CN111562725B - Method for improving photoetching resolution ratio based on space-time cooperative transformation exposure - Google Patents
Method for improving photoetching resolution ratio based on space-time cooperative transformation exposure Download PDFInfo
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- CN111562725B CN111562725B CN202010502150.8A CN202010502150A CN111562725B CN 111562725 B CN111562725 B CN 111562725B CN 202010502150 A CN202010502150 A CN 202010502150A CN 111562725 B CN111562725 B CN 111562725B
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/20—Exposure; Apparatus therefor
- G03F7/2051—Exposure without an original mask, e.g. using a programmed deflection of a point source, by scanning, by drawing with a light beam, using an addressed light or corpuscular source
- G03F7/2057—Exposure without an original mask, e.g. using a programmed deflection of a point source, by scanning, by drawing with a light beam, using an addressed light or corpuscular source using an addressed light valve, e.g. a liquid crystal device
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70383—Direct write, i.e. pattern is written directly without the use of a mask by one or multiple beams
- G03F7/70391—Addressable array sources specially adapted to produce patterns, e.g. addressable LED arrays
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
- G03F7/70491—Information management, e.g. software; Active and passive control, e.g. details of controlling exposure processes or exposure tool monitoring processes
Abstract
The invention discloses a method for improving photoetching resolution ratio based on space-time cooperative transformation exposure, which relates to the field of DMD device imaging exposure and comprises the steps of cooperatively matching three dynamic quantities, namely platform micromotion, DMD graph transformation and exposure energy adjustment to form an exposure mode of space-time cooperative transformation to improve photoetching resolution ratio.
Description
Technical Field
The invention relates to the field of DMD device imaging exposure, in particular to a method for improving photoetching resolution based on space-time cooperative transformation exposure.
Background
The mask-free photoetching technology based on the DMD can produce a tiny, light and integrated three-dimensional microstructure device, improves the photoetching efficiency and precision, and reduces the photoetching cost. However, in the DMD maskless lithography system, a dynamic mask pattern is generated by controlling each micromirror to turn and then using a projection lens. Therefore, the resolution of the maskless lithography system is strictly limited by the size of the projected micromirror, and there is a non-integer pixel error, called DMD pixel quantization error, which will cause the sawtooth structure at the edge of the outline of the pattern to be written.
The existing technology for improving the photoetching resolution ratio is easy to realize for a photoetching system with large focal depth and low resolution ratio, and for a system with high resolution ratio and small focal depth ratio, real-time and quick fine focusing in the motion process is difficult to realize.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a method for improving the photoetching resolution ratio based on space-time cooperative transformation exposure.
The purpose of the invention is realized by the following technical scheme:
a method for improving photoetching resolution ratio based on space-time cooperative transformation exposure comprises the following steps:
and 3, placing the substrate on a micro-displacement platform, projecting the optical image in the step 2 onto the substrate coated with the photoresist in a spinning mode through a projection lens for exposure, controlling the micro-displacement platform to accurately move in a nanometer scale through a computer, and correspondingly moving the micro-displacement platform every time the DMD changes the image, and simultaneously controlling exposure energy to effectively smooth the edge of the image.
Preferably, said step 2 comprises the following sub-steps;
step 2.1, the DMD is composed of m multiplied by N micro-mirror arrays with the single pixel size of L, and the improvement multiple N of the graph resolution is determined according to the requirement of the graph edge smoothness;
step 2.2, quantizing the graph through CAD, wherein the size of a grid required by the quantized graph is (m × N) x (N × N);
and 2.3, generating a mask map by using matlab, and moving the grid.
Preferably, the step 3 comprises the following substeps:
step 3.1, determining the moving position of the micro-displacement platform;
step 3.2, determining the optimal exposure time of the subgraph, if the exposure time threshold of the quantized graph obtained by N =1 is T, because the subgraph 0 does not participate in superposition, the exposure time is T, and the optimal exposure time tp of the rest subgraphs:
t p ＝T/N
step 3.3, determining the final sub-image exposure time: the exposure time T of the sub-image 0 is unchanged, the exposure time T of the other sub-images is changed, and the relationship between the line width corresponding to different N values and the exposure time is explored;
and 3.4, carrying out piezoelectric movement once, loading a corresponding sub-graph and simultaneously controlling the exposure time.
Preferably, the step 3.3 of exploring the relationship between the line width and the exposure time corresponding to different N values includes the following sub-steps
Step 3.3.1, determining the relationship between the sub-image exposure time and the line width variation as follows:
Δt＝ΔDK N
step 3.3.2, analyzing the experimental results and determining K N
Step 3.3.3, determining the exposure time t of the final subgraph of the graph:
t＝t p +Δt＝T/N+(D-d theory of the invention )K N
And 3.3.4, setting the exposure time of the subgraph 0 as T, and setting the exposure time of the rest subgraphs as T.
Preferably, the DMD is comprised of a 1024 x 768 micro-mirror array with a single pixel size of 13.68 μm.
Preferably, the rule for moving the grid includes the following,
selecting an area where the quantized graph and the grid are overlapped every time the grid moves once;
when the grid does not move, namely the grid is in the original position, the overlapping area needs to be divided into a part which does not participate in dislocation and an edge part (respectively marked as subgraph 0 and 1);
the grid only retains the edge portions of the overlapping area when moved to other locations.
Preferably, the micro displacement platform is a piezoelectric platform.
Preferably, the photoresist has a thickness of 1 μm.
The invention has the beneficial effects that:
the invention relates to a method for improving photoetching resolution by an exposure mode of space-time cooperative transformation, which is characterized in that three dynamic quantities of platform micromotion, DMD graph transformation and exposure energy adjustment are cooperatively matched. By applying the spatio-temporal cooperative transformation technique to DMD projection lithography, the edge smoothness of the lithographic pattern can be significantly improved without reducing the DMD micromirror size or the projection lens magnification. Meanwhile, the method is an effective method for experimental equipment which cannot adjust the focus in real time or improve the photoetching resolution by adjusting the rotation angle of the platform. Compared with non-subgraph superposition lithography, the method has the advantages that the CAD is used for quantifying the graph, subgraphs are extracted by using matlab, exposure energy is controlled simultaneously by combining micro displacement of the piezoelectric platform to carry out subgraph dislocation superposition exposure, smoothness of the edge of the photoetched graph is improved, and meanwhile the line width of the graph can be accurately controlled. The DMD photoetching method based on the space-time cooperative transformation technology is verified, and the method is very effective for improving the smoothness of any photoetching graph edge in a static exposure mode.
Drawings
FIG. 1 is a schematic view of an experimental apparatus according to the present invention;
FIG. 2 is a schematic diagram of a basic strategy based on a spatio-temporal collaborative transformation technique;
FIG. 3 is a specific example of a basic strategy based on spatio-temporal cooperative transformation technique;
FIG. 4 is a graph of the spiral raw mask;
FIG. 5 is a graph of the results of a lithography based on spatio-temporal co-transformation technique.
Detailed Description
The technical solutions of the present invention are further described in detail below with reference to the accompanying drawings, but the scope of the present invention is not limited to the following descriptions.
A method for improving photoetching resolution based on space-time cooperative transformation exposure comprises the following steps:
it should be noted that the micro displacement platform is a piezoelectric platform.
Wherein the thickness of the photoresist is 1 μm.
wherein the step 2 comprises the following substeps;
step 2.1, the DMD is composed of m multiplied by N micro-mirror arrays with the single pixel size of L, and the improvement multiple N of the graph resolution is determined according to the requirement of the graph edge smoothness;
step 2.2, quantizing the graph through CAD, wherein the size of a grid required by the quantized graph is (m × N) x (N × N);
step 2.3, generating a mask graph by using matlab, moving the grid,
wherein the rule for the grid to move comprises the following,
selecting an area where the quantized graph and the grid are overlapped every time the grid moves once;
when the grid does not move, namely the grid is in the original position, the overlapping area needs to be divided into a part which does not participate in dislocation and an edge part (respectively marked as subgraph 0 and 1);
the grid only retains the edge portions of the overlapping area when moved to other locations.
And 3, placing the substrate on a micro-displacement platform, projecting the light image in the step 2 on the substrate coated with the photoresist by a projection lens to expose, and simultaneously controlling the micro-displacement platform to accurately move in a nanometer scale by a computer, wherein the micro-displacement platform also moves correspondingly when the DMD changes the picture once, and simultaneously controls exposure energy to effectively smooth the edge of the picture.
Wherein the step 3 comprises the following substeps:
step 3.1, determining the moving position of the micro-displacement platform;
step 3.2, determining the optimal exposure time of the subgraph, setting the exposure time threshold of the quantized graph obtained by N =1 as T, wherein the exposure time is T because the subgraph 0 does not participate in superposition, and the optimal exposure time tp of the rest subgraphs:
t p ＝T/N
step 3.3, determining the final sub-image exposure time: the exposure time T of the sub-image 0 is unchanged, the exposure time T of the other sub-images is changed, and the relationship between the line width corresponding to different N values and the exposure time is explored;
and 3.4, carrying out piezoelectric movement once, loading a corresponding sub-graph, and controlling the exposure time.
Wherein, the step 3.3 of researching the relationship between the line width and the exposure time corresponding to different N values comprises the following substeps
Step 3.3.1, determining the relationship between the sub-image exposure time and the line width variation as follows:
Δt＝ΔDK N
step 3.3.2, analyzing the experimental results and determining K N
Step 3.3.3, determining the final subgraph exposure time t of the graph:
t＝t p +Δt＝T/N+(D-d theory of the invention )K N
And 3.3.4, setting the exposure time of the sub-image 0 as T, and setting the exposure time of the rest sub-images as T.
Note that the DMD is composed of 1024 × 768 micromirror arrays each having a single pixel size of 13.68 μm.
In summary, the basic strategy of the spatio-temporal collaborative transformation technology is as follows: the N value can be determined according to the requirement of graph edge smoothing, and then the sub-graph mode, the platform moving mode and the sub-graph optimal exposure time tp are determined according to the N value. Finally determining sub-graph exposure time according to the line width requirement of the photoetching graph, obtaining the photoetching graph consistent with the expected graph line width, wherein edge sawteeth also meet the target requirement, and the specific experimental parameters are shown in table 1:
in order to verify the feasibility of the spatio-temporal collaborative transformation technology, a complex graph dislocation superposition experiment needs to be further performed, as shown in fig. 4, a spiral line is used as an original graph, and a multiple exposure experiment is performed on the original graph to obtain an original mask graph exposure time threshold T =6s. The feasibility of this method was verified by experimentally making a complex spiral structure that accurately controlled the edge serration size and line width, first determining the specific requirements for the lithographic results, as shown in table 2,
and then obtaining corresponding experimental parameters according to a basic strategy of a space-time cooperative transformation technology.
According to the parameters of table 2:
(1) quantification of original drawings by CAD
(2) Determining subgraphs when N is 2 and 4 by matlab,
(3) determining the corresponding piezoelectric platform moving position according to the subgraph,
(4) the subgraph exposure time in the parameter table is adopted for carrying out the experiment, and the experimental result is shown in figure 5.
And finally, analyzing an experimental result: as can be seen from Table 3, the pattern line width is consistent with the target required line width, and the error is within 0.1 μm. And comparing the sawtooth theoretical value with the actual measured value, wherein the sawtooth theoretical value and the actual measured value are consistent.
The foregoing is merely a preferred embodiment of the invention, it being understood that the embodiments described are part of the invention, and not all of it. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. The invention is not intended to be limited to the forms disclosed herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (5)
1. A method for improving photoetching resolution ratio based on space-time cooperative transformation exposure is characterized by comprising the following steps:
step 1, configuring a DMD digital photoetching system, wherein the DMD digital photoetching system comprises an LED light source, a DMD, a tube lens, a beam splitter prism, a reflector, a projection lens, a CCD camera and a micro-displacement platform, light emitted by the LED light source is irradiated on the DMD and reflected after being collimated and homogenized, and then enters the projection lens after passing through the tube lens, the beam splitter prism and the reflector;
step 2, inputting the photoetching pattern to the DMD through a pattern generator by a computer, and turning each micromirror of the DMD by +12 degrees and-12 degrees so as to form a light image consistent with a required pattern on an image surface of the projection lens;
step 3, placing the substrate on a micro-displacement platform, projecting the optical image in the step 2 onto the substrate which is coated with photoresist in a spinning mode through a projection lens for exposure, controlling the micro-displacement platform to accurately move in a nanometer scale through a computer, and controlling exposure energy and effectively smoothing the edge of the graph, wherein the micro-displacement platform also moves correspondingly every time the DMD changes the picture;
the step 2 includes the following substeps;
step 2.1, the DMD is composed of m multiplied by N micro-mirror arrays with the single pixel size of L, and the improvement multiple N of the pattern resolution is determined according to the requirement of the smoothness of the pattern edge;
step 2.2, quantizing the graph through CAD, wherein the size of a grid required by the quantized graph is (m × N) x (N × N);
step 2.3, generating a mask map by using matlab, and moving the grid;
the step 3 comprises the following substeps:
step 3.1, determining the moving position of the micro-displacement platform;
step 3.2, determining the optimal exposure time of the subgraph, setting the exposure time threshold of the quantized graph obtained by N =1 as T, wherein the exposure time is T because the subgraph 0 does not participate in superposition, and the optimal exposure time tp of the rest subgraphs:
t p ＝T/N
step 3.3, determining the final sub-image exposure time: the exposure time T of the sub-image 0 is unchanged, the exposure time T of the other sub-images is changed, and the relationship between the line width corresponding to different N values and the exposure time is explored;
step 3.4, piezoelectric movement is carried out once, corresponding sub-graphs are loaded, and meanwhile exposure time is controlled;
the step 3.3 of exploring the relationship between the line width and the exposure time corresponding to different N values includes the following substeps
Step 3.3.1, determining the relationship between the sub-image exposure time and the line width variation as follows:
Δt＝ΔDK N
step 3.3.2, analyzing the experimental results and determining K N
Step 3.3.3, determining the exposure time t of the final subgraph of the graph:
t＝t p +Δt＝T/N+(D-d theory of the invention )K N
And 3.3.4, setting the exposure time of the subgraph 0 as T, and setting the exposure time of the rest subgraphs as T.
2. The method for improving the resolution of lithography based on spatio-temporal cooperative transform exposure according to claim 1, wherein the DMD is composed of 1024 x 768 micromirror arrays with a single pixel size of 13.68 μm.
3. The method for improving the lithography resolution based on the spatio-temporal cooperative transform exposure according to claim 2, wherein the rule for moving the grid comprises the following contents,
selecting an area where the quantized graph and the grid are overlapped every time the grid moves once;
when the grids do not move, namely when the grids are in the original positions, the overlapping area needs to be divided into a part which does not participate in dislocation and an edge part (respectively marked as subgraph 0 and 1);
the grid only retains the edge portions of the overlapping regions when moved to other locations.
4. The method for improving lithography resolution based on spatio-temporal cooperative transform exposure according to claim 1, wherein the micro-displacement stage is a piezoelectric stage.
5. The method for improving the lithography resolution based on the spatio-temporal cooperative transformation exposure according to claim 1, wherein the thickness of the photoresist is 1 μm.
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| CN101317133A (en) * | 2005-05-02 | 2008-12-03 | 拉多韦有限公司 | Lithographic method for maskless pattern transfer onto a photosensitive substrate |
| CN107908077A (en) * | 2017-10-30 | 2018-04-13 | 中国科学技术大学 | Rotary exposure system and method based on Digital Micromirror Device mask-free photolithography |
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| US6707534B2 (en) * | 2002-05-10 | 2004-03-16 | Anvik Corporation | Maskless conformable lithography |
| US9561622B2 (en) * | 2008-05-05 | 2017-02-07 | Georgia Tech Research Corporation | Systems and methods for fabricating three-dimensional objects |
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| CN101317133A (en) * | 2005-05-02 | 2008-12-03 | 拉多韦有限公司 | Lithographic method for maskless pattern transfer onto a photosensitive substrate |
| CN107908077A (en) * | 2017-10-30 | 2018-04-13 | 中国科学技术大学 | Rotary exposure system and method based on Digital Micromirror Device mask-free photolithography |
| CN109774128A (en) * | 2019-03-13 | 2019-05-21 | 东北师范大学 | Photoetching and printing integratedization equipment and its construction method based on DMD |
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