U.S. patent application number 14/180729 was filed with the patent office on 2014-06-12 for reactive sputtering method and reactive sputtering apparatus.
This patent application is currently assigned to CANON ANELVA CORPORATION. The applicant listed for this patent is CANON ANELVA CORPORATION. Invention is credited to Takashi NAKAGAWA, Yuichi OTANI.
Application Number | 20140158524 14/180729 |
Document ID | / |
Family ID | 44186125 |
Filed Date | 2014-06-12 |
United States Patent
Application |
20140158524 |
Kind Code |
A1 |
OTANI; Yuichi ; et
al. |
June 12, 2014 |
REACTIVE SPUTTERING METHOD AND REACTIVE SPUTTERING APPARATUS
Abstract
The present invention provides a reactive sputtering method and
a reactive sputtering apparatus which suppress a film quality
change caused by a temperature variation in continuous substrate
processing. An embodiment of the present invention performs
reactive sputtering while adjusting a flow rate of reactive gas
according to the temperature of a constituent member facing a
sputtering space. Specifically, a temperature sensor is provided on
a shield and the flow rate is adjusted according to the
temperature. Thereby, even when a degassing amount of a film
adhering to the shield changes, a partial pressure of reactive gas
can be set to a predetermined value. For a resistance change layer
constituting a ReRAM, a perovskite material such as PrCaMnO3
(PCMO), LaSrMnO3 (LSMO), and GdBaCoxOy (GBCO), a two-element type
transition metal oxide material which has a composition shifted
from a stoichiometric one, such as nickel oxide (NiO), vanadium
oxide (V2O5), and the like are used.
Inventors: |
OTANI; Yuichi; (Tama-shi,
JP) ; NAKAGAWA; Takashi; (Hachioji-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CANON ANELVA CORPORATION |
Kawasaki-shi |
|
JP |
|
|
Assignee: |
CANON ANELVA CORPORATION
Kawasaki-shi
JP
|
Family ID: |
44186125 |
Appl. No.: |
14/180729 |
Filed: |
February 14, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12974923 |
Dec 21, 2010 |
|
|
|
14180729 |
|
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Current U.S.
Class: |
204/192.13 |
Current CPC
Class: |
C23C 14/0042 20130101;
H01J 37/3438 20130101; H01L 45/146 20130101; C23C 14/088 20130101;
H01L 45/08 20130101; H01J 37/3447 20130101; H01L 45/1233 20130101;
C23C 14/544 20130101; H01L 45/1625 20130101 |
Class at
Publication: |
204/192.13 |
International
Class: |
C23C 14/00 20060101
C23C014/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 26, 2009 |
JP |
2009-296538 |
Claims
1. A reactive sputtering method of sputtering a target disposed in
a chamber, supplying reactive gas into the chamber, and forming a
deposited film on a to-be-processed substrate disposed in the
chamber by reactive sputtering, the method comprising the steps of:
measuring a temperature of a constituent member that is provided in
the chamber and faces a processing space; and adjusting a flow rate
of the reactive gas according to a rise of the measured temperature
so as to reduce the flow rate of the reactive gas supplied into the
chamber.
2. The reactive sputtering method according to claim 1, wherein the
flow rate of the reactive gas supplied into the chamber is adjusted
according to the measured temperature so that a partial pressure of
the reactive gas in the chamber falls within a predetermined
range.
3. The reactive sputtering method according to claim 1, wherein the
flow rate of the reactive gas is adjusted so that a specific
resistance value of the deposited film becomes a predetermined
specific resistance value, using a map that preliminarily defines a
relationship of the specific resistance value of the deposited film
against the flow rate of the reactive gas at each temperature and a
measured value of the measured temperature.
4. The reactive sputtering method according to claim 1, wherein the
processing space is surrounded by the target, the to-be-processed
substrate, and a shield, a temperature sensor capable of measuring
a temperature of the shield is attached on the side of the
to-be-processed substrate of the shield, and the temperature of the
constituent member is measured by the temperature sensor.
5. The reactive sputtering method according to claim 3, wherein the
temperature sensor is a thermocouple or a radiation
thermometer.
6. The reactive sputtering method according to claim 1, wherein the
deposited film is an insulating film including an oxygen
defect.
7. The reactive sputtering method according to claim 6, wherein an
element contained in the insulating film includes at least one of
Ta, Ni, V, Zn, Nb, Ti, Co, W, Hf, and Al.
8. The reactive sputtering method according to claim 6, wherein the
insulating film has a laminated structure in which it is sandwiched
by metals containing at least one of Ni, W, Pt, Ti, Al, Ru, Ta, and
Cu.
9-11. (canceled)
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a reactive sputtering
method and a reactive sputtering apparatus which provide an
excellent film quality stability.
[0003] 2. Description of the Related Art
[0004] For realizing a highly functional digital device, it is
indispensable to develop a memory to be used having a higher
capacity, a higher speed, a lower power consumption, a longer
lifetime, and the like. Especially, a flash memory is used for
various applications and expected to have a further higher
performance. However, a flash memory using a floating gate, which
is mainstream at present, has a problem that a threshold voltage
variation is caused by interference through a capacitive coupling
between memory cells neighboring each other along with
miniaturization of the memory cell and it is generally known that
there exists a limit for the miniaturization.
[0005] Hence, a device drawing attention for replacing the flash
memory is a ReRAM which is provided with a metal oxide and has a
recording principle suitable for the miniaturization. ReRAM is an
abbreviation of Resistivity Random Access Memory, and the ReRAM is
a nonvolatile memory which can be caused to change a state
(specifically, resistance value) of metal oxide with a pulse
voltage and can preserve the information unless a pulse voltage is
applied again. Further, the ReRAM can reduce cost utilizing the
simplicity of the device structure and operation, and is considered
to be operated even in an order of 50 ns or less, and thereby
various ideas are being proposed using this device.
[0006] For the resistance change layer of the ReRAM, there are used
a perovskite material such as PrCaMnO3 (PCMO), LaSrMnO3 (LSMO) and
GdBaCoxOy (GBCO), and a two-element type transition metal oxide
material which has a composition shifted from a stoichiometric one,
such as nickel oxide (NiO), vanadium oxide (V2O5), zinc oxide
(ZNO), niobium oxide (Nb2O5), titanium oxide (TiO2), cobalt oxide
(CoO), tantalum oxide (Ta2O5) and tungsten oxide (WO2).
[0007] A means for fabricating a metal compound such as the metal
oxide layer and the like includes reactive sputtering which
performs sputtering of a metal target using reactive gas such as
oxygen gas and nitrogen gas, and the process having an extinguished
controllability and reproducibility is considered to be required
for the production.
[0008] When performing continuous film deposition using the
reactive sputtering, however, there arises a problem that a film
characteristic is different for each processing. This phenomenon is
shown in FIG. 8. The data of FIG. 8 shows a specific resistance
change of a film (here, Ta oxide) deposited on a substrate against
the number of times of processing when the processing is performed
by oxygen reactive sputtering of a metal target Ta using a DC
magnetron sputtering apparatus. This data shows that the specific
resistance increases as the number of times of processing increases
and it is found that the specific resistance increases in 26% from
the first time to the 50th time.
[0009] The cause of the specific resistance increase includes that
an oxygen gas amount taken-in (gettered) by a metal compound
adhering to a shield provided in a sputtering apparatus changes
depending on a case. The reason that the amount of gettered oxygen
gas changes is considered to be a temperature change of the shield.
The surface temperature of the shield is low while the number of
times of processing is small and a degassing amount (ejected gas
amount) from the metal compound adhering to the shield is small,
and thereby the oxygen gettering effect is large in the metal
compound. On the other hand, as the number of times of processing
increases, the shield accumulates plasma heat and the shield
temperature increases due to the accumulated heat, and then the
degassing amount increases. The oxygen gettering effect decreases
gradually as this degassing amount increases, resulting in the
increase of the specific resistance along with the increase of the
number of times of processing.
[0010] As a means for suppressing the change of the reactivity for
each number of times of processing, there is a method of performing
a dummy run before the continuous processing for a sufficiently
long time until the shield comes to have a temperature which is to
be reached during the sputtering process. This method, however,
results in a shorter target shield life and a reduced throughput,
and does not provide a sufficiently effective countermeasure.
[0011] Further, Japanese Patent Laid-Open No. H5-175157 proposes to
heat the shield (200.degree. C. to 500.degree. C.) preliminarily
using heater heating, gas heating or the like. This proposal
intends to stabilize the reactivity by realizing a thermal
equilibrium state preliminarily within a sputtering chamber and to
suppress a thermal variation during the sputtering process.
However, the inside of the chamber is heated to 200.degree. C. or
more and thereby the deposition cannot be carried out in a
sufficiently cooled atmosphere and further it takes a long time
until the shield surface reaches a thermal equilibrium similarly to
the above case. Further, when using a material in which a crystal
state changes between at a low temperature and at a high
temperature such as Al oxide (.gamma.-alumina, .alpha.-alumina, or
the like) or a material which forms various coupling states with
oxygen such as Ta oxide (TaO2, Ta2O5, or the like), it is difficult
to control the reaction precisely in the film deposition by the
above method.
SUMMARY OF THE INVENTION
[0012] The present invention aims at providing a reactive
sputtering method and a reactive sputtering apparatus which are
capable of suppressing a film quality variation as described above
in continuous film deposition of reactive sputtering without losing
a target shield life or a throughput.
[0013] First aspect of the present invention is a reactive
sputtering method of sputtering a target disposed in a film
deposition processing chamber, supplying reactive gas into the film
deposition processing chamber, and forming a deposited film on a
to-be-processed substrate disposed in the film deposition
processing chamber by reactive sputtering, the method comprising
the steps of: measuring a temperature of a constituent member which
is provided in the film deposition processing chamber and faces a
sputtering space; and performing the reactive sputtering while
adjusting a flow rate of the reactive gas according to a rise of
the measured temperature so as to reduce the flow rate of the
reactive gas supplied into the film deposition processing
chamber.
[0014] Second aspect of the present invention is a reactive
sputtering apparatus forming a deposited film on a to-be-processed
substrate by reactive sputtering, the apparatus comprising: a
container; an electrode which is provided in the container and to
which a target can be attached; a substrate holder which is
provided in the container and can hold the to-be-processed
substrate; a shield which is provided in the container and disposed
so as to face a sputtering space in the reactive sputtering; a
reactive gas introduction means for introducing reactive gas into
the container; a temperature sensor capable of measuring a
temperature of the shield; and controller controlling the reactive
gas introduction means according to an output of the temperature
sensor so as to reduce a flow rate of the reactive gas supplied
into the container according to a rise in the temperature of the
shield.
[0015] Thereby, it is possible to control a partial pressure of the
reactive gas (e.g., oxygen partial pressure) according to the
temperature and it is possible to secure the stability in the
continuous film deposition while reducing the influence of the
degassing amount from the constituent member within the vacuum
container.
[0016] According to the present invention, it becomes possible to
suppress the variation of the film characteristic depending on the
number of times of processing in the continuous film deposition of
the reactive sputtering without losing the target shield life and
the throughput.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a diagram showing an outline of a processing
apparatus which suppresses the variation of a specific resistance
in reactive sputtering, according to a first embodiment of the
present invention.
[0018] FIG. 2 is a graph showing a specific resistance
characteristic against an oxygen flow rate at each shield
temperature, in a first embodiment of the present invention.
[0019] FIG. 3 is a diagram showing a reactive sputtering apparatus
according to a second embodiment of the present invention.
[0020] FIG. 4A is a diagram showing a reactive sputtering apparatus
according to a third embodiment of the present invention.
[0021] FIG. 4B is a diagram showing a reactive sputtering apparatus
according to a third embodiment of the present invention.
[0022] FIG. 5 is a flowchart showing the operation of a reactive
gas control mechanism in a fourth embodiment of the present
invention.
[0023] FIG. 6 is a diagram explaining a temperature estimation
method in a fourth embodiment of the present invention.
[0024] FIG. 7 is a schematic diagram showing a cross-sectional
structure of a ReRAM according to an embodiment of the present
invention.
[0025] FIG. 8 is a graph showing a relationship between the number
of times of processing and a specific resistance.
DETAILED DESCRIPTION OF THE INVENTION
[0026] Hereinafter, with reference to the drawings, there will be
explained a continuous film deposition method of the reactive
sputtering which suppresses a film characteristic variation using
the present invention. Note that an element having the same
function is denoted by the same reference numeral in the drawing to
be explained hereinafter and repeated explanation thereof will be
omitted.
First Embodiment
[0027] FIG. 1 is a schematic diagram of a sputtering apparatus
suitable for implementing a method of the present embodiment. A
film deposition processing chamber 100 is configured so as to be
heated to a predetermined temperature by a heater 101. Further, the
film deposition processing chamber (container) 100 is configured
such that a to-be-processed substrate 102 is heated to a
predetermined temperature by a heater 105 via a susceptor 104
embedded in a substrate holder 103. The substrate holder 103, which
is a substrate holder capable of holding the substrate, preferably
can rotate at a predetermined rotating speed from the viewpoint of
film thickness uniformity. In the film deposition processing
chamber, a target 106 is disposed at a position facing the
to-be-processed substrate 102. The target 106 is disposed at a
target holder 108 via a back plate 107 made of metal such as Cu.
Note that a form of target assembly combining the target 106 and
the back plate 107 may be fabricated as a component by the use of
target material and this form may be attached as the target. That
is, the target may be configured to be disposed directly on the
target holder.
[0028] The target holder 108 made of metal such as Cu is connected
with a DC power source 110 applying sputtering discharge power and
insulated from the wall of the film deposition processing chamber
100, which has a ground potential, by an insulator 109. Behind the
target 106, when viewed from the sputtering surface, there is
disposed a magnet 111 for realizing magnetron sputtering. The
magnet 111 is held by a magnet holder 112 and can be rotated by a
magnet holder rotation mechanism which is not shown in the drawing.
For uniform erosion of the target, the magnet 111 is rotated during
the discharge. The target 106 is disposed at an offset position
obliquely upward from the substrate 102. That is, the center point
of the sputtering surface on the target 106 is located at a
position shifted by a predetermined dimension from the normal line
at the center point of the substrate 102. A shield plate 116 is
disposed between the target 106 and the to-be-processed substrate
102 and controls the film deposition onto the to-be-processed
substrate 102 with sputtered particles ejected from the target 106
to which power is supplied. The sputtering is performed when the
power is supplied to the metal target 106 respectively via the
target holder 108 and the back plate 107 from the DC power source
110.
[0029] At this time, an inert gas is introduced into the processing
chamber 100 at a position around the target from an inert gas
source 201 via a valve 202, a mass flow controller 203, and a valve
204. Further, a reactive gas is introduced into the processing
chamber 100 at a position around the substrate from a reactive gas
source 205 via a valve 206, a mass flow controller 207, and a valve
208. Accordingly, the reactive gas source 205, the valve 206, the
mass flow controller 207, and the valve 208 function as a mechanism
involved in the reactive gas introduction. The introduced inert gas
and reactive gas are exhausted by an exhaust pump 118 via a
conductance valve 117. A shield 120 having a shape surrounding a
processing space is disposed via a shield support rod 119 for
preventing or reducing film adhesion to the side wall of the film
deposition processing chamber during the sputtering. The shield 120
is disposed so as to face the sputtering space at a position
surrounding the sputtering space formed in the film deposition
processing chamber 100.
[0030] On the side wall of the shield 120 (to-be-processed
substrate side of the shield 120), there is provided a shield
temperature sensor 121 which has a thermocouple or the like capable
of measuring the temperature of the shield 120 (hereinafter, also
called "shield temperature"). Note that, while the shield
temperature sensor 121 is preferably attached on the side of the
to-be-processed substrate 102 for accurately obtaining the
temperature change in a constituent member of the substrate
periphery (member except the to-be-processed substrate 102 and
constituent member provided in the film deposition processing
chamber), the shield temperature sensor 121 may be attached to a
position such as the rear side of the shield 120 where the film is
not deposited from the viewpoint of apparatus operation. Further,
the shield temperature sensors 121 may be provided at plural
positions of the shield 120, and a shield temperature to be used
for the control (a degassing amount or a reactive gas partial
pressure) may be calculated, for example, by the use of an average
temperature of the temperatures at the plural positions or
weighting of temperature data when the shield temperature sensors
121 are provided at positions where the film is easily deposited
and not easily deposited, respectively. Further, the shield
temperature may be estimated by providing the sensor on a member
around the shield without providing it directly on the shield.
[0031] A reactive gas control mechanism 209 which feedbacks an
output from the shield temperature sensor 121 is configured to
control the mass flow controller 207.
[0032] The reactive gas control mechanism 209 stores a relationship
of a specific resistance of a film (film to be deposited), which is
deposited on the to-be-processed substrate 102 with particles
sputtered from the target 106 provided in the film deposition
processing chamber 100 and the reactive gas, against a reactive gas
flow rate at each shield temperature in a preliminarily defined
map, as shown in FIG. 2, for example. FIG. 2 shows the specific
resistance characteristic against an oxygen flow rate at each
temperature obtained when the reactive gas flow rate is changed in
each film deposition at a constant temperature and the specific
resistance is measured in each deposited film. The example of FIG.
2 shows a result measured at each of shield temperatures,
28.degree. C. and 37.degree. C., for a case of using oxygen as a
reactive gas and Ta as a target material. It is found that the
specific resistance against the oxygen flow rate becomes higher at
a higher temperature by the influence of the degas from the metal
compound adhering to the shield 120.
[0033] That is, the present embodiment measures the specific
resistance of a deposited film at each reactive gas flow rate when
the reactive gas flow rate is changed within a predetermined range
for various temperatures at each number of times of processing.
Accordingly, when the continuous processing is to be carried out
100 times, for example, an oxygen flow rate (reactive gas flow
rate) and the specific resistance of a deposited film are obtained
as shown in FIG. 2 preliminarily at each temperature within a
predetermined range for each of the number of times of processing 1
to 100, and the data showing the relationship is stored as a map in
the reactive gas control mechanism 209. Accordingly, the reactive
gas control mechanism 209 can obtain the relationship between the
reactive gas flow rate and the specific resistance of the deposited
film corresponding to a temperature detected by the shield
temperature sensor 121 in the current number of times of
processing.
[0034] The reactive gas control mechanism 209 calculates a reactive
gas flow rate for obtaining a predetermined specific resistance
using the above map and the shield temperature data from the shield
temperature sensor 121 (e.g., shield temperature at each film
deposition start), and controls the reactive gas flow rate to
become the calculated flow rate via the mass flow controller. Note
that the information used for controlling the reactive gas flow
rate based on the shield temperature in the reactive gas control
mechanism 209 is not limited to that shown in FIG. 2. For example,
the relationship between the reactive gas flow rate and the
specific resistance of the deposited film may be defined at more
temperature zones. Alternatively, when a desired specific
resistance value has been determined, only a correspondence between
the shield temperature and the reactive gas flow rate may be
defined or the reactive gas flow rate may be obtained by a
calculation formula or the like which defines the relationship
between the shield temperature and the reactive gas flow rate.
Further, it is optional to control the reactive gas flow rate
according to the degassing amount or the reactive gas partial
pressure estimated from the shield temperature. Further, while the
reactive gas flow rate is controlled basically such that the
reactive gas partial pressure becomes constant for each substrate
processing, the target reactive gas partial pressure itself may be
varied.
[0035] In this manner, since the degassing amount of the metal
compound adhering to the shield 120 changes and the reactivity is
varied on the to-be-processed substrate according to the
temperature of shield 120, it is possible to obtain the film
characteristic of a desired specific resistance without receiving
the influence of the degassing amount variation caused by the
thermal variation of the film deposition processing chamber 100, by
the feedback of the specific resistance data against the reactive
gas flow rate preliminarily obtained at each shield temperature
zone.
[0036] The present embodiment performs the reactive sputtering
while adjusting the reactive gas flow rate so as to reduce the flow
rate of reactive gas supplied into the film deposition processing
chamber 100 according to the temperature rise of the shield 120.
That is, the present embodiment forms a desired deposited film on
the to-be-processed substrate 120 by adjusting the reactive gas
flow rate so that the reactive gas partial pressure (e.g., oxygen
partial pressure when the reactive gas is oxygen) in the film
deposition processing chamber 100 (in the container) falls within a
predetermined range according to the temperature of the shield 120
while monitoring the temperature of the shield 120. Specifically,
the reactive gas control mechanism 209, as the result of
monitoring, controls the mass flow controller 207 so as to reduce
the reactive gas flow rate when the shield temperature is high and
to increase the reactive gas flow rate when the shield temperature
is low. Accordingly, even when the temperature of the metal
compound adhering to the shield 120 is changed because of the
shield temperature change and the degassing amount of the adhering
metal compound changes, it is possible to control the supply of the
reactive gas (e.g., oxygen) so as to compensate the variation of
the reactive gas partial pressure (e.g., oxygen partial pressure)
caused by the degassing amount change in the film deposition
processing chamber 100. For example, even when the shield
temperature is increased to T1 and the oxygen gettering effect of
the adhering metal compound is reduced by the increased degassing
amount, the reactive gas flow rate for the temperature T1 is
reduced compared to the reactive gas flow rate for a temperature T2
which is lower than the temperature T1. Thereby, it is possible to
make the reactive gas partial pressure in the film deposition
processing chamber 100 approximately the same between the
temperature T1 and the temperature T2. That is, even when the
shield temperature changes, it is possible to select the reactive
gas flow rate which realizes a desired specific resistivity of the
deposited film at the shield temperature and it is possible to
always keep a reactive gas partial pressure (e.g., oxygen partial
pressure) so as to obtain the desired specific resistivity of the
deposited film. Accordingly, even when the shield temperature is
changed and thereby the degassing amount is changed by the
continuous film deposition of the reactive sputtering, the
variation of the reactivity between the reactive gas and the
sputtered particles can be reduced on the to-be-processed substrate
102 and the variation in the specific resistivity of the deposited
film can be reduced.
[0037] Meanwhile, it is important in the present embodiment to
reduce the variation of the reactive gas partial pressure in the
film deposition processing chamber 100 caused by degassing amount
variation of a member which faces the sputtering space and on which
the metal compound is formed with the sputtered particles generated
from the target 106 by the reactive sputtering (hereinafter, also
called "adhesive member") among constituent members except the
to-be-processed substrate 102 in the film deposition processing
chamber, the degassing amount variation being generated from the
temperature change of the adhesive member. The degassing amount
varies according to the temperature of the adhesive member, and
thereby the present embodiment measures the temperature of the
adhesive member and controls the reactive gas flow rate according
to the temperature of the adhesive member in order to make the
reactive gas partial pressure constant in the film deposition
processing chamber 100.
[0038] In this manner, in the present embodiment, it is not
essential how to select the kind of the reactive gas or how to
determine the flow rate, but it is essential how to set the
reactive gas partial pressure within an allowable range in the film
deposition processing chamber 100. Accordingly, the materials of
reactive gas and target are not limited to oxygen and Ta,
respectively, and any reactive gas and any material may be
used.
[0039] Further, the present embodiment focuses on the degassing
amount of the metal compound which is originated in the sputtered
particles from the target 106 when the adhesion member faces the
sputtering space, but does not focus on where the metal compound is
formed. Accordingly, the adhesive member is not limited to the
shield 120 and any constituent member facing the sputtering space
may be selected. In this case, the temperature of the selected
member may be measured and the reactive gas flow rate may be
controlled according to the measured temperature.
Second Embodiment
[0040] Next, a second embodiment will be explained.
[0041] FIG. 3 shows a reactive sputtering apparatus according to
the second embodiment. While the reactive sputtering apparatus of
the second embodiment has approximately the same configuration as
that of the reactive sputtering apparatus in the first embodiment,
a different point is that the reactive sputtering apparatus of the
second embodiment does not have the shield 120 but uses a radiation
thermometer 122 monitoring the strength of infrared light and
visible light. Further, a shield plate 116 has not only a through
hole 131 facing a target 106 but also a through hole (opening) 132
facing the radiation thermometer 122, and a space around a
substrate can be observed via the through hole 132. That is, the
radiation thermometer 122 is a member around a to-be-processed
substrate 102 except the to-be-processed substrate 102 and is
configured to measure the temperature of a member (adhesive member)
facing the sputtering space via the through hole 132. The through
hole 132 for the radiation thermometer 122 is formed to be smaller
than the through hole for the target 106 for preventing or reducing
the adhesion of the sputtered particles.
[0042] A reactive gas control mechanism 209 calculates a required
reactive gas flow rate based on temperature information input from
the radiation thermometer 122 and controls the reactive gas flow
rate to become the calculated value. While a measurement timing is
not limited particularly, it is preferable to perform the
measurement in the interim of the film deposition because the
temperature around the substrate can be measured accurately in the
case of using the radiation thermometer 122.
[0043] In this manner, by using the radiation thermometer, it is
possible to measure the temperature of the constituent member
around the substrate without depending on a configuration of the
apparatus and it is possible to accurately estimate the reactive
gas partial pressure around the substrate which particularly
affects the film deposition characteristic.
[0044] Note that obviously the present embodiment may use the
radiation thermometer together with another temperature sensor.
Third Embodiment
[0045] Next, a third embodiment will be explained with reference to
FIGS. 4A and 4B. While a reactive sputtering apparatus of the third
embodiment has approximately the same configuration as that
according to the second embodiment, a different point is a
configuration of a shield plate 116. In the third embodiment, the
shield plate 116 is provided with a through hole 131 having
approximately the same diameter as that of a target 106 and
configured to be rotatable according to an instruction from a
reactive gas control mechanism 209, and thereby the through hole
131 can be moved by the rotation to respective positions facing a
radiation thermometer 122 and the target 106.
[0046] In the interim of film deposition (e.g., after film
deposition or before film deposition), the through hole 131 is
caused to face the radiation thermometer 122 for enabling
temperature measurement (FIG. 4A) and also, during the film
deposition, the through hole 131 is moved to the position facing
the target 106 and the film deposition is carried out (FIG. 4B). In
the present embodiment, the shield plate 116 is provided with the
through hole 131 which allows the sputtered particles to pass
through, and thereby the target 106 is opened to the sputtering
space via the through hole 131 when the through hole 131 faces the
target 106 and the radiation thermometer 122 is opened to the
sputtering space via the through hole 131 when the through hole 131
faces the radiation thermometer 122. With such a configuration, the
through hole 131 can be utilized when the target is not used in the
interim of film deposition, and also the radiation thermometer 122,
which is not used during the film deposition, can be covered with
the shield plate 116. Thus, it is possible to effectively prevent
the generation of particles and the like toward the radiation
thermometer 122.
Fourth Embodiment
[0047] Next, a fourth embodiment will be explained.
[0048] While a reactive sputtering apparatus according to the
fourth embodiment has approximately the same configuration as that
according to the first embodiment, the operation of a reactive gas
control mechanism 209 is different and especially a temperature
estimation operation is different. FIG. 5 is an operation flow of
the reactive gas control mechanism 209 in the present embodiment,
and FIG. 6 is a diagram showing an image of temperature transition
during the continuous film deposition processing for explaining the
temperature estimation method.
[0049] The present embodiment shows a calculation method of shield
temperature estimation value effectively applied for a case such as
one in which a target flow rate of the reactive gas keeps a
predetermined value without being changed during the substrate
processing and the target flow rate is changed as required when the
substrate is exchanged.
[0050] Specifically, shield temperature sampling is performed
across plural times (e.g., before the film deposition processing
and after the film deposition processing), and a shield temperature
estimation value TM which is used for the calculation of a target
flow rate for each time is calculated using a temperature increase
amount Tu during the film deposition processing and a temperature
decrease amount Td in the interim of the processing. That is, as
shown in FIG. 6, the shield temperature estimation value TM is
calculated using a temperature increase function when the
temperature is increased by input heat from plasma during the film
deposition and a temperature decrease function when the temperature
falls along with substrate transfer and the like in the interim of
the film deposition.
[0051] The operation flow shown in FIG. 5 is as follows. First the
shield temperature is measured before the film deposition (e.g.,
after evacuation succeeding the substrate transfer is completed)
(Step S102) and a film deposition start temperature Ts (x) is
obtained (x: number of times of substrate processing). Then, a
shield temperature estimation value TM is calculated (Step S103)
and a target reactive gas flow rate is calculated using the
calculated value, and then the reactive gas flow rate is adjusted
to the value (Step S104). After the film deposition (e.g., after
exhaustion before the carry-out of substrate is completed), a film
deposition end temperature Te(x) is obtained (Step S106). The
operations in Steps S101 to S107 are repeated until a predetermined
number of times of the substrate processing are completed.
[0052] In Step S103, the shield temperature estimation value TM is
calculated by following Formula (1) for the xth time substrate
processing.
TM=Ts(x)+1/2.times.Tu(x-1).times.Te(x)/Te(x-1) Formula (1)
where Tu(x-1) is a temperature increase amount during the (x-1)th
(previous) film deposition processing and Te(x) is a temperature
decrease amount from the end of the (x-1)th processing to the start
of the xth processing.
[0053] In this manner, by adding both of the temperature increase
function when the temperature is increased by the input heat of the
plasma during the film deposition and the temperature decrease
function when the temperature falls along with the substrate
transfer and the like in the interim of the film deposition, it is
possible to estimate the shield temperature accurately and
calculate an appropriate reactive gas target flow rate using the
estimated temperature, even in the continuous film deposition in
which the temperature increase and the temperature decrease
continue intermittently.
[0054] As other method, a shield temperature estimation value TM in
a processing of the calculation target may be calculated based on
an approximate function f(t) of a shield temperature measurement
value Tm(x) at a certain processing time in each processing, for
example. In this case, however, a temperature measurement value
Tm(x-1) in the previous processing can be used for the estimation,
for example, and the latest temperature information cannot be
reflected. On the other hand, the method using the temperature
decrease amount in the interim of the film deposition can reflect
the information before the current film deposition which is the
latest information, and the shield temperature estimation value TM
can be calculated accurately.
[0055] Note that the calculation formula of the shield temperature
estimation value TM is not limited to above Formula (1). For
example, the temperature increase function and the temperature
decrease function may be not only functions for temperature changes
in a temperature increase time zone and a temperature decrease time
zone such as a temperature increase amount and a temperature
decrease amount but also functions or approximate functions, s(t)
or e(t), for the shield temperatures at certain times, for example,
in the temperature increase time zone and the temperature decrease
time zone, respectively. Further, the estimation method using the
temperature increase function and the temperature decrease function
may be used during some time after the start of the continuous film
deposition, for example, in which the temperature rises quickly,
and the estimation method may be changed using the above f(t), for
example, after the state is stabilized.
[0056] (Production Method)
[0057] FIG. 7 is a schematic diagram showing a cross-sectional
structure of a ReRAM according to an embodiment of the present
invention. A resistance change element (memory element) 311 of a
typical ReRAM has a parallel plate type laminated structure in
which a resistance change film (e.g., transition metal oxide film)
313 is sandwiched between a lower electrode 312 and an upper
electrode 314. When a voltage is applied across the upper electrode
314 and the lower electrode 312, the electric resistance of the
resistance change film 313 is changed and takes two different
resistance states (reset state and set state). It is described that
a material containing at least one kind of element selected from
Pt, Ru, Ti, Al, Ta, Cu, W and Ni is used for an electrode material
to be used for the ReRAM.
[0058] The operation mechanism of the resistance change element 311
is as follows. First a forming voltage is applied as an initial
operation for enabling the transition between the two resistance
states. The application of the forming voltage generates a state of
forming a filament which becomes a current path in the resistance
change film 313. After that, the filament generation state is
changed by the application of an operation voltage (set voltage or
reset voltage) and a set/reset operation, that is, write/erase
operation is carried out. While the number of filaments is
increased as an area of an operation region is increased in the
resistance change element 311, the increase in the number of
filaments causes a variation in reset current control and
resultantly memory operation is varied. The resistance change
element preferably has a smaller operation area not only from a
requirement of a higher density but also for realizing a stable and
highly reliable operation. In the conventional structure, however,
the miniaturization is limited by a fabrication preciseness of a
photolithography, as described above.
[0059] Further, APPLIED PHYSICS LETTERS 86, 093509 (2005) proposes
a nonvolatile memory device having a resistance change layer of NiO
and using upper and lower electrodes of Pt and describes that a
current path called a filament is formed in the Ni oxide and
resistance is changed. International electron devices meeting
technical digest, 2008, p 293-p 296 also proposes a nonvolatile
memory device having a resistance change layer of TaOx and using
upper and lower electrodes of Pt, and describes that resistance is
changed by the movement of an oxygen element in an interface layer
between a Pt electrode and TaOx.
[0060] Further, a technique regarding a resistance change element
using an electrode of titan nitride, which is an electrode material
for easy etching processing, is drawing attention. Symposium on
VLSI technology digest of technical papers, 2009, p 30-p 31
proposes a nonvolatile memory device using a lower electrode of Pt,
a resistance change layer of HfOx or HfAlOx and an upper electrode
of TiN, and describes that the variation of an operation voltage is
suppressed by the use of HfAlOx as the resistance change layer.
International electron devices meeting technical digest, 2008, p
297-p 300 also describes that the resistance change operation can
be realized by a laminated structure of TiN/TiOx/HfOx/TiN
fabricated from a laminated structure of TiN/Ti/HfO.sub.2/TiN by
annealing using oxygen.
[0061] For the resistance change film 313 of the resistance change
element 311, there is used an oxide having a composition shifted
from a stoichiometric one such as an insulating film having an
oxygen defect, and the resistance change film 313 can be deposited
by the reactive sputtering according to an embodiment of the
present invention. That is, an advantage of the present invention
can be obtained in the ReRAM fabrication process using the reactive
puttering in which at least one of Ta, Ni. V, Zn, Nb, Ti, Co, W, Hf
and Al is used for the deposition of the resistance change film
313.
Example 1
[0062] Table 1 shows a result of the continuous film deposition of
the reactive sputtering for a case of controlling the oxygen flow
rate in consideration of the shield temperature. Fifty times of
film deposition were carried out under the following condition.
Film Deposition Condition:
[0063] Target: Ta
[0064] Target input power: DC 1000 W
[0065] Ar gas flow rate: 20 sccm
[0066] Reactive gas: Oxygen
[0067] Pressure during film deposition: 0.06 Pa
[0068] Evaluation substrate: Si substrate with a thermally-oxidized
film
[0069] Film thickness: 30 nm
[0070] Specific resistance: approximately 20 mohmcm
[0071] Film depositions of an example and a comparison example were
carried out under the above condition and the oxygen flow rate for
the comparison example sample was kept constant during the
deposition while the oxygen flow rate was controlled according to
the shield temperature for the example.
[0072] From the result, it was confirmed that the variation of the
specific resistance could be suppressed to approximately 2% from
the first film to the 50th film.
TABLE-US-00001 TABLE 1 Value normalized by Reactive a specific
Shield gas resistance of temperature flow rate the first Sample
(.degree. C.) (sccm) film Example 28 23 1.00 (first film) Example
(50th 37 22 1.02 film) Comparison 28 23 1.00 example (first film)
Comparison 37 23 1.26 example (50th film)
* * * * *