Large-area light blocking area overlay method based on pattern assistance

Abstract

The invention belongs to the technical field of micro-nano machining, and particularly relates to a large-area light blocking area overlay method based on pattern assistance. According to the invention, the auxiliary pattern is introduced around the existing structure, so that the auxiliary pattern and the top photoresist jointly form a protective barrier to effectively cover the side surface of the structure, and the large-area light blocking region is nested onto the working region with poor photoresist wettability, so that the working region of the hard X-ray photon sieve is prevented from being damaged in the processing process; therefore, the high performance and the stability of the final product are ensured; the method specifically comprises the following steps: processing a working area, an auxiliary pattern and a light blocking area of the device on a film window; the technological process comprises photoetching, metallization, photoresist removal, overlay, metallization and photoresist removal. The method has the advantages that the overlay precision is improved, the electron beam photoetching time is saved, and the process time is shortened; the hard X-ray imaging device is suitable for hard X-ray high-contrast imaging of biological cells, organic materials, dielectric materials and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of micro-nano processing, and in particular relates to a large-area light-blocking area overlay method. Background Art

[0002] The photolithography process is a key step in micro-nano processing technology, which usually includes processes such as coating, pre-baking, exposure, development and post-baking. As the main technology for achieving patterning in the field of micro-nano processing, the photolithography process is widely used in many fields such as integrated circuits, micro-electromechanical systems, and X-ray devices. The X-ray photon sieve consists of a series of holes or columns. The diameter of these holes or columns gradually decreases with the increase of the radius according to the Fresnel zone principle. Compared with the traditional Fresnel zone plate, the photon sieve has a more flexible design and can realize more optical functions. It has the advantages of producing a smaller focal spot, suppressing high-order diffraction orders, and realizing multi-focus focusing.

[0003] In the hard X-ray band, the photon sieve needs to be thick enough for effective optical modulation, and a large light-blocking area is required to block the background light. In the micro-nano processing process, if the working area and the large light-blocking area of ​​the metal columnar structure of the photon sieve are processed by one lithography, in addition to consuming a lot of electron beam exposure time, the backscattered electrons generated by the large-area exposure of the light-blocking area will interfere with the spatial charge distribution of the high-resolution structure of the working area, thereby greatly increasing the difficulty of the process.

[0004] Another method is to use secondary photolithography: first, photolithography the working area, and then use overlay technology to process the light-blocking area. However, after development, the photoresist cannot fully penetrate the interior of the columnar structure in the working area with a large aspect ratio, resulting in the side of the structure being exposed. Figure 1 As shown. In the subsequent electroplating process, the processed structure cannot be effectively protected, which in turn affects its integrity and functionality. The high aspect ratio columnar structure in the working area of ​​the hard X-ray photon screen poses a severe challenge to the overlay process due to its poor photoresist wettability.

[0005] The wettability of a solid surface is usually determined by two main factors: the chemical state and physical morphology of the surface. In terms of chemical state, common optimization strategies include removing surface impurities, introducing polar functional groups, increasing chemical bonding sites, etc. Specific methods include chemical treatment, plasma treatment, and ultraviolet irradiation. However, these methods are usually used to improve the chemical properties of the surface, while for high aspect ratio hard X-ray photon sieving columnar structures, the photoresist wettability problem mainly stems from the physical morphology.

[0006] To solve this problem, the present invention proposes a method for overlaying a large-area light-blocking area based on an auxiliary pattern. The method introduces an auxiliary pattern around the existing structure so that the auxiliary pattern and the top layer of photoresist form a protective barrier together, effectively covering the side of the structure. This design can provide sufficient protection for the existing structure in subsequent processes, significantly improve the reliability and yield of the process, ensure that the working area of ​​the hard X-ray photon screen is not damaged during the processing, and thus ensure the high performance and stability of the final product.

[0007] The present invention can not only be used to prepare a hard X-ray photon sieve with a light-blocking area to achieve more optical functions and meet the growing demand for high-performance optical components at my country's synchrotron radiation X-ray microscopy stations, but is also suitable for overlay of low photoresist wettability structures in the fields of integrated circuits, micro-electromechanical systems, etc. Summary of the invention

[0008] The purpose of the present invention is to provide a stable, efficient and existing process compatible pattern-assisted large-area light-blocking area overlay method to solve the technical problem that the hard X-ray photon screen working area cannot be effectively overlaid due to poor wettability to photoresist.

[0009] The pattern-assisted large-area light-blocking area overlay method proposed in the present invention introduces an auxiliary pattern around the existing structure, so that the auxiliary pattern and the top-layer photoresist form a protective barrier together, effectively covering the side of the structure, and overlaying the large-area light-blocking area onto the working area with poor photoresist wettability; this design can provide sufficient protection for the existing structure in subsequent processes, significantly improve the reliability and yield of the process, ensure that the hard X-ray photon screen working area is not damaged during the processing, thereby ensuring the high performance and stability of the final product.

[0010] The method of the invention relates to the processing of a working area, an auxiliary pattern and a light-shielding area, and is completed on a film window. The process flow includes photolithography, metallization, degumming, overlaying, metallization and degumming.

[0011] In the present invention, the working area of ​​the device is a columnar structure area of ​​a hard X-ray photon sieve, which has poor photoresist wettability. The working area structure includes but is not limited to optical structures such as photon sieves, Fresnel zone plates, or other low photoresist wettability structures with certain functions.

[0012] In the present invention, the shape design of the auxiliary pattern is carried out by surrounding the working area from the outside to ensure that after overlay, the metallized auxiliary pattern and the photoresist that is not wetted but covers the working area and the top of the auxiliary pattern jointly encapsulate the working area structure. The auxiliary pattern surrounds the working area from the outside, so that the working area is effectively encapsulated after photolithography. The shape of the auxiliary pattern is designed according to the geometric shape of the working area, including but not limited to a ring, a square, etc.; the auxiliary pattern can be continuous or discontinuous; if there are multiple working areas, the number of auxiliary patterns can be one or more.

[0013] In the present invention, the working area and the auxiliary pattern are processed after the first photolithography and metallization; while the large light-blocking area is processed during the overlay and the second metallization process. After the auxiliary pattern is processed together with the working area, in the subsequent metallization process, the auxiliary pattern can effectively protect the working area and ensure the structural integrity of the working area.

[0014] In the present invention, the auxiliary pattern can be used to compensate for the overlay accuracy. When overlaying the light shielding area, by covering half the width of the auxiliary pattern, it can be ensured that the overlay is performed under the condition that the overlay error does not exceed half the width of the auxiliary pattern, without affecting the working area structure. During the overlay exposure process, the area of ​​the exposed light shielding area can be adjusted as needed, and the area of ​​the auxiliary pattern covered inward by the light shielding area can vary within the range of 0 to the entire auxiliary pattern area.

[0015] In the present invention, the overlay processing is for the light blocking area, which provides functional assistance to the working area with low wettability of the photoresist. The structure of the overlay processing includes but is not limited to the light blocking area.

[0016] In the present invention, the photolithography can be optical photolithography or electron beam photolithography. For overlay, since the present solution can perform error compensation through auxiliary patterns, the overlay alignment marks include but are not limited to standard overlay marks, film windows, and the like.

[0017] In the present invention, the metallization process includes but is not limited to electroplating, thermal evaporation, atomic layer deposition, etc. The metallized metal has a high refractive index for hard X-rays. If it is a noble metal, the material includes but is not limited to Au, Pt, Ir, etc.; if it is a metal oxide, the material includes but is not limited to HfO 2 , Al 2 O 3 wait.

[0018] In the present invention, the thin film window material includes but is not limited to silicon nitride, silicon dioxide, silicon, etc.

[0019] In the present invention, the film window is square, with a thickness of 100 to 500 nm and a side length of 1 to 5 mm.

[0020] The above-mentioned pattern-assisted low-resist infiltration hard X-ray photon screen large-area light-blocking area overlay method provided by the present invention includes auxiliary pattern design and device addition. The process flow is shown in Figure 2 The specific steps are as follows:

[0021] (1) thermally evaporate a seed layer and spin-coat a photoresist on the thin film window;

[0022] (2) performing photolithography on the sample obtained in step (1), wherein the exposure pattern is a working area and an auxiliary pattern, the auxiliary pattern is designed according to the working area layout, and after development, a photoresist structure of the working area and the auxiliary pattern is formed;

[0023] (3) metallizing the sample obtained in step (2);

[0024] (4) removing the glue from the sample obtained in step (3) to obtain a metallized working area and an auxiliary pattern;

[0025] (5) Spin-coating the sample obtained in step (4) with photoresist and overlaying, wherein the exposure pattern is the light-blocking area, and forming a light-blocking area photoresist structure after development;

[0026] (6) metallizing the sample obtained in step (5);

[0027] (7) Debonding the sample obtained in step (6) to obtain a metallized working area and a light-blocking area.

[0028] In step (1) of the present invention, the silicon nitride film window is square, grown by PECVD, has a thickness of 100 to 500 nm, a side length of 1 to 5 mm, and the window material includes but is not limited to silicon nitride, silicon dioxide, silicon, etc.

[0029] In step (2) of the present invention, the auxiliary pattern shape is designed according to the geometric shape of the working area, including but not limited to a ring, a square, etc.; the auxiliary pattern can be continuous or discontinuous; if there are multiple working areas, the number of auxiliary patterns can be one or more. The auxiliary pattern is processed together with the working area.

[0030] In step (3) and step (6) of the present invention, the metallization process includes but is not limited to electroplating, thermal evaporation, atomic layer deposition, etc.

[0031] In step (5) of the present invention, during the overlay exposure, the area of ​​the light-shielding area can be adjusted as needed, and the area of ​​the auxiliary pattern covered by the light-shielding area can be from 0 to the entire auxiliary pattern area. The outer side length of the light-shielding area is 0.1-20 mm, and the thickness is 0.1-10 μm.

[0032] In step (4) and step (7) of the present invention, the method for removing the resin includes but is not limited to soaking in a hot photoresist solvent, and the solvent includes but is not limited to acetone.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) Improve the wettability and protection effect of photoresist:

[0035] The present invention adds an auxiliary pattern, which can effectively wet with the photoresist because its aspect ratio is much smaller than that of the working area structure, thereby providing good protection for the low-wetting structure of the hard X-ray photon screen working area. In addition, the auxiliary pattern can also be used as a light-blocking area to avoid the situation in which the measurement result is affected by the over-bright slit during the optical measurement process.

[0036] (2) Improve the accuracy of engraving:

[0037] When overlaying the light shielding area, by covering the auxiliary pattern with half the width, it is possible to overlay without affecting the working area structure under the condition that the overlay error is not greater than half the width of the auxiliary pattern. By optimizing the width design of the auxiliary pattern, accurate overlay can be achieved without the need for standard overlay marks, significantly improving the processing yield, processing efficiency and process tolerance.

[0038] (3) Save electron beam lithography time:

[0039] In the present invention, chemical amplification glue can be used for the light-blocking area of ​​the overlay hard X-ray photon screen, thereby saving the processing time of electron beam lithography. Although electron beam lithography has a high resolution, its processing speed for large-area structures is slow; chemical amplification glue has a low resolution, but its sensitivity is extremely high, and it is suitable for processing low-resolution large-area light-blocking areas in overlay, which can greatly reduce the exposure time. Compared with using primary electron beam lithography to process the working area and the light-blocking area, the method of using auxiliary patterns for secondary lithography greatly shortens the processing time and improves efficiency.

[0040] (4) Improve machining accuracy and save process optimization time:

[0041] By dividing the high-resolution working area and the large-area light-shielding area into two-step processing, the present invention can improve processing accuracy and save process optimization time. If only one electron beam lithography is used to process the working area and the light-shielding area, a large area of ​​the light-shielding area will generate a large number of backscattered electrons, which will interfere with the spatial charge distribution of the high-resolution structure of the working area, reduce processing accuracy and increase process optimization time. The method of adding auxiliary patterns separates the working area and the light-shielding area for two processings without interfering with each other, which can effectively improve processing accuracy and save process optimization time.

[0042] The method of the present invention can be used to prepare a hard X-ray photon sieve with a light-blocking area. By adding auxiliary patterns around the structure with low photoresist wettability, the working area structure can be effectively protected in the subsequent process. The present invention integrates the light-blocking area into the hard X-ray photon sieve, which can block the background light and improve the optical performance of the hard X-ray photon sieve. The method of the present invention has the advantages of good process stability, high processing efficiency, saving process time, and compatibility with existing photolithography processes, and can significantly improve the processing quality and optical performance of hard X-ray optical devices. The present invention can not only be used to prepare a hard X-ray photon sieve with a light-blocking area, but is also suitable for the overlay of low photoresist wettability structures in the fields of integrated circuits, micro-electromechanical systems, etc.

[0043] By using the method of the present invention, a hard X-ray photon screen with a minimum column diameter of 140 nanometers, a height of 1.8 micrometers, and a large light-blocking area has been successfully processed. The present invention is suitable for hard X-ray high-contrast imaging of biological cells, organic materials, and dielectric materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a scanning electron microscope photograph after photoresist coating, exposure and development on a hard X-ray photon screen without auxiliary patterns. The photoresist covers the top of the structure and does not penetrate into the interior of the structure.

[0045] Figure 2 It is a flowchart of the pattern-assisted large-area light-shielding area overlay method of the present invention.

[0046] Figure 3 It is the exposure pattern in steps 2 and 3 of Example 1, wherein (a) is the exposure pattern of photolithography, including a hard X-ray photon screen working area, a small-sized central light-blocking area and an auxiliary pattern; wherein (b) is the exposure pattern of overlay, including a large-area surrounding light-blocking area; wherein (c) merges two exposure patterns, and the overlapping area of ​​the two exposure patterns is a ring.

[0047] Figure 4 This is a scanning electron microscope photograph after degumming in step 2 of Example 1.

[0048] Figure 5 This is a scanning electron microscope photograph after development in step 4 of Example 1.

[0049] Figure 6 This is a scanning electron microscope photograph of the hard X-ray photon sieve with light-blocking area after degumming in step 5 of Example 1. DETAILED DESCRIPTION

[0050] The present invention is further described below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited to the embodiments. Any simple changes to the process parameters in the embodiments fall within the scope of protection of the present invention.

[0051] Example 1: Preparation of a gold photon sieve lens with a minimum gold column diameter of 140 nm and a height of 1.8 μm suitable for focusing 8.39 keV hard X-rays; see the process flow Figure 2 As shown, the specific steps are:

[0052] (1) A silicon nitride film window with a supporting material of silicon was selected. The thickness of the silicon nitride window was 100 nm and the size was 1×1 mm. A gold seed layer was thermally evaporated on it and a 1.9 μm thick PMMA electron beam photoresist was spin-coated. The results are as follows: Figure 2 (a)

[0053] (2) The sample is subjected to electron beam lithography, gold electroplating, and degumming. The process is as follows Figure 2 (be) is shown. The working area, auxiliary pattern, and small-size central light-shielding area are exposed together. The diameter of the working area is 400μm, and the auxiliary pattern is a ring with an inner diameter of 400μm, an outer diameter of 460μm, and a ring width of 30μm. The electron beam exposure layout is shown in Figure 3 As shown in (a), the SEM photo of the sample after debonding is as follows Figure 4 As shown;

[0054] (3) Spin-coat a 2 μm thick UV5 chemical amplification glue on the sample, and use the film window as an alignment mark to perform electron beam overlay on the large area of ​​the surrounding light-blocking area. The process is as follows: Figure 2 As shown in (fg), the inner diameter of the surrounding light-blocking area is 430 μm, and the side length of the outer square is 1 mm. The exposure pattern is as follows Figure 3 As shown in (b), the overlapping area between the first exposure and the second exposure is a ring with a ring width of 15μm. The comparison of the two exposures is shown in Figure 3 (c)

[0055] (4) Develop the sample. The process is as follows: Figure 2 As shown in (h), the scanning electron microscope photo after development is as follows Figure 5 As shown in the figure, the auxiliary pattern gold ring and photoresist protect the photon screening gold pillars in the working area, solving the problem of Figure 1 The problem of the photon sieving gold pillars being exposed is shown;

[0056] (5) The sample is electroplated and debonded. The process is as follows Figure 2 As shown in (ij), the SEM photo after debonding is as follows Figure 5 As shown in FIG. 1 , the overlapping area of ​​the two exposure patterns forms a circular ring that is wide on the left and narrow on the right after electroplating. The widest part of the circular ring is 20 μm, and the narrowest part of the circular ring is 10 μm. Figure 6(b) shows that the method compensates for the 5 μm overlay error and successfully overlays the light-blocking area of ​​the gold column in the working area of ​​the hydrophobic hard X-ray photon sieve. The hard X-ray photon sieve prepared in this embodiment can be applied to the hard X-ray imaging system at 8.39 keV energy by enhancing the resolution and realizing the multi-focus function.

[0057] Example 2: Preparation of a gold photon sieve lens with a minimum gold column diameter of 100 nm and a height of 1 μm suitable for focusing 5.4 keV hard X-rays; see the process flow Figure 2 As shown, the specific steps are:

[0058] (1) A silicon nitride film window with a supporting material of silicon was selected. The thickness of the silicon nitride window was 50 nm and the size was 1×1 mm. A gold seed layer was thermally evaporated on it and a 1.1 μm thick PMMA electron beam photoresist was spin-coated. The results are as follows: Figure 2 (a)

[0059] (2) The sample is subjected to electron beam lithography, gold electroplating, and degumming. The process is as follows Figure 2 (be) shows that the working area, auxiliary pattern, and small-sized central light-blocking area are exposed together. The diameter of the working area is 100 μm, and the auxiliary pattern is a ring with an inner diameter of 100 μm, an outer diameter of 120 μm, and a ring width of 20 μm.

[0060] (3) Spin-coat a 1.2 μm thick UV5 chemical amplification glue on the sample, and use the film window as an alignment mark to perform electron beam overlay on the large area of ​​the surrounding light-blocking area. The process is as follows: Figure 2 As shown in (fg), the inner diameter of the surrounding light-blocking area is 110 μm, the side length of the outer square is 1 mm, and the overlapping area of ​​the first exposure pattern and the second exposure pattern is a circular ring with a ring width of 10 μm;

[0061] (4) Develop the sample. The process is as follows: Figure 2 (h)

[0062] (5) The sample is electroplated and debonded. The process is as follows Figure 2 (ij) shown.

[0063] The hard X-ray photon sieve prepared in this embodiment can be applied to a hard X-ray imaging system at 5.4 keV energy by enhancing resolution and realizing a multi-focus function.

Claims

1. A large-area light-shielding area overlay method based on pattern assistance, characterized in that: By introducing auxiliary patterns around the existing structure, the auxiliary patterns and the top layer of photoresist form a protective barrier together, effectively covering the side of the structure, and overlaying the large area of ​​light-blocking area onto the working area with poor photoresist wettability, ensuring that the working area of ​​the hard X-ray photon screen is not damaged during the processing, thereby ensuring the high performance and stability of the final product; specifically including the processing of the working area, auxiliary patterns and light-blocking area of ​​the device, and completing it on the thin film window; its process flow includes photolithography, metallization, stripping, overlaying, metallization and stripping; wherein: The working area of ​​the device is a columnar structure area of ​​a hard X-ray photon sieve, which has poor photoresist wettability; the working area structure includes a photon sieve, a Fresnel zone plate optical structure or other low photoresist wettability structures with certain functions; The shape design of the auxiliary pattern is carried out by surrounding the working area from the outside to ensure that after overlay, the metallized auxiliary pattern and the photoresist that is not wetted but covers the working area and the top of the auxiliary pattern jointly encapsulate the working area structure; the auxiliary pattern surrounds the working area from the outside so that the working area is effectively encapsulated after photolithography; the shape of the auxiliary pattern is designed according to the geometric shape of the working area; the auxiliary pattern is continuous or discontinuous; if there are multiple working areas, the number of the auxiliary pattern is one or more; The working area and auxiliary patterns are processed after the first photolithography and metallization; and the large light-blocking area is processed during the overlay and second metallization process; after the auxiliary pattern is processed together with the working area, in the subsequent metallization process, the auxiliary pattern can effectively protect the working area and ensure the structural integrity of the working area.

2. The pattern-assisted large-area light-shielding area overlay method according to claim 1, characterized in that: The auxiliary pattern is used to compensate for the overlay accuracy; when overlaying and exposing the light-blocking area, by covering half the width of the auxiliary pattern, it is ensured that the overlay is performed under the condition that the overlay error does not exceed half the width of the auxiliary pattern without affecting the working area structure; during the overlay exposure process, the area of ​​the exposed light-blocking area is adjusted as needed, and the area of ​​the auxiliary pattern covered inward by the light-blocking area varies within the range of 0 to the entire auxiliary pattern area.

3. The pattern-assisted large-area light-shielding area overlay method according to claim 2, characterized in that: The photolithography adopts optical photolithography or electron beam photolithography technology; for overlay, the alignment mark includes a standard overlay mark and a film window.

4. The pattern-assisted large-area light-shielding area overlay method according to claim 2, characterized in that: The metallization process includes electroplating, thermal evaporation, and atomic layer deposition; the metallized metal has a higher refractive index for hard X-rays.

5. The pattern-assisted large-area light-shielding area overlay method according to claim 2, characterized in that: The metal is a noble metal or a metal oxide, the noble metal is selected from Au, Pt, Ir; the metal oxide is selected from HfO2, Al2O3.

6. The pattern-assisted large-area light-shielding area overlay method according to claim 2, characterized in that: The film window material is selected from silicon nitride, silicon dioxide, and silicon; the film window is square, with a thickness of 100 to 500 nm and a side length of 1 to 5 mm.

7. The pattern-assisted large-area light-shielding area overlay method according to claim 2, characterized in that: The specific steps are as follows: (1) thermally evaporate a seed layer and spin-coat a photoresist on the thin film window; (2) performing photolithography on the sample obtained in step (1), wherein the exposure pattern is a working area and an auxiliary pattern, the auxiliary pattern is designed according to the working area layout, and after development, a photoresist structure of the working area and the auxiliary pattern is formed; (3) metallizing the sample obtained in step (2); (4) removing the glue from the sample obtained in step (3) to obtain a metallized working area and an auxiliary pattern; (5) Spin-coating the sample obtained in step (4) with photoresist and overlaying, wherein the exposure pattern is the light-blocking area, and forming a light-blocking area photoresist structure after development; (6) metallizing the sample obtained in step (5); (7) Debonding the sample obtained in step (6) to obtain a metallized working area and a light-blocking area.

8. The pattern-assisted large-area light-shielding area overlay method according to claim 7, characterized in that: In step (1), the silicon nitride film window is square, grown by PECVD, has a thickness of 100 to 500 nm, and a side length of 1 to 5 mm; In step (2), the auxiliary pattern shape is designed according to the geometric shape of the working area; the auxiliary pattern is continuous or discontinuous; if there are multiple working areas, the number of auxiliary patterns is one or more; the auxiliary pattern is processed together with the working area; In step (3) and step (6), the metallization process is selected from electroplating, thermal evaporation, and atomic layer deposition; In step (5), during the overlay exposure, the area of ​​the light-shielding area to be exposed is adjusted as needed, and the area of ​​the auxiliary pattern covered inward by the light-shielding area ranges from 0 to the entire area of ​​the auxiliary pattern; the outer side length of the light-shielding area is 0.1 to 20 mm, and the thickness is 0.1 to 10 μm; In step (4) and step (7), the method for removing the resist is to soak the resist in hot photoresist acetone.

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