Convex corner protection technology during deep corrosion of silicon island

Abstract

The invention discloses a convex corner protection technology during deep corrosion of a silicon island. Each silicon island (4) adopts four lt; 110gt, 110gt; and the crystal orientation two-end clamped beam (5) and the two cantilever beams (6) form a convex angle protection pattern. Lt; 110gt, 110gt; and one end of the crystal orientation two-end clamped beam (5) is clamped on the frame (8), and the other clamped end of the crystal orientation two-end clamped beam (5) is connected with the free end of the cantilever beam (6). And the clamped end of the cantilever beam (6) is connected with the silicon island (4) and is as wide as the silicon island (4). The anisotropic corrosive liquid is firstly undercut; 110gt, 110gt; and beams (5) are clamped at two ends of the crystal orientation. Then, mask-free corrosion fault is carried out; 110gt, 110gt; a silicon wedge (9) below the beam (5) is clamped and supported at the two ends of the crystal orientation so as to obtain a flat corrosion surface, and at the same time, the corrosion liquid undercuts the cantilever beam (6) from the free end of the cantilever beam (6), 110gt, 110gt; the silicon wedges (9) below the clamped beams (5) at the two ends of the crystal orientation are completely corroded, the cantilever beam (6) is undercut when a flat corrosion surface is formed, and the part of the left silicon island (4) is not undercut. The convex angle protection pattern is small in occupied area, leads can be arranged on the convex angle protection pattern, and the convex angle protection pattern is particularly suitable for the condition that the silicon island (4) is small in size and close to the frame (8).

Description

Technical Field

[0001] This invention relates to a corner protection technology during the etching of silicon islands, particularly a corner protection technology for silicon island structures fabricated on silicon wafers using anisotropic deep etching processes, and belongs to the field of microelectromechanical systems (MEMS). Background Technology

[0002] Microelectromechanical systems (MEMS) refer to miniature devices or systems such as micro-sensors, micro-mechanisms, and micro-actuators, mass-produced using micromachining technology. They elevate the miniaturization, multifunctionality, intelligence, and reliability of information systems to new heights. Currently, MEMS products such as microsensors and micro-actuators are playing a significant role in fields such as industrial process control, communications, robotics, environmental protection and monitoring, human health, aircraft, automotive transportation, and agriculture.

[0003] Micromachining technology is a means of realizing various microstructures by absorbing and integrating other processing technologies on the basis of microelectronic manufacturing processes. Anisotropic wet etching is one of the core technologies of micromachining and is an important technology for manufacturing beams, diaphragms, nozzles, mesa, and other three-dimensional microstructures.

[0004] One problem with anisotropic wet etching is that undercutting occurs at convex corners when island-like structures (such as silicon mass blocks used in inertial sensors) are wet etched. To obtain perfect convex corner structures, various convex corner compensation patterns have been designed, such as squares, triangles, and superimposed squares. <100> Crystal orientation compensation strip, <110> Crystal orientation compensation strip, <110> Crystalline folding strips, etc. These compensation patterns surround the convex corner. During wet etching, the etchant undercuts the aforementioned convex corner compensation patterns according to a specific crystalline orientation. When the set etching depth is reached, the etching front just completes the undercut of the convex corner compensation patterns, resulting in a perfect convex corner structure.

[0005] However, when the island dimensions (length and width) are small and close to the frame, the above-mentioned compensation structure cannot achieve the purpose of convex corner compensation if a large corrosion depth is required. This is because square, triangular, and superimposed square structures are suitable for deep corrosion. <100> Compensation patterns such as crystal orientation compensation strips require a large area and cannot be placed on the convex corners of small silicon islands; while <110> Crystal orientation compensation strip, <110> Compensation patterns such as crystal orientation folding strips require a long length, but cannot be laid out due to the close proximity of silicon islands to the frame. Summary of the Invention

[0006] The purpose of this invention is to develop a convex corner protection technology for deep etching of silicon islands, which can achieve a perfect silicon island structure when the island size is small and the distance between it and the frame is close, thus enriching micromachining technology.

[0007] To achieve the objective of this invention, the technical solution adopted by this invention is: each silicon island (4) uses 4 strands <110> The convex corner protection pattern is formed by the fixed beams (5) at both ends of the crystal orientation and two cantilever beams (6). <110> One end of the crystal-oriented fixed beam (5) is fixed to the frame (8), and the other fixed end is connected to the free end of the cantilever beam (6). The fixed end of the cantilever beam (6) is connected to the silicon island (4), and its width is equal to the width of the silicon island (4).

[0008] The convex corner protection technology for deep-etched silicon islands provided by this invention includes the following two consecutive steps:

[0009] (1) In the first stage of corrosion, the corrosive liquid cuts to the bottom. <110> The two ends of the crystal orientation are fixed beam (5). When the etching depth is equal to b / 2λ, the two ends of the fixed beam (5) are released and suspended on the substrate. Where b is <110> The width of the beam (5) fixed at both ends of the crystal orientation, λ is the value of the corrosive liquid on the crystal. <110> The ratio of the transverse undercut rate of the crystal-directed end-fixed beam (5) to the longitudinal etching rate of the silicon (100) surface.

[0010] (2) In the second stage of corrosion, anisotropic corrosive liquid undergoes unmasked corrosion. <110> Silicon wedges (9) are fixed below the cantilever beams (5) at both ends of the crystal orientation to obtain a flat etching surface; at the same time, the etching solution begins to undercut the cantilever beam (6) from the free end of the cantilever beam (6). When <110> When the silicon wedge (9) under the fixed beam (5) at both ends of the crystal orientation is completely corroded and a flat corrosion surface is formed, the cantilever beam (6) is undercut, leaving the silicon island (4) part uncut.

[0011] The convex corner protection technology for deep etching of silicon islands involved in this invention has the following advantages: the convex corner protection pattern occupies a small area, and leads can be laid on the convex corner protection pattern. Attached Figure Description

[0012] Figure 1 This is the convex corner protection pattern for deep etching of silicon islands involved in this invention.

[0013] Figure 2 This is a process flow diagram of the silicon island structure etching process as an embodiment of the present invention.

[0014] In the attached image:

[0015] 1-Silicon wafer 2-Silicon dioxide thin film

[0016] 3-Silicon nitride thin film 4-Silicon island

[0017] 5- <110> Crystal-oriented fixed-end beam 6-cantilever beam

[0018] 7-Forming groove 8-Frame

[0019] 9-Silicon Wedge Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments, but is not limited to these embodiments.

[0021] Example: The silicon island structure was fabricated using the convex corner protection technology for deep etching of silicon islands provided by this invention. The fabrication process is as follows:

[0022] 1. The original silicon wafer is a (100)-sided silicon wafer with a resistivity of 0.015 Ω·cm (1). Standard cleaning, as shown in the attached document. Figure 2 As shown in [1].

[0023] 2. Silicon dioxide thin film (2) was grown by thermal oxidation at 1100℃, with a thickness of 0.65μm, as shown in the attached figure. Figure 2 As shown in [2].

[0024] 3. Deposit silicon nitride thin film (3) with a thickness of 0.2 μm by low-pressure chemical vapor deposition, as shown in the attached figure. Figure 2 As shown in [3].

[0025] 4. Photolithographic silicon island (4) and for protecting protruding corners <110> The crystal-oriented fixed beam (5) and cantilever beam (6) patterns are used to sequentially etch the silicon nitride film (3) and silicon dioxide film (2) in the forming groove (7), while retaining the silicon island (4). <110> The silicon dioxide film (2) and silicon nitride film (3) on the crystal-oriented fixed beam (5), cantilever beam (6) pattern, and frame (8). Among them: <110> The beams (5) with fixed ends in the crystal orientation have a width of 24.5 micrometers, the cantilever beams (6) and silicon islands (4) have a width of 100 micrometers, and the total length is 1444 micrometers, as shown in the attached figure. Figure 2 As shown in [4].

[0026] 5. Etching silicon in a 25% tetramethylammonium hydroxide (TMAH) solution at 80℃, simultaneously etching silicon longitudinally along the (100) plane and undercutting it laterally along the (111) plane. <110> The beams are fixed at both ends of the crystal orientation (5). The ratio of the transverse corrosion rate to the longitudinal corrosion rate, corresponding to the resistivity of the silicon wafer, the concentration of the etchant, and the temperature, is λ = 9%. When the corrosion depth is equal to 136 micrometers... <110> The crystal-oriented fixed beams (5) at both ends are released, as shown in the attached figure. Figure 2 As shown in [5].

[0027] 6. Continue maskless etching at 80℃ and 25% TMAH. <110> The silicon wedge (9) is fixed at both ends of the crystal-oriented beam (5), while the cantilever beam is undercut. When the etching depth is equal to 90 micrometers... <110> The silicon wedge (9) under the fixed beams (5) at both ends of the crystal orientation is completely etched, and the cantilever beams (6) on both sides of the silicon island (4) are undercut to form the silicon island (4), as shown in the attached figure. Figure 2 As shown in [6].

[0028] Obviously, the above description is not a limitation of the present invention, and the present invention is not limited to the examples above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A technique for protecting convex corners during deep etching of silicon islands, characterized in that: Each silicon island (4) uses 4 wires <110> The convex corner protection pattern is formed by the fixed beams (5) at both ends of the crystal orientation and two cantilever beams (6); <110> One end of the crystal-oriented fixed beam (5) is fixed on the frame (8), and the other fixed end is connected to the free end of the cantilever beam (6); the fixed end of the cantilever beam (6) is connected to the silicon island (4), and its width is equal to the width of the silicon island (4).

2. The convex corner protection technology for deep-etched silicon islands according to claim 1, characterized in that: Anisotropic corrosive liquid first undercut <110> Crystalline end-supported beam (5); then unmasked etching. <110> Silicon wedges (9) are fixed below the cantilever beams (5) at both ends of the crystal orientation to obtain a flat corrosion surface. At the same time, the etchant begins to undercut the cantilever beams (6) from the free end. <110> When the silicon wedge (9) under the fixed beam (5) at both ends of the crystal orientation is completely corroded and a flat corrosion surface is formed, the cantilever beam (6) is undercut, leaving the silicon island (4) part uncut.

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