CN114858754A - Novel refractive index biosensor and manufacturing method thereof - Google Patents

Abstract

A novel refractive index biosensor and a manufacturing method thereof relate to the technical field of bio-optical sensing and integrated optical devices, and particularly belong to the novel refractive index biosensor and the manufacturing method thereof. The microstructure is characterized by comprising a medium substrate and a superstructure, wherein the superstructure is a microstructure unit formed by all-medium materials, and a plurality of microstructure units are distributed on the medium substrate in a matrix manner and are periodically arranged in the direction of X, Y. The application of the invention solves the problems of high ohmic loss, high manufacturing cost and incompatibility with CMOS in the metal micro-nano structure, thereby realizing the performance of the optical refractive index biosensor with high sensitivity.

Description

Novel refractive index biosensor and manufacturing method thereof

Technical Field

The invention relates to the technical field of biological optical sensing and integrated optical devices, in particular to a novel refractive index biosensor and a manufacturing method thereof.

Background

In recent years, optical bio-refractive index sensors are considered to be one of important devices in optical bio-detection research due to their advantages of high sensitivity, high precision, high reliability and high detection speed. With the rapid development of micro-nano processing technology, the types of optical biological refractive index sensors are also changing day by day, for example, various optical biological refractive index sensing devices prepared by using fiber gratings, plasma waveguides, superstructures and the like. Among them, the optical bio-refractive index sensor based on the superstructure is considered as the first choice for label-free, on-chip integration and ultra-sensitive sensing due to its stronger light capturing capability and smaller volume.

Conventional optical bio-refractive index sensors mainly use metal-based plasmonic nanostructures to achieve the fano resonance, but the inherent high ohmic losses, high manufacturing costs and incompatibility with Complementary Metal Oxide Semiconductor (CMOS) technology make the sensitivity of the sensor very low. The advent of all-dielectric superstructures solved these problems. The all-dielectric superstructure has the characteristics of low loss, easy adjustment and compatibility with CMOS technology, and simultaneously supports ultrahigh sensitivity, thereby providing a new approach for realizing high-performance, small-floor-area and highly-integrated optical devices.

Due to the Fano resonance, a narrower spectrum and higher field intensity can be generated, and better sensitivity is realized, so that the Fano resonance device is widely concerned by researchers. The Fano resonance is caused by destructive interference between a discrete state and a continuous state, the Fano resonance-based all-dielectric superstructure optical biological refractive index sensor utilizes the enhancement of a great electromagnetic field generated by the Fano resonance at the resonance frequency, has high sensitivity, avoids ohmic loss generated by materials, and is a research hotspot in the field of the current optical biological refractive index sensor.

In summary, based on the current research situation of the optical refractive index sensor and the advantages of the all-dielectric superstructure and Fano resonance of the high refractive index material, the inventors propose a novel refractive index biosensor.

Disclosure of Invention

The invention aims to provide a novel refractive index biosensor and a manufacturing method thereof, so as to achieve the purposes of avoiding ohmic loss generated by materials and realizing the performance of the optical refractive index biosensor with high sensitivity.

The invention provides a novel refractive index biosensor which is characterized by comprising a medium substrate and a superstructure, wherein the superstructure is a microstructure unit formed by all-dielectric materials, and a plurality of microstructure units are distributed on the medium substrate in a matrix manner and are periodically arranged in the direction of X, Y.

Further, the dielectric substrate material is silicon dioxide, the superstructure material is monocrystalline silicon, and the microstructure unit comprises two asymmetric silicon cylinders.

Further, the arrangement period of microstructure unit X, Y direction is 700 nm; the radius of the silicon cylinder is 100nm and 60nm respectively; the distance between the circle centers of the two silicon cylinders is 300 nm; the silicon cylinder height was 150 nm.

Furthermore, when incident light irradiates on the superstructure unit array, electromagnetic waves interact with the microstructure units, three narrow-line-width Fano resonance peaks appear on a transmission spectrum, and the working wavelength of the sensor is 800nm-1000 nm.

The invention provides a manufacturing method of a novel refractive index biosensor, which is characterized by comprising the following steps:

step 1: washing the silicon dioxide substrate by using a deionized water solution to remove pollutants;

step 2: depositing a silicon thin film on a silicon dioxide substrate by using a low pressure chemical vapor deposition method;

and step 3: uniformly spin-coating photoresist on the silicon film and baking;

and 4, step 4: projecting a pattern by an electron beam exposure technology, irradiating a region to be etched, and not exposing a corresponding silicon cylindrical region by an electron beam;

and 5: carrying out development treatment on the photoresist remained at the corresponding position after electron beam exposure, immersing the wafer in an inorganic weak alkaline aqueous solution, and carrying out high-temperature baking after soaking in a developing solution to harden the photoresist without an electron beam exposure area so as to have corrosion resistance;

step 6: obtaining a silicon cylindrical array after etching by inductively coupled plasma;

and 7: and removing the photoresist, and cleaning by using plasma to obtain the superstructure refractive index biosensor.

The novel refractive index biosensor and the manufacturing method thereof provided by the invention solve the problems of high ohmic loss, high manufacturing cost and incompatibility with CMOS (complementary metal oxide semiconductor) in a metal micro-nano structure. A high-sensitivity Fano peak is excited by combining the BIC theory, and a silicon-based material is used for replacing a metal material in the superstructure, so that the high-sensitivity optical refractive index biosensor performance is realized. The all-dielectric superstructure is based on the Mie's resonance principle, when a plane wave along the negative direction of the z axis is vertically incident on the all-dielectric superstructure, the optical field of the all-dielectric superstructure is mainly bound inside a device, the interaction between light inside the device and substances is favorably enhanced, and three sharp Fano resonances appear in a transmission spectrum. The invention has the following positive effects:

1. the all-dielectric superstructure has no ohmic loss, no biotoxicity, difficult corrosion, denaturation and long service life.

2. Three sharp Fano resonances are generated in the transmission spectrum to facilitate detection and measurement, and a plurality of detection points are provided.

3. The superstructure uses all-dielectric materials, is compatible with the COMS technology, has low manufacturing cost, and is expected to realize large-scale integrated production.

4. The optical biological refractive index sensor can be applied to the related fields of gas, liquid, biological sensing and the like, and can bring great convenience to industrial experimental measurement.

Drawings

FIG. 1 is a top view of the overall structure of the present invention;

FIG. 2 is a side view of the overall structure of the present invention;

FIG. 3 is a top view of a microstructure unit of the present invention;

FIG. 4 is a process flow diagram of the present invention;

fig. 5 shows the transmission spectra of incident plane waves of two silicon cylinders of the microstructure unit of the present invention in the symmetric (R ═ 100nm) and asymmetric (R ═ 100nm, R ═ 60nm) states;

FIG. 6 is a transmission curve of the resonance mode of the invention at a first Fano resonance (first dip) under different refractive indexes of the medium to be measured;

FIG. 7 is a transmission curve of the resonance mode of the present invention at the second and third Fano resonances (second dip, third dip) with different refractive indexes of the medium to be measured;

FIG. 8 is a graph showing the variation of the resonant positions of three resonant modes at different refractive indexes according to the present invention.

Detailed Description

As shown in fig. 1-3, the novel refractive index biosensor provided by the invention is specifically composed of a dielectric substrate 1 and a superstructure 2 which are sequentially stacked from bottom to top. Specifically, the superstructure is a microstructure unit made of all-dielectric material, and a plurality of microstructure units are distributed on the dielectric substrate in a matrix manner and are periodically arranged in the direction X, Y. The medium substrate material is silicon dioxide, the superstructure material is monocrystalline silicon, and the microstructure unit comprises two asymmetric silicon cylinders. In the embodiment of the present invention, the arrangement period of microstructure unit X, Y is 700 nm; the radius of the silicon cylinder is 100nm and 60nm respectively; the distance between the circle centers of the two silicon cylinders is 300 nm; the silicon cylinder height was 150 nm. When incident light irradiates on the superstructure unit array, electromagnetic waves interact with the microstructure units, three narrow-line-width Fano resonance peaks appear on a transmission spectrum, and the working wavelength of the sensor is 800nm-1000 nm.

As shown in fig. 4, the method for manufacturing a novel refractive index biosensor provided by the present invention specifically includes the following steps:

step 1: washing the silicon dioxide substrate by using a deionized water solution to remove pollutants;

step 2: depositing a silicon thin film on a silicon dioxide substrate by using a Low Pressure Chemical Vapor Deposition (LPCVD) method;

and step 3: uniformly spin-coating the photoresist 3 on the silicon film and baking;

and 4, step 4: projecting a pattern by an electron beam exposure technology, irradiating a region to be etched, and not exposing a corresponding silicon cylindrical region by an electron beam;

and 5: carrying out development treatment on the photoresist remained at the corresponding position after electron beam exposure, immersing the wafer in an inorganic weak alkaline aqueous solution, and carrying out high-temperature baking after soaking in a developing solution to harden the photoresist without an electron beam exposure area so as to have corrosion resistance;

step 6: etching by Inductively Coupled Plasma (ICP) to obtain a silicon cylindrical array;

and 7: and removing the photoresist, and cleaning by using plasma to obtain the superstructure refractive index biosensor.

In the transmission spectrum of the incident plane wave of the two silicon cylinders of the microstructure unit of the present invention in the symmetric (R ═ 100nm) and asymmetric (R ═ 100nm, R ═ 60nm) states as shown in fig. 5, when the symmetry is disturbed by the structural break, the radiation continuum interacts with the non-radiation bound state and leaks. The symmetry of the interaction is matched with that of free space polarization, the spatial symmetry matching of the BIC mode and incident polarization is compensated, the BIC mode is allowed to radiate outwards under the polarization excitation of incident light, and finally high-sensitivity Fano resonance is excited. We introduce a symmetry break into the fully symmetric nanopore array, and at r 120nm, these two BIC modes are converted into two quasi-BIC modes that are radiation and have high sensitivity.

In the transmission spectrograms of the resonance mode of the invention at the first (first dip), the second (second dip) and the third (third dip) Fano resonance positions under different refractive indexes of the medium to be measured, the refractive indexes of the corresponding detection substances are 1.31, 1.32, 1.33, 1.34 and 1.35 respectively as shown in fig. 6 and 7. When the material to be detected filled in the super-surface structure changes, the effective refractive index of the structure also changes, so that the position of a resonance peak is correspondingly changed, the change of the refractive index can be obtained through the change of the resonance wavelength, the sensing detection of the refractive index of the substance to be detected is completed, and the transverse movement phenomenon of the resonance peak in the transmission spectrogram is specifically referred to in fig. 6 and 7.

As shown in fig. 8, the relationship between the resonant wavelength of the refractive index sensor and the medium with different refractive indexes can be obtained from the variation curve of the resonant positions of the three resonant modes under different refractive indexes, where λ is the resonant wavelength of the resonant mode, and the abscissa is the refractive index n of the medium to be measured. The sensitivity of the sensing device is S ═ delta lambda/delta n, wherein delta lambda is the change of the Fano resonance wavelength, and delta n is the change of the refractive index of the medium. Three resonance modes appearing in the transmission spectrogram are First dip, Second dip and Third dip respectively, and for the First dip, the delta lambda is 1.085nm, and the delta n is 0.01, and S (First dip) is calculated to be 108.5 nm/RIU; s (Second dip) 226.5nm/RIU was calculated for Second dip, Δ λ 2.265nm and Δ n 0.01; for Third dip, Δ λ is 2.425nm, Δ n is 0.01, and s (Third dip) is 242.5 nm/RIU.

In summary, simulation experiments prove that the specific implementation case of the asymmetric silicon cylinder-based multi-Fano resonance all-dielectric superstructure optical biological refractive index sensor can induce three high-performance Fano resonances to provide multiple detection points. The invention can realize the detection of the substances to be detected of the gas and the liquid with different refractive indexes, has the characteristics of low cost, simple structure, real-time monitoring, no need of calibration and the like, and can play an important role in the fields of chemistry, medical treatment, integrated optics and the like.

Claims (5)

1. The novel refractive index biosensor is characterized by comprising a medium substrate and a superstructure, wherein the superstructure is a microstructure unit formed by all medium materials, and a plurality of microstructure units are distributed on the medium substrate in a matrix manner and are periodically arranged in the direction of X, Y.

2. The novel refractive index biosensor as claimed in claim 1, wherein the dielectric substrate material is silicon dioxide, the superstructure material is single crystal silicon, and the microstructure unit comprises two asymmetric silicon cylinders.

3. The novel refractive index biosensor as claimed in claim 2, wherein the arrangement period of the microstructure units X, Y is 700 nm; the radius of the silicon cylinder is 100nm and 60nm respectively; the distance between the circle centers of the two silicon cylinders is 300 nm; the silicon cylinder height was 150 nm.

4. The novel refractive index biosensor as claimed in claim 3, wherein when incident light is irradiated on the superstructure unit array, electromagnetic waves interact with the microstructure units, three narrow linewidth Fano resonance peaks appear on the transmission spectrum, and the sensor of the present invention has an operating wavelength of 800nm-1000 nm.

5. A manufacturing method of a novel refractive index biosensor is characterized by comprising the following steps:

step 1: washing the silicon dioxide substrate by using a deionized water solution to remove pollutants;

step 2: depositing a silicon thin film on a silicon dioxide substrate by using a low pressure chemical vapor deposition method;

and step 3: uniformly spin-coating photoresist on the silicon film and baking;

and 4, step 4: projecting a pattern by an electron beam exposure technology, irradiating a region to be etched, and not exposing a corresponding silicon cylindrical region by an electron beam;

and 5: carrying out development treatment on the photoresist remained at the corresponding position after electron beam exposure, immersing the wafer in an inorganic weak alkaline aqueous solution, and carrying out high-temperature baking after soaking in a developing solution to harden the photoresist without an electron beam exposure area so as to have corrosion resistance;

step 6: obtaining a silicon cylindrical array after etching by inductively coupled plasma;

and 7: and removing the photoresist, and cleaning by using plasma to obtain the superstructure refractive index biosensor.

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