A wet etching method for lead zirconate titanate thin films

Abstract

The present invention provides a wet etching method for lead zirconate titanate thin films. By using a first etching solution and a second etching solution, two-step etching is carried out for different components in the lead zirconate titanate thin films respectively. Each step is relatively independent, and it is easy to operate and control the etching rates of different components. While increasing the etching rate, the balance of the etching rates of different components is ensured. Among them, the use of F⁻ is completely controlled in the first etching with the first etching solution, which can minimize the side etching problem and the consumption problem of photoresist caused by F⁻ while ensuring the etching effect. This wet etching method has a high-precision pattern transfer ability, and the side etching ratio is less than 1:1, providing an effective processing method for the use of lead zirconate titanate thin films in the MEMS field. The present invention can provide lead zirconate titanate thin films with high yield and high quality, which can meet the process requirements for patterning lead zirconate titanate thin films in MEMS manufacturing. The equipment and process conditions are simple, and it is easy to expand production capacity.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor chips and manufacturing, and particularly to a wet etching method for lead zirconate titanate thin films. Background Art

[0002] Piezoelectric materials are widely used in MEMS devices, including radio frequency generators, actuators, ultrasonic motors, generators, acoustic sensors, etc. Piezoelectric materials commonly used in MEMS manufacturing processes include zinc oxide (ZnO), polyvinylidene fluoride (PVDF), aluminum nitride (AlN), aluminum scandium nitride (AlScN), and lead zirconate titanate (PZT). Among them, PZT has attracted much attention in MEMS devices due to its excellent piezoelectric coefficient and electromechanical coupling performance. In the process of device fabrication, the micropatterning of the PZT film layer is an important process that cannot be bypassed and is also one of the key technologies restricting its widespread development.

[0003] Common methods for PZT micropatterning include dry etching and wet etching, which are specifically as follows:

[0004] Due to its anisotropic characteristics, dry etching can ensure good pattern conversion accuracy, but the equipment is expensive and the etching rate is low. Among them, common dry etching methods include IBE (ion beam etching) and RIE (reactive ion etching). IBE etching of PZT uses an ion beam to bombard the material after acceleration to achieve the etching effect. Although this method has high patterning accuracy, its selectivity to metal bottom electrodes (such as platinum Pt, molybdenum Mo, gold Au, silver Ag, etc.) is very poor, and it cannot ensure that the PZT thin film is etched clean while the bottom electrode is not consumed. In addition, IBE etching is often accompanied by problems such as photoresist carbonization, which all lead to the fact that this method is not an ideal PZT etching method. RIE etching is a method that uses chemical and physical reactions to remove the material on the substrate surface. It is an etching process that can produce directional etching. However, since the PZT thin film is a multi-component compound, it is very difficult to master the balance of the etching process using RIE dry etching. There is a large etching rate difference for different components of PZT to the same etching gas. Therefore, a combination of multiple etching gases is required, resulting in very complex process development, high difficulty in daily maintenance, strong influence of equipment state fluctuations, and easy generation of residual and over-etching problems due to different etching rates of different components. In addition, the low dry etching rate and the difficulty in treating sidewall products also limit its application in PZT micropatterning.

[0005] In comparison, wet etching has excellent etching selectivity and etching rate, and has low requirements for equipment, making it suitable for process expansion in semiconductor fabrication plants (FABs). Since wet etching is isotropic etching, there is a significant lack of pattern conversion accuracy compared to dry etching. PZT can be simply understood as a composite material composed of PbO, TiO2, and ZrO2, and is often combined with upper and lower electrodes. Since dry etching has a poor selectivity ratio for the upper and lower electrode materials, wet etching is more suitable for patterning. However, since PZT is a multi-component composite material, the etching rates of different components are different in the same etching solution, and residues are likely to occur due to unbalanced etching of each component. Therefore, the currently commonly used wet etching method for PZT is composite acid etching to deal with different phase structures in the PZT composite material. In previous studies, people have tried to prepare composite acids by combining hydrochloric acid (HCl), hydrofluoric acid (HF), phosphoric acid (H3PO4), and nitric acid (HNO3), etc. These solutions all have an etching effect on the PZT thin film, but the etching rates of phosphoric acid and nitric acid are low, which will lead to long-term etching and serious side etching phenomena; the etching rate differences of hydrochloric acid and hydrofluoric acid for different components are large, and etching residues are likely to occur. Therefore, the ratio of the composite acid and relatively stable reaction conditions are the main directions for the development of wet etching procedures.

[0006] In summary, although dry etching has relatively high pattern conversion accuracy, it has a poor selectivity ratio for the bottom electrode, low etching rate, complex process, high equipment cost, and low processing efficiency; traditional wet etching has excellent etching rate and selectivity ratio, but poor pattern transfer accuracy. In addition, considering the characteristics of PZT multi-components, the etching solution usually selects a mixture of multiple acids, which brings problems such as complex solution ratio, serious side etching, low rate, and easy residue.

[0007] Therefore, there is an urgent need to develop a wet etching method for PZT thin films with low side etching, high efficiency, good etching effect, and good popularization. Summary of the Invention

[0008] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a wet etching method for lead zirconate titanate thin films to solve the above series of problems encountered in the etching of PZT thin films in the prior art.

[0009] To achieve the above purpose and other related purposes, the present invention provides a wet etching method for lead zirconate titanate thin films, and the wet etching method for lead zirconate titanate thin films at least uses a first etching solution and a second etching solution to sequentially etch the lead zirconate titanate thin film step by step, wherein the first etching solution contains F - and NO3 -The first etchant is an acidic solution, and the second etchant is an acidic solution containing Cl⁻. The zirconia phase and titania phase are selectively etched by the first etchant to break some Pb - O bonds, and the remaining Pb - O bonds are etched by the second etchant.

[0010] Optionally, the concentration of F in the first etchant - ranges from 0.5% to 10%; the concentration of NO₃ in the first etchant - ranges from 0.5% to 11%.

[0011] Optionally, the concentration of Cl in the second etchant - ranges from 20% to 40%.

[0012] Optionally, the first etchant includes NH₄F.

[0013] Optionally, the sample of the lead zirconate titanate thin film to be etched includes a cutoff layer located below the lead zirconate titanate thin film. The cutoff layer includes one or a combination of a metal electrode layer, a silicon layer, and a silicon nitride layer. Among them, the material of the metal electrode layer includes one or a combination of platinum, molybdenum, gold, and silver.

[0014] Optionally, the wet etching method of the lead zirconate titanate thin film is carried out at room temperature.

[0015] Optionally, the sidewall tilt angle of the lead zirconate titanate thin film after etching is 30° - 40°, and the sidewall tilt angle of the lead zirconate titanate thin film after etching is changed by changing the concentration of NO₃ - .

[0016] Optionally, the side etching ratio of the lead zirconate titanate thin film is less than 1:1.

[0017] Optionally, the wet etching method of the lead zirconate titanate thin film includes the following steps:

[0018] S1. Provide a lead zirconate titanate sample to be etched that has completed lithography, and perform a first etching in the first etchant until the titania phase and zirconia phase in the lead zirconate titanate thin film are completely etched;

[0019] S2. Quickly rinse the lead zirconate titanate sample that has completed step S1 with a cleaning solution until the products and residual acid solution etched in step S1 are removed, and then spin - dry;

[0020] S3. Perform a second etching on the lead zirconate titanate sample that has completed step S2 in the second etchant until the lower electrode layer in the lead zirconate titanate sample is completely exposed;

[0021] S4. Quickly rinse the lead zirconate titanate sample that has completed step S3 with a cleaning solution to remove the residual acid solution on the surface, and then spin - dry;

[0022] S5. Remove the photoresist layer.

[0023] Optionally, the cleaning solution in step S2 and step S4 includes deionized water; the rinsing methods in step S2 and step S4 include one or a combination of flushing, wafer brushing, or ultrasonic cleaning; the method for removing the photoresist layer in step S5 includes one or a combination of acetone ultrasonic cleaning, organic photoresist stripping, and dry photoresist stripping.

[0024] The wet etching method for lead zirconate titanate thin films of the present invention uses a first etching solution and a second etching solution to perform two-step etching on different components in the lead zirconate titanate thin film, which significantly expands the required range of the concentration ratio of the mixed acid. Each step is relatively independent, and it is easy to operate and control the etching rates of different components. While increasing the etching rate, it ensures the balance of the etching rates of different components. Among them, the use of F- is completely controlled in the first etching with the first etching solution, which minimizes the side etching problem and the consumption problem of the photoresist caused by F while ensuring the etching effect. - This wet etching method has a high-precision pattern transfer ability, and the side etching ratio is less than 1:1, providing an effective processing method for the use of lead zirconate titanate thin films in the MEMS field.

[0025] The present invention has the following beneficial effects: 1) High pattern accuracy for lead zirconate titanate thin films, with a side etching ratio less than 1:1 and a sidewall tilt angle of up to about 35°; 2) No special requirements for equipment, no need to modify the equipment, and the extended use cost is low; 3) The etching rate is extremely fast, and the average rate of the two-step etching can reach about 4 μm / min. This rate varies for lead zirconate titanate materials with different compositions and can be even faster; 4) The etching solution has an excellent selectivity ratio for traditional photoresists and stop layers, and the etching process will not damage the film layers on the upper and lower surfaces of the lead zirconate titanate thin film; 5) The etching rates of different components of lead zirconate titanate are easy to control during the step-by-step etching, and no residue problem will occur during etching; 6) It is carried out at room temperature, both etching solutions are at room temperature, and both manual operation and automated operation are applicable, and no problems such as stress caused by the thermal process will occur.

[0026] Therefore, the present invention can provide high-yield and high-quality patterned lead zirconate titanate thin films, which can meet the process requirements for patterning lead zirconate titanate thin films in MEMS manufacturing. The equipment and process conditions are simple, and it is easy to expand production capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It shows a schematic process flow diagram of wet etching of lead zirconate titanate thin films in an embodiment of the present invention.

[0028] Figure 2a It shows a schematic structural diagram of a lead zirconate titanate sample to be etched after lithography in an embodiment of the present invention.

[0029] Figure 2b It shows a schematic diagram of the structure after the first etching in the embodiment of the present invention.

[0030] Figure 2c It shows a schematic diagram of the structure after rinsing is completed in the embodiment of the present invention.

[0031] Figure 2d It shows a schematic diagram of the structure after the second etching in the embodiment of the present invention.

[0032] Figure 2e It shows a schematic diagram of the structure after the photoresist layer is removed in the embodiment of the present invention.

[0033] Figure 3a It shows a light microscope image after the first etching and before rinsing in the first embodiment of the present invention.

[0034] Figure 3b It shows a light microscope image after the first etching and rinsing in the first embodiment of the present invention.

[0035] Figure 4 It shows a cross-sectional SEM image after etching and before photoresist removal in the second embodiment of the present invention.

[0036] Figure 5 It shows a cross-sectional SEM image after etching and before photoresist removal in the third embodiment of the present invention.

[0037] Element number description

[0038] 101 Substrate layer

[0039] 102 Lower electrode layer

[0040] 103 PZT layer

[0041] 200 Photoresist layer

[0042] 113 PZT first etching residual product

[0043] 123 Remaining substance after PZT rinsing

[0044] Steps S1 to S5 Specific implementation manners

[0045] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0046] When describing the embodiments of the present invention in detail, for the convenience of description, the cross-sectional views showing the device structure may be enlarged locally in a non-general proportion, and the schematic diagrams are only examples and should not limit the scope of protection of the present invention herein. In addition, in actual production, three-dimensional spatial dimensions of length, width and depth should be included.

[0047] For the convenience of description, spatial relationship terms such as "under", "below", "lower than", "beneath", "above", "on" etc. may be used herein to describe the relationship between one element or feature shown in the drawings and other elements or features. It will be understood that these spatial relationship terms are intended to encompass other directions of the device in use or operation, in addition to the directions depicted in the drawings. Further, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or there can be one or more intervening layers. Herein, when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0048] Terms such as "between... and" may be used herein, which expression means including the endpoint values, and terms such as "a plurality of" may be used, which expression means two or more, unless otherwise specifically defined. In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0049] It should be noted that the diagrams provided in this embodiment only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape and size of the components in actual implementation. The types, numbers and proportions of the components in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0050] This embodiment provides a wet etching method for a lead zirconate titanate thin film. Among them, the wet etching method for the lead zirconate titanate thin film at least uses a first etching solution and a second etching solution to sequentially perform step-by-step etching on the lead zirconate titanate thin film. Among them, the first etching solution is an acidic solution containing F - and NO3 - The second etching solution is an acidic solution containing Cl - By using the first etching solution, the zirconia phase and the titania phase are selectively etched and part of the Pb-O bonds are opened, and the remaining Pb-O bonds are etched by the second etching solution.

[0051] Specifically, since the lead zirconate titanate (PZT) thin film is composed of multiple components, various acid concentration consumptions and influences will inevitably occur when using the commonly used mixed acid etching solutions in the prior art. In this embodiment, a step-by-step wet etching method is proposed to pattern the PZT thin film, so as to accurately control the reaction ion concentration of the etching solution at different etching stages, avoid the concentration consumption between components caused by excessive mixed acid components, significantly improve the wet etching rate, achieve high-speed and uniform etching, and contribute to improving the pattern transfer accuracy.

[0052] Among them, two etching solutions are used in this embodiment. The first etching solution is a solution containing F with extremely strong undercutting properties, - which can effectively and selectively etch zirconium oxide (ZrO2) and titanium oxide (TiO2), and cooperate with NO 3- in an acidic environment to break the Pb-O bond and ensure the continuous progress of the reaction. Among them, ZrO2 dissolves in HF, TiO2 + 4HF == H2[TiOF4] + H2O, PbO + 2HNO3 == Pb(NO3)2 + H2O, and the remaining structure after the reaction is loose, which is conducive to the timely discharge of the first etching residue 113 of PZT, such as Figure 2b and Figure 2c , ensuring that the etching has a certain longitudinal undercutting property. The second etching solution is for the PbO phase in the remaining PZT thin film, that is, the residue 123 remaining after PZT rinsing, such as Figure 2c , and a diluted concentrated hydrochloric acid solution is selected to provide an acidic solution containing Cl - . PbO + 2HCl == PbCl2 + H2O, and the etching rate is high, which can greatly reduce the loss of image conversion. In addition, the first etching solution and the second etching solution also have the characteristics generally possessed by conventional wet etching solutions, such as high selectivity ratio to photoresist, large batch processing, low cost, low pollution, and suitability for industrial production.

[0053] As an example, the concentration range of F - in the first etching solution is 0.5% to 10%, such as 0.5%, 1%, 5%, 10%, etc.; the concentration range of NO3 - in the first etching solution is 0.5% to 11%, such as 0.5%, 1%, 5%, 10%, 11%, etc.; the selection of the first etching solution can be configured according to specific needs, and the ratio of F - and NO3 - is not overly restricted here.

[0054] As an example, the first etching solution can be an F-supplementary source containing an inhibitor, such as NH4F.

[0055] As an example, the concentration range of Cl - in the second etching solution is 20% to 40%.

[0056] Specifically, the second etchant does not contain F - , wherein the Cl in the second etchant - The concentration range can be 20%, 30%, 40%, etc., and can be specifically selected according to needs, and there is no excessive limitation here.

[0057] As an example, the sample of the PZT thin film to be etched includes a stop layer located below the PZT thin film. The stop layer can include one or a combination of a metal electrode layer, a silicon layer, and a silicon nitride layer. Among them, the material of the metal electrode layer can include one or a combination of platinum (Pt), molybdenum (Mo), gold (Au), and silver (Ag).

[0058] Specifically, during wet etching, by different selection etching ratios between materials, the wet etching process can be controlled. In this embodiment, the metal electrode layer is preferably used as the stop layer located below the PZT thin film. Thus, the metal electrode layer can be used as the stop layer and can also be directly used as the subsequent lower electrode layer, thereby reducing process steps. However, the selection of the stop layer is not limited to this. According to needs, other materials such as a silicon layer and a silicon nitride layer can also be used as the stop layer, and there is no excessive limitation here.

[0059] As an example, the wet etching method of the PZT thin film can be carried out at room temperature, but it is not limited to this. It can also be carried out in other temperature ranges, but there will be certain differences in the rate and effect.

[0060] As an example, the sidewall inclination angle of the PZT thin film after etching is 30° - 40°, such as 30°, 35°, 40°, etc., and by changing the concentration of the NO3 - , the sidewall inclination angle of the PZT thin film after etching can be changed. For example, the concentration of the NO3 in the first etchant can be reduced - to obtain a more vertical sidewall, but at the same time, the risk of residue after etching will increase.

[0061] As an example, the side etch (lateral etch amount / longitudinal etch amount) ratio of the PZT thin film is less than 1:1, such as 0.8:1, 0.5:1, etc.

[0062] As an example, referring to Figure 1 , the wet etching method of the PZT thin film may include the following steps:

[0063] S1. Provide a lead zirconate titanate sample to be etched that has completed photolithography, and perform a first etching in the first etchant until the titanium oxide phase and zirconium oxide phase in the lead zirconate titanate thin film are etched clean;

[0064] S2. Quickly rinse the lead zirconate titanate sample that has completed step S1 with a cleaning solution until the etching products and residual acid solution in step S1 are removed, and then spin-dry it.

[0065] S3. Perform a second etching on the lead zirconate titanate sample that has completed step S2 in the second etching solution until the lower electrode layer in the lead zirconate titanate sample is completely exposed.

[0066] S4. Quickly rinse the lead zirconate titanate sample that has completed step S3 with a cleaning solution to remove the residual acid solution on the surface, and then spin-dry it.

[0067] S5. Remove the photoresist layer.

[0068] Refer to Figures 2a to 2e Schematically shows the main structural diagram during the wet etching of the PZT thin film, specifically including:

[0069] First, perform step S1. The first etching solution and the second etching solution can be respectively prepared according to the characteristics of the etching solution, and a PZT sample to be etched that has completed photolithography is provided, such as Figure 2a .

[0070] In this embodiment, the structure of the PZT sample includes a base layer 101, a lower electrode layer 102, and a PZT layer 103 stacked from bottom to top, and the surface of the PZT layer 103 has a photoresist layer 200 that has completed photolithography. Among them, regarding the specific composition and thickness of the PZT layer 103, it affects the specific etching solution ratio and etching time, and no excessive restrictions are imposed here. In this embodiment, the PZT layer 103 adopts the relatively common Pb(Zr 0.52 Ti 0.48 )O x type, but the type of the PZT layer 103 is not limited to this. The lower electrode layer 102 includes but is not limited to platinum (Pt), molybdenum (Mo), gold (Au), silver (Ag), and the base layer 101 can be a silicon layer to provide support, but the structure and material of the PZT sample are not limited to this. The PZT sample needs to be coated with a mask and patterned for wet etching. Among them, the material of the mask can use a common photoresist (PR). Since the subsequent wet etching solution has an excellent selectivity for the photoresist, it is recommended to perform a bottom film treatment after photolithography.

[0071] Next, refer to Figure 2b , place the PZT sample that has completed photolithography in the first etching solution for the first etching until the titanium dioxide (TiO2) phase and zirconium dioxide (ZrO2) phase in the PZT layer 103 are etched clean. When performing the etching, there are no special equipment requirements, and a common wet acid tank can be used, which can be operated automatically or manually.

[0072] Next, perform step S2, refer to Figure 2b and 2c , quickly rinse the PZT sample that has completed step S1 with a cleaning solution until the etching products and residual acid solution in step S1 are removed, and then spin-dry.

[0073] Specifically, when performing this rinsing step, equipment with a certain physical cleaning ability, such as an ultrasonic or a water-flushing brush machine, etc., also needs to be prepared for sample rinsing. Among them, the rinsing method can include one or a combination of water flushing, brush coating, or ultrasonic cleaning, and there is no excessive limitation here. After performing the first etching, using a physical cleaning device to clean the PZT sample can assist in removing the first etching residual product 113 and expose the remaining product 123 after PZT rinsing. Among them, it should be noted that the cleaning solution should not be reactive with the mask, that is, the photoresist layer 200.

[0074] Next, perform step S3, refer to Figure 2d , perform a second etching on the PZT sample that has completed step S2 in the second etching solution until the lower electrode layer 102 in the PZT sample is completely exposed.

[0075] Next, perform step S4, quickly rinse the PZT sample that has completed step S3 with a cleaning solution to remove the residual acid solution on the surface, and then spin-dry.

[0076] Specifically, this rinsing step can refer to step S2, which will not be elaborated here. Among them, performing the rinsing operation after each etching step can avoid unnecessary pattern transfer losses to achieve high-precision pattern transfer.

[0077] Next, perform step S5, refer to Figure 2e , remove the photoresist layer 200.

[0078] Specifically, the method for removing the photoresist layer 200 can include one or a combination of acetone ultrasonic cleaning, organic degumming, and dry degumming, and can be specifically selected according to needs, and there is no excessive limitation here.

[0079] The following further introduces the present application in combination with specific implementation manners:

[0080] Example 1

[0081] Perform two-step wet etching on the PZT sample in Figure 2a . Among them, for the first etching solution, use 9 ml of HNO3 + 15 ml of BHF + 180 ml of DI, and the first etching time is 15 s. After etching, observe the PZT sample under an optical microscope, as shown in Figure 2aAs shown; then rinse with deionized water for 2 min and spin dry. After completion, observe the PZT sample under an optical microscope, as Figure 2b shown.

[0082] Example 2

[0083] For the Figure 2a PZT sample in, perform two-step wet etching. Among them, the first etching solution uses 9 ml of HNO3 + 15 ml of BHF + 180 ml of DI for the first etching, and the first etching time is 15 s; then rinse with deionized water for 2 min and spin dry; then use the second etching solution of 20 ml of concentrated HCl + 80 ml of DI for the second etching, and the second etching time is 8 s until the lower electrode layer 102 is completely exposed. After flushing, cleaning, and spin drying, the SEM image of the un-deglued cross-section is as Figure 4 shown, and the CD loss is 2.39 μm.

[0084] Example 3

[0085] For the Figure 2a PZT sample in, perform two-step wet etching. Among them, the first etching solution uses 6 ml of HNO3 + 10 ml of BHF + 140 ml of DI for the first etching, and the first etching time is 10 s; then rinse with deionized water for 2 min and spin dry; then use the second etching solution of 30 ml of concentrated HCl + 70 ml of DI for the second etching, and the second etching time is 15 s until the lower electrode layer 102 is completely exposed. After flushing, cleaning, and spin drying, the SEM image of the un-deglued cross-section is as Figure 5 shown, and the CD loss is 0.78 μm.

[0086] In summary, for the wet etching method of lead zirconate titanate thin films according to the present invention, a first etching solution and a second etching solution are used to perform two-step etching on different components in the lead zirconate titanate thin film respectively. The requirement for the concentration ratio range of the mixed acid is significantly expanded. Each step is relatively independent, and it is easy to operate and control the etching rates of different components. While increasing the etching rate, the balance of the etching rates of different components is ensured. Among them, the use of F- is completely controlled in the first etching with the first etching solution, which can minimize the side etching problem and the consumption problem of photoresist caused by F- while ensuring the etching effect. This wet etching method has high-precision pattern transfer ability, and the side etching ratio is less than 1:1, providing an effective processing method for the use of lead zirconate titanate thin films in the MEMS field. The present invention can achieve the following: 1) High patterning accuracy for lead zirconate titanate thin films, with a side etching ratio less than 1:1 and a sidewall tilt angle of about 35°; 2) No special requirements for equipment, no need for equipment modification, etc., and the extended use cost is low; 3) The etching rate is extremely fast, and the average rate of the two-step etching can reach about 4 μm / min. This rate varies for lead zirconate titanate materials with different compositions and can be even faster; 4) The etching solution has an excellent selectivity ratio for traditional photoresist and the stop layer, and the etching process will not damage the film layers on the upper and lower surfaces of the lead zirconate titanate thin film; 5) The etching rates of different components of lead zirconate titanate in the step-by-step etching are easy to control, and no residue problem will occur during etching; 6) It is carried out at room temperature, both etching solutions are at room temperature, and both manual operation and automated operation are applicable, and no problems such as stress caused by thermal processes will occur.

[0087] Therefore, the present invention can provide lead zirconate titanate thin films with high yield and high quality, which can meet the process requirements for patterning lead zirconate titanate thin films in MEMS manufacturing. The equipment and process conditions are simple, and it is easy to expand production capacity.

[0088] The above embodiments are only used to illustrate the principle and its effects of the present invention, rather than to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A wet etching method for lead zirconate titanate thin films, characterized in that: The wet etching method of the lead zirconate titanate thin film at least uses a first etching solution and a second etching solution to sequentially etch the lead zirconate titanate thin film step by step. Among them, the first etching solution is an acidic solution containing F - and NO3 - , and the second etching solution is an acidic solution containing Cl - . The concentration range of Cl - in the second etching solution is 20% - 40%. The zirconia phase and the titania phase are selectively etched by the first etching solution to open some Pb - O bonds, and the remaining Pb - O bonds are etched by the second etching solution.

2. The wet etching method of lead zirconate titanate thin film according to claim 1, wherein: The F in the first etching solution - has a concentration range of 0.5% to 10%; the NO3 in the first etching solution - has a concentration range of 0.5% to 11%.

3. The wet etching method of lead zirconate titanate thin film according to claim 1, characterized in that: The first etchant includes NH4F.

4. The wet etching method of lead zirconate titanate thin film according to claim 1, characterized in that: The sample of the lead zirconate titanate thin film to be etched includes a cutoff layer located under the lead zirconate titanate thin film. The cutoff layer includes one or a combination of a metal electrode layer, a silicon layer, and a silicon nitride layer. Among them, the material of the metal electrode layer includes one or a combination of platinum, molybdenum, gold, and silver.

5. The wet etching method of lead zirconate titanate thin film according to claim 1, characterized in that: The wet etching method of the lead zirconate titanate thin film is carried out at room temperature.

6. The wet etching method of lead zirconate titanate thin film according to claim 1, wherein: The inclined angle of the sidewall of the lead zirconate titanate thin film after etching is 30° to 40°, and the inclined angle of the sidewall of the lead zirconate titanate thin film after etching is changed by changing the concentration of the NO3 - .

7. The wet etching method of lead zirconate titanate thin film according to claim 1, characterized in that: The side etching ratio of the lead zirconate titanate thin film is less than 1:

1.

8. The wet etching method of lead zirconate titanate thin film according to claim 1, characterized in that, The wet etching method of the lead zirconate titanate thin film includes the following steps: S1. Provide a lead zirconate titanate sample to be etched that has completed photolithography, and perform a first etching in the first etchant until the titanium oxide phase and zirconium oxide phase in the lead zirconate titanate thin film are completely etched away. S2. Quickly rinse the lead zirconate titanate sample that has completed step S1 with a cleaning solution until the products etched in step S1 and the residual acid solution are removed, and then spin dry. S3. Perform a second etching on the lead zirconate titanate sample that has completed step S2 in the second etchant until the lower electrode layer in the lead zirconate titanate sample is completely exposed. S4. Quickly rinse the lead zirconate titanate sample that has completed step S3 with a cleaning solution to remove the residual acid solution on the surface, and then spin dry. S5. Remove the photoresist layer.

9. The wet etching method of lead zirconate titanate thin film according to claim 8, characterized in that: The cleaning solution in steps S2 and S4 includes deionized water; the rinsing methods in steps S2 and S4 include one or a combination of flushing, wafer scrubbing, or ultrasonic cleaning; the method of removing the photoresist layer in step S5 includes one or a combination of acetone ultrasonic cleaning, organic resist stripping, and dry resist stripping.

Images