WO2018176267A1

WO2018176267A1 - Method for fabricating perfect absorber

Info

Publication number: WO2018176267A1
Application number: PCT/CN2017/078599
Authority: WO
Inventors: 张昭宇; 韩谞; 何克波
Original assignee: 香港中文大学（深圳）
Priority date: 2017-03-29
Filing date: 2017-03-29
Publication date: 2018-10-04
Also published as: CN107114006A; CN107114006B

Abstract

Disclosed is a method for fabricating a perfect absorber, at least comprising the following steps: 1) sequentially depositing, on a surface of a clean substrate and towards the exterior, a first metal layer, a dielectric layer and a second metal layer; 2) spin-coating an e-beam photoresist on a surface of the second metal layer; 3) performing heat-curing processing on the spin-coated e-beam photoresist; 4) performing exposing and development processing on the heat-cured e-beam photoresist to obtain an unexposed e-beam photoresist area; 5) and performing dry-etching processing on the exposed and developed e-beam photoresist area so as to enable the second metal layer to break and form a plurality of periodic square matrix arrangement structures, and removing the unexposed e-beam photoresist to obtain a perfect absorber. The method for fabricating a perfect absorber does not damage the photoresist, and the lifted-off metal arrays are not distorted.

Description

Title of Invention: Method of Manufacturing Perfect Absorber

Technical field

[0001] The invention belongs to the technical field of electromagnetic wave absorption structures, and particularly relates to a method for manufacturing a perfect absorber.

Background technique

[0002] An electromagnetic wave absorbing structure based on synthetic materials, whose electromagnetic wave parameters and electromagnetic parameters of the surrounding environment can achieve impedance matching, and the absorption rate at a specific wavelength band is 100%, so that the electromagnetic wave absorbing structure is called perfect Absorber.

[0003] Existing perfect absorbers generally use electron beam direct writing (EBL) to generate a periodic structure, specifically a periodic array complementary to the uppermost metal array of the absorber, and then through film deposition and lift-off. A metal array is formed. For example, in the manufacture of a perfect absorber, a metal cylinder is required, and the EBL photoresist is subjected to round hole exposure and development to form a circular hole of the same size as the metal cylinder, and then metal is deposited into the round hole by vapor deposition, and lifted. -off, finally remove the glue and glue, and finally form the structure of the perfect absorber. This method has the problem of difficulty in peeling and distortion of the metal pattern after peeling. For example, to deposit 100 nm of metal, it is necessary to at least 3 to 4 times the thickness of the EBL photoresist to achieve the peeling, and due to the unevenness and orientation of the deposited film defects. If the performance is poor, the peeling will be difficult and the metal pattern will be distorted after peeling. The specific distortion process can be as shown in Fig. 2 after the processing shown in Fig. 1. 1 is a first metal layer 2, a dielectric layer 3, and a photoresist 5 stacked in this order on the surface of the substrate layer 1. On the basis of the structure of FIG. 1, the second metal layer 4 is vapor-deposited. If the metal melting point of the second metal layer 4 is high, surface distortion of the second metal layer 4 as shown in FIG. 2 may be formed, as shown in FIG. In order to avoid excessively high metal temperature of the second metal layer 4, the surface distortion may be too severe, and the thickness of the second metal layer 4 may be thinner, which may not meet the process requirements of the perfect absorber. As shown in FIG. 3; when the metal temperature of the second metal layer 4 is not particularly high, the photoresist layer is not melted, and the second metal layer 4 completely covers the photoresist layer 5, so that the photoresist cannot be peeled off, as shown in FIG. 4; When the metal melting point of the second metal layer 4 is high, and the vapor deposition between the crucibles reaches the required enthalpy, the photoresist layer 5 not only collapses into a hilly shape, but also cannot be peeled off, as shown in FIG.

[0004] In addition, when the metal material of the perfect absorber is tungsten germanium, since the melting point of tungsten is the highest in the metal, the temperature of the film is extremely high during the evaporation process, and the high temperature destroys the pattern that the EBL photoresist has generated, and utilizes Sputtered The deposited film is not suitable for the stripping process. Therefore, it is necessary to propose a new method of manufacturing a perfect absorber.

technical problem

[0005] The present invention provides a perfect absorber for the problems of peeling difficulties and metal pattern distortion which occur in the manufacturing process of a perfect absorber, and the use of tungsten as a metal to have a too high melting point to destroy the electron beam direct writing photoresist pattern. Manufacturing method.

Problem solution

Technical solution

[0006] In order to achieve the above object of the invention, the technical solution of the present invention is as follows:

[0007] A method for manufacturing a perfect absorber includes at least the following steps:

[0008] 1) from the surface of the cleaned substrate, the deposition process of the first metal layer, the dielectric layer and the second metal layer is sequentially performed;

[0009] 2) performing a spin coating process on the surface of the second metal layer;

[0010] 3) performing thermal curing treatment on the spin-coated electron beam photoresist;

[0011] 4) exposing and developing the thermally cured electron beam photoresist to obtain an electron beam photoresist region having no exposure;

[0012] 5) performing dry etching on the electron beam resist region after exposure and development processing, so that the second metal layer is broken to form a plurality of periodic square array structures, and removing the The exposed electron beam photoresist gives a perfect absorber.

Advantageous effects of the invention

Beneficial effect

[0013] The method for manufacturing a perfect absorber provided by the present invention, because the electron beam direct writing technology is not used, avoids the destruction of the photoresist by the deposited film after patterning by the electron beam direct writing technology, and eliminates the pattern distortion phenomenon of the metal array after peeling off. , provides a new method for the manufacture of perfect absorbers.

Brief description of the drawing

DRAWINGS

[0014] FIG. 1 is a semi-finished product of a perfect absorber structure of an unvaporized metal layer produced by a conventional manufacturing method; [0015] FIG. 2 is a perfect absorbent structure made by a conventional manufacturing method;

[0016] FIG. 3 is another perfect absorber structure manufactured by a conventional manufacturing method;

[0017] FIG. 4 is still another perfect absorber structure manufactured by a conventional manufacturing method;

[0018] FIG. 5 is a further perfect absorber structure manufactured by a conventional manufacturing method;

6 is a flow chart of a method for manufacturing a perfect absorber according to an embodiment of the present invention;

7 is a schematic view showing the first step of manufacturing a perfect absorber according to an embodiment of the present invention;

8 is a schematic view showing the second step of manufacturing a perfect absorber according to an embodiment of the present invention;

9 is a schematic view showing the third step of manufacturing a perfect absorber according to an embodiment of the present invention; [0022] FIG.

10 is a schematic view showing the fourth step of manufacturing a perfect absorber according to an embodiment of the present invention;

11 is a schematic view showing a seventh step of manufacturing a perfect absorber according to an embodiment of the present invention; [0024] FIG.

[0025] FIG. 12 is a perspective view of a perfect absorbent body manufactured by the method for manufacturing a perfect absorbent body according to an embodiment of the present invention;

13 is a plan view of a perfect absorber manufactured by the method for manufacturing a perfect absorbent body according to an embodiment of the present invention.

Embodiments of the invention

[0027] In order to make the technical problems, technical solutions, and advantageous effects to be solved by the present invention more clearly, the present invention will be further described in detail below with reference to the embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0028] As shown in FIGS. 6 and 7 to 12, an embodiment of the present invention provides a method of manufacturing a perfect absorber. The method for manufacturing the perfect absorbent body comprises at least the following steps:

[0029] 1) self-cleaning substrate 1 outwardly, the first metal layer 2, the dielectric layer 3 and the second metal layer 4 deposition process, as shown in Figures 7, 8, 9;

[0030] 2) performing spin coating treatment of the electron beam photoresist 5 on the surface of the second metal layer 4, as shown in FIG. 10; [0031] 3) performing spin coating of the electron beam resist 5 Heat curing treatment;

[0032] 4) exposing and developing the thermally cured electron beam photoresist 5 to obtain an electron beam photoresist region having no exposure;

[0033] 5) performing a dry etching process on the electron beam resist 5 region after the exposure and development processes, so that the second metal layer 4 is broken to form a plurality of periodic square array structures, as shown in FIG. And removing the unexposed electron beam photoresist 5 to obtain a perfect absorber, as shown in FIG. [0034] In any embodiment, the substrate 1 is any one of quartz, silicon wafer, nickel, copper, and tungsten, and the substrate 1 serves as a space for growing a thin film.

[0035] Before the deposition treatment on the surface of the substrate 1, the substrate 1 needs to be cleaned to ensure that the surface of the substrate 1 is clean, and impurities are not adhered to the surface to adversely affect the performance of the absorber.

[0036] Preferably, the metal used for the first metal layer 2 is tungsten, and the metal used for the second metal layer 4 is also tungsten.

Since the melting point of tungsten is the highest among all metals, when tungsten is used in the manufacture of a perfect absorber, if other manufacturing methods are used, tungsten will melt the electron beam photoresist during the evaporation process, so that the electron beam photoresist The formed pattern is broken, resulting in difficulty in peeling off the electron beam resist, and the pattern of the metal tungsten after the peeling is distorted, which deteriorates the absorption efficiency of the perfect absorber. Moreover, when other metal crucibles are used, the melting point of other metals is not as high as that of tungsten metal, so the perfect absorber produced is not as effective as the perfect absorber made of tungsten metal.

[0037] Further preferably, the thickness of the first metal layer 2 is not less than 200 nm, the main function is to reduce the transmittance to zero, and 200 nm is a minimum thickness that ensures that the transmittance is almost zero. The thickness of the two metal layers 4 is 100-140 nm, which can make the effect of reducing reflection more obvious, but below or above this interval will obviously enhance the surface reflectance, which is not conducive to absorption.

[0038] Further preferably, the first metal layer 2 has a thickness of 200 to 300 nm.

[0039] Preferably, the deposition process of the first metal layer 2 is performed by magnetron sputtering, the magnetron sputtering power is 300~400 W, and the deposition time is 15~25 min; the deposition process of the second metal layer 4 is adopted. For magnetron sputtering, the magnetron sputtering power is 300~400W, and the deposition time is 6~10min.

[0040] Preferably, the material of the dielectric layer 3 is any one of silicon dioxide, silicon nitride, MgF ₂ , and A1 ₂ 0 ₃ . The dielectric layer 3 is a prerequisite for generating magnetic resonance. Preferably, the thickness is 60-80 nm, and the thickness can make the upper and lower free electrons in the metal layer interact with each other, that is, they are coupled to each other. Below or above this thickness interval, the effect is too strong or too weak to be A resonance peak is generated.

[0041] Preferably, the deposition process of the dielectric layer 3 is performed by electron beam evaporation, and the evaporation rate is 3 to 5 angstroms/second, and the film thickness is relatively uniform and the surface roughness is low.

[0042] Preferably, the electron beam photoresist 5 is a positive gel, and the positive gel is developed in the exposure zone by using a crucible, and an isolated hole can be obtained with high resolution and no pollution to the environment.

[0043] More preferably, the positive adhesive is ZEP520A, and the performance of dry etching is better. [0044] Preferably, the thickness of the electron beam photoresist 5 spin-coated is 200 to 250 nm.

[0045] Preferably, the heat curing temperature is 180 to 200 ° C, and the heat curing time is 1.5 to 4.5 minutes.

[0046] Preferably, the thermally cured photoresist is exposed and developed, and a photolithography machine is used, and the photolithography machine adopts a NanoBeam NB5 model lithography machine. The lithography machine device can set the corresponding program, and the exposure and development graphics are performed according to the program settings. In the embodiment of the invention, an unexposed circular area and other areas of exposure may be formed.

[0047] Preferably, the dry etching etches between 130 and 140 s, the gas pressure is 15 to 20 mTorr, and the gas is 0 ₂

15~25sccm, SF ₆ 90~100sccm, source power 50~100W, bias power 20~50W.

[0048] Still more preferably, the second metal layer 4 of the perfect absorber is a plurality of cylinders arranged in a periodic square array, the cylinder period is 500-600 nm, and the diameter of the cylinder is 250-350 nm. The structure arranged in a cylinder, of course, the second metal layer 4 may also have a prismatic or square structure. Only in all structures, the cylinder is easy to process, and surface plasma resonance can be excited between the second metal layer 4 and the air, and coupled magnetic resonance can be generated between adjacent cells.

[0049] In the most preferred embodiment, the cylinder has a diameter of 300 nm and the cylinder period in the array is 500 nm.

[0050] The method for manufacturing a perfect absorber provided by the above embodiments of the present invention, since the electron beam direct writing technology is not used, the destruction of the photoresist by the deposited film after the patterning of the electron beam direct writing technology is avoided, and the metal array after stripping is eliminated. Pattern distortion provides a new way to create a perfect absorber.

[0051] In order to better illustrate the method of manufacturing a perfect absorbent body provided by an embodiment of the present invention, the following further explains by way of various embodiments.

Embodiment 1

[0053] A method of manufacturing a perfect absorber, comprising the steps of:

[0054] 1) cleaning the quartz substrate, so that the oil stain on the quartz surface is removed, and drying the quartz, to be used; [0055] 2) using a magnetron sputtering method, on the surface of the clean quartz, 300W Power deposition of a first tungsten film of 250 nm (ie, the first metal layer), depositing between turns for 20 minutes, as shown in FIG. 7;

[0056] 3) using a method of electron beam evaporation, depositing a 60 nm layer of a silicon dioxide dielectric layer at a rate of 3 Å/sec on the surface of the first tungsten film, as shown in FIG. 8;

[0057] 4)

Using a magnetron sputtering method, depositing 100 nm at a power of 300 W on the surface of the above-mentioned silicon dioxide dielectric layer a second tungsten film (ie, a second metal layer), deposited for 8 minutes, as shown in FIG. 9;

[0058] 5) on the surface of the second tungsten film spin-coated ZEP520A (electron beam photoresist), ZEP520A spin coating thickness of 220nm, as shown in Figure 10, and then thermal curing, thermal curing temperature of 180 ° C, Heat curing time is 3 minutes;

[0059] 6) using a lithography machine to expose and develop the surface of the ZEP520A, so that the surface of the ZEP520A has a circular area that is not exposed and developed, and other areas that are exposed and developed;

[0060] 7) using a dry etching method, dry etching the ZEP520A mask as a mask, etching the second tungsten film, forming a second tungsten film into a cylindrical structure, and then removing the ZEP520A to obtain a perfect The absorber is shown in Figures 11 and 12.

Example 2

[0062] A method of manufacturing a perfect absorbent body, comprising the steps of:

[0063] 1) cleaning the quartz substrate, so that the oil stain on the quartz surface is removed, and the quartz is dried, and is used;

[0064] 2) using a method of magnetron sputtering, depositing a 200 nm first tungsten film (ie, a first metal layer) at a power of 350 W on the surface of the clean quartz, and depositing a turn for 15 minutes;

[0065] 3) using a method of electron beam evaporation, depositing a 70 nm layer of a silicon dioxide dielectric layer on the surface of the first tungsten film at a rate of 3 Å/sec;

[0066] 4) using a method of magnetron sputtering, depositing a 120 nm second tungsten film (ie, a second metal layer) at a power of 350 W on the surface of the above-mentioned silicon dioxide dielectric layer, depositing a turn for 10 minutes;

[0067] 5) spin-coated ZEP520A (electron beam photoresist) on the surface of the second tungsten film, the spin coating thickness of ZEP520A is 220 nm, as shown in FIG. 10, and then thermally cured, the heat curing temperature is 2000 ° C, Heat curing

3 minutes;

[0068] 6) using a lithography machine to expose and develop the surface of the ZEP520A, so that the surface of the ZEP520A has a circular area that has not been exposed and developed, and other areas that are exposed and developed;

[0069] 7) using a dry etching method, performing dry etching on the mask after exposure of ZEP520A, etching the second tungsten film, forming a second tungsten film into a cylindrical structure, and then removing the ZEP520A to obtain a perfect The absorber is shown in Figures 11 and 12.

Example 3

[0071] A method of manufacturing a perfect absorber, comprising the steps of: [0072] 1) cleaning the quartz substrate, so that the oil stain on the quartz surface is removed, and the quartz is dried, and is used;

[0073] 2) using a method of magnetron sputtering, depositing a 300 nm first tungsten film (ie, a first metal layer) at a power of 400 W on the surface of the clean quartz, depositing a turn for 25 minutes;

[0074] 3) using a method of electron beam evaporation, depositing a 50 nm layer of a silicon dioxide dielectric layer at a rate of 3 Å/sec on the surface of the first tungsten film;

[0075] 4) using a method of magnetron sputtering, depositing a second tungsten film (ie, a second metal layer) of 80 nm at a power of 400 W on the surface of the above-mentioned silicon dioxide dielectric layer, depositing a turn for 10 minutes;

[0076] 5) spin-coating ZEP520A (electron beam photoresist) on the surface of the second tungsten film, the spin coating thickness of ZEP520A is 200 nm, as shown in FIG. 10, and then thermally curing, the heat curing temperature is 180 ° C, Heat curing daytime is 4 minutes;

[0077] 6) using a lithography machine to expose and develop the surface of the ZEP520A, so that a surface of the ZEP520A surface that is not exposed and developed and other areas that are exposed and developed;

[0078] 7) dry etching is used to dry-etch ZEP520A as a mask, etch the second tungsten film, form a second tungsten film into a cylindrical structure, and then remove ZEP520A to obtain perfect The absorber is shown in Figures 11 and 12.

The above description is only the preferred embodiment of the present invention, and is not intended to limit the present invention, and any modifications, equivalents, and improvements made within the spirit and scope of the present invention should be included in the present invention. Within the scope of protection of the invention.

Claims

Claim

A method for manufacturing a perfect absorber, characterized in that it comprises at least the following steps:

1) depositing a first metal layer, a dielectric layer and a second metal layer in sequence from a surface of the cleaned substrate;

2) performing a spin coating process on the surface of the second metal layer;

3) performing thermal curing treatment on the spin-coated electron beam photoresist;

4) exposing and developing the thermally cured electron beam photoresist to obtain an electron beam photoresist region having no exposure;

5) performing a dry etching process on the electron beam resist region after exposure and development processing, so that the second metal layer is broken to form a plurality of periodic square array structures, and the unexposed is removed. Electron beam photoresist to obtain a perfect absorber.

The method of manufacturing a perfect absorber according to claim 1, wherein: the first metal layer is a tungsten layer, and the second metal layer is a tungsten layer; and the dielectric layer is a silicon dioxide layer and nitrided Silicon layer, MgF ₂ , Al ₂ 0 ₃

Any one of the first metal layers having a thickness of 200 to 300 nm, the dielectric layer having a thickness of 60 to 80 nm, and the second metal layer having a thickness of 100 to 140 nm.

The method of manufacturing a perfect absorber according to any one of claims 1 to 2, wherein the second metal layer is a cylinder arranged in a periodic square array, and the period of the cylinder is 500 nm. ~600nm, the diameter of the cylinder is 250~350nm.

The method of manufacturing a perfect absorber according to any one of claims 1 to 3, wherein: the deposition process of the first metal layer is performed by magnetron sputtering, and the magnetron sputtering power is 300~.

400W, the deposition time is 15~25min; the deposition of the dielectric layer is by electron beam evaporation, the evaporation rate is ₃ ~ 5 Å / sec; the deposition of the second metal layer is by magnetron sputtering

The magnetron sputtering power is 300~400W, and the deposition time is 6~10min.

The method of manufacturing a perfect absorbent body according to claim 1, wherein: the dry etching gas pressure is 15-20 mTorr, the gas is 0 ₂ 15~25 sccm, the SF _{6 is} 90-100 sccm, and the source power is 50-100 W. The bias power is 20~50W, and the etching time is 130~140s.

A method of manufacturing a perfect absorbent body according to claim 1, wherein: said thermosetting The temperature is 170 to 200 ° C, and the heat curing time is 1.5 to 4.5 minutes.

[Claim 7] The method of manufacturing a perfect absorber according to claim 1, wherein: the electron beam resist is a positive gel; and the positive gel is ZEP520A.

[Claim 8] The method for producing a perfect absorbent body according to claim 1, wherein the developing treatment is carried out by using pentyl acetate for 2 to 4 minutes and isopropanol for 1 to ₃ minutes.

[Claim 9] The method of manufacturing a perfect absorbent body according to claim 1, wherein the spin-coated electron beam resist has a thickness of 200 to 250 nm.

The method of manufacturing a perfect absorbent body according to claim 1, wherein the substrate is any one of quartz, silicon wafer, nickel, copper, and tungsten.