U.S. patent application number 11/575874 was filed with the patent office on 2008-02-14 for process for film production and semiconductor device utilizing film produced by the process.
This patent application is currently assigned to MITSUBISHI ELECTRIC CORPORATION. Invention is credited to Teruhiko Kumada, Norihisa Matsumoto, Shigeru Matsuno, Hideharu Nobutoki, Naoki Yasuda.
Application Number | 20080038585 11/575874 |
Document ID | / |
Family ID | 36202850 |
Filed Date | 2008-02-14 |
United States Patent
Application |
20080038585 |
Kind Code |
A1 |
Kumada; Teruhiko ; et
al. |
February 14, 2008 |
Process for Film Production and Semiconductor Device Utilizing Film
Produced by the Process
Abstract
The present invention provides a method of manufacturing a film
including the steps of using a compound with borazine skeleton
(preferably a compound expressed by a chemical formula (1) below
##STR1## (where R.sub.1-R.sub.6 may be identical with or different
from each other, and are each independently selected from a group
consisting of a hydrogen atom, and an alkyl group, an alkenyl group
and an alkynyl group each having a carbon number of 1-4, on
condition that at least one of R.sub.1-R.sub.6 is not the hydrogen
atom)) as a raw material, and forming the film on a substrate by
using a chemical vapor deposition method, characterized in that a
negative charge is applied to a site for placing the substrate, and
a semiconductor device utilizing a film manufactured by the method.
With the present invention, it is possible to provide a method of
manufacturing a film, which method stably provides a low dielectric
constant and a high mechanical strength over a long period of time,
reduces the amount of a gas component (outgas) emitted in heating
the film, and avoids any trouble in the device manufacturing
process.
Inventors: |
Kumada; Teruhiko; (Tokyo,
JP) ; Yasuda; Naoki; (Tokyo, JP) ; Nobutoki;
Hideharu; (Tokyo, JP) ; Matsumoto; Norihisa;
(Tokyo, JP) ; Matsuno; Shigeru; (Tokyo,
JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
MITSUBISHI ELECTRIC
CORPORATION
7-3, MARUNOUCHI 2-CHOME
Chiyoda-ku Tokyo Japan
JP
100-8310
|
Family ID: |
36202850 |
Appl. No.: |
11/575874 |
Filed: |
October 7, 2005 |
PCT Filed: |
October 7, 2005 |
PCT NO: |
PCT/JP05/18614 |
371 Date: |
March 23, 2007 |
Current U.S.
Class: |
428/704 ;
257/E21.292; 257/E21.576; 427/569; 427/585 |
Current CPC
Class: |
H01L 21/76801 20130101;
C23C 16/38 20130101; H01L 21/318 20130101 |
Class at
Publication: |
428/704 ;
427/569; 427/585 |
International
Class: |
C23C 8/00 20060101
C23C008/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 19, 2004 |
JP |
204-304015 |
Claims
1. A method of manufacturing a film, comprising the steps of: using
a compound with borazine skeleton as a raw material; and forming
the film on a substrate by using a chemical vapor deposition
method, wherein a negative charge is applied to a site for placing
said substrate.
2. The method of manufacturing the film according to claim 1,
wherein said compound with borazine skeleton is expressed by a
chemical formula (1) below. ##STR4## (In the formula,
R.sub.1-R.sub.6 may be identical with or different from each other,
and are each independently selected from a group consisting of a
hydrogen atom, and an alkyl group, an alkenyl group and an alkynyl
group each having a carbon number of 1-4, on condition that at
least one of R.sub.1-R.sub.6 is not the hydrogen atom.)
3. The method of manufacturing the film according to claim 1,
wherein a plasma is used in combination during chemical vapor
deposition.
4. The method of manufacturing the film according to claim 3,
wherein an ion and/or a radical of a raw material gas are/is
generated by said plasma.
5. A semiconductor device utilizing a film manufactured by the
method cited in claim 1, said film being used as an interwire
insulating material.
6. A semiconductor device utilizing a film manufactured by the
method cited in claim 1, said film being used as a protective film
on an element.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method of manufacturing a
film, in which method an insulating film used between layers of a
semiconductor element or a film used for a substrate of an electric
circuit component (also referred to as a "low dielectric constant
film") is formed by a chemical vapor deposition (hereinafter
abbreviated as CVD) method. The present invention also relates to a
semiconductor device utilizing a film manufactured by the method
according to the present invention.
BACKGROUND ART
[0002] As a semiconductor element achieves a higher speed and a
more highly integrated structure, a problem of a signal delay
becomes more and more serious. The signal delay is represented by a
product of wiring resistance, and interwire and interlayer
capacitance. In order to minimize the signal delay, decreasing a
dielectric constant of an interlayer insulating film as well as
reducing the wiring resistance is an effective measure.
[0003] Recently, as a method of decreasing a dielectric constant of
an interlayer insulating film, there has been disclosed a method of
forming, at a surface of a body to be processed, an interlayer
insulating film containing a B--C--N linkage by plasma CVD in an
atmosphere containing a hydrocarbon-based gas, borazine, and a
plasma-based gas. Furthermore, it is disclosed that the interlayer
insulating film has a low dielectric constant (e.g. see Japanese
Patent Laying-Open No. 2000-058538 (Patent Document 1)).
[0004] However, the conventional method above uses borazine as a
CVD raw material, and hence, although there can be formed a film
having a low dielectric constant and a high mechanical strength,
these characteristics do not continue because of its poor water
resistance. Furthermore, in a heating treatment associated with a
process of manufacturing a device by utilizing a substrate where
the film is formed, a gas component is generated from the film to
exert an adverse effect on the device manufacturing process.
[0005] Patent Document 1: Japanese Patent Laying-Open No.
2000-058538
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0006] The present invention is made to solve the problems above in
the conventional technique. An object of the present invention is
to provide a method of manufacturing a film, which method stably
provides a low dielectric constant and a high mechanical strength
over a long period of time, reduces the amount of a gas component
(outgas) emitted in heating the film, and avoids any trouble in a
device manufacturing process.
[0007] Furthermore, another object of the present invention is to
provide a semiconductor device utilizing a film manufactured by the
manufacturing method above.
Means for Solving the Problems
[0008] A method of manufacturing a film according to the present
invention includes the steps of: using a compound with borazine
skeleton as a raw material; and forming the film on a substrate by
using a chemical vapor deposition method, characterized in that a
negative charge is applied to a site for placing the substrate.
[0009] Preferably, the compound with borazine skeleton is herein
expressed by a chemical formula (1) below. ##STR2## (In the
formula, R.sub.1-R.sub.6 may be identical with or different from
each other, and are each independently selected from a group
consisting of a hydrogen atom, and an alkyl group, an alkenyl group
and an alkynyl group each having a carbon number of 1-4, on
condition that at least one of R.sub.1-R.sub.6 is not the hydrogen
atom.)
[0010] In the method of manufacturing the film according to the
present invention, it is preferable that a plasma is used in
combination during chemical vapor deposition. It is more preferable
herein that an ion and/or a radical of a raw material gas are/is
generated by the plasma.
[0011] The present invention also provides a semiconductor device
utilizing a film obtained by the above-described manufacturing
method according to the present invention, the semiconductor device
including (1) a semiconductor device utilizing the film as an
interwire insulating material, and (2) a semiconductor device
utilizing the film as a protective film on an element.
EFFECTS OF THE INVENTION
[0012] According to the method of manufacturing the film according
to the present invention, it is possible to stably provide a low
dielectric constant and a high mechanical strength over a long
period of time, and also reduce the amount of an outgas from the
obtained film in manufacturing the device.
[0013] According to the present invention, it is also possible to
provide a semiconductor device utilizing a film having a lower
dielectric constant, an improved crosslink density, and an improved
mechanical strength, when compared with the conventional one.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 schematically shows an example of a PCVD device
suitably used in the present invention.
[0015] FIG. 2 is a graph showing TDS data of a film formed in
Example 1.
[0016] FIG. 3 is a graph showing TDS data of a film formed in
Comparative Example 1.
[0017] FIG. 4 is a graph showing an example of an FT-IR spectrum
shape of each of films formed on a power feed electrode side (solid
line) and on a counter electrode side (dashed line).
[0018] FIG. 5 is a cross section schematically showing a
semiconductor device 21, which is a preferable example of the
present invention.
[0019] FIG. 6 is a cross section schematically showing a
semiconductor device 41, which is another preferable example of the
present invention.
DESCRIPTION OF THE REFERENCE SIGNS
[0020] 1 reaction container, 2 high-frequency power source, 3
matching box, 4 vacuum pump, 5 gas inlet, 6 heating/cooling device,
7 power feed electrode, 8 substrate, 9 counter electrode, 21
semiconductor device, 22 semiconductor substrate, 23, 25, 27, 29
insulating layer, 24, 26, 28 conducting layer, 41 semiconductor
device, 42 semiconductor substrate, 43 gate electrode, 44 source
electrode, 45 drain electrode, 46 insulating layer.
BEST MODES FOR CARRYING OUT THE INVENTION
[0021] The method of manufacturing the film according to the
present invention includes the steps of using a compound with
borazine skeleton as a raw material and forming the film on a
substrate by using a chemical vapor deposition (CVD) method,
characterized in that a negative charge is applied to a site for
placing the substrate.
[0022] With the method of manufacturing the film according to the
present invention, the negative charge is applied to the site of
the substrate during CVD, so that the amount of the outgas emitted
in heating the film manufactured by the relevant method is reduced,
and no trouble occurs in the process of manufacturing the device
utilizing the film.
[0023] <Raw Material>
[0024] In the present invention, any appropriate,
conventionally-known compound may be used for the compound with
borazine skeleton without any particular limitation, as long as it
has borazine skeleton. However, a compound expressed by a chemical
formula (1) below is preferably used as a raw material,
particularly because it is possible to manufacture a film improved
in dielectric constant, thermal expansion coefficient, heat
resistance, thermal conductivity, mechanical strength, and the
like. ##STR3##
[0025] In the compound expressed by the chemical formula (I) above,
substituent groups expressed by R.sub.1-R.sub.6 may be identical
with or different from each other, and any of a hydrogen atom, and
an alkyl group, an alkenyl group and an alkynyl group each having a
carbon number of 1-4 may be used independently for the substituent
groups. However, there is no case where all of R.sub.1-R.sub.6 are
hydrogen atoms. If all of them are hydrogen, a boron-hydrogen
linkage or a nitrogen-hydrogen linkage tends to remain in the film.
These linkages have a high hydrophilicity, which disadvantageously
results in increase in hygroscopicity of the film, so that a
desired film may not be obtained. If each of the R.sub.1-R.sub.6 in
the compound (I) above has a carbon number of more than 4, the
formed film has a high content of carbon atoms, so that heat
resistance and mechanical strength of the film may be deteriorated.
The carbon number is more preferably 1 or 2.
[0026] <CVD>
[0027] In the method of manufacturing the film according to the
present invention, a chemical vapor deposition (CVD) method is used
to form the film on a substrate. When the CVD method is used for
film formation, the raw material gas described above forms the film
by successive cross-linking, so that a high crosslink density can
be obtained. Accordingly, the film is expected to have an increased
mechanical strength.
[0028] In the CVD method, helium, argon, nitrogen or the like is
used as a carrier gas to move the raw material gas of the compound
with borazine skeleton (1), which is expressed by the chemical
formula (I) above, to a neighborhood of the substrate where a film
is to be formed.
[0029] At this time, it is also possible to mix methane, ethane,
ethylene, acetylene, ammonia or a compound of alkylamines into the
carrier gas to control the characteristic of the film to be formed
to a desired characteristic.
[0030] The flow rate of the carrier gas may arbitrarily be set to
fall within the range of 100-1000 sccm. The flow rate of the gas of
the compound with borazine skeleton may arbitrarily be set to fall
within the range of 1-300 sccm. The flow rate of methane, ethane,
ethylene, acetylene, ammonia or alkylamines may arbitrarily be set
to fall within the range of 0-100 sccm.
[0031] If the flow rate of the carrier gas is less than 100 sccm,
an extremely long period of time is required for obtaining a
desired film thickness, and there may also be a case where film
formation does not proceed. If the flow rate exceeds 1000 sccm,
uniformity of the film thickness on the substrate tends to be
reduced. The flow rate is more preferably at least 20 sccm and at
most 800 sccm.
[0032] If the flow rate of the gas of the compound with borazine
skeleton is less than 1 sccm, an extremely long period of time is
required for obtaining a desired film thickness, and there may also
be a case where film formation does not proceed. If the flow rate
exceeds 300 sccm, the obtained film has a low crosslink density,
and hence a lowered mechanical strength. The flow rate is more
preferably at least 5 sccm and at most 200 sccm.
[0033] The flow rate of the gas of methane, ethane, ethylene,
acetylene, ammonia or alkylamines exceeds 100 sccm, the obtained
film has a high dielectric constant. The flow rate is more
preferably at least 5 sccm and at most 100 sccm.
[0034] As described above, the raw material gas carried to the
neighborhood of the substrate is deposited on the substrate through
a chemical reaction, so that the film is formed. In order to
efficiently induce the chemical reaction, a plasma is preferably
used in combination during CVD. An ultraviolet ray, an electron
beam or the like can also be used in combination with them to
promote the reaction.
[0035] In the method of manufacturing the film according to the
present invention, it is preferable to heat, during CVD, the
substrate where the film is to be formed, because an outgas can be
reduced more easily. If heat is used for heating the substrate,
each of the gas temperature and the substrate temperature is
controlled to fall within the range from a room temperature to
450.degree. C. If each of the raw material gas temperature and the
substrate temperature exceeds 450.degree. C., an extremely long
period of time is required for obtaining a desired film thickness,
and there may also be a case where film formation does not proceed.
Each of the temperatures is more preferably at least 50.degree. C.
and at most 400.degree. C.
[0036] If a plasma is used for heating the substrate, the substrate
is placed in, for example, a parallel plate-type plasma generator,
and the raw material gas is then introduced thereinto. The
frequency and the power of an RF used at this time may arbitrarily
be set at 13.56 MHz or 400 kHz, and may arbitrarily be set to fall
within the range of 5-1000 W, respectively. Alternatively, it is
also possible to use in combination RFs having these different
frequencies.
[0037] If the power of the RF used for performing plasma CVD
exceeds 1000 W, there is increased the frequency with which the
compound with borazine skeleton expressed by the chemical formula
(1) is decomposed by the plasma, so that it becomes difficult to
obtain a film having a desired borazine structure. The power is
more preferably at least 10 W and at most 800 W.
[0038] In the present invention, the pressure in the reaction
container is preferably set to be at least 0.01 Pa and at most 10
Pa. If the pressure is less than 0.01 Pa, there is increased the
frequency with which the compound with borazine skeleton is
decomposed by the plasma, so that it becomes difficult to obtain a
film having a desired borazine structure. If the pressure exceeds
10 Pa, the obtained film has a low crosslink density, and hence a
low mechanical strength. The pressure is more preferably at least 5
Pa and at most 6.7 Pa. Note that the pressure can be adjusted by
means of a pressure regulator such as a vacuum pump, or by changing
a gas flow rate.
[0039] <Device>
[0040] The method of manufacturing the film according to the
present invention can be implemented by using an appropriate,
conventionally-known device. As described above, when a plasma is
used in combination during CVD in the method of manufacturing the
film according to the present invention, an example of a device
suitably used in particular can include a plasma CVD device (PCVD
device) including means for supplying a compound with borazine
skeleton, a plasma generator for generating a plasma, and means for
applying a negative charge to an electrode for placing the
substrate. The device is implemented such that the compound with
borazine skeleton is supplied by, for example, a method of
introducing the borazine compound into the device having a
vaporization mechanism for heating the borazine compound left at a
room temperature for vaporizing the same, a method of heating a
container itself where the borazine compound is stored, to vaporize
the borazine compound, and subsequently utilizing a pressure, which
is increased by the vaporization of the borazine compound, to
introduce the vaporized borazine compound into the device, a method
of mixing Ar, He, nitrogen or another gas into the vaporized
borazine compound to introduce the same into the device, or the
like. Among these methods, from the viewpoint that heat
denaturation of the raw material is less likely to occur, the
device is preferably implemented such that the compound with
borazine skeleton is supplied by the method of introducing the
borazine compound into the device having a vaporization mechanism
for heating the borazine compound left at a room temperature for
vaporizing the same.
[0041] For the plasma generator in the relevant device, there may
be used, for example, an appropriate plasma generator such as a
capacitively-coupled mode (parallel plate-type) plasma generator or
an inductively-coupled mode (coil type) plasma generator. Among
them, from the viewpoint that a practical film formation rate (10
nm/minute-5000 nm/minute) can easily be obtained, the
capacitively-coupled mode (parallel plate-type) plasma generator is
preferable.
[0042] Furthermore, if a plasma is generated between electrodes by
using the capacitively-coupled type plasma generator in the
relevant device, for example, the device is implemented such that a
negative charge is applied to the electrode for placing the
substrate, by a method of applying a radio frequency to the
electrode for placing the substrate, or a method of applying a
direct current having a frequency other than a radio frequency, or
a radiofrequency alternating current, for generating a plasma, to
the electrode for placing the substrate. Among these methods, from
a viewpoint that it is possible to apply to the substrate a
negative charge independent of an electric potential produced by
the generated plasma, the device is preferably implemented such
that a negative charge is applied to the electrode for placing the
substrate, by the method of applying a direct current.
[0043] For the reason above, the compound with borazine skeleton
used in the PCVD device is preferably the one expressed by the
chemical formula (1) described above.
[0044] Preferably, the PCVD device used in the present invention
further includes a reaction container for forming the film on the
substrate by PCVD. In such a configuration further including the
reaction container, there may adopt any of a configuration where
the plasma generator is provided outside the reaction container,
and a configuration where the plasma generator is provided inside
the reaction container. In the configuration where the plasma
generator is provided outside the reaction container, for example,
the plasma does not directly affect the substrate, and hence there
is an advantage that it is possible to prevent the progress of an
unexpected reaction caused by excessive exposure of the film, which
is produced on the substrate, to an electron, an ion, a radical or
the like in the plasma. In the configuration where the plasma
generator is provided inside the reaction container, there is an
advantage that a practical film formation rate (10 nm/minute-5000
nm/minute) can easily be obtained.
[0045] FIG. 1 schematically shows an example of the PCVD device
suitably used in the present invention. The PCVD device used in the
present invention adopts the configuration where a plasma generator
is provided inside the reaction container described above.
Furthermore, it is particularly preferable that the PCVD device is
implemented by a parallel plate-type PCVD device where the plasma
generator is provided at an electrode for placing a substrate, by
utilizing a capacitively-coupled mode. By implementing the
above-described method of manufacturing the film according to the
present invention with the use of such a PCVD device, the film is
formed on an applying electrode side (by a negative bias), and
hence it is considered that a positive-ionized borazine molecule
generated in the plasma, or He, Ar or the like used as the carrier
gas, impinges on a borazine molecule deposited on the substrate to
generate a new active spot, which enables further progress of a
cross-linking reaction. In contrast, if the film is formed on a
counter electrode side (by a positive bias), more of the electrons
generated in the plasma scatter, when compared with the case where
the film is formed on the applying electrode side, and the
electrons impinge on a borazine molecule deposited on the
substrate, inevitably resulting in more radicals. The generated
radicals have less activity, when compared with the ones generated
by ion impingement, so that it is considered that a sufficient
crosslink density is difficult to obtain.
[0046] In the PCVD device shown in FIG. 1, a reaction container 1
is provided with a power feed electrode 7 with a heating/cooling
device 6 interposed therebetween, and a substrate 8, to which a
film is to be formed, is disposed on power feed electrode 7.
Heating/cooling device 6 can heat or cool substrate 8 to a
prescribed processing temperature. Power feed electrode 7 is
connected to a high-frequency power source 2 via a matching box 3,
which makes it possible to adjust an electric potential to a
prescribed one.
[0047] In reaction container 1 in FIG. 1, a counter electrode 9 is
provided on a side opposite to substrate 8. A gas inlet 5 and a
vacuum pump 4 for ejecting a gas inside reaction container 1 are
further provided.
[0048] As to substrate 8 where a film is to be grown in reaction
container 1 for generating a plasma, substrate 8 is placed at power
feed electrode 7 for inducing a plasma to perform film formation,
so that a desired film can be formed. At this time, by imparting an
electric potential onto counter electrode 9 opposite to power feed
electrode 7 from another high-frequency power source, it is also
possible to arbitrarily adjust the electric potential on substrate
8 where a film is to be formed. In this case, the present invention
is characterized in that power feed electrode 7 on the side of
substrate 8 is set at a negative electric potential.
[0049] If the film is to be grown in a film forming device using a
dense plasma source, a desired film may be formed by using a power
source independent of high-frequency power source 2 serving as a
plasma source and applying a negative charge to the substrate.
[0050] The PCVD device shown in FIG. 1 is configured such that
counter electrode 9 is located on an upper side of the device,
while power feed electrode 7 is located on an lower side of the
device. However, these electrodes are only required to be located
to face each other, and a vertically-reverse configuration, for
example, may of course be possible (in this case, substrate 8 has a
structure allowing itself to be supported by a substrate fixing
part such as a flat spring, a screw, a pin or the like, so that it
is fixed to power feed electrode 7. Here, a susceptor substrate may
also be placed at power feed electrode 7 directly. Alternatively,
substrate 8 may also be fixed to power feed electrode 7 via a jig
for transporting a substrate.).
[0051] A method of implementing the present invention by using the
device shown in FIG. 1 will hereinafter be described. In FIG. 1,
substrate 8 is initially disposed on power feed electrode 7 and
reaction container 1 is evacuated. A raw material gas, a carrier
gas, and another gas described above, as needed, are then supplied
to reaction container 1 through gas inlet 5. The flow rate used
when each of the gases are supplied is as described above. In
addition to this, the pressure in reaction container 1 is
maintained to a prescribed processing pressure by evacuating
reaction container 1 by means of vacuum pump 4. Furthermore,
substrate 8 is set to a prescribed processing temperature by means
of heating/cooling device 6.
[0052] A negative charge is applied to power feed electrode 7 by
means of high-frequency power source 2 to generate a plasma in the
gases in reaction container 1. In the plasma, the raw material gas
and the carrier gas are turned into ions and/or radicals, which are
successively deposited on substrate 8 to form a film.
[0053] Among them, the ion is attracted to the electrode at an
electric potential opposite to an electric charge owned by the ion
itself, and repeatedly impinges on the substrate to cause a
reaction. In other words, in relation to an electric charge, a
cation is attracted to a side of power feed electrode 7, whereas an
anion is attracted to a side of counter electrode 9.
[0054] In contrast, the radicals are uniformly distributed in a
plasma field. Accordingly, if a film is formed on the side of power
feed electrode 7, many reactions are caused mainly by a cation, and
hence a contribution of radical species to film formation is
decreased.
[0055] Accordingly, it is possible in the present invention to
reduce the amount of a radical remaining in the formed film by
adjusting an electric potential of the electrodes, as described
above, and hence there is suppressed a reaction between the radical
remaining in the film and a substance such as oxygen or water in
the air, which substance is active toward the radical, after the
substrate is removed from the PCVD device.
[0056] If the radical remains in the film, the reaction between the
borazine radical and oxygen or water occurs when the film is
heated, so that B-hydroxyborazine is produced. Furthermore,
B-hydroxyborazine further reacts with water in the air to produce
boroxin and ammonia, so that the radical in the film makes brittle
a part of the film, which tends to produce an outgas. However, with
the manufacturing method according to the present invention,
radical species in the film are reduced, and hence the film formed
by the method according to the present invention has a small amount
of remaining radical, which makes it possible to reduce the amount
of an outgas.
[0057] In the parallel plate-type PCVD device shown in FIG. 1, an
example of the frequency of electric power to be applied is 13.56
MHz. However, an HF (a few tens-a few hundreds kHz), a microwave
(2.45 GHz), or an ultrashort wave of 30 MHz-300 MHz may be used. If
the microwave is used, there may be used a method of exciting the
reaction gas to form a film in an afterglow, or ECR plasma CVD in
which the microwave is introduced into a magnetic field that
satisfies an ECR condition.
[0058] <Film>
[0059] With the method of manufacturing the film according to the
present invention, a film having a lower dielectric constant can be
manufactured when compared with a film using a conventional
compound with borazine skeleton as a raw material. Here, "low
dielectric constant" means that a certain dielectric constant can
be maintained over a long period of time in a stable manner.
Specifically, the film formed by the conventional manufacturing
method maintains a dielectric constant of approximately 3.0-1.8 for
a few days, whereas the film according to the present invention can
maintain the above-described dielectric constant for at least a few
years. The low dielectric constant can be confirmed, for example,
by measuring the dielectric constant of the film stored for a
certain period, with a method similar to that used immediately
after the film formation.
[0060] The film obtained in the present invention can implement a
higher crosslink density, when compared with the film obtained by
the conventional manufacturing method, and is a closely-packed film
with improved mechanical strength (modulus of elasticity, strength
or the like). The improvement in crosslink density can be confirmed
from an FT-IR spectrum shape, for example, in which a peak adjacent
to 1400 cm.sup.-1 is shifted to a low frequency side. FIG. 4 shows
an example of this FT-IR spectrum. It can be seen that the peak of
an FT-IR spectrum shape of the film on the power feed electrode
side (shown by a solid line in this drawing) is shifted to a low
frequency side with respect to the peak of an FT-IR spectrum shape
of the film on the counter electrode side (shown by a dashed line
in this drawing).
[0061] <Semiconductor Device>
[0062] The present invention also provides a semiconductor device
utilizing a film obtained by the above-described manufacturing
method according to the present invention. FIG. 5 is a cross
section schematically showing a semiconductor device 21, which is a
preferable example of the present invention. Semiconductor device
21 in FIG. 5 represents an example in which the above-described
film according to the present invention is used as an interwire
insulating material (interlayer insulating film).
[0063] Semiconductor device 21 in the example shown in FIG. 5 is
formed such that a first insulating layer 23 is formed on a
semiconductor substrate 22 made of silicon, that a concave portion
corresponding to the shape of a first wire is formed in first
insulating layer 23, and that a first conducting layer 24 is formed
of a conducting material to fill the concave portion. Furthermore,
in the example shown in FIG. 5, a second insulating layer 25 is
formed on first insulating layer 23 and first conducting layer 24,
and a through hole is formed in second insulating layer 25 to reach
first conducting layer 24, and a second conducting layer 26 is
formed of a conducting material to fill the hole. In the example
shown in FIG. 5, a third insulating layer 27 is further formed on
second insulating layer 25 and second conducting layer 26, and a
concave portion corresponding to the shape of a second wire is
formed in third insulating layer 27, and a third conducting layer
28 is formed of a conducting material to fill the concave portion.
Furthermore, a fourth insulating layer is formed on third
insulating layer 27 and the third conducting layer.
[0064] Semiconductor device 21 according to the present invention
is implemented by utilizing the film obtained by the manufacturing
method according to the present invention for at least any of the
insulating films (preferably for all the first to fourth insulating
layers), in the above-described configuration shown in FIG. 5. If a
plurality of films according to the present invention are used,
there may be used the films all formed of the same raw material, or
the films formed of raw materials different from each other, which
raw materials are selected from the compounds with borazine
skeleton. The film according to the present invention has a lower
dielectric constant when compared with the conventional one, as
described above, and hence by implementing the wiring structure as
shown in FIG. 5, wiring capacitance can be more reduced than in the
conventional one, which makes it possible to implement the
semiconductor device enabling a higher-speed operation.
[0065] For the conducting material used for forming the conducting
layer in semiconductor device 21 according to the present
invention, an appropriate, conventionally-known conducting material
such as copper, aluminum, silver, gold, or platinum may be used
without any particular limitation. Semiconductor device 21
according to the present invention adopts a configuration in which
the film according to the present invention is brought into contact
with the conducting layer, and hence even if copper, for example,
is used for the conducting material, there is an advantage that
diffusion of copper from the conducting layer can be prevented by
the insulating layer.
[0066] Note that there is no need to use the film according to the
present invention for all the insulating layers in semiconductor
device 21 according to the present invention, and a film made of
silicon oxide (SiO) or silicon oxide carbide (SiOC), for example,
having an appropriate insulation property may also be applied to
any of the insulating layers.
[0067] FIG. 6 is a cross section schematically showing a
semiconductor device 41, which is another preferable example of the
present invention. Semiconductor device 41 in FIG. 6 is an example
in which the film obtained by the above-described manufacturing
method according to the present invention is used as a protective
film (passivation film) on an element.
[0068] Semiconductor device 41 in the example shown in FIG. 6
represents an example of a field-effect type transistor in which a
gate electrode 43, a source electrode 44, and a drain electrode 45
are formed on a semiconductor substrate 42 made of silicon, a
protective film (passivation film) 46 being formed to cover gate
electrode 43, source electrode 44, and drain electrode 45.
[0069] Semiconductor device 41 according to the present invention
utilizes the film according to the present invention as protective
film 46, in the structure above shown in FIG. 6. In semiconductor
device 41 according to the present invention, parasitic capacitance
generated on the gate electrode and on the semiconductor substrate
is more reduced, when compared with the case of a typically- and
conventionally-used protective film formed of silicon nitride
(SiN). Accordingly, an S/N characteristic of the transistor is
improved.
[0070] Note that it is of course possible to further stack an
insulating layer made of SiN or SiO on protective film 46 as
needed, in semiconductor device 41 according to the present
invention.
[0071] The present invention will hereinafter be described in
detail by providing examples. However, the present invention is not
intended to be limited thereto.
EXAMPLE 1 AND COMPARATIVE EXAMPLE 1
[0072] The parallel plate-type plasma CVD device in the example
shown in FIG. 1 was used to form a film as follows. Helium was used
as a carrier gas, and charged into a reaction container with a flow
rate set to be 200 sccm. Furthermore, a
B,B,B,N,N,N-hexamethylborazine gas serving as a raw material gas
was introduced into the reaction container, where a substrate was
placed, through a heated gas inlet, with a flow rate set to be 10
sccm. The steam temperature of the B,B,B,N,N,N-hexamethylborazine
gas was 150.degree. C. The substrate temperature was raised to
100.degree. C., and a radiofrequency current of 13.56 MHz was
applied to reach 150 W from a power feed electrode side, where the
substrate was placed. The pressure in the reaction container was
maintained at 2 Pa. By doing so, a film was formed on the
substrate.
[0073] While the temperature of the obtained film on the substrate
was raised at a rate of 60.degree. C./minute, the amount of an
outgas was measured by a thermal desorption spectroscopy (TDS)
device. For the case where a substrate was placed on a counter
electrode side (Comparative Example 1), there was measured, for
comparison, the amount of an outgas from a film obtained
concurrently with the above-described film, by means of the
TDS.
[0074] For a measurement condition, each of the substrates were cut
into a chip of a one centimeter square, and a comparison was made
between the outgases emitted from the films thereon. FIG. 2 shows a
vacuum degree of the film formed on the supply electrode side by
the method according to the present invention, when the temperature
of the film was raised. In FIG. 2, the vertical axis represents a
vacuum degree (Pa), while the horizontal axis represents a
temperature (.degree. C.).
[0075] FIG. 2 shows that the outgas emitted from the film is
increased with increasing vacuum degree. No obvious change in
vacuum degree can be seen until the temperature reaches
approximately 400.degree. C., which shows that no outgas is
generated by heating.
[0076] For comparison, FIG. 3 shows TDS data of the film formed on
the counter electrode side. In FIG. 3, the vertical axis represents
a vacuum degree (Pa), while the horizontal axis represents a
temperature (.degree. C.). In FIG. 3, a vacuum degree is increased
at a temperature of 100.degree. C. or higher, which shows that an
outgas is generated when the film is formed on the counter
electrode side. In view of these, it was found that a film emitting
less outgas can be formed by placing a substrate, where the film is
to be formed, on the power feed electrode and maintaining the
substrate at a negative electric potential.
EXAMPLES 2-13, COMPARATIVE EXAMPLES 2-13
[0077] A TDS measurement was performed on a film formed of a
modified type of the raw material gas, by a method similar to that
of Example 1. Table 1 shows the results of Examples 2-9 (the case
where the film was formed on the power feed electrode side), while
Table 2 shows the results of Comparative Examples 2-9 (the case
where the film was formed on the counter electrode side).
Furthermore, Table 3 shows the results of Examples 10-13 (the case
where the film was formed on the power feed electrode side), while
Table 4 shows the results of Comparative Examples 10-13 (the case
where the film was formed on the counter electrode side).
TABLE-US-00001 TABLE 1 Example 2 Example 3 Example 4 Example 5
Example 6 Example 7 Example 8 Example 9 Raw N,N,N- B,B,B- B,B,B-
B,B,B- B,B,B- B,N,N,N- B,B,B,N,N,N- borazine Material trimethyl
triethyl triethyl- trivinyl- triethynyl- tetramethyl pentamethyl
Gas borazine borazine N,N,N- N,N,N- N,N,N- borazine borazine
trimethyl trimethyl trimethyl borazine borazine borazine Carrier He
He He Ar Ar He He He Gas RF Power 500 400 150 300 100 500 400 150
(W) Vacuum 1.61 .times. 10.sup.-7 1.41 .times. 10.sup.-7 2.00
.times. 10.sup.-7 1.92 .times. 10.sup.-7 1.36 .times. 10.sup.-7
1.99 .times. 10.sup.-7 2.36 .times. 10.sup.-7 3.07 .times.
10.sup.-6 Degree at 400.degree. C. by TDS (Pa)
[0078] TABLE-US-00002 TABLE 2 Comparative Comparative Comparative
Comparative Comparative Comparative Comparative Comparative Example
2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8
Example 9 Raw N,N,N- B,B,B- B,B,B- B,B,B- B,B,B- B,N,N,N-
B,B,B,N,N,N- borazine Material trimethyl triethyl triethyl-
trivinyl- triethynyl- tetramethyl pentamethyl Gas borazine borazine
N,N,N- N,N,N- N,N,N- borazine borazine trimethyl trimethyl
trimethyl borazine borazine borazine Carrier Gas He He He Ar Ar He
He He RF Power (W) 500 400 150 300 100 500 400 150 Vacuum 2.64
.times. 10.sup.-5 2.07 .times. 10.sup.-5 2.17 .times. 10.sup.-5
2.17 .times. 10.sup.-5 1.32 .times. 10.sup.-5 2.51 .times.
10.sup.-5 2.68 .times. 10.sup.-5 -- Degree at 400.degree. C. by TDS
(Pa)
[0079] TABLE-US-00003 TABLE 3 Example 10 Example 11 Example 12
Example 13 Raw Material B,B,B- B,B,B- B,B,B- B,B,B- Gas tripropyl
triallyl tributyl triisobutyl borazine borazine borazine borazine
Carrier Gas He He He He RF Power (W) 400 400 400 400 Vacuum 1.85
.times. 10.sup.-7 1.79 .times. 10.sup.-7 2.20 .times. 10.sup.-7
2.11 .times. 10.sup.-7 Degree at 400.degree. C. by TDS (Pa)
[0080] TABLE-US-00004 TABLE 4 Comparative Comparative Comparative
Comparative Example Example Example Example 10 11 12 13 Raw
Material B,B,B- B,B,B- B,B,B- B,B,B- Gas tripropyl triallyl
tributyl triisobutyl borazine borazine borazine borazine Carrier
Gas He He He He RF Power (W) 400 400 400 400 Vacuum 2.71 .times.
10.sup.-5 2.56 .times. 10.sup.-5 3.15 .times. 10.sup.-5 3.05
.times. 10.sup.-5 Degree at 400.degree. C. by TDS (Pa)
[0081] Tables 1-4 show that the film formed on the side of the
power feed electrode emits less outgas than the film formed on the
counter electrode side in any of the cases. In Comparative Example
9, in which borazine (all the R.sub.1 to R.sub.6 are hydrogen in
the chemical formula (1)) was used as a raw material and a film was
formed on the counter electrode side, white turbidity appears in
the film immediately after the substrate was removed from the film
forming device, and hence TDS measurement was failed. It seems that
this is because the film had extremely high hygroscopicity.
EXAMPLE 14
[0082] There was fabricated semiconductor device 21 in the example
shown in FIG. 5. Initially, the PCVD device shown in FIG. 1 was
used, N,N,N-trimethylborazine shown in Example 2 was used as a raw
material, and a negative charge was applied on the power feed
electrode side, so that first insulating layer 23 having a
thickness of 0.2 .mu.m was formed on semiconductor substrate 22
made of silicon. A resist film formed on first insulating layer 23
was exposed with the use of a pattern, and then developed to obtain
a resist pattern. The first insulating layer with the resist
pattern was etched to form a concave portion (corresponding to a
first wire shape) in first conducting layer 24, which concave
portion had a width of 0.1 .mu.m and a depth of 0.1 .mu.m. First
conducting layer 24 made of copper was then formed to fill the
concave portion. Subsequently, the PCVD device shown in FIG. 1 was
used, N,N,N-trimethylborazine shown in Example 2 was used as a raw
material, and a negative charge was applied on the power feed
electrode side, so that second insulating layer 25 having a
thickness of 0.2 .mu.m was formed on first insulating layer 23 and
first conducting layer 24. A resist film formed on second
insulating layer 25 was exposed with the use of a pattern, and then
developed to obtain a resist pattern. The second insulating layer
with the resist pattern was etched to form a through hole reaching
first conducting layer 24, which through hole had a diameter of 0.1
.mu.m. Second conducting layer 26 made of copper was formed to fill
the hole. Furthermore, the PCVD device shown in FIG. 1 was used,
N,N,N-trimethylborazine shown in Example 2 was used as a raw
material, and a negative charge was applied on the power feed
electrode side, so that third insulating layer 27 having a
thickness of 0.2 .mu.m was formed on second insulating layer 25 and
second conducting layer 26. A resist film formed on third
insulating layer 27 was exposed with the use of a pattern, and then
developed to obtain a resist pattern. The third insulating layer
with the resist pattern was etched to form a concave portion
(corresponding to a second wire shape) having a width of 0.1 .mu.m
and a depth of 0.2 .mu.m. Third conducting layer 28 made of copper
was formed to fill the concave portion. Furthermore, the PCVD
device shown in FIG. 1 was used, N,N,N-trimethylborazine shown in
Example 2 was used as a raw material, and a negative charge was
applied on the power feed electrode side, so that a fourth
insulating layer having a thickness of 0.05 .mu.m was formed on
third insulating layer 27 and the third conducting layer. As such,
there was fabricated semiconductor device 21 in the example shown
in FIG. 5.
EXAMPLE 15
[0083] Semiconductor device 41 in the example shown in FIG. 6 was
fabricated. The PCVD device shown in FIG. 1 was used,
N,N,N-trimethylborazine shown in Example 2 was used as a raw
material, and a negative charge was applied on the power feed
electrode side, so that protective film 46 having a thickness of
0.05 .mu.m was formed at a field-effect type transistor, in which
gate electrode 42, source electrode 43, and drain electrode 44 are
formed at semiconductor substrate 42 made of silicon. As such,
there was fabricated semiconductor device 41 in the example shown
in FIG. 6.
[0084] The dielectric constant of the protective film, which was
measured in a manner similar to Example 14, was 2.5, so that when
compared with the case where typically- and conventionally-used
silicon nitride (SiN) having a dielectric constant of approximately
7 was used to form a protective film, it was possible to implement
the transistor with an improved S/N characteristic.
[0085] It should be understood that the embodiments and examples
disclosed herein are illustrative and not limitative in all
aspects. The scope of the present invention is shown not by the
description above but by the scope of the claims, and is intended
to include all modifications within the equivalent meaning and
scope of the claims.
* * * * *