KR100487886B1 - Method for acoustic wave device using a laser - Google Patents

Abstract

 The present invention relates to a method for manufacturing an acoustic wave device, and discloses a method for manufacturing an acoustic wave device that simultaneously performs the planarization and cleaning of each thin film constituting the acoustic wave element using a laser, as well as removal of the photosensitive film used for patterning each thin film. According to the present invention, the planarization of the thin film is performed by a non-contact method using a laser, thereby improving the performance of the device. In addition, planarization and cleaning can be performed all at once, thus simplifying the manufacturing process.

Description

Method for manufacturing acoustic wave device using laser {Method for acoustic wave device using a laser}

The present invention relates to a method for manufacturing an acoustic wave device, and to a method for manufacturing an acoustic wave device capable of improving performance and simplifying a manufacturing process by simultaneously performing surface planarization and cleaning of each thin film constituting the acoustic wave device.

A thin film type acoustic wave device is a device that directly deposits a piezoelectric material on a semiconductor substrate to cause resonance due to piezoelectric properties. In addition to the piezoelectric thin film made of the piezoelectric material, various thin films may be formed in the thin film type acoustic wave device, and each thin film may be formed by various methods such as RF sputtering. Particularly, the piezoelectric thin film may be epitaxially grown in a columnar shape. .

In order to improve the crystallinity of the thin film, the flatness of the lower thin film is very important. If the flatness of the lower thin film is improved, not only the crystallinity of the thin film deposited thereon is improved, but also the adhesion between the thin films can be increased and the scattering of waves can be minimized, thereby improving the device characteristics. Therefore, the planarization process is considered indispensable as a method for improving the performance of the device.

Currently, the planarization process of a thin film type acoustic wave device is performed by a chemical mechanical polishing (CMP) method. In the CMP method, the surface is polished by adding chemicals, slurry, ultrapure water, etc. while rotating by applying an appropriate pressure to a material requiring planarization.

However, the CMP method has economical and environmental problems that require the use of consumer products such as slurries and hazardous chemicals, as well as separate cleaning after the process. In addition, fine defects or scratches may occur during the process due to the slurry and toxic chemicals used in the CMP process, and since the contact method is applied to pressure, physical stress is directly applied to the surface of the target substrate. It may cause damage. If the polishing rate is lowered to prevent damage to the substrate, the precision of the surface processing is lowered and the processing time is delayed, thereby lowering the process efficiency. In addition, there is a disadvantage that can not be applied to the patterned substrate.

1 is a flowchart of a process for manufacturing an acoustic wave device performing surface planarization using CMP. Referring to FIG. 1, the conventional method prepares a substrate, and alternately deposits SiO ₂ and W to form a buffer layer (s1). At this time, in order to improve the properties of the deposited film, SiO ₂ CMP and cleaning are performed after SiO ₂ deposition, and W CMP and cleaning are also performed after W deposition. Subsequently, Mo is deposited for the lower electrode, followed by CMP, followed by cleaning. After coating and patterning the photoresist on Mo, and then etching the Mo to form a lower electrode, and removing the used photoresist film (s2). Subsequently, ZnO deposition, CMP, and washing are performed, and after the process of applying and patterning the photoresist film, ZnO etching is performed, and the used photoresist film is removed and washed to form a piezoelectric layer (s3). Finally, the upper electrode is formed by Mo deposition, photoresist patterning, and Mo etching, and then the photoresist is removed and then cleaned (s4) and passivated (s5).

As described above, the conventional method repeats a series of unit processes consisting of thin film deposition-> thin film flattening (CMP)-> cleaning-> photoresist patterning-> etching of thin film-> photoresist removal-> (wet) cleaning. It's very complicated because it's going on. In addition, even when the thin film is planarized, the thin film is attacked by plasma or chemicals in the process of etching the thin film and removing the photoresist, and thus the fine roughness of the thin film is deteriorated again.

The technical problem to be achieved by the present invention is to provide a method of manufacturing an acoustic wave device that improves the planarization process for each thin film of the thin film type acoustic wave device.

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Method of manufacturing an acoustic wave device according to the present invention for achieving the above technical problem, forming a buffer layer on a substrate, forming a lower metal layer on the buffer layer, forming a first photosensitive film pattern on the lower metal layer Forming a lower electrode by etching the lower metal layer using the first photoresist pattern as an etch mask, and simultaneously removing the first photoresist pattern and planarizing the lower electrode surface by using a laser; Forming a piezoelectric layer pattern on an electrode, forming a second photoresist pattern on the piezoelectric layer, forming a piezoelectric layer pattern by etching the piezoelectric layer using the second photoresist pattern as an etch mask, and laser Simultaneously removing the second photoresist pattern and planarizing the surface of the piezoelectric layer by using the piezoelectric layer. Forming an upper electrode by forming an upper metal layer on the layer, forming a third photoresist pattern on the upper metal layer, etching the upper metal layer by using the third photoresist pattern as an etching mask, and using a laser And removing the third photoresist pattern. The laser energy density and the number of laser pulses are 50 mJ / cm ² to 1,000 mJ / cm ² and 1 to 1,000, respectively, and the laser pulse period is preferably performed within 1 to 1,000 Hz. The pressure of the chamber for performing the step using the laser is preferably 10 ^-6 torr at atmospheric pressure, and the heating temperature is in the range of 500 ° C at room temperature.

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Apparatus that can be used in the method for manufacturing an acoustic wave device according to the present invention for achieving the above another technical problem, a vacuum chamber and a pumping system, a laser generator for supplying a laser, an optical system for delivering the laser to the substrate (optical system, a transfer module that can transfer substrates fully automatically, a translation stage that can scan for full substrate processing, a gas box, and a computer control system (PC control) system).

Here, the laser may be a pulse or continuous wave, the optical system is an attenuator, homogenizer, condenser lens, mirror, doublet lens, field lens It may be provided with an aperture and a beam splitter. It may further include an energy detector and a beam profiler.

The conveying module may also include a sorter, a cassette, a cassette stage, an aligner, a cooling system and a robot, and the vacuum chamber and the pumping system may include a slit door, a quartz window, a heating system, It may be equipped with a quartz focus ring, pin up down, a rotating stage, various valves and pumps for pumping.

In the present invention, the planarization and / or cleaning process for each thin film of the thin film type acoustic wave device may be processed in a non-contact manner using a laser, thereby minimizing physical stresses generated in the conventional contact planarization process. The planarization and cleaning can be performed at the same time, thereby reducing the overall process time.

The method also reduces the roughness by irradiating a laser to all thin films of the acoustic wave element, and simultaneously performs an ashing process and a cleaning process to remove the polymer residue remaining after the etching process. It includes. All of the thin films may correspond to a metal layer, an insulating layer, a piezoelectric layer, and all the substrates used for manufacturing the acoustic wave device.

In addition, the device manufacturing process proceeds in the order of deposition of the thin film-> photoresist patterning-> thin film etching-> removal and planarization of the photoresist using a laser to prevent attack of the surface of the thin film by the cleaning liquid and simplify the device manufacturing process, Reduce device production costs and improve process efficiency.

Specific details of other embodiments are included in the detailed description and drawings. Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of a method and apparatus for manufacturing an acoustic wave device according to the present invention. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention and to those skilled in the art to fully understand the scope of the invention. It is provided for the purpose of understanding the invention, and the invention is defined only by the claims.

2 is a flowchart of a process for manufacturing an acoustic wave device using a laser according to the present invention, and FIG. 3 is a schematic cross-sectional view of the acoustic wave device according to the present invention. In the elastic wave device manufacturing process according to the present invention, surface planarization and / or cleaning using a laser is performed. In particular, after the etching process of the thin film, surface planarization and removal and cleaning of the used photoresist film are simultaneously performed.

Referring to FIGS. 2 and 3, first, a semiconductor substrate 100 such as silicon or GaAs is prepared, and an insulating layer, for example, SiO ₂ 101 and a metal layer, for example, W 102 are alternately repeatedly deposited. A buffer layer 105 is formed (s11). At this time, in order to improve the properties of the film deposited thereafter, the laser planarization step is performed after the deposition of SiO ₂ 101, and the laser planarization step is also performed after the deposition of W 102. Since the laser planarization step here is performed along with the planarization, the process can be simplified by merging two processes separated by the conventional CMP and wet cleaning.

When performing the laser planarization step, the laser energy density and the number of laser pulses are 50 mJ / cm ² to 1,000 mJ / cm ² and 1 to 1,000, respectively, and the laser pulse period is preferably performed within 1 to 1,000 Hz. In order to perform the laser planarization step, an acoustic wave device manufacturing apparatus according to the present invention may be used.

Figure 4 shows a schematic diagram of a device that can be used in the method for manufacturing an acoustic wave element according to the present invention. The apparatus is capable of transferring the substrate to the vacuum chamber 300, the pumping system 304, the laser generating unit 200 for supplying the laser, the optical system 201 for delivering the laser to the substrate 100, and the substrate fully automatically. Transport module 405, transport stage 500 capable of scanning for full substrate processing, gas box 305, and computer control system 306.

Referring to FIG. 4, the planarization method using the laser of the present invention will be described in more detail. The method includes loading the substrate 100 to be processed into the chamber 300, and scanning the laser beam emitted from the laser generator 200. Irradiating the processing target substrate 100 in the chamber 300 through the quartz window 301, and unloading the processing target substrate 100 from the chamber 300.

First, in the loading of the substrate 100 to be processed into the chamber 300, the substrate 100 may be loaded into a vacuum atmosphere, an atmosphere atmosphere, an inert gas atmosphere, or a reactive gas atmosphere. In case of inert gas atmosphere, inert gas such as Ar, N ₂ is used, and in case of reactive gas atmosphere, reactive gas related to thin film material such as NF ₃ , CF ₄ , O ₂ , H ₂ , Cl ₂ , N _x O _y is used. do. The atmosphere in the chamber 300 may inject reactive gas using the gas injection device 302 or change the temperature using the heating system 303 according to the material to be treated, and contaminants removed during the process may be pumped system. Eject it out of the chamber 300 through the 304.

In the step of irradiating the laser beam emitted from the laser generating unit 200 to the substrate 100 to be processed in the chamber 300, the laser beam is preferably in the form of a line beam having a predetermined width and length, but is rectangular or square. It may also be in the form. In addition, the laser beam is preferably a homogenized laser beam having a uniform intensity only within the width and length of the laser beam. The laser source herein may include any laser having photon energy, and laser oscillation is suitable for pulsed laser to obtain high energy, but continuous wave laser is included therein. In the case of a pulsed laser, the laser pulse duration is preferably several fs to several s. Excimer lasers (e.g., 157 nm wavelength F2 lasers, 193 nm wavelength ArF lasers, 248 nm wavelength KrF lasers, 308 nm wavelength XeCl lasers, etc.), CO ₂ lasers, Nd: YAG lasers, Ar lasers, etc. Can be used.

Optical system 201 includes an attenuator, homogenizer, focusing lens, mirror, dual lens, field lens, aperture, and beam splitter to shape or suitably adjust the shape of the beam. And all means that are capable of delivering the beam continuously. In addition, an energy detector capable of measuring laser energy and a beam profiler for measuring beam shape may be included.

When irradiating the laser beam, the process is performed by fixing the laser beam and moving the substrate to be processed by the transport stage 500. In the step of unloading the substrate 100 to be processed from the chamber 300, after removing the suspended particles by using an inert gas such as nitrogen, helium or argon, the substrate 100 to be processed is unloaded from the chamber 300. . In addition, in the case of using the reactive gas, the reactive gas flowing in is stopped, and the reactive gas filled in the chamber is extracted, and then the inert gas is introduced to remove floating particles, and then the substrate 100 to be treated is removed from the chamber 300. Unload The types of materials to be treated are largely divided into conductors, semiconductors, and insulators.The conductors are Al, W, Mo, Cu, Pt, Ni, Fe, etc., and the semiconductors are Si, GaAs, LiTaO ₃ , ZnO, AlN, GaN, etc. Includes all laser treatable materials such as SiO ₂ , undoped silicate glass (USG), and Si _x N _y .

The transport module 405 includes a sorter, a cassette, a cassette stage, an aligner, a cooling system, and a robot. The vacuum chamber 300 and the pumping system 304 may be equipped with a slit door, a quartz window 301, a heating system 303, a quartz focus ring, pin up down, a rotating stage, various valves and pumps for pumping. have. The conveyance stage 500 can maintain appropriate precision, can be comprised by the x-axis, y-axis, and z-axis, and can use only one axis as needed. The gas box 305 can supply the gas of all the sources which can raise the effect of processing a semiconductor substrate by a laser, and also includes an inert gas for purging. The computer control system 306 can control all parts of the device, as well as the laser generator 200, and stores recipes for various materials and processes. Recipes include, for example, laser oscillation energy, laser pulse repetition rate, attenuator angle, stage speed, laser energy density, laser pulse number, chamber atmosphere, chamber pressure, heating temperature, and reactive gas species. .

If desired, the laser energy density and the number of laser pulses are performed in the range of 50 mJ / cm ² to 1,000 mJ / cm ² , 1 to 1,000 pulses, respectively. At this time, the laser pulse period is performed within 1 ~ 1,000 Hz. The chamber atmosphere includes both atmospheric and vacuum, in which case both inert gas atmosphere and reactive gas atmosphere. In an inert atmosphere, an inert gas such as Ar or N ₂ is used, and in a reactive atmosphere, a reactive gas associated with a material such as NF ₃ , CF ₄ , O ₂ , H ₂ , Cl ₂ , N _x O _y is used. Here, the pressure of the chamber 300 is 10 ^-6 torr at atmospheric pressure, the heating temperature is preferably in the range of 500 ℃ at room temperature.

After forming the buffer layer 105 by using the manufacturing apparatus and the planarization method as described above, referring to Figures 2 and 3 again, to deposit a metal layer, such as Mo for the lower electrode on the buffer layer 105, laser planarization Since Mo is deposited on the W 102, the planarization of Mo does not need to be performed separately. Therefore, the CMP and the wet cleaning step performed on the conventional Mo can be omitted.

Subsequently, after the photoresist is coated and patterned, Mo etching is performed to form the lower electrode 110. Unlike the prior art, the used photoresist film is removed with a laser using the manufacturing apparatus as described above, and at the same time as the photoresist film is removed, the Mo lower electrode 110 is planarized. In addition, the conventional wet cleaning after the ashing to remove the photoresist film has to be separately, but the cleaning step can be omitted using the laser according to the present invention (s12). In other words, in the method of manufacturing the acoustic wave device according to the present invention, residue removal and planarization are simultaneously performed using a laser. The wavelength of the laser for removing the photoresist is advantageously a laser having a wavelength in the ultraviolet region. Thus, a KrF excimer laser of 248 nm wavelength is suitable. However, the aforementioned wavelength band of the excimer laser is also very effective for removing the photoresist film.

 In order to simplify the process by performing the cleaning and planarization at the same time in the present invention, the photoresist film remaining after the etching process is completely removed based on the etching rate obtained through experiments through a single laser scanning, and the material to planarize the surface. The planarization process may be performed by adjusting the laser energy density, the repetition rate, the number of pulses, and the like that are appropriate for the process. Laser scanning will utilize the transfer stage 500 for the entire substrate processing. Some residues that may remain without being completely removed during laser cleaning can also be removed during laser planarization through another laser scanning. Laser cleaning and planarization can be performed simultaneously with one or two scanning in a single device, which can solve the problem of shortening of the process and worsening of surface roughness in the existing method.

2 and 3, ZnO for the piezoelectric layer is deposited by RF sputtering on the lower electrode 110, and is deposited on the laser planarized lower electrode 110, so that planarization of ZnO needs to be performed separately. There is no. Therefore, the CMP and the wet cleaning step performed on the conventional ZnO can be omitted. AlN or the like may be deposited instead of ZnO. Subsequently, a photosensitive film is coated and patterned on ZnO, and then ZnO is etched to form a piezoelectric layer 115. The used photoresist film is also removed with a laser, and the photoresist film is removed and the planarization and cleaning of the piezoelectric layer 115 are performed at step S13. Here, the step of using the laser is also preferably performed using the apparatus of FIG.

Then, Mo is deposited on the metal layer for the upper electrode, the photoresist patterning and Mo etching is performed to form the upper electrode 120, and then using the laser to remove the photoresist and at the same time cleaning (s14). This step is also preferably performed using the apparatus of FIG.

Finally, the device surface is passivated (s15).

Photosensitive films used in the manufacturing process are classified into g-line, i-line, DUV, etc. according to the application device (or wavelength of the light source), and more than 70% of the composition is made of solvent. In the process of patterning the photoresist during the process, the solvent component is removed through baking, and only carbonaceous materials are present. At this time, the elements that combine with carbon vary in composition such as O, N, H, and S. Do. These elements are present in the form of single or multiple bonds with carbon, each having a binding energy of approximately 5 eV or less for single bonds and more for multiple bonds.

The wavelength of the laser proposed as applicable to the removal of the photosensitive film in the present invention is 248 nm, corresponding to 5.01 eV of energy per photon. This is enough energy to directly break a single bond between carbon and other elements, and further multi-bond energy is due to the multi-photon effect of the continuous laser beam, resulting in the decomposition of the photoresist due to vibration and thermal energy accumulated in the molecule. It is possible. The density and etch rate of the damage threshold energy of the photoresist with respect to the laser of 248 nm wavelength is shown in FIG. 5, where the triangle (-Δ-) is the etch rate and square (-□-) when the laser pulse period is 1 Hz. ) Denotes an etch rate when the laser pulse period is 10 Hz, and circles (-○-) denote an etch rate when the laser pulse period is 30 Hz. Here, it can be seen that the threshold energy density for the photosensitive film is about 30 to 50 mJ / cm ² . That is, for the removal and cleaning of the photoresist, the cleaning process must be performed above this threshold energy density. In order to improve the laser cleaning efficiency as shown in FIG. 5, it is desirable to increase the energy density and the laser pulse period, but the threshold energy density for each material exposed to the bottom and the outside should be considered. That is, the process must be performed in accordance with the material having the lowest threshold energy density among the lower and exposed materials. For example, if the threshold energy density of ZnO is 200 mJ / cm ² and the threshold energy density of W is 250 mJ / cm ^2, it means that the laser energy density applied to the cleaning process for removing the photoresist should be 200 mJ / cm ² or less. do.

6 shows a distribution of materials used for fabricating an acoustic wave device according to laser energy density and processing time. As shown in FIG. 6, it can be seen that the laser energy density application range of all materials including ZnO is larger than that of the photosensitive film. In the case of the photoresist film, it is not necessary to limit the use range of the laser energy density to 200 mJ / cm ² or less as shown in FIG. 6, and in the case of a material having a high threshold energy density such as Al or Mo, more energy is required. By applying density, laser cleaning efficiency can be maximized. However, considering the range of laser energy densities to be applied to planarization processes such as ZnO, W, Si, etc., irradiation of laser energy densities that are too high may deteriorate the surface roughness of the thin film and also affect the physical properties, resulting in crack generation and composition ratio. Undesirable consequences such as change, deterioration of crystallinity and lowering of electrical conductivity are caused.

When performing laser cleaning and planarization according to the present invention, the degree of surface roughness of each material and the result of improving the performance of the device are shown in Tables 1 and 2 below.

material RMS ZnO W (PVD) W (CVD) Al Mo Si Before treatment 75.0 32.0 15.0 55.0 12.0 1.2 After treatment 8.5 28.0 8.5 23.5 9.0 0.75 Amount of change 66.5 4.0 6.5 21.5 3.0 0.45 % Improvement 88.7 12.5 43.3 39.1 25.0 37.5

Condition Insertion loss A B C D E F G H I J Average Before treatment (dB) 1.8 2.2 2.2 1.8 1.8 1.7 1.7 2.6 1.9 3.3 After treatment (dB) 1.4 1.7 1.4 1.3 1.4 1.5 1.7 2.5 1.5 3.2 Change amount (dB) -0.4 -0.5 -0.8 -0.5 -0.4 -0.2 0 -0.1 -0.4 -0.1 -0.34 % Improvement 22.2 22.7 36.4 27.8 22.2 11.8 0 3.9 21.1 3.0 17.1

As mentioned above, although embodiment of this invention was described, this invention is not limited only to the above-mentioned embodiment, A various change and a deformation | transformation are possible. The invention includes alternatives, modifications and equivalents that may be included within the spirit and scope of the invention as defined by the appended claims.

As described above, according to the present invention, the surface roughness can be effectively improved without applying physical stress by irradiating each thin film of the acoustic wave element using a laser. Unlike conventional flattening methods, no chemicals or water are used, which can solve environmental pollution, reprocessing of various by-products such as wastewater, and installation and operation of various facilities, and the cost increase due to chemical use. In addition, by performing the cleaning process, such as removal of the photoresist, at the same time, the number of manufacturing processes can be reduced to simplify the manufacturing process, and manufacturing time and cost reduction can be expected.

In addition, the device manufacturing process proceeds in the order of deposition of the thin film-> photoresist patterning-> thin film etching-> removal and planarization of the photoresist using a laser to prevent attack of the surface of the thin film by the cleaning liquid and simplify the device manufacturing process, It can reduce device production cost and improve process efficiency.

1 is a flowchart of an acoustic wave device manufacturing process of performing surface planarization using a conventional CMP.

2 is a flowchart of a process for manufacturing an acoustic wave device using a laser according to the present invention.

3 is a cross-sectional view of an acoustic wave device according to the present invention.

4 is a schematic diagram of a device that can be used in the method for manufacturing an acoustic wave device using a laser according to the present invention.

FIG. 5 is a graph showing the density and etch rate of the damage threshold energy of the photoresist for a laser of 248 nm wavelength.

FIG. 6 is a diagram illustrating materials used for fabricating an acoustic wave device with respect to laser energy density and processing time.

* Description of the symbols for the main parts of the drawings *

100 ... substrate 101 ... SiO ₂ 102 ... W

105 buffer layer 110 lower electrode 115 piezoelectric layer

120 Top electrode 200 Laser generator 201 Optical system

300 ... vacuum chamber 301 ... quartz window 302 ... gas injection device

303 Heating system 304 Pumping system 305 Gas box

Computer control system 405 Transport module 500 Transport stage

Claims (16)

delete delete delete delete delete delete Forming a buffer layer on the substrate; Forming a lower metal layer on the buffer layer; Forming a first photoresist pattern on the lower metal layer; Forming a lower electrode by etching the lower metal layer using the first photoresist pattern as an etching mask; Simultaneously removing the first photoresist pattern and planarizing the lower electrode surface by using a laser; Forming a piezoelectric layer on the lower electrode; Forming a second photoresist pattern on the piezoelectric layer; Forming a piezoelectric layer pattern by etching the piezoelectric layer using the second photoresist pattern as an etching mask; Simultaneously removing the second photosensitive film pattern and planarizing the surface of the piezoelectric layer using a laser; Forming an upper metal layer on the piezoelectric layer; Forming a third photoresist pattern on the upper metal layer; Forming an upper electrode by etching the upper metal layer using the third photoresist pattern as an etching mask; And And removing the third photoresist pattern using a laser. According to claim 7, wherein the laser energy density and the number of laser pulses are 50 mJ / cm ² ~ 1,000 mJ / cm ² , 1 ~ 1,000, respectively, characterized in that the laser pulse period is performed within 1 ~ 1,000 Hz Method of manufacturing an acoustic wave element. The method of claim 7, wherein the laser is any one of F2 laser, ArF laser, KrF laser, XeCl laser, CO ₂ laser, Nd: YAG laser, Ar laser. The method of claim 7, wherein the pressure of the chamber performing the step using the laser is in the range of 10 ⁻⁶ torr at atmospheric pressure, and the heating temperature is in the range of 500 ° C. at room temperature. delete delete delete delete delete delete