5,968,327
`[11] Patent Number:
`[19]
`Ulllted States Patent
`
`Kobayashi et al.
`[45 J Date of Patent:
`Oct. 19, 1999
`
`U3005968327A
`
`[54]
`
`[75]
`
`IONIZING SPUTTER DEVICE USING A COIL
`SHIELD
`
`Inventors: Masahiko Kobayashi; Nobuyuki
`Takahashi, both of Kanagawa-ken,
`Japan
`
`[73] Assignee: Anelva Corporation, Fuchu, Japan
`
`[21] Appl. No.: 09/022,623
`
`[22]
`
`[30]
`
`Filed:
`
`Feb. 12, 1998
`
`Foreign Application Priority Data
`
`Apr. 14, 1997
`
`[JP]
`
`Japan .................................... 9111902
`
`Int. Cl.6 ..................................................... C23C 14/34
`[51]
`[52] U.S. Cl.
`................................ 204/298.11; 204/298.06;
`204/298.08
`[58] Field of Search .......................... 204/29806, 298.11,
`204/29807, 298.08, 298.15
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`5,178,739
`5,397,962
`5,431,799
`5,545,978
`5,707,398
`5,763,851
`5,800,619
`
`.
`1/1993 Barnes et al.
`3/1995 Moslehi
`............................. 315/111.51
`/1995 Mosely et al.
`..................... 204/298.06
`/1996 Pontius .
`1/1998 Ngan .................................. 204/192.12
`7/1996 Forster et a1.
`..................... 219/121.43
`6/1996 Holland et al.
`....................... 118/723 I
`
`204/298.11
`4/1997 Lantsman et al.
`5,800,688
`5/1999 Young et a1.
`...................... 315/111.41
`5,903,106
`FOREIGN PATENT DOCUMENTS
`
`WO92/07969
`
`5/1992 WIPO .
`
`OTHER PUBLICATIONS
`
`Magnetron Sputter Deposition for Interconnect Applica-
`tions; S.M. Rossnagel; Conference Proceedings ULSI XI;
`1996 Materials Research Society; pp. 227—232.
`Ionized Magnetron Sputtering for Lining and Filling
`Trenches and Vias; S.M. Rossnagel; Semiconductor Inter—
`national; Feb. 1996; pp. 99—102.
`
`Primary Examiner—Nam Nguyen
`Assistant Examiner—Julian A. Mercado
`Attorney, Agent, or Firm—Burns, Doane, Swecker &
`Mathis, LLP
`
`ABSTRACT
`[57]
`A coil shield 64 that blocks the arrival at a substrate 50 of
`the material released by sputtering is provided to a high
`frequency coil 61 provided such that it surrounds the ion-
`ization space between the target 2 and the substrate holder
`5. The coil shield 64 is made of metal, and is grounded,
`which prevents plasma formation in unnecessary places. The
`coil shield 64 is hollow, gas blowing holes are uniformly
`formed over the inner surface facing the ionization space,
`and the gas is flown toward the ionization space.
`
`16 Claims, 4 Drawing Sheets
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`5,968,327
`
`1
`IONIZING SPUTTER DEVICE USING A COIL
`SHIELD
`
`This application claims priority under 35 U.S.C. §§ll9
`and/or 365 to Appln. No. 9-111902 filed in Japan on Apr. 14,
`1997; the entire content of which is hereby incorporated by
`reference.
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`The present invention relates to a sputtering device used
`in the fabrication of various types of semiconductor devices.
`More particularly, it relates to an ionizing sputtcring device
`having a function that ionizes the sputter particles.
`2. Description of Related Art
`With semiconductor devices, such as various types of
`memory and logic, a sputtering process is used in the
`formation of various wiring films, and in the production of
`barrier films that prevent
`the interdiffusion of different
`layers. A sputtering process makes use of a sputtering
`device, and there has recently been a great need for such
`sputtering devices to allow the inner surfaces of holes
`formed in a substrate to be coated with a good degree of
`coverage.
`
`Recently, there has been a need in the case of barrier films
`for an increase in the bottom coverage, which is the ratio of
`the film deposition on the bottom of a hole to that on the
`peripheral surfaces of the hole. With today’s higher degrees
`of integration, holes such as contact holes have been steadily
`increasing in aspect ratio, which is the ratio of the hole depth
`to the size of the hole opening. A film cannot be deposited
`with good bottom coverage by a conventional sputtering
`process. A decrease in the bottom coverage can lead to a
`thinner barrier film at the bottom of the hole and to critical
`flaws in the device characteristics, such as junction leakage.
`Collimation sputtering, and low-pressure, long-distance
`sputtering, have been developed up to now as sputtering
`processes that increase the bottom coverage. These pro—
`cesses will not be described in detail here, but they all
`attempt to direct many neutral sputter particles perpendicu-
`larly at the substrate.
`A problem with collimation sputtering, however, is that
`sputter particles accumulate on the collimator portion, and
`the resulting loss of material decreases the film deposition
`rate. Aproblem with low-pressure, long-distance sputtering
`is that since the pressure is lowered and the distance between
`the target and the substrate is lengthened, there is a funda—
`mental decrease in the film deposition rate. Because of these
`problems,
`the first generation is about as far as these
`processes are expected to go, or up to 64 megabits with
`collimation sputtering and 256 megabits with low-pressure,
`long-distance sputtering.
`There is a need for a practical process that can be utilized
`in the production of devices over 256 megabits. In response
`to this need, there has been speculation that ionizing sput-
`tering might be a useful process. Ionizing sputtering is a
`process in which the sputter particles released from the
`target are ionized, and the sputter particles are made to arrive
`inside the hole more efficiently through the action of these
`ions. Ionizing sputtering yields a higher bottom coverage
`than collimation sputtering or low-pressure, long-distance
`sputtering.
`Typically, ionizing sputtering involves forming a plasma
`along the flight path of the sputter particles between the
`substrate and the target, and ionizing the sputter particles as
`
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`they pass through the plasma. An inductive coupling type of
`plasma is usually formed as this plasma. In specific terms, a
`high frequency coil is provided such that it surrounds the
`space where the ionization is performed along the flight
`path, hereinafter referred to as the ionization space. Constant
`high frequency waves are supplied to this high frequency
`coil to form a plasma on the inside of the high frequency
`coil. High frequency current flows into the plasma, and the
`plasma and the high frequency coil are inductively coupled.
`It
`is because of this action that this plasma is called an
`inductive coupling type of plasma.
`SUMMARY AND OBJECTS
`
`However, conventional ionizing sputtering is plagued by
`the following problems:
`First, the high frequency coil is usually installed inside the
`sputter chamber in order to set up a sufficiently strong high
`frequency electric field. The high frequency coil is sputtered
`by the plasma, and the sputtered material from the high
`frequency coil reaches the substrate, as a result of which the
`substrate is fouled.
`
`Second, since the gas diifuses into the sputter chamber,
`there are cases when the plasma is formed on the outside of
`the high frequency coil, as well. The plasma formed at these
`places is not only not needed for the ionization, but can
`actually damage the members located in these places.
`Third, when a plasma is formed,
`the structure of the
`optimal gas introduction for sputter discharge differs from
`that of the optimal gas introduction for forming the ionizing
`plasma. The gas for forming the plasma cannot be supplied
`efiiciently, so plasma formation efliciency suifers.
`The present invention was conceived in an effort to solve
`these problems, and an object
`thereof is to provide a
`practical ionizing sputtering device that is effective in the
`production of second generation devices, and that solves the
`above problems encountered with ionizing sputtering.
`These objects may be accomplished with an ionizing
`sputtering device that includes a sputter chambcr equipped
`with a vacuum pump system; a target provided inside the
`sputter chamber; a sputtering electrode for sputtering the
`target; gas introduction means for introducing a gas into the
`sputter chamber; ionization means for ionizing sputter par-
`ticles released from the target by sputtering, the ionization
`means includes a high frequency coil provided inside the
`sputter chamber so as to surround a space between the target
`and the substrate holder, and a high frequency power source
`that forms a high frequency inductive coupling type of
`plasma in the space by supplying high frequency waves to
`the high frequency coil; a substrate holder for holding a
`substrate in a position where the sputter particles land; and
`a coil shield provided on the high frequency coil, the coil
`shield arranged so as to block the arrival at the substrate of
`sputter particles composed of the material of the high
`frequency coil that are sputtered and released by said high
`frequency coil.
`These objects may also be accomplished with an ionizing
`sputtering device that includes a sputter chamber equipped
`with an exhaust system; a target provided inside the sputter
`chamber; a sputtering electrode for sputtering the target; gas
`introduction means for introducing a gas into the sputter
`chamber;
`ionization means for ionizing sputter particles
`released from the target by sputtering, the ionization means
`includes a high frequency coil provided inside the sputtcr
`chamber so as to surround a space between the target and the
`substrate holder, and a high frequency power source that
`forms a high frequency inductive coupling type of plasma in
`
`

`

`5,968,327
`
`3
`the space by supplying high frequency waves to the high
`frequency coil, and the high frequency coil is formed from
`a same material as the target, which is a material of a thin
`film to be produced on the substrate; a substrate holder for
`holding a substrate in a position where the sputter particles
`land; and an auxiliary shield is provided to an outside of the
`high frequency coil, and the auxiliary shield is formed from
`a metal member and is electrically grounded, and encloses
`the plasma on the inside of the high frequency coil.
`These objects may also be accomplished with an ionizing
`sputtering device that includes a sputter chamber equipped
`with an exhaust system; a target provided inside the sputter
`chamber; a sputtering electrode for sputtering the target; gas
`introduction means for introducing a gas into the sputter
`chamber; ionization means for ionizing the sputter particles
`released from the target by sputtering, the ionization means
`includes a hollow high frequency coil provided inside the
`sputter chamber so as to surround a space between the target
`and the substrate holder, and a high frequency power source
`that forms a high frequency inductive coupling type of '
`plasma in the space by supplying high frequency waves to
`this high frequency coil; a substrate holder for holding a
`substrate in a position where the sputter particles land; the
`hollow high frequency coil
`includes gas blowing holes
`formed uniformly over an inner surface thereof so as to face ’
`the space so that a specific gas can be introduced into the
`space through the gas blowing holes.
`
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`BRIEF DESCRIPTION OF TIIE DRAWINGS
`
`FIG. 1 is a simplified front view of the structure of the
`sputtering device in a first embodiment of the present
`invention;
`FIG. 2 is a diagram of the specific dimensions of the coil
`shield 64 used in the device shown in FIG. 1;
`FIG. 3 is a simplified cross section of the state of the
`electric field inside the coil shield 64 in FIG. 1;
`FIG. 4 is a simplified cross section of a favorable structure
`of the coil shield 64 in FIG. 1;
`FIG. 5 is a simplified front View of the main structure of
`the ionizing sputtering device pertaining to a second
`embodiment of the present invention; and
`FIG. 6 is a simplified front View of the main structure of
`the ionizing sputtering device pertaining to the third embodi-
`ment of the present invention.
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`Preferred embodiments of the present invention will now
`be described.
`
`FIG. 1 is a simplified front View of the structure of a
`sputtering device in a first embodiment of the present
`invention.
`
`As shown in FIG. 1, the sputtering device in this embodi-
`ment has a sputter chamber 1 equipped with a vacuum pump
`system 11. The sputter chamber 1 has a target 2 provided on
`its inside, a sputtering electrode 3 that sputters this target 2,
`and a gas introduction means 4 for introducing a sputter gas
`into the sputter chamber 1. In order for the sputter particles
`released from the target 2 by sputtering to be ionized, the
`sputter chamber 1 further comprises an ionization means 6,
`and an electric field establishment means 7 for setting 11p an
`electric field in the direction perpendicular to a substrate 50
`in order to pull the ionized sputter particles into the substrate
`50. The ionized sputter particles are directed at the substrate
`50, which is held on a substrate holder 5.
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`The sputter chamber 1 is an airtight vessel equipped with
`a gate valve, not shown. This sputter chamber 1 is made of
`a metal such as stainless steel, and is electrically grounded.
`The vacuum pump system 11 is a multi-stage vacuum
`pump furnished with a turbo molecular pump or a diffusion
`pump. The vacuum pump system 11 is capable of pumping
`out the inside of the sputter chamber 1 down to about 10’8
`to 10'9 Torr. The vacuum pump system 11 is equipped with
`a pumping speed adjuster, not shown, such as a variable
`orifice, which allows the pumping speed to be adjusted.
`The target 2 is in the form of a disk that is 6 mm thick and
`about 300 mm in diameter. The target 2 is attached to the
`sputtering electrode 3 via a target holder, not shown.
`The sputtering electrode 3 is a magnetron cathode
`equipped with a magnet assembly. The magnet assembly
`consists of a center magnet 31, a peripheral magnet 32 that
`surrounds the center magnet 31, and a disk-shaped yoke 33
`that ties the center magnet 31 to the peripheral magnet 32.
`The magnets are both permanent magnets, but they can
`instead comprise electromagnets.
`The sputtering electrode 3 is attached to the sputter
`chamber 1 in an insulated state, and a sputtering power
`source 35 is connected. The sputtering power source 35
`applies the desired negative voltage or a high frequency
`voltage to the sputtering electrode 3. When titanium is being
`sputtered, a negative, direct current voltage of about 600 V
`is applied.
`The gas introduction means 4 primarily consists of a gas
`cylinder 41 filled with argon or another sputtering discharge
`gas, and a gas distributor 46 connected to the distal end of
`an in-chamber tube 45. The gas cylinder 41 and the sputter
`chamber 1 are linked by a tube 42. A valve 43 and flux
`adjuster 44 are attached to the tube 42. The in-chamber tube
`45 is linked to the distal end of the tube 42.
`
`An annular pipe that has gas blowing holes formed in its
`central side surface is employed for the gas distributor 46.
`The gas distributor 46 uniformly introduces gas into the
`space between the target 2 and the substrate holder 5.
`In this embodiment,
`the ionization means 6 forms an
`inductive coupling type of high frequency plasma along the
`flight path of the titanium from the target 2 to the substrate
`50. The ionization means 6 primarily consists of a high
`frequency coil 61 provided such that it surrounds the ion-
`ization space between the target 2 and the substrate holder
`5, and a high frequency power source 62 connected to the
`high frequency coil 61 via a matching box 63.
`The high frequency coil 61 comprises a metal rod about
`10 mm thick that has been molded into a roughly spiral
`shape, and the radial distance from the center axis of the
`sputter chamber 1 to the high frequency coil 61 is about 150
`to 250 mm. Since a coil shield 64, discussed below,
`is
`provided to the high frequency coil 61 in this embodiment,
`there are no particular restrictions on the material of the high
`frequency coil 61. A material that efficiently excites high
`frequency waves, such as titanium, is used for the high
`frequency coil 61.
`The high frequency power source 62 has a frequency of
`13.56 MHz and an output of about 5 kW. High frequency
`power is supplied to the high frequency coil 61 via a
`matching box 63. A high frequency electric field is set up in
`the ionization space by the high frequency coil 61. The gas
`introduced by the gas introduction means 4 is converted into
`a plasma by this high frequency electric field, forming a
`plasma P. A high frequency current is allowed to flow into
`the plasma P, and the plasma P and the high frequency coil
`61 are inductively coupled.
`
`

`

`5,968,327
`
`5
`As the sputter particles released from the target 2 pass
`through the plasma P, they strike the electrons in the plasma
`P and are ionized. The ionized sputter particles are acceler—
`ated by the electric field, as discussed below, and thereby
`arrive at the substrate 50.
`
`The substrate holder 5 holds the substrate 50 parallel to
`the target 2. The substrate holder 5 may be provided with a
`heating mechanism, not shown, for heating the substrate 50
`during film deposition to deposit a film more efficiently. The
`substrate holder 5 may also be provided with an electrostatic
`chucking mechanism, not shown,
`for electrostatically
`attracting the substrate 50.
`In this embodiment, the electric field establishment means
`7 imparts a negative bias voltage to the substrate 50 by
`applying a constant high frequency voltage to the substrate
`holder 5. The electric field establishment means 7 comprises
`a substrate-biasing high frequency power source 71 that is
`connected to the substrate holder 5 via a blocking capacitor
`72.
`
`The substrate-biasing high frequency power source 71 is
`one with a frequency of 13.56 MHz and an output of about
`300 W. When high frequency voltage is applied to the
`substrate 50 by the substrate-biasing high frequency power
`source 71, the charged particles within the plasma P are
`periodically attracted to the surface of the substrate 50.
`Electrons, with their higher degree of mobility, are attracted
`to the surface of the substrate 50 in greater number than
`positive ions, as a result of which the surface of the substrate
`50 is in the same state as if it were biased to a negative
`potential. In specific terms, in the case of the electric field
`establishment means 71 used in this example, a bias voltage
`of about —100 V can be imparted on average to the substrate
`50.
`The state in which the above-mentioned substrate bias
`voltage has been imparted is the same as that in a cathode
`sheath region when a plasma is formed by direct current
`diode discharge, and is a state in which an electric field
`having a potential gradient that drops toward the substrate
`50, hereinafter referred to as an extraction-use electric field,
`is set up between the plasma and the substrate 50. This
`extraction-use electric field causes the ionized sputter
`particles, which may be positive ions of titanium,
`to be
`extracted from the plasma and arrive at the substrate 50 more
`efficiently.
`When the target 2 is a metal, the above-mentioned sub-
`strate holder 5 is made from the same metal material as the
`target 2, and when the target 2 is a dielectric, the substrate
`holder 5 is made from a metal that is heat resistant, such as
`stainless steel. In any case, the substrate holder 5 is made of
`a metal, and therefore in principle no direct current electric
`field exists within the placement plane of the substrate
`holder 5. The above-mentioned extraction-use electric field
`
`is only an electric field that faces perpendicular to the
`substrate 50, and acts to accelerate the ionized sputter
`particles perpendicularly to the substrate 50. This allows the
`ionized sputter particles to make it all the way to the bottom
`of the hole formed in the substrate 50 more efficiently.
`The structure of the coil shield 64, will now be described.
`This embodiment is provided with a coil shield 64 that
`blocks the arrival at the substrate 50 of the material of the
`
`high frequency coil 61 that has been sputtered and released
`from the high frequency coil 61.
`As shown in FIG. 1, the coil shield 64 is formed so as to
`cover the periphery of the high frequency coil 61 except for
`a portion of the high frequency coil 61 on the inside. The coil
`shield 64 has a cylindrical cross section that is concentric
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`with the cross section of the high frequency coil 61. The coil
`shield 64 extends in the same direction as the high frequency
`coil 61, and is shaped so as to cover the high frequency coil
`61 over the entire length of the high frequency coil 61.
`An opening 640 is formed on the inner side of the coil
`shield 64, and this opening 640 allows high frequency waves
`to pass through, hereinafter this opening will be referred to
`as the high frequency wave passage opening. The high
`frequency wave passage opening 640 is formed over the
`entire length of the high frequency coil 61, so it is shaped as
`a spiral slit.
`A specific example of the dimensions of the coil shield 64
`will be given with reference to FIG. 2. FIG. 2 is a diagram
`of the specific dimensions of the coil shield 64 used in the
`device shown in FIG. 1.
`
`When the thickness d1 of the high frequency coil 61 is
`about 10 mm, then the distance d2 between the coil shield
`64 and the surface of the high frequency coil 61 is about 3
`to 5 mm, and the width d3 of the high frequency wave
`passage opening 640 is about 10 mm. The size of the high
`frequency wave passage opening 640 is referred to as the
`allowance angle from the center of the thickness of the high
`frequency coil 61, and in this embodiment is about 70°.
`The selection of the width d3 of this high frequency wave
`passage opening 640 is an important technological matter
`both in terms of the efficiency of plasma formation and of
`the diffusion of the plasma into the coil shield 64. In the
`sense of raising plasma formation efficiency by radiating
`more high frequency waves into the ionization space, it is
`preferable for the width d3 of the high frequency wave
`passage opening 640 to be large. If d3 is increased, however,
`then the problem of diffusion of the plasma into the coil
`shield 64 becomes more pronounced.
`As d3 increases, the plasma diffuses into the coil shield 64
`and produces a high frequency discharge inside the coil
`shield 64. This is just the same as in the case of a high
`frequency hollow discharge, but when discharge occurs
`within the coil shield 64, a great deal of high frequency wave
`energy is used up in said discharge. This means that not
`enough energy is supplied to the ionization space on the
`inner side of the high frequency coil 61, and as a result, the
`plasma formation efficiency decreases. The sputtering of the
`high frequency coil 61 also becomes more violent, resulting
`in the problem of damage to the high frequency coil 61.
`Therefore, d3 should be made as large as possible to the
`extent that the plasma does not diffuse into the coil shield 64.
`This value will vary with the pressure and plasma density, so
`these parameters should also be taken into account.
`This coil shield 64 is made of a metal such as stainless
`steel or aluminum, and is electrically grounded. The
`surfaces, both inner and outer sides, of the coil shield 64 are
`subjected to a surface treatment for heat resistance and
`plasma resistance, such as an alumite treatment.
`Irregularities that prevent the accumulated thin film from
`falling off are formed on the inner surface of the coil shield
`64, that is, the surface facing the high frequency coil 61. The
`surface of the high frequency coil 61 is sputtered by the
`plasma, and the sputtered material of the high frequency coil
`61 builds up on the surface of the coil shield 64. Once this
`accumulated film has reached a certain amount, it falls off by
`its own weight and becomes dust particles. These dust
`particles float
`inside the splitter chamber, occasionally
`adhering to the substrate, and are a cause of substrate
`fouling. Irregularities are formed to enhance film adhesion
`so that the accumulated film on the surface of the coil shield
`64 will not fall off so easily.
`
`

`

`5,968,327
`
`7
`The operation of the ionizing sputtering device of this
`embodiment will now be described through reference to
`FIG. 1. The substrate 50 is conveyed through a gate valve,
`not shown, and into the sputter chamber 1, where it is placed
`on the substrate holder 5. The inside of the sputter chamber
`1 has already been pumped down to about 10'8 to 10'9 Torr.
`After the substrate 50 is in place, the gas introduction means
`4 is actuated, and a process gas, such as argon, is introduced
`at a constant flux. This process gas is used for sputter
`discharge, and is also used to form a plasma in the ionization
`space.
`The pumping speed adjuster of the vacuum pump system
`11 is controlled so as to maintain the inside of the sputter
`chamber 1 at about 30 to 40 mTorr, and the sputtering
`electrode 3 is actuated in this state. A constant voltage is
`imparted to the sputtering electrode 3 by the sputtering
`power source 35, which produces a magnetron sputter
`discharge.
`At the same time, the ionization means 6 is also actuated
`by applying a high frequency voltage to the high frequency
`coil 61 by the high frequency power source 62, and a high
`frequency electric field is set up in the ionization space. The
`sputter discharge gas also diffuses into the ionization space,
`and the plasma P is formed when the sputter discharge gas
`undergoes electrolytic dissociation. The electric field estab-
`lishment means 7 is also actuated at the same time by
`applying a specific bias voltage to the substrate 50 by the
`substrate-biasing high frequency power source 71, and an
`extraction-use electric field is set up between the plasma 1’
`and the substrate 50.
`
`The target 2 is sputtered by the sputter discharge, and the
`sputtered titanium flies toward the substrate 50. In the course
`of this flight, the sputter particles are ionized as they pass
`through the plasma P in the ionization space. The ionized
`titanium is efficiently extracted from the plasma and directed
`at
`the substrate 50 by the extracting electric field. The
`titanium that lands on the substrate 50 reaches the bottom
`and side surfaces of the hole, builds up a film, and efliciently
`covers the inside of the hole.
`
`When a film of the desired thickness has been produced,
`the electric field establishment means 7, ionization means 6,
`sputtering electrode 3, and gas introduction means 4 are
`turned off, and the substrate 50 is conveyed out of the sputter
`chamber 1.
`
`In the above operation, the surface of the high frequency
`coil 61 is sputtered primarily by the ions of the process gas
`flying through the plasma P, and, in rare instances, by ions
`of the sputter particles. However, the sputter particles com-
`posed of the material of the high frequency coil 61 released
`by this sputtering are almost all blocked by the coil shield
`64, and so they do not reach the substrate 50 or the target 2.
`The problem of fouling of the substrate 50 by the sputtered
`material of the high frequency coil 61 is virtually nonexist-
`ent in this embodiment. If any sputter particles composed of
`the material of the high frequency coil 61 adhere to the target
`2, they may be re-sputtered and reach the substrate 50, so
`blocking is important not only for the substrate 50, but also
`for the target 2.
`Even when the grounded coil shield 64 is provided on the
`outer side of the high frequency coil 61, high frequency
`waves of sufficient energy can be stored on the inner side of
`the high frequency coil 61.
`FIG. 3 is a simplified cross section of the state of the
`electric field inside the coil shield 64 in FIG. 1. The coil
`shield 64 has a circular cross section that is concentric with
`the cross section of the high frequency coil 61. The coil
`
`10
`
`15
`
`’
`
`40
`
`45
`
`60
`
`65
`
`8
`shield 64 itself is grounded. Electric power lines 610 car-
`rying the high frequency voltage supplied to the high
`frequency coil 61 as shown in FIG. 3 fan out radially from
`the center point of the thickness of the high frequency coil
`61 as shown in FIG. 3. The equipotential surface 611 that
`radiates from the high frequency coil 61 spreads out from the
`center in a concentric, circular form. The high frequency
`electric field is induced without disturbance within the coil
`shield 64, and high frequency waves radiate stably from the
`high frequency wave passage opening 640. As a result, a
`stable plasma can be formed in the ionization space.
`FIG. 4 is a simplified cross section of a favorable structure
`of the coil shield 64 in FIG. 1. As discussed above, the coil
`shield 64 covers the outside of the high frequency coil 61,
`and blocks the material of the high frequency coil 61 that
`was released by sputtering from reaching the substrate 50.
`For the blocking of the sputter particles of the high fre-
`quency coil 61 from the substrate 50 to be most effective, it
`is preferable for no point on the substrate 50 and no point on
`the sputtered surface of the target 2 to be visible from the
`coil shield 64 through the high frequency wave passage
`opening 640.
`This will be described in specific terms through reference
`to FIG. 4. As one example, a high frequency wave passage
`opening 640 located on the upper right side in the figure will
`be described. As shown in FIG. 4, when a tangent 641 that
`passes by the lower edge of this high frequency wave
`passage opening 640 and is in contact with the upper surface
`of the high frequency coil 61, hereinafter referred to as the
`first tangent, passes to the outside of the left edge of the
`substrate 50, no point on the substrate 50 can be seen
`through this high frequency wave passage opening 640.
`Here, the substrate 50 is assumed to be circular.
`When a tangent 642 that passes by the upper edge of the
`high frequency wave passage opening 640 and is in contact
`with the lower surface of the high frequency coil 61,
`hereinafter referred to as the second tangent, passes to the
`outside of the left edge of the sputtered surface of the target
`2, no point on the sputtered surface of the target 2 can be
`seen through this high frequency wave passage opening 640.
`The “sputtered surface of the target 2” refers to the surface
`region of the target 2 sputtered exclusively by the sputtering
`electrode 3, excluding the surface region fixed to the target
`holder.
`
`The same applies to the high frequency wave passage
`opening 640 positioned on the left side in FIG. 4. When the
`first tangent 641 passes to the outside of the right edge of the
`substrate 50, and the second tangent 642 passes to the
`outside of the right edge of the sputtered surface of the target
`2, no point on the substrate 50 and no point on the sputtered
`surface of the target 2 can be seen through this high
`frequency wave passage opening 640.
`The geometric arrangement of the high frequency wave
`passage opening 640 described above allows the most
`favorable effect to be obtained, namely, the blockage of the
`sputter particles from the high frequency coil 61 to the
`substrate 50. In terms of the passage efficiency of the high
`frequency waves, it is better for the high frequency wave
`passage opening 640 to be as large as possible, so an
`arrangement
`is sometimes employed in which the first
`tangent 641 is in contact with the edge of the substrate 50,
`and the second tangent 642 is in contact with the edge of the
`sputtered surface of the target 2.
`FIG. 5 is a simplified front view of the main structure of
`the ionizing sputtering device pertaining to the second
`embodiment of the present
`invention.
`In this second
`
`

`

`5,968,327
`
`9
`embodiment, the high frequency coil 61 is formed from the
`same material as the target 2, which is the material of the
`thin film to be formed on the substrate 50, and an auxiliary
`shield 65 is provided to the outside of the high frequency
`coil 61.
`
`Having the high frequency coil 61 made of the same
`material as the target 2 solves the above-mentioned problem
`of fouling of the substrate 50 by the sputtered material of the
`high frequency coil 61 through a different approach from
`that in the first embodiment. With this approach, the high
`frequency coil 61 is formed from a material that will pose no
`problems if the material of the high frequency coil 61
`adheres to the substrate 50. When a barrier film is to be
`
`the target 2 is made of titanium, and the high
`produced,
`frequency coil 61 is also made of titanium.
`Since the high frequency coil 61 m