Projection Lens Research Articles

高分辨率像方远心连续变焦投影镜头的设计

高分辨率像方远心连续变焦投影镜头的设计

Analysis and correction of the distortion error in a DMD based scanning lithography system

Abstract DMD based lithography system provides the feasibility to achieve multi-point parallel direct writing exposure. However, the distortion of the projection lens in a scanning lithography system not only deviates the vertical size (vertical to the scanning direction), but also deviates the center position of an accumulated exposure point from the ideal one. In this work, we report a simple and realizable imaging compensation method, demonstrate as a combination of changing the magnification of the projection lens with loading an appropriately designed mask on DMD to eliminate the effects induced by distortion. With this method, the maximum center deviation of the accumulated exposure point is reduced from 4 . 3 μ m to 1 . 45 μ m , and the maximum size error is reduced from 0 . 4 μ m to 0 . 1 μ m with a 0.03% distortion projection lens in simulation. Moreover, we demonstrated the feasibility and effectiveness of the method experimentally by fabricating gratings with high geometry quality in large areas. Therefore, such simple method may have practical significance for improving the lithography quality of DMD-based system.

Alignment turning system for precision lens cells

This research increases the ability and value of a traditional vertical lathe and applies to manufacture a precise lens cell for the optical industry. The optical performance is limited by the residual centration error and position accuracy of conventional assembly methods. Recently, the development of a poker-chip assembly system with high-precision lens barrels has overcome these limitations and provided a solution for ultra-high-performance optical systems. To develop a high-precision lens cell by using poker-chip assembly, an alignment turning system (ATS), is developed based on a vertical lathe and equipped with tactile and optical measurement modules. Inside the ATS, the building-in the vibration/temperature monitoring sensors, which help to self-monitoring and network communication with the intelligent manufacturing techniques, to understand and master the reliability and efficiency of ATS. This system can manufacture precise lens cells, applied for optical metrology, high numerical aperture objective lenses, and lithography projection lenses. This paper describes the design and development of the ATS and its capabilities. The ATS is composed of measurement, alignment, and turning modules. After the ATS completes the measurement, alignment, and turning processes, the centration error of a lens cell, which is 200 mm in diameter, can be controlled to within 10 arcsec. Here, a lens cell with three subcells was assembled through the poker-chip method; each subcell was measured and then it underwent alignment and turning processes. The lens assembly test was performed five times by three technicians, and the average transmission centration error of the assembly lens was 12.45 arcsec. The results demonstrate that the ATS can achieve considerable assembly efficiency for high-precision optical systems.

High-order wavefront aberration measurement method for hyper-NA lithographic projection lens based on a binary target and rotated regression matrix

Abstract A high-order wavefront aberration (HWA) measurement method for a hyper-NA lithographic projection lens based on a binary target with eight directions and rotated regression matrix is proposed. A linear model between the aerial image intensity distribution of the hyper-NA lithographic projection lens and HWAs is built by principal component analysis and regression matrix rotation. Compared to the conventional method using a binary target with six directions, the proposed method improves the efficiency of pupil sampling, increases the modeling speed, extends the measuring range of the wavefront aberrations, and detects the HWAs of the hyper-NA lithographic projection lens accurately. The lithographic simulator PROLITH is used to validate the accuracies of the HWA measurement and analyze the impact of the illumination types of source on the accuracy of the HWA measurement, as well as the polarization rotation of illumination, the sample interval of the aerial images, and the manufacturing error of the test target. The results show that the proposed method retrieves 60 terms of Zernike coefficients ( Z 5 – Z 64 ) with measurement accuracy greater than 1.03 × 10−3 λ .

Design of compact ultrafast microscopes for single- and multi-shot imaging with MeV electrons

Ultrafast high-energy electron microscopy, taking advantage of strong interaction of electrons with matter while minimizing space charge problems, can be used to address a wide range of grand challenges in basics energy sciences. However, MeV-electron lenses are inherently bulky and expensive, preventing them from acceptance in a broad scientific community. In this article, we report our novel design of a compact, low-cost imaging-lens system for MeV-electrons based on quadrupole multiplets, including triplet, quadruplet and quintuplet, both symmetric and asymmetric. We compare optical performance of quadrupole-based condenser, objective and projector lenses with that of the traditional round-lenses and discuss the strategy for their practical use in constructing MeV-electron microscopes for high spatial and temporal resolution single- and multi-shot imaging. Combining the compound electron-optical system with a photocathode radiofrequency (RF) gun, such a MeV electron microscope can be fit into a small-sized laboratory for ultrafast observations and measurements.

Zoom projection lens design for small throw ratio and large field of view

In order to meet the requirements of large screen projection displays, we propose an ultra-thin zoom projection lens with a small throw ratio (TR), ultra-short throw distance and large field-of-view (FOV) using a digital micromirror device as a spatial modulator. A refractive–reflective system is developed to correct the distortion and shorten the projection distance. The image size (diagonal, 16:9 aspect ratio) of the projector is 80–120 in. (2.032–3.048 m) with a TR of 0.22, TV distortion < 0.6%, root mean square (RMS) spot size < 1.1 mm, relative illumination > 85% and modulation transfer function > 0.4 at 0.55 lp/mm for all fields and zoom conditions. When the tolerance error is considered, the RMS value is less than 1.3 mm for all fields and zoom conditions. Finally, the projection lens is fabricated and tested according to the designed model.

Multi-scale structure patterning by digital-mask projective lithography with an alterable projective scaling system

We report a flexible and efficient method to pattern two-dimensional (2D) multi-scale structures by digital-mask projective lithography (DMPL) with an alterable projective scaling system. In the developed DMPL system, femtosecond laser was modulated by digital micromirror device (DMD) to generate a designable intensity distribution with digital image information. The projective law of this DMPL system based on the geometric optics theory verified for different projective scaling lens systematically has been studied. With the combination of the customizable DMD elements and alterable projective scaling system, 2D designable patterned microstructures with multi-scale size range from millimeter to hundred nanometer have been achieved by a single exposure. In addition, an engineered Fresnel zone plate (FZP) with numerical aperture (NA) of 0.36 and focal length of 114 μm has been achieved by a single exposure of 1.2 s. The acquisition of the array of FZP lens shows the stability and efficiency of the pattern process. The proposed method could be expected to play an important role in the flexible and efficient fabrication of engineered 2D multi-scale structures.

7‐3: A Large‐scale Multi‐projection Light‐field Display based on Multi‐view Sampling Calibration

We proposed a large‐scale multi‐projection light‐field display system, including projectors and a cylindrical diffuser, which is 1.8m high with a radius of 3m. We design a wide‐field projection lens and apply light‐field calibration method based on multi‐view sampling to accurately reconstruct light‐field of models in real space.

Modeling and optimization of lens heating effect for lithographic projector

In optical lithography tools, thermal aberration of a projection lens, which is caused by lens heating effect, leads to degradation of imaging quality. In addition to in-line feedforward compensation technology, thermal aberration can be reduced by optimizing optical design of a projector. Thermal aberration analysis of a projection lens benefits the optimization of optical design. A model of lens heating effect for a lithographic projector is introduced, which is capable of evaluating the synthetical thermal aberration of a projector as well as analyzing the contribution of an individual optical element. Simulation results by the introduced model show that not only the deformation of lens surface, the variance of refractive index but also the change of optical path, which depends on optical design, should be considered in thermal aberration analysis. The contributions of optical elements at different locations of the projector are also analyzed. Based on the model and the simulation results, an optimization method is proposed. A projector for i-line lithography is optimized by the proposed method. Main aberrations Z5, Z9, and Z17 are reduced by about 40%. The image quality of the lithographic projector in steady state is also improved.

An ultrashort throw ratio projection lens design based on a catadioptric structure

In this paper, we present a rotational symmetry for an ultrashort throw (UST) lens with offset field. The UST lens has a throw ratio of 0.23 and a total track of 195 mm. The optical elements of the UST lens are comprised of two parts. First, a catadioptric projection lens where the catadioptric function permits reaching an ultrashort throw ratio, short total track, while at the same time requiring fewer lens elements. The second part is a collimating lens which takes advantage of the telecentric condition to generate uniform total internal reflection (TIR) in the TIR prism. With this design, an effective focal length of -1.96 mm and a f-number of 2.4 can be obtained. The root mean square spot size and lateral colour of all fields are smaller than one pixel in size. The maximum optical distortion of −0.97% and TV distortion of 0.2% are acceptable. In terms of image quality, the modulation transfer function (MTF) values for all fields are above 0.65 at 0.245 line pairs/mm. Even when the tolerance error is considered, the MTF values for all fields are still above 0.3. The suitability of the novel UST lens design for projection applications is discussed.

Projector-defocusing rectification for Fourier single-pixel imaging.

Fourier single-pixel imaging (FSI) is an efficient single-pixel imaging method of obtaining high-quality (resolution/signal-to-noise ratio) 2D images, which projects sinusoid patterns on the object and reconstructs the image through reflected light. The typical system of FSI consists of a single-pixel detector and a digital projector. However, the defocusing of the projector lens blurs the projected patterns, which results in reduced imaging quality. In this work, we propose the projector-defocusing rectification for FSI, which optimizes projector defocusing for the first time. The proposed method rectifies Fourier coefficients using the amplitude ratio between original and defocused patterns, which we can acquire through a controlled experiment on a whiteboard. The enhancement of imaging quality in imperfect circumstances is demonstrated by simulations and experiments.

Design of large aperture zoom projection lens

In order to obtain a large aperture zoom projection lens after optimizing a large aperture fixed focal length projection lens as the initial structure, a reasonable initial structure of fixed focal length lens was selected.According to DMD diagonal size, the dimension mapping of initial structure was done using AUTOCAD, the material of each lens was initially selected, and 5 zoom components were programmed in this system. The design was carried out by limiting the basic parameters and dimensions of lens with various operations, and 2 aspheric surfaces were used reasonably. After the optimization by using the optical design software ZEMAX and CODE V, a zoom projection lens system in visible light band was obtained. The system has a short focal length of 14.61 mm with 60° field of view(FOV) and 1.5 F number, while it has a long focal length of 29.31 mm with 30° FOV and 1.6 F number. The design results show that the modulation transfer function (MTF) of each FOV at each focal length is not less than 0.46 at the cut-off frequency 60 lp/mm. The dispersion angle at each focal length is not more than 1.6'. The projection lens achieves high quality of image. This lens system consists of 11 pieces of lenses and 1 piece of parallel plate, and the lens 2 uses aspheric surface. The system has less chips of lenses with low refractive index, and the material of each lens is easy to choose.

Design of zoom projection lens with large aperture and wild view

Design of zoom projection lens with large aperture and wild view

基于多偏振照明的浸没式光刻机投影物镜高阶波像差快速检测技术

基于多偏振照明的浸没式光刻机投影物镜高阶波像差快速检测技术

Image magnified lensless holographic projection by convergent spherical beam illumination

In liquid crystal spatial light modulator (SLM)-based holographic projection, the image is usually displayed at a distant projection screen through free space diffraction from a computer-generated hologram (CGH). Therefore, it allows for removing of the projection lens for the sake of system simplification and being aberration free, known as the “lensless holographic projection”. However, the maximum size of the optical projected image is limited by the diffraction angle of the SLM. In this Letter, we present a method for the implementation of image magnification in a lensless holographic projection system by using convergent spherical wave illumination to the SLM. The complete complex amplitude of the image wavefront is reconstructed in a lensless optical filtering system from a phase-only CGH that is encoded by the off-axis double-phase method. The dimensions of the magnified image can break the limitation by the maximum diffraction angle of the SLM at a given projection distance. Optical experiment results with successful image magnification in the lensless holographic projection system are presented.

Design of smallcaliber dual-channel dome screen projection lens

Design of smallcaliber dual-channel dome screen projection lens

深紫外光刻投影物镜的三维偏振像差

深紫外光刻投影物镜的三维偏振像差

Maskless Lithography Based on Digital Micro-Mirror Device (DMD) with Double Sided Microlens and Spatial Filter Array

A ultra-violet (UV) maskless lithography system is developed for arbitrary UV patterning. The system consists of an UV illumination system, a digital micro-mirror device (DMD), a projection system, and a double-sided microlens and spatial filter array (D-MSFA). The DMD acts as a virtual mask for generating arbitrary patterns by individually turning on or off of each micro-mirror. The projection lens projects the image of DMD onto the D-MSFA, which consists subsquently the fisrt microlens array (MLA1), the pinholes array, and the second microlens array (MLA2). The MLA1 focus the light from DMD to its corresponding pinhole, and the MLA2 projects the image of pinhole array onto a substrate to form a point array of UV light. The profiles of microlenses are designed optimized to chieve smallest focused spot size. A method has been developed to fabricate the D-MSFA and to ensure high microlens profile accuracy and excellent alignment between microlens arrays and pinhole array. The obatined UV spot sizze is 10 μm measured at FHMW level, and the system can generate arbitrary patterns with a minimum linewidth of 5.2 μm.

High-numerical aperture extreme ultraviolet scanner for 8-nm lithography and beyond

Current extreme ultraviolet (EUV) projection lithography systems exploit a projection lens with a numerical aperture (NA) of 0.33. It is expected that these will be used in mass production in the 2018/2019 timeframe. By then, the most difficult layers at the 7-nm logic and the mid-10-nm DRAM nodes will be exposed. These systems are a more economical alternative to multiple-exposure by 193 argon fluoride immersion scanners. To enable cost-effective shrink by EUV lithography down to 8-nm half pitch, a considerably larger NA is needed. As a result of the increased NA, the incidence angles of the light rays at the mask increase significantly. Consequently, the shadowing and the variation of the multilayer reflectivity deteriorate the aerial image contrast to unacceptably low values at the current 4× magnification. The only solution to reduce the angular range at the mask is to increase the magnification. Simulations show that the magnification has to be doubled to 8× to overcome the shadowing effects. Assuming that the mask infrastructure will not change the mask form factor, this would inevitably lead to a field size that is a quarter of the field size of the current 0.33-NA step and scan systems and reduce the throughput (TPT) of the high-NA scanner to a value below 100 wafers per hour unless additional measures are taken. This paper presents an anamorphic step and scan system capable of printing fields that are half the field size of the current full field. The anamorphic system has the potential to achieve a TPT in excess of 150 wafers per hour by increasing the transmission of the optics, as well as increasing the acceleration of the wafer stage and mask stage. This makes it an economically viable lithography solution.

Die Placement Error management for Fan out Applications using Projection Lithography

Abstract Photolithography has long been the key patterning technology for structuring organic materials used in advanced packaging applications like flip-chip wafer bumping, electroplated gold, solder bumps, copper pillar technologies and redistribution layers. Photolithography is a key manufacturing process and cost contributor, the careful selection of the right exposure solution is critical to achieve the best possible cost structure in today's industrial lithography applications We will introduce a projection exposure technology that uses a 1:1 projection lens; the projection exposure technology provides high resolution patterning performance. With the capability of varying NA from 0.07 to 0.14, a large depth of focus is obtained, that is required to ensure high pattern fidelity when working with thick resists. The projection exposure can also be applied to FOWLP applications, when the die placement data is fed into a software optimization algorithm to correct for it. We will present the projection exposure technology capability in managing the die placement error for FOWLP. In addition, details on the overlay capability of the projection exposure in thin resist are described and a Cost-of-Ownership comparison between different photolithography solutions is discussed.