CN115241648B - Suspension structure cavity patch antenna based on MEMS (micro-electromechanical systems) technology - Google Patents

Abstract

The present invention relates to the technical field of patch antennas, and in particular to a suspended structure cavity patch antenna based on a MEMS process, comprising a metal radiating element and a microstrip feeder, a suspended structure cavity type quartz glass layer, a suspended structure cavity, a metal grounding layer and a quartz glass layer, wherein the metal radiating element and the microstrip feeder are located on the top of the quartz glass layer. The present invention manufactures the suspended structure cavity by means of a standard MEMS process, and the formed cavity and the double dielectric layer of quartz glass can effectively reduce the dielectric constant of the dielectric layer of the microstrip patch antenna, thereby reducing the loss of the dielectric layer of the antenna, thereby significantly increasing the bandwidth of the microstrip patch antenna and significantly improving the gain of the microstrip patch antenna. Selecting a quartz glass material with a low dielectric constant commonly used in the MEMS process as the antenna dielectric layer material can improve the antenna bandwidth, gain and other performances.

Description

A suspended structure cavity patch antenna based on MEMS technology

Technical Field

The present invention relates to the technical field of patch antennas, and in particular to a suspended structure cavity patch antenna based on MEMS technology.

Background technique

The equipment of traditional PCB printed circuit process is simple, easy to operate, and can be mass-produced. However, the size error of the antenna manufactured by it is large, which will cause the center resonant frequency of the antenna to shift. This type of process cannot manufacture a cavity structure on the antenna dielectric layer.

Semiconductor processes are suitable for mass production and high precision. Integrated circuits are usually made on high dielectric constant substrate materials, while antennas should be made on low dielectric constant substrates. The silicon substrate material used in typical semiconductor processes has low resistance and high dielectric constant. These characteristics will cause the RF signal from the RF circuit to be transmitted to the antenna through the low resistance path of the substrate substrate and converted into electromagnetic radiation, and most of the electromagnetic radiation is confined in the substrate substrate instead of radiating into free space, resulting in narrowed bandwidth and reduced gain, further reducing radiation efficiency; electromagnetic waves will significantly stimulate the generation of surface waves when passing through high dielectric constant substrate materials, which will significantly reduce the performance of microstrip antennas, such as lower efficiency, narrower bandwidth, deterioration of radiation pattern, and unnecessary coupling between radiating units in the array structure.

Although the target structure can be formed by using a sacrificial layer process when manufacturing the suspended structure cavity, this process increases the complexity of the antenna manufacturing process steps and the cost.

It can be seen that among the currently available microstrip patch antennas, there is no microstrip patch antenna that takes into account low cost, simple manufacturing process flow, and increased gain and widened bandwidth by loading a suspended structure cavity.

Summary of the invention

The purpose of the present invention is to solve the shortcomings of the prior art.

In order to achieve the above-mentioned object, the present invention adopts the following technical scheme: a suspended structure cavity patch antenna based on MEMS technology, comprising a metal radiating element and a microstrip feed line, a suspended structure cavity quartz glass layer, a suspended structure cavity, a metal grounding layer and a quartz glass layer, wherein the metal radiating element and the microstrip feed line are located on the top of the quartz glass layer, the suspended structure cavity quartz glass layer and the metal grounding layer are sequentially arranged between the metal radiating element, the microstrip feed line and the quartz glass layer from top to bottom, and the suspended structure cavity is opened through the suspended structure cavity quartz glass layer;

The method for manufacturing the suspended structure cavity microstrip patch antenna based on MEMS technology comprises the following steps:

S1: Prepare substrate for processing: sputter gold/chromium layer on top of quartz glass layer to prepare antenna radiating element and metal ground layer;

S2: Realizing the antenna radiation element pattern: coating a photoresist on top of the sputtered gold/chrome layer of the quartz glass layer, forming the antenna radiation element pattern by photolithography, and defining the area of the antenna radiation element;

S3: preparing the top radiation element: using a gold/chrome etching solution to remove the gold/chrome layer not covered by the photoresist mask;

S4: Realizing the pattern of the quartz glass support layer at the bottom of the radiation element: coating photoresist on the top of the quartz glass layer, forming a suspended structure pattern on the top of the antenna by photolithography, and defining the suspended structure etching area around the antenna radiation element;

S5: preparing the quartz glass support layer and suspension structure at the bottom of the radiation element: etching the top of the quartz glass to form the quartz glass support layer at the bottom of the radiation element;

S6: realizing the cavity pattern at the bottom of the quartz glass layer: coating a photoresist at the bottom of the quartz glass layer, forming a cavity structure pattern by photolithography, and defining a cavity structure etching area;

S7: preparing a cavity structure at the bottom of the quartz glass layer: etching the bottom of the quartz glass to form a cavity at the bottom of the quartz glass layer;

S8: stripping the photoresist on the top and bottom of the quartz glass layer: completing the preparation of the quartz glass dielectric layer substrate with a suspended structure cavity and the microstrip patch antenna radiation element;

S9: Use the same process to sputter a gold/chromium layer on top of another piece of quartz glass to make a grounding layer: Use a bonding process to connect the grounding layer to the bottom of the quartz glass dielectric layer substrate with a suspended structure cavity to complete the antenna structure;

In the step S5, in order to make the side wall of the suspended structure cavity close to vertical, the upper and lower sides of the quartz glass are etched in sequence during the etching process;

In step S1, the thickness of the quartz glass layer is 300 μm, and the specific process of sputtering the gold/chromium layer on the top of the quartz glass layer is as follows: a sputtering device is used to first sputter a 30 nm thick chromium layer on the front of the 300 μm thick quartz glass layer, and then a 400 nm thick gold layer is sputtered on the chromium layer, and finally the gold/chromium metal film is deposited;

The step S2 is specifically as follows: coating AZP4210 photoresist on the front side of the quartz glass layer, using a coating machine to coat, rotating the coating speed at 3000 rpm for 30 seconds, preparing a 3 μm thick photoresist mask layer, pre-baking at 100° C. for 120 seconds, then using the mask of the top radiation element for exposure, the exposure time is 4 seconds, post-baking at 120° C. for 90 seconds, and maintaining the temperature at 23° C. for development using AZ300MIF developer for 60 seconds, and finally forming a top radiation element pattern;

The specific steps of step S3 are: firstly, etching the gold layer using a potassium cyanide-based solution at room temperature, and then etching the chromium layer using a CR-7 chromium etching solution at room temperature, and finally forming a top radiation element;

The specific steps of step S4 are: coating AZP4210 photoresist on the front side of the quartz glass, using a coating machine to coat, rotating the coating speed at 3000 rpm for 30 seconds, preparing a 3 μm thick photoresist mask layer, pre-baking at a temperature of 100° C. for 120 seconds, then using the mask of the top radiation element for exposure, the exposure time is 4 seconds, post-baking at a temperature of 120° C. for 90 seconds, and maintaining the temperature at 23° C. for development using AZ300MIF developer for 60 seconds, to form a front suspended structure cavity pattern of the quartz glass;

In step S5, SF6 gas is used to etch the front side of the quartz glass layer, the RF stage temperature is 20°C, the gas pressure is 0.4 Pa, the power is 100 W, and the bias voltage is -390;

The specific steps of step S6 are as follows: coating AZP4620 photoresist on the front side of the quartz glass, using a coating machine to coat, rotating the coating speed at 2000rpm for 30 seconds to prepare a 10μm thick photoresist mask layer, pre-baking at 100°C for 120 seconds, then using the mask of the cavity at the bottom of the quartz glass for exposure, the exposure time is 4 seconds, post-baking at 120°C for 90 seconds, and maintaining the temperature at 23°C for development using AZ300MIF developer for 60 seconds, and finally forming a cavity pattern on the back of the radiation element;

In step S7, a mixed solution of 49% hydrofluoric acid and 37% hydrochloric acid in a ratio of 10:1 is used to etch the back side of the quartz glass layer at a temperature of 23° C. and an air pressure of 101.3 Pa to complete the back side suspension structure cavity structure of the quartz glass.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of a suspended structure cavity microstrip patch antenna based on MEMS technology proposed by the present invention;

FIG2 is an exploded schematic diagram of the antenna structure proposed by the present invention;

FIG3 is a schematic top view of the antenna structure proposed by the present invention;

FIG4 is a front cross-sectional schematic diagram of the antenna structure proposed by the present invention;

FIG5 is a right cross-sectional schematic diagram of the antenna structure proposed by the present invention;

FIG6 is a schematic diagram of a method for manufacturing an antenna according to an embodiment of the present invention;

FIG7 is a schematic diagram of the relationship between antenna return loss and frequency according to an embodiment of the present invention;

FIG. 8 is a schematic diagram of the antenna gain-frequency relationship according to an embodiment of the present invention.

Legend: 1. Metal radiation element and microstrip feed line; 2. Suspended structure cavity quartz glass layer; 3. Suspended structure cavity; 4. Metal grounding layer; 5. Quartz glass layer.

Detailed ways

The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Example

As shown in Figure 1, a suspended structure cavity patch antenna based on MEMS technology includes a metal radiation element and a microstrip feed line 1, a suspended structure cavity quartz glass layer 2, a suspended structure cavity 3, a metal grounding layer 4 and a quartz glass layer 5, wherein the metal radiation element and the microstrip feed line 1 are located on the top of the quartz glass layer 5, the suspended structure cavity quartz glass layer 2 and the metal grounding layer 4 are sequentially arranged between the metal radiation element and the microstrip feed line 1 and the quartz glass layer 5 from top to bottom, and the suspended structure cavity 3 is opened through the suspended structure cavity quartz glass layer 2.

As shown in FIG3 , it is a schematic diagram of a top view of a suspended structure cavity microstrip patch antenna in the present invention, in which the metal radiation element and feeder line at the top of the antenna are in the middle, and the quartz glass dielectric layer and the suspended structure are around.

As shown in FIG4 , it is a schematic diagram of a front cross-sectional view of the suspended structure cavity microstrip patch antenna proposed in the present invention, which includes, from top to bottom, a gold/chromium (Au/Cr) layer, a suspended structure cavity quartz glass layer 2, a gold/chromium (Au/Cr) layer, and a quartz glass layer 5. The same materials have the same thickness. A certain thickness of quartz glass is retained under the radiation element at the top of the quartz glass layer 5 as a support layer. The quartz glass in the area surrounding the radiation element is completely etched, and only the quartz glass at the four cantilevers is retained as the support arms of the radiation element.

As shown in Figure 5, it is a schematic diagram of the right cross-sectional view of the suspended structure cavity microstrip patch antenna proposed in the present invention. It can be seen from the figure that the back of the antenna radiating element is a suspended structure, a certain thickness of quartz glass is retained under the radiating element and the feed line as a supporting layer, and the quartz glass in the area around the radiating element is completely etched.

As shown in FIG6 , a method for manufacturing a suspended structure cavity microstrip patch antenna based on MEMS technology includes the following steps:

S1: As shown in FIG6(a), a processing substrate is prepared, and a 430 nm thick gold/chromium (Au/Cr) layer is sputtered on the top of a 300 μm thick quartz glass layer 5 to prepare an antenna radiation element and a grounding layer. Specifically, a 30 nm thick chromium (Cr) layer is first sputtered on the front of the 300 μm thick quartz glass using a sputtering device, and then a 400 nm thick gold (Au) layer is sputtered on the chromium (Cr) layer, and finally a gold/chromium (Au/Cr) metal film is deposited;

S2: As shown in FIG6(b), the antenna radiation element pattern is realized, and the photoresist is coated on the front side of the quartz glass. The antenna radiation element pattern is formed by photolithography, and the area of the radiation element is defined. Specifically, AZP4210 photoresist is coated on the front side of the quartz glass, and a coating machine is used for coating. The coating speed is 3000 rpm for 30 seconds to prepare a 3 μm thick photoresist mask layer, and the pre-baking is maintained at 100°C for 120 seconds, and then the mask of the top radiation element is used for exposure, and the exposure time is 4 seconds. The post-baking is maintained at 120°C for 90 seconds, and the temperature is maintained at 23°C. AZ300MIF developer is used for development, and the development time is 60 seconds, and finally the top radiation element pattern is formed;

S3: As shown in FIG6(c), a top radiation element is prepared, and a gold/chromium (Au/Cr) etching solution is used to remove the gold/chromium (Au/Cr) layer not covered by the photoresist mask. Specifically, a potassium cyanide-based solution is first used to etch the gold (Au) layer at room temperature, and then a CR-7 chromium etching solution (chromium etching solution) is used to etch the chromium (Cr) layer at room temperature, and finally a top radiation element is formed;

S4: As shown in FIG6(d), the quartz glass support layer and the suspension structure pattern at the bottom of the radiation element are realized, a 3 μm thick photoresist is coated on the front of the quartz glass, and a cavity pattern at the top of the antenna is formed by photolithography to define the suspension structure cavity area around the radiation element. Specifically, AZP4210 photoresist is coated on the front of the quartz glass, and a coating machine is used to coat the quartz glass. The coating speed is 3000 rpm for 30 seconds to prepare a 3 μm thick photoresist mask layer. The pre-baking is maintained at 100°C for 120 seconds, and then the mask of the top radiation element is used for exposure. The exposure time is 4 seconds. The post-baking is maintained at 120°C for 90 seconds, and the temperature is maintained at 23°C for development using AZ300MIF developer for 60 seconds to form a suspension structure cavity pattern on the front of the quartz glass.

S5: As shown in FIG6(e), a quartz glass support layer and a suspension structure at the bottom of the radiation element are prepared, and the quartz glass on the front side of the quartz glass that is not covered by the photoresist mask is etched to form a front suspension structure cavity area, and the etching depth is 10 μm. Specifically, SF6 gas is used to etch the front side of the quartz glass layer 5, and the RF stage temperature is 20°C, the gas pressure is 0.4 Pa, the power is 100 W, and the bias voltage is -390 V. In order to make the side wall of the suspension structure cavity close to vertical, the upper and lower sides of the quartz glass are etched in sequence;

S6: As shown in FIG6(f), realize the cavity pattern at the bottom of the quartz glass layer, coat a 10 μm thick photoresist on the back of the quartz glass, form the cavity pattern on the back of the antenna by photolithography, and define the rectangular etching area of the suspended structure cavity on the back of the radiating element. Specifically, coat AZP4620 photoresist on the front of the quartz glass, use a coating machine to coat, and spin coat for 30 seconds at a speed of 2000 rpm to prepare a 10 μm thick photoresist mask layer, bake at 100°C for 120 seconds, and then use the mask of the cavity at the bottom of the quartz glass for exposure, the exposure time is 4 seconds, and the post-baking temperature is maintained at 120°C for 90 seconds, and the temperature is maintained at 23°C for development using AZ300MIF developer for 60 seconds, finally forming the cavity pattern on the back of the radiating element;

S7: As shown in FIG6(g), a cavity structure at the bottom of the quartz glass layer is prepared. The back side of the quartz glass is etched to complete the production of the back suspension structure cavity by using the same etching parameters as those for etching the front side of the quartz glass layer 5. The etching depth is 295 μm. Specifically, a 10:1 mixed solution of 49% hydrofluoric acid (HF) and 37% hydrochloric acid (HCl) is used to etch the back side of the quartz glass layer 5. The temperature is 23° C. and the air pressure is 101.3 Pa. The back side suspension structure cavity structure of the quartz glass is completed.

S8: As shown in FIG6(h), the photoresist on the front and back sides of the antenna quartz glass layer 5 is removed, and the preparation of the substrate of the hollow quartz glass layer 2 with a suspended structure and the microstrip patch antenna radiation element is completed;

S9: As shown in FIG6(i), a 430 nm thick gold/chromium (Au/Cr) layer is sputtered on the front side of another 300 μm thick quartz glass according to the same steps as FIG6(a), and the antenna structure prepared in step FIG6(h) is bonded to the gold/chromium (Au/Cr) layer on the front side of the quartz glass to complete the complete antenna structure.

In the present invention, after step S9, the performance of the suspended structure cavity microstrip patch antenna is simulated and tested using simulation software. As shown in FIG7 , the return loss-frequency test is performed on the suspended structure cavity microstrip patch antenna described in the embodiment. It can be seen that the antenna return loss is lower than -10dB and the impedance bandwidth is 57.87GHz to 62.05GHz (4.18GHz), which has a very wide bandwidth, almost covering the 60GHz ISM band. The return loss at the center frequency of 60GHz reaches -36.2dB, indicating that the antenna of this embodiment is well matched with the feeder line. As shown in FIG8 , the gain-frequency test is performed on the suspended structure cavity microstrip patch antenna described in the embodiment. The antenna gain reaches 9.08dB at the center resonant frequency of 60GHz, and has a high gain greater than 8dB in the working frequency band. Therefore, the antenna of this embodiment has a higher gain.

The thickness of the quartz glass substrate is 300 μm, the thickness of the gold/chromium (Au/Cr) layer is 430 nm, the height of the suspended structure cavity is 295 μm, and the thickness of the quartz glass support layer at the bottom of the radiation element is 5 μm.

The length of the microstrip patch antenna is 2.17 mm and the width is 2.5 mm, the length of the quarter-wavelength impedance transformer is 670 μm and the width is 375 μm, the width of the 50-ohm microstrip transmission line is 588 μm, and the thickness of the dielectric layer is 300 μm.

The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes and apply it to other fields. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims (1)

1. A suspended structure cavity patch antenna based on MEMS technology, comprising a metal radiating element and a microstrip feeder, a suspended structure cavity quartz glass layer, a suspended structure cavity, a metal grounding layer and a quartz glass layer, wherein the metal radiating element and the microstrip feeder are located on the top of the quartz glass layer, the suspended structure cavity quartz glass layer and the metal grounding layer are sequentially arranged between the metal radiating element, the microstrip feeder and the quartz glass layer from top to bottom, and the suspended structure cavity is opened through the suspended structure cavity quartz glass layer; The method for manufacturing the suspended structure cavity microstrip patch antenna based on MEMS technology comprises the following steps: S1: Prepare substrate for processing: sputter gold/chromium layer on top of quartz glass layer to prepare antenna radiating element and metal ground layer; S2: Realizing the antenna radiation element pattern: coating a photoresist on top of the sputtered gold/chrome layer of the quartz glass layer, forming the antenna radiation element pattern by photolithography, and defining the area of the antenna radiation element; S3: preparing the top radiation element: using a gold/chrome etching solution to remove the gold/chrome layer not covered by the photoresist mask; S4: Realizing the pattern of the quartz glass support layer at the bottom of the radiation element: coating photoresist on the top of the quartz glass layer, forming a suspended structure pattern on the top of the antenna by photolithography, and defining the suspended structure etching area around the antenna radiation element; S5: preparing the quartz glass support layer and suspension structure at the bottom of the radiation element: etching the top of the quartz glass to form the quartz glass support layer at the bottom of the radiation element; S6: realizing the cavity pattern at the bottom of the quartz glass layer: coating a photoresist at the bottom of the quartz glass layer, forming a cavity structure pattern by photolithography, and defining a cavity structure etching area; S7: preparing a cavity structure at the bottom of the quartz glass layer: etching the bottom of the quartz glass to form a cavity at the bottom of the quartz glass layer; S8: stripping the photoresist on the top and bottom of the quartz glass layer: completing the preparation of the quartz glass dielectric layer substrate with a suspended structure cavity and the microstrip patch antenna radiation element; S9: Use the same process to sputter a gold/chromium layer on top of another piece of quartz glass to make a grounding layer: Use a bonding process to connect the grounding layer to the bottom of the quartz glass dielectric layer substrate with a suspended structure cavity to complete the antenna structure; In the step S5, in order to make the side wall of the suspended structure cavity close to vertical, the upper and lower sides of the quartz glass are etched in sequence during the etching process; In step S1, the thickness of the quartz glass layer is 300 μm, and the specific process of sputtering the gold/chromium layer on the top of the quartz glass layer is as follows: a sputtering device is used to first sputter a 30 nm thick chromium layer on the front of the 300 μm thick quartz glass layer, and then a 400 nm thick gold layer is sputtered on the chromium layer, and finally the gold/chromium metal film is deposited; The step S2 is specifically as follows: coating AZP4210 photoresist on the front side of the quartz glass layer, using a coating machine to coat, rotating the coating speed at 3000 rpm for 30 seconds, preparing a 3 μm thick photoresist mask layer, pre-baking at 100° C. for 120 seconds, then using the mask of the top radiation element for exposure, the exposure time is 4 seconds, post-baking at 120° C. for 90 seconds, and maintaining the temperature at 23° C. for development using AZ300MIF developer for 60 seconds, and finally forming a top radiation element pattern; The specific steps of step S3 are: firstly, etching the gold layer using a potassium cyanide-based solution at room temperature, and then etching the chromium layer using a CR-7 chromium etching solution at room temperature, and finally forming a top radiation element; The specific steps of step S4 are: coating AZP4210 photoresist on the front side of the quartz glass, using a coating machine to coat, rotating the coating speed at 3000 rpm for 30 seconds, preparing a 3 μm thick photoresist mask layer, pre-baking at a temperature of 100° C. for 120 seconds, then using the mask of the top radiation element for exposure, the exposure time is 4 seconds, post-baking at a temperature of 120° C. for 90 seconds, and maintaining the temperature at 23° C. for development using AZ300MIF developer for 60 seconds, to form a front suspended structure cavity pattern of the quartz glass; In step S5, SF6 gas is used to etch the front side of the quartz glass layer, the RF stage temperature is 20°C, the gas pressure is 0.4 Pa, the power is 100 W, and the bias voltage is -390; The specific steps of step S6 are as follows: coating AZP4620 photoresist on the front side of the quartz glass, using a coating machine to coat, rotating the coating speed at 2000rpm for 30 seconds to prepare a 10μm thick photoresist mask layer, pre-baking at 100°C for 120 seconds, then using the mask of the cavity at the bottom of the quartz glass for exposure, the exposure time is 4 seconds, post-baking at 120°C for 90 seconds, and maintaining the temperature at 23°C for development using AZ300MIF developer for 60 seconds, and finally forming a cavity pattern on the back of the radiation element; In step S7, a mixed solution of 49% hydrofluoric acid and 37% hydrochloric acid in a ratio of 10:1 is used to etch the back side of the quartz glass layer at a temperature of 23° C. and an air pressure of 101.3 Pa to complete the back side suspension structure cavity structure of the quartz glass.