U.S. patent application number 09/106007 was filed with the patent office on 2001-11-08 for method for making an insulating film.
Invention is credited to HARA, MASAKI.
Application Number | 20010039125 09/106007 |
Document ID | / |
Family ID | 15967586 |
Filed Date | 2001-11-08 |
United States Patent
Application |
20010039125 |
Kind Code |
A1 |
HARA, MASAKI |
November 8, 2001 |
METHOD FOR MAKING AN INSULATING FILM
Abstract
In a method for manufacturing an insulating film using a fluid
source material without inviting corrosion of metal wiring or the
problem of poisoned via, after making a SiO.sub.2 film as a base
layer on an Si substrate defining an uneven surface with an Al
alloy wiring by plasma CVD using SiH.sub.4 and N.sub.2O, and
further making an inter-layer insualting film having a fluidity on
the SiO.sub.2 film by low pressure CVD using SiH.sub.4 or
organosilane and H.sub.2O.sub.2, O.sub.2 plasma processing is
applied to the inter-layer insulating film. After that, a SiO.sub.2
film as a cap layer is made on the inter-layer insulating film by
plasma CVD using SiH.sub.4 and N.sub.2O. Rapid thermal annealing
using lamp heating or O.sub.3 annealing may be done in lieu of
O.sub.2 plasma processing.
Inventors: |
HARA, MASAKI; (KANAGAWA,
JP) |
Correspondence
Address: |
SONNENSCHEIN NATH & ROSENTHAL
P.O. BOX 061080
WACKER DRIVE STATION
CHICAGO
IL
60606-1080
US
|
Family ID: |
15967586 |
Appl. No.: |
09/106007 |
Filed: |
June 29, 1998 |
Current U.S.
Class: |
438/763 ;
257/E21.576 |
Current CPC
Class: |
H01L 21/76826 20130101;
H01L 21/76801 20130101; H01L 21/76828 20130101; H01L 21/76834
20130101 |
Class at
Publication: |
438/763 |
International
Class: |
H01L 021/336 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 30, 1997 |
JP |
P09-173810 |
Claims
What is claimed is:
1. A method for making an insulating film configured to form the
insulating film on a substrate having an uneven surface by using a
fluid source material so as to level the unevenness, comprising the
steps of: forming a first insulating film having a fluidity on said
substrate by using a fluid source material; applying plasma
processing onto said first insulating film; and forming a second
insulating not having a fluidity on said first insulating film
after said plasma processing.
2. The method for making an insulating film according to claim 1
further comprising the step of annealing after the step of forming
the first insulating film before the step of applying the plasma
processing.
3. The method for making an insulating film according to claim 1
wherein said first insulating film is formed by low pressure CVD
using SiH.sub.4 or organosilane and H.sub.2O.sub.2 as source
materials.
4. The method for making an insulating film according to claim 1
wherein a gas of molecules containing oxygen as the matrix atoms
thereof and not containing nitrogen as the matrix atoms thereof is
used for said plasma processing.
5. A method for making an insulating film configured to form the
insulating film on a substrate having an uneven surface by using a
fluid source material so as to level the unevenness, comprising the
steps of: forming a first insulating film having a fluidity on said
substrate by using a fluid source material; applying rapid thermal
annealing by lamp heating onto said first insulating film; and
forming a second insulating not having a fluidity on said first
insulating film after said rapid thermal annealing.
6. The method for making an insulating film according to claim 5
wherein said first insulating film is formed by low pressure CVD
using SiH.sub.4 or organosilane and H.sub.2O.sub.2 as source
materials.
7. A method for making an insulating film configured to form the
insulating film on a substrate having an uneven surface by using a
fluid source material so as to level the unevenness, comprising the
steps of: forming a first insulating film having a fluidity on said
substrate by using a fluid source material; applying ozone
processing onto said first insulating film; and forming a second
insulating not having a fluidity on said first insulating film
after said ozonization.
8. The method for making an insulating film according to claim 7
wherein said first insulating film is formed by low pressure CVD
using SiH.sub.4 or organosilane and H.sub.2O.sub.2 as source
materials.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a method for making an insulating
film particularly suitable for use in making an inter-layer
insulating film in a semiconductor device.
[0003] 2. Description of the Related Art
[0004] In a process of manufacturing a semiconductor device, a
method for making an inter-layer insulating film using a fluid
source material is often used to level the surface of a substrate
by smoothing unevenness made by wiring or the like. Such an
inter-layer insulating film contains much moisture (H.sub.2O) and
is highly fluid.
[0005] In conventional techniques, a non-fluid cap layer was formed
directly on a fluid inter-layer insulating film containing much
H.sub.2O by plasma CVD (for example, 1995 Dry Process Symposium,
pp.261-268) to prevent cracks in the fluid inter-layer insulating
film containing H.sub.2O during post-annealing. Typically used as
the cap layer was a SiO.sub.2 film made of SiH.sub.4 and N.sub.2O
by plasma CVD because N.sub.2O was more preferable than O.sub.2 as
the source material of oxygen in reducing the number of particles
produced during the process.
[0006] However, the SiO.sub.2 cap layer made of SiH.sub.4 and
N.sub.2O by plasma CVD invited corrosion of metal wiring and
so-called poisoned via (a kind of defects of via holes (connection
holes) formed in inter-layer insulating films), among others.
OBJECT AND SUMMARY OF THE INVENTION
[0007] It is therefore an object of the invention to provide a
method for making an insulating film free from problems such as
corrosion of metal wiring and poisoned via even when a fluid source
material is used to make the insulating film.
[0008] The Inventor made researches to overcome the above-mentioned
problems involved in the conventional techniques as summarized
below.
[0009] The Inventor has found through various experiments that
NH.sub.3 is produced in vapor by plasma in the process of making a
SiO.sub.2 film by plasma CVD using SiH.sub.4 and N.sub.2O as source
materials. Under the condition, if the inter-layer insulating film
underlying the SiO.sub.2 film contains H.sub.2O and has a fluidity,
then NH.sub.3 produced in vapor is incorporated (absorbed) into the
underlying inter-layer insulating film. NH.sub.3 incorporated into
the underlying inter-layer insulating film is released from the
film when the inter-layer insulating film is heated or etched in a
later process, and probably cause the problems of corrosion of
metal wiring and poisoned via.
[0010] Therefore, in order to prevent these problems, it is
important to take measures to prevent that NH.sub.3 produced in
vapor in the process of making the SiO.sub.2 film by plasma CVD
using SiH.sub.4 and N.sub.2O as source materials is not
incorporated in the underlying inter-layer insulating film. For
this purpose, it is effective to remove H.sub.2O from the surface
of the underlying inter-layer insulating film and to cure the
surface prior to the process of making the SiO.sub.2 film. The
present invention has been made through these researches by the
Inventor.
[0011] According to a first aspect of the invention, there is
provided a method for making an insulating film configured to form
the insulating film on a substrate having an uneven surface by
using a fluid source material so as to level the unevenness,
comprising the steps of:
[0012] forming a first insulating film having a fluidity on the
substrate by using a fluid source material;
[0013] applying plasma processing onto the first insulating film;
and
[0014] forming a second insulating not having a fluidity on the
first insulating film after the plasma processing.
[0015] According to a second aspect of the invention, there is
provided a method for making an insulating film configured to form
the insulating film on a substrate having an uneven surface by
using a fluid source material so as to level the unevenness,
comprising the steps of:
[0016] forming a first insulating film having a fluidity on the
substrate by using a fluid source material;
[0017] applying rapid thermal annealing by lamp heating onto the
first insulating film; and
[0018] forming a second insulating not having a fluidity on the
first insulating film after the rapid thermal annealing.
[0019] According to a third aspect of the invention, there is
provided a method for making an insulating film configured to form
the insulating film on a substrate having an uneven surface by
using a fluid source material so as to level the unevenness,
comprising the steps of:
[0020] forming a first insulating film having a fluidity on the
substrate by using a fluid source material;
[0021] applying ozone processing onto the first insulating film;
and
[0022] forming a second insulating not having a fluidity on the
first insulating film after the ozone processing.
[0023] In the first aspect of the invention, the step of annealing
the structure may be added after making the first insulating film
and prior to plasma processing to previously cure the entirety of
the first insulating film to a certain extent in order to ensure
that the first insulating film be more effectively cured by
subsequent plasma processing. The annealing temperature is not
higher than 500.degree. C., about 350.degree. C., for example, when
Al alloy wiring is used. The annealing may be done either under
vacuum or atmospheric pressure, but can be done more conveniently
within a chamber used for the plasma processing. For plasma
processing, it is preferable to use a gas of molecules, such as
O.sub.2 gas, containing oxygen as its matrix atoms and not
containing nitrogen as its matrix atoms.
[0024] In the present invention, the first insulating film having a
fluidity is typically made by low pressure CVD using SiH.sub.4 or
organosilane and H.sub.2O.sub.2 as source materials.
[0025] According to the invention, having the above-summarized
construction configured to execute plasma processing, rapid thermal
annealing by using lamp heating or ozone processing after making a
first insulating film having a fluidity, H.sub.2O can be removed
from the surface of the first insulating film due to dehydrated
condensation, and the film can be hardened. Therefore, even when
NH.sub.3 is produced in vapor by plasma while a SiO.sub.2 film is
stacked on the first insulating film by plasma CVD using SiH.sub.4
and N.sub.2O as source material gases, NH.sub.3 can be prevented
from being incorporated into the first insulating film. As a
result, corrosion of metal wiring or the problem of poisoned via
can be prevented.
[0026] The above, and other, objects, features and advantage of the
present invention will become readily apparent from the following
detailed description thereof which is to be read in connection with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIGS. 1A through 1E are cross-sectional views for explaining
a method for making an inter-layer insulating film according to the
first embodiment of the invention;
[0028] FIGS. 2A through 2C are schematic diagrams for explaining
effects of O.sub.2 plasma processing executed in the method for
making the inter-layer insulating film according to the first
embodiment of the invention;
[0029] FIGS. 3A through 3E are cross-sectional views for explaining
a method for making an inter-layer insulating film according to the
second embodiment of the invention; and
[0030] FIGS. 4A through 4E are cross-sectional views for explaining
a method for making an inter-layer insulating film according to the
third embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] Explained below are embodiments of the invention with
reference to the drawings. In all figures illustrating the
embodiments of the invention, the same or equivalent elements are
labeled with common reference numerals.
[0032] FIGS. 1A through 1E show the method for making an
inter-layer insulating film according to the first embodiment of
the invention.
[0033] In the embodiment shown here, an Al alloy wiring 2 is formed
on a Si substrate 1 having formed a device and covered with an
inter-layer insulating film previously as shown in FIG. 1A.
[0034] Next, as shown in FIG. 1B, a non-fluid SiO.sub.2 film 3 is
formed as a base layer on the Si substrate 1 by plasma CVD using
SiH.sub.4 and N.sub.2O, for example, as source materials.
[0035] Next, as shown in FIG. 1C, a fluid inter-layer insulating
film 4 is formed by low pressure CVD using monomethyl silane
(Si(CH.sub.3)H.sub.3) and H.sub.2O.sub.2, for example, as source
materials. The fluid inter-layer insulating film 4 contains silanol
polymer as its major component, and contains much H.sub.2O in the
film (1995 Dry Process Symposium, pp. 261-268).
[0036] Next, as shown in FIG. 1D, the surface of the fluid
inter-layer insulating film 4 is processed with O.sub.2 plasma to
cure the surface of the inter-layer insulating film 4. The O.sub.2
plasma processing promotes hydrated condensation of silanol
(Si(OH).sub.4) along the surface of the inter-layer insulating film
4, and changes the surface of the inter-layer insulating film 4
substantially free from H.sub.2O.
[0037] Next, as shown in FIG. 1E, a non-fluid SiO.sub.2 film 5 is
formed as a cap layer on the inter-layer insulating film 4 by
plasma CVD using SiH.sub.4 and N.sub.2O, for example, as source
materials. Since substantially no H.sub.2O is contained in the
surface of the inter-layer insulating film 4, NH.sub.3 produced in
vapor by plasma is not incorporated into the inter-layer insulating
film 4 in the process of stacking the SiO.sub.2 film 5 as the cap
layer.
[0038] After that, the inter-layer insulating film 4 is cured by
post-annealing.
[0039] As a result, an inter-layer insulating film of a
triple-layered structure of the inter-layer insulating film 4,
underlying SiO.sub.2 film 3 as the base layer and overlying
SiO.sub.2 film 5 as the cap layer is obtained.
EXAMPLE
[0040] As shown in FIG. 1A, an Al alloy wiring 1, which is 0.65
.mu.m height and 0.4 .mu.m wide, is made on the Si substrate 1.
[0041] Next, as shown in FIG. 1B, a SiO.sub.2 film 3 of the
thickness of 0.1 .mu.m is formed as a base layer by plasma CVD,
using N.sub.2O, SiH.sub.4 and N.sub.2, setting their flow rates to
3000 SCCM, 120 SCCM and 1000 SCCM, respectively, under the reaction
pressure of 1.2 Torr (1200 mTorr), setting the substrate
temperature to 350.degree. C.
[0042] Next, as shown in FIG. 1C, a fluid inter-layer insulating
film 4 of the thickness of 0.8 .mu.m is formed by low pressure CVD,
using Si(CH.sub.3)H.sub.3 and vapor phase H.sub.2O.sub.2 and
N.sub.2, setting their flow rates to 100 SCCM, 0.7 g/min and 500
SCCM, respectively, under the reaction pressure of 1 Torr, setting
the substrate temperature to 0.degree. C.
[0043] Next, as shown in FIG. 1D, heating the Si substrate to
350.degree. C., using a mixed gas of O.sub.2 and Ar, generating
O.sub.2 plasma under the pressure of 1.2 Torr and the RF power of
500 W, O.sub.2 plasma processing of the inter-layer insulating film
4 is executed for three minutes. The flow rate of O.sub.2 is set to
2000 SCCM, and the flow rate of Ar is set to 1000 SCCM. The O.sub.2
plasma processing resulted in curing the surface of the inter-layer
insulating film 4 and in removing H.sub.2O from the surface
portion.
[0044] Next, as shown in FIG. 1E, a SiO.sub.2 film 5 as a cap layer
is stacked to the thickness of 0.3 .mu.m by plasma CVD, using
N.sub.2O, SiH.sub.4 and N.sub.2, setting their flow rates to 2500
SCCM, 120 SCCM and 1000 SCCM, the reaction pressure to 0.8 Torr
(800 mTorr), and the substrate temperature to 350.degree. C.
[0045] After that, the product is post-annealed for 30 minutes in a
N.sub.2 atmosphere to cure the inter-layer insulating film 4.
[0046] The inter-layer insulating film having a triple-layered
structure, thus obtained, did not contain a detrimental amount of
residual gas (NH.sub.3 gas, or the like) which might cause a
problem in the process and exhibited good characteristics.
[0047] Here is shown evidential data on the effects obtained by
O.sub.2 plasma processing of the fluid inter-layer insulating film
4. FIGS. 2A through 2C show values by TDS (Thermal Desorption
Spectroscopy) measurement on samples treated and not treated by
O.sub.2 plasma processing after making the fluid inter-layer
insulating film 4 by low pressure CVD. Both samples were prepared
by making the SiO.sub.2 film 5 after O.sub.2 plasma processing and
by thereafter post-annealing for 30 minutes in a N.sub.2 atmosphere
at 400.degree. C., and were measured by TDS measurement. For
O.sub.2 plasma processing, the flow rate of O.sub.2 was set to 800
SCCM, the pressure to 250 mTorr, RF power to 500 W, substrate
temperature to 0.degree. C., and processing time to 10 minutes.
FIGS. 2A, 2B and 2C are data upon the mass number of ions to be
measured being 18 (corresponding to H.sub.2O), 17 (corresponding to
NH.sub.3 and OH) and 16 (corresponding to NH.sub.2 and O),
respectively.
[0048] Comparing FIG. 2A and 2B, as to samples without O.sub.2
plasma processing, the ratio of the ionic strength of the mass
number 18 relative to the ionic strength of the mass number 17 is
much larger than the value when H.sub.2O alone exists as a kind of
gas, and this strongly indicates that another kind of gas with the
mass number 17, NH.sub.3, exists. In contrast, as to samples
treated by without O.sub.2 plasma processing, the ratio of the
ionic strength of the mass number 17 relative to the ionic
intensity of the mass number 18 is nearer to the value when
H.sub.2O alone exists as a kind of gas.
[0049] These phenomena indicate that, during the process of making
the SiO.sub.2 film 3 by plasma CVD, substantially no NH.sub.3
produced in vapor by plasma is not incorporated into the
inter-layer insulating film 4.
[0050] This means that O.sub.2 plasma processing effectively
removes H.sub.2O from the surface of the fluid inter-layer
insulating film 4.
[0051] As explained above, according to the first embodiment,
substantially all H.sub.2O can be removed from the surface of the
inter-layer insulating film 4 by treating the inter-layer
insulating film 4 by O.sub.2 plasma processing after making the
inter-layer insulating film 4 as a fluid film. Therefore, even when
the SiO.sub.2 film 5 is made as a cap layer directly on the
inter-layer insulating film 4 by plasma CVD, NH.sub.3 produced in
vapor by plasma during the process is never incorporated into the
inter-layer insulating film 4. As a result, corrosion of the Al
alloy wiring 2 or the problem of poisoned via do not occur.
[0052] FIGS. 3A through 3E show a method for making an inter-layer
insulating film according to the second embodiment of the
invention.
[0053] In the embodiment shown here, the Al alloy wiring 2 is
formed on the Si substrate 1 having formed a device and covered
with an inter-layer insulating film previously as shown in FIG.
3A,.
[0054] Next, as shown in FIG. 3B, a non-fluid SiO.sub.2 film 3 is
made as a base layer on the Si substrate 1 by plasma CVD using
SiH.sub.4 and N.sub.2O, for example, as source materials.
[0055] Next, as shown in FIG. 3C, a fluid inter-layer insulating
film 4 is made by low pressure CVD using Si(CH.sub.3)H.sub.3 and
H.sub.2O.sub.2, for example, as source materials. The steps
heretofore are the same as those of the first embodiment.
[0056] Next, as shown in FIG. 3D, the surface of the inter-layer
insulating film 4 is heated by lamp heating, namely by using
radiant heat from a lamp heater, to cure the surface of the
inter-layer insulating film 4 by rapid thermal annealing in a short
time. By the rapid thermal annealing, dehydrated condensation of
Si(OH).sub.4 is promoted along the surface of the inter-layer
insulating film 4, and the surface of the inter-layer insulating
film 4 is changed substantially free from H.sub.2O.
[0057] Next, as shown in FIG. 3E, a non-fluid SiO.sub.2 film 5 is
made as a cap layer on the inter-layer insulating film 4 by plasma
CVD using SiH.sub.4 and N.sub.2O, for example, as source materials.
In this case, since the surface of the inter-layer insulating film
4 contains substantially no H.sub.2O, it does not incorporate
NH.sub.3 produced in vapor by plasma during the process of making
the SiO.sub.2 film 5 as the cap layer.
[0058] After that, the inter-layer insulating film 4 is cured by
post-annealing.
[0059] By the process explained above, the inter-layer insulating
film of a triple-layered structure of the inter-layer insulating
film 4, underlying SiO.sub.2 film 3 as the base layer and overlying
SiO.sub.2 film 5 as the cap layer is obtained.
EXAMPLE
[0060] As shown in FIG. 3A, an Al alloy wiring 1, which is 0.65
.mu.m height and 0.4 .mu.m wide, is made on the Si substrate 1.
[0061] Next, as shown in FIG. 3B, a SiO.sub.2 film 3 of the
thickness of 0.1 .mu.m is formed as a base layer by plasma CVD,
using N.sub.2O, SiH.sub.4 and N.sub.2, setting their flow rates to
3000 SCCM, 120 SCCM and 1000 SCCM, respectively, under the reaction
pressure of 1.2 Torr (1200 mTorr), setting the substrate
temperature to 350.degree. C.
[0062] Next, as shown in FIG. 3C, an inter-layer insulating film 4
of the thickness of 0.8 .mu.m is formed by low pressure CVD, using
Si(CH.sub.3)H.sub.3 and vapor phase H.sub.2O.sub.2 and N.sub.2,
setting their flow rates to 100 SCCM, 0.7 g/min and 500 SCCM,
respectively, under the reaction pressure of 1 Torr, setting the
substrate temperature to 0.degree. C.
[0063] Next, as shown in FIG. 3D, heating the Si substrate to
350.degree. C. under vacuum, rapid thermal annealing by lamp
heating is executed for 60 seconds. At that time, the surface
temperature of the Si substrate 1 was about 500.degree. C. By rapid
thermal annealing using lamp heating, the surface of the
inter-layer insulating film 4 cured, and the surface portion was
changed free from H.sub.2O.
[0064] Next, as shown in FIG. 3E, a SiO.sub.2 film 5 as a cap layer
is stacked to the thickness of 0.3 .mu.m by plasma CVD, using
N.sub.2O, SiH.sub.4 and N.sub.2, setting their flow rates to 2500
SCCM, 120 SCCM and 1000 SCCM, the reaction pressure to 0.8 Torr
(800 mTorr), and the substrate temperature to 350.degree. C.
[0065] After that, the product is post-annealed for 30 minutes in a
N.sub.2 atmosphere to cure the inter-layer insulating film 4.
[0066] The inter-layer insulating film having a triple-layered
structure, thus obtained, did not contain a detrimental amount of
residual gas (NH.sub.3 gas, or the like) which might cause a
problem in the process and exhibited good characteristics.
[0067] As explained above, according to the second embodiment,
substantially all H.sub.2O can be removed from the surface of the
inter-layer insulating film 4 by treating the surface of the
inter-layer insulating film 4 by rapid thermal annealing by lamp
heating after making the inter-layer insulating film 4 as a fluid
film. Therefore, in the same manner as the first embodiment, even
when the SiO.sub.2 film 5 is made as a cap layer directly on the
inter-layer insulating film 4 by plasma CVD, NH.sub.3 produced in
vapor by plasma during the process is never incorporated into the
inter-layer insulating film 4. As a result, corrosion of the Al
alloy wiring 2 or the problem of poisoned via do not occur.
[0068] FIGS. 4A through 4E show a method for making an inter-layer
insulating film according to the third embodiment of the
invention.
[0069] In the embodiment shown here, the Al alloy wiring 2 is
formed on the Si substrate 1 having formed a device and covered
with an inter-layer insulating film previously as shown in FIG.
4A.
[0070] Next, as shown in FIG. 4B, a non-fluid SiO.sub.2 film 3 is
made as a base layer on the Si substrate 1 by plasma CVD using
SiH.sub.4 and N.sub.2O, for example, as source materials.
[0071] Next, as shown in FIG. 4C, a fluid inter-layer insulating
film 4 is made by low pressure CVD using Si(CH.sub.3)H.sub.3 and
H.sub.2O.sub.2, for example, as source materials. The steps
heretofore are the same as those of the first embodiment.
[0072] Next, as shown in FIG. 4D, the Si substrate 1 is set in a
chamber 6 and heated while introducing O.sub.3 into the chamber to
cure the surface of the inter-layer insulating film 4 by O.sub.3
annealing of the inter-layer insulating film 4. By the O.sub.3
annealing, dehydrated condensation of Si(OH).sub.4 is promoted
along the surface of the inter-layer insulating film 4, and the
surface of the inter-layer insulating film 4 is changed
substantially free from H.sub.2O.
[0073] Next, as shown in FIG. 4E, a non-fluid SiO.sub.2 film 5 is
made as a cap layer on the inter-layer insulating film 4 by plasma
CVD using SiH.sub.4 and N.sub.2O, for example, as source materials.
In this case, since the surface of the inter-layer insulating film
4 contains substantially no H.sub.2O, it does not incorporate
NH.sub.3 produced in vapor by plasma during the process of making
the SiO.sub.2 film 5 as the cap layer.
[0074] After that, the inter-layer insulating film 4 is cured by
post-annealing.
[0075] By the process explained above, the inter-layer insulating
film of a triple-layered structure of the inter-layer insulating
film 4, underlying SiO.sub.2 film 3 as the base layer and overlying
SiO.sub.2 film 5 as the cap layer is obtained.
EXAMPLE
[0076] As shown in FIG. 4A, an Al alloy wiring 1, which is 0.65
.mu.m height and 0.4 .mu.m wide, is made on the Si substrate 1.
[0077] Next, as shown in FIG. 4B, a SiO.sub.2 film 3 of the
thickness of 0.1 .mu.m is formed as a base layer by plasma CVD,
using N.sub.2O, SiH.sub.4 and N.sub.2, setting their flow rates to
3000 SCCM, 120 SCCM and 1000 SCCM, respectively, under the reaction
pressure of 1.2 Torr (1200 mTorr), setting the substrate
temperature to 350.degree. C.
[0078] Next, as shown in FIG. 4C, a fluid inter-layer insulating
film 4 of the thickness of 0.8 .mu.m is formed by low pressure CVD,
using Si(CH.sub.3)H.sub.3 and vapor phase H.sub.2O, and N.sub.2,
setting their flow rates to 100 SCCM, 0.7 g/min and 500 SCCM,
respectively, under the reaction pressure of 1 Torr, setting the
substrate temperature to 0.degree. C.
[0079] Next, as shown in FIG. 4D, using a mixed gas of O.sub.2 and
He, setting their flow rates to 2 SLM and 500 SCCM , a gas
containing O.sub.3 by the concentration of 10 wt % is generated
within the chamber 6, and the pressure of the gas containing
O.sub.3 is held in 650 Torr. Under the condition, the Si substrate
is heated to 400.degree. C. and undergoes O.sub.3 annealing for
three minutes. As a result of O.sub.3 annealing conducted here, the
surface of the inter-layer insulating film 4 cured, and the surface
portion was changed free from H.sub.2O.
[0080] Next, as shown in FIG. 4E, a SiO.sub.2 film 5 as a cap layer
is stacked to the thickness of 0.3 .mu.m by plasma CVD, using
N.sub.2O, SiH.sub.4 and N.sub.2, setting their flow rates to 2500
SCCM, 120 SCCM and 1000 SCCM, the reaction pressure to 0.8 Torr
(800 mTorr), and the substrate temperature to 350.degree. C.
[0081] After that, the product is post-annealed for 30 minutes in a
N.sub.2 atmosphere to cure the inter-layer insulating film 4.
[0082] The inter-layer insulating film having a triple-layered
structure, thus obtained, did not contain a detrimental amount of
residual gas (NH.sub.3 gas, or the like) which might cause a
problem in the process and exhibited good characteristics.
[0083] As explained above, according to the third embodiment,
substantially all H.sub.2O can be removed from the surface of the
inter-layer insulating film 4 by treating the surface of the
inter-layer insulating film 4 by O.sub.3 annealing after making the
inter-layer insulating film 4 as a fluid film. Therefore, in the
same manner as the first embodiment, even when the SiO.sub.2 film 5
is made as a cap layer directly on the inter-layer insulating film
4 by plasma CVD, NH.sub.3 produced in vapor by plasma during the
process is never incorporated into the inter-layer insulating film
4. As a result, corrosion of the Al alloy wiring 2 or the problem
of poisoned via do not occur.
[0084] Having described specific preferred embodiments of the
present invention with reference to the accompanying drawings, it
is to be understood that the invention is not limited to those
precise embodiments, and that various changes and modifications may
be effected therein by one skilled in the art without departing
from the scope or the spirit of the invention as defined in the
appended claims.
[0085] For example, numerals, structures, gases, sorts of films,
processes, wiring materials, substrate materials, and so forth, are
only examples, and can be changed appropriately. Namely, although
the first to third embodiments have been explained as using an
organic source material, Si(CH.sub.3)H.sub.3, as the source
material of Si in the process of making the inter-layer insulating
film 4, any other source material of Si, such as
Si(CH.sub.3).sub.2H.sub.2, Si(CH.sub.3).sub.3H, Si(CH.sub.3).sub.4,
or the like, may be used where appropriate.
* * * * *