Focused ion beam suspended microstructure processing method, system thereof, and suspended microstructure

Abstract

The application provides a focused ion beam suspended microstructure processing method, a system thereof and a suspended microstructure, and comprises the following steps: step S1: a sacrificial layer is arranged on the surface of a substrate; a thin film material is deposited on the sacrificial layer; step S2: the substrate after the deposition of the thin film material is placed into a focused ion beam device chamber, the middle part of a designed pattern is selected, and the pattern structure on the surface of the thin film material is processed by using a focused ion beam, and the etching depth is not less than the thickness of the thin film; step S3: a preset gas is introduced into the focused ion beam device chamber through a gas system, the surface of the pattern structure is etched, the etching time is controlled, and the suspended structure is obtained in combination with ion beam etching; and step S4: the remaining pattern on the surface of the suspended structure is processed to a required position, and a suspended edge structure and a suspended microstructure are obtained. The focused ion beam twice etching method is used for suspended microstructure processing, and the technical problems that the suspended edge is difficult to control and the edge structure is not easy to process in the prior art are solved.

Description

Technical Field

[0001] This invention relates to the technical field of semiconductor processing, and more specifically, to a focused ion beam suspension microstructure processing method, system, and suspension microstructure. Background Technology

[0002] Semiconductor fabrication technology is the cornerstone of integrated circuit development. Suspended microstructures fabricated using various processes are primarily used in microsensors, microactuators, micromechanics, and vacuum microelectronics, with broad application prospects in consumer electronics, aerospace, information technology, biomedicine, environmental monitoring, and military fields. With the advancement of semiconductor fabrication technology, the fabrication of suspended structures, such as photonic crystal structures, air bridges, and cantilever beams, has attracted increasing attention and is gradually becoming one of the key structures in micro-electro-mechanical system (MEMS) sensors.

[0003] Chinese invention patent document CN114488698A discloses a method for fine fabrication of suspended microstructures of epoxy-based photoresist manufactured by ultraviolet lithography. The method includes the following steps: S1, distributing SU-8 photoresist onto a Si / SiO2 substrate and coating it on a spin coater; S2, removing edge beads by distributing propylene glycol methyl ether acetate at the edge of a rotating wafer; S3, placing the wafer on a programmable heating plate at room temperature for low-temperature baking; S4, first ultraviolet exposure; S5, spin-coating mr-DWL 40 photoresist onto SU-8, followed by soft baking; S6, second ultraviolet exposure, followed by baking, development, rinsing, and drying.

[0004] Suspended microstructures are typically realized using semiconductor processes. Patterning is performed through photolithography and etching, and the suspension structure is released through wet or dry etching.

[0005] Regarding the aforementioned technologies, the inventors believe that the entire process of suspending microstructures is complex, and the yield is often limited by the process. In particular, the position of the pattern on the edge of the suspended structure is difficult to control, and the processing of patterns that span both suspended and non-suspended parts is even more difficult to achieve. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a focused ion beam suspension microstructure fabrication method, system, and suspension microstructure.

[0007] A method for fabricating microstructures by focusing ion beam suspension according to the present invention includes the following steps:

[0008] Step S1: A sacrificial layer is formed on the surface of the substrate; a thin film material is deposited on the sacrificial layer;

[0009] Step S2: Place the substrate after depositing the thin film material into the chamber of the focused ion beam equipment, select the middle part of the designed pattern, and use the focused ion beam to process the pattern structure on the surface of the thin film material, and the etching depth is not less than the film thickness.

[0010] Step S3: In the chamber of the focused ion beam equipment, a preset gas is introduced through the gas system to perform sacrificial layer etching on the surface of the patterned structure. The gas introduction time is controlled in combination with ion beam etching to obtain a suspended structure.

[0011] Step S4: Process the remaining pattern on the surface of the suspended structure to the desired position to obtain the suspended edge structure and suspended microstructure.

[0012] Preferably, in step S1, the sacrificial layer comprises monocrystalline silicon, polycrystalline silicon, amorphous silicon, or tungsten material.

[0013] Preferably, in step S2, the patterned structure is a patterned structure of not less than 10 nanometers.

[0014] Preferably, in step S3, the preset gas is xenon fluoride gas, and the gas transmission time is not less than 0.5 minutes.

[0015] Preferably, in step S4, the suspended microstructure is a suspended structure or a cap-shaped structure.

[0016] A focused ion beam suspension microstructure fabrication system according to the present invention includes the following modules:

[0017] Module M1: A sacrificial layer is disposed on the surface of the substrate; a thin film material is deposited on the sacrificial layer;

[0018] Module M2: Place the substrate after the thin film material is deposited into the chamber of the focused ion beam equipment, select the middle part of the designed pattern, and use a focused ion beam to process the pattern structure on the surface of the thin film material, and the etching depth is not less than the film thickness.

[0019] Module M3: A preset gas is introduced into the chamber of the focused ion beam equipment through a gas system to perform sacrificial layer etching on the surface of the patterned structure. By controlling the gas transmission time in combination with ion beam etching, a suspended structure is obtained.

[0020] Module M4: Processes the remaining pattern on the surface of the suspended structure to the desired position to obtain the suspended edge structure and suspended microstructure.

[0021] Preferably, in the module M1, the sacrificial layer comprises monocrystalline silicon, polycrystalline silicon, amorphous silicon, or tungsten material.

[0022] Preferably, in module M2, the graphic structure is a structure pattern of not less than 10 nanometers.

[0023] Preferably, in module M3, the preset gas is xenon fluoride gas, and the gas supply time is not less than 0.5 minutes.

[0024] According to the present invention, a suspended microstructure is obtained by processing using a focused ion beam suspended microstructure processing method.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. This invention uses a focused ion beam two-stage etching method to process suspended microstructures, which solves the technical problems of difficult control of suspended edges and difficulty in processing edge structures in the prior art;

[0027] 2. Compared with traditional methods, this invention is applicable to the preparation of suspended microstructures of various materials, and is particularly suitable for the processing of micro-sized suspended microstructures;

[0028] 3. Compared with traditional methods, this invention has a simple process and does not require photolithography and wet etching, thus solving the problems of complex processes and low yield in existing processes. Attached Figure Description

[0029] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0030] Figure 1 To design a schematic diagram of the graphic processing area;

[0031] Figure 2 This is a flowchart of the suspension membrane preparation process. Detailed Implementation

[0032] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0033] Embodiment 1 of this invention discloses a method for fabricating microstructures suspended by a focused ion beam, such as... Figure 1 and Figure 2 As shown, it includes the following steps:

[0034] Step S1: Deposit thin film materials of varying thicknesses on a substrate with a sacrificial layer on its surface. The thin film material is a material that does not react with xenon fluoride. The sacrificial layer can be monocrystalline silicon, polycrystalline silicon, amorphous silicon, or tungsten.

[0035] Step S2: Place the substrate obtained in Step S1 into the chamber of the focused ion beam (FIB) equipment. Select the middle portion of the designed pattern and use a FIB to process the surface pattern structure of the middle portion on the thin film surface according to the design. The etching depth is not less than the film thickness. The pattern structure is a structure pattern of not less than 10 nanometers. The middle portion of the designed pattern refers to the pattern portion within 10 nm of the edge of the designed pattern. The outermost edge of the middle portion pattern structure is not less than 0.1 micrometers from the edge of the designed suspended structure.

[0036] Step S3: Xenon fluoride gas (xenon difluoride, xenon tetrafluoride, or xenon hexafluoride) is introduced into the focused ion beam cavity through a gas system to perform sacrificial layer etching on the surface of the patterned structure obtained in step S2. The gas introduction time is controlled in conjunction with ion beam etching to obtain a suspended structure (suspended microstructure). The gas introduction time is not less than 0.5 minutes.

[0037] Step S4: Process the remaining pattern on the surface of the suspended structure obtained in step S3 to the desired position to obtain a suspended edge structure and a position-controllable suspended microstructure. The suspended microstructure is a suspended structure or a cap-shaped structure.

[0038] The present invention also provides a focused ion beam suspended microstructure processing system, which can be implemented by executing the process steps of the focused ion beam suspended microstructure processing method. That is, those skilled in the art can understand the focused ion beam suspended microstructure processing method as a preferred embodiment of the focused ion beam suspended microstructure processing system.

[0039] The system includes the following modules:

[0040] Module M1: A sacrificial layer is disposed on the surface of the substrate; a thin film material is deposited on the sacrificial layer. The sacrificial layer may be monocrystalline silicon, polycrystalline silicon, amorphous silicon, or tungsten material.

[0041] Module M2: The substrate after the thin film material is deposited is placed in the chamber of the focused ion beam equipment. The middle part of the designed pattern is selected, and the pattern structure is processed on the surface of the thin film material using a focused ion beam, with an etching depth not less than the film thickness. The pattern structure is a structure with a minimum thickness of 10 nanometers.

[0042] Module M3: A preset gas is introduced into the chamber of the focused ion beam equipment via a gas system to etch a sacrificial layer on the surface of the patterned structure. By controlling the gas introduction time in conjunction with ion beam etching, a suspended structure is obtained. The preset gas is xenon fluoride gas, and the gas introduction time is not less than 0.5 minutes.

[0043] Module M4: Processes the remaining pattern on the surface of the suspended structure to the desired position, obtaining the suspended edge structure and suspended microstructure. The suspended microstructure can be a suspended structure or a cap-shaped structure.

[0044] Embodiment 1 of the present invention also discloses a suspended microstructure, which is obtained by processing using a focused ion beam suspended microstructure processing method.

[0045] Embodiment 2 of the present invention discloses a method for fabricating microstructures suspended by focused ion beam, such as... Figure 1 and Figure 2 As shown, it includes the following steps:

[0046] Step S1: Using silicon as a sacrificial layer on a silicon substrate, a 2-micron silicon nitride thin film is grown using a low-pressure chemical vapor deposition process.

[0047] Step S2: Place the substrate obtained in step S1 into the chamber of the focused ion beam equipment and design and fabricate a cantilever beam structure with a width of 10 μm, a length of not less than 50 μm, and a distance of 2 μm from the edge of the suspended structure.

[0048] Step S3: Use a gallium ion beam to process the surface pattern structure of the middle part, with a voltage of 30KV and a beam current of 4nA, to etch a 10μm*49μm rectangular frame with one end open, and an etching depth of 2μm.

[0049] Step S4: Xenon fluoride gas is introduced into the focused ion beam cavity through the gas system to perform sacrificial layer etching on the surface of the patterned structure obtained in step S3. The voltage is 15KV, the beam current is 1pA, the sacrificial layer is etched, the gas transmission time is controlled at 30 minutes, and the etching is then completed.

[0050] Step S5: Extend the etching at the 49μm long side opening end to 2μm from the edge of the suspended structure, with a voltage of 30KV and a beam current of 1nA, to obtain a suspended microstructure with a width of 10μm, a length of not less than 50μm, and a distance of 2μm from the suspended edge.

[0051] Embodiment 3 of the present invention also discloses a method for fabricating microstructures suspended by focused ion beam, comprising the following steps:

[0052] Step S1: Deposit 200 nm polycrystalline silicon as a sacrificial layer on a glass substrate using chemical vapor deposition, and deposit a 200 nm gold thin film using electron beam evaporation.

[0053] Step S2: Place the substrate obtained in step S1 into the chamber of the focused ion beam equipment, design and process a 10*10 unit suspended cap array with no gold film suspended on the outer frame, the diameter of the circular structure at the top of the cap is 500nm, the spacing is 200nm, and the distance between the array and the outer frame is 500nm.

[0054] Step S3: Use gallium ion beam to process the surface pattern structure of the middle part, with a voltage of 30KV, a beam current of 240pA, and etch 10*10 circular structural units. The distance between the array edge circle and the outer frame is 150nm, and the etching depth is 220nm.

[0055] Step S4: Xenon fluoride gas is introduced into the focused ion beam cavity through the gas system to perform sacrificial layer etching on the surface of the patterned structure obtained in step S3. The voltage is 30KV, the beam current is 10pA, the sacrificial layer is etched, the gas transmission time is controlled at 3 minutes, and the etching is completed.

[0056] Step S5: Extend the etching along the edge of the patterned structure to 500nm from the edge of the array circle, with a voltage of 30KV and a beam current of 240pA, to obtain a cap-shaped suspension structure that meets the design requirements.

[0057] Embodiment 4 of the present invention also discloses a method for fabricating microstructures suspended by focused ion beam, comprising the following steps:

[0058] Step S1: A 50 nm tungsten film is grown on a quartz substrate using atomic layer deposition as a sacrificial layer, and a 100 nm ITO film is deposited using magnetron sputtering.

[0059] Step S2: Place the substrate obtained in step S1 into the chamber of the focused ion beam equipment, and design and process a 30*30 unit circular hole suspended array with a hole diameter of 150nm and a spacing of 100nm. Half of the outermost circular hole is suspended, and the other half is not suspended.

[0060] Step S3: Use gallium ion beam to process the surface pattern structure of the middle part, with a voltage of 30KV, a beam current of 120pA, and etch 29*29 circular structural units to a depth of 100 nanometers.

[0061] Step S4: Xenon fluoride gas is introduced into the focused ion beam cavity through the gas system to perform sacrificial layer etching on the surface of the patterned structure obtained in step S3. The voltage is 30KV, the beam current is 5pA, the sacrificial layer is etched, the gas transmission time is controlled to 1 minute, and the etching is completed to form a suspended structure in the middle. The outermost edge of the circular structure is suspended by about 150nm.

[0062] Step S5: Etch the remaining outermost circular holes at the edge of the patterned structure. The voltage is 30KV, the beam current is 120pA, and the etching depth is 100 nanometers to obtain a suspended structure with semi-suspended edge holes that meets the design requirements.

[0063] Embodiment 5 of the present invention discloses a method for fabricating microstructures suspended by focused ion beam, comprising the following steps:

[0064] Step S1: Deposit 20 nm amorphous silicon as a sacrificial layer on a lithium niobate substrate using plasma-enhanced chemical vapor deposition, and grow 2 nm silicon oxide and 3 nm titanium nitride using atomic layer deposition.

[0065] Step S2: Place the substrate obtained in step S1 into the chamber of the focused ion beam equipment, and design and process a 5*5 unit square hole suspended array with a hole diameter of 10nm, a spacing of 30nm, and the distance between the outermost hole edge and the suspended edge is no more than 10nm.

[0066] Step S3: Use a helium ion beam to process the surface pattern structure of the middle part, with a voltage of 30KV, a beam current of 1pA, and etch 4*4 circular structural units to a depth of 5 nanometers.

[0067] Step S4: Xenon fluoride gas is introduced into the focused ion beam cavity through the gas system to perform sacrificial layer etching on the surface of the patterned structure obtained in step S3. The voltage is 30KV, the beam current is 0.1pA, the sacrificial layer is etched, the gas introduction time is controlled at 0.5 minutes, and the etching is completed to form a suspended structure in the middle. The outermost edge of the square structure is suspended by about 45nm.

[0068] Step S5: Etch the remaining outermost square holes at the edge of the patterned structure. The voltage is 30KV, the beam current is 1pA, and the etching depth is 5 nanometers to obtain a suspended structure with square holes that meet the design requirements.

[0069] This invention presents a simple focused ion beam (FIB) method for fabricating suspended microstructures, addressing the problems of complex processes, difficulty in controlling the position of suspended structure edges, and challenges in fabricating structures across suspended edges in existing methods. This method yields suspended microstructures with controllable suspended edges and structure positions. Focused ion beam (FIB) technology accelerates and focuses an ion beam generated by an ion source onto a sample surface, generating secondary electron signal images. It can also be used for micro / nano fabrication or combined with other reactions for deposition. Since its inception, FIB technology has attracted widespread attention and has been widely applied in areas such as chip circuit modification, cross-sectional analysis, transmission electron microscopy sample preparation, and materials analysis. In recent years, the application of FIB in micro / nano fabrication has also gradually developed. It eliminates the need for pattern processing, coating, and development steps, offering advantages in simple processes and ease of fabrication, particularly in small-area micro / nano structure fabrication. This invention overcomes the difficulty in controlling the edges of suspended structures in existing technologies by etching the pattern in two separate parts.

[0070] Those skilled in the art will understand that, besides implementing the system and its various devices, modules, and units provided by this invention in the form of purely computer-readable program code, the same functions can be achieved entirely through logical programming of the method steps, making the system and its various devices, modules, and units of this invention function in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, the system and its various devices, modules, and units provided by this invention can be considered as a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; alternatively, the devices, modules, and units for implementing various functions can be considered as both software modules implementing the method and structures within the hardware component.

[0071] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for fabricating microstructures suspended by a focused ion beam, characterized in that, Includes the following steps: Step S1: A sacrificial layer is formed on the surface of the substrate; a thin film material is deposited on the sacrificial layer; Step S2: Place the substrate after depositing the thin film material into the chamber of the focused ion beam equipment, select the middle part of the designed pattern, and use the focused ion beam to process the pattern structure on the surface of the thin film material, and the etching depth is not less than the film thickness. Step S3: In the chamber of the focused ion beam equipment, a preset gas is introduced through the gas system to perform sacrificial layer etching on the surface of the patterned structure. The gas introduction time is controlled in combination with ion beam etching to obtain a suspended structure. Step S4: Process the remaining pattern on the surface of the suspended structure to the desired position to obtain the suspended edge structure and suspended microstructure; The middle part of the design graphic refers to the fact that the distance between the outermost edge of the middle part graphic structure and the edge of the designed suspended structure is not less than 0.1 micrometers.

2. The focused ion beam suspension microstructure fabrication method according to claim 1, characterized in that, In step S1, the sacrificial layer includes monocrystalline silicon, polycrystalline silicon, amorphous silicon, or tungsten material.

3. The focused ion beam suspension microstructure fabrication method according to claim 1, characterized in that, In step S2, the patterned structure is a patterned structure of not less than 10 nanometers.

4. The focused ion beam suspension microstructure fabrication method according to claim 1, characterized in that, In step S3, the preset gas includes xenon fluoride gas; the ventilation time is not less than 0.5 minutes.

5. The focused ion beam suspension microstructure fabrication method according to claim 1, characterized in that, In step S4, the suspended microstructure is a suspended structure or a cap-shaped structure.

6. A focused ion beam suspension microstructure fabrication system, characterized in that, Includes the following modules: Module M1: A sacrificial layer is disposed on the surface of the substrate; a thin film material is deposited on the sacrificial layer; Module M2: Place the substrate after the thin film material is deposited into the chamber of the focused ion beam equipment, select the middle part of the designed pattern, and use a focused ion beam to process the pattern structure on the surface of the thin film material, and the etching depth is not less than the film thickness. Module M3: A preset gas is introduced into the chamber of the focused ion beam equipment through a gas system to perform sacrificial layer etching on the surface of the patterned structure. By controlling the gas transmission time in combination with ion beam etching, a suspended structure is obtained. Module M4: Processes the remaining pattern on the surface of the suspended structure to the desired position to obtain the suspended edge structure and suspended microstructure; The middle part of the design graphic refers to the fact that the distance between the outermost edge of the middle part graphic structure and the edge of the designed suspended structure is not less than 0.1 micrometers.

7. The focused ion beam suspension microstructure fabrication system according to claim 6, characterized in that, In module M1, the sacrificial layer includes monocrystalline silicon, polycrystalline silicon, amorphous silicon, or tungsten material.

8. The focused ion beam suspension microstructure fabrication system according to claim 6, characterized in that, In module M2, the patterned structure is a patterned structure of not less than 10 nanometers.

9. The focused ion beam suspension microstructure fabrication system according to claim 6, characterized in that, In module M3, the preset gas includes xenon fluoride gas; the ventilation time is not less than 0.5 minutes.

10. A suspended microstructure, characterized in that, The microstructure was fabricated using the focused ion beam suspension microstructure fabrication method described in any one of claims 1-5.

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