A method for making linewidth modulatable submicron grating using digital mask

Abstract

The invention discloses a method for manufacturing a submicron grating with modulated line width by using a digital mask. The method matches the misalignment of two SLMs in a digital lithography system and the design of a grating lithography mask sub-image, sequentially and simultaneously distributes the pre-designed grating lithography mask sub-image to SLM1 and SLM2 with misaligned configuration for display, and controls SLM1 and SLM2 by a computer to sequentially and simultaneously project the grating lithography mask sub-image at the same position on a substrate coated with photoresist according to a pre-set exposure time, and performs multiple superimposed exposures to form different misaligned superimposed exposure amounts, thereby realizing the manufacturing of the submicron grating with modulated line width. The invention fully utilizes the significant advantage of digital mask lithography in fast and accurate projection of graphics, and avoids repeated positioning errors introduced by repeated scanning of a piezoelectric platform and the resulting reduction in processing efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of manufacturing submicron gratings, and in particular to a method for manufacturing linewidth modulated submicron gratings by using a digital mask. Background Art

[0002] As the core dispersive optical element of optical instruments, gratings are widely used in metrology, optical communication, aviation, aerospace, laser energy modulation and other fields. In recent years, linewidth modulated submicron gratings have shown broad application prospects in spatial spectrometers, optical fiber communications, aspheric interferometry, plasma diagnosis and other fields due to their unique advantages such as self-focusing, aberration correction and high resolution.

[0003] The main methods for making submicron gratings with modulated line width include electron beam exposure, holographic exposure and nanoimprinting. Electron beam exposure has the disadvantages of high cost and difficult to control exposure parameters. The grating spectrum obtained by holographic exposure has a wide range and high resolution, but the process requirements are very high. Nanoimprinting can replicate the graphics on the template with high precision, and its difficulty lies in the control of imprinting parameters. In recent years, digital mask lithography based on digital micromirror devices (DMD) has been widely used in the manufacture of functional microstructures due to its significant advantages such as high efficiency and low cost. However, due to unfavorable factors such as the non-monochromaticity of the lithography light source and the mutual interference between the diffraction of the DMD micromirrors, its resolution is limited to the micron level. Although the resolution of digital mask lithography can be further improved by linking a single SLM and a high-precision piezoelectric platform scanning, the multiple scanning processes of the piezoelectric platform will lead to a decrease in processing efficiency. At the same time, as the precision of the piezoelectric platform increases, its price rises sharply, thereby increasing the production cost. In order to overcome the defects of existing methods for producing submicron gratings with modulated line width, such as high cost and difficult to control process parameters, a method for producing submicron gratings with modulated line width using digital masks was proposed, taking full advantage of the significant advantages of digital mask lithography in fast and accurate projection of patterns. Summary of the invention

[0004] The purpose of the present invention is to solve the technical problems existing in the prior art and provide a method for making a line width modulated submicron grating using a digital mask. To achieve the above purpose, the technical solution provided by the present invention is: a method for making a line width modulated submicron grating using a digital mask, the method comprising the following steps:

[0005] (1) A digital lithography system is configured, wherein the digital lithography system includes exposure light sources 1 and 2, reflectors 1 and 2, SLMs 1 and 2, beam splitters 1 and 2, a projection objective lens, and a precision moving stage; light emitted by the exposure light source 1 is reflected by the reflector 1, incident on the SLM 1 at a fixed angle, and then modulated by the SLM 1 before entering the beam splitter 1; light emitted by the exposure light source 2 is reflected by the reflector 2, incident on the SLM 2 at a fixed angle, and then modulated by the SLM 2; light modulated by the SLM 1 and the SLM 2 is coupled by the beam splitter 2, and reaches a substrate mounted on the precision moving stage through the projection objective lens, thereby realizing combined superposition exposure of different SLMs; if the size of the image projected by one pixel of the SLM 1 and the SLM 2 through the projection objective lens is T x ×T y , configure the spatial positions of SLM1 and SLM2 so that the two images projected onto the substrate are displaced in two directions parallel to the substrate plane, and the displaced distances are n is a natural number.

[0006] (2) Using Matlab to pre-design n+1 grating lithography mask sub-images, the grating lithography mask sub-images are assigned to SLM1 and SLM2 for display in turn, and SLM1 and SLM2 are controlled by a computer to project the grating lithography mask sub-images at the same position on the photoresist-coated substrate in turn according to the pre-set exposure time for n+1 superimposed exposures.

[0007] (3) After developing, fixing, post-baking and other processes, a line width of Modulatable submicron grating lithography patterns.

[0008] Preferably, the misalignment in step (1) means that the positions of the graphics projected by SLM1 and SLM2 onto the substrate do not correspond one-to-one to the same position of the substrate, and the misalignment includes misalignment in all directions parallel to the substrate plane.

[0009] Preferably, the step (2) of pre-designing n+1 grating lithography mask sub-images using Matlab comprises the following steps:

[0010] Step 2.1: When the SLM pixel size is W x ×W y When the line width is W x , cycle is 2W x The binary grating pattern 1 is periodically tiled along the x direction and the generated line width is W y , cycle is 2W y A binary grating pattern 2 arranged periodically in a tiled pattern along the y direction;

[0011] Step 2.2 ORs the binary grating pattern 1 and the binary grating pattern 2 generated in step 2.1 to obtain a grating lithography mask. Figure 1 ;

[0012] Step 2.3: Place the grating photolithography mask Figure 1 Displacement in two directions at the same time distance, k=1,2,3,…,and k≤n,get the grating lithography mask Figure 2 , Grating Lithography Mask Figure 3 ,…,grating lithography mask sub-image n+1.

[0013] Preferably, the photoresist in step (3) includes positive or negative photoresist used for photolithography.

[0014] Beneficial effects of the present invention:

[0015] The present invention forms different offset superimposed exposure amounts on a substrate by staggered projection of a pre-designed grating lithography mask sub-image by two SLMs, thereby realizing the production of a submicron grating with modulated line width and making full use of the significant advantages of digital mask lithography in fast and accurate projection of images, avoiding repeated positioning errors introduced by repeated scanning of the piezoelectric platform and the resulting decrease in processing efficiency; the absence of a static mask can greatly reduce the cost of mask production, thereby effectively reducing the production cost of digital mask lithography. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings described herein are used to provide further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0017] Figure 1 is a schematic diagram of a digital lithography system of the present invention;

[0018] Figure 2 A schematic diagram of manufacturing a sub-micron grating by staggered superposition of two grating lithography mask sub-patterns of the present invention;

[0019] Figure 3 The schematic diagram of the present invention is to produce a submicron grating by staggered superposition of three grating lithography mask sub-patterns. DETAILED DESCRIPTION

[0020] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it cannot be understood as a limitation on the scope of protection of the present invention.

[0021] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are 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 device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0022] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0023] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0024] Example 1

[0025] Reference Figure 1 and Figure 2 , a method for making a linewidth modulated submicron grating using a digital mask, comprising the following steps:

[0026] (1) Configure a digital lithography system, such as Figure 1 As shown, the digital lithography system includes exposure light sources 1 and 2, reflectors 1 and 2, SLM1 and SLM2, beam splitters 1 and 2, projection objective lenses, and precision moving stages; preferably, the exposure light sources 1 and 2 can be LED light sources, laser light sources, mercury lamp light sources, etc.; the SLM1 and SLM2 can be spatial light modulators such as digital micromirror devices (DMDs), liquid crystals (LCDs), and liquid crystal on silicon (LCOS), etc., refer to Figure 1 , Figure 1In the embodiment, both SLM1 and SLM2 are DMDs, and the DMDs are composed of a micromirror array with a single pixel size of 13.68 μm×13.68 μm; the light emitted by the exposure light source 1 is reflected by the reflector 1, incident on the DMD1 at a fixed angle, and modulated by the DMD1 before entering the beam splitter 1; the light emitted by the exposure light source 2 is reflected by the reflector 2, incident on the DMD2 at a fixed angle, and modulated by the DMD2; the modulated light of DMD1 and DMD2 is coupled by the beam splitter 2 and reaches the substrate mounted on the precision moving stage through the projection objective lens, so as to realize the combined superposition exposure of different DMDs, and preferably, the reduction ratio of the projection objective lens is 20 times; if the size of the image projected by the projection objective lens for one pixel of DMD1 and DMD2 is T x ×T y , configure the spatial positions of DMD1 and DMD2 so that the two graphics projected onto the substrate are displaced in the x and y directions parallel to the substrate plane, and the dislocation distances are

[0027] (2) Using Matlab to pre-design two grating lithography mask sub-images, including the following sub-steps:

[0028] Step 2.1 When the SLM pixel size is W x ×W y When the line width is W x , cycle is 2W x The binary grating pattern 1 is periodically tiled along the x direction and the generated line width is W y , cycle is 2W y A binary grating pattern 2 arranged periodically in a tiled pattern along the y direction;

[0029] Step 2.2 ORs the binary grating pattern 1 and the binary grating pattern 2 generated in step 2.1 to obtain a grating lithography mask. Figure 1 ;

[0030] Step 2.3: Place the grating on the photolithography mask Figure 1 At the same time, the displacement W in the x and y directions is x , W y distance, and obtain the grating lithography mask Figure 2 .

[0031] Grating lithography mask Figure 1 The display is assigned to DMD1 and DMD2 at the same time, and the computer controls DMD1 and DMD2 to project the grating lithography mask at the same time according to the preset exposure time. Figure 1 The first superposition exposure is performed at the same position on the substrate coated with photoresist; then the grating photolithography mask is Figure 2The display is assigned to DMD1 and DMD2 at the same time, and the computer controls DMD1 and DMD2 to project the grating lithography mask at the same time according to the preset exposure time. Figure 2 A second overlay exposure is performed at the same location on the photoresist-coated substrate.

[0032] (3) After developing, fixing, post-baking and other processes, a line width of Modulatable submicron grating lithography patterns.

[0033] In Example 1, the size of the image projected by one pixel of DMD1 and DMD2 through the projection objective lens is x ×T y It is 0.684μm×0.684μm. After development, fixing, post-baking and other processes, a line width can be formed on the photoresist. It is a sub-micron grating lithography pattern of 0.484μm.

[0034] Example 2

[0035] Reference Figure 1 and Figure 3 , a method for making a linewidth modulated submicron grating using a digital mask, comprising the following steps:

[0036] (1) Configure a digital lithography system, such as Figure 1 As shown, the digital lithography system includes exposure light sources 1 and 2, reflectors 1 and 2, SLM1 and SLM2, beam splitters 1 and 2, projection objective lenses, and precision moving stages; preferably, the exposure light sources 1 and 2 can be LED light sources, laser light sources, mercury lamp light sources, etc.; the SLM1 and SLM2 can be spatial light modulators such as digital micromirror devices (DMDs), liquid crystals (LCDs), and liquid crystal on silicon (LCOS); preferably, Figure 1 In the embodiment, both SLM1 and SLM2 are DMDs, and the DMDs are composed of a micromirror array with a single pixel size of 13.68 μm×13.68 μm; the light emitted by the exposure light source 1 is reflected by the reflector 1, incident on the DMD1 at a fixed angle, and modulated by the DMD1 before entering the beam splitter 1; the light emitted by the exposure light source 2 is reflected by the reflector 2, incident on the DMD2 at a fixed angle, and modulated by the DMD2; the modulated light of DMD1 and DMD2 is coupled by the beam splitter 2 and reaches the substrate mounted on the precision moving stage through the projection objective lens, so as to realize the combined superposition exposure of different DMDs, and preferably, the reduction ratio of the projection objective lens is 20 times; if the size of the image projected by the projection objective lens for one pixel of DMD1 and DMD2 is T x ×T y, configure the spatial positions of DMD1 and DMD2 so that the two graphics projected onto the substrate are displaced in the x and y directions parallel to the substrate plane, and the dislocation distances are

[0037] (2) Using Matlab to pre-design three grating lithography mask sub-images, including the following sub-steps:

[0038] Step 2.1 When the SLM pixel size is W x ×W y When the line width is W x , cycle is 2W x The binary grating pattern 1 is periodically tiled along the x direction and the generated line width is W y , cycle is 2W y A binary grating pattern 2 arranged periodically in a tiled pattern along the y direction;

[0039] Step 2.2 ORs the binary grating pattern 1 and the binary grating pattern 2 generated in step 2.1 to obtain a grating lithography mask. Figure 1 ;

[0040] Step 2.3: Place the grating on the photolithography mask Figure 1 At the same time, the displacement in the x and y directions is distance, and obtain the grating lithography mask Figure 2 ; Place the grating lithography mask Figure 1 At the same time, the displacement in the x and y directions is distance, and obtain the grating lithography mask Figure 3 .

[0041] Grating lithography mask Figure 1 The display is assigned to DMD1 and DMD2 at the same time, and the computer controls DMD1 and DMD2 to project the grating lithography mask at the same time according to the preset exposure time. Figure 1 The first overlay exposure is performed at the same position on the photoresist-coated substrate; the grating photolithography mask is Figure 2 The display is assigned to DMD1 and DMD2 at the same time, and the computer controls DMD1 and DMD2 to project the grating lithography mask at the same time according to the preset exposure time. Figure 2 A second superimposed exposure is performed at the same position on the photoresist-coated substrate; and then the grating photolithography mask is Figure 3 The display is assigned to DMD1 and DMD2 at the same time, and the computer controls DMD1 and DMD2 to project the grating lithography mask at the same time according to the preset exposure time. Figure 3 A third overlay exposure is performed at the same location on the photoresist-coated substrate.

[0042] (3) After developing, fixing, post-baking and other processes, a line width of Modulatable submicron grating lithography patterns.

[0043] In Example 2, the size of the image projected by one pixel of DMD1 and DMD2 through the projection objective lens is T x ×T y It is 0.684μm×0.684μm. After development, fixing, post-baking and other processes, a line width can be formed on the photoresist. It is a sub-micron grating lithography pattern of 0.322μm.

[0044] As a preferred embodiment of the present invention, it may also have the following additional technical features:

[0045] In Example 1 and Example 2, the misalignment means that the positions of the graphics projected by the two DMDs onto the substrate do not correspond one-to-one to the same position of the substrate, and the misalignment includes misalignment in all directions parallel to the substrate plane.

[0046] In Example 1 and Example 2, the photoresist includes a positive or negative photoresist used for photolithography.

[0047] The present invention forms different offset superimposed exposure amounts on a substrate by staggered projection of a pre-designed grating lithography mask sub-image by two SLMs, thereby realizing the production of a submicron grating with modulated line width and making full use of the significant advantages of digital mask lithography in fast and accurate projection of images, avoiding repeated positioning errors introduced by repeated scanning of the piezoelectric platform and the resulting decrease in processing efficiency; the absence of a static mask can greatly reduce the cost of mask production, thereby effectively reducing the production cost of digital mask lithography.

[0048] Under the premise that no conflict occurs, those skilled in the art may freely combine and superimpose the above-mentioned additional technical features.

[0049] The above description is only a preferred implementation mode of the present invention. Any technical solution that achieves the purpose of the present invention by substantially the same means belongs to the protection scope of the present invention.

Claims

1. A method for producing a linewidth modulatable submicron grating using a digital mask, characterized in that: The method comprises the following steps: (1) A digital lithography system is configured, wherein the digital lithography system includes exposure light sources 1 and 2, reflectors 1 and 2, SLM1 and SLM2, beam splitters 1 and 2, a projection objective lens, and a precision moving stage; light emitted by the exposure light source 1 is reflected by the reflector 1, incident on SLM1 at a fixed angle, and then modulated by SLM1 before entering the beam splitter 1; light emitted by the exposure light source 2 is reflected by the reflector 2, incident on SLM2 at a fixed angle, and then modulated by SLM2; light modulated by SLM1 and SLM2 is coupled by the beam splitter 2 and reaches a substrate mounted on the precision moving stage through the projection objective lens, thereby realizing superimposed exposure of different SLM combinations; if the size of images projected by a pixel of SLM1 and SLM2 through the projection objective lens is both Tx×Ty, and the reduction ratio of the projection objective lens is 20 times, the spatial positions of SLM1 and SLM2 are configured so that the two images projected onto the substrate are displaced in two directions parallel to the substrate plane, and the displaced distances are respectively n is a natural number; the misalignment means that the positions of the graphics projected by SLM1 and SLM2 onto the substrate do not correspond one-to-one to the same position of the substrate, and the misalignment includes misalignment in all directions parallel to the substrate plane; (2) using Matlab to pre-design n+1 grating lithography mask sub-images, and sequentially assigning the grating lithography mask sub-images to SLM1 and SLM2 for display, and controlling SLM1 and SLM2 by computer to sequentially and simultaneously project the grating lithography mask sub-images at the same position on the photoresist-coated substrate according to a pre-set exposure time for n+1 superimposed exposures; (3) After development, fixing, and post-baking processes, a line width of Modulatable submicron grating lithography patterns.

2. A method for producing a linewidth modulated submicron grating using a digital mask according to claim 1, characterized in that : In step (2), using Matlab to pre-design n+1 grating lithography mask sub-images includes the following steps: Step 2.1 When the SLM pixel size is Wx×Wy, a binary grating pattern 1 with a line width of Wx and a period of 2Wx and a periodic arrangement of tiles along the x direction is generated, and a binary grating pattern 2 with a line width of Wy and a period of 2Wy and a periodic arrangement of tiles along the y direction is generated; Step 2.2 performs an OR operation on the binary grating pattern 1 and the binary grating pattern 2 generated in step 2.1 to obtain a grating lithography mask sub-image 1; Step 2.3 Sequentially displace the grating lithography mask sub-image 1 in two directions simultaneously Distance, k = 1, 2, 3, ..., and k ≤ n, obtain grating lithography mask sub-image 2, grating lithography mask sub-image 3, ..., grating lithography mask sub-image n+1.

3. The method for producing a linewidth modulated submicron grating using a digital mask according to claim 1, characterized in that : The photoresist in step (3) includes positive or negative photoresist used for photolithography.

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