Manufacturing method of depth change type grating for terahertz wave band

Abstract

The invention provides a manufacturing method of a depth change type grating for a terahertz wave band. The manufacturing method comprises the following steps: coating one side of a substrate with a photoresist layer; a layer of mask is arranged on the face, away from the substrate, of the photoresist layer, the mask comprises a mask pattern corresponding to a depth change type grating, the mask pattern comprises a hollowed-out area and a covering area which are arranged at intervals, and the hollowed-out area corresponds to one grating so that the photoresist can be exposed; a shading plate is arranged on the side, provided with the mask, of the substrate; the shading plate is moved according to the preset direction and the preset speed, the photoresist covering the hollowed-out area is exposed in sequence to obtain an exposure area, and the preset speed is set according to the depth of each grating; and after the photoresist layer is exposed, carrying out developing treatment on the exposure area to obtain the depth change type grating. The depth change type grating can be obtained by controlling the exposure amount of the photoresist through the shading plate, so that the manufacturing cost can be reduced, the process is simplified, and the application range of the depth change type grating is widened.

Description

Technical Field

[0001] The present application relates to the field of gratings, and in particular to a method for manufacturing a depth-varying grating in the terahertz band. Background Art

[0002] A grating is an optical device consisting of a large number of parallel slits of equal width and spacing. When electromagnetic waves propagate on the surface of a good conductor with sub-wavelength periodic etched patterns, the electromagnetic waves are regulated to transmit in a form similar to surface waves induced by collective oscillation of carriers, thus forming surface plasmon-like transmission.

[0003] In the prior art, depth-varying gratings are generally prepared by precision machining or complex electron beam exposure processes. However, the production method of such depth-varying gratings is costly and complex, making it difficult to apply on a large scale. Summary of the invention

[0004] In view of this, the present application provides a method for manufacturing a depth-variant grating for the terahertz band, so as to reduce the manufacturing cost, simplify the process, and increase the application scope of the depth-variant grating.

[0005] The present application provides a method for manufacturing a depth-varying grating for a terahertz band, the method comprising: a method for manufacturing a depth-varying grating for a terahertz band, the depth-varying grating comprising a plurality of continuous gratings of different depths, characterized in that the method comprises: coating a photoresist layer on one side of a substrate; arranging a mask layer on a side of the photoresist layer away from the substrate, the mask comprising a mask pattern corresponding to the depth-varying grating, the mask pattern comprising a hollow area and a covering area arranged at intervals, the hollow area corresponding to a grating to expose the photoresist; arranging a light shielding plate on a side of the substrate where the mask is arranged; moving the light shielding plate according to a preset direction and a preset speed so that the photoresist covered by the hollow area is sequentially exposed to obtain an exposure area, the preset speed being set according to the depth of each grating; after the photoresist layer is exposed, developing the exposure area to obtain the depth-varying grating.

[0006] The present application described above can obtain a depth-variable grating by controlling the moving direction and preset speed of the light shielding plate to change the exposure amount of the photoresist, thereby reducing the manufacturing cost, simplifying the process, and increasing the application range of the depth-variable grating. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0008] Figure 1 A schematic diagram of the manufacturing process of the grating structure provided in the first embodiment of the present application.

[0009] Figure 2 A schematic diagram of a mask provided in an embodiment of the present application.

[0010] Figure 3 The grating structure provided in the embodiment of the present application includes the structural schematic diagram of the depth-variant grating for the terahertz band provided in the first example.

[0011] Figure 4 A schematic flow chart of a method for manufacturing a depth-variable grating for the terahertz band provided in an embodiment of the present application.

[0012] Figure 5 A schematic diagram of the depth-varying grating manufacturing process provided in the first embodiment of the present application.

[0013] Figure 6 A schematic diagram of the depth-varying grating manufacturing process provided in the second embodiment of the present application.

[0014] Figure 7 A schematic diagram of the depth-varying grating manufacturing process provided in the third embodiment of the present application.

[0015] Figure 8 A schematic diagram of a depth-varying grating structure provided in the third embodiment of the present application.

[0016] Fig. 9 A schematic structural diagram of a vertically symmetrical depth-varying grating provided in an embodiment of the present application.

[0017] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0019] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of this application and the above-mentioned drawings are used to distinguish similar planning objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate. In other words, the described embodiments are implemented according to an order other than that illustrated or described herein. In addition, the terms "including" and "having" and any of their variations may also include other content. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to only those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0020] It should be noted that the descriptions involving "first", "second", etc. in this application are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0021] Please see Figure 1-3 , the first embodiment of the present application provides a grating structure 300, which includes a depth-varying grating 100 for the terahertz band. The depth-varying grating 100 includes continuous gratings of different depths. In the present embodiment, the depth-varying grating 100 includes a structure in which gaps and gratings are alternately arranged, and the depths of the gratings are not consistent, and the widths of the gaps are the same, and the widths of the gratings are the same. It can be understood that in the present embodiment, a grating structure 300 is shown, which uses a part of the depth-varying grating 100 and a part of the depth-same grating structure 200; and in some other feasible embodiments, the grating structure 300 can be all depth-varying gratings 100. The following only describes the method for manufacturing the depth-varying grating 100, and the depth-same grating structure 200 can be implemented by any existing manufacturing method, which is not described or limited here.

[0022] Please refer to Figure 4-Figure 5 The method for manufacturing the depth-varying grating 100 includes steps S100 to S500.

[0023] Step S100 , coating a photoresist layer 2 on the surface of the substrate 1 .

[0024] Specifically, the substrate 1 is made of materials such as silicon, quartz, and copper, and the substrate 1 is used to provide an attachment platform for the photoresist layer 2. Specifically, before applying the photoresist layer 2, the substrate 1 is first cleaned to ensure that there is no dust and oil on the surface of the substrate 1; then the photoresist is evenly applied to the cleaned surface of the substrate 1.

[0025] Please see again Figure 2 In the present embodiment, the photoresist layer 2 adopts negative photoresist. The coating thickness of the photoresist is set according to the depth of the depth-varying grating 100, that is, the thickness of the photoresist layer 2 corresponding to the position of the grating at different depths is different. Among them, the side of the photoresist layer 2 facing away from the substrate 1 is a flat surface. The thickness of the substrate 1 is different according to the different depths of the grating corresponding to the photoresist layer 2, so that the photoresist layer 2 has different thicknesses. In the present embodiment, the depth-varying grating 100 is a gradient grating, therefore, a substrate 1 and a photoresist layer 2 with a gradient thickness are used, that is, the depth of the grating gradually becomes shallower or deeper, the photoresist layer 2 gradually becomes thinner or thicker, and the substrate 1 gradually becomes thicker or thinner. The substrate 1 is made by mechanical processing and can be milled out by a milling machine.

[0026] It is understandable that in some feasible embodiments, the substrates may be set to have the same thickness, and the thickness of the photoresist layer may be set according to the depth of the depth-variable grating 100. In this case, the side of the photoresist layer 2 facing away from the substrate 1 is a gradually inclined surface.

[0027] Step S200 , disposing a mask 5 on a side of the photoresist layer 2 facing away from the substrate 1 .

[0028] like Figure 2 As shown, specifically, the mask 5 includes a mask pattern 51 corresponding to the depth-varying grating, and the mask pattern 51 includes hollow areas 510 and covering areas 512 that are spaced apart. The hollow area 510 corresponds to a grating, so that the position corresponding to the photoresist layer 2 and the hollow area 510 is exposed, that is, the photoresist layer 2 is exposed through the hollow area 510 intervals.

[0029] Step S300, a light shielding plate 3 is arranged on the photoresist layer 2. In the present embodiment, the number of the light shielding plate 3 is 1, and the size thereof matches the size of the depth-variable grating 100, so that the light shielding plate 3 completely covers the depth-variable grating 100. The light shielding plate 3 is made of a light-shielding material; the depth of the depth-variable grating 100 gradually becomes shallower from right to left, that is, the thickness of the photoresist layer 2 gradually becomes thinner from right to left, and the thickness of the substrate 1 gradually becomes thicker from right to left; the light shielding plate 3 is a plate-shaped object, arranged on the side of the photoresist layer 2 away from the substrate 1, that is, above the photoresist layer 2.

[0030] Step S400, moving the light shielding plate 3 according to a preset direction and a preset speed to expose the photoresist layer 2 to obtain an exposure area, wherein the preset direction and the preset speed are set according to the depth of each grating.

[0031] Specifically, the preset direction refers to the direction of the grating depth from deep to shallow. The preset speed is to determine the required exposure time according to the depth of each grating, and then determine the corresponding speed according to the exposure time and the distance between each grating. Wherein, the depth of the grating is proportional to the exposure time. When making a grating of a certain depth, it is necessary to expose a certain time at the position corresponding to the photoresist layer 2. Therefore, the gratings of different depths need different corresponding exposure times. More specifically, taking the present embodiment using negative photoresist as an example, the deeper the depth of the grating, the thicker the photoresist thickness required, and the longer the exposure time. It can be understood that, since the photoresist layer 2 needs to adopt different exposure times at different thicknesses, the photoresist layer 2 of different thicknesses can form gratings 100 of different depths after exposure. After the exposure time is determined, the distance to be moved is calculated according to the width of each grating and each gap, and the preset speed is calculated according to the moving distance and time.

[0032] In the present embodiment, the movement of the shading plate 3 is realized by a driving device (not shown). The driving device can be a motor or a cylinder. It can be understood that the preset speed can be calculated based on the structure of the depth-varying grating 100, so that the preset speed is configured to the driving device, so that the driving device moves the movable shading plate 3 at the preset speed. For example, when the depth-varying grating 100 is a gradual depth change, and the width of each grating and the width of each gap are the same, the preset speed movement is uniform. For another example, when there is a sudden change in the depth of the depth-varying grating 100, the preset speed movement is also sudden, rather than uniform. In other words, the preset speed is set according to the exposure time, width and width of each grating of the depth-varying grating 100.

[0033] In the initial state, the photoresist layer 2 is covered by the shading plate 3, and the corresponding hollow area 510 and the covered area 512 cannot be illuminated. When the shading plate 3 moves, the photoresist layer 2 is gradually illuminated, and when the hollow area 510 is exposed to light, the corresponding photoresist layer 2 will undergo a cross-linking reaction and form an insoluble network structure. This network structure makes the photoresist layer 2 harder in the exposure environment, and the permanent structure of the photoresist layer 2 is better. Further, in order to better expose, the present embodiment is to place the substrate 1 provided with the photoresist layer 2 and the shading plate 3 in the exposure device 5.

[0034] In this embodiment, during the exposure process of the photoresist layer 2, since the depth of the depth-varying grating 100 gradually becomes shallower from right to left, the shading plate 3 is uniformly moved from the right end of the photoresist layer 2 to the left end of the photoresist layer 2 (direction is X, speed is V), and at the same time, the exposure time is determined according to the depth of each grating, thereby determining the moving speed of the shading plate 3. In other words, the exposure time of the exposed photoresist layer 2 gradually decreases from the right end to the left end, that is, the exposure amount of the photoresist layer 2 gradually decreases from the right end to the left end. The present application realizes the gradual depth of the photoresist layer 2 by controlling the moving speed of the shading plate 3 when the photoresist layer 2 is exposed, thereby manufacturing a complex gradual grating structure and avoiding complex and expensive mechanical processing and electron beam exposure processes.

[0035] Step S500, after the photoresist layer 2 is exposed, the exposed area is developed to obtain the depth-varying grating 100. Specifically, before the exposed area is developed, it is necessary to determine whether the current photoresist layer 2 has been exposed based on the depth of the depth-varying grating 100 and the process parameters. When it is determined that the current photoresist layer 2 has been exposed, the photoresist layer 2 is developed using a developer to gradually remove the photoresist layer 2 dissolved in the developer. A groove is formed between the undissolved area of ​​the photoresist layer 2 and the dissolved area of ​​the photoresist layer 2, and the depth of the groove of the photoresist layer 2 is used as the depth of the depth-varying grating 100. The undissolved area of ​​the photoresist layer 2 serves as the top of the groove of the depth-varying grating 100, and the dissolved area of ​​the photoresist layer 2 serves as the bottom of the groove of the depth-varying grating 100, and the height between the top of the groove and the bottom of the groove is the depth of the groove. It is understandable that in the present embodiment, the photoresist layer 2 adopts a negative photoresist, therefore, the exposed area (hollow area 510) is an insoluble area, and the non-exposed area (covered area 512) is a dissolved area. It is understandable that the structure formed by the photoresist layer 2 after exposure and development has higher stability and corrosion resistance. The above-mentioned depth-varying grating 100 significantly improves the coupling efficiency and working bandwidth of the grating by matching grooves of different depths with the wave vector of the electromagnetic wave, and has a wide range of application prospects, especially in the terahertz band. Among them, the depth of the current photoresist layer 2 after exposure is consistent with the depth of the depth-varying grating 100, and the process parameters (such as the hardness of the exposure area of ​​the photoresist layer 2, the width of the grating, etc.) meet the preset process parameter requirements.

[0036] In this embodiment, after judging that the exposure of the photoresist layer 2 is completed, the developer is contacted with the photoresist layer 2 on the surface of the substrate 1, and the unexposed area of ​​the photoresist layer 2 maintains the original solubility, that is, the photoresist layer 2 in the unexposed area is gradually dissolved by the developer. The photoresist layer 2 in the exposed area becomes insoluble in the developer due to the photocuring reaction during exposure. Therefore, the photoresist layer 2 in the exposed area will remain in its original state, thereby obtaining a depth-variable grating 100. It can be understood that the solubility of the photoresist layer 2 in the developer is negatively correlated with the exposure amount of the photoresist layer 2, that is, the greater the exposure amount of the photoresist layer 2, the smaller the solubility of the photoresist layer 2 in the developer. Among them, the developer can be an organic solvent such as xylene, n-butyl acetate, and mixed alkanes. The development method includes but is not limited to rotation, spraying, and immersion.

[0037] In some feasible embodiments, metal sputtering is performed on the surface of the depth-variable grating 100 facing away from the substrate 1 to form a conductive layer of the depth-variable grating 100. A coupling structure is formed on the surface of the depth-variable grating 100 after metal sputtering, which can achieve efficient coupling between the grooves of the depth-variable grating 100 and the wave vector of the electromagnetic wave.

[0038] In some feasible embodiments, a series of subsequent treatments are performed after metal sputtering is performed on the surface of the depth-variable grating 100 facing away from the substrate 1, including but not limited to annealing and surface treatment. The present application can enhance the optical performance and mechanical stability of the depth-variable grating 100 by performing subsequent treatment on the grating surface.

[0039] Please see Figure 6 , which is a schematic diagram of the production of the depth-variable grating 100a provided in the second embodiment. In this embodiment, the structure of the depth-variable grating 100a is bilaterally symmetrical, and the depth gradually becomes shallower from the middle to both sides. During production, first, two identical shading plates 3a and 3b are placed side by side in the middle of the photoresist layer 2, and the contact point of the two shading plates 3a and 3b coincides with the center line 6 of the photoresist layer 2 to cover the photoresist layer together. In this embodiment, one shading plate 3a covers the left area of ​​the center line 6 of the photoresist layer 2, and the other shading plate 3b covers the right area of ​​the center line 6 of the photoresist layer 2; secondly, the shading plates 3a and 3b are moved away from each other in opposite directions X1 and X2, and at the same preset speed V, until they move to their respective preset end positions, so that the exposure time of each position of the left area and the right area of ​​the photoresist layer 2 is the same, so that the depth-variable grating 100 has a bilaterally symmetrical structure. The shape, size, and placement of the shading plates 3a and 3b can be designed according to actual needs and are not limited here. The moving directions and preset speeds of the shading plates 3a and 3b are just examples and can be set according to specific circumstances and are not limited here.

[0040] Please see Figure 7-8 , which is the depth variation grating 100b provided in the third embodiment. The depth variation grating 100b provided in the third embodiment includes two depth variation gratings with the same structure, and the two depth variation gratings with the same structure are arranged up and down, and the substrates 1a and 1b of the two depth variation gratings with the same structure are arranged back to back, and the photoresist layers 2 of the two depth variation gratings with the same structure are bonded together after exposure and development. During production, first, the two substrates 1a and 1b provided with the photoresist layer 2 and the mask 5 are arranged up and down relative to each other, so that the photoresist layers 2 on the substrates 1a and 1b are opposite; then, the photoresist layers 2 on the substrates 1a and 1b are simultaneously exposed and developed in the same manner; then, the two depth variation gratings are connected and fixed by means of adhesives, that is, the exposed and developed photoresist layers 2 on the substrates 1a and 1b are bonded to form a depth variation grating 100b with a top-to-bottom symmetrical structure. The above-mentioned top-to-bottom symmetrical structure of the depth variation grating 100b can realize a terahertz-type surface plasmon coupler. Among them, the above-mentioned depth variation grating 100b combination is only an example, and can be combined and arranged according to specific needs, and is not limited here. It can be understood that in this embodiment, in order to improve efficiency, two depth variation gratings with consistent structures are manufactured together when manufacturing the depth variation grating 100b. In some feasible embodiments, each depth variation grating in the depth variation grating 100b can also be manufactured separately in the same way. It can be understood that the light source suitable for exposure can be set between the masks 5 of the two substrates 1a and 1b.

[0041] Please see Fig. 9 In some other feasible embodiments, the photoresist layer 2' is made of positive photoresist, the thickness of the photoresist layer 2 is consistent with the thickness of the substrate 1', and the thickness of the photoresist layer 2' is the same as the deepest depth of the grating (such as Figure 4 only the exposure time needs to be different.

[0042] The photoresist layer 2' contains a photosensitizer, which is a dissolution inhibitor. Before the photoresist layer 2' is exposed, the photosensitizer will inhibit the solubility of the photoresist layer 2' in the dissolution solution. After the photoresist layer 2' is exposed, the photosensitizer will undergo chemical decomposition and change from a dissolution inhibitor to a dissolution enhancer, thereby increasing the solubility of the exposed area of ​​the photoresist layer 2' in the dissolution solution. It is understandable that the exposure amount of the photoresist layer 2' and the solubility of the photoresist layer 2' in the dissolution solution are positively correlated. The rest of the manufacturing process is the same as the first embodiment and will not be repeated here.

[0043] It is understandable that the selection of photoresists in the above embodiments is only an example, and either positive photoresist or negative photoresist can be selected as needed, or a combination of the two can be adopted.

[0044] In the above embodiments, the present application can realize a groove structure with a gradient depth by controlling the exposure amount of the photoresist, and can prepare a terahertz grating structure with high coupling efficiency and broadband performance by controlling the exposure and development technology through a simple light shield and combining the metal sputtering process.

[0045] It should be noted that the serial numbers of the embodiments of the present application are only for description and do not represent the advantages and disadvantages of the embodiments. And the terms "including", "comprising" or any other variants thereof herein are intended to cover non-exclusive inclusion, so that the process, device, article or method including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, device, article or method. In the absence of further restrictions, the elements defined by the sentence "including one..." do not exclude the presence of other identical elements in the process, device, article or method including the element.

[0046] Obviously, a person skilled in the art may make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include these modifications and variations.

[0047] The above are only preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the protection scope of the present application.

Claims

1. A method for manufacturing a depth-varying grating for a terahertz band, wherein the depth-varying grating for a terahertz band comprises a plurality of continuous gratings of different depths, characterized in that: The method comprises: coating a photoresist layer on one side of the substrate; A mask is arranged on a side of the photoresist layer away from the substrate, the mask includes a mask pattern corresponding to the depth-variable grating, the mask pattern includes hollow areas and covering areas arranged at intervals, the hollow area corresponds to a grating to expose the photoresist; Disposing a light shielding plate on a side of the substrate where the mask is disposed; Moving the light shielding plate according to a preset direction and a preset speed so that the photoresist covered by the hollowed-out area is sequentially exposed to obtain an exposure area, wherein the preset speed is set according to the depth of each grating; After the photoresist layer is exposed, the exposed area is developed to obtain the depth-varied grating.

2. The method for manufacturing a depth-variable grating for the terahertz band according to claim 1, characterized in that: The substrate thickness is consistent with the corresponding grating depth, and the photoresist layer is made of negative photoresist; or the substrate thickness is consistent, and the photoresist layer is made of positive photoresist.

3. The method for manufacturing a depth-variable grating for the terahertz band according to claim 1, characterized in that: The shading plate includes two identical shading plates, both of which are covered on the photoresist layer, and moving the shading plate according to a preset direction and a preset speed includes: The two shading plates are moved in opposite directions and at the same speed.

4. The method for manufacturing a depth-variable grating for the terahertz band according to claim 1, characterized in that: The shading plate includes two identical shading plates; the method for manufacturing a depth-variable grating for the terahertz band also includes: arranging the two substrates symmetrically up and down, so that the photoresist layers of the two substrates are symmetrically arranged up and down; Wherein, a light shielding plate is arranged on the side of the substrate where the mask is arranged, comprising: covering two identical light shielding plates on two substrates respectively; Wherein, moving the shading plate according to a preset direction and a preset speed includes: moving the two shading plates in opposite directions and at a preset speed.

5. The method for manufacturing a depth-variable grating for the terahertz band according to claim 1, characterized in that: Before moving the shading plate according to a preset direction and a preset moving speed, the method further includes: The substrate provided with the photoresist layer and the light shielding plate is placed in an exposure device, and the light shielding plate is moved in the exposure device to expose the photoresist layer.

6. The method for manufacturing a depth-variable grating for the terahertz band according to claim 1, characterized in that: The hollow areas are arranged at equal intervals, the covered areas are arranged at equal intervals, the preset speed is a uniform speed, and the depth-varying grating is a gradient depth grating.

7. The method for manufacturing a depth-variable grating for the terahertz band according to claim 1, characterized in that: The hollow areas are arranged at equal intervals, the covered areas are arranged at equal intervals, the preset speed includes a sudden change speed, and the depth-varying grating is a sudden change depth grating.

8. The method for manufacturing a depth-varied grating for the terahertz band according to claim 1, characterized in that: The method for manufacturing the depth-variable grating for the terahertz band also includes: Metal sputtering is performed on a surface of the depth-varying grating facing away from the substrate to form a conductive layer of the depth-varying grating.

9. The method for manufacturing a depth-variable grating for the terahertz band according to claim 8, characterized in that: After metal sputtering is performed on the surface of the depth-variable grating facing away from the substrate, the method for manufacturing the depth-variable grating for the terahertz band further includes: The conductive layer is annealed.

10. The method for manufacturing a depth-variable grating for the terahertz band according to claim 1, characterized in that: The thickness of the photoresist layer is set according to the depth of the depth-variable grating.

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