Etching method and etching equipment for silicon-based nitride film layer

Abstract

The invention provides an etching method and etching equipment for a silicon-based nitride thin film layer. The etching method comprises the following steps: providing a substrate with the silicon-based nitride thin film layer on the surface; the silicon-based nitride thin film layer is placed in an etching groove containing phosphoric acid etching liquid to remove the silicon-based nitride thin film layer, and in the etching process, a bubble generating device in the etching groove introduces micro-nano bubbles into the phosphoric acid etching liquid to trigger micro-turbulence to promote etching uniformity; and the micro-nano bubbles crack on the surface of the silicon-based nitride thin film layer to generate local pressure so as to enhance the etching reaction. Based on the synergistic effect of the micro-nano bubbles and the phosphoric acid etching liquid, efficient removal of the silicon-based nitride thin film layer is achieved. Compared with a traditional etching process, the etching rate is improved by more than 30%, the etching uniformity is greatly optimized, and the etching selection ratio of the silicon-based nitride thin film layer and the oxide thin film layer is greatly improved. Meanwhile, the introduction of the micro-nano bubbles significantly reduces the dosage of chemicals, the production cost and the environmental burden.

Description

Technical Field

[0001] The present invention belongs to the technical field of wet etching, and relates to an etching method and an etching device for a silicon-based nitride thin film layer. Background Art

[0002] In semiconductor manufacturing processes, due to its excellent dielectric properties, good thermal stability, high mechanical strength and other characteristics, the silicon-based nitride thin film layer is widely used as a mask layer, an insulating layer, a stress control layer and other functional structure layers. In specific process flows of semiconductor manufacturing, accurately removing these silicon-based nitride thin film layers used as mask layers, insulating layers or for other functional purposes is a necessary condition to ensure the smooth progress of subsequent processes, reliable device quality and process stability. The wet etching process with hot phosphoric acid (H3PO4) has become the main method for removing the silicon-based nitride thin film layer due to its simple process, low cost, suitability for large-scale production and other advantages. However, in practical applications, there are still some obvious deficiencies in this technology, which limit its further promotion and optimization. For example:

[0003] (1) Low etching rate and poor etching uniformity: During the process of removing the silicon-based nitride thin film layer by wet etching with hot phosphoric acid, phosphoric acid acts as a catalyst and water molecules act as reactants. As the reaction progresses, water molecules are continuously consumed, resulting in the gradual formation of an interfacial layer with a low water content near the surface of the silicon-based nitride thin film layer (as shown in Figure 1 ). The existence of this interfacial layer with a low water content not only significantly reduces the etching rate but also has an adverse effect on the etching uniformity. Especially for the etching of the silicon-based nitride thin film layer on high aspect ratio or complex graphic structures, the existence of this interfacial layer will cause obvious concentration gradient changes near the surface of the silicon-based nitride thin film layer, further exacerbating the difference in etching rates in different regions and seriously affecting the etching uniformity. In addition, since the process of removing the silicon-based nitride thin film layer by wet etching with hot phosphoric acid mainly relies on the self-diffusion and flow of the etching solution, for large-area substrates or substrates with complex graphic structures, uneven temperature distribution or unstable flow state of the etching solution are likely to cause etching non-uniformity, which in turn has an adverse effect on processing consistency and etching quality.

[0004] (2) Many pollution particles: The by-product particles generated during the etching process are easily attached to the substrate surface, which not only pollutes the subsequent processes but also reduces the yield and overall performance of the device structure.

[0005] (3) Poor etching selectivity: In the film layer structure of the substrate, an oxide film layer is often accompanied at the bottom of the silicon-based nitride film layer. During the process of removing the silicon-based nitride film layer by the hot phosphoric acid wet etching process, as the etching progresses, the silicon-based nitride film layer is gradually etched, and the oxide film layer is gradually exposed. However, in the existing hot phosphoric acid wet etching process, when the etching solution temperature is relatively low (such as below 160 °C), the etching selectivity for the silicon-based nitride film layer (such as the silicon nitride layer) and the oxide film layer (such as the silicon oxide layer) is relatively low (such as below 55:1), and the etching selectivity is poor. This causes a certain degree of damage to the oxide film layer during the etching process, thereby triggering structural defects or process problems.

[0006] Therefore, how to provide an etching method and an etching device for a silicon-based nitride film layer to improve the etching rate, improve the etching uniformity, enhance the etching selectivity, and reduce the number of contamination particles, so as to meet the requirements of high-efficiency and high-quality semiconductor manufacturing, has become an important technical problem urgently to be solved by those skilled in the art.

[0007] It should be noted that the above introduction of the technical background is only for the convenience of clearly and completely explaining the technical solutions of the present application and facilitating the understanding of those skilled in the art. It cannot be considered that the above technical solutions are well-known to those skilled in the art just because these solutions are described in the background art part of the present application. 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 an etching method and an etching device for a silicon-based nitride film layer, which are used to solve the problems of low etching rate, poor etching uniformity, many contamination particles, and poor etching selectivity existing in the prior art when using the hot phosphoric acid wet etching process to remove the silicon-based nitride film layer.

[0009] To achieve the above purpose and other related purposes, the present invention provides an etching method for a silicon-based nitride film layer, including the following steps:

[0010] Provide a substrate, and a silicon-based nitride film layer is provided on the surface of the substrate;

[0011] Place the substrate in an etching tank containing a phosphoric acid etching solution to remove the silicon-based nitride film layer. Among them, a bubble generating device is provided in the etching tank, and the bubble generating device introduces micro-nano bubbles into the phosphoric acid etching solution during the etching process of the silicon-based nitride film layer to initiate micro-turbulence in the phosphoric acid etching solution to promote etching uniformity, and the micro-nano bubbles burst on the surface of the silicon-based nitride film layer to generate local pressure to enhance the etching reaction.

[0012] Optionally, the diameter range of the micro-nano bubbles is 1 to 200 nanometers, and the micro-nano bubbles include at least one of nitrogen bubbles, helium bubbles, and argon bubbles.

[0013] Optionally, the phosphoric acid etching solution is prepared by mixing concentrated phosphoric acid with a mass fraction of 70% to 98% and deionized water in a preset ratio. During the etching process, the temperature of the phosphoric acid etching solution is controlled within the range of 150 to 180 °C, and the concentration range of the micro-nano bubbles in the phosphoric acid etching solution is 10 7 ~10 8 per mL.

[0014] Optionally, the phosphoric acid etching solution further includes a stabilizer, and the stabilizer includes boric acid.

[0015] Optionally, the silicon nitride-based thin film layer includes a silicon nitride layer or a silicon oxynitride layer.

[0016] Optionally, before placing the substrate in the etching tank containing the phosphoric acid etching solution, it further includes a step of pre-cleaning the substrate with a first cleaning solution.

[0017] Optionally, the silicon nitride-based thin film layer is used as a masking layer during the formation of a shallow trench isolation structure, a local oxidation of silicon isolation structure, or a self-aligned contact structure.

[0018] Optionally, after removing the silicon nitride-based thin film layer, it further includes the following steps:

[0019] Placing the substrate in a hot water tank for cleaning to remove the phosphoric acid etching solution remaining on the surface of the substrate;

[0020] Placing the substrate in a cleaning tank and cleaning the substrate with a second cleaning solution;

[0021] Performing a drying treatment on the surface of the substrate.

[0022] To achieve the above and other related purposes, the present invention further provides an etching device, which is used to etch the silicon nitride-based thin film layer as described in any one of the above, and includes:

[0023] An etching tank for containing an etching solution, and an etching solution inlet and a drain outlet are provided in the etching tank;

[0024] A flow equalizing plate is located between the notch of the etching tank and the etching solution inlet. The flow equalizing plate includes a plate body and a plurality of through holes penetrating the plate body, and the through holes are used to disperse the etching solution and micro-nano bubbles;

[0025] The bubble generating device is arranged in the etching tank and below the flow equalizing plate. The bubble generating device is connected to an external gas source supply system to generate micro-nano bubbles. A flow regulating valve and a power regulating device are arranged between the bubble generating device and the gas source supply system. The flow regulating valve and the power regulating device are used to control the generation frequency and size of the micro-nano bubbles.

[0026] Optionally, the etching tank further includes a temperature control module for controlling the temperature of the etching solution.

[0027] As described above, the present invention provides an etching method and an etching device for a silicon nitride thin film layer, including the following steps: providing a substrate with a silicon nitride thin film layer on its surface; placing the substrate in an etching tank containing a phosphoric acid etching solution to remove the silicon nitride thin film layer. Among them, a bubble generating device is arranged in the etching tank. During the etching process of the silicon nitride thin film layer, the bubble generating device introduces micro-nano bubbles into the phosphoric acid etching solution to initiate micro-turbulence in the phosphoric acid etching solution to promote etching uniformity. The micro-nano bubbles burst on the surface of the silicon nitride thin film layer to generate local pressure to enhance the etching reaction. Based on the synergistic effect of micro-nano bubbles and phosphoric acid etching solution, the present invention realizes the efficient removal of the silicon nitride thin film layer. Compared with the traditional etching process, the etching rate of the silicon nitride thin film layer in the present invention is increased by more than 30%, and the etching uniformity is greatly optimized, and the etching selectivity for the silicon nitride thin film layer and the oxide thin film layer is significantly improved. At the same time, due to the introduction of micro-nano bubbles, the consumption of chemicals is significantly reduced, effectively reducing the production cost and environmental burden. In addition, by optimizing the process steps and the temperature and composition ratio of the phosphoric acid etching solution, the present invention effectively reduces particle contamination and chemical residues. The method of the present invention is efficient, reliable, low-cost and easy to operate, and has wide applicability and application value. Description of the Drawings

[0028] Figure 1 It shows a schematic diagram when a low water content interface layer is formed in the area near the surface of the silicon nitride thin film layer during the removal of the silicon nitride thin film layer by the hot phosphoric acid wet etching process in the prior art.

[0029] Figure 2 It shows a process flow chart of the etching method for the silicon nitride thin film layer of the present invention.

[0030] Figure 3 It shows a schematic cross-sectional structure diagram of the etching device of the present invention.

[0031] Figure 4 It shows a three-dimensional view of the etching device of the present invention.

[0032] Element Number Description

[0033] 10 Substrate

[0034] 20 Etching groove

[0035] 30 Flow equalizing plate

[0036] 301 Plate body

[0037] 302 Through hole

[0038] 40 Bubble generating device

[0039] 50 Bracket

[0040] Steps S1 to S2 Specific implementation manner

[0041] 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.

[0042] Please refer to Figures 1 to 4 . It should be noted that the drawings 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 drawings, rather than being drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and ratio of each component in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0043] This embodiment provides an etching method for a silicon nitride thin film layer. Please refer to Figure 2 , which shows the flowchart of this method, including the following steps:

[0044] S1: Provide a substrate, and a silicon nitride thin film layer is provided on the surface of the substrate;

[0045] S2: Place the substrate in an etching groove containing a phosphoric acid etching solution to remove the silicon nitride thin film layer. Among them, a bubble generating device is provided in the etching groove, and the bubble generating device introduces micro-nano bubbles into the phosphoric acid etching solution during the etching process of the silicon nitride thin film layer to initiate micro-turbulence in the phosphoric acid etching solution to promote etching uniformity, and the micro-nano bubbles burst on the surface of the silicon nitride thin film layer to generate local pressure to enhance the etching reaction.

[0046] First, execute step S1: Provide a substrate, and a silicon nitride thin film layer is provided on the surface of the substrate.

[0047] Specifically, the substrate includes a silicon substrate, a silicon-germanium substrate, a silicon carbide substrate, an SOI (silicon-on-insulator) substrate, a GOI (germanium-on-insulator) substrate, a sapphire substrate, a gallium nitride substrate, a gallium arsenide substrate, a glass substrate, a plastic substrate, or a substrate of other suitable materials.

[0048] As an example, one or more intermediate layers are formed on the substrate, and the silicon-based nitride thin film layer is located on the one or more intermediate layers, or at least partially embedded in one or more of the intermediate layers (i.e., the silicon-based nitride thin film layer is partially or fully embedded in the intermediate layer).

[0049] As an example, the intermediate layer includes, but is not limited to, a conductor layer, a semiconductor layer, an insulating layer, or other functional material layers.

[0050] Specifically, the conductor layer includes a metal layer (such as an aluminum layer, a copper layer, a tungsten layer) or other material layers with conductive properties; the semiconductor layer includes a polysilicon layer, a gallium nitride layer, or other material layers with semiconductor characteristics; the insulating layer includes a silicon oxide layer, a titanium oxide layer, a silicon nitride layer, an aluminum nitride layer, or other material layers with insulating properties. In addition, the intermediate layer may also include a polymer layer, a composite material layer, or other functional layers to meet different application requirements.

[0051] As an example, the silicon-based nitride thin film layer includes a silicon nitride layer or a silicon oxynitride layer. In this embodiment, the silicon-based nitride thin film layer is preferably a silicon nitride layer.

[0052] Specifically, in the process flow of device manufacturing, some silicon-based nitride thin film layers used as barrier layers, hard mask layers, or protective layers need to be selectively removed to complete the final structure and function of the device. The specific position and removal timing of the silicon-based nitride thin film layer in the device structure depend on the type and process requirements of the device being manufactured. For example, in MOS devices, the silicon-based nitride thin film layer is usually deposited on the gate dielectric layer as a hard mask layer for pattern transfer, and after pattern formation, the silicon-based nitride thin film layer needs to be removed to expose the underlying material layer (such as the gate dielectric layer or other functional layers); in memory devices (such as 3D NAND or DRAM), the silicon-based nitride thin film layer usually covers the conductive layer, and after completing structure definition or via etching, the silicon-based nitride thin film layer needs to be selectively removed to expose the underlying conductive layer or dielectric layer for subsequent metal interconnect, oxide deposition, and other process steps. It should be noted that the specific position and structural form of the silicon-based nitride thin film layer on the substrate in this embodiment can be flexibly adjusted according to the requirements of different devices and are not specifically limited here.

[0053] Please perform the step S2 again: Place the substrate in an etching tank containing a phosphoric acid etching solution to remove the silicon nitride thin film layer. Among them, a bubble generating device is provided in the etching tank, and the bubble generating device introduces micro-nano bubbles into the phosphoric acid etching solution during the etching process of the silicon nitride thin film layer to initiate micro-turbulence in the phosphoric acid etching solution to promote etching uniformity. The micro-nano bubbles burst on the surface of the silicon nitride thin film layer to generate local pressure to enhance the etching reaction.

[0054] Specifically, during the etching process, the micro-turbulence initiated by the micro-nano bubbles in the phosphoric acid etching solution not only promotes the flow of the phosphoric acid etching solution, effectively disperses the phosphoric acid etching solution, but also eliminates the concentration gradient of high water content and low water content formed near the surface of the silicon nitride thin film layer due to the consumption of water molecules, thereby significantly improving the etching uniformity and increasing the etching rate. Especially when etching the silicon nitride thin film layer on a complex graphic structure or a high aspect ratio structure, this micro-turbulence can effectively avoid the formation of a stationary area or an etching dead angle on the surface of the silicon nitride thin film layer, thereby ensuring the etching uniformity and improving the etching quality. At the same time, the introduction of the micro-nano bubbles can effectively reduce the thickness of the boundary layer formed by the phosphoric acid etching solution on the surface of the silicon nitride thin film layer. The reduction of this boundary layer thickness means that the phosphoric acid etching solution can reach the surface of the silicon nitride thin film layer more efficiently for reaction, thereby further enhancing the etching rate. In addition, the local high pressure generated instantaneously when the micro-nano bubbles burst can enhance the impact force of the phosphoric acid etching solution on the silicon nitride thin film layer, accelerate the progress of the chemical reaction, and thus effectively promote the removal of the silicon nitride thin film layer.

[0055] As an example, before placing the substrate in the etching tank containing the phosphoric acid etching solution, it further includes the step of pre-cleaning the substrate with a first cleaning solution to remove the thin oxide film that may be generated on the surface of the silicon nitride thin film layer.

[0056] Specifically, when the silicon nitride thin film layer is exposed to air or other oxidation environments, its surface is prone to oxidation and generates a thin oxide film. And this thin oxide film will cause the uneven contact between the phosphoric acid etching solution and the silicon nitride thin film layer during the subsequent etching process, affecting the etching rate and etching effect. Therefore, before etching with the phosphoric acid etching solution, it is necessary to pre-clean the substrate with the first cleaning solution.

[0057] As an example, the first cleaning solution includes DHF (diluted hydrofluoric acid solution), and during the pre-cleaning process, the temperature range of the first cleaning solution is 20 - 30 °C. In this embodiment, the temperature of the first cleaning solution is preferably 23 °C.

[0058] Specifically, the pre-cleaning process in this embodiment includes the following steps: First, soak the substrate in a DHF solution at a temperature of 23°C for cleaning to remove the thin oxide film on the surface of the silicon nitride thin film layer. Subsequently, rinse the substrate with deionized water (DIW) to remove the residual DHF solution and avoid adverse effects of the residual DHF solution on the subsequent etching process. Through the pre-cleaning step, the interference of the oxide film on the surface of the silicon nitride thin film layer to the subsequent etching process can be eliminated, ensuring the smooth progress of the subsequent etching and improving the overall etching quality.

[0059] As an example, the phosphoric acid etching solution is prepared by mixing concentrated phosphoric acid with a mass fraction of 70% - 98% and deionized water in a preset ratio. During the etching process, the temperature of the phosphoric acid etching solution is controlled within the range of 150 - 180°C.

[0060] Specifically, in this embodiment, it is preferred to mix concentrated phosphoric acid with a mass fraction of 85% and deionized water to prepare the phosphoric acid etching solution, wherein the volume ratio of the deionized water is controlled between 15% and 20%.

[0061] Specifically, in this embodiment, the temperature of the phosphoric acid etching solution is preferably 160°C.

[0062] Specifically, the etching time is determined according to the thickness of the silicon nitride thin film layer. For example, in some examples, the etching time range can be 60 - 120 s, or it can be 1 - 10 minutes. It can be specifically adjusted and optimized according to actual needs and is not specifically limited here.

[0063] As an example, the diameter range of the micro-nano bubbles is 1 - 200 nanometers, and the micro-nano bubbles include but are not limited to at least one of nitrogen bubbles, helium bubbles, and argon bubbles.

[0064] As an example, the concentration range of the micro-nano bubbles in the phosphoric acid etching solution is 10 7 ~10 8 per mL.

[0065] Specifically, the smaller the diameter of the micro-nano bubbles introduced into the phosphoric acid etching solution, the greater the internal pressure generated by their surface tension, and the stronger the instantaneous high pressure released during rupture. The strong impact force generated by this instantaneous high pressure and the micro-turbulence induced by the micro-nano bubbles in the phosphoric acid etching solution can significantly enhance the interaction between the phosphoric acid etching solution and the silicon nitride thin film layer, accelerate the etching reaction process, and thus effectively improve the efficiency of removing the silicon nitride thin film layer. However, to achieve efficient etching while ensuring no damage to other material layers and protecting the integrity of the device structure, the diameter of the micro-nano bubbles should be controlled within the range of 1 to 200 nanometers. Within this size range, the instantaneous high pressure when the micro-nano bubbles rupture can efficiently and precisely remove the silicon nitride thin film layer, while effectively avoiding damage or destruction to other materials and structural layers (such as intermediate layers, etc.) on the substrate. This can not only improve the reliability and controllability of the etching process, but also effectively ensure the integrity and functional stability of the device structure. In addition, inert micro-nano bubbles such as nitrogen bubbles, helium bubbles, or argon bubbles with high concentration and high specific surface area have high solubility in the phosphoric acid etching solution. When these micro-nano bubbles enter the phosphoric acid etching solution, they can effectively reduce the oxygen content in the phosphoric acid etching solution, inhibit the occurrence of oxidation side reactions, and avoid the formation of an oxide layer on the surface of the silicon nitride thin film layer, thereby effectively reducing problems such as etching non-uniformity caused by the oxide layer. Moreover, when the micro-nano bubbles rupture, they release highly chemically active free radicals (such as hydroxyl radicals), which can efficiently decompose and etch organic pollutants or fine particles remaining during the etching of the silicon nitride thin film layer, thereby further cleaning the substrate surface and reducing the impact on subsequent process steps (such as deposition, lithography).

[0066] As an example, the phosphoric acid etching solution further includes a stabilizer, and the stabilizer includes boric acid, phosphate, or other additives with stabilizing properties. By adding an appropriate amount of stabilizer, problems such as possible decomposition or solution non-uniformity during the etching process of the phosphoric acid etching solution can be effectively reduced, thereby improving the stability of the phosphoric acid etching solution, extending its service life, and significantly improving the consistency and controllability of the etching effect.

[0067] As an example, the substrate is immersed vertically in the phosphoric acid etching solution in the etching tank.

[0068] Specifically, immersing the substrate in a vertical state in the phosphoric acid etching solution in the etching tank can not only enable the phosphoric acid etching solution to uniformly cover the surface of the silicon nitride thin film layer and continuously react, but also effectively avoid the problems of the accumulation of the phosphoric acid etching solution or the retention of micro-nano bubbles caused by gravity, thereby significantly enhancing the etching uniformity. In addition, it can also significantly reduce the attachment of particles or residues during the etching process, thereby reducing the risk of contamination of the substrate surface.

[0069] As an example, the substrate is placed on a bracket and immersed in the phosphoric acid etching solution in the etching tank in a vertical state, and multiple substrates can be placed on the bracket at the same time.

[0070] Specifically, the substrate is fixed to the bracket by a clamping structure or a card slot. The bracket adopts a layered or grid structure to achieve stable fixation and uniform arrangement of multiple substrates, ensuring that the surface of each substrate is covered by the phosphoric acid etching solution during the etching process, and effectively avoiding the problem of inconsistent etching caused by uneven spacing.

[0071] As an example, the silicon nitride thin film layer is used as a masking layer during the formation of a shallow trench isolation (STI) structure, a local oxidation of silicon (LOCOS) isolation structure, or a self-aligned contact (SAC) structure.

[0072] Specifically, when forming the STI structure, the silicon nitride thin film layer is used as a masking layer for the trench area, which can define the etching range of the trench. By etching the silicon nitride thin film layer, the trench area is exposed, and then an oxide can be filled in the trench to achieve the electrical isolation function; when forming the LOCOS isolation structure, the silicon nitride thin film layer can be used as a masking layer for protecting the non-isolated area during the thermal oxidation process. After the oxidation process is completed, the silicon nitride thin film layer can be removed by the etching method to facilitate the subsequent process steps; when forming the SAC structure, the silicon nitride thin film layer is used as a masking layer to protect the conductive material (such as polysilicon, metal layer, etc.) from diffusion or oxidation during the subsequent process, and the silicon nitride thin film layer can be removed by the etching method in the subsequent process of forming the contact structure. The etching method of this embodiment can accurately remove the silicon nitride thin film layer used as a masking layer during the formation of the STI structure, the LOCOS isolation structure, or the SAC structure, and will not damage the intermediate layer (such as a conductor layer, a semiconductor layer, or an insulating layer) at the bottom of the silicon nitride thin film layer, having high etching selectivity, excellent etching uniformity, and wide process adaptability.

[0073] As an example, when the intermediate layer includes an insulating layer, the silicon-based nitride thin film layer is located on the surface of the insulating layer, and the insulating layer is a silicon oxide layer and the silicon-based nitride thin film layer is a silicon nitride layer, the etching selectivity of the etching method for the silicon nitride layer and the silicon oxide layer is not less than 78:1, where the temperature of the phosphoric acid etching solution is 160°C.

[0074] Specifically, in this embodiment, by introducing micro-nano bubbles into the phosphoric acid etching solution to etch the silicon-based nitride thin film layer (silicon nitride layer), the etching selectivity of the phosphoric acid etching solution for the silicon-based nitride thin film layer (silicon nitride layer) and the oxide thin film layer (i.e., silicon oxide layer) is not less than 78:1 at a temperature of 160°C. This shows that the etching method can not only effectively improve the etching selectivity, reduce the generation of etching defects, but also significantly improve the etching efficiency and etching accuracy, thereby effectively improving the etching quality.

[0075] As an example, after removing the silicon-based nitride thin film layer, the following steps are further included:

[0076] (1) Place the substrate in a hot water bath for cleaning to remove the residual phosphoric acid etching solution on the surface of the substrate;

[0077] (2) Place the substrate in a cleaning tank and clean the substrate with a second cleaning solution;

[0078] (3) Perform a drying treatment on the surface of the substrate.

[0079] Specifically, in this embodiment, the substrate is placed in a hot water bath at a temperature of 60-70°C and cleaned with deionized water for a cleaning time of 60-120 s. Any one of rapid drainage cleaning, overflow cleaning, or water spray drainage cleaning can be selected during cleaning. In this embodiment, rapid drainage cleaning is preferably used, that is, the substrate is immersed in the hot water bath, the water in the water bath is quickly drained, then the drain valve is closed and new water is replenished, and the water bath is drained again after it is refilled, repeating this process three times (i.e., fast forward and fast drain three times). This fast forward and fast drain cleaning method can effectively remove the residual phosphoric acid etching solution on the surface of the substrate through the operation of rapid discharge and water replenishment cycles, avoid the influence of the residual liquid on subsequent processes, ensure the cleaning uniformity and efficiency, and improve the cleaning effect.

[0080] As an example, the second cleaning solution includes at least one of SC1 (a mixed solution of ammonia water, hydrogen peroxide, and water), SC2 (a mixed solution of hydrochloric acid, hydrogen peroxide, and water), and SPM (a mixed solution of sulfuric acid and hydrogen peroxide). That is, a single second cleaning solution can be used to clean the substrate once, or two or more of the second cleaning solutions can be used to clean the substrate in sequence to remove the particulate matter or impurities remaining during the removal of the silicon nitride thin film layer. At the same time, ultrasonic-assisted cleaning can be introduced during the cleaning process to enhance the particulate removal effect.

[0081] As an example, before the drying treatment, it also includes the step of cleaning the surface of the substrate with deionized water.

[0082] Specifically, in this embodiment, the substrate is placed in a deionized water tank at a temperature of 25 °C for cleaning to remove the residue of the second cleaning solution on the surface of the substrate.

[0083] As an example, the Marangoni drying method or the hot nitrogen drying method is used to dry the surface of the substrate.

[0084] Specifically, when using the Marangoni drying method to dry the surface of the substrate, the cleaned substrate is slowly lifted upward (or by slowly draining the water), so that the surface of the substrate gradually separates from the liquid surface. During this process, through the gradient action of the surface tension of the solvent, Marangoni convection is formed, thereby uniformly removing the liquid residue and achieving efficient drying.

[0085] Specifically, when using the hot nitrogen drying method to dry the surface of the substrate, under the temperature condition of 70-90 °C, high-purity hot nitrogen is used to blow and heat the surface of the substrate, and the high-temperature nitrogen realizes uniform drying by quickly evaporating the liquid remaining on the surface of the substrate.

[0086] This embodiment also provides an etching device, such as Figure 3 and Figure 4As shown, the etching equipment is used to etch the silicon nitride thin film layer described above. The etching equipment includes an etching tank 20, a flow equalizing plate 30, and a bubble generating device 40. Among them, the etching tank 20 is used to hold the etching solution, and an etching solution inlet (not shown) and a liquid discharge outlet (not shown) are provided in the etching tank 20; the flow equalizing plate 30 is located between the notch of the etching tank 20 and the etching solution inlet. The flow equalizing plate 30 includes a plate body 301 and a plurality of through holes 302 penetrating the plate body 301. The through holes 302 are used to disperse the etching solution and micro-nano bubbles; the bubble generating device 40 is arranged in the etching tank 20 and below the flow equalizing plate 30. The bubble generating device 40 is connected to an external gas source supply system (not shown) to generate micro-nano bubbles, and a flow regulating valve (not shown) and a power regulating device (not shown) are arranged between the bubble generating device 40 and the gas source supply system. The flow regulating valve and the power regulating device are used to control the generation frequency and size of the micro-nano bubbles.

[0087] Specifically, the bubble generating device 40 is a micro-nano bubble generating device based on the high-shear principle. This device adopts a dynamic or static high-speed shearing mechanism. Through an efficient shearing process, the size of the bubbles is accurately reduced to the range of a few nanometers to a few micrometers, thereby generating stable micro-nano bubbles.

[0088] It should be noted that Figure 3 The arrows shown in are only used to indicate the flow of the etching solution in the etching tank 20, but do not specifically indicate the flow direction of the etching solution. The actual flow direction of the etching solution varies due to various factors such as the introduction of the micro-nano bubbles and the setting of the etching tank 20. Therefore, the arrows are only for indication and cannot indicate its inevitable flow situation of the etching solution.

[0089] As an example, the etching tank 20 further includes a temperature control module (not shown), and the temperature control module is used to control the temperature of the etching solution.

[0090] As an example, the gas supplied by the gas source supply system includes at least one of nitrogen, helium, and argon.

[0091] As an example, the rate of injecting gas by the gas source supply system is 2-10 L / min.

[0092] Specifically, a higher gas injection efficiency can increase the number of bubbles generated per unit time, thereby significantly increasing the concentration of micro-nano bubbles in the phosphoric acid etching solution. And the high-concentration micro-nano bubbles can effectively enhance the reaction activity of the phosphoric acid etching solution, promote diffusion and the etching reaction, thereby improving the etching rate.

[0093] As an example, a bracket 50 is further provided in the etching tank 20. The bracket 50 is located above the flow equalizing plate 30 and is used to carry the substrate 10.

[0094] Specifically, the substrate 10 is fixed to the bracket 50 through a clamping structure or a card slot. The bracket 50 adopts a layered or grid-like structure to achieve stable fixation and uniform arrangement of multiple substrates 10.

[0095] As an example, the substrate 10 is placed vertically on the bracket and immersed in the etching tank 20 in a vertical state.

[0096] In summary, the present invention provides an etching method and an etching device for a silicon nitride thin film layer, including the following steps: providing a substrate with a silicon nitride thin film layer on its surface; placing the substrate in an etching tank containing a phosphoric acid etching solution to remove the silicon nitride thin film layer. Among them, a bubble generating device is provided in the etching tank. During the etching process of the silicon nitride thin film layer, the bubble generating device introduces micro-nano bubbles into the phosphoric acid etching solution to initiate micro-turbulence in the phosphoric acid etching solution to promote etching uniformity. The micro-nano bubbles burst on the surface of the silicon nitride thin film layer to generate local pressure to enhance the etching reaction. Based on the synergistic effect of micro-nano bubbles and phosphoric acid etching solution, the present invention realizes the efficient removal of the silicon nitride thin film layer. Compared with the traditional etching process, the etching rate of the silicon nitride thin film layer in the present invention is increased by more than 30%, and the etching uniformity is greatly optimized, and the etching selectivity for the silicon nitride thin film layer and the oxide thin film layer is significantly improved. At the same time, due to the introduction of micro-nano bubbles, the usage of chemicals is significantly reduced, effectively reducing the production cost and environmental burden. In addition, by optimizing the process steps and the temperature and composition ratio of the phosphoric acid etching solution, the present invention effectively reduces particle contamination and chemical residues. The method of the present invention is efficient, reliable, low-cost and easy to operate, and has wide applicability and application value. Therefore, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0097] The above embodiments are only illustrative of the principles and effects of the present invention, and are not used 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 method for etching a silicon-based nitride thin film layer, characterized in that: The following steps are involved: Providing a substrate, wherein the surface of the substrate has a silicon-based nitride thin film layer; The substrate is placed in an etching tank containing a phosphoric acid etching solution to remove the silicon-based nitride film layer, wherein a bubble generating device is provided in the etching tank, and the bubble generating device introduces micro-nano bubbles into the phosphoric acid etching solution during the etching process of the silicon-based nitride film layer to induce micro-turbulence in the phosphoric acid etching solution to promote etching uniformity, and the micro-nano bubbles burst on the surface of the silicon-based nitride film layer to generate local pressure to enhance the etching reaction.

2. The method for etching a silicon-based nitride thin film layer according to claim 1, characterized in that: The diameter of the micro-nano bubbles ranges from 1 to 200 nanometers, and the micro-nano bubbles include at least one of nitrogen bubbles, helium bubbles and argon bubbles.

3. The method for etching a silicon-based nitride thin film layer according to claim 1, characterized in that: The phosphoric acid etching solution is prepared by mixing concentrated phosphoric acid with a mass fraction of 70% to 98% and deionized water in a preset ratio. During the etching process, the temperature of the phosphoric acid etching solution is controlled within the range of 150 to 180° C., and the concentration range of the micro-nano bubbles in the phosphoric acid etching solution is 10 7 ~10 8 Pieces / mL.

4. The method for etching a silicon-based nitride thin film layer according to claim 3, characterized in that: The phosphoric acid etching solution also includes a stabilizer, and the stabilizer includes boric acid.

5. The method for etching a silicon-based nitride thin film layer according to claim 1, characterized in that: The silicon-based nitride thin film layer includes a silicon nitride layer or a silicon nitride oxide layer.

6. The method for etching a silicon-based nitride thin film layer according to claim 1, characterized in that: Before placing the substrate in the etching tank containing the phosphoric acid etching solution, the method further includes a step of pre-cleaning the substrate with a first cleaning solution.

7. The method for etching a silicon-based nitride thin film layer according to claim 1, characterized in that: The silicon-based nitride film layer is used as a masking layer in the process of forming a shallow trench isolation structure, a local silicon oxide isolation structure or a self-aligned contact structure.

8. The method for etching a silicon-based nitride thin film layer according to claim 1, characterized in that: After removing the silicon-based nitride film layer, the method further comprises the following steps: Placing the substrate in a hot water tank for cleaning to remove the phosphoric acid etching solution remaining on the surface of the substrate; Placing the substrate in a cleaning tank and cleaning the substrate with a second cleaning solution; The surface of the substrate is dried.

9. An etching device, used for etching the silicon-based nitride thin film layer according to any one of claims 1 to 8, characterized in that: include: An etching tank, used for containing etching liquid, wherein the etching tank is provided with an etching liquid inlet and a liquid discharge outlet; A flow-distributing plate, located between the notch of the etching groove and the etching liquid inlet, the flow-distributing plate comprises a plate body and a plurality of through holes penetrating the plate body, the through holes being used to disperse the etching liquid and micro-nano bubbles; A bubble generating device is arranged in the etching groove and below the flow equalizing plate. The bubble generating device is connected to an external gas source supply system to generate micro-nano bubbles. A flow regulating valve and a power regulating device are arranged between the bubble generating device and the gas source supply system. The flow regulating valve and the power regulating device are used to control the generation frequency and size of the micro-nano bubbles.

10. The etching device according to claim 9, characterized in that: The etching tank also includes a temperature control module, and the temperature control module is used to control the temperature of the etching solution.

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