A curved piston phase modulation MEMS array chip

Abstract

The application discloses a curved-piston phase modulation MEMS array chip, and belongs to the field of micro electro mechanical optical devices and precise photoetching technology. In view of the technical difficulties that the traditional torsion type DMD can only modulate light intensity, has no phase control ability, has no light condensing function, and is limited in waveband adaptation, and the existing EUV maskless photoetching system has great dynamic iteration difficulty and poor imaging uniformity, the application discloses a normal axial piston displacement integrated structure with a concave curved surface micromirror, discards the angle torsion light modulation paradigm, and adopts a hexagonal honeycomb pixel arrangement. The chip has high light field filling rate, and integrates macroscopic curved surface beam pre-converging and pixel-level phase encoding modulation functions. The chip is compatible with an industrial DMD interface, can be seamlessly adapted to a 30:1 concave mirror spot direct projection scanning type holographic direct writing imaging system, cooperates with an adaptive Bragg film system to eliminate imaging dark bands, and realizes low-cost iteration from static imaging to dynamic programmable imaging.

Description

Technical Field

[0001] This invention relates to the fields of microelectromechanical optical devices, multi-band optical field phase modulation, maskless micro / nano lithography, and ultra-precision optical imaging technology. Specifically, it relates to a curved piston-type phase modulation MEMS array chip, which is suitable for various scenarios such as visible light precision projection, UV / DUV atmospheric pressure maskless lithography, EUV ultra-high vacuum ultra-precision lithography, dynamic optical field encoding, and precision shaping of curved optical elements. It is particularly suitable for the dynamic iterative upgrade scenario of a 30:1 concave mirror spot direct projection scanning holographic direct writing imaging system, and belongs to the core technology fields of advanced semiconductor micro / nano fabrication and microelectromechanical optical devices. Background Technology

[0002] Existing commercial micromirror modulation devices are based on Texas Instruments' torsional DMD technology. A typical structure consists of a planar mirror with double-sided torsional hinges, relying on mechanical angle deflection to achieve beam switching and intensity / grayscale modulation. These devices are widely used in visible light projection and traditional mask lithography. While this technology has undergone long-term development and has formed a mature hardware driver and interface system, it is limited by its inherent technological paradigm, resulting in a significant decrease in reflection efficiency and a lack of phase modulation capabilities in the EUV band, making it difficult to meet the ultra-precision imaging requirements of advanced processes.

[0003] The core technological shortcomings of traditional torsional DMD devices are mainly reflected in their insufficient adaptability to photolithography: First, the modulation mechanism is simple, which can only achieve light intensity modulation and cannot generate controllable optical path difference. It lacks phase coding modulation capability, making it difficult to complete high-precision optical field phase coding and failing to meet the wavefront control requirements of EUV ultra-precision photolithography. Second, the optical structure is limited, using a planar reflective mirror, which lacks beam convergence and shaping capability, resulting in a large beam divergence angle and extremely low light energy utilization, making it unable to match the stringent requirements of EUV high-magnification miniaturized imaging optical path. Third, the array structure is defective, mostly using rectangular pixel arrangement, with large pixel gaps, low light field fill rate, easy to generate light field blind spots and imaging dark bands, and poor global exposure uniformity. Fourth, the band adaptability is narrow. The device is designed for visible light display scenarios, and has low reflection efficiency and serious optical loss in the ultraviolet, deep ultraviolet, and extreme ultraviolet bands, and does not have the adaptability to advanced semiconductor process photolithography conditions.

[0004] In the field of EUV maskless lithography, the applicant's prior application (application number: 202611238142.0, invention title: A concave mirror spot direct projection EUV imaging system) disclosed that a non-aspherical concave primary mirror is constructed by splicing multiple weakly curvature hexagonal sub-mirrors, and a maskless static spot direct projection imaging is achieved through a fixed pixel array. This effectively breaks through the magnification bottleneck, depth-of-field limitation, and mask industry chain dependence problems of traditional 4x mask EUV lithography. Simultaneously, the accompanying angle-adaptive variable-period Bragg multilayer film technology, through a two-stage tuning mechanism of coarse matching of inter-mirror reference periods and fine compensation of intra-mirror radial gradients, solves the problems of uneven reflectivity and dark bands in the imaging grid caused by differences in the incident angle of the entire optical path. Furthermore, the application proposes a concept of replacing the fixed sub-mirror module with a MEMS programmable pixel unit modulator to achieve dynamic wavefront modulation, wherein the modulator adopts an interferometric modulation method that combines a surface reflection structure with a displaceable inner reflection structure. However, the prior design only proposes a dynamic iteration concept and basic interference modulation principle, and still has several unresolved technical gaps: its surface structure does not adopt a continuous concave surface across pixels, lacks large-scale beam converging capability, and is difficult to match the stringent requirements of the incident beam divergence angle for a high-magnification concave surface direct projection optical path; it has not established a multi-band adaptation system, and the film system and structure are only designed for the 13.5nm extreme ultraviolet band and ultra-high vacuum conditions, and cannot take into account atmospheric pressure lithography scenarios such as ultraviolet and deep ultraviolet, lacking the design freedom of adaptive adjustment of pixel feature size according to the working wavelength; moreover, its addressing backplane is not compatible with the industrial standard DMD system, requiring the separate development of dedicated driver hardware, resulting in high engineering implementation costs and poor versatility. Therefore, there is an urgent need for a curved piston-type phase modulation MEMS array chip that combines continuous curved surface convergence, multi-band dual-condition adaptation, and compatibility with a mature driver system to substantially upgrade the prior technology.

[0005] Furthermore, another prior application filed by the applicant (application number: 202611347014.X, invention title: An Angle-Adaptive Variable Period Bragg Multilayer Film Reflector Group) disclosed a scheme for arranging a piston-type MEMS phase-modulated micromirror pixel array on the surface of a curved sub-mirror and performing cosine compensation on the piston displacement based on the local incident angle of the radial position of each micromirror pixel. This prior application primarily focuses on Bragg multilayer film reflection in the extreme ultraviolet band. Its micromirror pixel array is used to match the angle-adaptive film system design of the mirror group. It does not involve differentiated film systems and pixel size configurations across the entire visible to extreme ultraviolet bands, does not limit the hexagonal movable block configuration of the pixel unit, and does not disclose a CMOS addressing scheme compatible with the industrial standard DMD system. Based on the aforementioned prior application, this invention further addresses the issues of multi-band adaptation, pixel configuration, and the generalization of the driving system. Furthermore, the prior application disclosed a micromirror pixel array arranged on the surface of a curved sub-mirror, but did not disclose the double-layer conformal curved surface structure in which the first and second reflective surfaces of the present invention are formed by the same curved template, have the same curvature, and are conformally arranged. It also did not disclose the numerical aperture matching relationship between the overall concave curved surface that extends continuously across multiple pixel units and the rear-end spliced ​​aspherical concave primary mirror.

[0006] In summary, the industry currently lacks a general-purpose MEMS modulation chip that can adapt to multiple bands, curved surface focusing and shaping, high-precision phase coding modulation, high fill rate imaging, and seamlessly adapt to 30:1 concave mirror spot direct projection scanning holographic direct writing imaging systems. This makes it impossible to achieve low-cost iteration from static fixed lithography to dynamic programmable lithography, which restricts the large-scale implementation and advanced upgrading of maskless lithography technology. Summary of the Invention

[0007] 1. Purpose of the invention The purpose of this invention is to overcome the shortcomings of existing torsional DMD micromirrors, such as lack of phase modulation capability, lack of beam focusing function, single band adaptation, and poor imaging uniformity. It also addresses the technical pain points of existing EUV maskless lithography systems, including high difficulty in dynamic iteration, insufficient programmability, and poor compatibility between MEMS modules and curved optical paths. This invention provides a curved piston-type phase modulation MEMS array chip. The invention employs a curved piston-type phase encoding modulation architecture to achieve high-precision optical field phase encoding across the visible, UV, DUV, and EUV bands. It can seamlessly replace the fixed sub-mirror module of a 30:1 concave mirror spot direct-projection scanning holographic direct-writing imaging system, and is capable of operating under both atmospheric pressure and high vacuum conditions. This enables low-cost, smooth, and unmodified iteration of maskless lithography systems, adapting to the precision processing needs of various scenarios.

[0008] 2. Core Technology Solution To achieve the above objectives, the present invention adopts a novel technical solution: a curved piston-type phase modulation MEMS array chip, comprising a CMOS addressing substrate, a continuous curved surface structure, and an arrayed movable inner layer structure; each pixel unit comprises: a local region in the continuous curved surface structure corresponding to the pixel, a regular hexagonal movable block located on its backlight side and capable of axial piston displacement along the substrate normal, and an elastic support structure and a driving structure connecting the movable block.

[0009] The core innovative architecture of this invention is a dual-layer interferometric phase-encoded modulation + normal-axis piston differential displacement + concave curved surface focusing integration + multi-band film system adaptive matching. It is strictly based on the prior dual-layer reflection interferometric modulation mechanism and has been iteratively upgraded, unlike the traditional torsional dimming technology paradigm. Compared with the prior art, this invention abandons the mechanical angle deflection mode and relies on a dual-layer optical path structure with a fixed surface reflective layer and an inner movable curved surface reflective layer. By precisely controlling the optical path difference of the two optical paths through the axial displacement of the inner piston, it achieves interferometric multi-level phase encoding and intensity coordinated modulation, without the signal loss and grayscale distortion of traditional single light intensity modulation. At the same time, the continuous curved surface structure integrates a concave curved surface focusing function, which can compress the incident beam divergence angle and match a 30:1 high-magnification miniaturized imaging optical path, greatly improving light energy utilization and imaging resolution. This realizes the technological upgrade from the prior patented static dual-layer interferometric modulation to dynamic curved surface programmable interferometric modulation.

[0010] In the preferred embodiment of the extreme ultraviolet (EUV) band, the pixel array adopts a 1.40μm regular hexagonal honeycomb tightly arranged structure to eliminate pixel gaps and maximize the light field filling rate and global imaging uniformity. In other band embodiments, the width of the opposite side of the pixel unit increases with the increase of the center wavelength, taking 5μm or 10μm. For different working bands, curved mirrors are used to prepare differentiated reflective film systems. The EUV band uses an angle-adaptive variable-period Mo / Si Bragg multilayer film to match the radial incident angle gradient of the sub-mirrors, ensuring high reflectivity of Bragg resonance throughout the entire domain and eliminating dark bands in the stitched imaging grid. The UV and DUV bands use high-transmittance and high-reflectivity dielectric films to adapt to low-cost photolithography conditions under normal pressure.

[0011] The underlying electrical and interface architecture of this chip is fully compatible with the industry standard DMD, and existing driver hardware can be directly reused without the need for the development of new supporting equipment. At the same time, it can directly replace the fixed sub-mirror module of the 30:1 concave mirror spot direct projection scanning holographic direct writing imaging system without modifying the overall optical path, vacuum cavity, thermal management, and particle protection architecture, thus achieving a seamless iterative upgrade from a static imaging system to a dynamic programmable imaging system.

[0012] 3. Core Innovation Points (1) Principle paradigm innovation: Abandoning the industry’s decades-old twist angle dimming technology route, adopting a piston axial displacement phase coding modulation architecture, achieving a principle breakthrough from mechanical motion mode and optical field modulation mechanism, solving the core shortcoming that traditional devices cannot achieve phase coding.

[0013] (2) Decoupled integration of focusing modulation function: The chip integrates the dual functions of macroscopic curved surface beam pre-convergence and pixel-level high-precision phase modulation. The beam pre-convergence and divergence angle compression are uniformly completed by the continuous curved surface layer across pixels, and the normal axis piston displacement phase modulation is independently completed by the movable pixel unit of the inner array. The two functions are decoupled and matched in coordination, which not only solves the problems of ultraviolet and extreme ultraviolet beam divergence and low light energy utilization, but also realizes pixel-level dynamic wavefront control, which is suitable for ultra-high magnification miniaturized imaging optical path.

[0014] (3) Full-band, full-condition, and wide-spectrum adaptability: It covers the full spectrum modulation scenarios of visible light, UV, DUV, and EUV, and is compatible with both atmospheric pressure and ultra-high vacuum dual conditions. The UV / DUV band does not require vacuum equipment, which greatly reduces the cost of mid-range lithography. The EUV band meets the needs of high-end ultra-precision processing.

[0015] (4) Seamless iterative adaptability: It accurately matches the architecture of the self-developed 30:1 concave mirror spot direct projection scanning holographic direct writing imaging system, which can directly replace the fixed sub-mirror module. Combined with the variable period Bragg film system technology, it adapts to the gradient characteristics of the incident angle of the optical path, eliminates the dark band of dynamic imaging stitching, and has extremely low iteration cost and high feasibility.

[0016] (5) High engineering reusability: The underlying hardware interface and electrical specifications are compatible with mature industrial systems, eliminating the need to develop a new drive system. It can be quickly mass-produced and deployed, taking into account both R&D and commercial application needs. Attached Figure Description

[0017] Figure 1 Overall structural schematic diagram: In cross-section, five movable blocks are arranged along a concave curved surface structure that extends continuously across pixels. The leader lines are labeled as follows: 1 (CMOS addressing substrate), 2 (pixel unit), 3 (continuous curved surface structure), 4 (first reflecting surface), 5 (interference cavity), 6 (movable block), 7 (second reflecting surface), 9 (driving electrode), 10 (sacrificial layer cavity), 11 (pattern absorption layer), and 13 (arrayed movable inner layer structure).

[0018] Figure 2 Cross-sectional view of a single-pixel curved piston micromirror structure: including dashed light path (incident → reflection from the first reflecting surface → transmission to the second reflecting surface → return emission), piston displacement d with double arrows; leader lines labeled 1, 3, 4, 5, 6, 7, 8 (folded beam), 9, 10, 11.

[0019] Figure 3Schematic diagram of 1.44μm hexagonal honeycomb pixel array: pointy-top layout, side width w=1.44μm, row spacing 1.247μm, including dimension lines; the enlarged detail in the lower left corner shows a pixel unit (outer hexagon = pixel unit 2, inner dashed hexagon = movable block 6, diagonal fill ring = pattern absorption layer 11). Detailed Implementation

[0020] The technical solution of the present invention will be described in complete and clear detail below with reference to the accompanying drawings. The following preferred embodiments are used to illustrate the core structure and working principle of the present invention, but do not limit the scope of protection of the present invention.

[0021] This invention relates to a curved piston-type phase modulation MEMS array chip, which is fabricated by integrating a 0.13μm high-voltage CMOS addressing substrate with a MEMS pixel array. The CMOS addressing substrate integrates standard power rails for a 1.8V logic power supply, +10V addressing voltage, +18V bias voltage, and -14V reset voltage. It supports HSSI high-speed Sub-LVDS bit-plane data transmission and LSIF low-speed register configuration, is fully compatible with industrial DMD drive systems, and can be directly adapted to existing control hardware and software systems. The substrate incorporates independent row and column addressing units and a pixel-level driving electrode array, enabling independent and precise voltage output for each pixel unit, supporting single-pixel differentiated piston displacement control and phase encoding.

[0022] This invention employs an electrostatic vertical drive mechanism to achieve axial piston displacement, providing a preferred driving scheme for nanometer-level high-precision optical path difference control: a fixed driving electrode is set at the bottom of the pixel unit, and a movable electrode is integrated at the bottom of the movable inner layer reflective structure, forming a parallel plate electrostatic drive capacitor structure; a controllable voltage difference is output through the CMOS addressing substrate, generating an electrostatic attraction perpendicular to the normal direction, overcoming the stiffness of the elastic support structure, and driving the inner layer second reflective surface structure to perform axial piston displacement; after power failure or voltage difference removal, it resets due to the elastic restoring force of the elastic support structure, with no lateral offset or angular deflection throughout the entire process, exhibiting high displacement linearity, fast response speed, no magnetic interference, and no thermal drift, making it suitable for EUV high-precision lithography. For visible light and ultraviolet band embodiments with larger strokes, a displacement amplification mechanism can be set between the movable block and the driving electrode, or the electrostatic drive structure can be replaced with a piezoelectric drive structure or an electromagnetic drive structure to meet the stroke requirements of the corresponding bands; this invention does not limit the specific form of the drive structure.

[0023] The elastic support structure adopts a multi-folded flexible beam symmetrical support structure. The material is a low-stress, high-elasticity, fatigue-resistant single-crystal silicon or silicon nitride thin film with a thickness controlled between 0.8μm and 1.2μm. Four sets of folded beams are symmetrically arranged at the four corners of a single pixel to ensure axial compliance and high in-plane stiffness, effectively suppressing lateral movement and torsional offset, and ensuring that the piston displacement moves strictly along the normal direction of the substrate, providing a structural basis for precise control of sub-nanometer optical path difference.

[0024] In the preferred embodiment of the extreme ultraviolet (EUV) band, a single MEMS pixel unit is a regular hexagonal honeycomb structure with a side width precisely set to 1.40 μm. It employs a gapless, tightly packed arrangement, achieving an array equivalent resolution matching the 1920×1080 industrial standard. The light field fill rate approaches the theoretical limit, alleviating the problems of large gaps, uneven light field, and localized dark bands in traditional rectangular pixel arrays. The pixel unit adopts a dual-layer interference modulation architecture, consisting of a first reflective surface with a continuous curved surface structure and a second reflective surface of a movable block capable of axial piston displacement, forming a dual-layer optical path. The first reflective surface is a partially reflective film system with few period pairs, while the second reflective surface is a highly reflective film system with many period pairs. The intensities of the two reflected light paths are comparable to ensure interference contrast. During operation, there is no angular deflection; the output precisely controls the round-trip optical path difference of the dual optical paths by the reciprocating motion of a movable block along the normal direction of the chip substrate, achieving continuously adjustable output of destructive dark states, constructive bright states, and multiple intermediate gray levels. Simultaneously, the piston displacement of each pixel can be adjusted according to either the relative brightness (i.e., the target gray level) required by that pixel or the target phase value. Since the phase and intensity of the output light are uniquely determined by the same round-trip optical path difference, the chip can achieve intensity gray level output and phase encoding output respectively by switching the adjustment criteria under the same piston displacement degree of freedom. Specifically, the first and second reflective surfaces constitute a pixel-level interference cavity: the incident light is reflected at the first and second reflective surfaces and then superimposed for output. The piston displacement changes the distance between the two reflective surfaces, thereby continuously adjusting the optical path difference between the two reflected beams. When the equivalent optical path difference is an odd multiple of λ / 2, the output is destructive and dark; when it is an integer multiple of λ, the output is constructive and bright; at other positions, the output is a multi-level gray level between bright and dark.

[0025] It should be noted that the curved piston-type phase modulation of this invention does not involve beam convergence achieved independently by a single pixel. The continuous curved surface structure is an integral concave surface extending continuously across multiple pixel units. Its first reflective surface undertakes the convergence and divergence angle compression of the incident beam. The arrayed movable inner layer structure is located on its backlight side and consists of several regular hexagonal movable blocks. Each movable block only performs axial piston displacement along the normal direction to change the optical path difference between the first and second reflected light paths. Beam pre-convergence is achieved by the integral concave surface extending continuously across multiple pixel units. Its aperture is equal to the effective light-passing aperture of the chip, and its focal length is half the radius of curvature of the surface and is on the macroscopic order. Pixel-level phase modulation is achieved by the piston displacement of the movable blocks. The piston displacement does not change the surface shape of the integral concave surface, and the two functions are decoupled. The first and second reflective surfaces are formed from the same curved surface template, so their curvatures are consistent and conformally set, ensuring that the two reflected beams have a consistent convergence state, guaranteeing interference contrast and imaging quality. The continuous curved surface structure has a patterned TaN absorption layer in the non-pixel area. The TaN material has good light absorption characteristics and process adaptability in the EUV band, which can accurately define the light aperture of each pixel unit and effectively suppress stray reflections in the non-pixel area.

[0026] In the extreme ultraviolet (EUV) band, due to the strong absorption of all materials, the system cannot use transmissive optical elements. To ensure that the incident light can reach the second reflecting surface and return, the first reflecting surface uses a Mo / Si partial reflective film with few period pairs, providing a margin for transmission while maintaining a certain reflectivity; the second reflecting surface uses a Mo / Si high reflective film with many period pairs. To ensure the modulation effect of the interference bright and dark states, the two reflected lights must meet the condition of comparable intensity, and the core matching relationship must satisfy: R1≈T1 2 R2. In the EUV band, the reflectivity of the second reflective surface of the multi-period pair Mo / Si high reflectivity film is R2≈70%. Based on the above quantitative matching relationship, ignoring film absorption, the first reflective surface adopts a few-period Mo / Si film system with 3 to 5 period pairs, which can achieve a first reflective surface reflectivity R1≈30% and a transmittance T1≈70%. This accurately matches the light intensity balance requirement of the two reflected lights, ensuring both high dark-state contrast during destructive interference and effective bright-state reflectivity during constructive interference. This is consistent with the structural design of the present invention of "few-period pair partial reflective film and multi-period pair high reflectivity film".

[0027] The local incident angle differences in each pixel unit caused by the concave surface can be eliminated by pixel-level piston stroke calibration or driving voltage compensation, so that each pixel obtains a consistent optical path difference modulation range under its local incident angle. The specific calibration method can be found in the applicant's prior application (application number: 202611347014.X, invention title: An Angle-Adaptive Variable Period Bragg Multilayer Reflector Group). This prior application only relates to the piston stroke calibration method and does not constitute a structural limitation of the chip described in this invention. This invention can still be implemented even without this calibration method. The change in the normal direction within a single pixel unit is much less than 1° (i.e., the preset angle budget described in claim 5, preferably not greater than 1°), which can effectively avoid the problems of film system mismatch and phase modulation unevenness caused by angle deviation within a single pixel.

[0028] The curved first reflecting surface adopts a one-piece molding design with a weakly curved concave surface, which has a built-in beam pre-convexity function. This effectively compresses the incident beam divergence angle, improves beam collimation, and matches the convergence state of the outgoing beam with the numerical aperture of the concave primary mirror at the rear. The radius of curvature of the concave surface is much larger than the feature size of a single pixel unit, ranging from 500mm to 5000mm in a preferred embodiment. Therefore, the change in the normal direction within a single pixel unit is much less than 1°, and the spatial non-uniformity of phase modulation within the pixel and the angular mismatch of the Bragg film system can be ignored. At the same time, since the radial positions of each pixel unit are different, their local incident angles are continuously distributed across pixels. In a preferred embodiment, the value range of this local incident angle is 5° to 11°. The inter-pixel difference in local incident angle will cause the piston stroke required by each pixel unit to obtain a consistent optical path difference modulation range to be different. This invention eliminates this by independently calibrating the piston stroke (d=λ / (2cosθ)) according to the center incident angle of the radial position of each pixel unit, thereby achieving three-dimensional coordinated matching of pixel-level angle, optical path, and film period.

[0029] For different operating wavelengths, this invention employs differentiated film fabrication processes to achieve high reflectivity across the entire wavelength range: Under EUV band conditions, the curved mirror deposition angle adaptive variable period Mo / Si Bragg multilayer reflective film matches the corresponding film period according to the local incident angle difference of the radial position of the pixel, realizing radial gradient compensation within the mirror. Combined with the whole-machine two-level tuning mechanism, it ensures high reflectivity of Bragg resonance in the whole domain, effectively eliminating the hexagonal grid dark band of stitched dynamic imaging, and greatly improving imaging uniformity. At the same time, the film system avoids the p-polarization Brewster attenuation range, ensuring reflection efficiency and polarization robustness under large-angle off-axis incident.

[0030] It should be noted that the outermost layer of the Mo / Si multilayer reflective film may also be a capping layer. The capping layer can be made of an oxidation-resistant and carbon-contamination-resistant material (such as Ru, RuO2, or Mo2C), and its thickness is generally 1 nm to 3 nm. In this invention, since the first reflective surface is a few-period Mo / Si partial reflective film, the capping layer is located on the outermost side of the first reflective surface facing the incident beam. Its material and thickness must be considered in the reflectivity and transmittance design along with the few-period Mo / Si film system, so that the reflectivity of the first reflective surface still satisfies R1≈T1 after considering the capping layer. 2 The light intensity matching relationship of R2. This invention does not limit the specific material and thickness of the capping layer.

[0031] Under UV and DUV band conditions, a special high-reflectivity UV dielectric film is deposited on a curved mirror surface to suppress UV band scattering loss, improve beam reflection efficiency and transmission stability, and eliminate the need for a high-vacuum environment. It can operate stably in a cleanroom under atmospheric pressure, significantly reducing equipment maintenance and mass production costs. The first reflective surface, adapted for UV and DUV bands, uses a partially reflective dielectric film, allowing some of the incident beam to pass through to the inner second reflective surface. The second reflective surface uses a high-reflectivity dielectric film, forming a dual-path interference modulation structure to meet the requirements of light intensity matching and phase modulation. In a preferred embodiment, the outer surface of the high-reflectivity UV dielectric film is further provided with a dense protective film layer resistant to UV radiation. This dense protective film layer is a dense metal oxide or nitride film used to isolate the film layer from the erosion of water, oxygen, and organic pollutants in the atmosphere. This dense protective film layer ensures that the reflectivity attenuation rate of the chip after 1000 hours of continuous irradiation at atmospheric pressure and a 365nm band does not exceed 5%.

[0032] In visible light band applications, a broad-spectrum high-reflectivity film system is employed to balance beam reflection efficiency and optical field uniformity, making it suitable for general applications such as precision projection, optical modulation, and curved mirror shaping. The first reflecting surface for the visible light band uses a semi-transparent, semi-reflective film to achieve partial reflection and transmission of the incident beam. The transmitted beam is reflected back by the broad-spectrum high-reflectivity film on the inner second reflecting surface, forming a dual-path interference modulation structure suitable for the visible light band, meeting the requirements for full grayscale and full-phase modulation.

[0033] The core application advantage of this invention is its seamless adaptation to a self-developed 30:1 concave mirror spot direct-projection scanning holographic direct-writing imaging system. It can replace the original fixed sub-mirror modules in the system one by one, achieving an iterative upgrade from static imaging to dynamic programmable imaging. Alternatively, it can serve as the imaging core of the system, outputting a single programmable holographic imaging block written pixel-by-pixel by the CMOS addressable substrate. This imaging block can be an independently addressable local sub-region within the pixel array, or the entire array composed of all pixel units, which, in conjunction with the workpiece stage step-scanning stitching, synthesizes a large field-of-view exposure area. The "holography" described in this invention refers to pixel-level programmable light field encoding and dynamic wavefront modulation. By precisely controlling the optical path difference pixel by pixel, arbitrary pattern light field reconstruction is achieved, distinguishing it from traditional optical interference holographic imaging. Relying on pixel-level dynamic wavefront modulation and programmable light field encoding capabilities, it inherits the system's core advantages of 30x miniaturization, maskless operation, high uniformity, and low defects, while adding dynamic programmable imaging capabilities, adapting to multi-category, rapidly iterating semiconductor micro-nano fabrication R&D and small-batch mass production scenarios.

[0034] Multi-band quantization design parameter comparison table of this invention To match the interference modulation requirements of different wavelength bands and take into account the margin of deviation at the oblique incidence angle, this invention conducts a systematic and quantitative design of pixel size, piston stroke, and miniaturized imaging size for each working wavelength band of visible light, UV, DUV, and EUV. All parameters strictly meet the requirements of 2π full-phase modulation and reserve a margin for large incidence angle conditions. The specific parameters are shown in the table below: EUV 13.5nm 1.40μm ≈104λ ≈46.7nm 6.75 / 7.79nm ≥10nm DUV 193nm 5μm ≈26λ ≈167nm 96.5 / 111nm ≥150nm DUV 248nm 5μm ≈20λ ≈167nm 124 / 143nm ≥190nm UV 365nm 10μm ≈27λ ≈333nm 182.5 / 211nm ≥280nm Visible light 550nm 10μm ≈18λ ≈333nm 275 / 318nm ≥420nm The parameters in the table above are derived based on the core formula of interference modulation: the round-trip optical path difference of the beam satisfies Δ=2d·cosθ, and the minimum piston displacement required to achieve complete 2π phase modulation and cover the entire grayscale range of light and dark is d=λ / (2cosθ). Combined with the weak curvature surface constraint design of this invention, the local incident angle of the radial position of each pixel unit is 5°~11°, which is about 1.9% of the maximum stroke increment compared to the normal incident condition; the θ=30° column in the table is the stroke requirement under the condition of the maximum center incident angle of the sub-mirror. After the above two factors are superimposed, the stroke design value of each band retains a margin of not less than 25% relative to the stroke requirement to cover process tolerances and driving nonlinearity, which can cover the working conditions of the entire field of view and ensure the full-domain complete phase modulation capability. Meanwhile, the parameters in this table are consistent with the overall imaging performance: the EUV band 1.40μm pixel, after being scaled down by 30:1, corresponds to a wafer feature size of approximately 46.7nm, which matches the ultra-fine imaging performance of 48nm and below in the prior system; the DUV band 5μm pixel, after being scaled down, corresponds to a feature size of 167nm, which matches the requirements of submicron-level high-precision lithography, realizing a complete closed loop of theoretical design, structural parameters, and imaging performance. Preferred embodiment

[0035] Example 1: UV-band atmospheric pressure maskless photolithography example This embodiment is compatible with conventional ultraviolet (UV) lithography bands and operates in a cleanroom environment under atmospheric pressure, eliminating the need for high-vacuum chamber equipment. The chip employs a regular hexagonal honeycomb pixel array with a side width of 10μm. The curved first reflective surface is coated with a partially reflective dielectric film, and the second reflective surface is coated with a UV-specific high-reflectivity dielectric film. The piston stroke is designed to be no less than 280nm, ensuring low-loss transmission of the ultraviolet beam. This embodiment can precisely match the optical path of a 30:1 concave mirror spot direct-projection scanning holographic direct-writing micro-imaging system. Relying on high-precision pixel-level phase coding modulation capabilities, it optimizes the uniformity of the ultraviolet light field and imaging accuracy. It can stably adapt to conventional application scenarios such as mid-range precision lithography mass production, micro / nano structure batch processing, and optical patterning fabrication, balancing processing accuracy and equipment maintenance economy.

[0036] Example 2: High-precision photolithography at ambient pressure in the DUV band This embodiment is adapted to the deep ultraviolet (DUV) lithography band and also supports atmospheric pressure conditions. Optimized curvature parameters of the curved micromirrors and film structure specifically suppress scattering and energy loss in the deep ultraviolet band, improving beam transmission stability. Leveraging high-precision pixel-level phase encoding modulation capabilities, a standard holographic imaging block is output in a single pass. Combined with high-frequency scanning and stitching on the workpiece stage, large-area exposure synthesis is achieved, enabling sub-micron level ultra-fine maskless lithography. It is widely applicable to mid-range precision machining scenarios such as semiconductor mid-range processes, microelectromechanical system (MEMS) fabrication, and PCB discrete copper pillar pattern preparation, balancing processing accuracy with mass production economics.

[0037] Example 3: EUV band high vacuum ultra-precision dynamic lithography example This embodiment is adapted to the 13.5nm extreme ultraviolet (EUV) ultra-precision lithography band, matching the ultra-high vacuum operating environment of the entire system, and is specifically applied to a 30:1 concave mirror spot direct projection scanning holographic direct writing imaging system. The curved mirror is deposited with an angle-adaptive variable-period Mo / Si Bragg multilayer reflective film, which precisely matches the radial incident angle gradient characteristics of the concave primary mirror, achieving Bragg resonance high reflectivity across the entire domain and eliminating dark bands in the dynamically stitched imaging grid. Leveraging curved surface pre-convergence shaping and ultra-high precision piston phase modulation capabilities, coupled with a 30:1 high-magnification miniaturized optical path, the chip's complete 1920×1080 hexagonal pixel array imaging pattern, after miniaturization, forms an equivalent square imaging field of approximately 64.3μm×64.3μm on the wafer side. This field of view is a single complete imaging area output by all pixels as a whole, rather than local sub-region imaging. Relying on a 1000Hz high-frequency refresh mode, combined with a piezoelectric ceramic workpiece stage continuous scanning and shooting mechanism, a large-size exposure area can be synthesized by seamlessly stitching together multiple imaging fields of view, achieving ultra-fine pixel lithography imaging at 48nm and below. It is specifically adapted to high-end application scenarios such as high-end semiconductor ultra-precision micro-nano processing, advanced packaging pattern preparation, and cutting-edge lithography process research and development.

[0038] The specific kinematics and exposure stitching mechanism are as follows: The exposure process adopts a continuous, uniform scanning of the workpiece stage and a precise stepping between rows, employing a strobe-style stitching scheme. The strobe exposure and the workpiece stage position signal are triggered synchronously in real time. After a single row scan is completed, the workpiece stage automatically steps between rows, stitching each row and frame to create a full-coverage, 26mm × 33mm standard step exposure field effective area. Furthermore, the strobe exposure uses a narrow pulse mechanism with a pulse width of no more than 25ns, ensuring that the image-side displacement introduced by the uniform scanning motion within the single exposure integration time is no more than 1nm, far smaller than the 48nm minimum feature size on the wafer side. This eliminates the need for additional pixel motion compensation structures, fully guaranteeing imaging accuracy and stitching uniformity. Preparation process examples

[0039] This invention discloses a complete chip fabrication process, enabling those skilled in the art to fully reproduce the device and solving the industrial fabrication challenge of MEMS curved piston-type interference modulation chips. The specific steps are as follows: S1. CMOS substrate electrode fabrication: The addressing substrate is fabricated using a 0.13μm high-voltage CMOS process. Pixel-level independent addressing electrodes, common electrodes, and vertical driving electrode arrays are patterned on the substrate surface. Circuit passivation, aperture and metal lead fabrication are completed to form a complete electronically controlled driving bottom layer.

[0040] S2. Sacrificial Layer Deposition and Patterning: A polyimide or silicon dioxide sacrificial layer is uniformly deposited on the surface of the CMOS substrate after electrode fabrication. The cavity region and elastic beam avoidance region corresponding to the pixel piston displacement are patterned through photolithography and etching processes. The maximum displacement space of the movable structure is precisely defined so that the variation range of the round-trip optical path difference between the first and second reflected optical paths is not less than the center wavelength of the incident beam. The round-trip optical path difference is Δ=2d·cosθ, where d is the piston displacement and θ is the local incident angle at the pixel unit. Therefore, the displacement space of each band is set according to the maximum local incident angle of that band.

[0041] S3. Elastic support structure forming: A low-stress silicon nitride or single-crystal silicon structure film is deposited above the sacrificial layer. Through high-precision photolithography and dry etching processes, a four-corner symmetrical folded flexible elastic support beam array is patterned to ensure the axial flexibility and in-plane high rigidity of the structure and suppress micro-displacement lateral drift.

[0042] S4. Conformal Hyperboloid Structure Forming and Surface Patterning: First, a high-precision standard surface template is prepared using a grayscale photolithography + thermal reflow composite process. The photoresist film thickness gradient is precisely controlled using grayscale photolithography to form a pre-defined, weakly curvature surface prototype. Then, a precise temperature-controlled thermal reflow process is used to uniformly release surface stress and solidify the template to obtain the standard surface template. Using this unified surface template, the first reflective surface layer and the second reflective surface layer of the movable block are replicated to ensure consistent curvature and conformal matching between the first and second reflective surfaces. A pre-patterned sacrificial layer precisely defines the initial interference cavity length between the two surface structures, ensuring pixel-level interference optical path consistency. After the surface structure is formed, an absorption layer is patterned in the non-pixel area to precisely define the aperture of each pixel unit and suppress stray reflections in the non-pixel area, completing the fabrication of the double-layer conformal surface core structure.

[0043] S5. Band-matched reflective film deposition: For different working bands, corresponding functional films are deposited on the surface of the concave curved substrate: For the EUV band, a variable period Mo / Si Bragg multilayer reflective film is prepared using atomic layer deposition technology, and the film period is set differently according to the radial position of the pixel. A capping layer is deposited on the outermost layer of the film system; for the UV / DUV band, high and low refractive index dielectric films are deposited alternately, and a dense UV-resistant protective film is deposited on the outer surface of the film; for the visible light band, a broad-spectrum high reflective film is deposited to complete the optical functional layer preparation.

[0044] S6. Sacrificial Layer Release and Device Finishing: A dry release process is used to remove all sacrificial layers, releasing the movable pixel structure and forming a suspended double-layer interference cavity structure; cavity cleaning and stress annealing are completed to eliminate residual stress, ensure piston displacement repeatability and long-term structural stability, and finally complete the fabrication of the entire MEMS array chip. Invention and Innovation Effects

[0045] 1. Fundamental innovation and solid technological barriers: This invention adopts a curved piston axial displacement phase encoding modulation architecture, abandoning the angle deflection motion mode, and is fundamentally different from traditional DMD devices in terms of mechanical structure, modulation mechanism and optical function.

[0046] 2. Significantly upgraded optical performance and excellent imaging quality: The chip adopts a decoupled architecture for focusing and modulation functions, which achieves full-domain beam pre-convergence, compresses beam divergence angle, and improves light energy utilization through continuous curved surface layer; high-precision phase modulation is achieved through independent pixel piston displacement, and ultra-high light field filling rate is achieved with hexagonal honeycomb seamless arrangement; combined with adaptive film technology, dark bands in the stitched imaging grid are effectively eliminated, and the uniformity and resolution of full-domain imaging are significantly better than existing technologies.

[0047] 3. Full-band and full-condition adaptability, with a wide range of application scenarios: It fully covers visible light, UV, DUV and EUV multi-spectral modulation scenarios, and is compatible with both atmospheric pressure and ultra-high vacuum dual conditions. It meets the needs of conventional precision projection and mid-range photolithography mass production, and is also suitable for high-end semiconductor ultra-precision processing scenarios.

[0048] 4. Ultra-low iteration cost and high engineering feasibility: It is compatible with the self-developed 30:1 concave mirror spot direct projection scanning holographic direct writing imaging system, and can directly replace the fixed sub-mirror module without changing the core architecture of the whole machine. It realizes the smooth upgrade from static system to dynamic programmable system, avoiding the high cost and long cycle risk of traditional new equipment development.

[0049] 5. Hardware compatibility with mature systems and high feasibility for mass production: The underlying electrical, power supply and interface are fully compatible with the industrial standard DMD, and existing mature driver hardware and mass production processes can be directly reused, which greatly reduces R&D, production and operation and maintenance costs, and combines technological advancement with commercial applicability.

[0050] 6. Adapting to the needs of advanced process iteration: The dynamic pixel-level phase modulation capability enables software-defined arbitrary light field patterns, adapting to the R&D and production trends of semiconductors with multiple categories, small batches, and rapid iteration, breaking through the application limitations of traditional fixed pixel lithography systems, and providing broad space for technological iteration.

Claims

1. A curved piston-type phase modulation MEMS array chip, characterized in that, This includes addressable substrates, continuous curved surface structures, and arrayed movable inner layer structures; The continuous curved surface structure is a concave curved surface that extends continuously across multiple pixel units and has a first reflecting surface facing the incident beam, which is used to converge the incident beam and compress its divergence angle. The arrayed movable inner layer structure is disposed on the backlight side of the continuous curved surface layer structure, including a plurality of movable blocks arranged in an array. Each movable block constitutes a pixel unit and has a second reflective surface facing the first reflective surface. The movable block can be axially piston-displaced along the normal direction of the C-addressing substrate under the drive of the driving structure. The first reflective surface is a partial reflective surface, and the second reflective surface is a high reflective surface. The first reflective surface has a transmittance that allows a portion of the incident light beam to be transmitted to the second reflective surface and allows the light reflected by the second reflective surface to be transmitted out again, so that the intensity of the light reflected by the first reflective surface is comparable to that of the light reflected by the second reflective surface. The first reflective surface and the second reflective surface form a pixel-level interference cavity. The piston displacement is configured such that the range of the round-trip optical path difference between the first and second reflected optical paths is not less than the center wavelength of the incident beam, thereby realizing programmable modulation of the reflected light based on optical path difference control.

2. The curved piston-type phase modulation MEMS array chip according to claim 1, characterized in that: The first reflective surface and the second reflective surface are formed by the same curved template, so that their curvatures are consistent and they are conformally set; the movable block is a regular hexagonal movable block; the reflective film is configured differently according to the center wavelength, including at least one of the following: Mo / Si multilayer reflective film in the extreme ultraviolet band, high and low refractive index alternating dielectric film in the ultraviolet and deep ultraviolet bands, and broad-spectrum high reflective film in the visible light band.

3. The curved piston-type phase modulation MEMS array chip according to claim 1, characterized in that: The continuous curved surface structure has a patterned absorption layer in the non-pixel area to define the light aperture of each pixel unit and suppress stray reflections in the non-pixel area.

4. The curved piston-type phase modulation MEMS array chip according to claim 1, characterized in that: When the optical path difference is an odd multiple of half the wavelength, the two reflected lights cancel each other out and appear relatively dark; when it is an integer multiple of the wavelength, they grow together and appear relatively bright; and when they are in between, they appear as relatively multiple intermediate gray levels.

5. The curved piston-type phase modulation MEMS array chip according to claim 1, characterized in that: The radius of curvature of the concave surface is configured such that, on the one hand, the continuous surface structure pre-converges the incident light beam, compressing its divergence angle to match the receiving numerical aperture of the rear-end spliced ​​aspherical concave primary mirror; on the other hand, the local incident angle variation within a single pixel unit is not greater than a preset angle budget. The feature size of the pixel unit increases with the increase of the center wavelength of the incident light beam, and is not less than 15 times the center wavelength.

6. The curved piston-type phase modulation MEMS array chip according to claim 1, characterized in that: The surface of the concave reflective mirror is provided with a reflective film system, which is one of the following: (a) A Mo / Si multilayer reflective film adapted to the extreme ultraviolet band, wherein the film period of the Mo / Si multilayer reflective film of each pixel unit is set according to the radial position of the pixel unit to match the local incident angle of the position; the first reflective surface is a Mo / Si partial reflective film with few period pairs, and the second reflective surface is a Mo / Si high reflective film with many period pairs, so that the light reflected by the first reflective surface and the light reflected by the second reflective surface are comparable in intensity, so as to ensure the dark state contrast when the interference is destructive and the bright state reflectivity when the interference is constructive. (b) A highly reflective dielectric film adapted to the ultraviolet or deep ultraviolet band, wherein the highly reflective dielectric film is composed of alternating layers of high refractive index material and low refractive index material; wherein the first reflective surface is a partially reflective dielectric film and the second reflective surface is a highly reflective dielectric film; (c) A broad-spectrum high-reflectivity film adapted to the visible light band; wherein the first reflective surface is a semi-transparent and semi-reflective film, and the second reflective surface is a high-reflectivity film.

7. The curved piston-type phase modulation MEMS array chip according to claim 6(b), characterized in that: The outer surface of the high-reflectivity dielectric film is provided with a dense protective film layer resistant to ultraviolet radiation, so that the reflectivity attenuation rate of the chip under atmospheric pressure and clean working conditions does not exceed a preset threshold.

8. The curved piston-type phase modulation MEMS array chip according to claim 1, characterized in that: The CMOS addressing substrate is fabricated using a 0.13μm high-voltage process. Its electrical specifications, power rails, high-speed video data interfaces (including but not limited to HSSI Sub-LVDS interfaces) and low-speed LSIF configuration interfaces are fully compatible with the industry standard DMD device system, and existing mature driver hardware and control programs can be directly reused.

9. The curved piston-type phase modulation MEMS array chip according to claim 1, characterized in that: The arrayed movable inner layer structure is divided into several independently addressable imaging blocks on the CMOS addressing substrate. Each imaging block includes several pixel units, and the graphic data of each imaging block is independently written and refreshed by the CMOS addressing substrate, so that the chip outputs a complete imaging block graphic at a time. This imaging block graphic is used to sequentially stitch together with adjacent imaging block graphics to form the target exposure area.

10. The curved piston-type phase modulation MEMS array chip according to claim 6(a), characterized in that: The film period of each pixel unit is set in a one-to-one correspondence with the local incident angle of its radial position, and the piston stroke of each pixel unit is set according to the local incident angle, so that each pixel unit has a consistent optical path difference modulation range under its local incident angle.

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