A multi-patterning nanosphere lithography method with embedded layer triggering

Abstract

The present invention provides a method for embedded-layer-triggered multi-patterning nanosphere lithography. By inserting an embedded layer of the same material between the nanospheres and the wafer in nanosphere lithography, the RIE etching process simultaneously has the effects of isotropic and anisotropic etching. Therefore, under the combined action of the nanospheres and the embedded layer, various structures can be formed through a single etching step, including nano plates, nanomushrooms, nano pillars, nano needles, etc. In addition, the size, period, and aspect ratio of individual structural units can be precisely controlled through etching conditions and relative dimensions. It has created a precedent in lithography technology for preparing structures with a secondary structure where the size of the top layer structure is larger than that of the bottom layer structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of micro-nano processing, and mainly relates to an embedded layer-triggered multi-patterning nanosphere lithography method applicable to silicon crystal processing. Background Art

[0002] Surface arrays with periodic structures have extensive applications in the fields of energy conversion, water collection, plasmonic components, anti-reflection surfaces, anti-fogging, and biomedicine. Among them, the preparation of multi-patterned periodic structures, especially the patterning of large-area and scalable silicon wafers, is of great significance. The structures of nanocolumns, nanocones, and nanoneedle arrays with highly adjustable structures have excellent anti-reflection performance, cell membrane penetration, and droplet manipulation performance due to their localization effect on electromagnetic fields, mechanical penetration effect, and highly adjustable special wetting properties, and are widely used in fields such as solar cells, intracellular drug delivery, and surface-enhanced Raman spectroscopy. Although great progress has been made in the preparation methods of these array structures in recent years, simple and scalable manufacturing, the evolution of multiple patterns, and precise morphology control are still a challenge.

[0003] Periodic structures on silicon wafers are usually manufactured through complex processes, including metal-assisted chemical etching (MACE), reactive ion etching (RIE), and standard lithography techniques of coating, masking, exposure, and development. In addition, additive manufacturing processes such as focused ion beam etching (FIB) and electron beam lithography (EBL) face problems of high cost and scalability. Most importantly, most of these technologies only involve the manufacture of one type of structure or have complex processing procedures when manufacturing multiple patterns. Therefore, it is of great significance to develop a scalable multi-patterning manufacturing technology with a simple procedure. Nanosphere lithography (NSL) is a technology that uses a monolayer of closely packed nanospheres as a mask to etch or add structures on the underlying substrate. Its simplicity, scalability, and low cost have made it widely used in the manufacture of periodic structures. However, most of the currently used nanosphere lithography technologies only involve the manufacture of one type of structure, and it is still challenging to manufacture multiple patterns in a single manufacturing process. Summary of the Invention

[0004] In view of this, we propose a wafer-level multi-patterning micro-nano structure manufacturing technology, named Spacer triggered nanosphere lithography (ST-NSL). Compared with the traditional nanosphere lithography technology, the ST-NSL technology can remove the residual impurities on the surface through a simple one-step etching and ultrasonic post-treatment, achieving the highly adjustable fabrication of multiple patterns ( Figure 1 ). Compared with other studies, the ST-NSL technology inserts a spacer between the nanosphere and the wafer in the nanosphere lithography, and the nanosphere and the spacer are made of the same material. Due to the same surface material in the RIE etching, the manufacturing process has the effects of both isotropic and anisotropic etching at the same time. The anisotropic etching of RIE forms nano-pillars and nano-cones similar to traditional nanosphere lithography on the silicon wafer after penetrating the spacer. At the same time, due to the selectivity ratio during the etching of the spacer, nanosphere, and wafer, the nanosphere acts as a reducible mask, inducing the anisotropic etching of the wafer and the isotropic etching of the spacer and nanosphere. Therefore, under the combined action of the nanosphere and the spacer, various structures defined by the relative sizes of the nanosphere and the spacer are formed at the top of the structure. Subtle changes in the etching conditions (the selectivity ratio of the nanosphere, spacer, and wafer) make it possible to pattern various structures such as nano-mushroom, nano-tower, nano-pillar, nano-pencil, nano-cone, and nano-needle arrays. In addition, the size, period, and aspect ratio of a single structural unit can be precisely controlled by the etching conditions and the sizes of the mask and spacer. More importantly, in the current lithography technology, there is no precedent for preparing a structure with a secondary structure and the top-layer structure size larger than the bottom-layer structure size.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A spacer-triggered multi-patterning nanosphere lithography method uses a sequentially arranged spacer layer and nanosphere layer as masks, and the spacer layer and the nanosphere layer are made of the same material.

[0007] Among them, the ratio of the particle size of the nanospheres in the nanosphere layer to the thickness of the spacer layer can be 5:1 to 3:5, preferably 3:1 to 3:5; specifically, the particle size of the nanospheres in the nanosphere layer can be 100 nm - 600 nm, more preferably 300 nm - 500 nm, and the thickness of the spacer layer can be 100 nm - 600 nm, more preferably 100 nm - 300 nm.

[0008] Among them, the RIE etching method is adopted, the etching atmosphere is a mixed atmosphere of CHF3 and SF6 / O2, the atmosphere flow rate is 40 sccm - 80 sccm, and the etching rate parameter is the etching time of 50 s - 700 s under the power of 100 W - 200 W.

[0009] Furthermore, the flow ratio of SF6 / O2 in the SF6 / O2 mixed atmosphere is preferably (7 ± 1):1.

[0010] Furthermore, cyclic etching or non-cyclic etching is adopted. Cyclic etching includes at least 1 cycle process with an etching duration of (50 s ± 20 s) per cycle and an interval duration of (10 s ± 5 s) per cycle during the whole etching process. Preferably, the whole etching process entirely adopts a cyclic process with an etching duration of (50 s ± 20 s) per cycle and an interval duration of (10 s ± 5 s) per cycle.

[0011] Among them, the materials of the spacer layer and the nanosphere layer are SiO2, and the substrate is silicon.

[0012] Among them, the multi-patterning at least includes four sequential evolution stages of nano plate, nano mushroom, nano pillar, and nanoneedle.

[0013] Furthermore, the multi-patterning further includes one or more of the following evolution stages: the evolution stage of nano pillar@reentrant between nano plate and nano mushroom; the single or sequential evolution stages of nano tower and nano cone between nano mushroom and nano pillar; the evolution stage in which nano pencil appears as a special case during at least a certain period in the nano pillar stage.

[0014] The present invention also provides the product obtained by the above-mentioned inlay-triggered multi-patterning nanosphere lithography method, and the applications of the product in anti-reflection materials, superhydrophobic materials, and SERS detection.

[0015] The beneficial effects of the present invention are:

[0016] The ST-NSL technology has successfully achieved the evolution of multiple patterns in a single etching step, including nano pillar@reentrant, nano mushroom, nano pillar, nano cone, nano pencil, nano needle, etc. All structures are fabricated under a single condition and in a single step. The surface pattern can be highly regulated by controlling the sizes of the spacer and nanosphere. Additionally, by adjusting the etching atmosphere, power, and cyclic and non-cyclic etching, highly controllable fabrication of surface array structure parameters can be achieved. Further, the application capabilities of its anti-reflection performance, light trapping performance, special wettability regulation, and SERS detection are demonstrated through the application of several structures, proving the wide application potential of this technology in multiple disciplines and fields. Description of the Drawings

[0017] Figure 1 Comparison between traditional lithography technology and the ST-NSL of the present invention. Among them, a) Comparison of the single pattern preparation process of traditional lithography technology with the present scheme, b) One-step multi-pattern evolution process of the embedded layer-triggered nanosphere lithography technology ST-NSL proposed in this article, c) Dynamic mask etching mechanism of the present invention.

[0018] Figure 2 Multi-patterning evolution mechanism of ST-NSL.

[0019] Figure 3 Comparison of pattern evolution under cyclic etching and non-cyclic etching. Among them, a) Template used for etching. b), c), d) Sequential evolution of cyclic etching, e) Pre-treatment before evolution comparison, f), g), h) Sequential evolution of non-cyclic etching. The scale bar is 1μm.

[0020] Figure 4 Etching products under different etching times under CHF3 / O2 atmosphere conditions. Among them, a) - d) Different etching times of 50×8s, 50×10s, 50×12s, 50×14s are used respectively. The scale bar is 1μm.

[0021] Figure 5 Dependence of etching structure on atmosphere, power, and flow rate conditions. All the heights marked are the silicon pillar parts below. a1 - a6, Etching morphology of CHF3 under a flow rate of 40sccm and a power of 200W. b1 - b6, Etching morphology of SF6 / O2 under a flow rate of 35 / 5sccm and a power of 200W. c1 - c6, Etching morphology of SF6 / O2 under a flow rate of 35 / 5sccm and a power of 100W. d1 - d6, Evolution of etching morphology of SF6 / O2 under a flow rate of 70 / 10sccm and a power of 100W. The scale bar is 1μm.

[0022] Figure 6 Nanostructures etched in a mixed atmosphere of SF6 and O2. Among them, a) - f) used different etching times of 50×4s, 50×5s, 50×6s, 50×7s, 50×8s, and 50×9s respectively. The scale bar is 1μm.

[0023] Figure 7 For the dependence of structural evolution on the sizes of nanosphere and spacer. The height and width of all the markings are for the silicon pillar part below. a) 300nm nanosphere and 100nm spacer, b) 300nm nanosphere and 300nm spacer, c) 300nm nanosphere and 500nm spacer, d) 500nm nanosphere and 100nm spacer, e) 500nm nanosphere and 300nm spacer. The scale bar is 1μm.

[0024] Figure 8 For the morphologies of cyclic etching a) 14 times and b) 16 times under 300nm spacer and nanosphere. The scale bar is 1μm.

[0025] Figure 9 For the evolution law of the ST-NSL of the present invention.

[0026] Figure 10 For the anti-reflection, light trapping, and SERS applications of several array structures. a - c) are respectively the nano pillar@reentrant, nano mushroom, and nano needle arrays fabricated under 100nm spacer and 500nm nanosphere, a1 - c1) are the structural parameters of a - c), d) is the anti-reflection performance of the structures of a - c) and the blank sample, the yellow dashed line represents 10% anti-reflection rate, e1 - e3) are the electric field distributions of a - c) under the incident light of 680nm wavelength, f) is the morphology of the synthesized nanorods, g) is the distribution morphology of the mixture of gold nanorods and TPhT enriched on the FOTS-modified nano mushroom array, h) is the water contact angle of the FOTS-modified nano mushroom array, i) is the schematic diagram of SERS detection, j) 10 -2 M to 10 -10 The SERS spectra of TPhT with concentrations from 10

[0027] Figure 11Morphological property analysis of gold nanorods. Among them, a) SEM image of gold nanorods, b) UV-Vis spectrum of gold nanorods, c) length distribution of gold nanorods, d) diameter distribution of gold nanorods. The scale bar is 1μm. Detailed implementation mode

[0028] The technical solution of the present invention will be further elaborated below in conjunction with embodiments. The following preparation methods are only used to illustrate the present invention, rather than limiting the scope of the present invention. Unless otherwise specified, the following raw materials can be purchased on the market or obtained by conventional preparation means. The preparation methods and testing methods used in the following embodiments are all conventional existing methods.

[0029] I. Preparation of ST-NSL array structure

[0030] Take 100 μL of SiO2 dispersion with different SiO2 particle sizes at a concentration of 2.5% wt, wash it 3 times with deionized water and ethanol, then centrifuge and precipitate the SiO2 and redisperse it in 150 μL of ethanol for interfacial assembly. During interfacial assembly, the SiO2 dispersion is dropped onto a hydrophilically treated glass slide immersed in water. The SiO2 interfacial self-assembled film will immediately form at the water-air interface. Among them, the 500-nm SiO2 film is blue, and the 300-nm SiO2 film is purple. Then, the assembled nanosphere film is transferred to a silicon wafer with a corresponding spacer by the horizontal lifting method as the nanosphere layer. The material of the spacer is the same as that of the self-assembled film, which is also SiO2.

[0031] Patterned nanoarray structures are prepared by RIE etching under different conditions. RIE etching can be carried out under different conditions to obtain different evolution paths and different array structure results. All silicon wafers can be ultrasonically treated for 15 min after etching to ensure the removal of surface impurities and residual templates.

[0032] In subsequent experiments, the influence of the above optimization conditions on the multi-pattern evolution process will be further discussed in detail.

[0033] II. General evolution mechanism

[0034] The preparation of ST-NSL multi-patterned nanoarrays is mainly obtained by reactive ion etching of silicon wafers with a certain thickness of spacer coated with self-assembled nanospheres on the surface. Among them, the nanosphere and the spacer together serve as the pattern define layer. The specific evolution process is as follows Figure 1-2As shown, the ST-NSL multiple pattern evolution generally follows the order of nano plate, nano mushroom, nano pillar, and nano needle. During the etching process, the radial size of the nanosphere continuously decreases. The spacer is etched into different patterns during the dynamic masking process and constitutes the upper part of the nanoarray structure. This process combines anisotropic and isotropic etching to form nano pillar and nano cone structures in the silicon wafer under the spacer. The isotropic etching of the spacer and the nanosphere and the dynamic masking define the pattern of the final structure.

[0035] During the etching process, the substrate is completely covered by the spacer and the nanosphere at the initial stage. Due to their homogeneity, relatively isotropic etching occurs, namely the dynamic mask process. When the plasma of the RIE process penetrates the spacer, the magnetic enhancement effect and the rapid etching of the etching gas on silicon form different-shaped supports below. During the dynamic masking process, as the nanosphere continuously decreases, the projected area of the nanosphere on the spacer surface also decreases, which results in a longer etching time for the periphery of the spacer-formed structure compared to the inside, making its thickness thinner than that of the inside. A trapezoidal shape can be observed immediately from the cross-section (as shown in Figure 2 b). When this process continues, due to the further decrease of the nanosphere, a fan-shaped cross-section is formed (as shown in Figure 2 c). Until the nanosphere is completely etched, the spacer forms a conical structure (as shown in Figure 2 d). In addition, due to their homogeneity, after the etching progresses to a certain stage, the remaining part of the nanosphere adheres to the spacer, which is also the mechanism for the formation of the upper cap of the nano mushroom.

[0036] Observing the evolution of the entire system structure, when the RIE process just penetrates the spacer, the nanosphere is removed by ultrasound, and a closely packed nano plate array structure is formed on the silicon wafer, as shown in Figure 2e. When continuous etching is carried out, the plasma penetrates the spacer and etches into the silicon wafer itself. Due to the certain aspect ratio of the etching process, the evolution process of the etched part of the underlying silicon wafer evolves from nano pillar to nano cone and then to nano needle. The etching conditions used in this process have a high selectivity between silicon and silicon dioxide, where the etching rate of silicon is greater than that of silicon dioxide. Therefore, after the nanoplate is formed, the nano plate structure is eroded by the etching gas, and at the same time, the underlying silicon wafer forms a nano pillar structure. The two assembled together form a nano mushroom structure, as Figure 2 f. When the substrate is continuously etched, since the nanosphere has been completely eroded at this time, the remaining part of the spacer is also eroded to a certain extent. And because the etching rate of silicon is higher than that of the spacer, the connecting part between the spacer and silicon breaks due to the shear force during ultrasonic treatment. Thus, a frustum-shaped array of nano trapezoid, which is a kind of nano pillar structure, is formed, as Figure 2 shown in g. When the substrate is continuously etched, the lateral dimension of the nano trapezoid (nano pillar) structure under the spacer is further reduced. Until the size of its upper surface is 0, the spacer and silicon break naturally. After removing impurities by ultrasonic treatment, a nanoneedle structure is finally formed, as Figure 2 shown in h. Since the cap formed by the spacer masks the frustum structure below, only the part of the structure below the cap undergoes isotropic etching in the lateral direction during etching. This process is the key to forming a nano needle array structure with sharp tips. At the same time, due to the masking effect of the cap, the exposed part of the nano needle grows further under the action of the plasma, greatly increasing the aspect ratio of the nano needle structure.

[0037] In short, the mechanism of ST-NSL is the combination of anisotropic and isotropic etching, achieving a dynamic masking process by sacrificing the nanosphere and spacer, thereby realizing the one-step etching evolution of various patterns. The final morphology of all patterns mainly depends on the etching atmosphere, etching process parameters, and the relative and absolute sizes of the nanosphere and spacer. As a further practical demonstration of this technology, we fabricated a series of patterned arrays on silicon wafers with different thickness spacers using SiO2 nanospheres of different sizes to verify the multi-patterning ability of ST-NSL and its performance in structure adjustment.

[0038] III. Pattern Evolution under Cyclic Etching and Non-Cyclic Etching

[0039] Cyclic etching is usually used to improve the aspect ratio of structures in micro-nano processing. Since the change in etching selectivity in the ST-NSL technology has a significant impact on its final structure, cyclic etching and non-cyclic etching are of great significance for the relative rates of isotropic and anisotropic etching, as well as the regulation of the final morphology. To demonstrate the difference between cyclic etching and non-cyclic etching, here we used 500-nm-sized SiO2 nanospheres and carried out on a 300-nm SiO2 spacer, and prepared multi-patterned nanoarrays through cyclic etching and non-cyclic etching processes to study the influence of the etching process on the structure.

[0040] In the preliminary preparation of the research of the present invention, we etched the silicon wafer with a nanosphere mask without a spacer, and initially prepared nano-cone and nano-pillar arrays in these studies. Here, we compared the differences between the ST-NSL technology and the traditional NSL technology by using the same etching atmosphere. Using the same atmosphere conditions (SF6 / O2) as in the previous studies, first etch the substrate to form a nano mushroom structure. The etching conditions are set as follows: the SF6 flow rate is 70 sccm, the O2 flow rate is 10 sccm, the power is set to 100 W, and the relative position of the RF power is set to 100%, and the etching is carried out under the condition of magnetic enhancement. After etching the substrate for 250 s, remove the nanosphere mask on the surface by ultrasonic treatment, and the formed nano mushroom array structure is as Figure 3 shown in e1. It can be observed that the upper part of the nano mushroom structure has a cap with a hat shape, that is, a cap with a fan-shaped cross-section, and its material is SiO2. The lower part of the silicon wafer of the nano mushroom structure is a frustum of a cone with a trapezoidal cross-section or a nano pillar structure with a relatively low aspect ratio. According to the previous analysis, the formation of the cap is due to the full etching of the nanosphere, which is further etched after the spacer is etched to form a trapezoidal cross-section. And since this process is a non-cyclic etching process, the inclined surface angle of the frustum structure at the bottom is relatively low, and the angle with the silicon plane is about 75° (calculated by Image J).

[0041] After the formation of the nano mushroom structure, we studied the differences between different etching processes through cyclic etching and non-cyclic etching. Here, the nano mushroom structure was first etched to highlight the impact of subsequent etching processes on the structure. The total etching time for cyclic etching and non-cyclic etching was controlled to be the same. The single etching time for cyclic etching was 50 s, and the interval between etching cycles was 10 s to ensure the full release of the etching products. Magnetic enhancement was applied during all etching processes.

[0042] The fundamental difference between cyclic etching and non-cyclic etching is that in non-cyclic etching, the etching products cannot be released from the structure, while the release of the etching products leads to an increase in the aspect ratio of cyclic etching. The structures formed by cyclic etching and non-cyclic etching are shown as Figure 3 follows. The conditions for cyclic etching are Figure 3 in Fig. 3b, a 50-s etching was carried out after 250 s of non-cyclic etching, and in Fig. 3c, 2 cycles of 50-s cyclic etching were carried out after non-cyclic etching. Figure 3 In Fig. 3d, 3 cycles of cyclic etching were carried out after 250 s of non-cyclic etching, and their total etching times were 300 s, 350 s, and 400 s in sequence. Therefore, for the non-cyclic etching structure, we etched the bare substrate separately for a single time with total durations of 300 s, 350 s, and 400 s respectively.

[0043] Figure 3 In Fig. 3b, etching the substrate for 50 s after 250 s of etching further reduced the sizes of the nanospheres and spacers. At the same time, the nanospheres and spacers adhered to each other due to their homogeneity during this process, thus forming a double-layer cap structure on the silicon substrate. Combining with the further etched silicon column structure formed a nano tower array. Meanwhile, by comparing the silicon array in the lower layer with the structure of the lower layer of the nano mushroom under the 250-s etching condition, it can be clearly observed that the aspect ratio of this array structure increased, and the angle between the side of the lower-layer nano pillar structure and the silicon plane was close to 81° (calculated by Image J). Thus, it can be seen that cyclic etching and non-cyclic etching have a significant impact on the aspect ratio and morphology parameters of the structure, and the morphology of the array structure can be regulated by adjusting the etching conditions.

[0044] In Figure 3In c, after 250 s of non-cyclic etching and two cycles of 50 s etching, a nano tower array with a three-layer cap structure was formed on the substrate. The residue of the nanosphere and the spacer fused together. The first layer of the cap was the etching product of the nanosphere, the second layer of the cap was the etching product of the further reduced spacer, and the third layer of the cap was due to the reduction of the upper nanosphere and spacer, making its radius smaller than the maximum radius of the lower nano pillar. Therefore, on the lower nano pillar, the part with a size smaller than the spacer and the nanosphere evolved differently from the larger part below. The part with a size smaller than the spacer and the nanosphere formed the third layer of the cap, and its etching mechanism was similar to the formation of the cap in the previous process. It was because the part larger than the spacer and the nanosphere evolved independently to form the nano pillar structure. The upper part of it was only reduced under isotropic etching, and the exposed part was rapidly reduced under the action of magnetically enhanced plasma, eventually resulting in a smaller size compared to the upper part and finally forming the third layer of the cap structure. In Figure 3 In d, the substrate was further etched. Due to the isotropic etching effect, the final size of the upper part of the nanopillar was reduced to 0, causing the upper cap structure to detach from the substrate surface and then evolve into a nanoneedle array structure. The mechanism of this evolution was previously described in Figure 2 h. The cap on the pillar protected the nanowire from etching, and the nanowire was reduced to a sharp needle under isotropic etching.

[0045] When performing non-cyclic etching, when the etching time was extended to 300 s, due to the isotropic etching and the reduction of selectivity caused by the masking of the etching product when it could not be released from the structure, the isotropic etching rapidly reduced the upper surface of the lower nano pillar, and finally a nano cone array structure was formed (as shown in Figure 3 f and 3f1). The angle between its inclined plane and the silicon plane was approximately 65° (calculated by Image J). Compared with the cyclic etching at the same time, this angle was approximately 16° smaller, thus fully demonstrating the ability of non-cyclic etching and cyclic etching to adjust the relative speed of isotropic etching and anisotropic etching. When the non-cyclic etching time was 350 s, the contact area between the frustum structure above and below the substrate and the upper spacer decreased significantly. Figure 3The conical tip structure in f1 detaches from the structure surface during ultrasonic treatment. Thus, the surface of the final structure is planar. The structure below it is etched into an inclined plane with a certain curvature during etching due to the masking effect of the upper conical cap, forming a nano - pillar structure with an angle relative to the silicon plane that is somewhat increased compared to the nano - cone, as Figure 3 g and Figure 3 g1. Compared with the cyclic etching at the same time, due to the enhanced selectivity of the cyclic process, isotropic etching is inhibited, and the cap finally remains on the structure. When the time of non - cyclic etching is further extended, compared with Figure 3 g and Figure 3 g1, the size of the structure below it in the horizontal direction is further reduced. Finally, a sharp shape is formed on its upper surface, and the upper cap detaches from the structure. Thus, a nano - needle array structure identical to that of cyclic etching is finally formed, as Figure 3 h and Figure 3 h1 shown. However, due to the different selectivities of cyclic etching and non - cyclic etching, it can be seen that Figure 3 d1 and Figure 3 h1 have different aspect ratios and sharpness of the two nano - needle structures. Thus, it is further proved that under non - cyclic and cyclic etching conditions, the etching process variation has the ability to regulate its final array structure.

[0046] IV. Pattern Evolution under Different Selectivity Ratios

[0047] Under the same etching conditions, when the etching process is adjusted, its final structure can be highly regulated. At the same time, when the etching conditions are changed, such as adjusting the etching atmosphere, etching power, etc., it can also be expected that there will be a certain regulatory effect on the final structure of the etching. This is of great significance for fabricating patterned array structures with specific parameters such as aspect ratio, sharpness, etc. on demand. Therefore, in order to evaluate the influence of different conditions on its final morphology and structural parameters, we selected three different atmosphere conditions and two different etching powers for comparison, and prepared all structures under the cyclic etching process.

[0048] As Figure 5 shown, this figure shows the etching products under the atmosphere conditions of CHF3 and SF6 / O2. For another atmosphere condition CHF3 / O2, as Figure 4As shown, the etch products are shown under CHF3 and O2 atmosphere conditions with flow rates of 40 sccm and 15 sccm respectively, etch times of 50×8 s, 50×10 s, 50×12 s, 50×14 s, and a power of 200 W. Due to selectivity reasons, an array pattern cannot be formed on the underlying silicon. Under magnetic enhancement, the morphology of all structures etched under CHF3 / O2 is a similar circular mesa-like rough surface morphology. This result also demonstrates the importance of the etch atmosphere for the final array morphology. Therefore, in Figure 5 we investigated the dependence of morphology on different atmospheres, flow rates, and etch powers under CHF3 and SF6 / O2 atmosphere conditions. Since the same nanospheres and spacers were used, all structures have the same periodicity.

[0049] By comparing the patterns etched at 200 W under CHF3 and SF6 / O2 atmosphere conditions respectively, the aspect ratio of the nano mushroom etched under the CHF3 atmosphere condition is higher than that of the pattern under the SF6 / O2 mixed atmosphere condition. However, as Figure 5 a4 and Figure 5 b4 show, the two patterns have similar heights. The nano mushroom under the SF6 / O2 etch atmosphere obviously has larger dimensions at the top and bottom cross-sections, and the crown cap at the top is larger than the pattern etched under the CHF3 atmosphere condition at any scale. When further etched, its aspect ratio can be further increased. When the etch time is extended to 50 s and 8 cycles, the aspect ratios of the nanoneedle arrays etched under CHF3 and SF6 / O2 atmosphere conditions are also very different, as Figure 5 a5 and Figure 5 b5 show. Among them, the nanoneedle array has a higher aspect ratio under the SF6 / O2 mixed atmosphere condition than under CHF3. Its detailed structural parameters are marked in the figure after measurement by Image J. The nano needle formed under the CHF3 atmosphere environment has a lower height and a larger bottom size, but the sharpness of its tip is higher than that of the nano needle formed under the SF6 / O2 atmosphere condition, which is attributed to the higher isotropic etching rate under the CHF3 atmosphere environment.

[0050] Further extend the etch time and compare the patterns etched for a longer time under the two atmosphere conditions, such as Figure 5 a6 and Figure 5As shown in b6. The nano needles formed in the CHF3 atmosphere are more like nano cone structures. Since the SF6 / O2 atmosphere conditions have a higher selectivity and anisotropic etching rate, their structures still maintain a nano needle structure with a relatively high aspect ratio, and the aspect ratio is about 3. Here, we can easily find that the selectivity, anisotropy, and relative rates of isotropy of the etching conditions for nanosphere, spacer, and wafer have a significant impact on the final structure. The aspect ratio changes and relative sizes of the two structures further confirm that the pattern formed under SF6 / O2 atmosphere conditions has a higher aspect ratio. It is worth mentioning that the total flow rates of the two atmosphere conditions of CHF3 and SF6 / O2 are the same, and their nano needle arrays are also formed under the conditions of etching for 50 s and 6 cycles. Therefore, by controlling the total flow rate of the etching gas, it is easy to change different atmospheres and regulate the morphology of their patterns.

[0051] To clarify the influence of power and flow rate on the final structure, SF6 / O2 atmosphere conditions with flow rates of 35 sccm and 5 sccm, power settings of 100 W and 200 W, flow rates of 70 sccm and 10 sccm, and power settings of 100 W were used for etching. The comparison between 100 W and 200 W power at 35 sccm SF6 and 5 sccm O2 is as Figure 5 b and Figure 5 c shown. When etching at 200 W, the etching rate is much higher than that at 100 W. Therefore, for a similar nano mushroom structure, it takes 50 s of etching and 6 cycles to etch at 200 W, while it takes 50 s of etching and 10 cycles to etch at 100 W. In addition to the difference in etching time, the aspect ratios of the final patterns at different powers are also different. In Figure 5 b4 - 6 and Figure 5It can be clearly seen from c4 - 6 that the etched pattern under a 100W power supply has a higher aspect ratio. One reason might be that the etched pattern at 100W power has experienced 9 releases of etching products, while there are only 4 releases during etching at 200W power. The release of etching products helps to increase the aspect ratio of the structure, thus having a higher selectivity between the substrate and the sidewall. A higher aspect ratio also means a deeper final pattern height and better anti - reflectivity. A sharper nano - needle array also contributes to enhanced localization of the electric field, which is crucial for surface plasmon and biomedical applications. Finally, we can conclude that in an atmosphere of 35sccm SF6 and 5sccm O2, when the power is set to 100W, the fabricated nano - structure array is easier to control the morphology, is more friendly to applications, and its surface roughness is also lower than that of the pattern etched at 200W, as shown in the SEM pictures.

[0052] In addition, compared with the structure etched under a flow rate of 70sccm SF6 and 10sccm O2, its etching rate is still lower. Under the flow rate of 70sccm SF6 and 10sccm O2, the difference from the condition of 35sccm SF6 and 5sccm O2 is similar to the difference between etching at 200W power and 100W power under the same flow rate and atmosphere conditions, as Figure 5 shown in d. After increasing the etching flow rate while keeping the etching power unchanged, the aspect ratio of the structure decreases, and its parameters are as Figure 5 shown in d4 - d6.

[0053] In addition, we characterized the pattern etched at 200W power under the atmosphere condition of 70sccm SF6 and 10sccm O2, as Figure 6 shown. As mentioned above, higher etching power and higher flow rate both reduce the etching selectivity and the aspect ratio of the etching products. In addition, after increasing the etching power, we found that the surface roughness of the structure also increased significantly.

[0054] Among them Figure 6 in a, the nano - mushroom structure only has a very short nano - pillar at the bottom, and its overall structure is more like a nano - cone structure with a curved surface. The morphologies of other etched patterns have also changed greatly. When the nano - mushroom is further etched, the obvious difference in size between the cap and the underlying pillar seen in the previous conditions is not observed. The outer diameter of the cap has a similar size to the upper surface of the adjacent nano - pillar, as Figure 6 shown in b and 6c. When the substrate is further etched, the nano - needle array can still be formed ( Figure 6d - f), which has a significantly higher roughness than the aforementioned conditions and lower uniformity in the distribution between structural units after deep etching, such as Figure 6 e - f. Therefore, changing different etching atmospheres and powers can have a significant impact on its structure. However, in order to maintain a high aspect ratio, the uniformity of the structure and its low surface roughness, in subsequent studies, we all used the etching conditions of a mixed gas of 35 sccm SF6 and 5 sccm O2 at a power of 100 W, which has higher selectivity and is easy to control the morphology.

[0055] V. Pattern Evolution of Different Nanospheres and Interlayer Sizes

[0056] In addition to the influence of etching conditions, the sizes of nanosphere and spacer play an important role in the periodic conditions and morphology control of the final pattern. And due to its ability to control the size, it is the main influencing condition. To clarify its regulation and influence on the final structure, we selected nanospheres and spacers with diameters of 100 nm, 300 nm, and 500 nm to evaluate their influence on the final pattern under the same etching conditions. All structures were etched in a 50 s cycle with a mixed gas of 35 sccm SF6 and 5 sccm O2 and a power of 100 W.

[0057] Figure 7 shows the structural dependence of the nanoarray on the sizes of nanosphere and spacer. In Figure 7 a - c, the diameter of the nanosphere is 300 nm, and the thicknesses of the spacer are 100 nm, 300 nm, and 500 nm. Comparing the nanomushroom structures formed by etching the 100 nm spacer for 6 cycles, the 300 nm spacer for 8 cycles, and the 500 nm spacer for 12 cycles, due to the different times for the plasma to penetrate the spacer at different spacer thicknesses, patterns with different aspect ratios and significantly different morphologies were finally formed. When the spacer is 100 nm, the plasma easily penetrates the spacer, thus easily forming a mushroom-like structure. When the spacer thickness increases to 300 nm, its size is comparable to that of the nanosphere, and due to the longer time for the plasma to penetrate the spacer, the relative diameters of the cap and the underlying pillar are smaller compared to the pattern of the 100 nm spacer. For the etching of the 500 nm spacer, the etching in the initial stage shapes the structure into a trapezoidal frustum structure. At this time, the nanospheres on the surface have been completely eliminated due to their small size. Then, after etching for 10 cycles, a structure such as Figure 7The nano plate structure shown in c1. This is because the size of the spacer is larger than that of the nanosphere, and the etching does not penetrate the spacer, so a secondary structure cannot be formed beneath it. Therefore, when the spacer is thinner compared to the nanosphere, the etching process is more likely to penetrate the spacer and form a secondary structure on the wafer. However, even when the size of the spacer has exceeded that of the nanosphere, when further etching is carried out, the plasma can still penetrate the spacer and evolve into nano mushroom, nano pillar, and nano needle arrays, only with different aspect ratios, as Figure 7 shown in c2 and Figure 7 c3.

[0058] Comparing the nano needle arrays formed under three different conditions, the nano needle array formed with a 100nm spacer and 300nm nanosphere has a sharper top morphology, and the specific parameters are as Figure 7 shown in a3. As the thickness of the spacer increases, the nano needle array formed with a 300nm spacer is shorter than the etching product of the 100nm spacer, and its sharpness also decreases. This structural morphology is more like the nano pencil structure reported in the literature. The reason for this result is that the thicker spacer slows down the penetration process, thereby reducing its aspect ratio, and because the radial size of the spacer decreases more, this structure is finally formed at the top, as Figure 7 shown in b3. Although its sharpness can be improved by further etching, our results show that when further etching is carried out for 2 cycles (conditions same as Figure 7 b), the tip part is cut off under the action of ultrasound, as Figure 8 shown in a, Figure 8 and b further shows the morphology after another 2 cycles of etching. The cut nano pillar structure is further etched and sharpened, but due to the influence of the mask, most of the structures are inclined, and there is no obvious pattern in the way they are inclined, and the centers of each unit are randomly distributed.

[0059] The structure with a 500nm spacer finally also evolves into a randomly distributed nano pillar array, as Figure 7as shown in c3. The potential mechanism for this result is that the cap part of the nano mushroom formed under the 300nm nanosphere and 500nm spacer is completely composed of the spacer. When the nanosphere mask is completely etched away, it cannot mask the underlying etching during the subsequent etching process. Therefore, the periphery of the cap above the nano mushroom it forms is thinner and has a conical shape as shown in Figure 7 c2. At the same time, due to the relatively thick longitudinal dimension of the cap, the etching of the underlying silicon is faster than that of the upper cap during the formation of the nano pillar. And due to the masking effect of the cap, the etching of the entire pillar tends to be isotropic etching. Therefore, when the cap can be removed from the surface, a nano pillar array is formed below, and the overall radial dimension of this array is relatively uniform without the formation of sharp tops. The pattern fabricated with the 300nm nanosphere demonstrates the importance of the relative dimensions between the nanosphere and the spacer for optimizing the structure and the ability of the Nanosphere to regulate the period. We further studied the structure with the 500nm nanosphere as the mask, controlling the spacer thickness to be 100nm, 300nm, and 500nm respectively to further prove the multi-patterning fabrication ability of the ST-NSL technology. Figure 7 d~e show the structures fabricated with 100nm and 300nm spacers. The etching of the 100nm-thick spacer under the 500nm nanosphere mask has a large difference from that between the 100nm spacer and 300nm nanosphere system, although their relative dimensions are relatively close. As shown in Figure 7 d1, the structure in this system evolves into a nano pillar@reentrant structure at the initial stage and then continues to form a nano mushroom and a nano pillar. The nano pillar@reentrant structure can enhance the hydrophobicity of the structure surface. Compared with the nano mushroom fabricated with the 300nm spacer and 500nm nanosphere ( Figure 7 e1), the nano mushroom array in this system has thicker pillars, as shown in Figure 7 d2. When both are further etched for 2 cycles, Figure 7 the nano mushroom in d2 evolves into a nano pillar array with a small cap at the top, and its diameter is equal to the underlying column structure, as shown in Figure 7 d3. While Figure 7The nano mushrooms in e1 evolve into a nano cone array( Figure 7 e2). This structure is due to the fact that under the etching conditions, the upper surface size of the pillars under the nano mushrooms is relatively small. During further etching, ultrasonic treatment causes the upper cap to separate from the pillars, thus forming a nano cone array. When further etching the nano cones, a nano needle array is formed. And due to the relatively high isotropic etching rate under these conditions, the nano needle array has a very sharp structure.

[0060] VI. Summary of the Graphic Evolution Law and Etching Condition Optimization of ST - NSL

[0061] Combined with the above experimental analysis results, as the optimization conditions for multi - graphic evolution, in the specific RIE etching process of silicon wafers:

[0062] The ratio of the particle size of the nanospheres in the nanosphere layer to the thickness of the spacer layer can be 5:1 - 3:5, preferably 3:1 - 3:5; a more suitable thickness ratio can be coordinated with an appropriate mask reduction rate to optimize the aspect ratio of the graphic structure and the number of graphic evolution structure forms. Specifically, the particle size of the nanospheres in the nanosphere layer can be 100nm - 600nm, further preferably 300nm - 500nm, and the thickness of the spacer layer can be 100nm - 600nm, further preferably 100nm - 300nm.

[0063] The etching atmosphere can be selected as CHF3, SF6 / O2 mixed atmosphere, with an atmosphere flow rate of 40sccm - 80sccm. The flow ratio of SF6 / O2 in the SF6 / O2 mixed atmosphere is preferably (7 ± 1):1. A suitable atmosphere composition is beneficial to improving the number of graphic evolution structure forms and the roughness.

[0064] The etching rate parameters can be an etching time of 50s - 700s at a power of 100W - 200W; lower etching power and lower atmosphere flow rate are beneficial to improving the aspect ratio and roughness of the graphics, and are more conducive to morphology control and friendly applications. Cyclic etching or non - cyclic etching can also be used. Cyclic etching includes at least 1 cycle process with an etching duration of (50s ± 20s) per cycle and an interval duration of (10s ± 5s) per cycle during the entire etching process. Preferably, the entire etching process uses a cyclic process with an etching duration of (50s ± 20s) per cycle and an interval duration of (10s ± 5s) per cycle. Cyclic etching can not only increase the aspect ratio of the material but also further expand the number of graphic evolution structure forms. The overall evolution law of the process of the present invention can be summarized as Figure 9Under general conditions, the spacer and nanosphere can bring about four sequential evolution stages of nano plate, nano mushroom, nano pillar, and nano needle. Through further optimization of conditions, under certain specific etching conditions, other morphologies such as nano pillar@reentrant, nano tower, nanocone, and nano pencil will also appear during the evolution process, making the graphic morphologies obtainable by the present invention more diverse. For the sake of understanding, the understanding of each morphology during the graphic evolution process in the present invention is as follows:

[0065] nano plate: The silicon structure is not etched, and there is a mask (SiO2) on the silicon structure with a substantially planar upper surface (for example, a trapezoidal cross-section in the longitudinal section).

[0066] nano pillar@reentrant: Below is a nano pillar silicon structure and above is a mask (SiO2) with a substantially planar upper surface (for example, a trapezoidal cross-section in the longitudinal section).

[0067] nano mushroom: Below is a nano pillar silicon structure, and above is a cap-shaped mask (SiO2) with a fan-shaped cross-section.

[0068] nano tower: Below is a nano pillar silicon structure, and above is a cap-shaped mask (SiO2) with at least two layers of fan-shaped cross-sections.

[0069] nano pillar: A silicon structure with a trapezoidal cross-section or a cross-section similar to a trapezoid. A cross-section similar to a trapezoid means that the upper surface is not a horizontal straight line in the cross-section, may be an arc, but does not have a tip.

[0070] nano cone: A silicon structure or mask (SiO2) with a triangular cross-section in the longitudinal section (the solid is in the shape of a triangular pyramid).

[0071] nano pencil: A special nano pillar structure with a high aspect ratio, a silicon structure with a cross-section similar to a trapezoid in the longitudinal section, and an upwardly convex arc on the upper surface in the cross-section.

[0072] nano needle: A silicon structure with a stepwise changing diameter size from bottom to top in the longitudinal section and a sharp tip at the top of the longitudinal section.

[0073] VII. Anti-reflection, superhydrophobic, and SERS applications of the substrate

[0074] To evaluate the practical application performance of the array structure prepared by the ST-NSL technology, we selected several structures as examples for antireflective surface applications. Antireflective surfaces have extensive applications in solar cells, water collection, and other disciplines. According to previous studies, structures with higher aspect ratios tend to have better antireflective properties. Therefore, structures fabricated under 100nm spacer and 500nm nanosphere masks were selected. The specific structures are as shown in Figure 10 a - c. These structures are nano pillar@reentrant, nano mushroom, and nano needle arrays respectively. The specific structural parameters are as shown in Figure 10 a1 - c1. All antireflective performance measurements were carried out using a Lambda HR950 UV-Vis system in a 150mm integrating sphere.

[0075] By performing FDTD simulations on the electric field distribution characteristics of the three structures, the results are as shown in Figure 10 e1 - 10e3. The pictures show the electric field distribution of the three structures under the same incident wavelength of 680nm. It can be seen from the figure that the electric field distribution in the array structure unit is significantly enhanced, which is also consistent with the results of the antireflective measurements. Therefore, these structures are all helpful for light trapping, that is, the light trapping effect, which is crucial for the construction of surface plasmon structures and SERS applications. The light trapping effect helps to generate the localized surface plasmon effect. Here, we selected the nano mushroom structure as the substrate for its SERS application. Since the top of the nano mushroom structure is a cap structure made of SiO2, which contains a large number of hydroxyl groups that can react with FOTS. Thus, it greatly improves the surface hydrophobicity, achieving a similar effect to the nano pillar@reentrant structure. At the same time, the nano mushroom structure has more excellent light trapping characteristics. Although the nano needle array has a stronger electric field on the surface and inside of the structure, as shown in Figure 10 e3. But it is difficult for nano needles to introduce a large number of noble metal hot spots inside the structure, which is the basis of the high plasmon resonance effect. And compared with the nano mushroom and nano pillar@reentrant structures, nano needles cannot endow it with stable superhydrophobic properties. And by enriching droplets containing noble metal nanoparticles through hydrophobic interaction, a stronger surface plasmon effect can be generated, thus greatly improving the sensitivity of SERS detection.

[0076] Therefore, by introducing the hydrophobic enrichment effect and light-trapping characteristics, the nano mushroom structure is utilized for SERS applications. This system is based on the plasmonic effect of GNRs, using the nano mushroom structure as an enrichment platform and a light-trapping enhancement platform for the mixture of GNRs and analytes, for SERS detection. The nano mushroom structure is modified with FOTS to enhance its hydrophobicity, and the FOTS modification is carried out according to the steps reported in the literature. The modified water contact angle is calculated as 136° after averaging three measurements, as Figure 10 shown in h. Among them, the GNRs used in SERS detection are about 39.78 nm long and about 11.68 nm in diameter, as Figure 10 shown in f, and its molar concentration is calculated to be about 1 nM. The size statistics of GNRs are obtained by averaging 100 GNRs with Image J, and its specific distribution is as Figure 11 shown. Figure 11 b is the UV-visible spectrum of GNRs, and its peak position is 767 nm, which is close to the detection wavelength, facilitating the surface plasmon resonance effect. Before use, GNRs are concentrated to 5 nM and dispersed in 1 mM CTAB. The analysis substrate is selected as TPhT (triphenyltin chloride), which is an important environmental pollutant because of its persistent pollution in the environment and its ability to interfere with the human endocrine system.

[0077] During the detection process, equal amounts of TPhT with a concentration gradient distribution from 10 -2 M to 10 -10 M and GNRs are mixed and adsorbed for 30 min, and then 5 μL of the mixed solution is dropped onto the FOTS-modified nano mushroom array at 35 °C until it completely evaporates. Due to the surface hydrophobicity, GNRs are enriched on a smaller coffee ring and surround the nano mushroom units, as Figure 10 shown in g. More importantly, due to the hydrophobic enrichment effect and the guidance of the evaporation process, GNRs are arranged orderly around the nano mushroom structure. Due to its orderly arrangement, the uniformity of the nanogap between GNRs is also improved, which helps to form consistent hot spots between GNRs. Then, SERS detection is carried out on the GNRs on the coffee ring, and the detection conditions are carried out under a 785 nm light source with a 10 s exposure time, 0.1% laser intensity, and 1 integration mode. The results are as Figure 10 shown in j. The detection limit of TPhT reaches 10 -10 M, which is the lowest detection limit reported in the current literature. This result proves the feasibility of the ST-NSL technology in SERS detection and the application ability of this structure.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A multi-patterning nanosphere lithography method with an embedded layer trigger, using a sequentially arranged spacer layer and nanosphere layer as masks, where the spacer layer and the nanosphere layer have the same material; The multi-patterning at least includes four sequential evolution stages of nano plate, nano mushroom, nano pillar, and nano needle; Among them, For nano plate, the silicon structure is not etched, and there is a mask on the silicon structure with a substantially flat upper surface; For nano mushroom, there is a nano pillar silicon structure below and a mask in the shape of a hat with a fan-shaped cross-section above; For nano pillar, the longitudinal cross-section is a trapezoidal cross-section or a similar trapezoidal cross-section. A similar trapezoidal cross-section means that the upper surface is not a horizontal straight line in the cross-section but an arc and does not have a tip; For nano needle, the longitudinal cross-section has a stepwise changing diameter from bottom to top, and the silicon structure has a sharp tip at the top of the longitudinal cross-section.

2. The multi-patterned nanosphere lithography method with in-layer triggering according to claim 1, wherein The ratio of the particle size of the nanospheres in the nanosphere layer to the thickness of the spacer layer is 5:1 to 3:

5.

3. The multi-patterned nanosphere lithography method with inlay trigger according to claim 1, characterized in that The ratio of the particle size of the nanospheres in the nanosphere layer to the thickness of the spacer layer is 3:1 to 3:

5.

4. The multi-patterned nanosphere lithography method with inlay trigger according to claim 1, characterized in that, The particle size of the nanospheres in the nanosphere layer is 100 nm - 600 nm.

5. The multi-patterned nanosphere lithography method with in-layer triggering according to claim 1, wherein The particle size of the nanospheres in the nanosphere layer is 300 nm - 500 nm.

6. The multi-patterned nanosphere lithography method with an embedded trigger according to claim 1, wherein The thickness of the spacer layer is 100 nm - 600 nm.

7. The multi-patterned nanosphere lithography method with inlay trigger according to claim 1, wherein The thickness of the spacer layer is 100 nm - 300 nm.

8. The multi-patterned nanosphere lithography method with embedded layer triggering according to claim 1, characterized in that, Using the RIE etching method, the etching atmosphere is a CHF3, SF6 / O2 mixed atmosphere, the atmosphere flow rate is 40 sccm - 80 sccm, and the etching rate parameter is an etching time of 50 s - 700 s at a power of 100 W - 200 W.

9. The multi-patterned nanosphere lithography method with inlay trigger according to claim 8, characterized in that, In the SF6 / O2 mixed atmosphere, the SF6 / O2 flow ratio is (7 ± 1):

1.

10. The multi-patterned nanosphere lithography method with interlayer triggering according to claim 8, wherein Using cyclic etching or non-cyclic etching. Cyclic etching includes at least 1 cycle process in the whole etching process with an etching duration of (50 s ± 20 s) per cycle and an interval duration of (10 s ± 5 s) per cycle.

11. The multi-patterned nanosphere lithography method with inlay trigger according to claim 10, characterized in that, Cyclic etching is a cyclic process in the whole etching process with an etching duration of (50 s ± 20 s) per cycle and an interval duration of (10 s ± 5 s) per cycle.

12. The multi-patterned nanosphere lithography method with an embedded trigger according to claim 1, characterized in that The materials of the spacer layer and the nanosphere layer are SiO2, and the substrate is silicon.

13. The multi-patterned nanosphere lithography method with inlay trigger according to claim 1, characterized in that The multi-patterning further includes one or more of the following evolution stages: the evolution stage of nanopillar @reentrant between nano plate and nano mushroom; the single or sequential evolution stages of nano tower and nanocone between nano mushroom and nano pillar; the evolution stage of nano pencil that appears in at least one period during the nano pillar stage; Among them, nano pillar @reentrant is a mask with a nano pillar silicon structure below and a mask with a substantially flat upper surface above, nano tower is a mask with a nano pillar silicon structure below and a hat shape with at least two layers of fan-shaped cross-sections above, nano cone is a silicon structure or mask with a triangular longitudinal cross-section, nano pencil is a special nano pillar structure with an aspect ratio, a silicon structure with a trapezoidal cross-section in the longitudinal cross-section, and a convex arc on the upper surface in the cross-section.

14. The product obtained by the inlaid layer-triggered multi-patterning nanosphere lithography method according to any one of claims 1-13.

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