JP5135106B2 - Film forming apparatus, film forming method, and liquid discharge apparatus - Google Patents

Description

  The present invention relates to a film forming apparatus, a film forming method, and a liquid discharge apparatus, and in particular, a film forming apparatus and a film forming method for forming a film by a vapor phase growth method using plasma, and the film forming method. The present invention relates to a liquid ejection device that uses a piezoelectric film formed by the above method.

  As a method for forming a thin film such as a piezoelectric film, a vapor phase growth method such as a sputtering method is known. In the sputtering method, plasma ions such as high-energy Ar ions generated by plasma discharge in a high vacuum are collided with a target to release the constituent elements of the target, and the released constituent elements of the target are applied to the surface of the substrate. This is a method of vapor deposition.

  When a thin film of an insulator is formed by such a sputtering method, the discharge continues immediately after the start of discharge, but as the film formation time elapses, an insulating film that should be deposited on the substrate adheres to the anode as the electrode. The area of the effective anode that plays the role of capturing electrons in the plasma is reduced, the discharge of the plasma becomes unstable, and the film quality of the formed thin film changes. There was a problem. That is, when a thin film made of an insulator or the like is formed by sputtering, there is a problem that the film quality is greatly deteriorated by several film formations.

  Due to the above problems, when a thin film such as an insulating film is formed by sputtering, the film is formed every several times, that is, before the film quality of the formed thin film deteriorates. Since the chamber (film formation container) to be performed must be opened to the atmosphere and the deposits on the anode surface must be removed, the productivity is greatly reduced.

  On the other hand, in Patent Document 1, by using an anode (counter electrode) having a large number of holes (unevenness) on the surface and an increased surface area, the sputtered dielectric material is deposited in the holes. A sputtering apparatus is disclosed in which the charge density distributed on the surface of the anode is reduced as compared with the prior art, the anode potential is kept substantially at the ground potential, and the discharge is stabilized.

  Further, in Patent Document 2, an anode (stable discharge anode) is provided outside the first deposition shield, so that stable discharge can be maintained even if a dielectric film adheres to the deposition shield. A sputtering apparatus that can be used is disclosed.

  Further, Patent Document 3 discloses that an insulating film is deposited on the anode by disposing at least one columnar body configured to be rotatable as an anode along the outer peripheral direction of the cathode. A film forming apparatus capable of supplying a thin film product having a stable film thickness and film quality by reducing the frequency of occurrence of abnormal discharge by reducing the above-mentioned is disclosed.

  Further, in Patent Document 4, by providing an outer adhesion preventing member having the same potential as the chamber around the anode, it is possible to prevent particles scattered by sputtering from adhering to the inner wall of the chamber (film formation container), A sputtering apparatus that can prevent unnecessary plasma discharge in the chamber is disclosed.

  Further, Patent Document 5 has a structure in which a plurality of conductive plates having a gap are stacked, and an anode for allowing electrons emitted from a target to enter is provided to form an insulating film on the substrate. A reactive magnetron sputtering apparatus that can be used is disclosed.

JP 2002-38263 A JP 2007-32226 A JP 2006-199989 A JP 2000-144407 A JP-A-8-232064

  However, the sputtering apparatus disclosed in Patent Document 1 can stabilize the discharge by providing a large number of holes on the surface of the anode, thereby suppressing the decrease in the surface area of the anode due to the deposition of the dielectric film. However, it is very difficult to remove (clean) the film adhered (deposited) inside the hole.

Further, in the sputtering apparatus disclosed in Patent Document 1, since the hole formed on the anode surface is at a position overlooking the target, particles generated when the target is sputtered are deposited inside the hole. There was a problem that the speed of (attachment) was relatively fast.
Furthermore, in the sputtering apparatus disclosed in Patent Document 1, if the depth of the hole is increased in order to deposit the dielectric film, the thickness of the anode inevitably increases, and the apparatus needs to be expanded. There is a problem that handling becomes extremely difficult when cleaning is performed to remove the film attached to the anode. In addition, even when the anode is formed of SUS or the like to which particles do not easily adhere, there is a problem that handling of the anode becomes extremely difficult when cleaning is performed to remove the film adhering to the anode because the weight of the anode increases. .

  Moreover, although the sputtering apparatus or the film forming apparatus disclosed in Patent Documents 2 to 4 can also realize a stable discharge, the shape of the anode or outer adhesion preventing member to which the thin film (dielectric film or insulating film) adheres is cylindrical. It is very difficult to remove the attached film by cleaning.

  Furthermore, although the reactive magnetron sputtering apparatus disclosed in Patent Document 5 can realize stable discharge, it has a configuration in which an anode is arranged around the target. Therefore, when the anode is arranged on the substrate side, film formation is performed. The gas flow may change. Also, depending on the shape and size of the plate constituting the anode, the volume of the anode is likely to be large, and handling such as cleaning to remove the attached thin film becomes difficult, and the apparatus itself becomes large, There is a problem that the apparatus cost increases.

  Therefore, an object of the present invention is to solve the problems based on the above prior art, and to realize a stable plasma discharge and to have a stable film quality by installing a simple cleaning anode without expanding the apparatus. An object of the present invention is to provide a film forming apparatus and a film forming method capable of forming a thin film, and a liquid ejecting apparatus using a piezoelectric film formed by these.

To achieve the above object, the present invention provides a vacuum vessel capable of introducing and evacuating a gas, a target holder disposed in the vacuum vessel and holding a target as a film forming material, and the vacuum vessel A substrate holder that is disposed opposite to the target holder and holds a film formation substrate on which a thin film of the film formation material is formed, and the substrate holder between the target holder and the substrate holder wherein and a anode disposed so as to surround the outer periphery of the target holder side, said anode is one stacked several sheets double annular plate member having a plurality of through holes, and the substrate holder as the plate-shaped member positioned on the side from the center of the annular small shortest distance to the inner surface, the gas was introduced into the vacuum chamber, between the target holder and the substrate holder, a voltage Only to generate plasma, in which to provide a film forming apparatus and forming a thin film of the film forming material in the film-formation on a substrate.

  In this invention, it is preferable that the said plate-shaped member is cyclic | annular.

  In the present invention, the annular shape is preferably an annular shape.

  In the present invention, the anode is formed by stacking a plurality of the plate-like members apart from each other in a direction orthogonal to the substrate holder, and the plurality of through holes of the adjacent plate-like members are It is preferable that they are arranged so as not to coincide with each other in a direction orthogonal to the substrate holder.

  In the present invention, the anode is formed by stacking a plurality of the plate-like members apart from each other in a direction orthogonal to the substrate holder, and the adjacent plate-like members are 1.0 mm from each other. It is preferable to arrange them at a distance of ˜15.0 mm.

  In the present invention, the anode is preferably grounded.

  In the present invention, the anode may be electrically insulated from the film formation substrate, and a predetermined voltage may be applied.

In order to achieve the above object, the present invention generates plasma between a target and a film formation substrate, causes ions of the plasma to collide with the target, and forms the target on the film formation substrate. A film forming method for forming a thin film using a film forming material, wherein a plurality of through holes are provided between the target and the film forming substrate so as to surround an outer periphery on the target side of the film forming substrate. overlapping several sheets double annular plate member having, and the anode shortest distance is smaller from the center of the annular extent the plate member positioned on the substrate holder side to the inner surface provided by the anode, the thin film The present invention provides a film forming method characterized by controlling a difference Vs−Vf (V) between a plasma potential Vs (V) and a floating potential Vf (V) in the plasma during the formation.

  In the present invention, the target is preferably a dielectric, a piezoelectric, an insulator, or a ferroelectric.

  Moreover, in this invention, it is preferable that the said plate-shaped member is cyclic | annular.

  In the present invention, the annular shape is preferably an annular shape.

  In the present invention, the anode is formed by stacking a plurality of the plate-like members apart from each other in a direction orthogonal to the substrate holder, and the plurality of through holes of the adjacent plate-like members are It is preferable that they are arranged so as not to coincide with each other in a direction orthogonal to the film-forming substrate.

  In the present invention, the anode is formed by stacking a plurality of the plate-like members apart from each other in a direction orthogonal to the substrate holder, and the adjacent plate-like members are 1.0 mm from each other. It is preferable to arrange them at a distance of ˜15.0 mm.

  In the present invention, the anode is preferably grounded.

  In the present invention, the anode may be electrically insulated from the film formation substrate, and a predetermined voltage may be applied.

  In order to achieve the above object, the present invention provides a piezoelectric film formed by using any of the film forming apparatuses described above or a piezoelectric film formed by any of the film forming methods described above. In order to apply a voltage to the piezoelectric film, by applying a voltage to the piezoelectric element including electrodes formed on both surfaces of the piezoelectric film, a liquid storage chamber in which liquid is stored, and the piezoelectric element, A liquid discharge apparatus having a liquid discharge port for discharging the liquid from the liquid storage chamber to the outside is provided.

According to the present invention, by providing an anode in which one or a plurality of plate-like members having a plurality of through-holes are provided, a change in the plasma state in the chamber caused by the film adhering to (depositing on) the anode Can be reduced and stabilized. As a result, the film quality of the film to be formed can be stabilized, and a stable film quality can be formed over a long period of time.
Further, according to the present invention, since the anode is composed of a plate-like member, even when a film adheres to the anode, handling is easy, and further, the deposit can be easily cleaned (removed). .
Further, in the present invention, by arranging adjacent plate-like members so that the through holes do not coincide with each other in the direction orthogonal to the film-forming substrate, adhesion of the film to the plate-like member located on the lower side of the chamber is prevented. Probability can be reduced, and film adhesion to the chamber can be reduced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a film forming apparatus, a film forming method of the present invention, a liquid ejecting apparatus including a piezoelectric element using a piezoelectric film formed using these film forming apparatus and film forming method will be described with reference to the accompanying drawings. This will be described in detail based on the preferred embodiment shown in FIG.
FIG. 1 is a schematic configuration diagram conceptually showing an embodiment of a film forming apparatus for carrying out the film forming method of the present invention, and FIG. 2 is a plate-like member constituting the anode of the film forming apparatus shown in FIG. 2A is a top view of the anode plate-like member viewed from the ceiling side of the vacuum apparatus, and FIG. 2B is a cross-sectional perspective view of the anode plate-like member. .
In the following, a film forming apparatus for forming a piezoelectric film as a thin film and manufacturing a piezoelectric element as a thin film device using the thin film will be described as a representative example. However, the present invention is not limited to this. .

The film forming apparatus of the present invention forms a thin film such as an insulating film, a dielectric film, and a ferroelectric film, in particular, a piezoelectric film on a substrate by a vapor phase growth method (sputtering) using plasma. A film forming apparatus for manufacturing a thin film device such as an element.
As shown in FIG. 1, a film forming apparatus 10 according to the present invention includes a vacuum vessel 12 having a gas introduction pipe 12a and a gas discharge pipe 12b, and a sputtering target material TG disposed on the ceiling of the vacuum vessel 12. A target holder 14 that serves as a cathode and generates plasma, a high-frequency power source 16 that is connected to the target holder 14 and applies a high frequency to the target holder 14, and the target holder 14 in the vacuum vessel 12 Between the target holder 14 and the mounting table 18, the mounting table 18 is arranged between the mounting table (substrate holder) 18 on which the substrate SB that is disposed at the opposite position and on which the thin film of the target material TG is formed is deposited. Two plate-like members 22a and b each having a plurality of through holes provided so as to surround the outer periphery on the target holder 14 side were overlapped. And a node 20.

The vacuum vessel 12 is a highly airtight vessel formed of iron, stainless steel, aluminum or the like that maintains a predetermined degree of vacuum for performing sputtering. In the illustrated example, the vacuum vessel 12 is grounded and forms a film therein. A gas introduction pipe 12a for introducing the necessary gas and a gas discharge pipe 12b for exhausting the gas in the vacuum vessel 12 are attached.
As the vacuum container 12, various vacuum containers such as a vacuum chamber, a bell jar, and a vacuum tank used in a sputtering apparatus can be used.

In the vacuum vessel 12, argon (Ar), a mixed gas of argon (Ar) and oxygen (O ₂ ), or the like can be used as the gas introduced into the vacuum vessel 12 from the gas introduction tube 12 a.
The gas introduction pipe 12a is connected to a supply source (not shown) of these gases.
On the other hand, the gas discharge pipe 12b has a predetermined degree of vacuum inside the vacuum vessel 12, and in order to exhaust the gas in the vacuum vessel 12 in order to maintain this predetermined degree of vacuum during film formation, a vacuum pump or the like Connected to the exhaust means.

  The target holder 14 is a cathode electrode, and is disposed above the inside of the vacuum vessel 12 while being insulated from the other parts of the vacuum vessel 12, and has a thin film composition such as a piezoelectric film formed on the surface thereof. A target material TG having a suitable composition is mounted and held, and is connected to the high-frequency power source 16.

The high frequency power supply 16 is for supplying a high frequency power (negative high frequency) for turning a gas such as Ar introduced into the vacuum vessel 12 into a plasma to the target holder 14, one end of which is a target. It is connected to the holder 14 and the other end is grounded although not shown.
The high-frequency power applied to the target holder 14 by the high-frequency power supply 16 is not particularly limited, and examples thereof include 13.65 MHz, a maximum of 5 kW, or a maximum of 1 kW of high-frequency power, for example, 50 kHz to 2 MHz, It is preferable to use high frequency power of 27.12 MHz, 40.68 MHz, 60 MHz, 1 kW to 10 kW.

The target holder 14 is discharged by applying high-frequency power (negative high-frequency) from the high-frequency power source 16, and plasmas the gas such as Ar introduced into the vacuum vessel 12 to generate positive ions such as Ar ions. Therefore, the target holder 14 can also be called a cathode electrode or a plasma electrode.
The positive ions generated in this way sputter the target material TG held by the target holder 14. In this way, the constituent elements of the target material TG sputtered by the positive ions are released from the target material TG, and are neutralized or ionized, on the substrate SB held on the mounting table 18 arranged to be opposed to each other. Vapor deposited.
In this way, a plasma space P containing positive ions such as Ar ions, constituent elements of the target material TG, ions thereof, and the like is formed between the target holder 14 and the mounting table 18 inside the vacuum vessel 12.

The mounting table 18 is disposed below the inside of the vacuum vessel 12 at a position facing the target holder 14, and a constituent element (component) of the target material TG held by the target holder 14 is deposited on the mounting table 18. For holding the substrate SB on which a thin film such as is formed, that is, supporting from the lower surface in the figure.
Although not shown, the mounting table 18 includes a heater (not shown) for heating and maintaining the substrate SB at a predetermined temperature during the formation of the substrate SB.
Further, the size of the substrate SB to be mounted on the mounting table 18 is not particularly limited, and may be a normal 6-inch size substrate, a 5-inch or 8-inch size substrate, A substrate having a size of 5 cm square may be used.
In the present embodiment, the substrate SB is electrically insulated and a predetermined voltage is applied.

  As shown in FIGS. 1 and 2, the anode 22 is composed of two rod-like bodies 24 and two plate-like members 22 a and b, and the plate-like members 22 a and 22 b are orthogonal to the surface of the mounting table 18. The two plate-like members 22a and 22b are supported by the two rod-like bodies 24 from the lower surface of the vacuum vessel 12 so as to be stacked while being separated from each other in the direction in which the target holder 14 and It is provided between the mounting table 18 so as to surround the outer periphery of the mounting table 18 on the target holder 14 side.

The rod-like body 24 is not particularly limited as long as the plate-like members 22a and 22b can be supported in a stacked state while being separated in a direction orthogonal to the surface of the mounting table 18. In the illustrated example, two rod-like bodies 24 are used. However, in the present invention, there is no particular limitation, and any number may be used as long as the plate-like members 22a and 22b can be supported in the above state. May be.
On the other hand, the plate-like members 22a and 22b are annular members having a plurality of through-holes 26 on the surface, as shown in FIGS.
In the present invention, the reason why the plate-like members 22a and 22b constituting the anode 20 have the through holes 26 will be described in detail later.
Further, in the present embodiment, the anode 22 is grounded as shown in FIG.

In the present embodiment, as shown in FIGS. 1 and 2, the anode 22 has a smaller inner diameter in the plate-like member 22b located on the mounting table 18 side than the other plate-like member 22a.
By configuring the inner diameters of the plate-like members 22a and 22b in the anode 22 as described above, gas can easily flow through the substrate SB, and a high-quality thin film can be formed on the substrate SB.

Further, the separation distance between the plate-like members 22a and 22b of the anode 22 is preferably 1.0 mm or more so that electrons can enter and play a sufficient role as the anode, and the sputtered particles can be easily formed. It is preferably 15.0 mm or less so as not to enter and contaminate the anode.
In the present invention, the separation distance (gap distance) between the plate-shaped members 22 of the anode 22 is the surface of the mounting table 18 among the plurality of plate-shaped members 22 arranged so as to overlap in the direction orthogonal to the surface of the mounting table 18. In the plate member 22 adjacent (in a vertical relationship) in a direction orthogonal to the upper surface, the lower surface of the plate member positioned on the upper side (target side) and the upper surface of the plate member positioned on the lower side (substrate side) That is, in this embodiment, the distance between the lower surface of the plate-like member 22a in the drawing and the upper surface of the plate-like member 22b in the drawing.

Here, in the present invention, the reason why the plate-like members 22a and 22b constituting the anode 20 have a plurality of through holes 26 will be further described with reference to FIG.
FIG. 3 shows the anode and cathode at the time of plasma generation when the sheath (not shown) of the anode and cathode (target holder) is regarded as a capacitor, and the current density of ions (electrons) is uniform. It is a graph which shows the electric potential distribution between.
Note that the vertical axis of the graph shown in FIG. 3 represents a potential.

The present inventor obtains the potential distribution between the anode and the cathode at the time of plasma generation shown in FIG. 3, and from this, the energy of ions capable of generating sputtered particles from the target TG due to collision of ions (electrons). and V ₁ which represents the, were determined and V ₂ representative of the energy of the ion damage to the substrate by ion bombardment.

The relationship represented by the following formula 1 is established between the V ₁ and V ₂ and the surface area A ₁ of the cathode and the surface area A _{2 of the} anode.

[Equation 1]
(V ₁ / V ₂ ) = (A ₂ / A ₁ ) ⁴

That is, when the area of the anode is reduced according to the above formula 1, the present inventor increases the ratio of V _{2 to} V ₁ , that is, reverse sputtering easily proceeds, and the plasma state in the vacuum vessel 12 is It was found that it changed from the normal state.

  However, as described above, when an anode having a complicated shape with an increased surface area of the anode is used, cleaning for removing the attached film is often very difficult, and also increases the surface area of the anode. In addition, when an anode having a volume larger than that of the conventional one is used, there is a problem that the problem that the film forming apparatus itself has to be enlarged cannot be solved.

  Therefore, the present inventor has found that the anode is composed of a plate-like member so that cleaning for removing the attached film can be easily performed while increasing the surface area of the anode, and further, when using a simple plate-like member In order to further increase the surface area, the inventors have found that the anode is composed of a plate-like member provided with a plurality of through holes.

As described above, the film forming apparatus 10 according to the present invention uses the anode 20 having a configuration in which the plate-like members 22 having a plurality of through holes 26 are stacked, so that electrons are transmitted through the through holes 26. Therefore, the effective anode area is increased, and thereby reverse sputtering on the substrate can be suppressed, and as a result, a high-quality thin film can be formed.
Furthermore, since the film does not easily adhere to the lower anode, the plasma state in the vacuum vessel 12 can be stabilized for a long period of time without reducing the effective anode area by film formation.

  Further, as described above, the anode 20 having the above-described configuration is configured by the plate-like member 22, so that it can be performed very simply and repeatedly when performing cleaning to remove the adhered film. Can also be used very simply.

In the present embodiment, as shown in FIGS. 2A and 2B, the plate-like member 22 is the plate-like member 22 constituting the anode 22 when the anode 22 is viewed from the target TG. The position of the through hole 26 of the plate-like member 22a located on the target TG side and the position of the through-hole 26 of the plate-like member 22b located on the substrate SB side (indicated by a dashed line in FIG. 3A) That is, the positions of the plurality of through holes 26 of the plate-like members 22 adjacent in the upper and lower directions in the drawing are arranged so as not to coincide with each other in the direction orthogonal to the surface of the mounting table 18.
By configuring the anode 22 in this way, the through holes 26 are arranged at an angle with respect to the target TG, so that the particles of the sputtered target TG are located on the lower side in the vacuum vessel 12. It can prevent effectively adhering to the lower surface of the plate-shaped member 22 or the vacuum vessel 12.

  In the above embodiment, the anode 22 is composed of the rod-like body 24 and the two plate-like members 22, and the plate-like member positioned closer to the mounting table 18 has a smaller inner diameter. In other words, the shortest distance from the center of the plate-like member 22 to the inner surface of the plate-like member is reduced. However, in the present invention, the present invention is not limited to this. One or a plurality of sheets may be stacked in a direction orthogonal to the surface of the mounting table 18.

  For example, in the above embodiment, the annular plate-like member 22 is used to improve the uniformity of the film to be formed. However, the present invention is not limited to this, and the target holder of the mounting table 18 is not limited thereto. There is no particular limitation as long as it is a plate-like member having a shape that can surround the outer periphery on the 14 side, and it may be an annular plate-like member having a quadrangle, an ellipse, or other shapes, You may use the plate-shaped member of the shape which the part or several parts interrupted.

In the above embodiment, the plate-like member 22 located on the substrate SB side has a smaller inner diameter, that is, the plate-like member 22 located on the substrate SB side is closer to the inside of the plate-like member 22 from the center of the plate-like member 22. Although the plate-like member 22 having the shortest distance to the side surface is used, the present invention is not limited to this, and the same plate-like member 22 may be used for both the outer diameter and the inner diameter.
The shortest distance from the center of the plate-like member 22 to the inner surface of the plate-like member 22 is, for example, an inner diameter as described above if the plate-like member 22 has an annular shape. If so, the distance from the center of the rectangle to the center of the long side of the rectangle.

  The film forming apparatus of the present invention is basically configured as described above, and the operation and the film forming method of the present invention will be described below.

First, in the film forming apparatus 10 shown in FIG. 1, a sputtering target material TG is mounted and held on a target holder 14 provided in a vacuum vessel 12, and is opposed to the target holder 14 in the vacuum vessel. A substrate SB on which a thin film such as a piezoelectric film is formed is mounted and held on a mounting table 18 that is spaced apart from the mounting position.
In the present invention, the target is preferably a dielectric, a piezoelectric, an insulator, or a ferroelectric.

  Next, the vacuum vessel 12 is evacuated from the gas discharge pipe 12b until a predetermined degree of vacuum is reached, and while continuing to be evacuated so as to maintain the predetermined degree of vacuum, the gas introduction pipe 12a is used for plasma such as argon gas (Ar). Continue to supply gas in predetermined amounts. At the same time, a high frequency (negative high frequency power) is applied from the high frequency power source 16 to the target holder 14 to discharge the target holder 14, and a gas such as Ar introduced into the vacuum vessel 12 is turned into plasma, whereby Ar ions A plasma space is formed by generating plasma ions such as.

  Thereafter, the positive ions in the formed plasma space sputter the target material TG held by the target holder 14, and the constituent elements of the sputtered target material TG are released from the target material TG, and are neutral or ionized. In this state, vapor deposition is performed on the substrate SB held on the mounting table 18 which is disposed to face and separate, and film formation is started.

At this time, in the film forming method of the present invention, the anode V having the above configuration controls the difference Vs−Vf (V) between the plasma potential Vs (V) in the plasma and the floating potential Vf (V).
The reason will be described below.

FIG. 4 is a diagram schematically showing a state during film formation in the film forming apparatus as shown in FIG.
As schematically shown in FIG. 4, the gas introduced into the vacuum vessel 12 by the discharge of the target holder 14 is turned into plasma, and positive ions Ip such as Ar ions are generated, and the target holder 14 and the mounting table 18 are In other words, a plasma space P is generated between the target material TG held by the target holder 14 and the substrate SB held by the mounting table 18. The generated positive ions Ip sputter the target material TG. The constituent element Tp of the target material TG sputtered by the positive ions Ip is emitted from the target material TG and deposited on the substrate SB in a neutral or ionized state.

  The potential of the plasma space P becomes the plasma potential Vs (V). In the present invention, the substrate SB is normally an insulator and is electrically insulated from the ground. Therefore, the substrate SB is in a floating state, and the potential thereof is the floating potential Vf (V). The constituent element Tp of the target material TG between the target material TG and the substrate SB causes collision of ions having kinetic energy corresponding to an acceleration voltage Vs−Vf between the potential of the plasma space P and the potential of the substrate SB. Therefore, it is considered that the substrate SB during film formation collides with high energy. On the substrate, reverse sputtering also occurs due to ions having kinetic energy corresponding to the acceleration voltage of the potential difference Vs−Vf.

  The plasma potential Vs and the floating potential Vf can be measured using a Langmuir probe. When the tip of a Langmuir probe is inserted into the plasma P and the voltage applied to the probe is changed, for example, current-voltage characteristics as shown in FIG. 5 can be obtained (Mitsuharu Onuma, “Plasma and Film Formation Basics” p. .90, published by Nikkan Kogyo Shimbun). In FIG. 5, the probe potential at which the current becomes 0 is the floating potential Vf. This state is that the ion current and the electron current flow into the probe surface become equal. The surface of the metal in the insulating state and the surface of the substrate are at this potential. As the probe voltage is made higher than the floating potential Vf, the ionic current gradually decreases, and only the electron current reaches the probe. The voltage at this boundary is the plasma potential Vs.

It has been described that the potential difference Vs−Vf affects the kinetic energy of the constituent element Tp of the target material TG colliding with the substrate SB. Since the kinetic energy E is generally expressed as a function of the temperature T as shown in the following formula, the potential difference Vs−Vf is considered to have the same effect as the temperature with respect to the substrate SB.
E = 1 / 2mv ² = 3 / 2kT
(Where m is mass, v is velocity, k is a constant, and T is absolute temperature.)
The potential difference Vs−Vf is considered to have effects such as an effect of promoting surface migration and an etching effect of weakly coupled portions in addition to the same effect as temperature.

  In the present invention, when a voltage of the high-frequency power supply 16 is applied to the target holder 14 in order to form a film on the substrate SB, plasma is generated above the substrate SB and between the anode 20 and the substrate SB. In this case, when the plasma is confined in the anode 20 by this discharge, the plasma potential Vs decreases, and Vs which is the difference between the plasma potential Vs (V) and the floating potential Vf (V). It is considered that −Vf (V) decreases. In this way, when Vs−Vf (V) decreases, the energy with which the constituent element Tp of the target TG released from the target TG collides with the substrate SB decreases, and at the same time, reverse sputtering on the substrate is suppressed.

  Therefore, in the film forming method of the present invention, the difference Vs−Vf (V) between the plasma potential Vs (V) in the plasma and the floating potential Vf (V) is adjusted by the anode 20 having the above-described configuration. And optimize (control).

  The piezoelectric film obtained by the film forming method of the present invention as described above is a high-quality insulating film, dielectric film, or ferroelectric film free from variations in film quality and compositional deviation, particularly containing Pb such as PZT. This is a piezoelectric film made of perovskite-type oxide, with a stable growth of perovskite crystals with little pyrochlore phase and stable suppression of Pb detachment, and should be used as a piezoelectric element suitable for use in inkjet heads, etc. Can do.

Next, the structure of the liquid ejection apparatus (hereinafter also referred to as an inkjet head) of the present invention will be described.
FIG. 6 is a sectional view (a sectional view in the thickness direction of the piezoelectric element) of an embodiment of an inkjet head using an embodiment of the piezoelectric element according to the present invention. In addition, in order to make it easy to visually recognize, the scale of the component is appropriately changed from the actual one.

  As shown in FIG. 6, the inkjet head 50 of the present invention includes a piezoelectric element 52 according to the present invention, an ink storage / discharge member 54, and a diaphragm 56 provided between the piezoelectric element 52 and the ink storage / discharge member 54. And a nozzle (liquid discharge port) 70.

  The piezoelectric element 52 according to the present invention is an element including a substrate 58, a lower electrode 60, a piezoelectric film 62, and an upper electrode 64 that are sequentially stacked on the substrate 58. An electric field is applied in the thickness direction by the upper electrode 64.

The substrate 58 is not particularly limited, and examples thereof include silicon, glass, stainless steel (SUS), yttrium stabilized zirconia (YSZ), alumina, sapphire, silicon carbide, and the like. As the substrate 58, a laminated substrate such as an SOI substrate in which a SiO ₂ oxide film is formed on the surface of a silicon substrate may be used.
The lower electrode 60 is formed on substantially the entire surface of the substrate 58, and a piezoelectric film 62 having a pattern in which line-shaped convex portions 62a extending from the front side to the back side in the drawing are arranged in a stripe shape is formed thereon. The upper electrode 64 is formed on each convex portion 62a.
The pattern of the piezoelectric film 62 is not limited to that shown in the figure, and is designed as appropriate. The piezoelectric film 62 may be a continuous film, but the piezoelectric film 62 is not a continuous film, but is formed by a pattern made up of a plurality of protrusions 62a separated from each other, so that each protrusion 62a can be expanded and contracted smoothly. Therefore, a larger amount of displacement is obtained, which is preferable.

The main component of the lower electrode 60 is not particularly limited, and examples thereof include metals or metal oxides such as Au, Pt, Ir, IrO ₂ , RuO ₂ , LaNiO ₃ , and SrRuO ₃ , and combinations thereof.
The main component of the upper electrode 64 is not particularly limited, and the materials exemplified in the lower electrode 60, electrode materials generally used in semiconductor processes such as Al, Ta, Cr, and Cu, and combinations thereof Is mentioned.
The piezoelectric film 62 is a film formed by a film forming method to which the above-described sputtering method of the present invention is applied. The piezoelectric film 62 is preferably a piezoelectric film made of a perovskite oxide.
The thickness of the lower electrode 60 and the upper electrode 64 is, for example, about 200 nm. The film thickness of the piezoelectric film 62 is not particularly limited and is usually 1 μm or more, for example, 1 to 5 μm.

An ink jet head 50 shown in FIG. 6 is roughly external to an ink chamber (ink storage chamber) 68 in which ink is stored and an ink chamber 68 on the lower surface of the substrate 58 of the piezoelectric element 52 having the above-described configuration. An ink storing and discharging member 54 having an ink discharge port (nozzle) 70 through which ink is discharged is attached. A plurality of ink chambers 68 are provided corresponding to the number and pattern of convex portions 62 a of the piezoelectric film 62. That is, the inkjet head 50 has a plurality of ejection units, and the piezoelectric film 62, the upper electrode 64, the ink chamber 68, and the ink nozzle 70 are provided for each ejection unit. On the other hand, the lower electrode 60, the substrate 58, and the diaphragm 56 are provided in common for the plurality of ejection units, but are not limited thereto, and may be provided individually or in groups.
In the ink jet head 50, the electric field strength applied to the convex portion 62 a of the piezoelectric element 52 is increased or decreased for each convex portion 62 a by a conventionally known driving method, thereby expanding or contracting, thereby ejecting or ejecting ink from the ink chamber 68. The amount is controlled.
The ink jet head of the present invention is basically configured as described above.

  As described above, the film forming method and the film forming apparatus according to the present invention, and the ink jet head (liquid ejecting apparatus) including the piezoelectric element having the piezoelectric film formed by them are described in detail with various embodiments and examples. Although explained, this invention is not limited to the said embodiment and Example, Of course, in the range which does not deviate from the main point of this invention, various improvements and design changes may be performed.

  Hereinafter, specific examples of the present invention will be given, and the present invention will be described in more detail with reference to the accompanying drawings. Needless to say, the present invention is not limited to the following examples.

Example 1
As the film forming apparatus 10 shown in FIG. 1, a commercially available film forming apparatus (CLN2000 type manufactured by Oerlikon) was used.
As the target material TG, a sintered body of 300 mmφ Pb _1.3 (Zr _0.52 Ti _0.48 ) O ₃ composition was used.
The distance between the target material TG and the substrate SB was 60 mm.
Further, a stainless steel (SUS) plate-like member 22a having an outer diameter of 300 mmφ and an inner diameter of 220 mmφ is placed on the target material TG side, while the outer diameter of 300 mmφ and the inner diameter of 160 mmφ is surrounded so as to surround the outer periphery of the substrate SB on the target material TG side. A plate member 22ab made of stainless steel (SUS) was installed on the substrate side, and the anode 20 was provided.

Ar + O ₂ (2.5%) gas is introduced into the vacuum apparatus 12 as described above, 700 W is applied to the high frequency power supply 16 at 0.5 Pa, and a PZT (lead zirconate titanate) film is formed. Film formation was performed continuously for 7 hours.
At this time, the cathode self-bias Vdc and the substrate potential Vf were measured with the elapse of the film formation time using software installed in the above-mentioned commercially available apparatus (CLN2000 type manufactured by Oerlikon).

The change of the cathode self-bias Vdc with the film formation time at this time is shown by a white circle (◯) in FIG. 7, and the change of the substrate potential Vf with the film formation time at this time is shown by a white circle (◯) in FIG. .
In addition, XRD (X-ray diffraction) of the deposited film is performed every hour using an X'pert PRO X-ray diffractometer manufactured by PANalytica, and the ratio of the perovskite structure to the pyrochlore structure is determined by the XRD peak ratio. That is, a perovskite structure / pyrochlore structure was obtained, and the result is shown by white circles (◯) in FIG.

7 is a graph in which the vertical axis represents the cathode bias potential and the horizontal axis represents the film formation time, and FIG. 8 represents the substrate potential on the vertical axis and the film formation time on the horizontal axis. It is a graph.
On the other hand, FIG. 9 is a graph in which the vertical axis represents the ratio of the perovskite structure to the pyrochlore structure, that is, the perovskite / pyrochlore, and the horizontal axis represents the film formation time.

(Comparative Example 1)
A PZT (lead zirconate titanate) film was formed in the same manner as in the example except that the plate member constituting the anode did not have a through hole. It was done continuously.

A change in the cathode self-bias Vdc with the film formation time at this time is shown by a black circle (●) in FIG. 7, and a change in the substrate potential Vf with the film formation time at this time is shown by a black circle (●). .
Also, XRD (X-ray diffraction) of the deposited film is performed every hour using an X'pert PRO X-ray diffractometer manufactured by PANalytica, and the XRD peak ratio of the perovskite / pyrochlore is compared with the pyrochlore structure. The ratio of the perovskite structure, that is, the perovskite structure / pyrochlore structure was obtained, and the result is shown by black circles (●) in FIG.

(Comparative Example 2)
A PZT (lead zirconate titanate) film was continuously formed for 7 hours by the same method as in the example except that the plate-like member was not used.
The change in cathode self-bias Vdc with the film formation time at this time is shown by a triangle (▲) in FIG. 7, while the change in substrate potential Vf with the film formation time at this time is shown by a triangle (▲) in FIG. .
Also, XRD (X-ray diffraction) of the deposited film is performed every hour using an X'pert PRO X-ray diffractometer manufactured by PANalytica, and the XRD peak ratio of the perovskite / pyrochlore is compared with the pyrochlore structure. The ratio of the perovskite structure, that is, the perovskite structure / pyrochlore structure was obtained, and the result is shown by a triangle (▲) in FIG.

From the results shown in FIGS. 7 and 8, in Example 1, Vdc was −180 V immediately after the start of film formation, and Vf was +70 V, and Vdc was −170 V even after film formation was performed for 7 hours. , Vf was +75 V, showing almost no change.
That is, it was found that when the PZT film was formed as in the example, the potential between the electrodes in the vacuum vessel 12 was stabilized.

On the other hand, in Comparative Example 1, Vdc immediately after the start of film formation was −170 V and Vf was +60 V. However, it was found that as the film formation time elapses, Vdc increases and Vf decreases.
This is because the PZT film adheres to the anode provided with the plate-like member by reducing the effective anode area by using the anode composed of the plate-like member provided with a plurality of holes. This is thought to be because the drop in sheath potential around the target holder was reduced and the drop in sheath potential around the anode was increased.

In Comparative Example 2, Vdc immediately after the start of film formation was −85 V and Vf was approximately 0 V. However, as the film formation time elapses, Vdc increases and Vf is substantially unchanged. all right.
This is because the Vdc is higher and the Vf is lower than when the PZT film is formed as in the embodiment, so that the sheath potential around the target holder (cathode) that serves as the driving force for sputtering is obtained by not providing the anode. It is clear that the drop in the sheath potential around the anode, which is the reverse sputtering driving force, is large.

From the results shown in FIG. 9, it can be seen that in the example, the pyrochlore layer hardly exists in the formed PZT film even when the film formation is performed for 7 hours.
At this time, the piezoelectric characteristics of the PZT film formed as in the example were measured from the amount of displacement when driven at a voltage of 30 V. The piezoelectric characteristics were also good.
That is, it was found that by forming a PZT film as in the example, a high-quality PZT film can be formed even if the film is formed for a long time.

From the results shown in FIG. 9, in Comparative Example 1, the film formed 1 hour after the start of film formation was a film having a substantially 100% perovskite structure, whereas the film formed 6 hours after the start of film formation. The film formed was found to be a film having almost 100% pyrochlore structure.
Furthermore, at this time, the piezoelectric characteristics of the PZT film were measured in the same manner as in the example, but the piezoelectric performance was not shown.
That is, it was found that, as in Comparative Example 1, a high-quality PZT film could not be formed with the passage of the film formation time by using an anode composed of a plate-like member having no holes.

From the results shown in FIG. 9, it was found that in Comparative Example 2, the film formed one hour after the start of film formation was a film having a substantially 100% pyrochlore structure.
This is due to the fact that the effective area of the anode decreased dramatically at an early time after the start of film formation, and the film was no longer in the condition of being able to form a good film as in Example 1 during the growth.
That is, it was found that a high-quality PZT film could not be formed at an early stage after the start of film formation by using no anode as in Comparative Example 2.

  As described above, by using the anode 20 having the plate-like member 22 having the through-hole 26, it is possible to suppress a reduction in the effective area of the anode 20, particularly, by attaching a film to the through-hole 26 portion. It was found that the change in the plasma state can be suppressed within 12, and the change in the film quality due to the change in the plasma state can be greatly reduced.

  The film forming apparatus and the film forming method of the present invention can be applied to the case where a thin film such as a piezoelectric film, an insulating film, or a dielectric film is formed by a vapor phase growth method using plasma such as sputtering. The present invention can be applied to the formation of a piezoelectric film or the like used for a recording head, a ferroelectric memory (FRAM), a pressure sensor, or the like.

It is a schematic block diagram which shows notionally one Embodiment of the film-forming apparatus which enforces the film-forming method of this invention. It is a schematic diagram which shows typically the plate-shaped member which comprises the anode of the film-forming apparatus shown in FIG. It is a graph which shows the electric potential distribution between the anode and cathode at the time of plasma generation. It is a schematic diagram which shows typically the mode during the film-forming in the film-forming apparatus shown in FIG. It is explanatory drawing which shows the measuring method of the plasma potential Vs and the floating potential Vf in a sputtering device. It is sectional drawing which shows the structure of one Embodiment of the inkjet head of this invention. It is a graph which shows the change of the cathode self-bias Vdc accompanying the film-forming time. It is a graph which shows the change of substrate potential Vf accompanying film formation time. It is the graph which showed the change of the film quality of the PZT film | membrane accompanying film-forming time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Film-forming apparatus 12 Vacuum container 12a Gas introduction pipe 12b Gas discharge pipe 14 Target holder 16 High frequency power supply 18 Mounting stand 20 Anode 22 Plate member 24 Rod body 50 Inkjet head 52 Piezoelectric element 54 Ink storage discharge member 56 Vibration plate 58 Substrate ( Support substrate)
60, 64 Electrode 62 Piezoelectric film 68 Ink chamber 70 Ink discharge port IP plus ion P Plasma space SB substrate (deposition substrate)
TG Target material Tp Target material constituent elements

Claims (15)

A vacuum vessel capable of introducing and evacuating gas,
A target holder disposed in the vacuum container and holding a target to be a film forming material;
A substrate holder that is disposed in the vacuum container so as to face the target holder and holds a film formation substrate on which a thin film of the film formation material is formed;
An anode provided between the target holder and the substrate holder so as to surround an outer periphery of the substrate holder on the target holder side;
The anode is an annular plate member having a plurality of through-holes are those stacked several sheets double, and the shortest distance from the center of the annular extent the plate member positioned on the substrate holder side to the inner surface small,
The gas is introduced into the vacuum container, a voltage is applied between the target holder and the substrate holder to generate plasma, and a thin film of the film forming material is formed on the film forming substrate. A film forming apparatus.   The film forming apparatus according to claim 1, wherein the plate-like member is annular.   The film forming apparatus according to claim 2, wherein the annular shape is an annular shape. The anode is a stack of a plurality of the plate-like members separated from each other in a direction orthogonal to the substrate holder,
The film forming apparatus according to claim 1, wherein the plurality of through-holes of the adjacent plate-like members are arranged so as not to coincide with each other in a direction orthogonal to the substrate holder. . The anode is a stack of a plurality of the plate-like members separated from each other in a direction orthogonal to the substrate holder,
The film forming apparatus according to claim 1, wherein the adjacent plate-like members are arranged to be separated from each other by 1.0 mm to 15.0 mm.   The film forming apparatus according to claim 1, wherein the anode is grounded. Said anode, said the deposition substrate are electrically insulated, and film formation apparatus according to any one of claims 1 to 5, characterized in that a predetermined voltage is applied. A film forming method in which a plasma is generated between a target and a film formation substrate, and ions of the plasma collide with the target to form a thin film using the target as a film formation material on the film formation substrate. There,
Between the deposition substrate and the target, so as to surround the target side periphery of the deposition substrate, overlapping several sheets double annular plate member having a plurality of through holes, and the substrate The plate-like member located on the holder side is provided with an anode whose shortest distance from the annular center to the inner surface is small , and the anode causes the plasma potential Vs (V) and floating potential Vf in the plasma when the thin film is formed. A film forming method characterized by controlling a difference Vs−Vf (V) from (V).   The film forming method according to claim 8, wherein the target is a dielectric, a piezoelectric, an insulator, or a ferroelectric.   The film forming method according to claim 8, wherein the plate-like member is annular.   The film formation method according to claim 10, wherein the annular shape is an annular shape. The anode is a stack of a plurality of the plate-like members separated from each other in a direction orthogonal to the substrate holder,
The plurality of through holes of the adjacent plate-like members are arranged so as not to coincide with each other in a direction orthogonal to the film formation substrate. Membrane method. The anode is a stack of a plurality of the plate-like members separated from each other in a direction orthogonal to the substrate holder,
The film forming method according to claim 8, wherein the adjacent plate-like members are spaced apart from each other by 1.0 mm to 15.0 mm.   The film forming method according to claim 8, wherein the anode is grounded. Said anode, said the deposition substrate are electrically insulated, and film forming method according to any one of claims 8-13, characterized in that the predetermined voltage is applied.

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