas, a BCl.sub.3 gas and a CH.sub.2Cl.sub.2 gas.
[0011] In a further aspect of the present invention, there is also
provided a manufacturing method of a semiconductor device, which
comprises forming metal films over a semiconductor substrate by
stacking a TiN film, an Al film and a TiN film one after another;
and etching the metal films by using a plasma of a mixture of a
Cl.sub.2 gas, a BCl.sub.3 gas and a CH.sub.2Cl.sub.2 gas, wherein
the amount of CH.sub.2Cl.sub.2 gas is adjusted to 0 to 4% upon
etching of the TiN film, while it is adjusted to 5 to 30% during
etching of the Al film.
[0012] In a still further aspect of the present invention, there is
also provided a manufacturing method of a semiconductor device,
which comprises depositing metal film including an aluminum over a
semiconductor substrate, forming a resist mask over the metal film,
etching the metal film by using a plasma of a mixture of a Cl.sub.2
gas, a BCl.sub.3 gas and a CH.sub.2Cl.sub.2 gas and removing a
resist mask by using a plasma of a mixture containing an F element
and an O element.
[0013] In a still further aspect of the present invention, there is
also provided a manufacturing method of a semiconductor device,
which comprises depositing metal film including an aluminum over a
semiconductor substrate, forming patterns at a wiring pitch less
than 500 nm over the metal film, and etching the metal film with a
plasma of a mixture gas containing a Cl.sub.2 gas, a BCl.sub.3 gas
and a CH.sub.2Cl.sub.2 gas.
[0014] In a still further aspect of the present invention, there is
also provided a manufacturing method of a semiconductor device,
which comprises depositing metal film including an aluminum over a
semiconductor substrate, forming a first mask pattern group (or a
first pattern group) at a first pitch and then, a second mask
pattern group (or a second pattern group) at a second pitch over
the metal film, and etching the metal film by using a plasma of a
mixture of a Cl.sub.2 gas, a BCl.sub.3 gas and a CH.sub.2Cl.sub.2
gas.
[0015] In a still further aspect of the present invention, there is
also provided a manufacturing method of a semiconductor device,
which comprises forming metal films over a semiconductor substrate
by stacking a TiN film, an Al film and a TiN film one after
another, and etching the metal films by using a plasma of a mixture
of a Cl.sub.2 gas, a BCl.sub.3 gas and, as an additive gas, a
CH.sub.2Cl.sub.2 gas diluted with a diluting gas, wherein the mole
concentration of the CH.sub.2Cl.sub.2 gas diluted with the diluting
gas is 10% to 100%.
[0016] In a still further aspect of the present invention, there is
also provided the above-described constitutions, wherein the
pressure of the mixture gas is not greater than 1.5 Pa but 0.6 Pa
or greater; the CH.sub.2Cl.sub.2 gas has a purity of at least
99.99%; and the plasma is generated using an electromagnetic wave
having a frequency range of 300 MHz to 1 GHz (UHF range).
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 illustrates the characteristics of various additive
gases;
[0018] FIG. 2 illustrates the relationship between a ratio of
failure by particle contamination and the number of wafers
treated;
[0019] FIG. 3 illustrates the relationship between the CD shift
relative to a resist mask and the kind of additive gases;
[0020] FIG. 4 is a cross-sectional view, after washing treatment,
of a sample etched with a CH.sub.2Br.sub.2-containing gas;
[0021] FIG. 5 is a cross-sectional view, after washing treatment,
of a sample etched with the CH.sub.2Cl.sub.2-containing gas of the
present invention;
[0022] FIG. 6 is a flow chart for explaining one example of a
multilayer interconnection step of a semiconductor device to which
the etching method of the present invention is applied;
[0023] FIG. 7A illustrates the cross-sectional structure of a
sample used for metal etching, whereas FIG. 7B illustrates one
example of the etching results of the sample (FIG. 7A);
[0024] FIG. 8 illustrates the relationship between a wiring pitch
and undercut condition; and
[0025] FIG. 9 illustrates the relationship between the CD shift of
patterns formed at a wiring pitch of 100 nm and a dilution ratio of
CH.sub.2Cl.sub.2 when the sample of FIG. 7A is etched with a
mixture gas containing a CH.sub.2Cl.sub.2 gas diluted with Ar.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
EXAMPLE 1
[0026] Results of comparison between a CH.sub.2Cl.sub.2 gas and
another gas in their characteristics such as ozone layer
destructivity, carcinogenicity and inflammability are shown in FIG.
1.
[0027] A CH.sub.2Cl.sub.2 gas used in the present invention is,
different from a CCl.sub.4 gas or a CHF gas, free from the problem
of ozone layer destruction and is, different from a CHCl.sub.3 gas,
has no carcinogenicity. There is accordingly a high possibility of
it being supplied stably in future. Different from a CH gas or
another CHCl gas, it is flame retardant so that it can be added
without dilution. Different from a CHF gas or an N.sub.2 gas, it
does not contain elements such as N and F, which tends to make it
free from the problem of particle contamination. Different from a
CHBr gas, it does not contain Br so that it is presumed not to be
troubled much with the problem in removability of a side-wall
protection film.
[0028] Generation of particles was studied using a CH.sub.4 gas
diluted to 8% with Ar (which will hereinafter be described as "PR
gas"), a CH.sub.2Cl.sub.2 gas, a CH.sub.2Br.sub.2 gas, a CHF.sub.3
gas and an N.sub.2 gas, respectively. In FIG. 2, shown is the
relationship--when a wafer having a metal material thereon is
etched with a plasma of each of various gases and a
Cl.sub.2-BCl.sub.3 mixture gas--between a ratio of failure by
particle contamination and the number of wafers treated. It is
however to be noted that during etching, plasma cleaning in a
chamber is conducted by using O.sub.2 gas plasma discharge or
Cl.sub.2 gas plasma discharge.
[0029] When the number of the wafers etched with a plasma of a
mixture gas containing an N.sub.2 gas or a CHF.sub.3 gas is 500,
the failure ratio reaches 90% or greater. So this gas is not suited
for mass production. When the number of the wafers treated with a
plasma of a mixture gas containing a CH.sub.2Cl.sub.2 gas, a
CH.sub.2Br.sub.2 gas or a PR gas is 5000, on the other hand, the
failure ratio is suppressed to less than 10%, suggesting that this
gas is suited for mass production.
[0030] In the next place, shape control was studied. A PR gas, a
CH.sub.2Cl.sub.2gas, or a CH.sub.2Br.sub.2gas suited for mass
production was selected as an additive gas, and a sample was etched
using a plasma of a mixture gas containing the additive gas, a
Cl.sub.2 gas and a BCl.sub.3 gas. The sample employed here was a
wafer which had a diameter of 8 inches, had thereover TiN, Al and
TiN films successively stacked one after another, and had a resist
film formed over these stacked films. In FIG. 3, the relationship
among a CD shift relative to the resist mask, an etching rate and
kinds of gases added. In this diagram, an etching rate (nm/min) is
indicated by a circle.
[0031] When the partial pressure of a Cl.sub.2 gas is low, a
decrease in an etching rate occurs. It is necessary to maintain the
partial pressure of a Cl.sub.2 gas at about 0.5 Pa or greater in
order to maintain an etching rate at 600 nm/min or greater which is
sufficient for practical use. Since high treating pressures cause
an increase in the CD shift, it is necessary to suppress the
treating pressure to 1.5 Pa or less in order to attain a
practically usable CD shift of 100 nm or less. In addition, it is
necessary to add a shape controlling gas in an amount of about 20%
of the Cl.sub.2 gas in order to suppress side etching.
[0032] In a PR gas, the shape controlling CH.sub.4 gas has been
diluted to 8%, so that the PR gas should be added in an amount of
about 2.5 times as much as that of the Cl.sub.2 gas in order to
control the shape. This increases the treating pressure to about
3.5 times as much as the partial pressure of the Cl.sub.2 gas,
making it difficult to attain both a sufficient etching rate and a
sufficient CD shift. Addition of a PR gas, which has been adjusted
to maintain an etching rate at a practically usable level of 600
nm/min as shown in FIG. 3, increased a CD shift as large as several
hundred nm or greater.
[0033] A CH.sub.2Cl.sub.2 gas or CH.sub.2Br.sub.2 gas is, on the
other hand, usable without diluting a shape controlling gas. Even
by the addition of a 20% shape controlling gas, the treating
pressure can be suppressed to about 1.2 times as much as that of
the Cl.sub.2 partial pressure. This makes it possible to attain
both a sufficient etching rate and sufficient CD shift within a
wide range from 0.6 Pa to 1.5 Pa. As a result, a CH.sub.2Cl.sub.2
gas and a CH.sub.2Br.sub.2 gas can suppress the CD shift to about
10 nm while maintaining an etching rate at a practically usable
level of 800 nm/min.
[0034] As described above, it has been found that a
CH.sub.2Cl.sub.2 gas and a CH.sub.2Br.sub.2 gas are much superior
in shape controllability to a PR gas.
[0035] After removal of the resist mask by a plasma of a CF.sub.4
and O.sub.2 mixture gas from the sample etched with each of a
CH.sub.2Cl.sub.2 gas and CH.sub.2Br.sub.2 gas, the resulting wafer
was washed with a mixed solution of acetic acid and aqueous
ammonia. The cross-sectional views of the sample after washing are
shown in FIGS. 4 and 5.
[0036] As is apparent from FIG. 4 wherein the shape after etching
with a CH.sub.2Br.sub.2 gas is illustrated, a side-wall protection
film 4 remains on the side walls of the barrier TiN layer 1, Al
layer 2 and cap TiN layer 3 and over the cap TiN layer 3,
suggesting that the side-wall protection film cannot be removed
completely by the washing after etching. Indicated at numeral 5 in
these diagrams is a semiconductor substrate.
[0037] As is apparent from FIG. 5 wherein the shape after etching
with a CH.sub.2Cl.sub.2 gas is illustrated, the side-wall
protection film is removed completely from the side walls of the
barrier TiN layer 1, Al layer 2 and cap TiN layer 3 and from the
upper surface of the cap TiN layer 3, suggesting that this gas is
superior in removability of the side-wall protection film. For the
removal of the resist mask, a plasma of a CF.sub.4 and O.sub.2
mixture gas was employed. Similar results are available insofar as
the plasma is a mixture gas containing an F element and O
element.
[0038] It has been understood from the above-described results that
use of a CH.sub.2Cl.sub.2 gas as an additive gas for shape control
is desired from four viewpoints, that is, stable gas supply,
suitability for mass production, shape controllability and
removability of side-wall protection films.
EXAMPLE 2
[0039] In etching of a stacked structure of a TiN film, an Al film
and a TiN film formed over a semiconductor substrate, the amount of
a CH.sub.2Cl.sub.2 gas is suppressed to 0 to 4% upon etching of the
TiN film and it is increased to 5 to 30% only during etching of the
Al film which needs shape control. This makes it possible to
decrease the CD shift to half of that in the case of etching
without changing the amount of the gas.
EXAMPLE 3
[0040] FIG. 6 illustrates an application example of the etching
method of the present invention to a multilayer interconnection
step of a semiconductor device. In this interconnection step, a via
hole is made by successively carrying out (1) deposition of a
silicon oxide film (TEOS) by chemical vapor deposition (CVD), (2)
formation of a resist mask by photolithography and (3) etching of
TEOS by using a plasma of a CF gas along the resist mask. In the
resulting via hole, (4) TiN is embedded by sputtering, followed by
(5) embedding of tungsten (W) by CVD.
[0041] Excessive W and TiN deposited over the TEOS surface by the
above-described embedding step is (6) removed by chemical
mechanical polishing (CMP) and then, (7) washed with a chemical
solution. After successive deposition, over the TEOS surface after
CMP, of (8) TiN by sputtering, (9) Al--Cu mixed crystals by
sputtering, (10) TiN by sputtering, (11) TEOS by CVD, and (12) SiON
by CVD, (13) the resist mask is patterned by lithography. Along
this resist mask, TEOS is (14) etched by a CF gas to form a TEOS
mask.
[0042] Along the TEOS mask thus formed, the TiN, Al--Cu and TiN
films thus stacked are etched using a plasma of a mixture gas of
Cl.sub.2, BCl.sub.3 and CH.sub.2Cl.sub.2 according to the present
invention. After etching, the remaining resist mask is (16) removed
by a plasma of a mixture gas of O.sub.2 and CF.sub.4, followed by
(17) washing with a chemical solution.
[0043] After (18) deposition of an insulating material over the
washed sample by CVD, the resulting sample is (19) planarized by
CMP and then (20) washed with a chemical solution. The resulting
sample is subjected to the above-described steps starting from (1)
in repetition, whereby a multilayer interconnection is formed.
[0044] The yield of the semiconductor device produced in accordance
with the method of the present invention which uses a
CH.sub.2Cl.sub.2 gas for the etching step (15) was 90%. The yield
of the semiconductor device produced using a PR gas in the step of
(15) was, on the other hand, only 50% owing to disconnection
failure or short-circuit failure. The yield lowered to 40% by the
use of a CH.sub.2Br.sub.2 gas, because of high contact resistance.
The yield drastically decreased to 10% by the use of a CHF.sub.3
gas owing to particle contamination.
[0045] As described above, in the multi-layer interconnection step
including an aluminum film, use of a plasma of a mixture gas of
Cl.sub.2, BCl.sub.3 and CH.sub.2Cl.sub.2 for etching of a metal
interconnection makes it possible to fabricate a semiconductor
device having a high reliability.
EXAMPLE 4
[0046] As illustrated in FIG. 7A, a sample having various line and
space patterns formed using a resist mask 6 over a stacked
structure of a barrier TiN film 1, an Al film 2 and a cap TIN film
3 over a semiconductor substrate 5 was etched using a plasma of a
mixture gas containing Cl.sub.2, BCl.sub.3 and an undercut
preventive gas.
[0047] One example of the etched shape is shown in FIG. 7B.
[0048] Patterns of a wide pitch can be etched vertically, whereas
those of a fine pitch have undercut appeared on the Al film 2.
[0049] In FIG. 8 illustrated are the results of the undercut
conditions in the patterns formed at wiring pitches of 1000, 500,
300, 260 and 200 when a PR gas or CH.sub.2Cl.sub.2 gas was used as
an additive gas. At wiring pitches of 500 nm or greater, no
undercut was observed irrespective of the kind of the additive gas.
At wiring pitches less than 500 nm, undercut appeared when a PR gas
was added, while it was suppressed when a CH.sub.2Cl.sub.2 gas was
added. This suggests that addition of a CH.sub.2Cl.sub.2 gas has
marked effects on the patterns formed at a wiring pitch less than
500 nm.
EXAMPLE 5
[0050] A difference in the CD shift between the pattern formed at a
wiring pitch of 1000 nm and that formed at a wiring pitch of 200 nm
was measured using the sample obtained in Example 4. As a result,
the difference in CD shift was as large as 200 nm in the case of PR
gas addition, whereas it was as small as 20 nm in the case of
CH.sub.2Cl.sub.2 gas addition. This suggests that addition of a
CH.sub.2Cl.sub.2 gas is effective for etching of a sample on which
patterns different in wiring pitch exist on the same wafer.
EXAMPLE 6
[0051] Upon preparation of the sample of Example 4, a
CH.sub.2Cl.sub.2 gas having a purity of 99.9% was added, resulting
in problems of foreign matters and metal contamination. It has been
understood that such problems do not occur when a CH.sub.2Cl.sub.2
gas having a purity of 99.99% or greater is used.
EXAMPLE 7
[0052] The sample as illustrated in FIG. 7A was etched using a
plasma of a mixture gas containing a Cl.sub.2 gas, a BCl.sub.3 gas
and an undercut preventive gas. As this undercut preventive gas, a
CH.sub.2Cl.sub.2 gas diluted with Ar was employed. In FIG. 9, the
relationship between the CD shift of the patterns formed at a
wiring pitch of 1000 nm and a dilution ratio of CH.sub.2Cl.sub.2 is
illustrated.
[0053] The CD shift increases with a dilution ratio. At a mole
concentration of CH.sub.2Cl.sub.2 not less than 10%, however, CD
shift is smaller compared with the case where a PR gas is added. It
has been found that when a CH.sub.2Cl.sub.2 is diluted with Ar to
give a mole concentration of 10% to 100%, the shape controllability
is higher, compared with the use of a conventional gas. For
dilution, Ar was employed here, but there is no limitation imposed
on the dilution gas insofar as it is inert.
EXAMPLE 8
[0054] The sample obtained in FIG. 7A was etched with a mixture gas
of Cl.sub.2, BCl.sub.3 and CH.sub.2Cl.sub.2 by using each of an
etching system which generates a plasma by using an UHF-range
electromagnetic wave (300 MHz to 1 GHz) (which system will
hereinafter be called "UHF plasma etching system), an etching
system which generates a plasma by using an electromagnetic
microwave (2.45 GHz) (which system will hereinafter be called
"microwave etching system", and an etching system which generates a
plasma by using an RF-range electromagnetic wave (13.56 MHz or
less) (which system will hereinafter be called "ICP plasma etching
system).
[0055] As a result, the UHF plasma etching system did not cause
undercut easily compared with the microwave plasma etching system
or ICP etching system. In the microwave plasma etching system or
ICP etching system, a plasma density is high and this facilitates
dissociation of CH.sub.2Cl.sub.2 into the corresponding atoms so
that effects of gas addition are reduced by half. It is presumed
that in the UHF plasma etching system, on the other hand, a plasma
density is low and this disturbs dissociation of a
CH.sub.2Cl.sub.2gas, effects of the additive gas tend to appear
readily.
EXAMPLE 9
[0056] In Example 3, the resist was removed in the step 16 after
etching of the stacked films of TiN, Al--Cu and TiN in the step 15.
In this Example, after etching of SION and TEOS in the step 14, the
resist removal of the step 16 is conducted, followed by etching of
the stacked films of TiN, Al--Cu, and TiN of the step 15. Even
after such a permutation, similar results are available.
[0057] In Example 3, TEOS was deposited over TiN in the step 11.
Similar results are available even if deposition of SiON over TiN
in the step 12 is conducted without the step 11.
[0058] As described above, a highly reliable semiconductor device
can be manufactured by using the manufacturing method of the
present invention adopting an etching method which uses a gas
suppliable stably also in future, is reduced in the problem of
particle contamination, is free from the problem in the removal of
a side-wall protection film and exhibits high shape controlling
capacity.
* * * * *