Method for manufacturing large-aperture all-quartz superlens

Abstract

The application belongs to the technical field of semiconductor process, and particularly relates to a preparation method of a large-aperture all-quartz superlens. The method comprises the following steps: performing standard processing on a quartz substrate, depositing a conductive layer on a first surface of the quartz substrate, and depositing a metal hard mask on a second surface of the quartz substrate; performing multiple times of splicing photolithography and etching on the metal hard mask: coating an anti-reflection layer and a photoresist on the metal hard mask in sequence and drying the anti-reflection layer and the photoresist, aligning exposure using a mask, developing after the aligning exposure, drying to form a hard film, etching the metal hard mask and cleaning, and splicing preset patterns formed multiple times into a first pattern. The metal hard mask is used as a mask, fluorine-based gas dry etching is adopted to etch the quartz substrate, and a super surface subwavelength structure is formed. Finally, the metal hard mask and the conductive layer are removed, and the large-aperture all-quartz superlens is prepared. The application realizes the preparation of the large-aperture all-quartz superlens, and the process is compatible with a CMOS production line and suitable for mass production.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor process technology, specifically relating to a method for preparing a large-aperture all-glass lens. Background Technology

[0002] Traditional metasurfaces mostly use silicon as a substrate, which has poor light transmittance and high optical loss in the ultraviolet-visible band, making it difficult to meet the requirements of transparent optical scenarios such as imaging, spectroscopy, and laser shaping. Although fused silica has excellent ultraviolet-infrared transmittance, low thermal expansion coefficient and high optical damage threshold, making it an ideal substrate for transmissive metasurfaces, it has the following problems when used in DUV lithography to fabricate large-aperture devices. First, the high transparency of quartz at DUV wavelengths results in extremely weak reflected signals, making it difficult for the autofocus system of the lithography machine to identify the surface position, easily leading to defocusing, false focus, and decreased pattern accuracy. Second, after the incident light penetrates the transparent substrate, it is reflected on the back side and interferes with the incident light, forming standing waves, scattering, and edge burrs in the photoresist, severely damaging the uniformity of subwavelength structural dimensions. Third, quartz has strong insulation properties and easily accumulates static electricity, leading to wafer transport obstruction and alignment misalignment, resulting in low yield. At the same time, conventional photoresist masks have low selectivity and poor resistance to etching in fluorine-based dry etching, and are limited by the single exposure field of DUV stepper / scanning lithography machines (such as the NIKON DUV S204, where the maximum field of view on the short side is only 25mm), making it difficult to fabricate large-diameter devices with diameters of 50mm or more, thus restricting the industrial application of all-quartz superconducting lenses. Summary of the Invention

[0003] To address the current technological limitations in fabricating large-diameter devices (50mm and above), which hinders the industrial application of all-lens superconducting lenses, this invention proposes the following specific solution:

[0004] In a first aspect, the present invention proposes a method for manufacturing a large-aperture all-lithic Premiere lens, the method comprising:

[0005] The quartz substrate is subjected to standard treatment to obtain a standard quartz substrate;

[0006] A conductive layer is deposited on the first surface of the standard quartz substrate;

[0007] A metal hard mask is deposited on the second surface of the standard quartz substrate;

[0008] The metal hard mask is subjected to multiple splicing photolithography and etching processes; after multiple splicing photolithography and etching processes, a first pattern is formed on the metal hard mask;

[0009] Using a metal hard mask with a first pattern as a mask, the standard quartz substrate is dry etched to form a metasurface subwavelength structure on the standard quartz substrate.

[0010] The metal hard mask and conductive layer of the standard quartz substrate are removed to obtain a large-aperture all-quartz superconducting lens; the large aperture is greater than or equal to 50 mm.

[0011] The beneficial effects of this invention are as follows:

[0012] (1) The first side of the standard quartz substrate of the present invention is deposited with a conductive layer. The material of the conductive layer is Ti and the thickness is 100nm, which improves the mechanical strength, conductive heat dissipation and transmission stability of the wafer. The second side of the standard quartz substrate is deposited with a metal hard mask, which solves the problem of automatic focusing and inaccurate focusing of transparent substrate photolithography, and eliminates the pattern distortion caused by back reflection and interference.

[0013] (2) The metal hard mask of the present invention is subjected to multiple photolithography steps. Each photolithography step involves coating an anti-reflection layer, spin-coating photoresist, pre-baking, aligning the exposure with a mask, etching the anti-reflection layer, removing the mask, developing, hardening, etching the metal hard mask and cleaning. Multiple preset patterns formed by multiple etching steps are spliced ​​together to form the first pattern, which breaks through the size limitation of a single exposure and can stably prepare full-stone PVC surface with a large aperture greater than or equal to 50mm.

[0014] (3) The material of the metal hard mask of the present invention is one or more of Al, Cr and Mo, preferably Cr. The quartz etching selectivity ratio under fluorine-based plasma is ≥15:1. Fluorine-based gas is used when dry etching standard quartz substrate, which realizes high-precision transfer of metasurface subwavelength structure, ensures the sidewall angle and uniformity of structure, and the whole process is compatible with CMOS (Complementary Metal-Oxide-Semiconductor) production line and can be mass-produced. Attached Figure Description

[0015] Figure 1 This is a flowchart of a method for preparing a large-aperture all-lithic Premiere lens according to the present invention;

[0016] Figure 2 This is a process diagram of the first etching of a metal hard mask according to an embodiment of the present invention;

[0017] Figure 3 This is a process diagram of a second etching of a metal hard mask according to an embodiment of the present invention;

[0018] Figure 4 This is a schematic diagram of the process for forming a first pattern on the standard quartz substrate according to an embodiment of the present invention;

[0019] Figure 5 This is a schematic diagram of the first pattern formed by multiple etchings on a standard quartz substrate according to an embodiment of the present invention. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] In some embodiments, such as Figure 1 As shown, this invention proposes a method for manufacturing a large-aperture all-stone Premiere lens, the method comprising:

[0022] A standard quartz substrate is obtained by standard processing. A conductive layer is deposited on the first surface of the standard quartz substrate. A metal hard mask is deposited on the second surface of the standard quartz substrate. The metal hard mask is subjected to multiple splicing photolithography and etching processes. After multiple splicing photolithography and etching processes, a first pattern is formed on the metal hard mask. Using the metal hard mask with the first pattern as a mask, the standard quartz substrate is subjected to dry etching to form a metasurface subwavelength structure on the standard quartz substrate.

[0023] In some embodiments, the preparation method of a large-aperture all-stone overglaze optic lens is specifically described:

[0024] The quartz substrate is subjected to standard treatment to obtain a standard quartz substrate.

[0025] For example, standard processing of a quartz substrate includes standard RCA cleaning of the quartz substrate and drying and dehydration to obtain a standard quartz substrate.

[0026] A conductive layer is deposited on the first surface of the standard quartz substrate; a metal hard mask is deposited on the second surface of the standard quartz substrate.

[0027] The metal hard mask is subjected to multiple splicing photolithography and etching processes; after multiple splicing photolithography and etching processes, a first pattern is formed on the metal hard mask;

[0028] Understandably, metal hard masks exhibit significantly better corrosion resistance, conformability, and sidewall perpendicularity than photoresist and oxide masks. The preferred material for metal hard masks is Cr, with a thickness greater than 100 nm, ensuring a dense, pinhole-free surface to meet the requirements of photolithography focusing and high selectivity etching.

[0029] Using a metal hard mask with a first pattern as a mask, the standard quartz substrate is dry etched to form a metasurface subwavelength structure on the standard quartz substrate.

[0030] The metal hard mask and conductive layer of the standard quartz substrate are removed to obtain a large-aperture all-quartz superconducting lens; the large aperture is greater than or equal to 50 mm.

[0031] In some embodiments, the steps for each photolithography step on the quartz substrate on which the metal hard mask is deposited are as follows:

[0032] S11: After sequentially coating the anti-reflection layer and photoresist onto the metal hard mask, the mask is dried.

[0033] For example, the anti-reflective layer can be BARC (Bottom Anti-Reflective Coating).

[0034] S12: Cover the metal hard mask with a mask plate.

[0035] S13: Align and expose the photomask to form a preset pattern on the photoresist.

[0036] S14: Remove the mask and perform development to clean away the photoresist at the preset pattern position; then etch the anti-reflection layer to expose the underlying metal hard mask.

[0037] S15: Dry the undeveloped photoresist to form a hard film.

[0038] S16: Using the hard mask and the underlying anti-reflective layer as a mask, etch the metal hard mask to form a preset pattern on the metal hard mask.

[0039] S17: Clean the photoresist and anti-reflective layer on the metal hard mask.

[0040] In some embodiments, multiple preset patterns formed by repeatedly etching the metal hard mask are stitched together to form a first pattern.

[0041] For example, the metal hard mask can be etched in two overlapping layers, such as... Figure 2 As shown, a first preset pattern is formed by etching on the metal hard mask for the first time, such as... Figure 3 The second etching process, as shown, forms a second preset pattern on the metal hard mask; in this example, the first and second preset patterns constitute the first pattern. Using the etched metal mask layer as a mask, a standard quartz substrate is etched, as shown... Figure 4 The image shows a standard quartz substrate after etching.

[0042] For example, taking the NIKON DUV S204 as an example, its maximum field of view for a single exposure is 25mm × 32mm. Since the final lens is circular, limited by the shortest side (25mm), a 25mm × 25mm square mask is used. Different aperture superlenses can be fabricated by increasing the number of stitching operations, such as... Figure 5As shown, a 50mm aperture all-lens HD lens is fabricated using 4 stitches, a 100mm aperture using 16 stitches, a 125mm aperture using 25 stitches, a 200mm aperture using 64 stitches, and a 300mm aperture using 144 stitches. To fabricate all-lens HD lenses of other apertures, simply select an appropriate photomask size and the appropriate number of stitches.

[0043] In some embodiments, the conductive layer is deposited by electron beam evaporation and magnetron sputtering; the material of the conductive layer is Ti.

[0044] In some embodiments, the thickness of the conductive layer is 100 nm.

[0045] For example, 100nm Ti is deposited on the back side using electron beam evaporation or magnetron sputtering processes to enhance conductivity and mechanical strength, and facilitate vacuum adsorption and automated transport.

[0046] In some embodiments, the material of the metal hard mask is one or more of Al, Cr, and Mo.

[0047] In some embodiments, the thickness of the metal hard mask is greater than 100 nm.

[0048] In some embodiments, the method for etching the metal hard mask is to use one or more of Cl2 plasma, O2 plasma or Ar plasma for etching.

[0049] In some embodiments, when the metal hard mask is Cr, wet etching with cerium ammonium nitrate solution is used; when the metal hard mask is Al, wet etching with phosphate-based solution is used.

[0050] In some embodiments, the method for dry etching the standard quartz substrate is as follows: dry etching the standard quartz substrate using a fluorine-based gas.

[0051] For example, fluorine-based gases include CHF3, C4F8, O2, and Ar. When dry etching the standard quartz substrate using fluorine-based gases, the etching ratio of quartz to the metal hard mask is greater than or equal to 15:1.

[0052] For example, the selectivity of metal hard masks for quartz etching under fluorine-based plasma is ≥15:1, and their corrosion resistance, conformability, and sidewall perpendicularity are significantly better than those of photoresist and oxide masks. For the metasurface subwavelength structures formed after etching, the sidewall angles are 88-90°, and the structural uniformity is ≤±5%. The metasurface subwavelength structures have steep sidewalls, precise dimensions, and high stability throughout the entire process.

[0053] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for manufacturing a large-aperture all-lithic Premier crystal lens, characterized in that, The method includes: The quartz substrate is subjected to standard treatment to obtain a standard quartz substrate; A conductive layer is deposited on the first surface of the standard quartz substrate; A metal hard mask is deposited on the second surface of the standard quartz substrate; The metal hard mask is subjected to multiple splicing photolithography and etching processes; after multiple splicing photolithography and etching processes, a first pattern is formed on the metal hard mask; Using a metal hard mask with a first pattern as a mask, the standard quartz substrate is dry etched to form a metasurface subwavelength structure on the standard quartz substrate. The metal hard mask and conductive layer of the standard quartz substrate are removed to obtain a large-aperture all-quartz superconducting lens; the large aperture is greater than or equal to 50 mm.

2. The method for preparing a large-aperture all-stone Premiere lens according to claim 1, characterized in that, The steps for each photolithography step in depositing a metal hard mask are as follows: After sequentially coating an anti-reflective layer and photoresist onto the metal hard mask, a drying process is performed. The metal hard mask is covered with a mask plate; The photomask is aligned and exposed to form a preset pattern on the photoresist; Remove the mask and perform a development process to clean away the photoresist at the preset pattern positions; The anti-reflective layer is then etched to expose the underlying metal hard mask; The undeveloped photoresist is dried to form a hard film; Using the hard mask and the underlying anti-reflective layer as a mask, the metal hard mask is etched to form a preset pattern on the metal hard mask; Clean the photoresist and anti-reflective layer on the metal hard mask.

3. The method for preparing a large-aperture all-stone Premiere lens according to claim 2, characterized in that, The first pattern is formed by stitching together multiple preset patterns created by repeatedly etching the metal hard mask.

4. The method for preparing a large-aperture all-stone Premiere lens according to claim 3, characterized in that, The conductive layer can be deposited by electron beam evaporation or magnetron sputtering; the material of the conductive layer is Ti.

5. The method for preparing a large-aperture all-stone Premiere lens according to claim 1, characterized in that, The thickness of the conductive layer is 100 nm.

6. The method for preparing a large-aperture all-stone Premiere lens according to claim 1, characterized in that... The material of the metal hard mask is one or more of Al, Cr, and Mo.

7. The method for preparing a large-aperture all-stone Premiere lens according to claim 1, characterized in that, The thickness of the metal hard mask is greater than 100 nm.

8. The method for preparing a large-aperture all-stone Premiere lens according to claim 1, characterized in that, The method for etching the metal hard mask is to use one or more of Cl2 plasma, O2 plasma or Ar plasma for etching.

9. The method for preparing a large-aperture all-stone Premiere lens according to claim 8, characterized in that, When the metal hard mask is Cr, wet etching with cerium ammonium nitrate solution is used; when the metal hard mask is Al, wet etching with phosphate-based solution is used.

10. The method for preparing a large-aperture all-stone Premiere lens according to claim 1, characterized in that, The method for dry etching the standard quartz substrate is as follows: the standard quartz substrate is dry etched using a fluorine-based gas.

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