170990s
`
`I,
`
`of
`
`VERIFICATION OF TRANSLATION
`
`Rumiko Whitehead
`
`1950 Roland Clarke Place
`
`Reston, VA 20191
`
`declare that I am well acquaintecl with both the Japanese and English languages, and that
`the attached is an accurate translation, to the best of my knowledge and ability, of
`Japanese Unexamined Patent Application Publication No. Hl0-330938, published
`
`December 15, 1998.
`
`I further declare that all statements made herein of my own knowledge are true and that
`all statements made on information and belief are believed to be true; and further that
`these statements were made with the knowledge that willful false statements and the like
`so made are punishable by fine or imprisonment, or both, under Section 1001 of Title 18
`of the United States Code and that such wì1lful false statements may jeopardize the
`validity of the above-captioned application or any patent issued thereon.
`
`S
`
`?" h ú'¿-
`
`Rumiko Whitehead
`
`Date
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`3
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`24/
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`u709905 03031921 .DOC\
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`Page 1 of 14
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`IP Bridge Exhibit 2029
`TSMC v. IP Bridge
`IPR2016-01264
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`(19) Japan Patent Office (JP)
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`(12) Unexamined Patent Application
`Publication (A)
`
`(11) Patent Application Publication
`No.
`
`
`H10-330938
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`(43) Publication Date December 15, 1998
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`(51) Int.Cl6
`C23C 14/46
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`14/34
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`Identification
`Symbol
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` FI
`C23C 14/46
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`14/34
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`Z
`M
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`Request for Examination Not requested Number of claims 6 FD (9 pages total)
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`(21) Application No.
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`(22) Application Date
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`H09-155981
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`May 28, 1997
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`(71) Applicant
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`
`
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`(72) Inventor
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`
`
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`(72) Inventor
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`
`
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`(74) Agent
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`000227294
`Anelva Corporation
`5-8-1, Yotsuya, Fuchu-shi, Tokyo
`Masao Sasaki
`Anelva Corporation
`5-8-1, Yotsuya, Fuchu-shi, Tokyo
`Kiyohiko Funato
`Anelva Corporation
`5-8-1, Yotsuya, Fuchu-shi, Tokyo
`Patent Agent Koichi Hotate
`
`(54) [Title of Invention] Ionizing Sputtering Device and Method of Ionizing Sputtering
`
`
`
`
`
`(57) [Abstract]
`[Problem] To form a film with good bottom coverage
`by ionizing sputtering with respect to holes having a
`high aspect ratio, and to simplify inside and outside
`structures of a sputter chamber.
`[Means to Resolve the Problem] A target 2, provided
`inside a sputter chamber 1 equipped with an
`evacuation system 11, is sputtered using a sputtering
`power source 3 so that sputter particles emitted
`therefrom are made to arrive at a substrate 50 to form
`a film. The sputtering power source 3 supplies an
`electric power of 5W/cm2 or higher to the target 2,
`and sputter particles are ionized in a plasma P formed
`only by this electric power. A cylindrical shield 6 is
`provided between the target 2 and a substrate holder
`5 and regulates a plasma-forming space, and an
`electric field establishment means 8 establishes an
`electric field to extract the ionized sputter particles
`from the plasma P and cause them to enter the
`substrate 50.
`
`
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`[Scope of Claims]
`[Claim 1] An ionizing sputtering device consisting of a sputter chamber equipped with an evacuation
`system, a target provided inside the sputter chamber, a gas introduction means which introduces a
`predetermined gas into the sputter chamber, a sputtering power source which sputters the target by
`generating sputter discharge in the gas introduced, and a substrate holder which holds a substrate in a
`position at which sputter particles released from the target by sputtering enter the substrate;
`wherein the aforementioned sputtering power source is capable of ionizing the aforementioned sputter
`particles in a plasma formed by the aforementioned sputter discharge, using only the electric power
`applied by such sputtering power source.
`
`[Claim 2] The ionizing sputtering device according to claim 1, wherein the aforementioned sputtering
`power source applies a high frequency electric power to the target such that a supplied-electric power area
`density of the high frequency electric power divided by the area of the sputtered face of the target is
`5W/cm2 or higher.
`
`[Claim 3] The ionizing sputtering device according to claims 1 or 2, wherein the aforementioned target
`and the aforementioned substrate holder are positioned so as to be coaxially facing each other, and a
`cylindrical shield is coaxially provided in a space between the target and the substrate holder.
`
`[Claim 4] The ionizing sputtering device according to claims 1, 2, or 3, wherein the ionizing sputtering
`device is provided with an electric field establishment means which establishes an electric field for
`extracting the aforementioned ionized sputter particles from the aforementioned plasma and causing them
`to enter the substrate.
`
`[Claim 5] An ionizing sputtering method in which a predetermined electric power is applied to a target
`provided inside a sputter chamber so as to generate a sputter discharge and sputter said target, and sputter
`particles released from said target are caused to arrive at a surface of a substrate to deposit a
`predetermined thin film,
`wherein the inside of the aforementioned sputter chamber is maintained at a pressure between 10 mTorr
`and 100 mTorr and, in a plasma formed by the sputter discharge, the aforementioned sputter particles are
`ionized by just the electric power applied to the aforementioned target, and the aforementioned thin film
`is deposited by causing the ionized sputter particles to arrive at the aforementioned substrate.
`
`[Claim 6] An ionizing sputtering method wherein the predetermined electric power applied to the
`aforementioned target is a high frequency electric power such that a supplied-electric power area density
`of the high frequency electric power divided by the area of the sputtered face of the target is 5W/cm2 or
`higher.
`
`[Detailed Description of Invention]
`[0001]
`[Technical Field of the Invention] The present invention relates to a sputtering device used in the
`manufacture of various types of semiconductor devices and the like, and in particular an ionizing
`sputtering device in which sputter particles are ionized and utilized for the formation of film.
`
`[002]
`[Prior Art] With semiconductor devices, such as various types of memory and logic devices, a sputtering
`process is used in the production of various types of wiring films, and the production of barrier films
`which prevent interdiffusion of different types of layers, and a sputtering device is often used for this
`purpose. There are various characteristics that are required in such sputtering devices; however, there is
`recently a great need for the ability to coat the inner surfaces of holes formed in a substrate with good
`coverage.
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`[0003] To be specific, in a CMOS-FET (field effect transistor), which is frequently used in a DRAM, for
`example, a structure is employed in which cross-contamination of a contact wiring layer and a diffusion
`layer is prevented by providing a barrier film to the inner surface of contact holes provided on the
`diffusion layer. In addition, in a multi-layered wiring structure in which memory cells are wired, a
`through hole is provided on an interlayer insulation film, and interlayer wiring is embedded inside the
`through hole to connect a lower-layer wiring and an upper-layer wiring. Here again, a structure is
`employed in which a barrier film is produced inside the through hole to prevent cross-contamination.
`
`[0004] Due to the increasing degree of integration, the aspect ratio (the ratio of a depth of a hole to a
`diameter or width of an opening of the hole) of such holes is becoming higher, year after year. For
`example, the aspect ratio is around 4 with a 64 megabit DRAM, but the aspect ratio is around 5-6 with a
`256 megabit DRAM.
`
`[0005] In the case of a barrier film, it is necessary to deposit a thin film on the bottom surface of a hole in
`an amount that is 10 to 15% of the amount deposited to the surrounding surfaces of the hole; however,
`with holes with a high aspect ratio, it is difficult to form films with a high degree of bottom coverage (the
`ratio of the film formation speed on the surrounding surfaces of the hole to the deposition speed on the
`bottom surface of the hole). When the bottom coverage decreases, the barrier film on the bottom surface
`of the hole becomes thin, thereby creating the risk of causing critical defects in the characteristics of the
`device, such as junction leaks and the like.
`
`[0006] Methods such as collimation sputtering and low-pressure, long-distance sputtering have been
`developed up to now as a sputtering method which increases bottom coverage. Collimation sputtering is
`a method where a plate (collimator), in which numerous holes have been made in a direction
`perpendicular to the substrate, is provided between the target and the substrate, and only those sputter
`particles (usually sputtering atoms) that fly more or less perpendicular to the substrate are selectively
`allowed to arrive at the substrate. Low-pressure, long-distance sputtering is a method in which the
`distance between the target and the substrate is lengthened (to three to five times the usual distance) to
`cause relatively more sputter particles that fly more or less perpendicular to the substrate to enter the
`substrate, and, by setting the pressure to a level lower than usual (about 0.8 mTorr or lower), the mean
`free path is lengthened and the sputter particles are prevented from dispersing.
`
`[0007] However, with collimation sputtering, there is a problem in which the sputter particles accumulate
`on the collimator portion, and the loss of such sputter particles causes the film formation speed to
`decrease. In low-pressure, long-distance sputtering, there is problem that the film formation speed
`inherently decreases because the distance between the target and the substrate is lengthened by the lower
`pressure. Because of such problems, collimation sputtering is used only in mass-production of 16
`megabit-class products with an aspect ratio of up to around 3, and low-pressure, long-distance sputtering
`is limited to devices having an aspect ratio of up to around 4.
`
`[0008]
`[Problems to Be Solved by the Invention] In light of this situation, an ionizing sputtering method is being
`considered as a technology that allows the formation of a film with good bottom coverage with respect to
`holes having an aspect ratio of 4 or higher. Ionizing sputtering is a method in which sputter particles
`released from the target are ionized, and bottom coverage is improved by the action of these ions.
`
`[0009] However, ionizing sputtering has a number of practical problems. One of these is in the structure
`of the energy supply used for ionization. That is, in order to perform ionizing sputtering, it is effective to
`form a plasma in the flight path of the sputter particles from the target to the substrate. One possible
`structure is to provide a (coil or plate-shaped) electrode separately from the target and to connect a power
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`source that applies electric power to the electrode, in order to form the plasma. However, a drawback to
`such a structure is that the structure inside the sputter chamber is complicated. Moreover, since a power
`source is provided separately from the sputtering power source, the structure around the sputter chamber
`is also complicated. Additionally, the cost is high.
`
`[0010] The present invention was conceived to solve these problems, and the purpose thereof is to
`provide a device and method that enables the formation of a film with good bottom coverage by ionizing
`sputtering with respect to holes having a high aspect ratio, which also simplifies the inside and outside
`structures of a sputter chamber and reduces costs.
`
`[0011]
`[Means to Solve the Problems] In order to solve the problems set forth above, the invention set forth in
`claim 1 of this application is an ionizing sputtering device consisting of a sputter chamber equipped with
`an evacuation system, a target provided inside the sputter chamber, a gas introduction means which
`introduces a predetermined gas into the sputter chamber, a sputtering power source which sputters the
`target by generating sputter discharge in the gas introduced, and a substrate holder which holds a substrate
`in a position at which sputter particles released from the target by sputtering enter the substrate; wherein
`the aforementioned sputtering power source is capable of ionizing the aforementioned sputter particles in
`a plasma formed by the aforementioned sputter discharge, using only the electric power applied by such
`sputtering power source. Additionally, in order to solve the problems set forth above, the invention set
`forth in claim 2 has a structure in which the aforementioned sputtering power source applies a high
`frequency electric power to the target, wherein the supplied-electric power area density of the high
`frequency electric power divided by the area of the sputtered face of the target is 5W/cm2 or higher.
`Additionally, in order to solve the problems set forth above, the invention set forth in claim 3 has a
`structure according to claims 1 or 2 above, wherein the aforementioned target and the aforementioned
`substrate holder are positioned so as to be coaxially facing each other, and includes a cylindrical shield
`coaxially provided in a space between the target and the substrate holder, and is provided with an electric
`field establishment means which establishes an electric field perpendicular to the substrate for extracting
`ions from the plasma formed on the inner side of the aforementioned shield and causing them to enter the
`substrate. Additionally, in order to solve the problems set forth above, the invention set forth in claim 4
`has a structure according to claims 1, 2, or 3 above, and is provided with an electric field establishment
`means which establishes an electric field for extracting the aforementioned ionized sputter particles from
`the aforementioned plasma and causing them to enter the substrate. Additionally, in order to solve the
`problems set forth above, the invention set forth in claim 5 is a sputtering method in which a
`predetermined electric power is applied to a target provided inside a sputter chamber so as to generate a
`sputter discharge and sputter said target, and sputter particles released from said target are caused to
`arrive at a surface of a substrate to deposit a predetermined thin film, wherein the inside of the
`aforementioned sputter chamber is maintained at a pressure between 10 mTorr and 100 mTorr and, in the
`a plasma formed by the sputter discharge, the aforementioned sputter particles are ionized by just the
`electric power applied to the aforementioned target, and the aforementioned thin film is deposited by
`causing the ionized sputter particles to arrive at the aforementioned substrate. Additionally, in order to
`solve the problems set forth above, the invention set forth in claim 6 has a structure according to claim 5
`above, wherein the predetermined electric power applied to the aforementioned target is a high frequency
`electric power such that a supplied-electric power area density of the high frequency electric power
`divided by the area of the sputtered face of the target is 5W/cm2 or higher.
`
`[0012]
`[Embodiments of the Invention] An embodiment of the present invention is described below. Fig. 1 is a
`simplified front view describing a structure of an ionizing sputtering device according to one embodiment
`of the present invention. The sputtering device shown in Fig. 1 has a sputter chamber 1 equipped with an
`evacuation system 11, a target 2 provided inside the sputter chamber 1, a sputtering power source 3 which
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`H10-330938
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`sputters the target 2, a gas introduction means 4 which introduces a predetermined gas into the sputter
`chamber 1, and a substrate holder 5 which holds a substrate 50 in a position at which sputter particles
`released from the target 2 by sputtering enter the substrate 50.
`
`[0013] Firstly, the sputter chamber 1 is an airtight vessel equipped with a gate valve (not shown in
`drawings). This sputter chamber 1 is made of metal such as stainless steel and the like, and is electrically
`grounded. The evacuation system 11 consists of a multi-phased evacuation system equipped with a turbo
`molecule pump and diffusion pump and the like, and is capable of evacuating the sputter chamber 1 to
`about 10-9 Torr. In addition, the evacuation system 11 is equipped with an evacuation speed adjuster (not
`shown in drawings) such as a variable orifice and the like, and it is possible to adjust the evacuation speed.
`
`[0014] The target 2 is in a form of a disk that has a thickness of about 26 mm, and a diameter of about
`314 mm, for example, and is attached to the sputter chamber 1 via a metal target holder 21 and an
`insulator 22. The distance between the target 2 and the substrate holder 5 is about 120 mm. A magnet
`mechanism 30 is provided behind the target 2, to perform magnetron sputtering. The magnet mechanism
`30 is comprised of a center magnet 31, a peripheral magnet 32 that surrounds this center magnet 31, and a
`disk-shaped yoke 33 that connects the center magnet 31 and the peripheral magnet 32. Both of the
`magnets 31 and 32 are permanent magnets; however, they can also be comprised of electromagnets. In
`addition, this magnet mechanism 30 is rotated as necessary so as to even out the erosion of the target 2.
`The rotational axis is perpendicular to the target 2, and is set to be slightly eccentric from the center of the
`target 2.
`
`[0015] The sputtering power source 3 features a significant characteristic of the ionizing sputtering device
`according to the present embodiment. In the present embodiment, the sputtering power source 3 is a high
`frequency power source with a frequency of 13.56 MHz and an output of 8 to 10 kW, and has a
`considerably high output for a power source performing high frequency sputtering. A regulator (not
`shown in drawings) is provided between the sputtering power source 3 and the target 2, to perform
`impedance matching.
`
`[0016] The gas introduction means 4 primarily consists of a gas cylinder 41 filled with a sputtering
`discharge gas such as argon and the like, a tube 42 connecting the gas cylinder 41 and the sputter chamber
`1, and a valve 43 or a flow regulator 44 provided to the tube 42.
`
`[0017] The substrate holder 5 is airtightly provided to the sputter chamber 1 via an insulator 53, and
`holds the target 2 parallel to the substrate 50. This substrate holder 5 is provided with an electric field
`establishment means 8 that establishes an electric field to extract the sputter particles from the plasma P
`formed beneath the target 2, and cause them to enter the substrate 50 (hereinafter referred to as an
`“extraction electric field”). In the present embodiment, a substrate-biasing power source 81, which
`applies a bias voltage to the substrate 50, is employed as the electric field establishment means 8. A
`direct-current power source, which applies a negative direct current voltage to the substrate 50, is used as
`the substrate-biasing power source 81 in the present embodiment.
`
`[0018] In addition, the substrate-biasing power source 81 doubles as an attraction power source for
`attracting the substrate 50 to the substrate holder 5. That is, an upper-side portion of the substrate holder
`5 is formed of a dielectric, and an attraction electrode 51 is embedded in the interior of this dielectric
`portion. The substrate-biasing power source 81 is connected to this attraction electrode 51. Specifically,
`the substrate-biasing power source 81 is designed to apply a direct current voltage of about -600V, for
`example, to the attraction electrode 51. The voltage causes dielectric polarization of the dielectric, and a
`negative potential appears on the surface of the substrate holder 5. This negative potential establishes an
`electric field perpendicular to the substrate 50, and the ionized sputter particles are efficiently extracted
`from the plasma P.
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`[0019] In addition, the substrate 50 is electrostatically attracted by the negative potential on the surface of
`the substrate holder 5. A heater 52 is provided in the interior of the substrate holder 5, and the precision
`with which the heater 52 controls temperature is enhanced by the substrate 50 being electrostatically
`attracted to the substrate holder 5. The heater 52 is structured so as to be able to control the temperature
`of the substrate 50 over a range from room temperature to about 500°C.
`
`[0020] In addition to a negative direct-current power source, a predetermined high frequency power
`source can be used as the substrate-biasing power source 81. When the substrate-biasing power source 81
`applies a high frequency voltage to the substrate holder 5, the charged particles in the plasma P are
`periodically attracted to the surface of the substrate 50. Of these particles, electrons, having a higher
`degree of mobility, are attracted to the surface of the substrate 50 in greater number than positive ions,
`causing the surface of the substrate 50 to be in the same state as if biased to a negative potential as a result.
`This high frequency power source can be one with a frequency of about 13.56 MHz and an output of
`about 600W, for example.
`
`[0021] A shield 6 is provided so as to surround the flight path of the sputter particles between the target 2
`and the substrate 50. The shield 6 is cylindrical, and is provided coaxially with the target 2 and the
`substrate 50. To indicate the measurements in more detail, the shield 6 is in the form of a cylinder having
`a wall thickness of about 1 mm, with an inner diameter of 300 mm, which is slightly smaller than the
`diameter of the target 2, and a height of about 50 mm. Additionally, the distance in the axial direction
`from the target 2 to the shield 6 is about 20 mm. The shield is made of titanium in material, and is formed
`of a nonmagnetic body. This shield 6 is held by the sputter chamber 1 via an insulator 61. However, a
`make-and-break short-circuiting body 62 that short-circuits the shield 6 with respect to the sputter
`chamber 1 is provided, so as to allow selection of whether the shield 6 is set at a grounding potential or a
`floating potential.
`
`[0022] Additionally, in the device shown in Fig. 1, a magnetic field establishment means 7, which
`establishes a magnetic field to facilitate the effects of ionizing sputtering, is provided. In the present
`embodiment, the magnetic field establishment means 7 consists of a magnet 71 provided to the lower side
`of the substrate holder 5. The magnet 71 is an annular permanent magnet provided coaxially with the
`substrate holder 5, and different magnet poles appear on the top and bottom faces thereof. Thus, lines of
`magnetic force 72 as shown in Fig. 1 are established. The magnetic 71 can consist of an electromagnet.
`
`[0023] Next, the operation of the sputtering device of the present embodiment is described using Fig. 1.
`The substrate 50 is conveyed into the sputter chamber 1 through a gate valve (not shown in drawings) and
`placed on the substrate holder 5. The inside of the sputter chamber 1 is evacuated in advance so as to be
`10-9 Torr, and after placement of the substrate 50, the gas introduction means 4 is actuated and a process
`gas such as argon and the like is introduced at a predetermined flow rate. The evacuation speed adjuster
`of the evacuation system 11 is controlled so as to maintain the inside of the sputter chamber 1 at a
`predetermined pressure level. The pressure here is about 20 mTorr to 100 mTorr, which is higher than the
`pressure in ordinary sputtering (a few mTorr). Under this pressure, the sputtering power source 3 is
`actuated, and the substrate-biasing power source 81 is simultaneously actuated.
`
`[0024] A predetermined high frequency voltage is applied to the target 2 by the sputtering power source 3,
`which generates a magnetron sputter discharge; the magnetron sputter discharge forms a plasma P
`beneath the target 2. Additionally, a substrate-biasing voltage is applied to the substrate 50 by the
`substrate-biasing power source 81, and as a result, an extraction electric field is established between the
`plasma P and the substrate 50. The sputter particles released from the target 2 by sputtering arrive at the
`substrate 50 and deposit onto the substrate 50 a thin film made of the material of the target 2. When the
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`thin film reaches a predetermined thickness, actuation of each of the sputtering power source 3, the
`substrate-biasing power source 81, and the gas introduction system 4 shuts down, and after evacuating the
`inside of the sputter chamber 1 again, the substrate 50 is removed from the sputter chamber 1.
`
`[0025] When a barrier film is to be produced, a titanium target 2 is used, and argon is at first introduced
`as the process gas to form a titanium thin film. Then, nitrogen gas is introduced thereafter as the process
`gas, and a reaction between the titanium and the nitrogen is supplementarily utilized to produce a titanium
`nitride thin film. Thereby, a barrier film is obtained in which a titanium nitride thin film is laminated over
`a titanium thin film.
`
`[0026] In the operation set forth above, the pressure is high at 20 mTorr to 100 mTorr, and a large amount
`of electric power of 10 kW is applied to the target 2; thus, the plasma P has high density and energy levels.
`Therefore, the sputter particles ionize in this plasma P with sufficient efficiency and become ionized
`sputter particles. These ionized sputter particles are efficiently extracted from the plasma P by the
`extraction electric field, and efficiently enter the substrate 50. These ionized sputter particles efficiently
`arrive at the interior of a hole formed in the surface of the substrate 50, and contribute to forming a film
`on the inside of the hole with good bottom coverage. This point is described in further detail.
`
`[0027] Fig. 2 is a simplified cross-section describing an action of the ionized sputter particles. As
`illustrated in Fig. 2(a), when depositing a thin film 510 inside a fine hole 500 formed in the surface of the
`substrate 50, there is a tendency for the thin film 510 to accumulate and create a bulge around an edge
`503 of the opening of the hole 500. The thin film 510 that forms the bulging portion is called an
`“overhang,” and when the overhang is formed, the opening of the hole 500 becomes smaller, which
`increases the apparent aspect ratio. Thus, the amount of sputter atoms that reaches the inside of the hole
`500 decreases, and the bottom coverage decreases.
`
`[0028] As shown in Fig. 2(b), when ionized sputter particles 20 reach the substrate 50, these ionized
`sputter particles 20 re-sputter and break up the thin film 510 forming the overhang portion, and act so as
`to knock it into the hole 500. This prevents the opening of the hole 500 from narrowing and facilitates the
`deposition of film on the bottom surface of the hole 500, and the bottom coverage is increased. This kind
`of re-sputtering of the overhang can be caused not only by the ionized sputter particles 20 but by ions of
`the process gas introduced to generate sputter discharge.
`
`[0029] In addition, with the device of the present embodiment, the electric field establishment means 8
`establishes an extraction electric field perpendicular to the substrate 50 in which the potential decreases
`toward the substrate 50. Thus, the ionized sputter particles 20 set forth above are guided by this
`extraction electric field and made to perpendicularly enter the substrate 50 more easily. This makes it
`easier for the ionized sputter particles 20 to arrive at the bottom surface of the deep hole 500, and this
`point also contributes to increasing the bottom coverage.
`
`[0030] Further, as seen in Fig. 1, the lines of magnetic force established by the magnet 71 employed as
`the magnetic field establishment means 7 act to efficiently guide the ionized sputter particles 20 to the
`substrate 50. This point also contributes to the formation of film with a high degree of bottom coverage.
`The lines of magnetic force 72 also have an effect of preventing diffusion of the plasma P toward the side
`of the substrate holder 5, which has an effect of increasing plasma density and further facilitating
`ionization.
`
`[0031]
`[Example] Sputtering can be performed under the following conditions as a practical example (hereinafter
`referred to as the first practical example) of producing a titanium thin film for use as a barrier film, and
`which pertains to the embodiment set forth above.
`
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`Sputtering power source 3: 13.56 MHz, 8kW output
`Material of target 2: titanium
`Type of process gas: argon
`Flow rate of process gas: 120 cc/min
`Pressure during film formation: 60 mTorr
`Substrate-biasing voltage: -600V
`Temperature of substrate holder 5 during film formation: 300°C
`Film formation speed: 500 angstroms/min
`
`[0032] In addition, sputtering can be performed under the following conditions as a practical example
`(hereinafter referred to as the second practical example) of producing a titanium nitride thin film for use
`as a barrier film.
`Sputtering power source 3: 13.56 MHz, 8kW output
`Material of target 2: titanium
`Type of process gas: mixed gas of argon and nitrogen
` Flow rate of process gas: argon 25 cc/min, nitrogen 75 cc/min
`Pressure during film formation: 45 mTorr
`Substrate-biasing voltage: -600V
`Temperature of substrate holder 5 during film formation: 200°C
`Film formation speed: 200 angstroms/min
`
`[0033] Fig. 3 is a graph showing the results of forming a film under the conditions of the first practical
`example set forth above, and is a graph showing the relationship of bottom coverage to the aspect ratio of
`the hole. For comparison, data for a low-pressure, long-distance sputtering device is also shown as a
`conventional sputtering device. The data for this low-pressure, long-distance sputtering were obtained
`under conditions comprising a pressure of 0.5 mTorr and a distance of 340 mm between the target 2 and
`the substrate 50.
`
`[0034] As shown in Fig. 3, with low-pressure, long-distance sputtering, a bottom ratio of less than 20% is
`obtained for a hole with an aspect ratio of 4. On the other hand, with ionizing sputtering of the practical
`example, a bottom coverage of about 40% is obtained, and it can be understood that a much higher
`bottom coverage is obtained. Even for a hole with an aspect ratio over 4, a bottom coverage of about 35%
`is obtained at the central portion of the substrate 50, and it can be understood that [ionizing sputtering] is
`also effective for forming films in holes having a high aspect ratio. Furthermore, compared to low-
`pressure, long-distance sputtering, there is very little variance in the bottom coverage between the central
`portion and the peripheral portion of the substrate, and it can be understood that the uniformity of bottom
`coverage within the surfaces is also significantly improved.
`
`[0035] The amount of electric power supplied to the target 2 is an important parameter in such ionization
`of sputter particles in the plasma P formed by sputter discharge. Supplying a large amount of electric
`power to the target 2 is effective in facilitating ionization in the plasma P. How large the amount should
`be for sufficient ionization varies depending upon the size of the space in which the plasma P is formed.
`By substituting the size of the space in which the plasma P is formed with the size of the target 2, it can be
`seen that generally, the above-mentioned ionization is sufficiently performed when the electric power area
`density obtained by dividing the amount of electric power supplied by the area of the sputtered face of the
`target 2 is 5W/cm2 or higher.
`
`[0036] In addition, the pressure during film formation is also an important parameter for efficient
`ionization of ionized sputter particles. This is because, even if the electric power is increased, if the
`amount of gas molecules which become the source of the plasma does not increase, then the thing
`receiving the energy doe