Design, processing and manufacturing method of novel silicon-based terahertz frequency selection surface

Abstract

The invention relates to a design, processing and manufacturing method of a novel silicon-based terahertz frequency selection surface, and belongs to the technical field of electromagnetic fields and microwaves. The specific processing and manufacturing steps are as follows: manufacturing a silicon wafer; manufacturing a base; manufacturing a pressing ring; manufacturing a gasket; the gasket, the silicon wafer and the pressing ring are installed on the base, and manufacturing of the silicon-based terahertz frequency selection surface is completed; the silicon wafer is formed by stacking an upper silicon-based bonding structure, a middle silicon-based bonding structure and a lower silicon-based bonding structure; the thicknesses of the layers are the same; wherein the upper surface and the lower surface of the silicon wafer are respectively etched with periodic array patterns and then are subjected to gold plating treatment; the gap between the vertical side wall of the base and the silicon wafer is adjusted through the gasket; a chamfer is arranged on the side wall of the inner ring of the pressing ring; a supporting rib plate is arranged on the side wall of the base; the structure has the advantages of being high in structural strength, compact, good in universality, high in installation precision and the like, and can resist mechanical conditions in the rocket launching stage while meeting the requirement for filtering electrical performance.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic field and microwave technology, and relates to a novel silicon-based terahertz frequency selective surface design, processing and manufacturing method. Background Technology

[0002] With the development of satellite meteorological observation technology, meteorological observation is moving towards full-band, all-weather, and global observation capabilities, covering microwave, visible light, multispectral, and hyperspectral spectrums. Within the entire Earth meteorological observation system, ice clouds in the upper troposphere are one of the most important and difficult-to-determine meteorological elements, significantly impacting Earth's energy balance, climate change, and weather evolution. Traditional microwave and millimeter-wave remote sensing systems are ineffective at detecting ice clouds. Terahertz waves (100 GHz-10 THz), situated between microwave / millimeter-wave and infrared / visible light, have wavelengths closer to the size of the main particles in ice clouds. Therefore, terahertz detection technology is the best means of observing ice clouds. In the design of terahertz band detection instruments, it is often necessary to observe multiple channels and multiple frequency bands of spectral lines. To ensure a simple and compact instrument structure while considering the high frequency of the terahertz band, the mainstream international design method uses a frequency selectivity surface to control the transmission and reflection of electromagnetic waves in different frequency bands, thereby achieving filtering of different terahertz bands.

[0003] A frequency selective surface is a plane with a one-dimensional or two-dimensional periodic array structure, through which different electromagnetic waves exhibit different frequency responses after filtering. Currently, research on the design, fabrication, and preparation of frequency selective surfaces in the terahertz band above 400 GHz is almost nonexistent in China. Summary of the Invention

[0004] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a new design, processing and manufacturing method for silicon-based terahertz frequency selective surfaces. This method has the advantages of high structural strength, compactness, good versatility and high installation accuracy. It meets the requirements of filter electrical performance and can withstand the mechanical conditions during rocket launch.

[0005] The solution of the present invention is:

[0006] A novel method for designing, fabricating, and manufacturing a silicon-based terahertz frequency selective surface includes:

[0007] Making silicon wafers;

[0008] Make a base;

[0009] Make the pressure ring;

[0010] Make gaskets;

[0011] The gasket, silicon wafer, and pressure ring are installed on the base to complete the fabrication of the silicon-based terahertz frequency selective surface.

[0012] In the above-mentioned novel silicon-based terahertz frequency selective surface design and manufacturing method, the silicon wafer is made of three layers of silicon-based bonding structure stacked together; each layer has the same thickness; wherein, the upper and lower surfaces of the silicon wafer are respectively etched with periodic array patterns and then gold-plated; the silicon wafer has a circular plate structure; two lugs are symmetrically arranged on the outer side of the silicon wafer; a positioning pin hole is arranged in the center of the lug; the positioning pin hole is arranged at a fixed angle with the periodic array pattern.

[0013] In the above-mentioned novel silicon-based terahertz frequency selective surface design and manufacturing method, the periodic array pattern is a C-shaped slot cell; the etching positions of the periodic array pattern on the upper and lower surfaces of the silicon wafer correspond one-to-one.

[0014] In the above-mentioned novel silicon-based terahertz frequency selective surface design and manufacturing method, periodic array patterns are etched on the upper and lower surfaces of a silicon wafer using a laser etching method.

[0015] In the above-mentioned novel silicon-based terahertz frequency selective surface design and manufacturing method, the diameter of the silicon wafer is 4 inches; the silicon wafer is a passive spatial filter material with a filtering frequency of 448GHz-664GHz.

[0016] In the above-mentioned design, processing and manufacturing method of a novel silicon-based terahertz frequency selective surface, the base is a vertically placed L-shaped structure; the base is made of aluminum metal material; screw holes are provided on the vertical side wall of the base to achieve docking between the back of the base and the external compartment plate; through holes are provided on the vertical side wall of the base to correspond to the positions of the two lugs of the silicon wafer, and alignment is achieved by a pin.

[0017] In the above-mentioned design, processing and manufacturing method of a novel silicon-based terahertz frequency selective surface, the pressure ring is made of aluminum metal material; the pressure ring has a ring structure.

[0018] In the above-mentioned design, processing and manufacturing method of a novel silicon-based terahertz frequency selective surface, the gasket has a ring structure.

[0019] In the above-mentioned design, processing and manufacturing method of a novel silicon-based terahertz frequency selective surface, the gasket is coaxially mounted on the front of the vertical side wall of the base; the silicon wafer is coaxially placed on the gasket; the pressure ring is coaxially placed on the silicon wafer; and it is fastened through the screw hole.

[0020] In the above-mentioned design, processing and manufacturing method of a novel silicon-based terahertz frequency selective surface, the gap between the vertical side wall of the base and the silicon wafer is adjusted by using a shim; a chamfer is provided on the inner side wall of the pressure ring; and a support rib is provided on the side wall of the base.

[0021] The advantages of this invention compared to the prior art are:

[0022] (1) This invention can effectively separate and filter key spectral lines of ice water and ice particles in the 448GHz-664GHz range, and has made breakthroughs in key technologies such as the preparation technology of silicon-based frequency selectivity surface in the terahertz band, lightweight modular design technology, and installation and calibration.

[0023] (2) This invention has the advantages of high structural strength, compactness, good versatility and high installation accuracy. While meeting the requirements of filter electrical performance, it can resist the mechanical conditions during the rocket launch stage and has excellent spaceborne performance and broad application prospects.

[0024] (3) The present invention can meet the filtering requirements of the terahertz band with frequencies above 448 GHz. Compared with conventional frequency duplexers, the present invention has the advantages of light weight, compact structure and high degree of integration. It is easy to achieve modularization and can achieve high-precision assembly. It is particularly suitable for the preparation of filter devices for large-scale terahertz ice cloud meteorological detection. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the silicon wafer of the present invention;

[0026] Figure 2 This is a schematic diagram of the silicon wafer etching periodic array pattern of the present invention;

[0027] Figure 3 This is a schematic diagram of the silicon-based terahertz frequency selectivity surface of the present invention;

[0028] Figure 4 This is a side sectional view of the silicon-based terahertz frequency selection surface of the present invention;

[0029] Figure 5 This is an enlarged view of the silicon-based terahertz frequency selectivity surface of the present invention;

[0030] Figure 6 This is a process flow diagram for manufacturing silicon wafers according to the present invention. Detailed Implementation

[0031] The present invention will be further described below with reference to the embodiments.

[0032] This invention provides a novel design, fabrication, and manufacturing method for silicon-based terahertz frequency selective surfaces, capable of effectively separating and filtering key spectral lines of water ice and ice particles at 448 GHz and 664 GHz. It overcomes key technical challenges in the fabrication, lightweight modular design, and installation calibration of silicon-based frequency selective surfaces in the terahertz band. This invention boasts advantages such as high structural strength, compactness, good versatility, and high installation accuracy. While meeting the electrical performance requirements for filtering, it can withstand the mechanical conditions of rocket launch, exhibiting excellent spaceborne performance and broad application prospects.

[0033] The design, fabrication, and manufacturing method of a silicon-based terahertz frequency selective surface specifically includes the following steps:

[0034] Fabricating silicon wafer 1, such as Figure 1 As shown.

[0035] Silicon wafer 1 is fabricated using a stacked three-layer silicon-based bonding structure (top, middle, and bottom); each layer has the same thickness. The top and bottom surfaces of silicon wafer 1 are etched with periodic array patterns and then gold-plated. Silicon wafer 1 has a circular plate-like structure. Two lugs are symmetrically arranged on the outer side of silicon wafer 1. A positioning pin hole is located at the center of each lug. The positioning pin holes are arranged at a fixed angle to the periodic array pattern. The periodic array pattern is a C-shaped slot cell, such as... Figure 2 As shown, the etching positions of the periodic array patterns on the upper and lower surfaces of silicon wafer 1 correspond one-to-one.

[0036] Silicon wafer 1 is fabricated using a stacked three-layer silicon-based bonding structure (top, middle, and bottom); each layer has the same thickness. The top and bottom surfaces of silicon wafer 1 are etched with periodic array patterns and then gold-plated. Silicon wafer 1 has a circular plate-like structure. Two lugs are symmetrically arranged on the outer side of silicon wafer 1. A positioning pin hole is located at the center of each lug. The positioning pin holes are arranged at a fixed angle to the periodic array pattern. The periodic array pattern is a C-shaped slot cell; the etching positions of the periodic array patterns on the top and bottom surfaces of silicon wafer 1 correspond one-to-one.

[0037] Periodic array patterns were etched on the upper and lower surfaces of silicon wafer 1 using a laser etching method. Silicon wafer 1 has a diameter of 4 inches and is a passive spatial filter material with a filtering frequency of 448 GHz to 664 GHz.

[0038] Make the base 2.

[0039] The base 2 is a vertically placed L-shaped structure; the base 2 is made of aluminum metal; the vertical side wall of the base 2 is provided with screw holes, through which the back of the base 2 is connected to the external compartment plate; the vertical side wall of the base 2 is provided with through hole structures corresponding to the two lug positions of the silicon wafer 1, and alignment is achieved by a pin.

[0040] Make the pressure ring 3.

[0041] The pressure ring 3 is made of aluminum metal; the pressure ring 3 has a ring structure.

[0042] Make gasket 4.

[0043] Gasket 4 has a ring-shaped structure.

[0044] Install the gasket 4, silicon wafer 1, and pressure ring 3 onto the base 2 to complete the fabrication of the silicon-based terahertz frequency selective surface.

[0045] Install the gasket 4 coaxially on the front of the vertical side wall of the base 2; place the silicon wafer 1 coaxially on the gasket 4; place the pressure ring 3 coaxially on the silicon wafer 1; and tighten it through the screw holes. Figures 3-5 As shown.

[0046] The gap between the vertical sidewall of the base 2 and the silicon wafer 1 is adjusted by the shim 4; the inner sidewall of the pressure ring 3 is chamfered; and the sidewall of the base 2 is provided with support ribs.

[0047] In this invention, the central axis of the groove of the silicon wafer 1 coincides with that of the base 2, and the central axis is 30mm away from the outer mounting surface of the base 2.

[0048] like Figure 6 As shown, the process flow for fabricating silicon wafer 1 is as follows:

[0049] First, the silicon wafers are bonded together. Then, the C-shaped mesh structure is transferred onto the silicon wafer using photolithography. ICP etching is performed using photoresist as a mask. Then, the photoresist is removed, the adhesive is removed, and after cleaning, metallization is performed. Finally, the three-layer silicon wafer bonding is completed.

[0050] (1) Silicon wafer bonding

[0051] In this project, the frequency selection plane is fabricated by directly bonding an ultrathin silicon wafer to a sacrificial silicon wafer and etching it in one step. During the etching process, the sacrificial wafer serves to transfer heat and prevent damage to the device base after the via etching is completed. The bonding operation should be performed as follows: Place the sacrificial wafer on the hot stage. Once the hot stage reaches the set temperature of 140°C, evenly apply adhesive to the surface of the sacrificial wafer; wait 5 minutes to allow the adhesive to fully melt and, driven by its own fluidity, thoroughly wet the surface of the sacrificial wafer, ensuring a uniform thickness of adhesive throughout; apply adhesive to one side of the ultrathin silicon wafer using the same method; slowly push the ultrathin silicon wafer, adhesive side down, from one side of the sacrificial wafer to the other until its shape completely overlaps with the sacrificial wafer's shape; gently press and rotate the ultrathin silicon wafer slightly to expel any residual air from the bonding interface; wait approximately 1 minute, then remove the bonded silicon wafer from the hot stage to cool. In a bright environment, rotate the "bonded" ultrathin silicon wafer slightly left and right, facing upwards. The image of the object projected onto the silicon wafer should not be distorted or magnified. Any form of image distortion indicates the presence of impurities, bubbles, or uneven adhesive at the bonding interface, and the bonding process should be repeated. Then, place it in the pre-vacuum chamber of the ICP equipment. If there is no obvious unevenness, bubbling, or cracking, it can be assumed that it will remain intact even in a high-vacuum chamber.

[0052] (2) Photolithography

[0053] The pattern on the photomask (a C-shaped pattern in this example) is transferred to the wafer surface using photoresist. The permissible error for the pattern on the frequency selective plane is ±4μm. Simultaneously, the photoresist must not react significantly with the etching gas during ICP etching. AZ series positive photoresist is preferred for fabricating the frequency selective surface. Recommended process parameters are: spray speed 1.5L / min, 4 spray passes, photoresist layer thickness 4–5μm, pre-baking at 80℃ for 70min, and hardening at 90℃ for 60–70min.

[0054] (3) ICP etching

[0055] Using the BOSCH process principle, the seam etching is completed using a combination of C4F8 and SF6 gases. To increase etching uniformity and reduce the impact of temperature fluctuations, the silicon wafer temperature is set to 5°C. Simultaneously, to increase plasma energy, the top cover temperature is set to 45°C. After continuous optimization of gas flow rate and plasma power, a total duration of 24 minutes is considered optimal.

[0056] (4) Silicon wafer debonding

[0057] First, the photoresist film on the surface of the ultrathin silicon wafer is removed by wiping or soaking with an organic solvent. Then, the entire bonding sheet is immersed in deionized water and boiled, followed by ultrasonic treatment in a 70°C water bath. When removing the photoresist film, the contact time between the organic solvent and the "bond" between the ultrathin silicon wafer and the sacrificial wafer should be minimized, which is approximately 30 seconds in this case.

[0058] (5) Metallization

[0059] The deposition of metal films is achieved by DC magnetron sputtering. The key to DC magnetron sputtering is to achieve the required adhesion between the metal layer and the silicon wafer. Measures to improve adhesion include improving the pre-sputtering cleaning method to obtain an active interface, and selecting sputtering metal materials and controlling process parameters to improve the bonding force between the film and the silicon wafer.

[0060] The cleaning process was selected to follow the standard silicon wafer cleaning steps SC1 and SC2: ultrasonic cleaning at 75°C in a mixed solution of NH3OH, H2O2, and H2O; followed by ultrasonic cleaning at 75°C in a mixed solution of HCl, H2O2, and H2O; and finally, dehydration and drying to complete the entire cleaning process. The sputtered film structure was set as NiCr-Au, with the NiCr layer thickness approximately... The Au layer thickness is approximately The sputtering parameters are as follows: background vacuum level better than 1×10-6 mbar; plasma cleaning process pressure of 5×10-2 mbar, argon flow rate of 100 sccm, RF power of 400 W, cleaning time of 180 s; sputtering temperature of 200℃±5℃; baking time of 15 min-25 min; stage movement speed of 770~790 mm / min when sputtering NiCr layer; stage movement speed of 490~510 mm / min when sputtering Au layer; sputtering power of 1000 W.

[0061] (6) Bonding

[0062] Bonding is a crucial process for stacking three discrete silicon wafers into a single frequency-selective surface. At an operating frequency of 664 GHz, sputtered gold layers can meet the adhesion depth requirements. Sputtered gold layers can maximize the preservation of the original silicon wafer roughness, and excellent bonding can be achieved after cleaning. Before bonding, the three silicon wafers to be bonded have already been cut in the ICP stage. This allows for the assurance of dimensional accuracy of the product through photolithography, but the drawback is that standard-sized bonding equipment cannot be used. Since the basic principle of bonding is temperature, pressure, time, and alignment, special tooling was used in this project to align and fix the three non-standard-sized silicon wafers and complete the bonding of the three silicon wafers under high pressure of 200 MPa and low temperature of 85°C.

[0063] This invention can effectively separate and filter key spectral lines of ice water and ice particles in the 448GHz-664GHz range, and has made breakthroughs in key technologies such as the preparation technology of silicon-based frequency selectivity surfaces in the terahertz band, lightweight modular design technology, and installation and calibration.

[0064] This invention has the advantages of high structural strength, compactness, good versatility, and high installation accuracy. While meeting the requirements of filtering electrical performance, it can resist the mechanical conditions during rocket launch, and has excellent spaceborne performance and broad application prospects.

[0065] This invention can meet the filtering requirements of the terahertz band above 448 GHz. Compared with conventional frequency duplexers, this invention has the advantages of light weight, compact structure, and high degree of integration. It is easy to modularize and can achieve high-precision assembly, making it particularly suitable for the preparation of filter devices for large-scale terahertz ice cloud meteorological detection.

[0066] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for designing, fabricating, and manufacturing a silicon-based terahertz frequency selective surface, characterized in that: include: Fabrication of silicon wafers (1); Make the base (2); Make the pressure ring (3); Make gaskets (4); Install the gasket (4), silicon wafer (1), and pressure ring (3) on the base (2) to complete the fabrication of the silicon-based terahertz frequency selective surface.

2. The method for designing, fabricating, and manufacturing a silicon-based terahertz frequency selective surface according to claim 1, characterized in that: The silicon wafer (1) is made of three layers of silicon-based bonding structure stacked together: upper, middle and lower layers; each layer has the same thickness; the upper and lower surfaces of the silicon wafer (1) are respectively etched with periodic array patterns and then plated with gold; the silicon wafer (1) has a circular plate structure; two lugs are symmetrically arranged on the outer side of the silicon wafer (1); a positioning pin hole is provided in the center of the lug; the positioning pin hole is arranged at a fixed angle with the periodic array pattern.

3. The method for designing, fabricating, and manufacturing a silicon-based terahertz frequency selective surface according to claim 2, characterized in that: The periodic array pattern is a C-shaped slot cell; the etching positions of the periodic array pattern on the upper and lower surfaces of the silicon wafer (1) correspond one-to-one.

4. The method for designing, fabricating, and manufacturing a silicon-based terahertz frequency selective surface according to claim 1, characterized in that: Periodic array patterns were etched on the upper and lower surfaces of a silicon wafer (1) using a laser etching method.

5. The method for designing, fabricating, and manufacturing a silicon-based terahertz frequency selective surface according to claim 1, characterized in that: The diameter of the silicon wafer (1) is 4 inches; the silicon wafer (1) is a passive space filter material with a filtering frequency of 448GHz-664GHz.

6. The method for designing, fabricating, and manufacturing a silicon-based terahertz frequency selective surface according to claim 2, characterized in that: The base (2) is a vertically placed L-shaped structure; the base (2) is made of aluminum metal material; the vertical side wall of the base (2) is provided with screw holes, and the back of the base (2) is connected to the outer compartment plate through the screw holes; the vertical side wall of the base (2) is provided with through hole structures corresponding to the two lug positions of the silicon wafer (1), and alignment is achieved through pins.

7. The method for designing, fabricating, and manufacturing a silicon-based terahertz frequency selective surface according to claim 2, characterized in that: The pressure ring (3) is made of aluminum metal material; the pressure ring (3) has a ring structure.

8. The method for designing, fabricating, and manufacturing a silicon-based terahertz frequency selective surface according to claim 2, characterized in that: The gasket (4) has a ring structure.

9. The method for designing, fabricating, and manufacturing a silicon-based terahertz frequency selective surface according to claim 2, characterized in that: Install the gasket (4) coaxially on the front of the vertical side wall of the base (2); place the silicon wafer (1) coaxially on the gasket (4); place the pressure ring (3) coaxially on the silicon wafer (1); and tighten it through the screw hole.

10. The method for designing, fabricating, and manufacturing a silicon-based terahertz frequency selective surface according to claim 9, characterized in that: The gap between the vertical sidewall of the base (2) and the silicon wafer (1) is adjusted by using a shim (4); the inner sidewall of the pressure ring (3) is chamfered; and the sidewall of the base (2) is provided with a support rib.

Images