Piezoelectric micro-electro-mechanical device and preparation method thereof
The polymer redeposition effect is solved by using a cycle process combining dry etching and alkaline wet cleaning during the etching process of piezoelectric MEMS devices, combined with the patterned hard mask layer and the self-developed DEKC solution. The problem of abnormal morphology has achieved the integrity of the device morphology and structure and efficient etching effect.
Patent Information
- Application Number
- CN202411539717.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-31
- Publication Date
- 2025-02-11
AI Technical Summary
During the etching process of piezoelectric MEMS devices, the polymer redeposition effect leads to abnormal product morphology. The existing dry glue removal process is difficult to completely remove polymers containing metal ions, resulting in cost loss.
Using a cyclic process combining dry etching and alkaline wet cleaning, the pattern dislocation and morphology abnormalities caused by the photoresist mask during the cyclic etching and wet process are avoided. Problem, the self-developed DEKC solution is used for alkaline wet cleaning to reduce corrosion on the piezoelectric film layer.
It effectively solves the problem of polymer redeposition during piezoelectric film etching, ensures the integrity of the device morphology and structure, avoids cost losses, and improves the selectivity and uniformity of the etching process.
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Figure CN119409138A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of semiconductor technology, and in particular to a piezoelectric micro-electromechanical device and a method for preparing the same. Background Art
[0002] Piezoelectric MEMS (Micro-Electro-Mechanical System) devices are devices that use aluminum nitride AlN or aluminum scandium nitride AlScN as the building material and can realize the mutual conversion between electrical signals and mechanical vibrations. With the rapid development in recent years, piezoelectric MEMS has gradually been used in fields such as automobiles, electronics, industry, and medical equipment. Piezoelectric MEMS can be made into a variety of devices such as transducers, accelerometers, energy harvesters, and microphones, which adds convenience to all aspects of our lives. At the same time, due to the increase in its market demand and application volume, it has also promoted the research boom of piezoelectric MEMS.
[0003] Piezoelectric thin film materials such as Al N and Al ScN will form relatively serious polymers during the dry etching process. When etching a trench structure, a "redeposition effect" will occur due to the gradual increase in etching depth. There will be many reaction products during the etching process, and some of the reaction products that are difficult to remove are called polymers. In some etching processes, polymers will adhere to the side walls and surfaces and redeposit, so the phenomenon of redeposition during this etching process is called the "redeposition effect." Among them, the redeposited polymer layer is called the redeposition layer. The redeposition layer will reduce the selectivity, uniformity and etching rate of the etching process, which will lead to the phenomenon of incomplete or incomplete etching, resulting in abnormal morphology.
[0004] For the removal of polymers, dry stripping process is generally used. Dry stripping process uses plasma technology to remove residues (including polymers and photoresists, etc.) through chemical reactions and physical bombardment. However, when facing complex polymers containing metal ions, dry stripping process has great limitations, because the types of gases that can be used in dry stripping equipment are generally only O2, N2, CF4 and H20, etc. The chemical reactions that can occur cannot completely decompose such polymers, and there will still be a lot of residues.
[0005] Based on the above reasons, there is no good solution for the abnormal product morphology caused by the "redeposition effect" during the etching process of Al N or Al ScN, which causes a lot of cost losses in the manufacturing process. Summary of the invention
[0006] The purpose of the embodiments of the present application is to provide a piezoelectric micro-electromechanical device and a method for preparing the same, which can solve the problem of polymer redeposition during the etching process of the piezoelectric film layer and ensure the morphology and integrity of the device.
[0007] In one aspect of an embodiment of the present application, a piezoelectric micro-electromechanical device is provided, comprising providing a base layer, and sequentially forming at least a metal electrode layer, a piezoelectric film layer and a patterned hard mask layer on the base layer, wherein the patterned hard mask layer partially covers the piezoelectric film layer; wherein the material of the metal electrode layer does not react with an alkaline cleaning solution used in alkaline wet cleaning, and does not react with a removal solution of the patterned hard mask layer;
[0008] dry etching the area outside the patterned hard mask layer on the piezoelectric film layer to form a groove on the piezoelectric film layer;
[0009] alkaline wet cleaning of the trench to remove residual polymer generated by etching;
[0010] When the metal electrode layer is not exposed, dry etching and alkaline wet cleaning of the groove again until the piezoelectric film layer forms a target morphology and the metal electrode layer is exposed;
[0011] The patterned hard mask layer is removed.
[0012] Optionally, providing a base layer, and sequentially forming at least a metal electrode layer, a piezoelectric film layer and a patterned hard mask layer on the base layer, wherein the patterned hard mask layer partially covers the piezoelectric film layer; wherein the material of the metal electrode layer does not react with an alkaline cleaning solution used in alkaline wet cleaning, and does not react with a removal solution of the patterned hard mask layer, comprises:
[0013] Depositing the metal electrode layer with a thickness of 10nm to 1um on the base layer, wherein the material of the metal electrode layer includes at least molybdenum and ruthenium;
[0014] Depositing the piezoelectric film layer with a thickness of 0.1 um to 2 um on the metal electrode layer, wherein the material of the piezoelectric film layer at least includes aluminum nitride or aluminum scandium nitride;
[0015] The patterned hard mask layer is prepared on the piezoelectric film layer.
[0016] Optionally, the step of preparing the patterned hard mask layer on the piezoelectric film layer comprises:
[0017] The material of the patterned hard mask layer basically does not react with the etching gas of the material of the piezoelectric film layer and the alkaline cleaning solution; and the etching gas of the patterned hard mask layer basically does not react with the material of the piezoelectric film layer; and the removal solution of the patterned hard mask layer basically does not react with the materials of the piezoelectric film layer and the metal electrode layer.
[0018] Optionally, the alkaline wet cleaning of the trench to remove the residual polymer generated by etching comprises:
[0019] removing the polymer using a diluted DEKC solution;
[0020] Cleaning the groove by alcohol or ketone solution;
[0021] Cleaning the groove with deionized water;
[0022] The grooves are dried.
[0023] Optionally, the removing the polymer using a diluted DEKC solution comprises:
[0024] Diluting the EKC solution to obtain a diluted DEKC solution; wherein the EKC solution is diluted with water so that the water concentration in the DEKC solution is 30% to 45%; or the EKC solution is diluted with methanol so that the methanol concentration in the DEKC solution is 5% to 30%;
[0025] The polymer in the trench is removed using the DEKC solution.
[0026] Optionally, the alkaline wet cleaning of the trench to remove the residual polymer generated by etching comprises:
[0027] At a temperature of 30° C. to 90° C., reacting the diluted DEKC solution with the polymer for 3 to 30 minutes;
[0028] At a temperature of 10° C. to 40° C., the groove is cleaned with an alcohol or ketone solution for 1 minute to 30 minutes;
[0029] At a temperature of 10° C. to 40° C., the groove is cleaned with deionized water for 1 minute to 30 minutes;
[0030] The groove is dried at a temperature of 20° C. to 80° C. for 1 minute to 45 minutes.
[0031] Optionally, removing the patterned hard mask layer includes:
[0032] The patterned hard mask layer removal solution is used to react with the patterned hard mask layer at a temperature of 20° C. to 40° C. for 1 minute to 20 minutes; wherein the patterned hard mask layer removal solution reacts with the material of the patterned hard mask layer and does not react with the materials of the piezoelectric film layer and the metal electrode layer;
[0033] Use deionized water at a temperature of 10°C to 40°C for 1 minute to 30 minutes;
[0034] Dry at 20°C to 80°C for 1 minute to 45 minutes.
[0035] On the other hand, the present application provides a piezoelectric micro-electromechanical device, which is prepared according to the above-mentioned method for preparing a piezoelectric micro-electromechanical device, and includes a base layer, a metal electrode layer and a piezoelectric film layer stacked in sequence, wherein the piezoelectric film layer is formed with a groove, and the groove extends to the metal electrode layer and exposes the metal electrode layer.
[0036] Optionally, the material of the piezoelectric film layer includes at least aluminum nitride or aluminum scandium nitride.
[0037] Optionally, a functional film layer is also provided on the piezoelectric film layer.
[0038] The piezoelectric MEMS device and its preparation method provided in the embodiment of the present application adopt a cyclic operation method combining dry etching and alkaline wet process, which effectively solves the problem that the groove morphology cannot be completed in one step due to the "redeposition effect" during the process of etching the groove of the piezoelectric film material, and the problem that the polymer is difficult to remove, and finally realizes the groove etching of the piezoelectric film layer. The graphic hard mask solves the new problems of morphological deformation and abnormality under the repeated etching and cleaning process flow, and avoids the problem that the use of photoresist mask will cause graphic misalignment and overlap during cyclic etching and wet process, which eventually leads to morphological and CD abnormalities, and has extremely high protection for graphic morphology and CD. The wet cleaning process uses the self-developed DEKC solution to minimize the damage of the alkaline cleaning solution to the piezoelectric film layer and protect the integrity of the structural morphology. BRIEF DESCRIPTION OF THE DRAWINGS
[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.
[0040] Figure 1 is a flow chart for preparing a piezoelectric micro-electromechanical device provided in this embodiment;
[0041] Figure 2 to Figure 6 is a diagram of the preparation process of the piezoelectric micro-electromechanical device provided in this embodiment;
[0042] Figure 7 This is one of the schematic diagrams of the structure of the piezoelectric micro-electromechanical device provided in this embodiment;
[0043] Figure 8 This is the second structural schematic diagram of the piezoelectric micro-electromechanical device provided in this embodiment.
[0044] Icon: 100-base layer; 110-metal electrode layer; 120-piezoelectric film layer; 130-patterned hard mask layer; 140, 141-grooves; 150-polymer; 160-functional film layer; D-stacking direction. DETAILED DESCRIPTION
[0045] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.
[0046] In the description of this application, it should be noted that the terms "inside", "outside", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the application is usually placed when in use, which is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.
[0047] It should also be noted that, unless otherwise clearly specified and limited, the terms "disposed" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.
[0048] Please refer to Figure 1 As shown, the present invention provides a method for preparing a piezoelectric micro-electromechanical device, which can be prepared Figure 7 The piezoelectric micro-electromechanical device shown, the method comprising:
[0049] like Figure 2 As shown, step 200 : providing a base layer 100 , and sequentially forming at least a metal electrode layer 110 , a piezoelectric film layer 120 , and a patterned hard mask layer 130 on the base layer 100 , wherein the patterned hard mask layer 130 partially covers the piezoelectric film layer 120 .
[0050] The material of the metal electrode layer 110 does not react with the alkaline cleaning solution used in the alkaline wet cleaning, and does not react with the removal solution of the patterned hard mask layer. The alkaline cleaning solution is generally alkaline, and the removal solution can be an acidic solution, specifically using BOE (Buffered Oxi de Etch, buffered oxide etchant) and HF (hydrofluoric acid) two acid solutions.
[0051] The base layer 100 may be a single-layer substrate, or may be other functional film layers on the substrate including the substrate, which is not limited in the present application.
[0052] After the base layer 100 is obtained, a metal electrode layer 110 with a thickness of 10 nm to 1 um is deposited on the base layer 100. The thickness is the dimension in the stacking direction D.
[0053] Among them, the material of the metal electrode layer 110 should be selected to be a metal that is not easy or does not react with the alkaline cleaning solution used in alkaline wet cleaning, and does not react with the removal solution of the patterned hard mask layer. This is to ensure that when an alkaline cleaning solution is used to remove the piezoelectric film layer 120 to form a groove 140 in the subsequent steps, and when BOE or a diluted hydrofluoric acid solution is used to remove the patterned hard mask layer 130, the alkaline cleaning solution and BOE, hydrofluoric acid solution do not corrode the metal electrode layer 110, so that the metal electrode layer 110 can remain intact; in some embodiments, the material of the metal electrode layer 110 may include metals such as molybdenum (Mo) and ruthenium (Ru).
[0054] Deposition may be by magnetron sputtering deposition, atomic layer deposition, chemical vapor deposition, laser pulse deposition or the like.
[0055] In addition, it should be noted that Figures 2 to 7 The diagram shows a simplified cross-sectional view of a specific example of the process of forming a partial film layer structure of a piezoelectric micro-electromechanical device. The number of piezoelectric film layers 120 and metal electrode layers 110 shown is only an example, and the piezoelectric micro-electromechanical device may include any number of piezoelectric film layers 120 and metal electrode layers 110.
[0056] After forming the metal electrode layer 110, a piezoelectric film layer 120 with a thickness of 0.1um to 2um is deposited on the metal electrode layer 110. The material of the piezoelectric film layer 120 at least includes aluminum nitride (AlN) or aluminum scandium nitride (AlScN). In addition, in the stacking direction D, the piezoelectric film layer 120 completely covers the metal electrode layer 110 below.
[0057] Finally, a patterned hard mask layer 130 is formed on the piezoelectric film layer 120 .
[0058] A patterned hard mask is prepared on the top surface of the piezoelectric film layer 120 to form a patterned hard mask layer 130. The remaining area on the piezoelectric film layer 120 where the patterned hard mask layer 130 is not set is left empty to prepare for the subsequent formation of the groove 140 to complete the process treatment of the piezoelectric film layer 120 before etching the groove 140.
[0059] The patterned hard mask layer 130 of the present application uses a hard mask instead of a photoresist mask because in subsequent Figure 4During the alkaline wet cleaning process shown, the cleaning solution will remove the photoresist together. In this way, a new round of photolithography process is required after the cleaning process to prepare the patterned hard mask layer 130, so that the subsequent dry etching process can continue. However, due to the limitations of the photolithography process itself and the influence of the accuracy of overlay (that is, each photolithography needs to be aligned with the calibrated pattern), each photolithography pattern cannot be completely aligned with the previous photolithography pattern, and deviations will occur. Therefore, even if a secondary photolithography and etching process is performed, the graphic morphology will inevitably deviate from the standard morphology. This has great uncertainty in determining whether the product's morphology is qualified and whether the performance is affected.
[0060] In order to avoid the problems at the photolithography process end, the present application adopts a patterned hard mask solution, and the hard mask needs a removal method that is compatible with it to complete the stripping or removal. Therefore, the material of the patterned hard mask layer 130 of the present application must meet the following conditions: the material of the patterned hard mask layer 130 basically does not react with the etching gas of the material of the piezoelectric film layer 120, that is, the etching rate of the etching gas of the piezoelectric film layer 120 on the patterned hard mask layer 130 is extremely low, and even does not etch the patterned hard mask layer 130, and the material of the patterned hard mask layer 130 also basically does not react with the alkaline cleaning solution; and the etching gas of the patterned hard mask layer 130 basically does not react with the material of the piezoelectric film layer 120; and the removal solution of the patterned hard mask layer 130 basically does not react with the material of the piezoelectric film layer 120 and the material of the metal electrode layer 110, and will not cause damage to the material of the piezoelectric film layer 120 and the material of the bottom metal electrode layer 110. Therefore, materials such as (silicon nitride) SiN and (silicon oxide) SiO2 that meet the above conditions are finally adopted as materials for patterned hard masks.
[0061] The hard mask used in this application overcomes the drawbacks of pattern dislocation and deformation caused by the cyclic process: because the wet cleaning in the cyclic process will remove the traditional photoresist mask, and multiple exposures will cause pattern deformation, dislocation and other problems. The patterned hard mask layer 130 process of this application avoids the above problems and ensures the morphology of the etched pattern.
[0062] Step 201 : dry-etching the area on the piezoelectric film layer 120 outside the patterned hard mask layer 130 to form a trench 140 in the piezoelectric film layer 120 .
[0063] The area outside the patterned hard mask layer 130 on the piezoelectric film layer 120 is etched toward the metal electrode layer 110 , that is, the middle area of the piezoelectric film layer 120 where the patterned hard mask layer 130 is not formed is etched, and a groove 140 is formed in the middle area of the piezoelectric film layer 120 .
[0064] In such Figure 3In the dry etching process shown, the piezoelectric film layer 120 is etched to form a groove 140 (the groove 140 is the area where the piezoelectric film layer 120 is etched, excluding the lateral area between the patterned hard mask layers 130).
[0065] In some embodiments, the dry etching process may be performed using Cl2 (chlorine) gas, Ar (argon) gas, other gases, or any combination thereof.
[0066] After the first round of etching is completed, due to the "redeposition effect", a layer of polymer 150 will exist on the side wall and bottom surface of the groove 140 to form a redeposition layer. Generally, the redeposition layer on the side surface of the groove 140 is thicker near the bottom surface of the groove 140, and relatively thinner near the top surface of the piezoelectric film layer 120. The "redeposition effect" means that due to the high output of polymer 150 during the etching process, it cannot be removed in time during the reaction process, and it will be re-deposited on the side wall or bottom surface of the groove 140 to form a redeposition layer. The redeposition layer will reduce the selectivity, uniformity and etching rate of the etching, and then lead to abnormal phenomena such as incomplete etching or incomplete etching.
[0067] Therefore, the present application adopts wet cleaning of the polymer 150 after etching to remove the redeposition layer, and then etches and wet cleans again, and repeats the cycle to remove the redeposition layer formed by the polymer 150 .
[0068] The dry etching mentioned in the above process is a technology used in microelectronics manufacturing and semiconductor processing, and its essence is a subtractive manufacturing technology for materials. Generally, before the etching process is carried out, it is necessary to prepare a patterned hard mask layer 130 on the etched area by photolithography technology, and the non-etched area is protected by the patterned hard mask layer 130. The substrate to be etched, which has a patterned hard mask layer 130, is placed in the vacuum working chamber of the etching machine. Under a vacuum environment, the machine generates plasma through an ion generator, and controls the plasma through a magnetic field to accelerate the generation of an ion beam to bombard the surface of the substrate. The ion energy is sufficient to destroy the chemical bonds on the surface of the substrate, thereby achieving etching. The reaction product-polymer 150 generated during the etching process will accumulate on the surface of the groove 140 and needs to be removed by vacuuming or other methods.
[0069] Step 202: wet-clean the trench 140 to remove the residual polymer 150 generated by etching.
[0070] The present application adopts an alkaline cleaning solution to wet clean the groove 140. In this process, DEKC solution is specifically used to remove Figure 3 The polymer 150 is shown on both side walls and the bottom of the groove 140 until the surface of the piezoelectric film layer 120 covered by the polymer 150 is exposed.
[0071] Generally, the wet removal process of polymer 150 is carried out using an alkaline solution. However, the alkaline solution will react with the material of the piezoelectric film layer 120. Even if the removal of polymer 150 is achieved, it will cause morphological damage and CD abnormality to the device. Therefore, the alkaline cleaning solution used in this application is a specially diluted DEKC solution. DEKC (Dilution EKC) is a solution obtained by diluting an EKC solution. EKC solution is an important chemical solution used in the semiconductor manufacturing process. In the wafer manufacturing industry, EKC solution is mainly used in wet cleaning processes, such as removing photoresists, pollutants on the wafer surface, and metal layers.
[0072] EKC itself contains a certain water concentration, and its dilution method can be selected to dilute with water so that the water concentration can be in the range of about 30% to about 45%. DEKC can also be diluted with methanol, and the methanol concentration of DEKC can be in the range of about 5% to about 30%.
[0073] Through experimental verification, by adjusting the concentration of DEKC solution, cleaning temperature and cleaning time, the polymer 150 can be effectively removed while the corrosion of the solution on the piezoelectric film layer 120 is greatly reduced.
[0074] Specifically, the execution process of the wet cleaning process mainly includes the following steps:
[0075] Removing the polymer 150 using a diluted DEKC solution: The DEKC solution treatment process may be performed by soaking, spraying, or any combination thereof. The DEKC solution treatment process may react with the polymer 150 at a temperature ranging from about 30° C. to about 90° C. for about 3 minutes to about 30 minutes to remove the polymer 150 in the groove 140.
[0076] The groove 140 is cleaned by an alcohol or ketone solution: the alcohol solution may be an isopropyl alcohol solution, etc., and the ketone solution may be an acetone solution, etc. The cleaning process is performed at a temperature ranging from about 10° C. to about 40° C., and the groove 140 is cleaned for about 1 minute to 30 minutes.
[0077] Rinse the trench 140 with deionized water: Rinse the trench 140 with deionized water at a temperature ranging from about 10° C. to about 40° C. for about 1 minute to 30 minutes.
[0078] Drying the groove 140: Drying the groove 140 at a temperature of 20° C. to 80° C. for about 1 minute to 45 minutes; the drying process uses appropriate drying equipment (eg, spin dryer, drying box, etc.) to completely dry the wafer.
[0079] It should be noted that the above four steps can be repeated multiple times and in different combinations to achieve the effect of effectively removing the polymer 150. Figure 4 The structural morphology shown.
[0080] Step 203 : When the metal electrode layer 110 is not exposed, dry etching and wet cleaning the groove 140 are performed again until the piezoelectric film layer 120 forms a target morphology and the metal electrode layer 110 is exposed.
[0081] After one etching and wet cleaning, the final morphology has not yet been formed, so etching and wet cleaning are performed again to complete the preparation of the final groove 140 morphology.
[0082] like Figure 5 As shown, during the second etching, the size of the groove 140 formed by the previous etching is enlarged to form a groove 141. The groove 141 is also cleaned by alkaline wet method to remove the polymer 150 generated by the second etching, and the obtained Figure 6 The structural morphology shown.
[0083] Etching and alkaline wet cleaning are repeated repeatedly until the metal electrode layer 110 is exposed, forming the final morphology of the trench 141 .
[0084] Compared with the semi-finished groove 140, the groove 141 formed after the piezoelectric film layer 120 is completely etched, and the bottom surface of the groove 141 is the top surface of the metal electrode layer 110; polymer 150 will still be produced on both sides of the groove 141 during this process and attached to the side and bottom surfaces. After each etching operation is completed, the product needs to be wet cleaned to remove the polymer 150 on the morphological surface to ensure the subsequent process.
[0085] like Figure 6 During the alkaline wet cleaning process shown, the polymer 150 on both sides and the bottom of the groove 141 is removed by the DEKC solution wet cleaning process. After the last etching and alkaline wet cleaning process, the final groove 141 structure of the piezoelectric film layer 120 is achieved, and the sides of the groove 141 and the bottom of the hole are not covered by the polymer 150.
[0086] Figure 6 The etching and alkaline wet cleaning process before removing the graphic hard mask layer 130 may be performed one or more times according to the specific product conditions to achieve the required structural morphology requirements. The process described in this application only shows the schematic cross-sectional diagram of the morphology structure of the first etching and the last etching, which does not mean that the process will only undergo two etching and cleaning processes. The number of cycles depends on the specific situation.
[0087] In some embodiments, the final morphology of the trench 141 may be achieved through five cycles of etching and alkaline wet cleaning.
[0088] The above-mentioned dry etching combined with the alkaline wet process cyclic operation mode overcomes the problem of difficult removal of polymers and polymer obstruction of the etching process during the etching of piezoelectric materials. In addition, while using alkaline solution to clean the piezoelectric material, the structural integrity of the piezoelectric film layer 120 is guaranteed: the alkaline solution will corrode the Al N or Al ScN material, but the present application uses the self-developed DEKC solution to greatly reduce the corrosion of the Al N or Al ScN material during the alkaline wet cleaning process, achieving the effect of almost no damage to the piezoelectric film layer, ensuring the morphology and integrity of the piezoelectric film layer 120. A metal that basically does not react with acid and alkali is also selected as the material of the metal electrode layer 110, avoiding damage to the metal electrode layer 110 during the wet cleaning process of the alkaline cleaning solution, and damage to the metal electrode layer 110 during the hard mask removal process by the acidic solution, thereby ensuring the electrical connection performance of the device.
[0089] Step 204 : Remove the patterned hard mask layer 130 .
[0090] Generally, the patterned hard mask layer 130 can be removed by a dry method or a wet method. In the present application, the patterned hard mask layer 130 is removed by a wet method.
[0091] Figure 7 In the patterned hard mask layer 130 removal process shown, the patterned hard mask layer 130 (generally Si N, etc.) on the top surface of the piezoelectric film layer 120 needs to be removed by a wet process. The removal solution used in the hard mask removal wet process can be an acidic solution such as BOE or a diluted hydrofluoric acid solution that reacts with hard mask materials such as Si N, but does not damage the piezoelectric film layer 120. The execution flow of the wet process mainly includes the following steps:
[0092] Hard mask removal solution treatment: BOE or diluted hydrofluoric acid solution is used to react with the patterned hard mask layer 130 at a temperature of 20° C. to 40° C. for 1 minute to 20 minutes; the removal solution used in the wet removal process of the patterned hard mask layer 130 cannot damage the piezoelectric film layer 120 and the metal electrode layer 110, so the removal solution of the patterned hard mask layer 130 can only be an acidic solution, which reacts with the material of the patterned hard mask layer 130 but does not react with the material of the piezoelectric film layer 120 and the metal electrode layer 110;
[0093] Deionized water cleaning: Use deionized water at a temperature of 10°C to 40°C for 1 minute to 30 minutes;
[0094] Drying: Dry at 20℃ to 80℃ for 1 minute to 45 minutes.
[0095] The hard mask removal solution treatment, deionized water cleaning, and drying process may be performed by immersion, spraying, or other methods or any combination thereof.
[0096] After removing the patterned hard mask layer 130, the Figure 7 On this basis, in other embodiments of the present application, other functional film layers 160 may be provided on the piezoelectric film layer 120 to form Figure 8 The structural morphology shown; these functional film layers 160 are prepared in a conventional manner and may or may not be patterned, which ultimately does not affect the main process of the present application and can be regarded as a compatible process.
[0097] In summary, the preparation method of the piezoelectric micro-electromechanical device provided in the embodiment of the present application is mainly aimed at the development of the etching process of the two piezoelectric materials, Al N or Al ScN, overcoming the influence of the "redeposition effect", and realizing the etching of the groove 141 of Al N or Al ScN: through the cyclic operation method combining etching and alkaline wet process adopted in the present application, the problem of the inability to etch and complete the groove morphology in one step during the etching of the groove 141 of piezoelectric thin film materials such as Al N or Al ScN, and the difficulty in removing the polymer are effectively solved, and finally the groove etching of Al N or Al ScN is realized.
[0098] No problems such as pattern dislocation or deformation: By selecting materials such as SiN to prepare the patterned hard mask layer 130, the existing use of photoresist masks during cyclic etching and wet processes will avoid pattern dislocation, overlap, and ultimately lead to abnormal morphology and CD, which provides extremely high protection for the pattern morphology and CD. (CD stands for Critical Dimension, which refers to the critical dimension that needs to be strictly controlled during the manufacturing process).
[0099] Hard masks are usually used in the wafer manufacturing industry to solve the problem that the thickness of the photoresist (PR) is not sufficient in a single etching step, and the photoresist cannot always fully cover the protection area during the entire etching step. Because the upper limit of the thickness of the photoresist is constrained by the machine and process conditions, it cannot always protect any material of any thickness, so the photoresist thickness will be insufficient in the actual manufacturing process.
[0100] Although the present application also uses a hard mask process, the scenarios solved and applied by the present application are quite different from the traditional hard mask application. The hard mask process of the present application is used to solve the new problems of morphological deformation and morphological abnormality generated by repeated etching and alkaline wet cleaning process in the present application. By setting conditions for the material of the patterned hard mask layer 130 to meet, the damage to the piezoelectric film layer 120 is greatly reduced, ensuring the integrity of the morphology.
[0101] The self-developed DEKC solution is used in the wet cleaning process to minimize the damage of the alkaline cleaning solution to the piezoelectric film layer 120 and protect the integrity of the structural morphology.
[0102] In general, the present application overcomes the problem of inability to etch through or penetrate the conventional Al N or Al ScN material trench etching process by optimizing the process flow, improving the solution, and using a patterned hard mask layer 130, and also solves the problem that the dry stripping process cannot remove the polymer.
[0103] On this basis, the present application also discloses a piezoelectric micro-electromechanical device, which is prepared by the above-mentioned piezoelectric micro-electromechanical device preparation method, such as Figure 7 As shown, the piezoelectric micro-electromechanical device includes a base layer 100 , a metal electrode layer 110 and a piezoelectric film layer 120 stacked in sequence. The piezoelectric film layer 120 is formed with a groove 141 , and the groove 141 extends to the metal electrode layer 110 and exposes the metal electrode layer 110 .
[0104] The material of the piezoelectric film layer 120 at least includes aluminum nitride or aluminum scandium nitride; the thickness of the metal electrode layer 110 is between 10 nm and 1 um, and the thickness of the piezoelectric film layer 120 is between 0.1 um and 2 um.
[0105] Based on this, in some other embodiments of the present application, other functional film layers 160 may be provided on the piezoelectric film layer 120 to form Figure 8 The structural morphology shown.
[0106] The piezoelectric micro-electromechanical device has the same structure and beneficial effects as the piezoelectric micro-electromechanical device in the aforementioned embodiment. The structure and beneficial effects of the piezoelectric micro-electromechanical device have been described in detail in the aforementioned embodiment, and will not be repeated here.
[0107] The above description is only an embodiment of the present application and is not intended to limit the protection scope of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims
1. A method for preparing a piezoelectric micro-electromechanical device, characterized in that: include: Providing a base layer, and sequentially forming at least a metal electrode layer, a piezoelectric film layer and a patterned hard mask layer on the base layer, wherein the patterned hard mask layer partially covers the piezoelectric film layer; wherein the material of the metal electrode layer does not react with an alkaline cleaning solution used in alkaline wet cleaning, and does not react with a removal solution of the patterned hard mask layer; dry etching the area outside the patterned hard mask layer on the piezoelectric film layer to form a groove on the piezoelectric film layer; alkaline wet cleaning of the trench to remove residual polymer generated by etching; When the metal electrode layer is not exposed, dry etching and alkaline wet cleaning of the groove again until the piezoelectric film layer forms a target morphology and the metal electrode layer is exposed; The patterned hard mask layer is removed.
2. The method for preparing a piezoelectric micro-electromechanical device according to claim 1, characterized in that: The method of providing a base layer, and sequentially forming at least a metal electrode layer, a piezoelectric film layer and a patterned hard mask layer on the base layer, wherein the patterned hard mask layer partially covers the piezoelectric film layer; wherein the material of the metal electrode layer does not react with an alkaline cleaning solution used in alkaline wet cleaning, and does not react with a removal solution of the patterned hard mask layer, comprises: Depositing the metal electrode layer with a thickness of 10nm to 1um on the base layer, wherein the material of the metal electrode layer includes at least molybdenum and ruthenium; Depositing the piezoelectric film layer with a thickness of 0.1 um to 2 um on the metal electrode layer, wherein the material of the piezoelectric film layer at least includes aluminum nitride or aluminum scandium nitride; The patterned hard mask layer is prepared on the piezoelectric film layer.
3. The method for preparing a piezoelectric micro-electromechanical device according to claim 2, characterized in that: The step of preparing the patterned hard mask layer on the piezoelectric film layer comprises: The material of the patterned hard mask layer basically does not react with the etching gas of the material of the piezoelectric film layer and the alkaline cleaning solution; and the etching gas of the patterned hard mask layer basically does not react with the material of the piezoelectric film layer; and the removal solution of the patterned hard mask layer basically does not react with the materials of the piezoelectric film layer and the metal electrode layer.
4. The method for preparing a piezoelectric micro-electromechanical device according to claim 1, characterized in that: The alkaline wet cleaning of the trench to remove the residual polymer generated by etching comprises: removing the polymer using a diluted DEKC solution; Cleaning the groove by alcohol or ketone solution; Cleaning the groove with deionized water; The grooves are dried.
5. The method for preparing a piezoelectric micro-electromechanical device according to claim 4, characterized in that: The step of removing the polymer using a diluted DEKC solution comprises: Diluting the EKC solution to obtain a diluted DEKC solution; wherein the EKC solution is diluted with water so that the water concentration in the DEKC solution is 30% to 45%; or the EKC solution is diluted with methanol so that the methanol concentration in the DEKC solution is 5% to 30%; The polymer in the trench is removed using the DEKC solution.
6. The method for preparing a piezoelectric micro-electromechanical device according to claim 4 or 5, characterized in that: The alkaline wet cleaning of the trench to remove the residual polymer generated by etching comprises: At a temperature of 30° C. to 90° C., reacting the diluted DEKC solution with the polymer for 3 to 30 minutes; At a temperature of 10° C. to 40° C., the groove is cleaned with an alcohol or ketone solution for 1 minute to 30 minutes; Cleaning the groove with deionized water at a temperature of 10° C. to 40° C. for 1 minute to 30 minutes; The groove is dried at a temperature of 20° C. to 80° C. for 1 minute to 45 minutes.
7. The method for preparing a piezoelectric micro-electromechanical device according to claim 1, characterized in that: The removing of the patterned hard mask layer comprises: The patterned hard mask layer removal solution is used to react with the patterned hard mask layer at a temperature of 20° C. to 40° C. for 1 minute to 20 minutes; wherein the patterned hard mask layer removal solution reacts with the material of the patterned hard mask layer and does not react with the materials of the piezoelectric film layer and the metal electrode layer; Use deionized water at a temperature of 10°C to 40°C for 1 minute to 30 minutes; Dry at 20°C to 80°C for 1 minute to 45 minutes.
8. A piezoelectric micro-electromechanical device, prepared according to the method for preparing a piezoelectric micro-electromechanical device according to any one of claims 1 to 7, characterized in that: The invention comprises a base layer, a metal electrode layer and a piezoelectric film layer which are stacked in sequence. The piezoelectric film layer is formed with a groove which extends to the metal electrode layer and exposes the metal electrode layer.
9. The piezoelectric micro-electromechanical device according to claim 8, characterized in that: The material of the piezoelectric film layer at least includes aluminum nitride or aluminum scandium nitride.
10. The piezoelectric micro-electromechanical device according to claim 8 or 9, characterized in that: A functional film layer is also arranged on the piezoelectric film layer.