U.S. patent application number 16/257185 was filed with the patent office on 2020-07-30 for oxide film forming method.
This patent application is currently assigned to ASM IP Holding B.V.. The applicant listed for this patent is ASM IP Holding B.V.. Invention is credited to Takafumi HISAMITSU, Seiji OKURA.
Application Number | 20200240016 16/257185 |
Document ID | 20200240016 / US20200240016 |
Family ID | 1000004954553 |
Filed Date | 2020-07-30 |
Patent Application | download [pdf] |
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United States Patent
Application |
20200240016 |
Kind Code |
A1 |
HISAMITSU; Takafumi ; et
al. |
July 30, 2020 |
OXIDE FILM FORMING METHOD
Abstract
Examples of a oxide film forming method include providing a
precursor to a reaction space including a substrate and a
susceptor, and forming an oxide film on the substrate by
introducing at least one of CxOy and NxOy (x and y are integers) as
a reactant gas into the reaction space while applying a pulse RF
power having a duty cycle less than 60% to an RF plate to generate
plasma of the reactant gas, the RF plate being provided in the
reaction space so as to face the susceptor, wherein the providing
and the forming are repeated a predetermined number of times.
Inventors: |
HISAMITSU; Takafumi;
(Sagamihara-shi, JP) ; OKURA; Seiji;
(Sagamihara-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ASM IP Holding B.V. |
Almere |
|
NL |
|
|
Assignee: |
ASM IP Holding B.V.
Almere
NL
|
Family ID: |
1000004954553 |
Appl. No.: |
16/257185 |
Filed: |
January 25, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 16/405 20130101;
C23C 16/407 20130101; C23C 16/45542 20130101; C23C 16/401 20130101;
C23C 16/45553 20130101 |
International
Class: |
C23C 16/455 20060101
C23C016/455; C23C 16/40 20060101 C23C016/40 |
Claims
1. An oxide film forming method comprising: providing a precursor
to a reaction space including a substrate and a susceptor; and
forming an oxide film on the substrate by introducing at least one
of CxOy and NxOy (x and y are integers) as a reactant gas into the
reaction space while applying a pulse RF power having a duty cycle
less than 50% to an RF plate to generate plasma of the reactant
gas, the RF plate being provided in the reaction space so as to
face the susceptor, wherein the providing and the forming are
repeated a predetermined number of times, and a frequency of the
pulse RF power is equal to or less than 250 Hz.
2. (canceled)
3. The oxide film forming method according to claim 1, wherein the
duty cycle of the pulse RF power is more than 0% and equal to or
less than 15%.
4-5. (canceled)
6. The oxide film forming method according to claim 1, wherein the
precursor includes Si, Ti or Ge, and the oxide film includes SiO,
TiO or GeO.
7. The oxide film forming method according to claim 1, comprising:
purging the precursor without adsorbing to the substrate remaining
in the reaction space, after providing the precursor and before
generating the plasma; and purging the reaction space after forming
the oxide film, wherein the reaction space is supplied with the
reactant gas through the precursor providing, the precursor
purging, the oxide film forming, and the reaction space
purging.
8. The oxide film forming method according to claim 1, wherein when
the oxide film is formed, oxygen plasma is generated in addition to
the plasma of the reactant gas.
9. The oxide film forming method according to claim 1, wherein when
the oxide film is formed, plasma of the reactant gas is generated
without providing oxygen to the reaction space.
Description
TECHNICAL FIELD
[0001] Examples are described which relate to an oxide film forming
method.
BACKGROUND
[0002] PEALD (Plasma-Enhanced Atomic Layer Deposition) causes a
precursor to adsorb to a substrate, for example, and subsequently
generates oxygen plasma, thereby forming an oxide film on the
substrate. For example, the substrate includes a certain thin film
or a pattern as a covered object on a surface, and an oxide film
can be formed on the covered object through PEALD. The covered
object is called an underlying film because this film serves as an
underlayer for the oxide film. The oxygen plasma can be generated
by providing oxygen gas for a reaction space including an RF plate
and by applying a high-frequency power to the RF plate.
[0003] Depending on a type of the underlying film or an oxidation
source, the underlying film may be damaged as the oxide film is
formed through PEALD. Such damage may sometimes thin the underlying
film.
SUMMARY
[0004] Some examples described herein may address the
above-described problems. Some examples described herein may
provide an oxide film forming method that can reduce the adverse
effect on the substrate.
[0005] In some examples, an oxide film forming method includes
providing a precursor to a reaction space including a substrate and
a susceptor, and forming an oxide film on the substrate by
introducing at least one of CxOy and NxOy (x and y are integers) as
a reactant gas into the reaction space while applying a pulse RF
power having a duty cycle less than 60% to an RF plate to generate
plasma of the reactant gas, the RF plate being provided in the
reaction space so as to face the susceptor, wherein the providing
and the forming are repeated a predetermined number of times.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 illustrates a configuration example of a film-forming
apparatus;
[0007] FIG. 2 is a timing chart illustrating an oxide film forming
method;
[0008] FIG. 3 illustrates an example of the spectrum of the pulse
RF power; and
[0009] FIG. 4 shows the relationship between the duty cycle of the
pulse RF power and the amount of film loss.
DETAILED DESCRIPTION
[0010] The oxide film forming method is described with reference to
the drawings. The same or corresponding configuration elements are
assigned the same symbols, and the redundant description may be
omitted in some cases.
[0011] FIG. 1 illustrates a configuration example of a film-forming
apparatus. A susceptor 12 and an RF plate 14 are provided in a
chamber 10. A parallel plate structure where the susceptor 12 and
the RF plate 14 face each other provides a reaction space 10A in
the chamber 10.
[0012] The susceptor 12 supports a substrate 20. The substrate 20
serves as an object on which an oxide film is to be formed. The
substrate 20 has a material containing carbon as an underlying
film, for example. The underlying film is photoresist, for example.
The susceptor 12 may be a grounded electrode. For example, the
susceptor 12 is heated or cooled to control the temperature of the
substrate 20.
[0013] The RF plate 14 is connected to a power source 16. The power
source 16 applies HRF power of 13.56 or 27 MHz, for example, to the
RF plate 14. The power source 16 also applies LRF power of 5 MHz or
400 to 500 kHz, for example, to the RF plate 14 as required.
Application of the RF power to the RF plate 14 generates plasma in
the reaction space 10A, specifically between the susceptor 12 and
the RF plate 14.
[0014] The power source 16 applies pulse RF power to the RF plate
14. For example, the power source 16 does not continuously
oscillate but pulse-oscillates instead. The power source 16 can
apply duty-controlled pulse RF power to the RF plate 14.
[0015] The RF plate 14 also functions as a shower plate. A gas is
supplied into the reaction space 10A from above the RF plate 14
through a through-hole 14a of the RF plate 14. For example, a
precursor 30 in a liquid state, a carrier gas source 32, and a
reactant gas source 34 can be provided. The precursor 30 is
preserved in the liquid state, and can supply its vapor by being
heated. A tube that introduces the precursor 30 into the chamber 10
is provided with valves. By opening a valve, the vapor of the
precursor 30 can be provided together with the gas of the carrier
gas source 32 for the reaction space 10A. By opening another valve,
the reactant gas of the reactant gas source 34 can be provided for
the reaction space 10A. Valve opening and closing processes control
whether to provide the gas for the reaction space 10A or not.
[0016] An exhaust duct 18 can be formed to surround the susceptor
12. The gas having been supplied to the reaction space 10A radiates
in a plan view, enters the exhaust duct 18, and is exhausted to the
outside of the chamber 10. In a case where the apparatus described
above is used, a controller that achieves the following method can
be provided.
[0017] FIG. 2 is a timing chart illustrating an oxide film forming
method. According to one example, the oxide film forming method
includes (A) precursor providing, (B) source purging, (C) RF
application, and (D) post purge, in this order. The A to D
processes serve as one film forming process. Repetition of the
process forms an oxide film having a desired thickness.
[0018] In this disclosure, the "oxide film" may refer to a film
characterized by M-O bonds (M is a metal or silicon), constituted
mainly or predominantly by M-O bonds, categorized in M-O films,
and/or having a main skeleton substantially constituted by M-O
bonds. When a precursor having hydrocarbons such as
organoaminosilane is used, the oxide film may contain carbons
derived from the precursor. In some examples, the oxide film may
contain C, H, and/or N as a minor element.
(A) Precursor Providing
[0019] In a time period T1 in FIG. 2, the substrate is supplied
with the precursor. The valve is opened to supply the reaction
space 10A with the vapor of the precursor 30 together with the
carrier gas.
[0020] As the precursor, silane compounds such as monosilane are
excluded since they are reactive to oxygen even without a plasma.
In some examples, the precursor is non-reactive to oxygen, CxOy,
and NxOy, and the term "non-reactive" refers to detecting no film
volume or particles generated on a substrate as a result of
reaction under conditions where the precursor and oxygen, CxOy, or
NxOy are introduced simultaneously to a reaction space in an
atmosphere having a temperature of 400.degree. C. or less and a
pressure of 10 torr or less in the absence of plasma. In some
examples, the precursor contains Si, Ti, or Ge, and the oxide film
is constituted substantially by SiO, TiO, or GeO. In other
examples, the precursor contains As, Ga, Sb, In, Al, or Zr. A
skilled artisan can select a suitable precursor depending on the
type of oxide film through routine experiment based on this
disclosure.
[0021] For example, for SiO film, organoaminosilanes can be used,
including bis(diethylamino)silane (BDEAS or SAM24),
tetrakis(dimethylamino)silane (4DMAS), tris(dimethylamino)silane
(3DMAS), bis(dimethylamino)silane (2DMAS),
tetrakis(ethylmethylamino)silane (4EMAS),
tris(ethylmethylamino)silane (3EMAS),
bis(tertiary-butylamino)silane (BTBAS), and
bis(ethylmethylamino)silane (BEMAS), singly or in any combination
of two or more. For example, for AsO film, triethoxyarsine and
triethylarsenate, singly or in any combination, can be used. For
example, for SbO film, Sb(i-O--C.sub.3H.sub.7).sub.3 and antimony
tri-ethoxide, singly or in any combination, can be used. For
example, for InO film, (CH.sub.3).sub.3In and
(C.sub.2H.sub.5).sub.3In, singly or in any combination, can be
used. For example, for GaO film, Ga(OCH.sub.3).sub.3, and
Ga(OC.sub.2H.sub.5).sub.3, singly or in any combination of two or
more, can be used. For example, for TiO film, titanium isopropoxide
or titanium tetraisopropoxide (TTiP), tetrakis(dimethylamino)
titanium (TDMAT),
tetrakis(1-methoxy-2-methyl-2-propanolate)titanium (Ti(MMP)4),
titanium-tetra-butoxide (TTB), and
tetrakis(ethylmethylamino)titanium (TEMAT), singly or in any
combination of two or more, can be used. For example, for GeO film,
tetraethyloxygermane (TEOG), tetramethyloxygermane (TMOG),
tetraethylgermane (TEG), tetramethylgermane (TMG),
tetrakis(dimethylamino)germanium (TDMAGe), germanium
tetraisopropoxide, and germanium tetraisobutoxide, singly or in any
combination of two or more, can be used. In some examples, the
precursor consists essentially of any of the foregoing compounds.
The term "consisting essentially of" is used to the full extent
permitted by law and regulation.
[0022] As described above, the precursor can include Si, Ti or Ge.
In the time period T1, the precursor can adsorb to the underlying
film of the substrate 20.
(B) Source Purging
[0023] In a time period T2 in FIG. 2, the precursor without
adsorbing to the substrate 20 remaining in the reaction space 10A
is purged. This purge can be achieved by continuously supplying the
reactant gas to the reaction space 10A.
(C) RF Application
[0024] In a time period T3 in FIG. 2, the reactant gas is
introduced into the reaction space 10A while pulse RF power having
a duty cycle less than 60% is applied to the RF plate 14. In an
"ON" time period, the RF power is applied to the RF plate 14. In an
"OFF" time period, the RF power is not applied to the RF plate 14.
The "ON" time period and the "OFF" time period are adjusted to make
the duty cycle (duty ratio) less than 60%. According to another
example, the duty cycle of the pulse RF power can be equal to or
less than 50%. According to still another example, the duty cycle
of the pulse RF power can be more than 0% and equal to or less than
15%. Application of the pulse RF power to the RF plate 14 can
generate the plasma of the reactant gas and form an oxide film on
the substrate 20.
[0025] At least one of CxOy and NxOy (x and y are integers) can be
used as the reactant gas. In some examples, the reactant gas is at
least one of CO.sub.2 and N.sub.2O, for example.
[0026] In some examples, the plasma is generated using CxOy and/or
NxOy with or without a rare gas. As CxOy, CO, C.sub.2O, CO.sub.2,
C.sub.3O.sub.2, CO.sub.3, and C.sub.5O.sub.2 can be used singly or
in any combination of two or more. As NxOy, NO, N.sub.2O, NO.sub.2,
N.sub.2O.sub.3, N.sub.2O.sub.4, and N.sub.2O.sub.5 can be used
singly or in any combination of two or more. In some examples, the
plasma of CxOy and/or NxOy is a CO.sub.2 plasma. In some examples,
in step (C), an oxygen plasma is further added to the reaction
space except for the beginning of step (C), where a plasma of CxOy
and/or NxOy does not provide sufficient oxidizability so that an
oxide film with desired properties is not obtained, or where a
plasma of CxOy and/or NxOy increases concentration of impurities in
an oxide film. In the beginning of step (C), a plasma of CxOy
and/or NxOy may be used without an oxygen plasma so as to inhibit
oxidation of an underlying layer, and after an oxide film is formed
on an interface surface of the underlying layer and becomes thick
enough (e.g., a thickness of about 0.5 nm to about 2.0 nm,
depending on the RF power) for alleviating the oxidation problem
(where the oxide film itself functions as a barrier layer blocking
oxidation of the underlying layer), an oxygen plasma is added to or
partially or completely replaces the plasma of CxOy and/or NxOy. In
some examples, the oxide film is composed of a lower oxide layer
formed using a plasma of CxOy and/or NxOy without a plasma of
oxygen, and an upper oxide layer formed using a mixed plasma of
oxygen and CxOy and/or NxOy (wherein a flow ratio of oxygen to CxOy
and/or NA may be in a range of more than 0/100 to about 100/0). In
some examples, in step (C), no oxygen plasma is used in the
reaction space throughout step (C).
[0027] As described above, when the oxide film is formed, in
addition to the plasma of the reactant gas, oxygen plasma may be
generated. In this example, the reactant gas and the oxygen gas are
provided for the reaction space 10A while the pulse RF power is
applied to the RF plate 14. According to another example, when the
oxide film is formed, the oxide gas is not provided for the
reaction space 10A, and the plasma of a reactant gas that is of at
least one of CxOy and NxOy (x and y are integers) is generated.
Elimination or reduction in density of the oxygen plasma can reduce
the damage to the underlying film of the substrate 20.
Specifically, in a case where the underlying film contains carbon,
the effect of reducing the damage is high.
[0028] The time period T3 may be 100 to 1000 milliseconds, for
example. The frequency of the pulse RF power may range from 10 to
100,000 Hz. According to another example, the frequency of the
pulse RF power is equal to or more than 500 Hz. FIG. 3 illustrates
an example of the spectrum of the pulse RF power. FIG. 3
illustrates a waveform obtained by a spectrum analyzer. The cycle
time is 4 milliseconds. In the time period of 4 milliseconds, RFON
occurs only one time. That is, in the T3.sub.ON time period, the
pulse RF power is applied to the RF plate. In the T3.sub.OFF time
period, the pulse RF power is not applied to the RF plate. In this
example, the sum of the T3.sub.ON time period and the T3.sub.OFF
time period is 4 milliseconds. The frequency of the pulse RF power
at this time is 250 Hz. In this example, the duty cycle of the
pulse RF power is 15%.
(D) Post Purge
[0029] In the time period T4 in FIG. 2, the gas in the reaction
space 10A is purged. The purge from the reaction space 10A may be
achieved by providing the reaction space with the reactant gas, for
example.
[0030] A predetermined number of times of repetition of the
processes A to D described above forms the oxide film on the
substrate. The formed oxide film may include SiO, TiO or GeO, for
example. The film thickness of the oxide film may be equal to or
less than 4 nm, for example.
[0031] In the above example, the reaction space is supplied with
the reactant gas entirely through the precursor providing, the
source purging that is the precursor purging, the oxide film
forming by application of RF, and the post purge that is the
reaction space purging. However, the reactant gas may be provided
for the reaction space only during the RF application. During the
other time periods, the carrier gas may be provided for the
reaction space.
[0032] FIG. 4 exemplifies the relationship between the duty cycle
of the pulse RF power and the amount of film loss of the underlying
film of the substrate. FIG. 4 illustrates a case of using CO.sub.2
as the reactant gas and using the pulse RF power of 500 Hz, a case
of using CO.sub.2 as the reactant gas and using the pulse RF power
of 250 Hz, and a case of using O.sub.2as the reactant gas and the
continuously oscillating RF power. Use of O.sub.2 as the reactant
gas, and use of the continuously oscillating RF power increase the
amount of film loss of the underlying film. Specifically, the
underlying film is reduced by 2.5 nm or more. With the continuous
oscillation, a strong plasma reaction may heavily damage the
underlying film.
[0033] On the contrary, use of CO.sub.2 as the reactant gas and use
of the pulse RF power reduce the amount of film loss. The duty
cycle of the pulse RF power and the amount of film loss have a
substantially proportional relationship. However, in a domain where
the duty cycle is less than 50%, the frequency dependency appears.
Specifically, in the domain where the duty cycle is less than 50%,
the configuration having the pulse RF power with a frequency equal
to or less than 250 Hz can facilitate reduction in the amount of
film loss. The reduction in the duty cycle can increase the radical
reaction, and reduce the damage to the underlying film.
* * * * *