A processing method for a gradient film layer and a processing method for a gradient depth micro-nano structure

Abstract

The present invention relates to a processing method for a gradient film layer and a processing method for a gradient-depth micro-nano structure. The processing method for the gradient film layer includes the following steps: fixing a planar film layer on the surface of a substrate; forming a sacrificial film layer with a gradually changing thickness on the surface of the planar film layer through gradient coating and / or exposure and development; based on the etching selectivity ratio, removing the sacrificial film layer and the planar film layer above the gradient surface in sequence through dry etching to obtain a substrate with a gradient film layer; the processing method for the gradient-depth micro-nano structure includes the following steps: forming a photoresist film on the surface of the gradient film layer and patterning the photoresist film in the gradient structure region; through etching and resist removal, removing the photoresist film and the gradient film layer in the gradient structure region in sequence, and after the etching is completed, through post-treatment, a gradient-depth micro-nano structure is obtained. The present invention has the effects of improving the processing flexibility, increasing the thickness control range of the gradient film layer, and obtaining a gradient-depth micro-nano structure with a continuous depth change.

Description

Technical Field

[0001] The present invention relates to the technical field of optical element processing, and particularly to a processing method for a gradient film layer and a processing method for a gradient-depth micro-nano structure. Background Art

[0002] Gradient-thickness film systems exhibit broad application prospects due to their unique optical properties and excellent performance. The main application areas include: 1. Optical thin films: Gradient-thickness films can precisely control reflection and transmission characteristics and are widely used in anti-reflection coatings, filters, etc.; 2. Sensors: Suitable for gas, temperature, and humidity sensors, thanks to their high sensitivity to environmental changes; 3. Display technology: In liquid crystal displays and OLED screens, gradient-thickness films can improve image quality and color performance; 4. Solar cells: In photovoltaic technology, gradient films can enhance light capture efficiency and thus increase the energy conversion rate; 5. Biomedicine: In biosensors and drug delivery systems, gradient-thickness film systems are favored for their excellent biocompatibility and controllability. With the continuous progress of material science and manufacturing technology, the application potential of gradient-thickness film systems will be further expanded.

[0003] As a consumer electronic product that may replace smartphones in the future, the optical system of AR glasses can expand the image generated by the optical engine from a small projection source to a larger display area for users to view clearly. Therefore, the gradient coating process will become a key link in AR glasses manufacturing. Currently, there are mainly two methods to achieve the gradient coating process: one is to keep the substrate stationary during the magnetron sputtering coating process and achieve gradient coating by adjusting the relative position between the target gun and the substrate and fixing the irradiation direction of the sputtering glow; the other is to use a baffle with a specific-shaped opening to achieve gradient coating. Both of these methods belong to the technology of directly depositing to form a gradient-thickness film layer. In the magnetron sputtering inclined coating scheme, the coating rate is higher in the area of the substrate closer to the target gun. However, due to space limitations, the rate difference change at each point on the substrate is limited, which results in poor controllability of the film layer gradient range. In addition, since the actual coating result is difficult to accurately predict through theoretical calculation, each time the gradient film layer needs to be adjusted, a large number of experiments must be relied on to determine the coating parameters, which reduces the operation flexibility. When using the method of a baffle with a specific-shaped opening, each time the need to adjust the gradient film layer requires re-designing and processing the baffle fixture, which not only reduces flexibility but also increases costs and needs to be improved.

[0004] In the field of AR optical waveguide technology, a gradually varying depth micro-nano structure refers to a continuous and progressive geometric form formed at the micro-nano scale through fine control of the gradual change of the structure depth. Such structures play an important role in multiple fields such as optics, materials science, and surface engineering. The remarkable feature of the gradually varying depth micro-nano structure is that the structure depth changes along a specific direction, thereby generating unique physical properties, providing broad application prospects for fields such as optics, acoustics, and surface engineering. Currently, the mainstream technical method is to divide the structure into regions with different etching depths and achieve the processing of three-dimensional structures through the alternation of photolithography and etching. However, this partitioned etching scheme has the following defects: First, in order to obtain a more uniform display effect, more depth partitions are required when preparing the grating template, which not only increases the processing procedures but also makes the overall processing cycle longer, thereby affecting the overall processing yield; Second, multiple overlay exposures in the photolithography process are prone to overlay accuracy errors between partitions, thus affecting the display effect; Finally, although the depth is consistent within the same region in partitioned etching, there is still a stepped depth change between different regions, and a truly continuous depth change cannot be achieved. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the first object of the present invention is to provide a processing method for a gradually varying film layer, which has the advantages of simple processing, improved processing flexibility, and an increased thickness control range of the gradually varying film layer.

[0006] The second object of the present invention is to provide a processing method for a gradually varying depth micro-nano structure, which has the advantage of obtaining a gradually varying depth micro-nano structure with a continuous depth change.

[0007] To achieve the above first object, the present invention provides the following technical solutions:

[0008] A processing method for a gradually varying film layer, comprising the following steps,

[0009] S11 Prepare a substrate and fix a planar film layer on the surface of the substrate;

[0010] S12 Through gradually varying coating and / or exposure and development, form a sacrificial film layer with a gradually varying thickness on the surface of the planar film layer, and there is an etching selectivity between the planar film layer and the sacrificial film layer;

[0011] S13 Based on the etching selectivity, through dry etching, sequentially remove the sacrificial film layer and the planar film layer above the gradually varying surface. After the etching is completed, through post-treatment, obtain a substrate with a gradually varying film layer.

[0012] Further, in the step S11, the substrate is first immersed in acetone and isopropyl alcohol in sequence, ultrasonically cleaned with 40KHz for 8 - 12 minutes, dried with nitrogen, then baked at 100 - 130 °C for 25 - 35 minutes, and then the substrate is evenly split into pieces to obtain a strip-shaped substrate.

[0013] Further, in the step S11, a planar film layer is fixed on the surface of the substrate by means of coating, film deposition (such as electron beam evaporation, sputter, PECVD, etc.), bonding, adsorption, or bonding.

[0014] Further, in the step S11, a planar film layer is fixed on the surface of the substrate by electron beam evaporation, controlling the electron beam current to be 50 - 70 mA, the evaporation rate to be 5 - 15 Å / s, the film deposition thickness to be 100 - 1000 nm, and the evaporation material to be one or a combination of materials such as Si, SiO 2 、SiN x 、TiO 2 、Al 2 O 3 、AlN.

[0015] Further, in the step S12, a sacrificial film layer with a gradually changing thickness is directly formed on the surface of the planar film layer by gradient film deposition. The sacrificial film layer is a composite thin film of one or several of Cr, Ti, Al, Si, and Mo.

[0016] Or, in the step S12, a sacrificial film layer with a uniform thickness is first formed on the surface of the planar film layer. The sacrificial film layer is a photoresist film (1 - 10 μm, such as AZ1500 photoresist, AZ1518 photoresist, APR - 5350 photoresist, AZ4562 photoresist, etc.). Then, an optical mask template with a gradually changing thickness is prepared, and the sacrificial film layer with a uniform thickness is exposed and developed to obtain a sacrificial film layer with a gradually changing thickness.

[0017] Furthermore, in the step S12, if the sacrificial film layer is a photoresist film, the etching selectivity range between the planar film layer and the sacrificial film layer is controlled to be 1:8 - 60; otherwise, the etching selectivity range between the planar film layer and the sacrificial film layer is controlled to be 5 - 83:1.

[0018] Still further, in the step S12, a mask layer with a gradually changing thickness is directly formed on the surface of a blank mask template by gradient film deposition. The mask layer is a composite thin film of one or several of Cr, Ti, Al, and Mo to obtain an optical mask template with a gradually changing thickness.

[0019] Further, in the step S12, the specific implementation of the gradient coating is as follows: first, the target gun is installed above one side of the substrate or the blank mask plate at an angle between the sputtering direction and the substrate or the blank mask plate, and then the sacrificial film layer or the mask layer is obtained through magnetron sputtering. Among them, since the atoms or atomic clusters of the sputtered thin film material have good directivity, the deposition rate of the film layer is faster at the position closer to the target gun on the substrate, and conversely, the deposition rate of the film layer is slower at the position farther from the target gun, and the change of the deposition rate with the position is linearly uniform. Just keep the substrate stationary during sputtering, and a film layer with a continuously and uniformly changing thickness can be deposited; by changing the angle between the target gun orientation and the substrate plane (30° - 60°, preferably 45°), the relative position of the target gun and the substrate, and the sputtering time, the degree of change of the thin film thickness can be adjusted to a certain extent.

[0020] Further, in the step S12, the specific implementation of the exposure and development is as follows: first, a contact lithography machine (Suss MA6) is used, and exposure is performed on the sacrificial film layer with a uniform thickness using an optical mask template with a gradually changing thickness. The sacrificial film layer is an AZ4562 photoresist film with a thickness of 5 - 10 μm, and the exposure dose is controlled to be 300 - 800 mJ / cm 2 , and then the exposed sacrificial film layer is developed with AZ300 - MIF developer for 30 - 150 s to remove part of the photoresist and obtain a sacrificial film layer with a gradually changing thickness.

[0021] Further, in the step S13, the specific implementation of the dry etching is as follows: dry etching is carried out through a RIBE device, and the BMV of the RIBE is controlled to be 300 - 600 V, the BMI is 40 - 400 mA, the gas flow rate of Ar is 0 - 80 sccm, and the gas flow rate of CF 4 is 0 - 30 sccm, the gas flow rate of CHF 3 is 0 - 30 sccm, the gas flow rate of O 2 is 0 - 30 sccm, and the gas flow rate of SF 6 is 0 - 30 sccm.

[0022] Alternatively, in the step S13, the specific implementation of the dry etching is as follows: dry etching is carried out through an ICP - RIE device, and the Source Power of the ICP is controlled to be 300 - 600 W, the Bias Power is 100 - 200 W, the gas flow rate of Ar is 0 - 80 sccm, and the gas flow rate of CF 4 is 0 - 30 sccm, the gas flow rate of CHF 3 is 0 - 30 sccm, the gas flow rate of O 2 is 0 - 30 sccm, and the gas flow rate of SF 6The gas flow rate is 0 to 30 sccm.

[0023] RIBE and ICP control the etching selectivity in the same principle. For different combinations of sacrificial film layers and planar film layers, several types of the gases can be selected as the process gases. Among the selected process gases, there is a gas that has a strong etching effect on one of the sacrificial film layer and the planar film layer, while having a weak etching effect on the other film layer. Thus, the etching selectivity between the sacrificial film layer and the planar film layer can be changed by changing the gas flow rate of this gas. Suppose the etching selectivity between the sacrificial film layer and the planar film layer is k, and the gradient thickness difference of the sacrificial film layer is x. The gradient film layer thickness difference finally obtained is x / k. From this, it can be seen that when k > 1, the gradient thickness difference of the sacrificial film layer can be reduced by etching and transferred to the planar film layer; when k < 1, the gradient thickness difference of the sacrificial film layer can be amplified by etching and transferred to the planar film layer, so as to adjust the gradient thickness difference within the same range by adjusting the etching selectivity.

[0024] Further, in the S13, after the dry etching is completed, N-methyl-2-pyrrolidone (NMP) or acetone is used for degumming and cleaning, and then Plasma treatment is performed at 100 - 300 W for 1 - 10 min.

[0025] To achieve the above first object, the present invention provides the following technical solutions:

[0026] A processing method for a gradient-depth micro-nano structure, comprising the following steps:

[0027] S1 According to the above processing method of the gradient film layer, a substrate with a gradient film layer is obtained;

[0028] S2 A photoresist film is formed on the surface of the gradient film layer, and the photoresist film in the gradient structure region is patterned;

[0029] S3 By etching and degumming, the photoresist film and the gradient film layer in the gradient structure region are sequentially removed, and after post-treatment after the etching is completed, a gradient-depth micro-nano structure is obtained.

[0030] Further, in the S2, the thickness of the photoresist film is controlled to be 0.1 - 10.0 μm, and the photoresist of the photoresist film is Zep520 photoresist, AZ1500 photoresist, AZ1518 photoresist, APR-5350 photoresist or AZ4562 photoresist.

[0031] Further, in the step S2, the specific implementation of the patterning is as follows: First, use an EBL device, a laser direct writing lithography machine or a contact lithography machine to expose the photoresist film, then use a developer to develop the sample, and then perform Plasma treatment at 100 - 300W for 1 - 5 minutes to form grating grooves in the gradient structure area of the photoresist film.

[0032] Further, in the step S3, the specific implementation of the etching and de-gluing is as follows: Perform etching and de-gluing through an ICP-RIE device, control the gas flow rate of Ar to be 0 - 80 sccm, CF 4 The gas flow rate of is 0 - 30 sccm, CHF 3 The gas flow rate of is 0 - 30 sccm, O 2 The gas flow rate of is 0 - 30 sccm, SF 6 The gas flow rate of is 0 - 30 sccm, the RF power is 100 - 800W, the Bias power is 50 - 300W, the chamber pressure is 5 - 20 mTorr, the etching rate is 3 - 10 nm / s. After etching the gradient film layer to the required depth, use N-methyl-2-pyrrolidone (NMP) or acetone for de-gluing and cleaning, and then perform Plasma treatment at 100 - 300W for 1 - 10 minutes.

[0033] In summary, the beneficial technical effects of the present invention are as follows:

[0034] 1. Based on the existing gradient coating process, the present invention deposits the directly deposited high-slope gradient film as a sacrificial film layer on top of a uniform planar film layer. The coating parameters of the sacrificial film layer can be fixed at several specific values. Etch the planar film layer using the sacrificial film layer as a mask, and adjust the etching selectivity ratio between the sacrificial film layer and the planar film layer to control the gradient range of the final planar film layer; Since the adjustable range of the etching selectivity ratio is relatively large, the thickness change range of the gradient film is greatly increased. And due to the setting of the coating parameters of the sacrificial film layer, when facing a large range of gradient requirements, it is not necessary to design and process a large number of shielding fixtures or conduct a large number of process verification experiments, improving efficiency and reducing costs, and greatly improving the processing flexibility;

[0035] 2. The present invention uses the method of gray-scale lithography. After one processing of the gradient film layer, one patterning of the photoresist film layer, and two etching processes of the photoresist film and the gradient film layer, a grating structure with a gradient depth can be obtained on the gradient film layer, greatly shortening the process flow, improving the processing efficiency and processing yield, reducing the processing cost, eliminating the need for lithography overlay of structural partitions, and avoiding the errors caused by lithography overlay;

[0036] 3. The present invention obtains an optical mask with a gradually changing thickness through gradient coating, and then uses the effect that the ultraviolet light transmittance of different thickness mask layers is different to perform gray-scale exposure to obtain a sacrificial film layer with a gradually changing thickness. Then, through etching, a substrate with a gradient film layer is obtained. Among them, by adjusting the coating parameters and etching parameters, film layers with different changing trends can be obtained, which can cover various requirements, greatly simplifies the process flow, improves the processing efficiency and processing yield, can significantly reduce the processing cost, and also avoids the accuracy error between the structures in different regions caused by multiple alignment exposures. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a flowchart of the method provided in Embodiment 1 of the present invention.

[0038] Figure 2 is an SEM image of the left region of the gradually changing depth micro-nano structure prepared in Embodiment 18 of the present invention.

[0039] Figure 3 is an SEM image of the right region of the gradually changing depth micro-nano structure prepared in Embodiment 18 of the present invention.

[0040] Figure 4 is an SEM image of the left region of the gradually changing depth micro-nano structure prepared in Embodiment 20 of the present invention.

[0041] Figure 5 is an SEM image of the right region of the gradually changing depth micro-nano structure prepared in Embodiment 20 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] In order to make the technical means, creative features, achieved purposes and functions of the present invention clearer and easier to understand, the present invention will be further described below in conjunction with the drawings and specific embodiments.

[0043] Embodiment 1: Refer to Figure 1 , a method for processing a gradient film layer disclosed in the present invention, includes the following steps,

[0044] S11 Prepare a substrate and fix a planar film layer on the surface of the substrate;

[0045] S12 Through gradient coating and / or exposure and development, form a sacrificial film layer with a gradually changing thickness on the surface of the planar film layer, and there is an etching selectivity between the planar film layer and the sacrificial film layer;

[0046] S13 Based on the etching selectivity, through dry etching, sequentially remove the sacrificial film layer and the planar film layer above the gradient surface. After the etching is completed, through post-treatment, a substrate with a gradient film layer is obtained.

[0047] The present invention also discloses a method for processing a gradually changing depth micro-nano structure, including the following steps,

[0048] S1 According to the processing method of the gradient film layer above, a substrate with a gradient film layer is obtained;

[0049] S2 A photoresist film is formed on the surface of the gradient film layer, and the photoresist film in the gradient structure region is patterned;

[0050] S3 By etching and removing the photoresist, the photoresist film and the gradient film layer in the gradient structure region are removed in sequence. After the etching is completed, post-treatment is carried out to obtain a gradient-depth micro-nano structure.

[0051] Embodiment 2: A processing method of a gradient film layer disclosed in the present invention. The difference from Embodiment 1 is that it includes the following steps.

[0052] S11 First, the substrate (silicon wafer) is successively immersed in acetone and isopropyl alcohol, and ultrasonically cleaned at 40 KHz and 600 W for 8 - 12 min, dried with nitrogen, then baked at 120 °C for 30 min. Then, the substrate is evenly split to obtain four strip-shaped substrates of 12 cm in length. Then, a planar film layer is fixed on the surface of the substrate by electron beam evaporation. The electron beam current is controlled at 55 - 60 mA, the evaporation rate is 8 Å / s, the coating thickness is 600 nm, and the evaporation material is SiO 2 , baked at 200 °C, and assisted by an argon ion source;

[0053] S12 First, the target gun is installed above one side of the substrate at an angle of 45° with the substrate in the sputtering direction. Among them, the substrates are arranged side by side along the direction of the target gun on the coating carrier, and the center of the whole group of substrates is located at the center of the coating carrier. Then, a sacrificial film layer with a gradually changing thickness is obtained by magnetron sputtering. Coating parameters: DC 200 W, 80 sccm of argon gas is passed, the sputtering pressure is 0.3 Pa, the coating time is 5 min, the sacrificial film layer is a Cr thin film, and it is measured by a film thickness meter that the thickness of the Si thin film changes from 30.8 nm to 52.2 nm within a length range of 10 cm, and the thickness difference is 21.4 nm;

[0054] S13 Dry etching is carried out by a RIBE device, and the BMV of the RIBE is controlled at 500 V, the BMI is 320 mA, and the ACV is 80 V; control the gas flow rate of CF 4 to be 20 sccm, the gas flow rate of Ar to be 6 sccm, and the gas flow rate of O 2 to vary within the range of 4 - 20 sccm; among them, the larger the gas flow rate of O 2 , the higher the etching selectivity ratio between the planar film layer SiO 2 and the sacrificial film layer Cr. By adjusting O 2The gas flow rate can achieve an adjustable etching selectivity ratio of the planar film layer to the sacrificial film layer in the range of 8 - 50:1, and finally obtain a gradient film layer directly grown on the substrate in the required area. After the dry etching is completed, N-methyl-2-pyrrolidone (NMP) or acetone is used for degumming and cleaning, and then plasma treatment is carried out at 100 - 300 W for 1 - 10 min.

[0055] Examples 3 - 5: A processing method of a gradient film layer disclosed in the present invention, different from Example 2 in that the technical parameters of the planar film layer, the sacrificial film layer and the gradient film layer are shown in Table 1.

[0056] Table 1

[0057] Planar film layer thickness / nm Thickness difference of 10 cm sacrificial film layer / nm Etch selectivity Thickness difference of 10 cm graded film layer / nm Thickness difference of 1 cm graded film layer / nm Example 2 600 21.4 8：1 173.4 17.3 Example 3 600 21.4 14：1 295.3 29.5 Example 4 600 21.4 20：1 432.3 43.2 Example 5 600 21.4 26：1 550.9 55.1

[0058] Examples 6 - 9: A processing method of a gradient film layer disclosed in the present invention, different from Example 2 in that the coating materials of the planar film layer are Si, SiN x , Al 2 O 3 , TiO 2 , and the process parameters of the dry etching are shown in Table 2.

[0059] Table 2

[0060] Planar film layer material Sacrificial film layer material Etching process Power parameter Gas flow rate / sccm Etch selectivity range Example 6 Si Cr RIBE BMV = 500V, BMI = 80mA <![CDATA[Ar: SF 6 = 10: 10~60]]> 5~83：1 Example 7 <![CDATA[SiN x > Cr RIBE BMV = 500V, BMI = 160mA <![CDATA[Ar: SF 6 = 10: 10~60]]> 5~56：1 Example 8 <![CDATA[Al 2 O 3 > Cr RIBE BMV = 400V, BMI = 160mA <![CDATA[Ar: CHF 3 = 10: 10 to 60]]> 5~40：1 Example 9 <![CDATA[TiO 2 > Cr RIBE BMV = 400V, BMI = 100mA <![CDATA[Ar: CHF 3 : SF 6 = 10:10:10~60]]> 5~36：1

[0061] Examples 10 - 13: A processing method of a gradient film layer disclosed in the present invention, different from Example 2 in that the coating materials of the sacrificial film are Si, Ti, Al, Mo in sequence, and the process parameters of the dry etching are shown in Table 3.

[0062] Table 3

[0063] Planar film layer material Sacrificial film layer material Etching process Power parameter Gas flow rate / sccm Etch selectivity range Example 10 <![CDATA[SiO 2 > Si ICP Source Power = 800W, Bias Power = 150W <![CDATA[CHF 3 : O 2 = 20: 5~60]]> 5~55：1 Example 11 <![CDATA[SiO 2 > Ti RIBE BMV = 400V, BMI = 320mA <![CDATA[CHF 3 : Ar = 5 to 60:10]]> 5~73：1 Example 12 <![CDATA[SiO 2 > Al RIBE BMV = 400V, BMI = 320mA <![CDATA[CHF 3 : Ar = 5 to 60:10]]> 5~67：1 Example 13 <![CDATA[SiO 2 > Mo RIBE BMV = 400V, BMI = 320mA <![CDATA[CHF 3 : Ar = 5 to 60:10]]> 5~56：1

[0064] Example 14: A processing method of a gradient film layer disclosed in the present invention, different from Example 1 in that it includes the following steps

[0065] S11 First, the substrate (silicon wafer) is successively immersed in acetone and isopropyl alcohol, and ultrasonically cleaned at 40 KHz and 600 W for 8 - 12 min, dried with nitrogen, then baked at 120 °C for 30 min, and then the substrate is evenly cleaved to obtain four long strip-shaped substrates of 12 cm. Then, a planar film layer is fixed on the surface of the substrate by electron beam evaporation, controlling the electron beam current to be 55 - 60 mA, the evaporation rate to be 8 Å / s, the coating thickness to be 600 nm, and the evaporation material to be SiO 2 , baked at 200 °C, and assisted by an argon ion source;

[0066] S12 Use a spin coater to spin coat a layer of AZ4562 photoresist on the surface of the gradient film layer. Control the spin coating speed at 4000 rpm, the baking temperature at 100 °C, and the baking time at 60 s to obtain a sacrificial film layer with a thickness of about 6 μm. Then, through gradient coating, form a mask layer with a gradually changing thickness on the surface of another blank optical mask. The mask layer is a Cr thin film to obtain an optical mask with a gradually changing thickness. Alternatively, the substrate with a sacrificial film layer prepared in S12 of Example 2 can be directly selected as the optical mask with a gradually changing thickness. Then, use a contact lithography machine (Suss MA6) and use the optical mask with a gradually changing thickness to expose the sacrificial film layer with a uniform thickness. The sacrificial film layer is a 5 - 10 μm AZ4562 photoresist film. Control the exposure dose to be 300 - 800 mJ / cm 2 , then use AZ300 - MIF developer to develop the exposed sacrificial film layer for 120 s. Weak development is required to remove part of the photoresist to obtain a sacrificial film layer with a gradually changing thickness. Use a film thickness gauge to measure that the thickness change of the sacrificial film layer within a 3 cm length range is 2.59 - 3.58 μm;

[0067] S13 Use an ICP device to etch and remove the photoresist, control the gas flow rate of CHF 3 to be 10 sccm, the gas flow rate of O 2 to be 8 - 40 sccm, the Source Power to be 600 W, the Bias Power to be 180 W, and the chamber pressure to be 15 mtorr. By adjusting the gas flow rate of O 2 , the etching selectivity between the planar film layer and the gradient photoresist film can be adjusted within the range of 1:8 - 60. After etching the gradient film layer to the required depth, soak it in N - methyl - 2 - pyrrolidone (NMP) at 80 °C with 40 Khz ultrasonic soaking for 1 h, ultrasonically clean it with isopropanol for 10 min, and then perform Plasma treatment at 100 W for 5 min to finally obtain a gradient film layer in the required area.

[0068] Examples 15 - 17: A processing method for a gradient film layer disclosed in the present invention. The difference from Example 14 is that the mask layer is successively a Ti, Al, and Mo thin film.

[0069] Example 18: A processing method for a gradient depth micro - nano structure disclosed in the present invention. The difference from Example 1 is that it includes the following steps,

[0070] S1 According to the processing method of the gradient film layer in Example 14, obtain a substrate with a gradient film layer;

[0071] S2 First, use a spin coater to spin coat a layer of AZ4562 photoresist on the surface of the graded film layer to obtain a photoresist film. Use an EBL device, a laser direct writing lithography machine, or a contact lithography machine to expose the photoresist film, and then use a developer to develop the sample. Then, perform Plasma treatment at 100 - 300W for 1 - 5 minutes to form grating grooves in the graded structure area of the photoresist film and ensure that there is no residual photoresist in the grating grooves;

[0072] S3 Use an ICP device to etch and remove the photoresist and obtain a straight grating. Control the Source Power of the ICP to be 500W, the BiasPower to be 150W, the chamber pressure to be 14mtorr, the gas flow rate of CHF 3 to be 10sccm, and the gas flow rate of O 2 to be 16sccm. The etching rate of the graded film layer is 7nm / s. Stop etching when reaching the substrate, and a straight grating with continuously varying depth is obtained. Refer to Figure 2 and Figure 3 , SEM images at different depths of the graded depth straight grating can be seen. The magnification is 50K for all, and it can be seen that the depth does change and the change is uniform.

[0073] Example 19: A processing method for a graded depth micro - nano structure disclosed by the present invention. The difference from Example 18 is that in S1, according to the processing method of the graded film layer in Example 2, a substrate with a graded film layer is obtained.

[0074] Example 20: A processing method for a graded depth micro - nano structure disclosed by the present invention. The difference from Example 18 is that in S3, use a RIBE device to etch and remove the photoresist and obtain an inclined grating. Control the BMV of the RIBE device to be 500V, the BMI to be 150mA, the gas flow rate of CHF 3 to be 28sccm, the gas flow rate of Ar to be 8sccm. The etching rate of the graded film layer is 5.5nm / s. Stop etching when reaching the substrate, and an inclined grating with continuously varying depth is obtained. Refer to Figure 4 and Figure 5 , SEM images at different depths of the graded depth inclined grating can be seen. The magnification is 50K for all, and it can be seen that the depth does change and the change is uniform.

[0075] 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 purpose and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A method for processing a gradient film layer, characterized in that: The following steps are included: S11 prepares a substrate, and fixes a planar film layer on the surface of the substrate; S12 forms a sacrificial film layer with a gradient thickness on the surface of the planar film layer by gradient coating and / or exposure and development, and an etching selectivity ratio exists between the planar film layer and the sacrificial film layer; S13 removes the sacrificial film layer and the planar film layer above the gradient surface in sequence through dry etching based on the etching selectivity, and obtains a substrate with a gradient film layer through post-processing after the etching is completed.

2. The method for processing a gradient film layer according to claim 1, characterized in that: In the S11, the planar film layer is Si, SiO2, SiN x , TiO2, Al2O3, AlN or a composite film of one or more thereof.

3. The method for processing a gradient film layer according to claim 1, characterized in that: In S12, a sacrificial film layer with a gradient thickness is directly formed on the surface of the planar film layer by gradient coating, and the sacrificial film layer is a composite film of one or more of Cr, Ti, Al, Si, and Mo, and the etching selectivity ratio between the planar film layer and the sacrificial film layer is controlled to be in the range of 5 to 83:

1.

4. The method for processing a gradient film layer according to claim 1, characterized in that: In the S12, a sacrificial film layer with uniform thickness is first formed on the surface of the planar film layer, and the sacrificial film layer is a photoresist film. Then, an optical mask with a gradient thickness is prepared, and the sacrificial film layer with uniform thickness is exposed and developed to obtain a sacrificial film layer with a gradient thickness. The etching selectivity ratio between the planar film layer and the sacrificial film layer is controlled to be in the range of 1:8~60.

5. The method for processing a gradient film layer according to claim 4, characterized in that: In S12, a mask layer with a gradient thickness is formed directly on the surface of the blank mask by gradient coating in advance, and the mask layer is a composite thin film of one or more of Cr, Ti, Al, and Mo to obtain an optical mask with a gradient thickness.

6. The method for processing a gradient film layer according to claim 1, characterized in that: In the S13, the specific implementation method of the dry etching is to perform dry etching through a RIBE device, control the BMV of RIBE to 300~600V, the BMI to 40~400mA, the gas flow rate of Ar to 0~80sccm, the gas flow rate of CF4 to 0~30sccm, the gas flow rate of CHF3 to 0~30sccm, the gas flow rate of O2 to 0~30sccm, and the gas flow rate of SF6 to 0~30sccm.

7. The method for processing a gradient film layer according to claim 1, characterized in that: In S13, the specific implementation method of the dry etching is to perform dry etching through ICP-RIE equipment, control the Source Power of ICP to 300~600W, the Bias Power to 100~200W, the gas flow rate of Ar to 0~80sccm, the gas flow rate of CF4 to 0~30sccm, the gas flow rate of CHF3 to 0~30sccm, the gas flow rate of O2 to 0~30sccm, and the gas flow rate of SF6 to 0~30sccm.

8. A method for processing a micro-nano structure with a gradient depth, characterized in that: The following steps are included: S1 The method for processing a gradient film layer according to any one of claims 1 to 7, to obtain a substrate with a gradient film layer; S2 forming a photoresist film on the surface of the gradient film layer, and patterning the photoresist film in the gradient structure area; S3 removes the photoresist film and the gradient film layer in the gradient structure area in sequence by etching and removing the resist. After the etching is completed, post-processing is performed to obtain a gradient depth micro-nano structure.

9. The method for processing a micro-nano structure with a gradient depth according to claim 8, characterized in that: In S2, the thickness of the photoresist film is controlled to be 0.1-10.0 μm, and the photoresist of the photoresist film is Zep520 photoresist, AZ1500 photoresist, AZ1518 photoresist, APR-5350 photoresist or AZ4562 photoresist.

10. The method for processing a micro-nano structure with a gradient depth according to claim 8, characterized in that: In S3, the specific implementation method of the etching and degumming is to perform etching and degumming through ICP-RIE equipment, control the gas flow rate of Ar to 0~80sccm, the gas flow rate of CF4 to 0~30sccm, the gas flow rate of CHF3 to 0~30sccm, the gas flow rate of O2 to 0~30sccm, the gas flow rate of SF6 to 0~30sccm, the RF power to 100~800W, the Bias power to 50~300W, the chamber pressure to 5~20mTorr, and the etching rate to 3~10nm / s. After etching the gradient film layer to the required depth, use N-methyl-2-pyrrolidone (NMP) or acetone for degumming and cleaning, and then perform Plasma treatment at 100~300W for 1~10min.

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