(1.1 p)
`
`2322::22173:"
`
`Ofllce européen des brevets
`
`llllllllllllllllllllllllllllllllIllllllllllllllllllllllllllllllllll
`
`EP 1 113 088 A1
`
`{11)
`
`[12)
`
`EUROPEAN PATENT APPLICATION
`
`(43) Date of publication:
`04.07.2001 Bulletin 2001127
`
`{51) lot Cl.7.‘ C23C 14/35, H01J 37134
`
`[21) Application number: 001261205
`
`(22) Date of filing: 29.11.2000
`
`(84) Designated Contracting States:
`AT BE CH CY DE DK ES Fl FR GB GR lE IT LI LU
`MC NL PT SE TFI
`
`Designated Extension States:
`AL LT L'll' MK HO SI
`
`(30) Priority: 30.11.1999 JP 33924199
`20.04.2000 JP 2000131042
`29.00.2000 JP 2000194476
`04.07.2000 JP 2000202225
`04.03.2000 JP 2000237317
`04.09.2000 JP 2000237310
`
`[71) Applicant: CANON KABUSHIKI KAISHA
`Tokyo (JP)
`
`
`
`{72) inventors:
`- Yameguchl, leohito
`Ohta-ku, Tokyo (JP)
`- Kanal.Masahim
`Ohte-ku, Tokyo {JP}
`0 Kolke.Atsushi
`Ohta-ku. Tokyo (JP)
`- Ova, Katsunorl
`Ohta-ku. Tokyo (JP)
`
`{74) Representative:
`Leann, Thomas Johannes Alois. Dipl.-lng. et al
`Patentanwfilte
`
`Tledtke-Btihllng-Klnne 8: Partner,
`Bavariaring 4
`30336 Mlinchen (DE)
`
`(54) Method and apparatus for coating by plasma sputtering
`
`The present invention provides a film forming
`(5?)
`method comprising the steps of ionizing sputtering par-
`ticles and applying a periodically changing voltage to an
`electrode near a substrate. wherein a time for applying
`a voltage equal to or higher than an intermediate value
`between maximum and minimum values at the periodi—
`cally changing voltage is shorter than a time for applying
`a voltage equal to or less the intermediate value, and a
`film forming apparatus for carrying out the above meth—
`od.
`
`3:16.?
`
`'
`
`f”
`-
`
`'
`
`
`
`
`
`Framed by Jenna. P5001 PARlS [FP1
`
`INTEL 1222
`
`EP1113088A1
`
`INTEL 1222
`
`

`

`EP 1 113 030 A1
`
`Description
`
`BACKGROUND OF THE INVENTION
`
`Field of the Invention
`
`[0001} The present invention relates to a film-forming method and apparatus which can be used to produce semi-
`conductor devices, such as LSls, and recording media, such as magneto-optical disks, and more particularly, to an
`ionization film—tormi ng method and apparatus which can form various types of deposited films by using ionized particles.
`
`Related Background Art
`
`Film-forming methods are used to form wirings and interlayer insulating films on a variety of semiconductor
`[0002]
`devices or form magnetic and protective layers on recording media. These film-forming methods, which must exhibit
`various types of performance. have recently been required to provide a film having an improved coverage of an inside
`of a groove formed in a substrate, especially a bottom of the groove.
`[0003]
`Fig. 5 shows a cross section of a film deposited by a conventional sputtering method. The film 102 on the
`bottom 104 of a groove is by farthinner than the film 100 on a top portion 103 of a substrate 7 outside the groove. This
`means that the sputtering method provides poor coverage. Fig. 5 also shows that a film is deposited on the side 101
`of the groove. Poor coverage and film formation on the side of a groove adversely affect film formation on a substrate.
`[0004] Below is described an magneto-optical disk of a magnetic domain wall displacement type. which is disclosed
`in Japanese Patent Application Laid-Open No. 6-290496. Grooves which are concentrically formed in conventional
`magneto-optical disks and compacldisks are not used to record information. However, because information is recorded
`also on the bottom of a groove in a recording medium of a magnetic domain wall displacement type. a functional film
`must be formed on the bottom similarly as on the flat parts (hereinafter, referred to as "lands"] of the medium outside
`the groove. In addition, the medium must be adapted so that no magneto-optical signal is produced from the side of
`the groove. which separates the bottom of the groove and the lands, to prevent interference between the groove and
`the lands. To do so. a deposition amount of a film on the side of the groove must be minimized. That is. a recording
`medium of a magnetic domain wall displacement type requires film formation which is highly directional and has a high
`bottom coverage ratio. The bottom coverage ratio is defined as the ratio of a film formation rate on the bottom surface
`of the groove to a film formation rate on a surface outside the groove. The bottom coverage ratio can be obtained by
`the formula of tAftB w: 100 (Va). wherein try is the thickness of a film formed on the bottom surface of a groove and is is
`the thickness of a film formed on a surface outside the groove [see Fig. 4}.
`[0005} Conventional film forming methods which provide a high bottom coverage ratio include the low-pressure re-
`mote sputtering method. collimate sputtering method, and a high—frequency plasma assisted sputtering method which
`is disclosed in Japanese Patent Application Laid-Open No. 10-259480.
`[0006] The low—pressure remote sputtering method allows sputtering particles to fly straight without scattering be—
`cause the method uses a lower pressure and a longer mean free path than ordinary sputtering methods. The low-
`pressure remote sputtering method is also adapted to provide a longer distance between a target and a substrate and
`make particles fly at a right angle to the substrate.
`[000?] The collimate sputtering method makes only sputtering particles flying at a right angle to a substrate to reach
`It and deposits theparticles thereon by placing a cylinder having a plurality of holes made at a right angle to the substrate
`between a target and the substrate.
`[0008] The high-freq uency plasma assisted sputtering method aliowe flying sputtering particles to deposite by ion-
`izing them in a space of plasma, which is produced near a substrate by applying a high-frequency voltage to the
`substrate. and directing the ionized sputtering particles at a right angle to the substrate, using a negative voltage [sell
`bias} produced on the substrate due to plasma.
`[0009] However, the low-pressure remote sputtering method is said to be limited to substrates with a groove aspect
`ratio up to about 4 in mass production because of its low film formation rate and low raw—material (target) use efficiency
`due to the long distance between the target and substrate.
`[0010] The collimate sputtering method has a problem of low film formation rate and low raw-material use efficiency
`due to a loss caused by sputtering particles deposited on the collimator, and is limited to substrates with a groove
`aspect ratio up to about 3.
`[0011] The high-frequency plasma assisted sputtering method can be used for substrates with a groove aspect ratio
`of 4 or more. However. the sputtering method allows charged particles In plasma to penetrate a substrate, thus heating
`it because plasma is produced by applying a high—frequency voltage to the substrate. Thus in the sputtering method.
`it is difficult to form a film on a substrate made of a material which has low heat resistance, such as resin used as the
`substrate material for recording media. including compact disks and magneto-optical disks.
`
`hr
`
`10
`
`f5
`
`30
`
`35
`
`40
`
`50
`
`55
`
`

`

`SUMMARY OF THE INVENTION
`
`EP 1 113 088 A1
`
`it is an object of the present invention. intended to solve the above-described problems, to provide a film
`[0012]
`forming method and film forming apparatus which can be used to form a film at a high bottom coverage ratio even on
`a substrate with deep grooves on its surface.
`[0013]
`it is another object of the present invention to provide a film forming method and a film icrrning apparatus
`which can prevent substrate temperature from Increasing.
`[0014]
`It is still another object of the present Invention to provide an ionization film forming method and an ionization
`film iorrning apparatus which promote discharge gas excitation and ionization. thereby increasing the efficiency of
`ionization of evaporated particles.
`[0015] These objects are attained by a method for forming a deposited film by sputtering. comprising the steps of:
`
`ionizing sputtering particles and
`applying a periodically changing voltage to an electrode provided near a substrate.
`
`wherein a time for which avoltage equal to or larger than an intermediate value between maximum and minimum
`values of the above-described voltage is applied is shorter than a time lorwhich a voltage equal to or smaller than the
`intermediate value is applied.
`[0016] The objects are also attained by an ionization sputtering apparatus for forming a deposited film by directing
`sputtering particles to a substrate using an electric field produced near the substrate. comprising:
`
`a sputtering chamber with an evacuating system:
`gas introducing means for introducing a processing gas into the sputtering chamber;
`a target placed in the sputtering chamber:
`ionizing means provided between the target and the substrate:
`an electrode disposed near the substrate; and
`voltage applying means for applying a periodically changing voltage to the electrode under such a condition that
`the time for which a voltage equal to or larger than an intermediate value between maximum and minimum values
`of the applied voltage is applied is shorterthan the time for which avoltage equal to or smailerthan the intermediate
`value is applied. Detailed descriptions will be given later with reference to examples.
`
`BRIEF DESCRiPTlON OF THE DRAWINGS
`
`[0017]
`
`Fig. 1 is a schematic sectional view illustrating a structure of a film forming apparatus according to an embodiment
`oi the present invention;
`Fig. 2 is a schematic sectional view illustrating an embodiment of an ionizing mechanism of the present invention:
`Fig. 3 shows a waveform of a voltage applied to an electrode 10 according to the present Invention;
`Fig. 4' is a schematic view illustrating a method for calculating a bottom coverage ratio according to the present
`invention:
`Fig. 5 is a sectional view of a film deposited by a conventional sputtering method:
`Fig. 6 shows a relationship between a frequency of voltage applied to the electrode 10 and the bottom coverage
`ratio in Example 3 of the present invention:
`Fig. 7 shows a relationship between a duty ratio of the voltage applied to the electrode 10 (the ratio of a time T1
`for which a voltage V1 is applied to a time T2 forwhich a voltage V2 is applied. as shown in Fig. 3} and the bottom
`coverage ratio in Example 4 of the present invention:
`Fig. 8 shows a relationship between the duty ratio of a voltage applied to the electrode 10 and a dielectric strength
`in Example 6 oi the present invention;
`Fig. 9 is a schematic sectional view illustrating the structure of an ionization film-ton'ning apparatus in Example 8
`of the present invention;
`Fig. 10 is a schematic view illustrating magnetic lines of force which are formed when magnetic—field applying
`means installed in the ionization iiirn-tom-ring apparatus in Example 8 of the present invention is singly used;
`Fig. 11 is a schematic view illustrating magnetic lines of force which are ion‘ned by the magnetic-field applying
`means between a target and an ionizing mechanism and by magnetidiield applying means below the target in
`Fig. 9;
`Fig. ‘12 is a schematic sectional view illustrating the structure of an ionization film-forming apparatus in Example
`ii oi the present invention:
`
`10
`
`15
`
`30
`
`35
`
`«it?
`
`50
`
`55
`
`

`

`EP1113088A1
`
`Fig. 13 is a schematic sectional view Illustrating the structure of an Ionization film-forming apparatus in Example
`15 of the present invention;
`Fig. ‘14 is a schematic sectional view Illustrating the structure of an ionization film-forming apparatus in Example
`18 of the present invention;
`Fig. 15 is a schematic sectional view illustrating the structure of an ionization film-forming apparatus In Example
`20 of the present invention;
`Fig. 16 shows a relationship betWeer'I the size ratio betWeen a substrate and the electrode 10 and the bottom
`coverage ratio in Example 20 of the present invention;
`Fig. 17 shows a relationship between the size ratio between a substrate and the electrode 10 and the bottom
`coverage ratio in Example 21 of the present invention:
`Fig. 18 is a schematic sectional view illustrating the structure of an ionization film-forming apparatus in Example
`22 of the present invention:
`Figs. 19A and 193 are a top view of Ionizing means 5 In an ionization film-forming apparatus in Example 22 of the
`present invention and a side view of the apparatus. respectively:
`Fig. 20 illustrates relationships between a film forming time and a substrate temperature which are established in
`cases where a shield plate is provided. the shield plate is cooled. and no shield plate is provided in Example 22
`of the present invention;
`Fig. 21 illustrates differences in the bottom coverage ratio depending on whether shield plates made of glass.
`Teflon. and polycarbonate are watercooled or not:
`Fig. 22 is a schematic sectional view illustrating the structure of an ionization film-forming apparatus in Example
`25 of the present invention:
`Fig. 23 is a sectional view of a substrate on which a film is formed in Example 25 of the present invention;
`Fig. 24 shows the results of CN ratio measurements using a magnetic domain wall displacement type recording
`medium in Example 25 of the present invention;
`Fig. 25 is a schematic sectional view illustrating another embodiment of the ionization film-forming apparatus in
`Example 25 of the present invention; and
`Fig. 26 is a graph forshowing the dependency of amagnetic flux density at point A on the rate of lorming a deposited
`film on a substrate.
`
`DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
`
`[0018} Referring now to the drawings. the present invention will be described below.
`[0019}
`Fig. 1 is a schematic view illustrating an ionization film—forming apparatus according to an embodiment of the
`present invention. In Fig. 1 . a reference n umeral it] indicates an electrode on the back side of a substrate. and reference
`numerals ii and 12 indicate voltage applying means for applying a periodically changing voltage to the electrode 10.
`[0020] According to a film forming mechanism of the present invention. particles evaporated from a target 2 are
`ionized using an ionizing mechanism 6. and the ionized sputtering particles with directivity are incident on asubstrate
`7 under the action of an electric field 9 on the substrate 7.
`[0021] Afilm forming chamber 1 , which is a metal container made of stainless steel. aluminum. orthe like. is grounded
`to be at a reference electric potential and is kept airtight by a gate valve not shown.
`[0022] An evacuating system 14 is a complex evacuator which can evacuate in a range of the atmospheric pressure
`to about 10'6 Pa. The evacuation speed ofthe evacuating system can be adlusted using an evacuation speed adjuster.
`not shown. such as an orifice or a conductance valve.
`[0023]
`For the embodiment, the target 2 is a disk 3 mm thick and about 3 inches (75.2 mm) in diameter, which is
`Installed through a backing plate and an insulator in a sputtering chamber 1. A mechanism may be provided which
`cools the target as required. using a refrigerant. such as water.
`[0024] A magnet 3 as magnetic-field producing means is installed on the back side of the target 2 so that magnetron
`sputtering can be carried out.
`[0025]
`A sputtering power supply 4. which feeds a predetermined electric power to the target 2 to cause glow dis—
`charge. ls adapted to apply to the target 2 a negative DC voltage of -2CIO V or 4300 V with respect to the reference voltage.
`[0026}
`Processing gas Introducing means 5 introduces a sputtering discharge gas. such as a rare gas. Because the
`gas is efficiently ionized. it is preferable that the processing gas be introduced at the center of an ionizing space. A
`circular pipe with many gas blow-out holes formed on its center side is more preferably used because the gas is
`uniformly Introduced.
`[0027] The Ionizing mechanism 6. which is of a hot cathode type using Penning ionization. ionizes sputtering ions
`by hitting thermoelectrons. emitted from a hot cathode. against sputtering particles and sputtering discharge gas par-
`ticles in an ionizing space 608 provided In a sputtering particle travel path ircm the target 2 to the substrate 7 or
`produces sputtering discharge gas excitation seeds and ions. Discharge gas excitation seeds and ions also collide
`
`to
`
`10
`
`1‘5
`
`30
`
`35
`
`«it?
`
`50
`
`55
`
`

`

`EP1113088A1
`
`hr
`
`10
`
`15
`
`30
`
`35
`
`«it?
`
`50
`
`55
`
`with sputtering particles in the ionizing space to lonize the sputtering particles. As described above. sputtering particles
`are ionized mainly through the two mechanisms.
`[0028]
`Fig. 2 shows the structure of the ionizing mechanism 6. Specifically. by feeding current from a DC power
`supply 604 to a filament 601 connected thereto in series. the ionizing mechanism 6 heats the filament 601. thereby
`making it emit thermoelectrons. A grid 602 has a network structure. A DC power supply 605 applies a positive voltage
`thereto. so that thermoelectrons from the filament 601 are accelerated toward the grid 602. The thermoelectrons ac-
`celerated are not Immediately captured by the grid 602 but travels through the grid 602 the ionizing space 606 in the
`travel path of sputtering particles. The thermoelectrons collide with sputtering particles and sputtering discharge gas
`particles to ionize or excite these particles and then are captured by the grid 602. The filament 601 is made of a material
`with a large coefficient of thermoelectron emission. such as Flew or W. and the grid 602 has a network structure.
`consisting ofwires. for example.1 mm in diameter which arespaced abouts mm apartfrorn each other. Forthe ionizing
`mechanism. one side of the filament 601 is at the same potential as a casing 603. Thus a DC voltage which is negative
`with respect to a reference voltage may be applied to the casing 603 by a DC powar supply 607 to prevant electron
`diffusion. or the casing 603 may be kept at the reference potential.
`[0029] A substrate holder 8, disposed in the chamber 1. is adapted so that the holder can keep the substrate 7
`parallel to thetarget 2. An insulator 1 7 is interposed between the substrate holder 6 and the substrate 7. The electrode
`10 is preferably installed in parallel with the substrate 7.
`[0030] The electrode 10 is connected with voltage applying means consisting of a function synthesizer 11. serving
`as a signal generator. and a power amplifier 12. The voltage applying means applies periodically changing voltage to
`the electrode 10.
`
`Fig. 3 exemplifies a bias voltage applied to the electrode 10. The bias voltage varies in a predetermined period
`[0031]
`between a maximum voltage V1 (a voltage at which the amplitude takes a minimum with respect to a floating potential)
`and a minimum voltage V2 {a voltage at which the amplitude takes maximum with respect to a floating potential). The
`floating potential is a potential which an electricaiiy insulated substrate placed in plasma generates under the action
`of plasma. In this embodiment. the floating potential Is a potential generated at the substrate 7 when no voltage is
`applied to the electrode 10.
`[0032] Such a bias voltage produces an electric field 9 near the substrate 7 substantially at a right angle to the
`substrate 7. so that ionized sputtering particles are accelerated along the electric field 9 to reach the substrate 7.
`Because ionized particles are incident on the substrate 7 in the direction of the electric field 9. it is desirable that the
`electric field 9 be uniformly formed over the substrate as directed at a right angle to the substrate as possible. Any
`waveform and voltage can be applied from the signal generator 11 and power amplifier 12 to the electrode 10.
`[0033] An ionization film-forming method according to an embodiment of the present invention will be described
`below.
`
`[0034] After the substrate 7 is installed in the substrate holder 6. the chamber is evacuated to about 10'5 Pa using
`the complex evacuating system 14. Then the ionizing mechanism 6 is operated. That is. first. the DC power supply
`607 is operated and set to a value. Next. the filament DC power supply 604 is operated to heat the filament 601 by
`energizing it. Finally. using the grid DC powersupply 605. apositive DC voltage of about +10 to about +200 V is applied
`to the grid 602 to cause it to emit thennoeiectrons in the ionizing space 606.
`[0035] Depending on the rate of film formation by sputtering. it is desirable that the value of a current (emission
`current) flowing into the grid 602 be set to 5A or more during film formation.
`[0036] Then using the processing gas introducing means 5. a sputtering gas such as Ar is introduced. and the evac-
`uation speed adjusterfor the complex evacuating system 14 is controlled to keep the chamber 1 at 0.2 to 2.5 Pa. Next.
`by operating the sputtering power supply 4. sputtering discharge is performed to start sputtering. At the same time. by
`operating the signal generator 11 and the poWer amplifier 12. a periodically changing voltage is applied to the electrode
`10 to produce the electric field 9 substantially perpendicular to the surface of the substrate 7.
`[0037] For example. a voltage which has the rectangular waveform in Fig. 3 is applied to the electrode 10 as described
`above so that electrons can be incident on the substrate at the maximum voltage V1 near the rectangular-wave floating
`potential. Specifically. it is desirable that the maximum voltage V1 be chosen within the range of 0 to ~10 V because
`the floating potential is often within or around the range. Depending on sputtering conditions. the floating potential may
`be more than -0 V. In this case. the maximum voltage V1 should be chosen according to the floating potential. As
`described above. as a voltage applied near the substrate 7. which is determined on basis of the maximum voltage V1
`around the floating potential or above it is applied so that electrons can be incident on the substrate. and the minimum
`voltage V2 is applied so that positive Ions can be incident on the substrate. In addition. to prevent a film formation rate
`from significantly decreasing under the effect of reverse sputtering. it is desirable that the minimum voltage V2 be set
`to -20 to -100 V.
`
`[0033] To make ions efficiently incident on the substrate while preventing substrate charge—up. it is desirable that the
`frequency be 100 kHz or more and that the waveform duty ratio be set to 1 :50 or more. that is. the ratio of the time for
`which the maximum voltage V1 is applied to the timefor which the minimum voltage V2 is applied be set to 1i50 or less.
`
`

`

`EP1 1130881“
`
`[0039] After presputtering is performed for a few minutes. with the conditions unchanged, a substrate shutter 13 is
`opened to start film formation. Particles sputtered by sputtering discharge are ionized in the ionizing space 606. directed
`to the substrate 7. and accelerated underthe action of the electric field 9 near the substrate 7. so that the particles are
`attracted to the substrate 7 and deposited efficiently on the bottoms of grooves in the substrate.
`[0040] After a film with a predetermined thickness is formed. the sh utter 13 is closed. and the signal generator 11 .
`power amplifier 12. sputtering power supply 4. and processing gas introducing means 5 are first stopped and then the
`filament power supply 504. grid power supply 605. and floating power supply 607 in the ionizing mechanism 6 are
`stopped. Finally, a gate valve not shown is closed. the sputtering chamber 1 is emptied. and the substrate 7 is removed
`from the substrate holder 3.
`
`For the ionizing mechanism 6, it is not preferable to deposit sputtering particles on the filament 601 . This is
`[00411
`because a deposited film on a filament changes its resistance and causes the filament to easily break. To prevent this
`problem. the filament power supply 604 is desirably kept in service whenever the sputtering power supply 4 is in
`operation.
`[0042]
`In this embodiment described above. various materials for forming a film to be evaporated. including metals.
`alloys. and compounds. may be used. The embodiment uses a mechanism which hits thermoelectrons against evap—
`orated particles and discharge gas particles to ionize the evaporated particles. According to the ionization film-forming
`method ofthe present invention. however. various ionizing means. such as laserassisted ionization and high-frequency
`coil plasma assisted ionization methods. which can ionize the evaporated particles between the evaporation source
`and the substrate. can be used.
`[0043] By taking examples. the present Invention will be more specifically described below. Although the following
`examples are typical of the best embodiments of the present invention. the examples do not limit the present invention.
`
`{Example 1 i
`
`[0044]
`below.
`
`Following the procedures for the above-described embodiment. a film was formed under conditions given
`
`Material for the target 2‘. GdFeCr (ternary alloy}
`Power fed to the target 2: 400W
`Pressure in the sputtering chamber: 0.8 Pa
`Discharge gas: Argon
`Discharge gas flow rate: 200 sccm
`Ionizing mechanism grid voltage: 50 V
`Ionizing mechanism emission current: 20 A
`Ionizing mechanism floating power supply voltage: -30 V
`
`[0045} Under these conditions. with the frequency and duty ratio of a voltage to be applied to the electrode 10 set
`to 500 kHz and 1: 100. films were successively formed on a substrate 7 for five minutes with different minimum and
`maximum voltages V2 and V1 applied to the electrode 10 to make sample substrates. When they were made. temper-
`ature was measured on the surface of the sample substrates. Fig. 1 showa the results. They show that properly setting
`voltage to be applied to the substrate significantly reduces an increase in substrate temperature.
`[0046]
`For example. setting V1 and V2 to ~5 to —10 V and -40 to -100 V. respectively allows a film to be formed at
`about 60°C as thetemperature of the substrate 7. This. in turn. means that a film can smoothly be formed on asubstrate
`made of a material with low heat resistance. such as polycarbonate. For example. polycarbonate. polymethyl metah-
`crylate. and epoxy resin are said to have a thermal defamation temperature of 95 to 105°C. 120 to 132°C. and about
`135°C. respectively. The present example allowed a good film to be formed on substrates made of such materials wilh
`low heat resistance.
`
`In the film formation under the conditions of the present example. the iioating potential was In a range of 0 to
`[004?]
`10 V as described above. From the results of the present example. the maxim um voltage V1 was set to a value obtained
`by subtracting 10 V from the floating potential, thereby obtaining a more suitable result.
`
`{Example 2)
`
`[0048] According to Example 1 . films were formed on an Si substrate having grooves with a bottom width of 0.25pm
`and an aspect ratio of 4 under the following conditions. In the present example. sample substrates were made at
`different maximum and minimum voltages V1 and V2. The bottom coverage ratio of these sample substrates was
`measured. Table 2 shows the results.
`
`[0049]
`
`For information. Table 2 also gives bottom coverage ratios obtained with conventional low—pressure remote
`
`10
`
`f5
`
`30
`
`35
`
`«it?
`
`50
`
`55
`
`

`

`EP1113088A1
`
`sputtering and high-frequency plasma assisted ionization sputtering apparatuses.
`[00501
`For example. conventional low-pressure remote sputtering methods provide a bottom coverage ratio of about
`16% while the present example provided a bottom coverage ratio of about 40% especially when a maximum voltage
`V1 of -10 V and a minimum voltage V2 of -40 V were applied to the electrode 10.
`[0051]
`In the film formation under the conditions of the present example. the floating potential was In a range of 0 to
`10 V as described above. From the results ofthe present example. the maximum voltage V1 was set to a value obtained
`by subtracting 10 V from the floating potential. thereby obtaining a more suitable resu it.
`
`[Example 3]
`
`[0052] Aocorclingto Example 1 . films were formed on an Si substrate 7 having grooves with a bottom width of 0.25pm
`and an aspect ratio of4 by applyingthe maximum voltage V‘i of—1CI V and minimum voltage V2 of -40 V to the electrode
`10 and changing the frequency of the voltaged applied to the electrode 10. The bottom coverage ratio of the obtained
`samples ware measured.
`[0053]
`Fig. 6 shows the results of the measurements, which indicate that the present example significantly increases
`the bottom coverage ratio, compared with conventional sputtering methods. For example. conventional low-pressure
`remote sputtering methods provide a bottom coverage ratio of about 16% while the present example provided a bottom
`coverage ratio oi about 40% especially when the frequency of voltage to be applied to the electrode 10 was set to 100
`Hz or more.
`
`In the film formation under the conditions of the present example. the floating potential was in a range of D to
`[0054]
`1 D V as described above. From the results of the present example, the maxim um voltage V1 was set to a value obtained
`by subtracting 10 V from the floating potential, thereby obtaining a more suitable result.
`
`{Example 4)
`
`[0055] Accordingto Example 1 . films were formed on an Si substrate 7 having grooves with a bottom width of 0.25pm
`and an aspect ratio of 4 at different duty ratios {the duty ratio is the ratio of the time T1 for which the maximum voltage
`V1 is applied to the time for which the minimum voltage V2 is applied) of a voltage applied to the electrode 10. with
`the maximum voltage V1 and minimum voltage V2 set to -10 V and -4Cl V. respectively. The bottom coverage ratio of
`the obtained samples were measured. Fig. 7 shows the results of the measurements, which indicate that the present
`example significantly increases the bottom coverage ratio. compared with conventional sputtering methods. For ex-
`ample, conventional low-pressure remote sputtering methods provide a bottom coverage ratio of about 15% while the
`present example provided a bottom coverage ratio of about 40% especially when the duty ratio of the voltage to be
`applied to the electrode 10. that is. T1/T2 was set to 1.350 orless.
`[0056]
`In the film formation under the conditions oi the present example. the floating potential was in a range oi 0 to
`10 V as described above. From the results of the present example. the maxim um voltage V1 was set to a value obtained
`by subtracting 10 V from the floating potential. thereby obtaining a more suitable result.
`
`{Example 5]
`
`[0057} According to Example 1. using Sic}2 forthe target 2 and RF power supply as the sputtering powersupply 4.
`SiO2 film was formed on an SI substrate with grooves. with different maximum and minimum voltages applied to the
`electrode 10. By reactive Ion etching, a plurality oi sample Si substrates were provided which had grooves with a bottom
`width or 0.5um and an aspect ratio of 4. In addition. according to Example 1. using GdFeCr for the target 2. GdFeCr
`films were formed on Si substrates with grooves. with different maximum and minimum voltages applied to the electrode
`‘10. The Silt)2 and GdFeCr films were 100 nm and 80 nm thick outside the grooves. respectively. Dielectric strength
`was measured between the Si substrate and the GdFeCr iilm formed thereon at the bottom of each sample substrate.
`
`(Comparative Example}
`
`[0058] By sputtering, Sit)2 iilm 20 nm thick and GdFeCr film 80 nm thick were formed on the lands of Si substrates
`under the same film formation conditions as in Example 5. except that the Ionizing mechanism was not operated.
`[0059] Dielectric strength was measured between the SI layer and the GdFeCr layer on it at the bottom of each
`sample substrate.
`[0060] Table 3 gives the dielectric strength of the sample film formed in Example 5 and the dielectric strength of the
`sample film obtained by conventional sputtering in the comparative example.
`[0061] Table 3 shawls that the dielectric strength is about 2 V in the comparative example while property choosing
`the values of V1 and V2 caused the dielectric strength to significantly increase up to 13V to Example 5.
`
`m
`
`10
`
`f5
`
`30
`
`35
`
`«it?
`
`50
`
`55
`
`

`

`(Example 6]
`
`EP 1 113 088 A1
`
`[0062] According to Example 5. films were formed on a substrate 7 at different duty ratios of voltage applied to the
`electrode 10, with the maximum voltage V1 and minimum voltage V2 set to -10 V and .40 V. respectively. and the
`dielectric strength of the obtained samples were measured Fig. 8 shows the results. For comparison purposes. Fig. 8
`also shows the dielectric strength of a sample obtained by a conventional sputtering method.
`[0063]
`Fig. 3 shows that Example 6 allowed a sample substrate with a significantly increased dielectric strength
`exceeding 13V to be provided by setting the duty ratio to 1 :50 or more.
`
`(Example 7)
`
`[0064] According to Example 1. using SiNa for