Laser direct writing device and laser direct writing method

Abstract

The present invention relates to a laser direct writing device and a laser direct writing method, which sequentially comprise a first light source, an optical diffraction element, a multi-channel acousto-optic modulator, a first sleeve lens, a first objective lens and a first writing platform in the direction of light path propagation; the optical diffraction element is used to divide a light beam emitted by the first light source into at least two first sub-beams, the diameter of each of the first sub-beams is equal or substantially equal, and the diameter of the first sub-beam is smaller than the entrance pupil diameter of the first objective lens; the multi-channel acousto-optic modulator is used to adjust the light intensity of each of the first sub-beams.

Description

Technical Field

[0001] The invention relates to the field of laser direct writing, and in particular to a laser direct writing device and a laser direct writing method. Background Art

[0002] Nanocolumnar structure is a typical micro-nano structure and is widely used in supersurfaces, hydrophobic surfaces, self-assembled structures, microbial culture dishes and other fields.

[0003] As the scope of use of nano-columnar structures increases, the design requirements of nano-columnar structures gradually expand from micron size to sub-wavelength size, from periodic structure to non-periodic structure, and from small area design to large area design. In other words, the design requirements of nano-columnar structures gradually become flexible and diversified, which leads to increasingly complex preparation processes, and significantly increases the preparation cycle and preparation cost. Summary of the invention

[0004] Based on this, it is necessary to provide a laser direct writing device and a laser direct writing method to address the problems of long preparation cycle and high cost of nano-columnar structures.

[0005] A laser direct writing device comprises a first light source, an optical diffraction element, a multi-channel acousto-optic modulator, a first sleeve lens, a first objective lens and a first writing platform in sequence in the direction of light path propagation;

[0006] The optical diffraction element is used to split the light beam emitted by the first light source into at least two first sub-beams, the diameter of each of the first sub-beams is equal or substantially equal, and the diameter of the first sub-beams is smaller than the entrance pupil diameter of the first objective lens, and the multi-channel acousto-optic modulator is used to adjust the light intensity of each of the first sub-beams.

[0007] The laser direct writing device of the present invention further includes a first lens, which is located between the optical diffraction element and the multi-channel acousto-optic modulator, and is used to collimate the first sub-beam.

[0008] A laser direct writing method, based on a laser direct writing device, the laser direct writing method comprises:

[0009] Before preparing the nanopillars, determine the designed height of the nanopillars H ;

[0010] At least based on H , determining a target light intensity of the first sub-beam;

[0011] The multi-channel acousto-optic modulator adjusts the actual light intensity of the first sub-beam so that the actual light intensity of the first sub-beam matches the target light intensity;

[0012] The first sub-beam after light intensity modulation is used to expose the corresponding position of the photoresist to obtain the nano-column.

[0013] The present invention also includes:

[0014] Get the beam quality factor of the first light source M 2 , the first light source corresponds to the emission wavelength λ , the equivalent focal length of the first objective lens f And the designed focal depth of the first sub-beam is L ;

[0015] At least based on M 2 , λ , f , L Determine the target diameter of the first sub-beam D ;

[0016] The optical diffraction element adjusts the actual diameter of the first sub-beam so that the actual diameter of the first sub-beam matches the target diameter. D .

[0017] The present invention also includes:

[0018] Get the polymerization threshold of the photoresist S ;

[0019] At least based on H , f、L and S Determine the target light intensity and target exposure time of the first sub-beam t ;

[0020] The first light source controls the actual exposure time of the first sub-beam so that the actual exposure time of the first sub-beam matches the target exposure time t .

[0021] The present invention also includes:

[0022] Before preparing nanopillars, determine the design radius of the nanopillars R ;

[0023] At least based on R A target light intensity and a target exposure time of the first sub-beam are determined.

[0024] The present invention also includes:

[0025] Before fabricating the nanorods, determine the designed phase modulation amount of the nanorods φ , Refractive index of photoresist after curing n refand the refractive index of air n 0 ;

[0026] At least based on φ , λ, D, H Determine the target spacing between two adjacent nanopillars P ;

[0027] The optical diffraction element is based at least on P , n ref and n 0 The distance between two adjacent first sub-beams is adjusted.

[0028] The present invention , , , , ,in I 0 is the light intensity at the waist of the first sub-beam.

[0029] A laser direct writing device comprises, in order in the direction of light path propagation, a first light source, a light homogenizing and beam expanding assembly, a digital micromirror array, a microlens array, a first sleeve lens, a first objective lens and a first writing platform;

[0030] The digital micromirror array is used to form at least two second sub-beams. The digital micromirror array adjusts the light intensity of each of the second sub-beams by controlling the number of opened sub-micromirrors and makes the diameter of each of the second sub-beams not less than 40 μm, so that the focal depth of each of the second sub-beams at the photoresist is equal or substantially equal.

[0031] A laser direct writing device comprises, in order in the direction of light path propagation, a first light source, a light homogenizing and beam expanding assembly, a digital micromirror array, a microlens array, a first sleeve lens, a first objective lens and a first writing platform;

[0032] The digital micromirror array is used to form at least two second sub-beams. The digital micromirror array adjusts the light intensity of each of the second sub-beams by controlling the number of opened sub-micromirrors and makes the diameter of each of the second sub-beams less than 40 μm, so as to allow the digital micromirror array to individually adjust the focal depth of each of the second sub-beams at the photoresist.

[0033] The beneficial effects of the present invention are:

[0034] The optical diffraction element can split the light beam emitted by the first light source to form at least two first sub-beams, and the optical diffraction element can uniformly adjust the diameter of the first sub-beams and the spacing between two adjacent first sub-beams. The multi-channel acousto-optic modulator can modulate the light intensity of each first sub-beam separately.

[0035] The first sub-beam after adjusting the light intensity, diameter and spacing is exposed at the corresponding position of the photoresist to obtain nanocolumns. The formation position of the nanocolumns can not only match the designed focal depth, but also match the designed height, designed radius and designed phase modulation amount.

[0036] The laser direct writing device of the present invention can simultaneously expose and obtain a plurality of nanocolumns with different size specifications, which not only meets the requirements of design flexibility, but also greatly improves the preparation efficiency of nanocolumns. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a light path diagram of the laser direct writing device in Example 1 of the present invention;

[0038] Figure 2 Schematic diagram of the focus of the first sub-beam at different diameters in Example 1 of the present invention;

[0039] Figure 3 The light intensity distribution of the focus of the first objective lens in the YZ plane under different power conditions of the multi-channel acousto-optic modulator in Example 1 of the present invention;

[0040] Figure 4 Schematic diagram of the three-dimensional structure of the nanocolumn in Example 1 of the present invention;

[0041] Figure 5 In Example 1 of the present invention P Under different numerical conditions, T / S Graph of the relationship between value and phase change;

[0042] Figure 6 The phase distribution diagram required for the superlens on the XY cross section in Example 1 of the present invention;

[0043] Figure 7 The XY section of the super lens in Example 1 of the present invention T / S Numerical distribution graph;

[0044] Figure 8 This is a light path diagram of the laser direct writing device in Example 2 of the present invention;

[0045] Fig. 9 Graph showing the relationship between the diameter of the second sub-beam and the focal depth of the second sub-beam in Embodiment 2 of the present invention.

[0046] Reference numerals:

[0047] 1. First light source; 2. Optical diffraction element; 3. First lens; 4. Multi-channel acousto-optic modulator; 5. First sleeve lens; 6. First objective lens; 7. First writing platform; 8. Light homogenization and beam expansion assembly; 9. Digital micromirror array; 10. Microlens array. DETAILED DESCRIPTION

[0048] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0049] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0050] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0051] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0052] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0053] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0054] Embodiment 1:

[0055] See also Figure 1 This embodiment provides a laser direct writing device, which includes a first light source 1, an optical diffraction element 2, a first lens 3, a multi-channel acousto-optic modulator 4, a first tube lens 5, a first objective lens 6 and a first writing platform 7 in sequence in the direction of light propagation.

[0056] The optical diffraction element 2 can split the light beam emitted by the first light source 1 to form at least two first sub-beams. Based on the characteristics of the optical diffraction element 2, the diameter of each first sub-beam is equal or substantially equal, and the diameter of the first sub-beam is smaller than the entrance pupil diameter of the first objective lens 6.

[0057] If there is a difference between the diameters of the first sub-beams, it is mainly caused by equipment errors. For those skilled in the art, it can be clearly determined that the diameters of the first sub-beams are substantially equal. If the diameters of the first sub-beams are substantially equal, the difference between the maximum value of the diameter of the first sub-beam and the minimum value of the diameter of the first sub-beam is not greater than 0.1 mm.

[0058] The optical diffraction element 2 can also adjust the distance between two adjacent first sub-beams.

[0059] The first lens 3 can collimate the first sub-beam generated by the optical diffraction element 2 to make it parallel to the optical axis.

[0060] The collimated first sub-beams enter different channels of the multi-channel acousto-optic modulator 4, so that the multi-channel acousto-optic modulator 4 can modulate the light intensity of each first sub-beam respectively. Accordingly, the light intensities of different first sub-beams can be the same or different.

[0061] The first sub-beam can be exposed at the photoresist to form a nano-column. The actual diameter of the first sub-beam determines the focal depth. In other words, the actual diameter of the first sub-beam determines the formation position of the nano-column. The actual light intensity and actual exposure time of the first sub-beam determine the height and diameter of the nano-column. In addition, the spacing between two adjacent first sub-beams determines the spacing between two adjacent nano-columns.

[0062] In order to obtain nanopillars with specific properties, parameter design is required. The main parameters that need to be designed include the design height of the nanopillars. H , the design radius of the nanopillar R , the designed focal depth of the first sub-beam L and the designed phase modulation amount of the nanorods φ .

[0063] In order to make the actual focal depth of the first sub-beam match the designed focal depth L , it is necessary to adjust the actual diameter of the first sub-beam. In order to make the actual height and actual diameter of the final nanocolumn match the designed height of the nanocolumn H and design diameter R , the actual light intensity and actual exposure time of the first sub-beam also need to be adjusted. In addition, in order to make the actual phase modulation amount of the nanorod match the designed phase modulation amount φ , it is also necessary to adjust the actual spacing between two adjacent nanopillars.

[0064] Based on this, this embodiment also provides a laser direct writing method, including the following steps:

[0065] Step 101: See Figure 4 Before preparing the nanocolumns, the design height of the nanocolumns is designed and determined according to the subsequent practical application requirements of the nanocolumns. H , the design radius of the nanopillar R , the designed focal depth of the first sub-beam L and the designed phase modulation amount of the nanorods φ .

[0066] Step 102: Obtaining the polymerization threshold of the photoresist S、 Refractive index of photoresist after curing n ref , air refractive index n 0 , beam quality factor of the first light source 1M 2 , the first light source 1 corresponds to the emission wavelength λ and the equivalent focal length of the first objective lens 6 f .

[0067] Step 103: At least based on the designed height of the nanopillars H , the design radius of the nanorod R , the designed focal depth of the first sub-beam L , the designed phase modulation amount of the nanorod φ , polymerization threshold of photoresist S、 Refractive index of photoresist after curing n ref , air refractive index n 0 , beam quality factor of the first light source 1 M 2 , the first light source 1 corresponds to the emission wavelength λ and the equivalent focal length of the first objective lens 6 f , determine the target light intensity of the first sub-beam and the target exposure time of the first sub-beam t、 Target diameter of the first sub-beam D and the target spacing between two adjacent nanopillars P .

[0068] Step 104: The optical diffraction element 2 adjusts the actual diameter of the first sub-beam so that the actual diameter of the first sub-beam matches the target diameter. D The optical diffraction element 2 also adjusts the spacing between two adjacent first sub-beams so that the actual spacing between two adjacent nanocolumns matches the target spacing. P .

[0069] Step 105: the multi-channel acousto-optic modulator 4 adjusts the actual light intensity of the first sub-beam so that the actual light intensity of the first sub-beam matches the target light intensity.

[0070] Step 106: The first sub-beam after adjusting the light intensity, diameter and spacing is exposed at the corresponding position of the photoresist to obtain a nano-column, and the formation position of the nano-column can match the designed focal depth. On this basis, the first light source 1 controls the actual exposure time of the first sub-beam so that the actual exposure time of the first sub-beam matches the target exposure time. t The actual height, actual radius and actual phase modulation of the nanorods thus obtained can match the designed height, designed radius and designed phase modulation, respectively.

[0071] In this embodiment, ,pass M 2 ,λ,L,f SolvableD .

[0072] In this embodiment, , , , ,in, w 0 is the spot radius formed after the first sub-beam is focused by the first objective lens 6, I 0 is the light intensity at the waist of the first sub-beam.

[0073] The above relationship reasoning process is as follows:

[0074] At the distance from the waist z At the position of , the radius of the first sub-beam is , ;

[0075] The first sub-beam can be regarded as a Gaussian beam, and its intensity distribution satisfies ;

[0076] Actual exposure metering for the first sub-beam T Need to be equal to the polymerization threshold of the photoresist S ,Right now .

[0077] when x = y =0, z = H / 2, thus we get ;

[0078] when x = z =0, y = R , thus we get ;

[0079] By solving the above two equations together, we can get I 0 and t The specific value of .

[0080] Furthermore, ,in n eff is the equivalent refractive index of the nanorods;

[0081] n eff = S eff n ref +(1- S eff ) n0 , S eff = πR 2 / P 2 , S eff represents the proportion of the cross-sectional area of ​​the nanopillar in the unit structure area;

[0082] Obtained from this .

[0083] Through this φ, f, R, n ref 、n 0 , H You can find the solution P The specific value of .

[0084] See also Figure 2 In this embodiment, the first objective lens 6 is an Olympus UPLXAPO40XO objective lens, and the corresponding entrance pupil diameter is 12.6 mm, and the equivalent focal length is f =4.5mm, the wavelength of the emitted light corresponding to the first light source 1 λ =517nm, beam quality factor of the first light source 1 M 2 =1.2. If the design focal depth of the first sub-beam L =201.5nm, then the target diameter of the first sub-beam must be met D= 12.6mm, accordingly, the first sub-beam needs to be incident on the first objective lens 6 with a full pupil. If the design focal depth of the first sub-beam is L =5.119μm, then the target diameter of the first sub-beam must be met D= 2.5mm.

[0085] See also Figure 3 In (a), the power of the multi-channel acousto-optic modulator 4 is 100%, and the light intensity at the waist of the first sub-beam is I 0 , where the light intensity of the white part is greater than 40% I 0 , so the white part can represent the expected size of the nanopillars to some extent. Figure 3 In (b), the power of the multi-channel AOM 4 drops to 80%, see Figure 3In (c), the power of the multi-channel AOM 4 drops to 60%. As the power of the multi-channel AOM 4 drops, the light intensity of the first sub-beam also drops, and the size of the white part also drops. This proves that the shape of the nanocolumn can be effectively adjusted by adjusting the light intensity of the first sub-beam. Similarly, the shape of the nanocolumn can also be effectively adjusted by adjusting the exposure time of the first sub-beam.

[0086] In some embodiments, λ =532nm, n ref =1.55nm, the distance between the focus and the focal plane of the first objective lens 6 is 3μm. Assume H = a H T + b H , 2 R=a R T + b R ,in a H =1.3×10 -7 , a R =9.7×10 -9 , b H =-7.2×10 -6 , b R = -2.5 × 10 -7 .

[0087] See also Figure 5 ,when P= 1.5μm and P= When the nanorod is 1 μm, the phase modulation range of the transmitted light can cover 2 π range, where P= At 1.5μm, the coverage is wider. T The value range only covers 55.4% S -98.4% S This range allows the nanopillars to cover 2 π phase change.

[0088] If we want to manufacture a metalens with the function of focusing a beam, its diameter is 450 μm, the focal length is 4 mm, and the required phase distribution on the XY cross section is as follows: Figure 6 As shown, T / S The numerical distribution of Figure 7 shown.

[0089] Embodiment 2:

[0090] See also Figure 8 This embodiment provides a laser direct writing device, which includes a first light source 1, a uniform light expansion component 8, a digital micromirror array 9, a microlens array 10, a first sleeve lens 5, a first objective lens 6 and a first writing platform 7 in the direction of light propagation.

[0091] The digital micromirror array 9 and the microlens array 10 form a beam splitting control module. Assume that the digital micromirror array 9 has 1920×1080 sub-micromirrors, and the sub-micromirror size is 10μm. 13×13 sub-micromirrors form a sub-region. Each sub-region corresponds to a second sub-beam. The number of sub-micromirrors turned on in each sub-region determines the diameter and light intensity of a single second sub-beam at the same time. Therefore, in this embodiment, for a single second sub-beam, its diameter and light intensity cannot be freely adjusted at the same time.

[0092] See also Fig. 9 , when the diameter of the second sub-beam is not less than 40 μm, the focal depth of the second sub-beam is almost unchanged. Therefore, as long as the diameter of each second sub-beam is not less than 40 μm, the focal depth of each second sub-beam at the photoresist can be equal or substantially equal, and the light intensity of each second sub-beam can be adjusted separately. On the contrary, as long as the diameter of each second sub-beam is less than 40 μm, the digital micromirror array 9 can not only make different second sub-beams have different focal depths, but also make different second sub-beams have different light intensities.

[0093] If the focal depths of the second sub-beams at the photoresist are substantially equal, then the difference between the maximum focal depth of the second sub-beams and the minimum focal depth of the second sub-beams is no greater than 1 μm.

[0094] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0095] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A laser direct writing method, characterized in that: Based on a laser direct writing device, the laser direct writing device comprises, in sequence in the direction of light path propagation, a first light source (1), an optical diffraction element (2), a multi-channel acousto-optic modulator (4), a first tube lens (5), a first objective lens (6) and a first writing platform (7); The optical diffraction element (2) is used to split the light beam emitted by the first light source (1) into at least two first sub-beams, the diameter of each of the first sub-beams is equal or substantially equal, and the diameter of the first sub-beams is smaller than the entrance pupil diameter of the first objective lens (6), and the multi-channel acousto-optic modulator (4) is used to adjust the light intensity of each of the first sub-beams; The laser direct writing method comprises: Before preparing the nanopillars, determine the designed height of the nanopillars H ; At least based on H , determining a target light intensity of the first sub-beam; The multi-channel acousto-optic modulator (4) adjusts the actual light intensity of the first sub-beam so that the actual light intensity of the first sub-beam matches the target light intensity; Using the first sub-beam after light intensity modulation to expose the corresponding position of the photoresist to obtain the nanorod; The laser direct writing method also includes: Obtain the beam quality factor of the first light source (1) M 2 , the first light source (1) corresponds to the emission wavelength λ , the equivalent focal length of the first objective lens (6) f And the designed focal depth of the first sub-beam is L ; At least based on M 2 , λ , f , L Determine the target diameter of the first sub-beam D ; The optical diffraction element (2) adjusts the actual diameter of the first sub-beam so that the actual diameter of the first sub-beam matches the target diameter. D ; The laser direct writing method also includes: Get the polymerization threshold of the photoresist S ; At least based on H , f、L and S Determine the target light intensity and target exposure time of the first sub-beam t ; The first light source (1) controls an actual exposure time of the first sub-beam so that the actual exposure time of the first sub-beam matches a target exposure time. t ; The laser direct writing method also includes: Before preparing nanopillars, determine the design radius of the nanopillars R ; At least based on R determining a target light intensity and a target exposure time of the first sub-beam; The laser direct writing method also includes: Before fabricating the nanorods, determine the designed phase modulation amount of the nanorods φ , refractive index of photoresist after curing n ref and the refractive index of air n 0; At least based on φ , λ, D, H Determine the target spacing between two adjacent nanopillars P ; The optical diffraction element (2) is based at least on P , n ref and n 0. adjusting the distance between two adjacent first sub-beams; in, , , , , ,in I 0 is the light intensity at the waist of the first sub-beam, w 0 is the radius of the light spot formed after the first sub-beam is focused by the first objective lens (6).

2. The laser direct writing method according to claim 1, characterized in that: The laser direct writing device further comprises a first lens (3), wherein the first lens (3) is located between the optical diffraction element (2) and the multi-channel acousto-optic modulator (4), and the first lens (3) is used to collimate the first sub-beam.

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