Wafer cavity preparation method and wafer
Through supercritical fluid drying technology, the problems of wafer deformation and damage during cavity drying are solved, and the stable drying of the cavity is achieved, ensuring the integrity and yield of MEMS devices.
Patent Information
- Application Number
- CN202411308181.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-19
- Publication Date
- 2024-12-20
AI Technical Summary
In the chip production of microelectromechanical system (MEMS) devices, the wafer is easily deformed or damaged by force during cavity drying, resulting in device damage.
Using supercritical fluid drying technology, the supercritical fluid in liquid state is injected into the drying device and heated and pressurized to the supercritical state, so that it escapes in a gas state, avoiding the surface tension formed by the gas-liquid interface, thereby protecting the cavity. The wall surface is not subject to deformation or damage.
It effectively avoids deformation and damage of wafers during cavity drying, ensuring device integrity and yield.
Smart Images
Figure CN119160853A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of wafer processing technology, and in particular to a wafer cavity preparation method and a wafer. Background Art
[0002] At present, various cavity structures are needed in the chip production process of micro-electro-mechanical system (MEMS) devices. For example, the cavity filter is a microwave filter using a resonant cavity structure, and the cavity can be equivalent to an inductor in parallel with a capacitor, thereby forming a resonant stage to realize the microwave aluminum foil function.
[0003] The production of the cavity requires a temporary filling material to support the upper covering material and prevent it from collapsing. A wet etching solution is then used to remove the temporary filling material, followed by a drying process to form a cavity structure.
[0004] However, during the drying process of the cavity, there are gas and liquid in the cavity. The gas is easy to evaporate into the environment, while the liquid in the cavity is slowly removed, which can easily cause deformation of the cavity structure and even damage the device.
[0005] In summary, during the cavity drying process, the wafer is easily deformed or damaged by the force, which is an urgent problem to be solved. Summary of the invention
[0006] A wafer cavity preparation method and a wafer provided in an embodiment of the present application can avoid deformation or damage of the wafer during cavity drying.
[0007] According to a first aspect of an embodiment of the present application, a method for preparing a wafer cavity is provided, comprising:
[0008] removing the sacrificial layer using an etching solution to form a cavity on the wafer;
[0009] Clean the cavity with deionized water and isopropyl alcohol to remove the corrosive liquid in the cavity;
[0010] placing the wafer into a drying device, the drying device being used to inject a liquid supercritical fluid into a cavity;
[0011] heating and pressurizing a supercritical fluid to a supercritical state;
[0012] The drying device is controlled to stop heating and release pressure, so that the supercritical fluid escapes out of the cavity at least in the form of gas.
[0013] In some embodiments, cleaning the chamber with deionized water and isopropyl alcohol comprises:
[0014] The cavity is cleaned with deionized water, wherein the cavity includes a mixed liquid, and the mixed liquid includes residual corrosive liquid and deionized water;
[0015] Inject isopropyl alcohol into the cavity to soak the cavity;
[0016] Among them, isopropyl alcohol is used to combine with water molecules in the mixed liquid.
[0017] In some embodiments, the number of times isopropyl alcohol is injected into the cavity is at least two times.
[0018] In some embodiments, injecting isopropyl alcohol into the cavity to soak the cavity comprises:
[0019] The isopropyl alcohol is introduced into the cavity for the first time, and the first immersion time of the cavity is the first time;
[0020] Isopropyl alcohol is introduced into the cavity for the second time, and the second immersion time of the cavity is the second time.
[0021] In some embodiments, the first time and the second time are both in the range of 5-10 min.
[0022] In some embodiments, the number of times deionized water is injected into the cavity is at least twice;
[0023] The single injection time of deionized water is in the range of 5-10 minutes.
[0024] In some embodiments, the etching solution comprises hydrofluoric acid; and / or
[0025] Supercritical fluids include liquid carbon dioxide.
[0026] In some embodiments, heating and pressurizing a supercritical fluid to a supercritical state comprises:
[0027] The drying device is controlled to heat the temperature of the supercritical fluid to the supercritical temperature and supercritical pressure corresponding to the supercritical fluid.
[0028] In some embodiments, the depth of the cavity is less than or equal to 1 μm; and / or
[0029] The drying device is a supercritical dryer; and / or
[0030] The material of the sacrificial layer includes silicon dioxide.
[0031] According to a second aspect of an embodiment of the present application, a wafer is provided, which is prepared using any of the above-mentioned wafer cavity preparation methods.
[0032] The beneficial effects of this application are:
[0033] The supercritical fluid eliminates the surface tension in the cavity, so the wall surface of the cavity will not be deformed by the surface tension, which means that the device will not be damaged. After the fluid in the cavity is drained, the drying process of the wafer cavity is completed. BRIEF DESCRIPTION OF THE DRAWINGS
[0034] Figure 1 A schematic flow chart of a wafer cavity preparation method provided in an embodiment of the present application;
[0035] Figure 2 A schematic partial structural diagram of a wafer provided in an embodiment of the present application.
[0036] The reference numerals in the figure represent respectively:
[0037] 100, first dielectric layer; 200, second dielectric layer; 210, via hole; 300, cavity; Y, first direction. DETAILED DESCRIPTION
[0038] In order to better understand the technical solutions provided by the embodiments of this specification, the technical solutions of the embodiments of this specification are described in detail below through the accompanying drawings and specific embodiments. It should be understood that the embodiments of this specification and the specific features in the embodiments are detailed descriptions of the technical solutions of the embodiments of this specification, rather than limitations on the technical solutions of this specification. In the absence of conflict, the embodiments of this specification and the technical features in the embodiments can be combined with each other.
[0039] In this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements limited by the statement "comprise one..." do not exclude the existence of other identical elements in the process, method, article or equipment including the elements. The term "more than two" includes two or more than two situations.
[0040] At present, various cavity structures are needed in the chip production process of micro-electromechanical system devices. For example, the cavity filter is a microwave filter using a resonant cavity structure. The cavity can be equivalent to an inductor in parallel with a capacitor, thereby forming a resonant level and realizing the function of microwave aluminum foil. The production of the cavity requires a temporary filling material to support the upper covering material from collapsing. After that, the temporary filling material is removed cleanly using a wet etching solution, and then a drying process is performed to form a cavity structure. However, during the drying process of the cavity, there are gas and liquid in the cavity. The gas is easy to evaporate into the environment, while the liquid in the cavity is removed slowly, resulting in a large surface tension between the interface of the gas and the liquid. The surface tension will cause the corresponding avoidances of the cavity to be close to each other, which is easy to cause deformation of the cavity structure and even damage to the device. In summary, during the cavity drying process, the wafer is easily deformed or damaged by the force, which is an urgent problem to be solved.
[0041] In view of this, a wafer chamber preparation method and a wafer provided in an embodiment of the present application can avoid deformation or damage of the wafer during the chamber drying process.
[0042] In the first aspect of this application, Figure 1 A schematic flow chart of a wafer cavity preparation method provided in an embodiment of the present application, referring to Figure 1 , provides a wafer cavity preparation method, comprising:
[0043] S100: removing the sacrificial layer by using an etching solution to form a cavity on the wafer;
[0044] In some examples, a sacrificial layer is disposed on one side of the first dielectric layer, a partial structure of the sacrificial layer is etched, and a second dielectric layer is disposed on a side of the first dielectric layer facing the sacrificial layer, so that the sacrificial layer is formed between the first dielectric layer and the second dielectric layer, and a plurality of vias are etched and developed on the second dielectric layer. The vias can connect the sacrificial layer with a side of the second dielectric layer away from the first dielectric layer, and the corrosive liquid contacts the sacrificial layer through the vias, thereby corroding the sacrificial layer, so that a cavity is formed between the first dielectric layer and the second dielectric layer.
[0045] S200: Cleaning the cavity with deionized water and isopropyl alcohol to remove the corrosive liquid in the cavity;
[0046] In some examples, after the cavity is formed by the corrosive liquid, the corrosive liquid in the cavity will be poured out, but some corrosive liquid will remain in the cavity. The residual corrosive liquid will cause the wall of the cavity corresponding to the wafer to have moisture, which will reduce the dryness of the wafer. At the same time, the moisture can also be transmitted to the display area of the display panel through the cavity wall, causing damage to the display device. The corrosive liquid on the surface of the cavity can be removed by flushing the cavity with deionized water. By utilizing the water absorption characteristics of isopropyl alcohol, the water in the residual corrosive liquid can be replaced by injecting isopropyl alcohol into the cavity, and isopropyl alcohol is highly volatile and can evaporate outside the cavity.
[0047] S300: placing the wafer into a drying device, the drying device is used to inject a liquid supercritical fluid into the cavity;
[0048] In some examples, the cavity has residual isopropyl alcohol from step S200, and the supercritical fluid can be in liquid state, that is, in fluid state, at room temperature. The drying device can control corresponding parameters such as temperature and pressure to make the supercritical fluid in a supercritical state, and the supercritical fluid in a supercritical state can replace the isopropyl alcohol.
[0049] S400: heating and pressurizing the supercritical fluid to a supercritical state;
[0050] In some examples, the supercritical fluid may be in liquid form at room temperature. A state above the critical temperature and critical pressure and close to the critical point is a supercritical state. When the supercritical fluid is in a supercritical state, the gas and liquid phases of the supercritical fluid have similar properties, and the supercritical fluid may be between the gas phase and the liquid phase, that is, there is no surface tension between the supercritical fluid and isopropyl alcohol.
[0051] S500: controlling the drying device to stop heating and release pressure, so that the supercritical fluid escapes out of the cavity at least in the form of gas;
[0052] In some examples, the density of the supercritical fluid that is heated and pressurized to a supercritical state increases, and its solubility is enhanced. In the supercritical state, there is no gas-liquid interface between the gas and liquid states of the supercritical fluid, and it becomes a uniform fluid between the gas and the liquid, and can be discharged from the cavity to the environment. Since the gas-liquid interface forms surface tension, and the supercritical fluid does not form surface tension, the wall surface corresponding to the cavity will not be deformed or even ruptured by the force of the supercritical fluid. When the supercritical state is maintained for a certain period of time, or when it is determined that all the supercritical fluid in the cavity is discharged out of the cavity, it can be determined that the cavity drying process of the crystal is completed.
[0053] Generally, the cavity can be dried by wet etching cavity process, for example, using a corrosive liquid, such as hydrofluoric acid, to remove the sacrificial layer to obtain a cavity structure, i.e., a cavity. Then the silicon wafer is rinsed with deionized water to remove the hydrofluoric acid remaining on the surface of the cavity, and since the cavity is a cavity structure, a mixture of hydrofluoric acid and water remains in the cavity. Then isopropanol is used to replace the residue in the cavity, and finally hot nitrogen or an oven is used to evaporate the isopropanol remaining in the cavity, thereby obtaining a silicon wafer with a dry cavity. However, during the evaporation of isopropanol in the cavity, the cavity contains gas, and the gas can escape to the outside of the cavity faster, while the liquid in the cavity is removed slowly, so that the interface between the gas and the liquid can form a large surface tension, and the surface tension causes the wall of the cavity to deform, and even the cavity structure and the substrate contact to form a contact surface, so that the wall of the cavity adheres under the action of the van der Waals force of the contact surface. The above-mentioned deformation and adhesion can cause semiconductor devices to fail and reduce product yield.
[0054] The present application uses a supercritical fluid in a supercritical state, and the supercritical fluid in the supercritical state is between the gas phase and the liquid phase, so that there is no gas-liquid interface in the cavity, that is, there is no surface tension, so that the wall surface corresponding to the cavity will not be deformed by the surface tension, that is, the device will not be damaged. After the fluid in the cavity is drained, the drying process of the wafer cavity is completed. The drying process of the present application prevents the wafer corresponding to the cavity from being deformed due to the force, and the cavity after the drying process can be in a dry state.
[0055] In some examples, step S200: cleaning the cavity with deionized water and isopropyl alcohol to remove the corrosive liquid in the cavity includes:
[0056] S210: cleaning the cavity with deionized water, wherein the cavity includes a mixed liquid, and the mixed liquid includes daughter ion water and residual corrosive liquid;
[0057] In some examples, deionized water is pure water from which impurities in the form of ions have been removed. Deionized water can remove ions from water through an RO (Reverse Osmosis) membrane and a mixed bed resin. Deionized water is injected into the cavity to clean the cavity, and the cavity cleaning operation is completed by pouring the deionized water out of the cavity. After the step of pouring the deionized water is completed, there will be residual solution on the wall surface corresponding to the cavity, and the residual solution is the above-mentioned mixed solution.
[0058] S220: injecting isopropyl alcohol into the cavity to soak the cavity;
[0059] In some examples, isopropyl alcohol is a colorless transparent liquid with an odor similar to a mixture of ethanol and acetone. Isopropyl alcohol can be dissolved in organic solvents such as water, alcohol, ether, benzene, chloroform, etc., and has good water absorption. By utilizing the characteristics of isopropyl alcohol, the water in the mixed liquid can be absorbed by isopropyl alcohol, thereby replacing the residue in the cavity.
[0060] In some examples, the isopropyl alcohol can bind to water molecules in the mixture.
[0061] Exemplarily, isopropanol can react with water molecules in the mixture, and the chemical reaction formula can be: (CH3)2CHOH+H2O→(CH3)2CO+H2O2.
[0062] In some examples, the number of times that isopropyl alcohol is injected into the cavity is at least two times.
[0063] Exemplarily, by injecting isopropyl alcohol multiple times, more of the mixed liquid in the cavity can be replaced by isopropyl alcohol.
[0064] In some examples, the immersion time of the isopropyl alcohol is adjusted based on the content of the mixed liquid in the cavity.
[0065] Exemplarily, the immersion time of isopropyl alcohol can be gradually reduced as the number of injections increases.
[0066] Exemplarily, step S220: injecting isopropyl alcohol into the cavity may include:
[0067] S221: introducing isopropyl alcohol into the cavity for the first time, and the first immersion time of the cavity is the first time;
[0068] In some examples, the first time may be 5-10 minutes.
[0069] S222: introducing isopropyl alcohol into the cavity for a second time, and the second immersion time of the cavity is a second time;
[0070] In some examples, the second time may be 5-10 minutes.
[0071] In some examples, the first time and the second time are both in the range of 5-10 minutes.
[0072] In some examples, the number of times the deionized water is injected into the cavity is at least two times.
[0073] In some examples, the single injection time of deionized water ranges from 5 to 10 minutes.
[0074] In some examples, step S210: cleaning the cavity with deionized water may include:
[0075] S211: injecting deionized water into the cavity for the first time, and the injection time of the deionized water is the third time;
[0076] In some examples, the third time may be 5-10 minutes.
[0077] S212: injecting deionized water into the cavity for a second time, the injection time of the deionized water being a fourth time;
[0078] In some examples, the fourth time may be 5-10 minutes.
[0079] In some examples, the third time and the fourth time both range from 5 minutes.
[0080] In some examples, as the number of deionized water cleanings increases, the amount of residual corrosive liquid in the chamber decreases, and thus the deionized water cleaning time can be gradually reduced as the number of cleanings increases.
[0081] Typically, the cavity is made by a wet process, so that the wall of the cavity corresponding to the wafer may be uneven, and the etching liquid may remain in the depressions of the wall, for example, the etching liquid remains on the side walls and bottom surface corresponding to the cavity.
[0082] In some examples, step S400: heating and pressurizing a supercritical fluid to a supercritical state includes:
[0083] S410: Controlling the drying device to heat the temperature of the supercritical fluid to a supercritical temperature and a supercritical pressure corresponding to the supercritical fluid.
[0084] Exemplarily, the supercritical fluid may be liquid carbon dioxide, the supercritical temperature of the supercritical fluid may be 31.1° C., and the supercritical pressure of the supercritical fluid may be 7.39 MPa.
[0085] Exemplarily, the supercritical fluid may also be ammonia, ethylene, propane, propylene or water, and different supercritical fluids may correspond to different supercritical temperatures and supercritical pressures. When different supercritical fluids are selected, the drying device may select different supercritical temperatures and supercritical pressures.
[0086] In some examples, during the heating and pressurizing process of the drying device, the isopropyl alcohol in the cavity will be evaporated, and during the evaporation of the isopropyl alcohol, the liquid capacity in the cavity is slowly removed, and the liquid carbon dioxide at the above temperature and pressure can be in a supercritical state, so that there is no gas-liquid interface between the supercritical carbon dioxide and the mixed liquid, and therefore there is no gas-liquid interface in the wall, that is, no surface tension will be formed at the interface between the liquid and the air, and the wall surface of the cavity corresponding to the crystal will not be deformed or even damaged. After the fluid in the cavity is discharged, the drying process of the cavity is completed.
[0087] Normally, hot nitrogen or an oven can be used to evaporate the isopropanol in the cavity, but as the isopropanol is evaporated, the residual solution in the cavity is slowly removed, resulting in a large surface tension at the interface between the liquid and the gas. The vertical component of the surface tension between the gas-liquid interface in the cavity will pull the adjacent structures of the cavity closer to each other, causing the wall of the cavity structure to deform, and even causing the substrate and semiconductor material of the wafer, such as the first dielectric layer and the second dielectric layer, to contact, and adhere under the action of the van der Waals force on the contact surface. Adhesion, deformation or damage will cause the failure of semiconductor microelectromechanical systems (MEMS) devices, resulting in a reduction in the yield rate of finished products.
[0088] In some examples, the etching fluid includes hydrofluoric acid.
[0089] Exemplarily, the sacrificial layer is a silicon dioxide sacrificial layer. Hydrofluoric acid is highly corrosive and volatile, and can be used to remove oxide layers on the surface of semiconductor silicon wafers, and can also be used for cleaning and etching metal surfaces.
[0090] In some examples, the supercritical fluid includes liquid carbon dioxide.
[0091] For example, carbon dioxide in a supercritical state has high solubility and good selectivity. Supercritical carbon dioxide can dissolve organic and inorganic substances and can also be used as an extraction solvent and reaction medium.
[0092] Typically, when the depth of the cavity is less than 1 μm, the surface tension of the gas-liquid interface can cause damage to the device structure.
[0093] In some examples, the depth of the cavity of the present application may be less than or equal to 1 μm.
[0094] Illustratively, no gas-liquid interface will be formed between the gas and liquid in the supercritical state, and thus no surface tension will be generated. The wall of the cavity will not adhere due to the surface tension, so the depth of the cavity can be smaller, and no adhesion or breakage will occur due to surface tension during the drying process. Therefore, the thickness of the wafer prepared by the wafer cavity preparation method of the present application can be thinner.
[0095] In some examples, the drying device is a supercritical dryer.
[0096] In some examples, the material of the sacrificial layer includes silicon dioxide.
[0097] Figure 2 An exemplary partial structure diagram of a wafer provided in an embodiment of the present application. Figure 2In a second aspect of the present application, a wafer is provided, which is prepared by using the wafer cavity preparation method in any of the above technical solutions.
[0098] In some examples, reference Figure 2 A sacrificial layer is disposed on one side of the first dielectric layer 100, a partial structure of the sacrificial layer is subjected to an etching process, and a second dielectric layer 200 is disposed on the side of the first dielectric layer 100 facing the sacrificial layer, so that the sacrificial layer is formed between the first dielectric layer 100 and the second dielectric layer 200, and the orthographic projection of the sacrificial layer on the first dielectric layer 100 falls into the orthographic projection of the second dielectric layer 200 on the first dielectric layer 100, so that the second dielectric layer 200 can cover the sacrificial layer.
[0099] In some examples, a photoresist is disposed on a side of the second dielectric layer away from the first dielectric layer. The photoresist may be spin-coated on a surface of the second dielectric layer away from the first dielectric layer. The orthographic projection of the photoresist on the first dielectric layer covers the orthographic projection of the second dielectric layer on the first dielectric layer.
[0100] In some examples, multiple hollows are formed on the photoresist by exposure and development, and adjacent hollows can be spaced apart. The hollows connect the second dielectric layer and the side of the photoresist away from the first dielectric layer, and the orthographic projection of the hollows on the first dielectric layer falls into the orthographic projection of the sacrificial layer on the first dielectric layer.
[0101] In some examples, reference Figure 2 A plurality of via holes 210 may be formed on the second dielectric layer 200 by dry etching, and the via holes 210 may connect the sacrificial layer and the hollowing, that is, the via holes 210 may connect the sacrificial layer with the side of the second dielectric layer 200 away from the first dielectric layer 100 .
[0102] In some examples, reference Figure 2 , the orthographic projection of the via hole 210 on the first dielectric layer 100 covers the orthographic projection of the hollow on the first dielectric layer 100 , and the orthographic projection of the via hole 210 on the first dielectric layer 100 falls into the orthographic projection of the sacrificial layer on the first dielectric layer 100 .
[0103] In some examples, reference Figure 2 The photoresist or the residual polymer of the photoresist can be removed by a wet process, and then an etching solution is injected through the via 100 to the surface of the sacrificial layer facing the second dielectric layer, so that the etching solution contacts and corrodes the sacrificial layer, thereby etching away the sacrificial layer, so that a cavity 300 is formed between the first dielectric layer 100 and the second dielectric layer 200. In addition, the space corresponding to the cavity 300 is also the space corresponding to the sacrificial layer.
[0104] In some examples, the etching solution may be hydrofluoric acid.
[0105] In some examples, reference Figure 2 , the height of the cavity 300 in the first direction Y may be less than or equal to 1 μm.
[0106] Exemplary, reference Figure 2 The supercritical fluid in the cavity 300 creates a gas-liquid interface between the gas and the liquid, thereby preventing surface tension from being formed. The depth of the cavity 300, that is, the size of the cavity 300 in the first direction Y, can be made smaller, for example, less than 1 μm.
[0107] In some examples, reference Figure 2 The first dielectric layer 100 may include a flexible substrate or a hard substrate, the flexible substrate may include polyimide, the hard substrate may be glass, or the first dielectric layer 100 may be a silicon wafer. The material of the second defining layer 200 may be polysilicon, and the material of the sacrificial layer may be silicon dioxide.
[0108] It should be noted that in the above embodiments, the description of each embodiment has its own emphasis, and for parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.
[0109] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.
[0110] Although the preferred embodiments of this specification have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of this specification.
[0111] Obviously, those skilled in the art can make various changes and modifications to this specification without departing from the spirit and scope of this specification. Thus, if these modifications and variations of this specification fall within the scope of the claims of this specification and their equivalents, this specification is also intended to include these modifications and variations.
Claims
1. A method for preparing a wafer cavity, characterized in that: include: removing the sacrificial layer using an etching solution to form a cavity on the wafer; Cleaning the cavity with deionized water and isopropyl alcohol to remove the corrosive liquid in the cavity; Placing the wafer into a drying device, wherein the drying device is used to inject a liquid supercritical fluid into the cavity; heating and pressurizing the supercritical fluid to a supercritical state; The drying device is controlled to stop heating and release pressure, so that the supercritical fluid escapes out of the cavity at least in a gaseous form.
2. The wafer cavity preparation method according to claim 1, characterized in that: The method of cleaning the cavity with deionized water and isopropyl alcohol comprises: Cleaning the cavity with deionized water, wherein the cavity includes a mixed liquid, and the mixed liquid includes the residual corrosive liquid and the deionized water; injecting isopropyl alcohol into the cavity to soak the cavity; Wherein, the isopropanol is used to combine with water molecules in the mixed solution.
3. The wafer cavity preparation method according to claim 2, characterized in that: The number of times of injecting isopropyl alcohol into the cavity is at least twice.
4. The wafer cavity preparation method according to claim 2, characterized in that: The step of injecting isopropyl alcohol into the cavity to soak the cavity comprises: The isopropanol is introduced into the cavity for the first time, and the first immersion time of the cavity is the first time; The isopropanol is introduced into the cavity for a second time, and the second immersion time of the cavity is a second time.
5. The wafer cavity preparation method according to claim 4, characterized in that: The first time and the second time are both in the range of 5-10 minutes.
6. The wafer cavity preparation method according to claim 2, characterized in that: The number of times of injecting deionized water into the cavity is at least twice; The single injection time of deionized water is in the range of 5-10 minutes.
7. The wafer cavity preparation method according to claim 1, characterized in that: The etching solution comprises hydrofluoric acid; and / or The supercritical fluid includes liquid carbon dioxide.
8. The wafer cavity preparation method according to claim 1, characterized in that: The step of heating and pressurizing the supercritical fluid to a supercritical state comprises: The drying device is controlled to heat the temperature of the supercritical fluid to a supercritical temperature and a supercritical pressure corresponding to the supercritical fluid.
9. The wafer cavity preparation method according to claim 1, characterized in that: The depth of the cavity is less than or equal to 1 μm; and / or The drying device is a supercritical dryer; and / or The material of the sacrificial layer includes silicon dioxide.
10. A wafer, characterized in that: The wafer cavity is prepared by the wafer cavity preparation method as described in any one of claims 1 to 9.