Wet etching method and equipment for high aspect ratio structure

Abstract

The invention discloses a wet etching method and equipment for a high aspect ratio structure, and the etching method comprises the steps: 1, providing a wafer after photoetching development, and carrying out the plasma processing of the surface of the wafer; 2, horizontally placing the long and deep grooves to be etched on the treated wafer in a soaking tank, and performing wet etching treatment on the wafer to enable the flowing direction of etching liquid to form an inclination angle of 20-45 degrees with the surface of the wafer; and step 3, after etching is completed, cleaning and drying the wafer. According to the method, the plasma processing step is added before wet etching, the hydrophilicity of the etching surface is improved, the wettability of the etching liquid on the material surface is remarkably improved, the flowing path of the etching liquid is changed by adjusting the flowing direction of the etching liquid and the inclination angle of the wafer surface, and the etching uniformity is ensured.

Description

Technical Field

[0001] The present invention relates to the field of process manufacturing of semiconductor integrated circuits and micro-electromechanical systems, and in particular to a high aspect ratio structure wet etching method and equipment. Background Art

[0002] In the MEMS manufacturing process, wet etching is a commonly used process, especially in the etching of high-aspect-ratio structures. However, the wettability of the etching solution on the material surface has a significant impact on the etching effect. If the etching solution cannot spread well on the material surface and fully contact it, it will lead to uneven etching, affecting the performance and yield of the product. When wet etching high-aspect-ratio structures (such as deep holes and narrow grooves), the etching solution is difficult to completely penetrate due to surface tension, resulting in residual etched film. At the same time, etching produces a large number of bubbles (such as hydrogen or reaction byproducts), which will hinder the contact between the etching solution and the film layer, forming an etching blind area and affecting device performance.

[0003] Furthermore, traditional wet etching tools use vertical or fixed-angle injection, resulting in low flow rates and poor exchange efficiency at the bottom of deep trenches, which can easily lead to the accumulation of etching byproducts. Existing improvements focus on optimizing the chemical composition or using ultrasonic assistance, but these solutions present challenges such as high costs and structural damage.

[0004] Based on this, the present invention provides a high aspect ratio structure wet etching method and equipment, which effectively improves etching uniformity, reduces film residue, and is suitable for the manufacture of high aspect ratio structure MEMS devices. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a high aspect ratio structure wet etching method, which solves the problem of film residue during the high aspect ratio structure wet etching process, effectively provides etching uniformity, and is suitable for the manufacture of high aspect ratio structure MEMS devices.

[0006] The present invention provides a wet etching method for a high aspect ratio structure, comprising the following steps:

[0007] Step 1: providing a wafer after photolithography and development, and performing plasma treatment on the surface of the wafer;

[0008] Step 2: placing the long and deep groove to be etched on the processed wafer horizontally in an immersion tank, and performing wet etching on the wafer, so that the flow direction of the etching solution is inclined at an angle of 20° to 45° with the wafer surface;

[0009] Step 3: After etching is completed, clean and dry the wafer.

[0010] In existing wet etching processes, wet etching is typically performed directly after photolithography development. This makes it difficult for the chemical solution to quickly penetrate the etched surface, resulting in uneven etching. Furthermore, for high-aspect-ratio wafer structures, the etching process generates a large amount of reactive gas that is blocked on the etched surface, further exacerbating the problem of film residue. The present invention adds a plasma treatment step before wet etching to increase the hydrophilicity of the etched surface, significantly improving the wettability of the etching solution on the material surface. Furthermore, by adjusting the inclination angle between the etching solution and the wafer surface, the etching solution flow path is changed to ensure etching uniformity.

[0011] In step 2, the tilt angle is 30° to 40°. For etching structures with high aspect ratios, the etching liquid is placed at a certain angle to the surface to be etched, ensuring that the surface is evenly covered with the etching liquid. At the same time, the etching liquid needs to have a certain impact force. Setting the tilt angle at 30° to 40° can help the etching liquid penetrate into pores or deep areas, accelerating the etching reaction while preventing the etching liquid from splashing and avoiding damage to the structure.

[0012] In step 2, the etched surfaces of the wafers are placed face to face. The present invention optimizes the placement of the etched surfaces of the wafers, changing the original uniform placement to face to face placement, so that the reaction gases generated between the etched surfaces can collide with each other, reducing the formation of bubbles.

[0013] In the step 1, the plasma treatment is oxygen plasma etching.

[0014] The second step also includes lifting the wafer up and down during the etching process. Lifting the immersion tank up and down increases the flow of reactive bubbles, which are more easily volatilized on the sidewalls of the deep trench of the wafer under the action of the up and down lifting, further reducing the possibility of film residue.

[0015] The present invention also provides a high aspect ratio structure wet etching device, comprising:

[0016] An etching tank for containing etching liquid, wherein the etching tank is provided with a soaking tank for placing the wafer to be etched;

[0017] A liquid inlet device, comprising a plurality of liquid inlet pipes, wherein the liquid inlet ends of the liquid inlet pipes are connected to the bottom of the etching tank;

[0018] An angle adjustment device is provided at the liquid inlet end of the liquid infusion pipeline and includes a plurality of liquid inlet nozzles with adjustable angles;

[0019] A reaction monitoring device, disposed above the etching tank, for monitoring the etching process;

[0020] The control system receives feedback data from the reaction monitoring device and controls the angle adjustment device to adjust the tilt angle between the etching liquid flow direction and the wafer surface.

[0021] Conventional wet etching equipment uses a vertical or fixed-angle etching solution injection method, resulting in low etching solution flow rate and poor exchange efficiency at the bottom of deep holes or narrow grooves in the wafer to be etched, which easily leads to the accumulation of etching byproducts. The etching equipment provided by the present invention, by providing an angle adjustment device, dynamically adjusts the inclination angle between the etching solution outlet direction and the etching surface according to the etching process. In other words, by changing the etching solution flow path, it can achieve efficient removal of residues at the bottom of high-aspect-ratio structures.

[0022] The liquid inlet nozzle includes a main nozzle and an auxiliary nozzle. The etching liquid in the main nozzle flows out along the inclined angle, and the auxiliary nozzle replenishes the etching liquid from the side. By combining the main nozzle and the auxiliary nozzle, a portion of the etching liquid is sprayed along the etching angle, while the other portion of the etching liquid is replenished from the side, forming a spiral fluid path that covers the sidewalls of the deep trench on the wafer, thereby improving etching uniformity.

[0023] The system also includes a lifting device that moves the immersion tank up and down. An adjustment module is provided at the movable end of the lifting device to fine-tune the angle of the immersion tank during its up and down movement. By providing a lifting device to lift the immersion tank up and down, the flow of reaction bubbles is increased, further reducing the possibility of film residue.

[0024] The wet etching equipment also includes a circulation pipeline and a power device. The liquid outlet end of the circulation pipeline is arranged at the upper part of the etching tank, and the liquid inlet end of the circulation pipeline is arranged at the bottom of the etching tank. The power device controls the etching liquid to circulate in the etching tank.

[0025] The beneficial effects of the present invention are:

[0026] (1) The etching method provided by the present invention adds a plasma treatment step before wet etching, which effectively improves the microstructure and chemical properties of the material surface, increases the hydrophilicity of the etched surface, and significantly improves the wettability of the etching solution on the material surface. In addition, by adjusting the inclination angle between the etching solution and the wafer surface, the flow path of the etching solution is changed to ensure etching uniformity.

[0027] (2) The etching equipment provided by the present invention adds a liquid infusion pipeline and sets an angle adjustment device at the liquid inlet end of the liquid infusion pipeline. It dynamically adjusts the inclination angle between the flow direction of the etching liquid and the wafer surface according to the etching process. That is, by changing the flow path of the etching liquid, it can achieve efficient removal of residues at the bottom of the high aspect ratio structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 This is a schematic flow chart of a high aspect ratio structure wet etching method provided by the present invention;

[0030] Figure 2 This is a schematic diagram of reaction bubbles when a long and deep groove to be etched on a wafer is placed vertically in the etching groove and pulled up and down in the prior art solution;

[0031] Figure 3 Schematic diagram of reaction bubbles in the state of pulling up and down when the long and deep groove to be etched on the wafer is horizontally placed in the etching groove in Example 1;

[0032] Figure 4 It is a schematic diagram of a wafer obtained after wet etching in the prior art;

[0033] Figure 5 Schematic diagram of a wafer obtained by using the wet etching method provided in Example 1;

[0034] Figure 6 This is a schematic structural diagram of a high aspect ratio structure wet etching device provided in Example 2;

[0035] Figure 7 Schematic diagram of the liquid inlet nozzle in Example 2 (top view);

[0036] Figure 8 This is a schematic diagram of the liquid delivery pipeline and liquid flow direction of traditional etching equipment;

[0037] Figure 9 This is a schematic diagram of the liquid delivery pipeline and liquid flow direction of the etching equipment provided in this embodiment 2.

[0038] 1. Etching tank; 101. Immersion tank; 2. Liquid inlet device; 201. Liquid delivery pipeline; 3. Angle adjustment device; 301. Liquid inlet nozzle; 4. Reaction monitoring device; 5. Lifting device; 6. Adjustment module; 7. Wafer to be etched; 8. Liquid level box; 9. Vibrator; 10. Circulation pipeline; 11. Power device. DETAILED DESCRIPTION

[0039] To make the objectives, technical solutions, and advantages of the present invention more apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. Examples of these preferred embodiments are illustrated in the accompanying drawings. The embodiments of the present invention shown in and described with reference to the accompanying drawings are merely exemplary, and the present invention is not limited to these embodiments.

[0040] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, the accompanying drawings only show structures and / or processing steps closely related to the solutions according to the present invention, while other details that are not closely related to the present invention are omitted.

[0041] Example 1

[0042] See also Figure 1 The present invention provides a high aspect ratio structure wet etching method, comprising the following steps:

[0043] Step 1: providing a wafer after photolithography and development, and performing plasma treatment on the surface of the wafer;

[0044] Step 2: placing the soaking tank containing the processed wafer horizontally in the etching tank, and performing wet etching on the wafer, so that the flow direction of the etching solution is inclined at an angle of 20° to 45° with the wafer surface;

[0045] Step 3: After etching is completed, clean and dry the wafer.

[0046] In this embodiment, the aspect ratio of the wafer film layer to be etched is 20:1.

[0047] In step 1, the plasma treatment process includes: placing the wafer to be etched in a vacuum chamber, introducing oxygen to make the air pressure in the chamber reach a set value, such as 0.1-10 Pa, turning on the plasma generator, and bombarding the surface of the material to be etched. The treatment time is 1 to 60 seconds and the power is 100 to 1000 watts.

[0048] In step 2, before etching, the etched surfaces of the wafers to be etched are placed face to face so that the reaction gases generated between the etched surfaces collide with each other, thereby reducing the formation of bubbles.

[0049] In step 2, the tilt angle is 30° to 40°. Meanwhile, the etching process in this step also includes lifting the immersion tank containing the wafer up and down to increase the flow of reaction bubbles and further reduce the possibility of film residue. Figure 2 This is a schematic diagram of reaction bubbles when a long and deep groove to be etched on a wafer is placed vertically in the etching groove and pulled up and down in the prior art. In this case, since the long and deep groove to be etched is long, the gases generated by the reaction are not easy to collide with each other, and the bubbles gather along the side walls of the long and deep groove to be etched, which easily causes film residue. Figure 3This is a schematic diagram of reaction bubbles when the long and deep groove to be etched on the wafer is placed horizontally in the etching groove and pulled up and down in this embodiment. Under the action of pulling up and down, the reaction bubbles can collide quickly and the gas can be easily volatilized.

[0050] In other embodiments, ultrasonic oscillation may be appropriately performed during the etching process to effectively remove reactants and increase etching uniformity.

[0051] like Figure 4 and Figure 5 As shown, Figure 4 This is a schematic diagram of a wafer obtained by wet etching using existing technology. It can be seen that there are metal residues in the etched area, the etching depth deviation is ±15%, the wafer test (CP) yield is low, and the reaction bubble coverage observed in the experiment is about 32%.

[0052] Figure 5 This is a schematic diagram of a wafer obtained using the etching method provided by this embodiment. During the etching process, the bubble coverage is ≤5%, the etching depth deviation is ±3%, there is no metal residue in the etched area, and the wafer test (CP) is improved.

[0053] Example 2

[0054] like Figure 6 and Figure 7 As shown, the present invention also provides a high aspect ratio structure wet etching device, comprising:

[0055] The etching tank 1 is used to hold the etching liquid. The etching tank 1 is provided with an immersion tank 101 for placing the wafer to be etched; a liquid inlet device 2, which includes multiple sets of liquid inlet pipes 201, the liquid inlet ends of the liquid inlet pipes 201 connected to the bottom of the etching tank 1; an angle adjustment device 3, provided at the liquid inlet end of the liquid inlet pipes 201, including multiple angle-adjustable liquid inlet nozzles 301; a reaction monitoring device 4, which is an observation window provided above the etching tank 1 and is used to monitor the changes in reaction bubbles during the etching process; a control system (not shown in the figure) receives feedback data from the reaction monitoring device and controls the angle adjustment device to adjust the inclination angle between the flow direction of the etching liquid and the surface of the wafer. Furthermore, the immersion tank can also be provided with a flow monitor for real-time monitoring of the flow of the etching liquid entering the immersion tank. The control system receives the flow signal and controls the angle adjustment device according to the flow signal to further adjust the inclination angle of the nozzle.

[0056] like Figure 8 As shown, the traditional liquid circulation pipeline is designed as a group of 2 rows. The dotted line in the figure indicates the flow direction of the etching liquid. In this embodiment, a three-group 6-row design is adopted (see Figure 9), the liquid inlet nozzles 301 at the liquid inlet end of the liquid delivery pipe 201 are arranged in an asymmetrical fan-shaped pattern, comprising a main nozzle and an auxiliary nozzle. The etching liquid in the main nozzle flows out along the inclined angle, while the auxiliary nozzle replenishes the etching liquid from the side. By combining the main and auxiliary nozzles, a portion of the etching liquid is sprayed along the etching angle, while another portion is replenished from the side, forming a spiral fluid path that covers the sidewalls of the deep trench on the wafer, thereby improving etching uniformity.

[0057] The system further includes a lifting device 5, which drives the immersion tank 101 to move up and down. The movable end of the lifting device 5 is provided with an adjustment module 6, which controls the angle of the immersion tank 101 to be fine-tuned during the upward and downward movement. By providing a lifting device to lift the immersion tank up and down, the flow of reaction bubbles is increased, further reducing the possibility of film residue.

[0058] The wet etching equipment also includes a circulation pipeline 10 and a power device 11. The liquid outlet end of the circulation pipeline 10 is arranged at the upper part of the etching tank 1, and the liquid inlet end of the circulation pipeline 10 is arranged at the bottom of the etching tank 1. The power device 11 is a pump body, which controls the circulation of the etching liquid in the etching tank.

[0059] In this embodiment, a plurality of vibrators 9 are further provided at the bottom of the immersion tank, and ultrasound is appropriately added to oscillate during etching to effectively remove reactants and increase etching uniformity.

[0060] In addition, it should be noted that, in this specification, "comprises," "includes," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0061] It should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A wet etching method for a high aspect ratio structure, characterized in that: The following steps are involved: Step 1: providing a wafer after photolithography and development, and performing plasma treatment on the surface of the wafer; Step 2: placing the long and deep groove to be etched on the processed wafer horizontally in an immersion tank, and performing wet etching on the wafer, so that the flow direction of the etching solution is inclined at an angle of 20° to 45° with the wafer surface; Step 3: After etching is completed, clean and dry the wafer.

2. A high aspect ratio structure wet etching method according to claim 1, characterized in that: In the step 2, the inclination angle is 30° to 40°.

3. The high aspect ratio structure wet etching method according to claim 1, characterized in that: In the step 2, the etched surfaces of the wafers are placed face to face.

4. The high aspect ratio structure wet etching method according to claim 1, characterized in that: In the step 1, the plasma treatment is oxygen plasma etching.

5. The high aspect ratio structure wet etching method according to claim 1, characterized in that: The step 2 also includes pulling the wafer up and down during the etching process.

6. A high aspect ratio structure wet etching device, characterized in that: include An etching tank for containing etching liquid, wherein the etching tank is provided with a soaking tank for placing the wafer to be etched; A liquid inlet device, comprising a plurality of liquid inlet pipes, wherein the liquid inlet ends of the liquid inlet pipes are connected to the bottom of the etching tank; An angle adjustment device is provided at the liquid inlet end of the liquid infusion pipeline and includes a plurality of liquid inlet nozzles with adjustable angles; A reaction monitoring device, disposed above the etching tank, for monitoring the etching process; The control system receives feedback data from the reaction monitoring device and controls the angle adjustment device to adjust the tilt angle between the etching liquid flow direction and the wafer surface.

7. The high aspect ratio structure etching equipment according to claim 6, characterized in that: The liquid inlet nozzle includes a main nozzle and an auxiliary nozzle. The etching liquid in the main nozzle flows out along the inclined angle, and the auxiliary nozzle replenishes the etching liquid from the side.

8. The high aspect ratio structure etching equipment according to claim 7, characterized in that: It also includes a lifting device, which drives the soaking tank to move up and down. The moving end of the lifting device is provided with an adjustment module, which controls the soaking tank to fine-tune the angle during the up and down movement.

9. The high aspect ratio structure etching equipment according to claim 6, characterized in that: It also includes a circulation pipeline and a power device, the liquid outlet end of the circulation pipeline is arranged at the upper part of the etching tank, the liquid inlet end of the circulation pipeline is arranged at the bottom of the etching tank, and the power device controls the etching liquid to circulate in the etching tank.

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