JP2005319380A - Film formation method and film formation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance a crystallinity of a film in a film formation method by an aerosol deposition method. <P>SOLUTION: The subject film formation device includes a film formation chamber 4 arranged with a substrate 100 provided with a structure; an aerosol production chamber 3 for producing aerosol by blowing up powder of a material arranged in a vessel by carrier gas; a nozzle 6 for depositing a composition material of the powder of the material on the substrate by injecting the aerosol produced in the aerosol production chamber toward the substrate; and a reactive gas introduction part 10 for introducing a reactive gas for selectively etching a surface of the deposition substance into the film formation chamber by reacting with the deposition substance on the surface of the deposition substance formed on the substrate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a film forming method for depositing a raw material composition material on a substrate by spraying the raw material toward the substrate, and a film forming apparatus using the film forming method.

  PZT (Pb (lead) zirconate titanate) and other structures in which electrodes are arranged on both sides of the piezoelectric body, piezoelectric actuators, piezoelectric pumps, inkjet printer inkjet heads, ultrasonic transducers, etc. It is used for. In recent years, in such a structure, a plurality of insulating layers and a plurality of electrode layers are alternately stacked. That is, the inter-electrode capacitance of the entire device can be increased by connecting a plurality of stacked layers in parallel. For this reason, the element can be miniaturized while suppressing an increase in the electrical impedance of the element, and therefore, for example, application to MEMS (microelectromechanical system) -related devices is being promoted.

  As a related technique, Patent Document 1 discloses a plurality of columnar piezoelectric bodies, a dielectric portion positioned between the plurality of columnar piezoelectric bodies, and the plurality of columnar piezoelectric bodies so as to cross the plurality of columnar piezoelectric bodies. A composite piezoelectric body having at least one inner conductor extending in a direction intersecting the longitudinal direction of the body is disclosed. With such a structure, a composite piezoelectric body having a plurality of columnar piezoelectric bodies with a high aspect ratio and a small electrical impedance can be manufactured at low cost without degrading performance.

  By the way, in patent document 1, the laminated body is produced by using a piezoelectric green sheet and a conductive paste. However, when a green sheet is used, since a binder is mixed in the piezoelectric body, sufficient piezoelectric performance cannot be obtained in the piezoelectric body. In addition, since the heat treatment at a high temperature is included in the manufacturing process, there is a possibility that the piezoelectric body warps or the both peel off due to the difference in thermal expansion coefficient between the piezoelectric body and the conductor. Furthermore, since there is a problem in handling that the sheets are easily broken when the thin sheets are bonded together, it is difficult to divide the laminated body including such sheets to produce a fine element.

  Therefore, a film forming method called an aerosol deposition (AD) method has attracted attention as a method for forming each piezoelectric layer included in the laminate. With the AD method, raw materials such as PZT (Pb (lead) zirconate titanate) are sprayed from the nozzle toward the substrate and made to collide with the substrate or the previously formed film. This is a film forming method for depositing. In the AD method, the raw material powder sprayed at a high speed collides with and crushes the lower layer such as the substrate or the previously formed deposit, and the crushed surface generated at that time adheres to the lower layer. Such a film formation mechanism is called a mechanochemical reaction, and this reaction makes it possible to form a dense and strong film that does not contain impurities. Therefore, it is expected that the performance of an element including a piezoelectric body or the like can be improved by using the AD method, and various studies are made on a film forming apparatus and a film forming method. For example, Patent Document 2 discloses extracting and optimizing film forming conditions in each step in order to provide a stable film quality in a gas deposition method. The AD method is also called a jet deposition method or a gas deposition method.

As a related technique, in Patent Document 3, in the AD method, before the flow of ultrafine particles collides with the substrate, these ultrafine particles and the substrate are made of ions, atoms, molecular beams, high-energy atoms such as low-temperature plasma, and molecules. By irradiating a certain high-speed high-energy beam, the contamination layer or oxide layer due to ultrafine particles or water molecules adhering to the substrate surface is removed or made amorphous without dissolving or decomposing the ultrafine particle material. Even when the flow rate of the ultrafine particles is slow, the ultrafine particle film forming method is disclosed in which the ultrafine particles and the substrate or the ultrafine particles are firmly bonded to each other to form a film.
JP 2003-189395 A (first page, fifth page, FIG. 1) JP 2001-152360 A (first page) Japanese Patent Laid-Open No. 2000-212766 (first page, FIG. 1)

However, in such an AD method, heat is generated when the ultrafine particles of the raw material collide with the lower layer, and the collision part may become amorphous. In such a case, the crystallinity of the formed film is worse than that of the raw material ultrafine particles. In addition, due to delicate conditions when the ultrafine particles collide with the lower layer, a weakly bonded portion may occur in the formed film. If many such poorly crystalline portions are present in the formed film, the function of the film and the durability may be reduced. Furthermore, as disclosed in Patent Document 3, when the injected ultrafine particle material is activated, a film having relatively good physical properties can be obtained. There is a problem in that a film that remains in the film or has a sufficiently satisfactory crystallinity cannot be obtained.
Therefore, in view of the above points, an object of the present invention is to improve the crystallinity of a film in a film forming method using an aerosol deposition method.

  In order to solve the above problems, a film forming method according to the present invention includes a step (a) of generating an aerosol by blowing up a raw material powder disposed in a container in which the aerosol is generated with a carrier gas, and The step (b) of introducing a reactive gas into the film chamber and the composition of the raw material powder by injecting the aerosol generated in the step (a) from the nozzle toward the substrate disposed in the film formation chamber. Depositing material on the substrate and selectively etching the surface of the deposit by reacting the deposit with a reactive gas at the surface of the deposit formed on the substrate; It has.

  In addition, the film forming apparatus according to the present invention generates an aerosol by generating a film forming chamber in which a substrate on which a structure is formed is disposed and a raw material powder disposed in the container by blowing up with a carrier gas. And a nozzle for depositing a raw material powder composition on the substrate by injecting the aerosol generated by the aerosol generating means toward the substrate, and the deposit on the surface of the deposit formed on the substrate. And reactive gas introduction means for introducing a reactive gas for selectively etching the surface of the deposit into the film formation chamber.

  According to the present invention, by introducing a reactive gas into the film formation chamber, the surface of the deposit, that is, the weakly bonded portion on the growth surface of the film is selectively etched while performing the film formation by the AD method. Only the portion having good crystallinity can be left in the film. Therefore, the film quality including crystallinity can be improved without going through a high temperature process. Therefore, it is possible to improve the performance and yield of the device to which the film thus manufactured is applied, and to increase the degree of freedom in manufacturing process design.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. The same constituent elements are denoted by the same reference numerals, and the description thereof is omitted.
FIG. 1 is a schematic view showing a film forming apparatus according to the first embodiment of the present invention. This film forming apparatus is a film forming apparatus that uses an aerosol deposition (AD) method in which a raw material is deposited on a substrate by spraying an aerosol containing the raw material powder onto the substrate.

  The film formation apparatus shown in FIG. 1 includes a gas cylinder 1, transfer pipes 2a and 2b, an aerosol generation chamber 3, a film formation chamber 4, an exhaust pump 5, a nozzle 6, a substrate holder 7, a high-frequency power source (RF ) 8, a matching box (MB) 9, and a reactive gas introduction unit 10.

The gas cylinder 1 is filled with nitrogen (N ₂ ), oxygen (O ₂ ), helium (He), argon (Ar), dry air or the like used as a carrier gas. Further, the gas cylinder 1 is provided with a pressure adjusting unit 1a for adjusting the supply amount of the carrier gas.

  The aerosol generation chamber 3 is a container in which a fine powder of a raw material that is a film forming material is placed. By introducing a carrier gas from the gas cylinder 1 into the aerosol generation chamber 3 through the transport pipe 2a, the raw material powder disposed there is blown up to generate the aerosol 101. The generated aerosol 101 is supplied to the nozzle 6 through the transport pipe 2b.

In the film forming chamber 4, a nozzle 6 for injecting aerosol and a substrate holder 7 for holding the substrate 100 are arranged. Further, the inside of the film forming chamber 4 is exhausted by an exhaust pump 5, thereby maintaining a predetermined degree of vacuum. Further, the film forming chamber 4 is connected to a ground wiring.
The nozzle 6 has, for example, an opening having a length of about 5 mm and a width of about 0.5 mm, and sprays the aerosol 101 supplied from the aerosol generation chamber 3 toward the substrate 100 at a high speed.

  The substrate holder 7 is a holder for holding the substrate 100 and is also used as an electrode for generating plasma in the film forming chamber 4. The substrate holder 7 is insulated from the film forming chamber 4 and is electrically connected to a high-frequency power source 8 through a matching box 9. The substrate holder 7 is provided with a substrate holder driving unit 7a that moves the substrate holder 7 three-dimensionally. Thereby, the relative position and relative speed between the nozzle 6 and the substrate 100 are controlled.

  The high frequency power supply 8 is a high frequency power supply for plasma generation that generates an alternating voltage with a frequency of 13.56 MHz, for example. The matching box 9 performs impedance matching between the load and the high frequency power supply 8 by canceling the reactance component of the load. As the matching box 9, for example, a matching box using a blocking capacitor can be used. The blocking capacitor cuts the DC component and passes only the AC component.

  Further, a reactive gas introduction unit 10 is provided in the film forming chamber 4. The reactive gas introduction unit 10 is used when a reactive gas (etching gas) for etching a film being formed is introduced into the film forming chamber 4. The type of reactive gas introduced into the film formation chamber will be described later.

Next, the film forming method according to the present embodiment will be described.
The film forming method according to the present embodiment is a film forming method in which a film is grown by the AD method while etching particles or crystals that are physically weakly present on the growth surface of the film. That is, the portion with poor crystallinity on the growth surface of the film is selectively removed, and only the portion with good crystallinity is left on the substrate. As a result, a film having good crystallinity, dense and strong, and good adhesion to the lower layer can be formed.

  In this embodiment, reactive ion etching is used as a method for etching the film. Here, the reactive ion etching means that ions generated by plasma are accelerated by a negative self-bias voltage generated by applying high-frequency power to an electrode (substrate holder) on which the substrate is placed. This is an etching method that collides with deposits. Therefore, the film forming apparatus shown in FIG. 1 includes a reactive gas introduction unit 10 for introducing a reactive gas into the film forming chamber 4 and a substrate holder 7 for generating plasma in the film forming chamber 4. A box 9 is provided.

FIG. 2 shows a circuit constituted by the film forming chamber 4, the substrate holder 7, the high frequency power supply 8, and the matching box 9 shown in FIG.
As shown in FIG. 2, the film forming chamber 4 and the substrate holder 7 function as an anode and a cathode in parallel plate type high frequency discharge, respectively. The blocking capacitor of the matching box 9 is connected in series with the plasma load between the anode and the cathode, and the cathode is in a floating state in terms of direct current. When electric power is supplied to the circuit shown in FIG. 2 from the high frequency power supply 8, glow discharge occurs and capacitively coupled (CCP) type plasma is generated. At that time, during the plasma space, positive plasma potential V _PL is generated with respect to the ground potential, the cathode, the negative potential V _BI occurs with respect to the ground potential by the self-bias effect. As a result, a potential distribution as shown in FIG. 3 is generated between the anode and the cathode. For details of the principle of self-bias generation, see pages 63-66 of Mitsuharu Onuma, “Plasma and Fundamentals of Film Formation” (Nikkan Kogyo Shimbun).

  In addition to the glow discharge and the method for generating plasma, known methods such as a direct current pulse method and an asymmetric bipolar plasma method can be used as used in sputtering and etching. For example, see Brain N. Chapman, translated by Yukio Okamoto, “Plasma Processing Fundamentals” (Denki Shoin).

As the types of reactive gases introduced into the film formation chamber 4, for example, as described on page 312 of “Micromechanical System Practical Application Overview” (issued by Fuji Techno System Co., Ltd.) Fluorine gas containing carbon fluoride (CF ₄ ), sulfur hexafluoride (SF ₆ ), nitrogen trifluoride (NF ₃ ), chlorine gas containing carbon tetrachloride (CCl ₄ ), silicon tetrachloride (SiCl ₄ ) Corrosive gas such as chlorine-fluorine gas containing chlorotrifluoromethane (CClF ₃ ) can be used. In this case, since reactive ions are generated by the plasma in the film forming chamber 4, the film is etched mainly by chemical action.

The gas introduced into the film forming chamber 4 is selected according to the material of the film to be formed, and according to the film forming conditions such as the film forming speed and temperature in order to obtain a desired reaction speed and the like. It is desirable to use a solution diluted to an appropriate concentration. In that case, a simple gas such as hydrogen (H ₂ ), nitrogen (N ₂ ), oxygen (O ₂ ), a rare gas such as helium (He) or argon (Ar), methane (CH ₄ ), ethane An organic compound gas such as (C ₂ H ₆ ) can be used. For example, when forming a PZT film, it is preferable to use a Cl-based or F-based gas mixed with argon.

Using the film forming method according to this embodiment, a PZT film was manufactured as follows.
First, in the film forming apparatus shown in FIG. 1, a substrate (SUS substrate) formed of SUS (stainless steel) 304 was set on the substrate holder 7, and the substrate holder 7 was kept at about 500 ° C. Further, the inside of the film forming chamber 4 was evacuated to about 50 Pa using an exhaust pump 5. Next, niobium oxide (Nb ₂ O ₅ ) -added PZT (52/48) particles having a particle size of about 0.3 μm are arranged in the aerosol generation chamber 3 as raw material powder, and argon gas or oxygen gas is used as a carrier gas. Was supplied at a predetermined flow rate to generate an aerosol. Further, the generated aerosol was supplied to the nozzle 6 and sprayed from the nozzle 6 toward the SUS substrate to start film formation.

On the other hand, simultaneously with the start of film formation, carbon tetrafluoride is introduced as a reactive gas from the reactive gas introduction unit 10 at a flow rate of 5 SLM (L / min, at 0 ° C. 101.3 kPa) and power is supplied from the high frequency power source 8. And a glow discharge was generated from the substrate holder 7. At that time, the DC component applied to the SUS substrate was −120V. As a result, plasma 102 having a plasma power of about 3 W / cm ² was generated, and etching was performed by reactive ions generated from the reactive gas. Further, after the film formation was completed, the formed PZT film was taken out from the film formation chamber 4 and subjected to a polarization treatment.
Further, as a comparative example, a PZT film was manufactured without performing etching under the same film forming conditions using the above film forming apparatus and film forming material.

  When the performance of the PZT film thus manufactured was measured, the PZT film of the comparative example had a piezoelectric constant of d33 = 150, whereas the PZT film formed by the film forming method according to this embodiment ( In Example), d33 = 250. That is, it can be seen that a film having good crystal constant and good crystallinity can be formed by performing film formation by AD method while performing etching. Moreover, in the PZT film | membrane of an Example, both the adhesiveness to a board | substrate and hardness (Vickers hardness) were favorable. In addition, when the direct current component applied to the SUS substrate was larger than −10 V (the absolute value was small) when the glow discharge was generated, the etching was not performed so much. There was little difference. On the other hand, when the direct current component applied to the substrate is smaller than −1000 V (the absolute value is increased), the selectivity becomes too high in etching, resulting in a composition shift.

  As described above, according to the present embodiment, the crystallinity, strength, and the like of a film formed by the AD method can be improved without going through a high temperature process. Therefore, the performance and durability of the device to which such a film is applied can be improved. In addition, since it is possible to prevent film warpage and peeling from the substrate that are likely to occur during a high-temperature process, the manufacturing yield can be improved. Furthermore, since the high temperature process is not required, the degree of freedom in designing the manufacturing process can be increased.

The film forming method according to the present embodiment can be applied to, for example, the following device manufacturing process.
As disclosed in Japanese Patent Laid-Open No. 2002-190512, an alumina (Al ₂ O ₃ ) film for an electrostatic chuck is preferably as hard and dense as possible. By using an AD method, a sputtering method or a green sheet can be used. Compared with the case where the method is used, a film having favorable characteristics can be manufactured. When performing the AD method, as described above, by selectively etching the weakly bonded portion, it becomes possible to obtain an alumina film that is stronger and denser than the normal AD method.

  In addition, a piezoelectric (PZT) film used for an ink jet head of an ink jet printer or the like is generally formed by forming a film at a high temperature of 600 ° C. or higher. The types of substrates that can be used at such high temperatures are limited, the range of material selection is narrow, and the film forming apparatus itself is expensive in order to cope with high temperatures. However, by using the film forming method according to the present embodiment, it is possible to form a PZT film having good crystallinity and good performance at a lower temperature (for example, 500 ° C.). Therefore, in the past, SUS430 was mainly used as a substrate, but more general-purpose SUS304 can be used, and the cost can be reduced.

Next, a film forming apparatus according to a second embodiment of the present invention will be described with reference to FIG.
The film forming apparatus shown in FIG. 4 has a gas cylinder 20 connected to the aerosol generation chamber 3 via a transfer pipe 20b instead of the reactive gas introduction unit 10 shown in FIG. Other configurations are the same as those of the film forming apparatus shown in FIG.

The gas cylinder 20 is filled with a reactive gas used for etching a film formed by the AD method. The type of reactive gas is the same as that described in the first embodiment.
In the present embodiment, the reactive gas is introduced into the film formation chamber 4 together with the aerosol 103 by introducing the reactive gas into the aerosol generation chamber 3. In that case, the concentration of the reactive gas can be adjusted by controlling the pressure adjusting unit 20 a provided in the gas cylinder 20. As a result, the reactive gas is sprayed onto the region where the film is being formed, so that a weakly bonded portion on the growth surface of the film can be efficiently etched with a small amount of the reactive gas.

Next, a film forming apparatus according to a third embodiment of the present invention will be described with reference to FIG.
The film forming apparatus shown in the present embodiment is obtained by further providing a counter electrode 30 with respect to the film forming apparatus shown in FIG. Other configurations are the same as those of the film forming apparatus shown in FIG.
The counter electrode 30 is disposed so as to face the substrate holder 7 and is connected to the ground wiring. Such a counter electrode 30 acts as an anode in the circuit shown in FIG. Further, the counter electrode 30 has an opening 30a through which the aerosol 101 ejected from the nozzle 6 passes.

  In the film forming apparatus shown in FIG. 5, when electric power is supplied from the high frequency power source 8, glow discharge is generated between the substrate holder 7 and the counter electrode 30, and plasma 104 is generated. Since the plasma 104 is confined between the substrate holder 7 and the counter electrode 30, a more uniform plasma space can be formed as compared with the case where the counter electrode 30 is not provided. Therefore, a weakly bonded portion on the growth surface of the film can be selectively etched more stably. In this embodiment as well, the reactive gas may be supplied together with the aerosol as in the second embodiment.

  In the first and second embodiments of the present invention described above, plasma is generated using the principle of a parallel plate type, but various other plasma generation methods can be used. For example, as described in pages 729-731 of "Applied Physics Handbook" 2nd edition (Maruzen Co., Ltd.) edited by the Japan Society of Applied Physics, a plasma source that generates electron cyclotron resonance (ECR) plasma, or inductive coupling A plasma source that generates plasma (ICP) may be used.

  The present invention can be used in a film forming method for depositing a raw material composition material on a substrate by spraying the raw material powder onto the substrate.

It is a schematic diagram which shows the structure of the film-forming apparatus which concerns on the 1st Embodiment of this invention. It is a circuit diagram for demonstrating the principle of the plasma generation in the film-forming apparatus shown in FIG. It is a figure which shows the electric potential distribution produced between the anode and cathode shown in FIG. It is a schematic diagram which shows the structure of the film-forming apparatus which concerns on the 2nd Embodiment of this invention. It is a schematic diagram which shows the structure of the film-forming apparatus which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,20 Gas cylinder 1a, 20a Pressure adjustment part 2a, 2b, 20b Conveyance pipe | tube 3 Aerosol production | generation chamber 3a Container drive part 4 Film formation chamber 5 Exhaust pump 6 Nozzle 7 Substrate holder 7a Substrate holder drive part 8 High frequency power supply 9 Matching box 10 Reaction Reactive gas introduction part 30 counter electrode 30a opening 100 substrate 101, 103 aerosol 102, 104 plasma

Claims (11)

A step (a) of generating an aerosol by blowing up a raw material powder disposed in a container in which aerosol generation is performed by a carrier gas;
Introducing a reactive gas into the film forming chamber (b);
The aerosol generated in the step (a) is sprayed from a nozzle toward the substrate disposed in the film formation chamber, thereby depositing a raw material powder composition material on the substrate and forming the material on the substrate. Selectively etching the surface of the deposit by reacting the deposit with the reactive gas on the surface of the deposit,
A film forming method comprising:   The film forming method according to claim 1, wherein step (c) includes generating plasma for activating the reactive gas in the film forming chamber.   The film forming method according to claim 1, wherein step (b) includes introducing the reactive gas into the container in which generation of aerosol is performed.   The film forming method according to claim 1, wherein the reactive gas includes any one of a chlorine-based gas, a fluorine-based gas, and a chlorine-fluorine-based gas. The raw material powder composition material includes PZT (Pb (lead) zirconate titanate),
The reactive gas includes a mixed gas of chlorine gas or fluorine gas and argon gas,
The film-forming method of any one of Claims 1-4. A film forming chamber in which a substrate on which a structure is formed is disposed;
Aerosol generating means for generating an aerosol by blowing up the raw material powder disposed in the container with a carrier gas;
A nozzle for depositing a composition material of a raw material powder on the substrate by spraying the aerosol generated by the aerosol generating means toward the substrate;
Reactive gas introduction means for introducing into the film formation chamber a reactive gas for selectively etching the surface of the deposit by reacting with the deposit on the surface of the deposit formed on the substrate; ,
A film forming apparatus comprising:   The film forming apparatus according to claim 6, further comprising plasma generating means for generating plasma for activating the reactive gas in the film forming chamber.   The film forming apparatus according to claim 7, wherein the plasma generating unit generates plasma by applying a negative voltage to the substrate.   The film forming apparatus according to claim 8, wherein the plasma generation unit includes a high-frequency power source, a blocking capacitor, and an electrode that holds the substrate and is electrically connected to the high-frequency power source via the blocking capacitor. .   The film forming apparatus according to claim 9, wherein the plasma generation unit further includes a second electrode that is disposed to face the electrode and is connected to a ground wiring.   The film forming apparatus according to claim 6, wherein the reactive gas introducing unit is arranged to introduce a reactive gas into the film forming chamber via the aerosol generating unit.

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