JP2014060210A - Dry etching method and method for manufacturing piezoelectric device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dry etching method and a method for manufacturing a piezoelectric device, capable of highly accurately forming an etched material along a mask layer pattern by dry etching.SOLUTION: A dry etching method comprises the steps of: etching an etched material using an organic film as a mask material (etching step); removing a sidewall adhesion film 26 formed when the etched material removed by the etching step adheres to the organic film and a sidewall of the etched material etched by the etching step by ashing treatment (sidewall adhesion film removal step); and repeatedly performing the etching step and the sidewall adhesion film removal step so that the etched material becomes a desired depth (repetition step). There is also provided a method for manufacturing a piezoelectric device including the dry etching method.

Description

  The present invention relates to a dry etching method and a piezoelectric device manufacturing method, and more particularly to a dry etching method and a piezoelectric device manufacturing method for accurately forming a pattern shape of anisotropic etching.

  When processing a piezoelectric film by dry etching, there are a method of etching at a high temperature using a hard mask and a method of etching at a normal temperature using a resist mask. When etching is performed at a high temperature, the apparatus becomes complicated and difficult, and thus room temperature etching using a resist is performed. However, in normal temperature etching using a resist, reaction products are generated from the resist, piezoelectric film, and etching gas during the etching, and adhere to and accumulate on the etched side wall. Therefore, there is a side wall deposit called a rabbit ear (fence). It was a problem. After the etching, the deposit on the side wall is deposited thick, and it is difficult to remove it.

  In order to prevent the formation of side wall deposits, for example, in Patent Document 1 below, a film of a difficult-to-etch material formed on a substrate is etched using plasma using a mask formed thereon. At the same time, a method is described in which etching is performed using a mask whose side wall of the mask is less than 90 degrees with respect to the surface of the substrate.

  Further, Patent Document 2 below describes a method of performing dry etching using a resist mask having a rounded outer periphery of the head, performing over-etching after dry etching, and removing the sidewall adhesion film. Yes. By making the outer peripheral part of the head of the resist mask round, it is possible to obtain a side wall adhesion film having a forward taper shape, and the amount of the side wall adhesion can be reduced.

JP 2003-257950 A JP 2003-152108 A

  However, since the method described in Patent Document 1 uses a tapered mask, the film to be etched also has a tapered shape, and it has been difficult to achieve high definition and density. Further, since the taper angle controllability of the mask material is difficult (bad), the reproducibility is poor, and as a result, the reproducibility of the taper angle of the film to be etched is also poor, resulting in a reduction in product quality. Further, in the method described in Patent Document 2, etching is performed using a round-shaped mask, and the sidewall adhesion film adhering to the side surface of the pattern is removed by overetching. Therefore, the film to be etched has a tapered shape. Therefore, a decrease in pattern accuracy was observed.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a dry etching method and a piezoelectric device manufacturing method capable of forming a pattern with high accuracy.

  In order to achieve the above object, the present invention uses an organic film as a mask material to etch the material to be etched, and the material to be etched removed by the etching process is etched by the organic film and the etching process. The material to be etched has a desired depth in the sidewall adhesion film removing step of removing the sidewall adhesion film formed by adhering to the sidewall of the material to be etched by ashing, the etching step, and the sidewall adhesion film removing step. Thus, there is provided a dry etching method having a repeated process.

  According to the present invention, the material to be etched removed by the etching process forms a sidewall adhesion film on the sidewall of the organic film and the etched material to be etched. The etching process and the sidewall adhesion film are subjected to ashing treatment. Dry etching is performed while repeating the sidewall adhesion film removing step to be removed. Therefore, it is possible to prevent the side wall adhesion film from being formed on the side wall of the organic film, so that the accuracy of the mask pattern can be maintained. Therefore, the etching pattern of the material to be etched can be anisotropically etched with high accuracy.

  In the dry etching method according to another aspect of the present invention, it is preferable that the sidewall adhesion film removing step is performed after the ashing process.

  According to the dry etching method according to another aspect of the present invention, the sidewall adhesion film can be easily removed by performing a wet process after the ashing process. In particular, by using a mixed gas of a halogen gas and a CF-based gas as an etching gas, a sidewall adhesion film containing halogen and fluorine is formed, so that it can be easily removed by a wet process. Further, when a CF-based gas is used as the etching gas, the surface of the sidewall adhesion film contains fluorine and is water repellent. Therefore, by performing ashing treatment, oxygen radicals (O) and OH radicals can be bonded to the surface of the sidewall adhesion film to make it hydrophilic, so that the sidewall adhesion film can be easily removed by wet treatment. .

  In the dry etching method according to another aspect of the present invention, the material to be etched is preferably a piezoelectric film.

  A piezoelectric film can be used as the material to be etched.

  In the dry etching method according to another aspect of the present invention, the etching gas in the etching step preferably includes at least a CF-based gas.

  According to the dry etching method according to another embodiment of the present invention, the etching gas includes a CF-based gas, thereby ensuring a selection ratio between the organic film and the material to be etched and selectively etching the material to be etched. Can be done. Further, when the etching gas contains a CF-based gas, the sidewall adhesion film is formed of a component composed of C, CH, and CF, so that the surface becomes water-repellent. Therefore, it is effective to remove the sidewall adhesion film by ashing treatment.

  In the dry etching method according to another aspect of the present invention, the etching gas is preferably a mixed gas with a halogen gas.

  According to the dry etching method according to another aspect of the present invention, by using an etching gas as a mixed gas with a halogen gas, the selection ratio between the organic film and the material to be etched is ensured, and the material to be etched is more etched. It can be done selectively.

In the dry etching method according to another aspect of the present invention, the gas used for the ashing treatment preferably includes at least one of oxygen, nitrogen, hydrogen, argon, and H ₂ O.

  According to the dry etching method according to another aspect of the present invention, the gas used for the ashing treatment is a gas containing at least one of the above gases, whereby the sidewall adhesion film is removed by radicals. Can do.

  In the dry etching method according to another aspect of the present invention, the gas used for the ashing treatment preferably contains a fluorine-containing gas.

  According to the dry etching method of another aspect of the present invention, the sidewall adhesion film can be removed by fluorine radicals by using a gas containing fluorine.

  According to the dry etching method of another aspect of the present invention, it is preferable that the wet treatment is pure water cleaning.

  According to the dry etching method of another aspect of the present invention, the wet treatment can be easily performed by performing pure water cleaning.

  In the dry etching method according to another aspect of the present invention, the organic film is preferably a resist.

  According to the dry etching method according to another aspect of the present invention, etching can be performed with a simple configuration by using an organic film as a resist. Further, it can be selectively etched with respect to the material to be etched.

  In order to achieve the above object, the present invention provides a piezoelectric device having a structure in which a piezoelectric film that is a material to be etched is patterned by the dry etching method described above, and the patterned piezoelectric film and an electrode made of a conductive material are laminated. A manufacturing method is provided.

  According to the present invention, when the piezoelectric film is patterned, it can be formed with high pattern accuracy, so that the occurrence of a shape defect or the like can be suppressed. Thereby, while improving a yield, the device with the stable characteristic can be manufactured.

  In order to achieve the above object, the present invention provides a first electrode forming step of forming a first electrode made of a first conductive material on a substrate, and a piezoelectric film as a material to be etched is laminated on the first electrode. And a patterning step of patterning the piezoelectric film by etching the piezoelectric film by the dry etching method described above.

  According to the present invention, when patterning a piezoelectric film, it is possible to form a pattern with high pattern accuracy, and thus it is possible to suppress the occurrence of shape defects. Thereby, while improving a yield, the device with the stable characteristic can be manufactured.

  A device manufacturing method according to another aspect of the present invention includes a second electrode formation step of forming a second electrode of a second conductive material on the piezoelectric film before or after the patterning step. It is preferable to have.

  According to the device manufacturing method according to another aspect of the present invention, the second electrode formed on the piezoelectric film can be formed either before or after patterning of the piezoelectric film.

  According to the dry etching method and the piezoelectric device manufacturing method of the present invention, a pattern by dry etching can be formed with high accuracy.

It is explanatory drawing which showed the manufacturing process of the board | substrate which has an upper electrode. It is explanatory drawing which showed the patterning process of the piezoelectric film. It is a block diagram of a dry etching apparatus.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[Example of manufacturing process of piezoelectric element]
Here, a manufacturing process of the piezoelectric element is illustrated, and a dry etching method according to an embodiment of the present invention and a piezoelectric film patterning process using the dry etching method will be described. First, the manufacturing process of the substrate having the patterned upper electrode 20 will be described with reference to FIG.

(Step 1): Substrate Preparation Step First, as shown in FIG. 1A, a silicon (Si) substrate 10 is prepared.

(Step 2): Insulating Film Forming Step Next, an insulating film (for example, an oxide film such as SiO 2) 12 is formed on the silicon substrate 10 (FIG. 1B). As an example, a silicon oxide film is formed by CVD (Chemical Vapor Deposition), sputtering, vapor deposition, thermal oxidation, or the like.

(Step 3): Lower electrode formation step Next, an adhesion layer (for example, a Ti layer) 14 is formed on the insulating film 12, and a noble metal film corresponding to the lower electrode 16 is formed on the adhesion layer 14 ( FIG. 1 (c)). The lower electrode 16 is made of a noble metal material such as Pt (platinum), Ir (iridium), Ru (ruthenium) or an oxide film thereof. The lower electrode 16 can be formed by sputtering or CVD.

(Step 4): Piezoelectric Film Formation Step Next, as shown in FIG. 1D, a piezoelectric film 18 is formed on the lower electrode 16. The piezoelectric film 18 may be a film containing lead zirconate titanate (PZT) or the like, and may be formed by a sputtering method, a CVD method, a sol-gel method, or the like. Not only PZT but also lanthanum zirconate titanate (PLZT) or “PZTN” in which a part of Ti of PZT is replaced with Nb can be used.

(Step 5): Upper electrode formation step Next, a noble metal film corresponding to the upper electrode 20 is formed on the piezoelectric film 18 (FIG. 1E). The upper electrode 20 may be made of Pt, Ir, Ru, Al, AlSi, Au or an oxide film thereof (PtOx, IrOx, RuOx), and is formed by a sputtering method or a CVD method. PtOx is a generic name for platinum oxide, and “x” represents a positive number indicating the ratio of Pt and O. The same applies to IrOx and RuOx. IrOx is a general term for oxides of iridium, and RuOx is a general term for oxides of ruthenium.

(Step 6): Hard Mask Formation Step Next, a hard mask 22 that covers the upper electrode 20 is formed (FIG. 1F). The hard mask 22 may be made of a silicon oxide film, a silicon nitride film, an organic SOG (Spin on Glass) film, an inorganic SOG film, or a metal such as Ti, Cr, Al, or Ni. Here, as the hard mask 22, a silicon oxide film was formed by TEOS (Tetra Ethyl Ortho Silicate) -CVD method.

(Step 7): Resist Mask Forming Step Next, a resist 24 is formed on the hard mask 22 layer by spin coating or the like, followed by soft baking, exposure and development, and then post baking. In addition, you may perform the hardening process (UV cure) by ultraviolet irradiation instead of post-baking. Thus, the resist 24 for patterning the upper electrode is patterned (FIG. 1G).

(Step 8): Hard Mask Patterning Step When the hard mask 22 is a silicon oxide film, the hard mask 22 is patterned by a dry etching method (FIG. 1H).

(Step 9): Resist removal step Thereafter, the resist 24 used in the patterning step of the hard mask 22 is removed using an ashing method or a special stripping solution (FIG. 1 (i)).

(Step 10): Upper electrode patterning step Next, the upper electrode 20 is patterned. The patterning of the upper electrode 20 is performed by a dry etching method. The etching of the upper electrode 20 is preferably adjusted so that a good etching result can be obtained by adjusting the rate of the etching rate and the base film selection ratio by a combination of bias frequency, gas pressure, and etching gas conditions. As the etching gas, for example, a mixed gas of chlorine gas and oxygen gas is used.

  Next, a method for patterning the piezoelectric film 18 will be described with reference to FIG. FIG. 2 is an explanatory diagram of patterning of the piezoelectric film 18.

(Step 11): Resist mask forming step First, the hard mask 22 is removed. The hard mask 22 can be removed using an ashing method or a dedicated stripping solution using a dry etching method or a wet etching method.

  After the hard mask 22 is removed, a mask layer 34 made of an organic film is formed on the piezoelectric film 18 in order to dry-etch the piezoelectric film 18 (FIG. 2 (k)). A resist is preferably used as the organic film. By using a resist for the mask layer 34, it is possible to perform etching at room temperature, simplify the apparatus, and reduce costs. In addition, reactive organisms between the resist and the etchant can be easily removed. Hereinafter, an embodiment in which a resist is used as the material of the mask layer 34 will be described.

  As the resist, for example, OFPR series, TSMR series, PMER series of Tokyo Ohka Kogyo Co., Ltd., 1500 series, 10XT series of AZ Co., etc. can be used.

  As a method for forming a mask pattern on a silicon substrate, first, a resist material is applied by spin coating or spray coating to form a resist film on the entire surface. Next, the resist film is pre-baked. Pre-baking can be performed at an optimum temperature of various resist materials using a hot plate or an oven.

  Thereafter, the pattern of the photomask is transferred to the resist film by exposure. As an exposure apparatus, an aligner or a stepper can be used, and exposure can be performed with an optimum exposure amount for various resist materials. Depending on the resist used, PEB (Post Exposure Bake) may be performed after exposure.

  Subsequently, development is performed. Development is performed by immersing the substrate in a developer, rinsing with pure water, and drying the substrate. By development, either the exposed part or the unexposed part can be dissolved with a developer, and a pattern can be formed. As the developer, one suitable for the resist material is selected. Moreover, it is not limited to the method of immersing a developing solution, Well-known methods, such as a shower method, are applicable. Moreover, you may post-bake as needed. Post-baking is performed by heating the substrate using a hot plate or oven. As heating temperature and heating time, it can carry out for about 1 to 60 minutes at about 100-200 degreeC, for example. By performing post-baking, the curability of the resist can be promoted.

  Specifically, the resist film can be formed by the following method. For example, when AZ 10TX is used as the resist and the film thickness is 10 μm, the resist is dropped on the substrate and rotated at 1000 rpm for 30 seconds by a spin coater to form a resist film. The resist film is described below (Step 13): (Step 13-1) in the side wall adhesion film removing step: Film thickness of the piezoelectric film 18 to be dry-etched because it is removed by ashing (Step 12): It is preferable to set the film thickness so that the upper electrode 20 and the piezoelectric film 18 are not exposed until the patterning of the piezoelectric film 18 is completed, depending on the number of repetitions of the piezoelectric film patterning step and (Step 13): sidewall adhesion film removing step. The thickness of the mask layer (resist) 34 is preferably 2 to 5 times that of the piezoelectric film 18.

  Then, soft baking is performed by heating at 100 ° C. for 90 seconds using a hot plate.

Next, exposure using a contact aligner is performed. As the contact aligner, a commercially available device may be used. For example, MA-6 manufactured by SUSS Microtech Co., Ltd. can be used. The exposure amount can be performed at, for example, 1000 mJ / cm ² . Thereafter, development is performed. A commercially available developer can be used, and for example, AZ300MIF manufactured by AZ can be used. After immersing in the developer for about 10 minutes, rinsing with pure water is performed twice for 180 sec. Thereafter, moisture attached to the substrate is removed by a spin dryer or the like. Post-bake if necessary. The post-bake may be performed at an arbitrary temperature for about 120 seconds using a hot plate. Since the cross-sectional shape of the resist varies depending on the post-baking heating temperature, it is preferably performed at a temperature as required.

(Step 12): Piezoelectric film patterning step Next, the piezoelectric film 18 is patterned by dry etching (FIG. 2L).

  FIG. 3 is a configuration diagram of a dry etching apparatus used in the dry etching method according to the present embodiment. As the dry etching apparatus 110, for example, an inductive coupling plasma (ICP) apparatus is used. Other methods using plasma sources such as Helicon Wave Plasma (HWP), Electron Cyclotron Resonance (ECR) plasma, Surface Wave Plasma (SWP), etc. It is also possible to apply.

  The dry etching apparatus 110 includes a process gas supply unit 114 that supplies a process gas (etching gas) into the chamber 112 (vacuum vessel), an exhaust unit 116 that exhausts the gas in the chamber 112, and a pressure adjustment in the chamber 112. And a pressure adjusting unit (not shown) for performing. The pressure in the chamber 112 is adjusted by exhausting from the exhaust unit 116 while supplying the process gas from the process gas supply unit 114 into the chamber 112.

  A dielectric window 118 is hermetically attached to the upper surface of the chamber 112, and a loop coil antenna 120 is installed above the dielectric window 118 (atmosphere side). A high frequency power source (RF power source) 124 for generating plasma is connected to the antenna 120 via a matching circuit (matching unit) 122. The frequency of the high frequency power supply 124 can use a frequency band of 13.56 MHz or more and 60 MHz or less, for example, 13.56 MHz. Further, the high frequency power supply 124 may be pulse-driven.

  A stage 126 is installed in the chamber 112. The stage 126 is provided with a substrate cooling mechanism (not shown) provided with an electrostatic chuck or a clamp, and a substrate 128 to be etched is placed on the stage 126. A low frequency power supply 132 for applying a bias is connected to the stage 126 via a matching circuit 130. The frequency of the low frequency power supply 132 is 200 kHz or more and 2 MHz or less, for example, 500 kHz.

  In addition, when the bias power source is pulse-driven, the bias power source may be provided with pulse driving means. Further, when the bias power source is used by pulse driving, means for synchronizing the pulse period of the power source (high frequency power source 124) of the antenna 120 (for plasma generation) and the bias power source (low frequency power source 132) is used. do it.

When PZT which is the piezoelectric film 18 is dry-etched, as a process gas in the chamber, Cl ₂ (chlorine), BCl ₃ (boron trichloride), HBr (hydrogen bromide), SF ₆ (sulfur hexafluoride), CF ₄ (carbon tetrafluoride), CHF _{3 (trifluoromethane),} C 2 _{F 6 (hexafluoroethane),} C 3 _{F 8} (eight fluoride _propane), C 4 _{F 6} (hexafluoro _{butadiene), C} 4 F ₈ (cyclofluorane octafluoride), C ₅ F ₈ (octafluorocyclopentene), a mixed gas thereof, or a mixed gas with oxygen, nitrogen, or the like can be used.

  Etching is performed by applying a high frequency to a plasma generation antenna to generate plasma, and applying a bias high frequency to the stage on which the processing substrate is placed.

  For example, 13.56 MHz is used for the high frequency power supply for the antenna, and 500 kHz, which is a low frequency, is used for the high frequency power supply for the bias. The RF frequency for the antenna can also be used in the range of 13.56-60 MHz. As the low frequency power source, 100 kHz to 2 MHz can be used.

The following conditions can be mentioned as typical etching conditions. As the process gas, a mixed gas of 10% to 60% Cl ₂ and 40% to 90% C ₄ F ₈ can be used. For example, by setting the flow rate of Cl ₂ to 20 sccm and C ₄ F ₈ to 80 sccm, a mixed gas of 20% Cl ₂ and 80% C ₄ F ₈ can be obtained. By using a mixed gas of Cl ₂ and C ₄ F ₈ as an etching gas, the etching selectivity between the mask layer 34 and the piezoelectric film 18 can be increased, and the piezoelectric film 18 can be selectively etched. . The pressure of the etching gas is preferably 0.1 to 5 Pa, for example, 1.0 Pa. The antenna RF power is preferably 350 to 1000 W, for example, 500 W. The substrate bias power is preferably 50 to 500 W, for example, 200 W. When a resist is used for the mask, the stage temperature is preferably -20 to 30 ° C, and particularly preferably 5 ° C.

Etching gas: Cl ₂ flow rate 20 sccm, C ₄ F ₈ 80 sccm mixed gas, etching gas pressure 1.0 Pa, antenna RF power 500 W, substrate bias power 200 W, stage temperature 5 ° C. The etching rate of the piezoelectric film 18 (PZT) under conditions is about 200 nm / min. For example, the etching is performed for 1 minute, and the etching of PZT of about 200 nm is performed.

  As a result, the portion of the piezoelectric film 18 shown in FIG. 2K that is not covered with the mask layer 34 is removed by etching, and the piezoelectric film 18 is patterned leaving the portion covered with the mask layer 34. (FIG. 2 (l)).

When the piezoelectric film 18 is patterned, the etched piezoelectric film 18 component, etching gas component, and mask layer (resist) 34 component are deposited on the mask layer 34 and the etched piezoelectric film 18 sidewalls. Then, the sidewall adhesion film 26 is formed. The sidewall adhesion film 26 is composed of C and CH, which are resist components, Pd, Zr, Ti and their oxides in the case of PZT, and Cl ₂ which is a component of etching gas, and chlorine radicals ( Cl, Cl ₂ ), C ₄ F ₈ to CF radicals (CF, CF ₂ , CF ₃ ) and fluorine radicals (F) are considered, and the sidewall adhesion film 26 is considered to be water repellent. When the sidewall adhesion film 26 is formed, the pattern accuracy of the piezoelectric film 18 is lowered. Since the sidewall adhesion film 26 is difficult to remove when the film thickness is increased, the sidewall adhesion film is removed in the next step. Do.

  Note that the etching gas preferably does not contain an inert gas such as argon. When an etching gas containing an inert gas is used, sputter etching becomes dominant during etching, and atoms of PZT, which is a component of the piezoelectric film 18, are easily sputtered and adhere to the side wall. However, it becomes difficult to remove the sidewall adhesion film 26 in a later process.

(Step 13): Side wall adhesion film removal step (Step 13-1): Ashing process In the side wall adhesion film removal process, first, an ashing process is performed (FIG. 2 (m)).

  The sidewall adhesion film 26 is formed by (Process 12): Piezoelectric film patterning process. In the piezoelectric film patterning process, a CF-based gas is used as an etching gas. Therefore, the surface of the sidewall adhesion film 26 is water repellent. Therefore, since the direct wet (WET) process cannot be performed, the sidewall plasma 26 made of the CF polymer, the resist component, and the material to be etched is removed by performing the oxygen plasma process by the ashing process continuously after the etching.

  As the ashing treatment, ashing treatment using oxygen plasma can be performed. Moreover, it can also carry out using ICP (Inductive Coupling Plasma), a microwave asher, and a barrel-type asher.

  As the process gas, a gas containing oxygen, nitrogen, hydrogen, argon, helium, or a combination of these gases can be used.

  As conditions for the ashing treatment, for example, SWP using a microwave can be performed with oxygen gas at 200 sccm, 100 Pa, and a microwave output of 1 kW.

  In the case where the piezoelectric film is etched as the film to be etched, ashing can be performed with a dry etching apparatus for the piezoelectric film. Since the processing can be continuously performed by using the dry etching apparatus for the piezoelectric film, the cost can be reduced. The conditions of the piezoelectric film dry etching apparatus (ICP) can be performed with an oxygen gas of 100 sccm, a degree of vacuum of 10 Pa, an RF power of 500 W, and a processing time of 10 seconds.

The ashing treatment may be performed under the same conditions as described above. When peeling is difficult, it is preferable to add fluorine gas to oxygen gas. Fluorine gas includes SF ₆ (sulfur hexafluoride), CF ₄ (carbon tetrafluoride), CHF ₃ (trifluoromethane), C ₂ F ₆ (ethane hexafluoride), C ₃ F ₈ (propane octafluoride) ), C ₄ F ₆ (hexafluorobutadiene), C ₄ F ₈ (cyclobutane octafluoride), C ₅ F ₈ (octafluorocyclopentene), and the like.

Also, of H _{2 O} in the process gas can also be used vaporized gas. Further, oxygen, an inert gas, or a fluorine gas can be added and a plurality of combinations of gases can be used. That is, by the water vapor plasma treatment, the sidewall adhesion film can be removed by O, H, OH, and (F) radicals.

(Step 13-2): Wet treatment When it is difficult to remove the sidewall adhesion film 26 only by the ashing treatment, the sidewall adhesion film 26 can be removed by using the wet treatment together.

  The substrate subjected to the ashing process is wet-processed. By performing the ashing process, since the surface of the sidewall adhesion film 26 has been subjected to a hydrophilic treatment, the sidewall adhesion film 26 can be easily removed.

  The wet treatment is performed by washing the substrate with water, and the washing method may be performed using a commercially available cleaning apparatus, and may be performed with a batch type apparatus or a single wafer type apparatus. For example, washing with pure water can be performed, and a stripping solution for removing the polymer can also be used.

  (Step 12): The sidewall adhesion film 26 formed in the piezoelectric film patterning process is a film composed of components including a resist, a piezoelectric film (PZT), and an etching gas. (Step 12): In the piezoelectric film patterning step, the side wall adhesion film 26 becomes a film containing chlorine and fluorine by using a mixed gas of chlorine and fluorine-based gas as an etching gas. (Step 13-1): CF groups on the surface of the sidewall adhesion film 26 are removed by ashing treatment, and oxygen radicals (O) and OH radicals are bonded to the surface to make them hydrophilic. By making the surface hydrophilic, the sidewall adhesion film 26 can be removed by wet treatment. When wet treatment, in particular, when immersed in pure water, fluorine-based reaction products composed of fluorine radicals, for example, Pd-F, Zr-F, Ti-F, F, etc., react to produce HF, It becomes an etchant (etching solution) for removing the reaction product of PZT. As for the chlorine-based reaction product, HCl is produced and has the same effect.

  As described above, the patterning process of the piezoelectric film by dry etching and the sidewall adhesion film removal process by ashing process and wet process have a mechanism consisting of selection of etching gas, ashing process and wet process, and the sidewall adhesion film 26 is easily removed (peeled).

(Step 14): Repetition Step After that, (Step 12): Piezoelectric film patterning step, (Step 13): Side wall adhesion film removal step is repeatedly performed until the etching of the piezoelectric film 18 is completed (FIGS. 2 (n) to (n)). q)). According to the present embodiment, (Step 12): Piezoelectric film patterning step (Step 13): Side wall adhesion film removal step is repeatedly performed. Therefore, the side wall adhesion film 26 is formed in a state where the side wall adhesion film 26 is thin. Since it is removed, the angle between the substrate and the piezoelectric film 18 can be set to an angle close to 90 ° and within a range of 90 ° ± 5 °, and the pattern can be accurately formed along the mask pattern of the mask layer 34. it can.

  As described above, (step 13): the mask layer (resist) 34 is removed by the ashing process in the side wall adhesion film removing step, so care must be taken not to lose the mask layer (resist) 34. .

  (Step 12): Piezoelectric film patterning step and (Step 13): Side wall adhesion film removing step is, for example, when overetching is performed 20% when the piezoelectric film is 4 μm and the etching amount per one time is 0.2 μm. , The piezoelectric film 18 can be patterned by repeating 24 times. Note that since the etching amount varies depending on the location of the substrate, it is necessary to perform overetching in order to completely remove the film to be etched, and the amount of overetching can be determined as appropriate.

(Step 15): Mask Layer Removal Step After the etching of the piezoelectric film 18 is completed, the remaining resist is removed (FIG. 2 (r)). The removal of the mask layer (resist) 34 can be performed by an ashing process, and the ashing process can be performed by the above-described method.

<Other embodiments>
In the above-described embodiment, the dry etching of the piezoelectric film 18 is performed by repeating the patterning process by etching and the sidewall adhesion film removing process. However, the present invention is not limited to the piezoelectric film, and is not limited to the noble metal, Pt, Ir, Ru, and the like. Even in the upper electrode 20 made of a metal material such as an oxide (PtOx, IrOx, RuOx), patterning can be performed by repeating the patterning step and the sidewall adhesion film removing step. However, when the film thickness is small, the amount of the side wall adhesion film is small, so that it is not necessary to perform the adhesion film removal step. It is preferably used when etching a film of several μm or more.

  In the above embodiment, the piezoelectric film 18 is patterned after the upper electrode 20 is formed. However, the present invention is not limited to this, and the upper electrode 20 is formed after the piezoelectric film 18 is patterned. be able to. That is, the above (Step 5) to (Step 10) may be performed after (Step 15): Mask layer removing step.

<Application of piezoelectric element>
The piezoelectric element manufactured by the process described with reference to FIGS. 1 and 2 can be used for various applications such as an actuator and a sensor. For example, when used as a piezoelectric actuator for generating a droplet discharge pressure in an inkjet head, a pressure chamber (ink chamber) can be formed by processing a layer of the silicon substrate 10. A part of the silicon substrate 10 functions as a diaphragm, and a unimorph piezoelectric actuator is configured by a structure in which the lower electrode 16, the piezoelectric film 18, and the upper electrode 20 are laminated on the diaphragm. That is, FIGS. 1 and 2 can be grasped as the manufacturing process of the actuator. Further, the present invention is not limited to a unimoful type actuator, and can be applied to the manufacture of various types of actuators such as a bimorph actuator.

<Application to various devices>
The scope of application of the present invention is not limited to the piezoelectric devices exemplified above, and can be widely applied to various devices having a structure in which a dielectric and a conductive material (electrode) are laminated. Such devices include various devices such as capacitors, acceleration sensors, temperature sensors, memory devices, pyroelectric devices and the like.

  The present invention is not limited to the embodiments described above, and many modifications can be made by those having ordinary knowledge in the field within the technical idea of the present invention.

  DESCRIPTION OF SYMBOLS 10 ... Board | substrate, 16 ... Lower electrode, 18 ... Piezoelectric film, 20 ... Upper electrode, 26 ... Side wall adhesion film, 34 ... Mask layer, 110 ... Dry etching apparatus, 112 ... Chamber, 114 ... Process gas supply part, 116 ... Exhaust 118: Dielectric window, 120 ... Antenna, 124 ... High frequency power supply, 126 ... Stage, 128 ... Substrate, 132 ... Low frequency power supply

Claims (12)

An etching process for etching a material to be etched using an organic film as a mask material;
A sidewall adhesion film removing step of removing, by ashing, a sidewall adhesion film formed by the material to be etched removed by the etching process adhering to the organic film and the sidewall of the material to be etched etched by the etching process. When,
A dry etching method comprising: a repeating step of repeatedly performing the etching step and the sidewall adhesion film removing step so that the material to be etched has a desired depth.   The dry etching method according to claim 1, wherein the sidewall adhesion film removing step performs a wet process after the ashing process.   The dry etching method according to claim 1, wherein the material to be etched is a piezoelectric film.   The dry etching method according to claim 1, wherein the etching gas in the etching step includes at least a CF-based gas.   The dry etching method according to claim 4, wherein the etching gas is a mixed gas with a halogen gas. The dry etching method according to claim 1, wherein the gas used for the ashing treatment includes at least one of oxygen, nitrogen, hydrogen, argon, and H ₂ O.   The dry etching method according to claim 1, wherein the gas used for the ashing treatment includes a fluorine-containing gas.   The dry etching method according to claim 2, wherein the wet treatment is pure water cleaning.   The dry etching method according to claim 1, wherein the organic film is a resist material.   A piezoelectric film having a structure in which a piezoelectric film as the material to be etched is patterned by the dry etching method according to claim 1, and the patterned piezoelectric film and an electrode made of a conductive material are stacked. Device manufacturing method. A first electrode forming step of forming a first electrode of a first conductive material on a substrate;
A piezoelectric film forming step of laminating a piezoelectric film as the material to be etched on the first electrode;
A method for manufacturing a piezoelectric device comprising: a patterning step of etching the piezoelectric film by the dry etching method according to claim 1 and patterning the piezoelectric film.   The piezoelectric device according to claim 11, further comprising: a second electrode forming step of forming a second electrode made of a second conductive material on the piezoelectric film before or after the patterning step. Manufacturing method.

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