A pattern-assisted overlay method for large-area light-blocking areas

Abstract

The present invention belongs to the field of micro-nano processing technology, specifically a method for overlaying a large-area light-blocking area based on pattern assistance. The present invention 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, and overlaying the large-area 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, it includes the processing of the working area, auxiliary pattern and light-blocking area of ​​the device, and is completed on a thin film window; its process flow includes photolithography, metallization, debonding, overlaying, metallization and debonding. The method of the present invention has the advantages of improving overlay accuracy, saving electron beam lithography time, shortening process time, etc.; it is suitable for hard X-ray high-contrast imaging of biological cells, organic materials and dielectric materials.

Description

Technical Field

[0001] The invention belongs to the field of micro-nano processing technology, and in particular relates to a method for overlaying a large-area light-blocking area. 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 radius according to the Fresnel zone principle. Compared with traditional Fresnel zone plates, 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 achieving multi-focal 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 background light. During micro-nanofabrication, if the working area of ​​the photon sieve's metal columnar structure and the large light-blocking area are processed in a single lithography process, in addition to consuming a large amount of electron beam exposure time, the backscattered electrons generated by the large-area light-blocking area will interfere with the spatial charge distribution of the high-resolution structure in the working area, thereby significantly increasing the process difficulty.

[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 figure, the processed structures cannot be effectively protected in the subsequent electroplating process, which in turn affects their integrity and functionality. The high aspect ratio columnar structures in the working area of ​​the hard X-ray photon screen pose a severe challenge to the overlay process due to their poor photoresist wettability.

[0005] The wettability of solid surfaces is generally determined by two primary factors: the surface's chemical state and physical morphology. Regarding the chemical state, common optimization strategies include removing surface impurities, introducing polar functional groups, and increasing chemical bonding sites. Specific methods include chemical treatment, plasma treatment, and UV irradiation. However, these methods are typically used to improve the surface's chemical properties. For high-aspect-ratio hard X-ray photon-sieving columnar structures, photoresist wettability issues primarily stem from physical morphology.

[0006] To address this issue, the present invention proposes a method for overlaying large-area light-blocking areas based on auxiliary patterns. This method introduces auxiliary patterns around existing structures, allowing them to form a protective barrier together with the top layer of photoresist, effectively covering the sides of the structure. This design provides sufficient protection for the existing structure during subsequent processing, significantly improving process reliability and yield, and ensuring that the hard X-ray photon screen's active area is not damaged during processing, thereby ensuring 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, thereby realizing more optical functions and meeting the growing demand for high-performance optical components at my country's synchrotron radiation X-ray microscopy lines, 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 present invention proposes a method for overlaying a large-area light-blocking area based on pattern assistance, which introduces auxiliary patterns around the existing structure so that the auxiliary patterns and the top-layer photoresist form a protective barrier together, effectively covering the side surfaces 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 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.

[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 thin film window. The process includes photoetching, metallization, degumming, overetching, 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 auxiliary pattern is designed to externally surround the working area, ensuring that after overlay, the metallized auxiliary pattern and the photoresist that does not wet the working area but covers the top of the auxiliary pattern and the auxiliary pattern together encapsulate the working area structure. The auxiliary pattern externally surrounds the working area, effectively encapsulating the working area after photolithography. The shape of the auxiliary pattern is designed based on the geometric shape of the working area, including but not limited to rings, squares, 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 this invention, the active area and auxiliary pattern are fabricated after the first photolithography and metallization process; while the large light-blocking area is fabricated during the overlay and second metallization process. Once the auxiliary pattern is fabricated along with the active area, it effectively protects the active area during the subsequent metallization process, ensuring its structural integrity.

[0014] In the present invention, the auxiliary pattern can be used to compensate for overlay accuracy. When overlaying the light-shielding area, by covering half the width of the auxiliary pattern, overlay can be performed with an overlay error of no more than 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 by the light-shielding area can range from 0 to the entire area of ​​the auxiliary pattern.

[0015] In the present invention, the overlay process 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 process includes but is not limited to the light-blocking area.

[0016] In the present invention, the photolithography can adopt optical photolithography or electron beam photolithography. As for overlay, since the present solution can compensate for errors through auxiliary patterns, the overlay alignment marks include but are not limited to standard overlay marks, thin film windows, etc.

[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 HfO2, Al2O3, etc.

[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, has a thickness of 100 to 500 nm, and a side length of 1 to 5 mm.

[0020] The present invention provides a method for pattern-assisted low-resist infiltration of a large-area light-blocking area of ​​a hard X-ray photon screen, including auxiliary pattern design and device addition. The process flow is as follows: Figure 2 The specific steps are as follows:

[0021] (1) Thermally evaporate a seed layer and spin-coat 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) degumming the sample obtained in step (3) to obtain a metallized working area and auxiliary pattern;

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

[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, and a side length of 1 to 5 mm. 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 based on the geometric shape of the working area, including but not limited to ring, 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 inward by the light-shielding area can range 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.

[0032] In step (4) and step (7) of the present invention, the method of removing the glue 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] By adding an auxiliary pattern, the present invention effectively wets the photoresist due to its much smaller aspect ratio than the active area structure, thereby providing excellent protection for the low-wetting structure of the hard X-ray photon screen active area. Furthermore, the auxiliary pattern acts as a light-blocking area, preventing the measurement results from being affected by an overly bright slit during optical measurement.

[0036] (2) Improve the overlay accuracy:

[0037] When overlaying the light-blocking area, an auxiliary pattern covering half the width allows for overlay without affecting the workspace structure, provided the overlay error is no greater than half the width of the auxiliary pattern. By optimizing the width of the auxiliary pattern, precise overlay can be achieved without the need for standard overlay marks, significantly improving processing yield, efficiency, and process tolerance.

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

[0039] In this invention, chemically amplified adhesive can be used to overlay the light-blocking area of ​​the hard X-ray photon screen, thereby reducing processing time required for electron beam lithography. Although electron beam lithography offers high resolution, it is slow for processing large-area structures. Chemically amplified adhesive, while having lower resolution, offers extremely high sensitivity and is suitable for processing large, low-resolution light-blocking areas during overlay, significantly reducing exposure time. Compared to processing the working area and light-blocking area using a single electron beam lithography process, the secondary lithography method using auxiliary patterns significantly shortens processing time and improves efficiency.

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

[0041] By separating the high-resolution working area and the large-area light-blocking area into two separate processing steps, the present invention improves processing accuracy and reduces process optimization time. If electron beam lithography is used only once to process both the working area and the light-blocking area, exposing the large area of ​​the light-blocking area will generate a large number of backscattered electrons. These electrons interfere with the spatial charge distribution of the high-resolution structure in the working area, reducing processing accuracy and increasing process optimization time. The method of adding auxiliary patterns separates the working area and the light-blocking area for processing, eliminating interference between the two processes. This method effectively improves processing accuracy and reduces 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 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 overlay of low photoresist wettability structures in the fields of integrated circuits, micro-electromechanical systems, etc.

[0043] Using the method of the present invention, a hard X-ray photon screen with a minimum column diameter of 140 nanometers and a height of 1.8 microns, along with a large light-blocking area, has been successfully fabricated. The present invention is suitable for high-contrast hard X-ray 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 flow chart of the pattern-assisted large-area light-blocking area overlay method of the present invention.

[0046] Figure 3 It is the exposure layout in steps 2 and 3 of Example 1, wherein (a) is the exposure layout 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 layout of overlay, including a large-area surrounding light-blocking area; wherein (c) merges two exposure layouts, and the overlapping area of ​​the two exposure layouts 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 a light-blocking area after debonding in step 5 of Example 1. DETAILED DESCRIPTION

[0050] The present invention will be further described below with reference to 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; process flow see 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) shows the working area, auxiliary pattern, and small-sized central light-blocking 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 scanning electron microscope photo of the sample after degumming 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 pattern and the second exposure pattern is a circular ring with a ring width of 15μm. The comparison of the two exposure patterns 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, 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;

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

[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; process flow see 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 As shown in (be), the working area, auxiliary pattern, and small central light-blocking area are exposed together. The working area has a diameter of 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 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 pattern-assisted large-area light-blocking area overlay method, characterized in that: By introducing auxiliary patterns around the existing structure, the auxiliary patterns and the top layer of photoresist together form a protective barrier, effectively covering the sides of the structure, and overlaying the large light-blocking area onto the working area with poor photoresist wettability, the hard X-ray photon screen working area is protected from damage during processing, thereby ensuring the high performance and stability of the final product. Specifically, the process includes the processing of the device's working area, auxiliary patterns, and light-blocking area, and is completed on a thin film window. The process includes photolithography, metallization, stripping, overlaying, metallization, and stripping. Among them: 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 of the auxiliary pattern is designed by surrounding the working area from the outside to ensure that after overlay, the metallized auxiliary pattern and the photoresist that does not wet but covers the working area and 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 based on the geometric shape of the working area; the auxiliary pattern can be continuous or discontinuous; if there are multiple working areas, the number of auxiliary patterns is one or more; The working area and auxiliary pattern are processed after the first photolithography and metallization; and the large-area 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-blocking area overlay method according to claim 1, characterized in that: The auxiliary pattern is used to compensate for the overlay accuracy; when overlaying 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-blocking 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-blocking 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 high refractive index for hard X-rays.

5. The pattern-assisted large-area light-blocking 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, and Ir; the metal oxide is selected from HfO2 and Al2O3.

6. The pattern-assisted large-area light-blocking area overlay method according to claim 2, characterized in that: The thin film window material is selected from silicon nitride, silicon dioxide, and silicon; the thin 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-blocking 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 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) degumming the sample obtained in step (3) to obtain a metallized working area and auxiliary pattern; (5) Spin-coating the sample obtained in step (4) with a photoresist and overlaying the sample, wherein the exposure pattern is a light-blocking area, and developing the sample to form a light-blocking area photoresist structure; (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-blocking 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 exposed light-shielding area 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 acetone.

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