掩模版复印工艺图形畸变分析与改进

批量化、低成本的掩模版复印工艺常被用于LED领域。在微米级图形的掩模版复印工艺中,受玻璃基板平面度的影响,光学衍射效应会导致图形发生畸变。为消弭复印工艺中的图形畸变,从光学衍射理论展开分析,提出通过调整光刻曝光剂量和光刻胶层厚度来提升掩模版复印工艺水平的方法。实验实现了4μm圆形图形掩模版的复印制作,结果表明该方法可以显著提升微米级图形的掩模版复印工艺水平,降低掩模版的制作成本。     

微透镜列阵成像光刻技术

介绍了一种利用微透镜列阵投影成像光刻的周期微纳结构加工方法.该方法采用商业打印机在透明薄膜上打印的毫米至厘米尺寸图形为掩模,以光刻胶作为记录介质,以微透镜列阵为投影物镜将掩模缩小数千倍成像在光刻胶上,曝光显影后便可制备出微米、亚微米特征尺寸的周期结构列阵.基于该方法建立了微透镜列阵成像光刻系统,并以制备800 nm线宽、50 mm×50 mm面积的图形列阵为例,实现了目标图形的光刻成形,曝光时间仅为几十秒,图形边沿粗糙度低于100 nm.该方法系统结构简单、掩模制备简易、曝光时间短;为周期微纳结构的低成本、高效率制备提供了有效途径.     

声表面波器件光刻的衍射效应研究

声表面波(SAW)器件光刻过程中,制作的光刻胶线条宽度与掩模版不一致,特别是不同宽度的非均匀线条光刻后线宽变化值存在偏差.该文研究了接近式曝光衍射效应对线宽的影响,分析了掩模版上线条和缝隙宽度、衍射光强、掩模版与光刻胶间距等参数间的关系.结果表明,通过建立光学模型给出了计算曝光后不同线条宽度变化值的方法,采用程序编程可...     

光刻胶在二元光学元件制作工艺中的行为研究

采用大规模集成电路的多次掩模光刻和刻蚀技术制作二元光学元件阵列是较为传统和实用的制作方法,其工艺过程主要包括:利用光刻技术将设计的掩模版图形转印到有光刻胶的衬底表面;利用刻蚀技术将光刻胶的图形转移到衬底表面,形成所需的表面浮雕结构.在工艺中,光刻胶的行为和特性对衬底的最终图形有着极为重要的作用.光刻和刻蚀两道工序都要求实际图形与掩模版的图形达到很高的一致性,这样才能实现元件被高保真地制作到衬底上.在整个工艺过程中,由于不同光刻胶在甩胶、前烘、曝光、显影、坚膜、刻蚀或腐蚀等工艺中表现不同的行为特性:附着性、均匀性、边缘效应、分辨率、感光度、高温形变、耐刻蚀性等等,使得所制作的器件性能有较大的区别.本文详细研究了不同光刻胶在不同工艺过程中的行为.在二元光学元件的制作中,通过选用不同的光刻胶:在第一次光刻刻蚀台阶较深时,选择粘度系数较大,高感光度,耐刻蚀的厚胶;在套刻中,刻蚀台阶较浅时,选用高分辨率、高陡直度、耐高温的薄胶,最终制作出了性能良好的二元光学元件.(OD2)     

硅基超疏水跨尺度微纳结构的制备北大核心

提出了一种可行的制备超疏水跨尺度微纳结构的方法,该方法基于衍射干涉光刻技术,制备出拥有跨尺度的光刻胶结构阵列。建立衍射干涉光刻模型,采用严格耦合波分析(RCWA)方法对衍射干涉形成的光强分布进行理论分析;通过衍射干涉光刻技术制备出跨尺度微纳光刻胶阵列。最后用ICP-Bosch干法刻蚀工艺,将跨尺度光刻胶结构转移到硅基底上,制备出高深宽比硅管状结构,其顶部是跨尺度微纳锥形结构,利用接触角测量仪对制备的样品表面的浸润性能进行了测试,测试结果表明该跨尺度微纳结构达到超疏水性能。     

光刻胶回流技术

本文介绍了集成电路制作过程中,采用光刻胶回流技术,提高抗蚀能力和图形边缘整齐度,以获得硅片上的光刻图形与掩模版图形几何尺寸一致性很好的效果,达到电路参数一致性好和提高电路管芯成品率的目的。同时介绍了光刻胶回流的实验条件,以及如何掌握与控制好光刻胶回流的工艺技术要点。     

大规模集成电路掩版模的检查与质量分析

在大规模集成电路的制造中,掩模版的特点是:1)掩模必须是分层作图,且每层之间的掩模图形按设计要求套刻;2)、掩模的图形尺寸变化应控制在设计的一定容差范围;3)掩模图形内的任何缺陷,都会导致电学的穿通或错误连结,所以对缺陷尺寸、位置及密度都有严格要求;4)掩模图形本身的质量,包括黑白反差和边缘锐度等等将会影响光刻工艺质量,这也是对掩模要求着眼点之一,…….     

亚微米光栅曝光系统的应用及设备关键技术研究

半导体工艺中的光刻是芯片制造中最关键的工艺。DFB半导体激光器的腔体结构与普通半导体激光器的腔体结构不同,需要制作周期光栅,光栅周期为亚微米数量级;鉴于亚微米光栅曝光系统在半导体激光器的应用需求,瑞士一家公司研制了一款专用于亚微米周期光栅的设备Phabler 100M DUV光刻机;本系统采用了非线性晶体的倍频效应和周期性光栅的泰伯效应。这些关键技术用较低的成本实现了极高的分辨率,可以制作周期性光栅并达到100 nm的线条分辨率;掩模版和晶片的不平行将造成光刻线条的不均匀,应用CCD探测器和计算机相结合的办法是做平行度的关键调试。     

激光直写系统制作掩模和器件的工艺

激光直写系统是国际上９０年代制作集成电路光刻掩模版的新型专用设备。微细加工光学技术国家重点实验室从加拿大引进了国内第一台激光直写系统。利用这台系统,通过高精度激光束在光致抗蚀剂上扫描曝光,将设计图形直接转移到掩模或硅片上。激光直写系统的应用,可以分成一次曝光制作光刻掩模和多次套刻曝光制作器件两个方面。介绍使用激光直写系统制作光刻掩模和套刻器件的具体工艺,并给出利用激光直写工艺做出的一些掩模和器件的实例     

同步辐射软X射线曝光工艺研究

本文介绍利用北京正负电子对撞机同步辐射软X射线光刻装置进行亚微米X射线光刻技术和深结构光刻的实验研究。通过对曝光剂量、掩模、抗蚀剂等工艺实验,初步得到适合于目前条件的较好的同步辐射X射线光刻工艺条件,并光刻出0.3μm的亚微米图形和抗蚀剂厚度为36μm深光刻图形。     

Improving resolution in photolithography with a phase-shifting mask

The phase-shifting mask consists of a normal transmission mask that has been coated with a transparent layer patterned to ensure that the optical phases of nearest apertures are opposite. Destructive interference between waves from adjacent apertures cancels some diffraction effects and increases the spatial resolution with which such patterns can be projected. A simple theory predicts a near doubling of resolution for illumination with partial incoherence σ < 0.3, and substantial improvements in resolution for σ < 0.7. Initial results obtained with a phase-shifting mask patterned with typical device structures by electron-beam lithography and exposed using a Mann 4800 10X tool reveals a 40-percent increase in usuable resolution with some structures printed at a resolution of 1000 lines/mm. Phase-shifting mask structures can be used to facilitate proximity printing with larger gaps between mask and wafer. Theory indicates that the increase in resolution is accompanied by a minimal decrease in depth of focus. Thus the phase-shifting mask may be the most desirable device for enhancing optical lithography resolution in the VLSI/VHSIC era.     

Spatial frequency doubling lithography (SFDL) of periodicstructures for integrated optical circuit technology

A novel technique for fabricating gratings useful for integrated optical circuits (IOCs) is described. The technique combines optical projection lithography, partially coherent illumination, and spatial filtering. With this technique, only the first two orders diffracted by the mask grating are allowed to pass through the lens. This produces a grating pattern in the image plane that has a high contrast (near 100%), a large depth of focus, and a period half of what would have been obtained in normal imaging. Gratings of different periods, sizes, locations, orientations, and configurations (chirped, phase-shifted, etc.) can all be produced on the same chip with a single exposure. Using a deep UV lens with 248-nm KrF excimer laser for illumination, the authors printed high-quality 0.5-μm period gratings in an oxide layer on 10 mm×10 mm silicon chips. Extended depth of focus was observed. This technique opens up the possibility of high-volume production of IOC chips with Bragg filters using standard IC fabrication facilities     

Two-Laser Lithography Shrinks Transistors on the Cheap

Engineers are near the outer limits of what can be done with optical lithography, the process by which light shone through a patterned mask defines the fine structures of microprocessors and memory chips. Now three teams of optics experts have independently hit upon what could turn out to be a way to extend optical lithography?s use?and, what?s even more critical, to do it cheaply.     

基于离散抽样加密算法的衍射光学元件设计

为满足浸没式光刻照明系统对掩模面高均匀性和不同照明模式的要求,对照明系统中的照明模式变换器进行了研究。采用衍射光学元件（Diffractive Optical Elements,DOE）来产生各种照明模式,从光栅结构出发,经两步变换分析了光栅转变为DOE的过程。并提出一种离散抽样加密算法,以抽样线宽1~5 m的四极照明DOE为例,揭示了DOE特征尺寸、衍射效率和光强分布非均匀性的实际对应关系。设计结果表明:随着抽样线宽的减小,整形光束的衍射效率和均匀性将得到较大提高。利用接触式光刻工艺完成了特征尺寸为1.76 m1.76 m的16台阶照明模式变换DOE的制作,通过搭建光学测试平台对不同照明模式下DOE的光强非均匀性和衍射效率进行了测试,结果满足设计要求,验证了离散抽样加密算法能够有效指导照明模式变换系统DOE的设计。     

External Cavity Lasers Composed of Higher Order Gratings and SLDs Integrated on PLC Platform

Very compact 4‐channel 200‐GHz‐spacing external cavity lasers (ECLs) were fabricated by hybrid integration of reflection gratings and superluminescent laser diodes on a planar lightwave circuit chip. The fifth‐order gratings as reflection gratings were formed using a conventional contact‐mask photo‐lithography process to achieve low‐cost fabrication. The lasing wavelength of the fabricated ECLs matched the ITU grid with an accuracy of ×0.1 nm, and optical powers were more than 0.4 mW at the injection current of 80 mA for all channels. The ECLs showed single mode operations with more than 30 dB side lobe suppression.     

Mask Design for Optical Microlithography—An Inverse Imaging Problem

In all imaging systems, the forward process introduces undesirable effects that cause the output signal to be a distorted version of the input. A typical example is of course the blur introduced by the aperture. When the input to such systems can be controlled, prewarping techniques can be employed which consist of systematically modifying the input such that it (at least approximately) cancels out (or compensates for) the process losses. In this paper, we focus on the optical proximity correction mask design problem for "optical microlithography," a process similar to photographic printing used for transferring binary circuit patterns onto silicon wafers. We consider the idealized case of an incoherent imaging system and solve an inverse problem which is an approximation of the real-world optical lithography problem. Our algorithm is based on pixel-based mask representation and uses a continuous function formulation. We also employ the regularization framework to control the tone and complexity of the synthesized masks. Finally, we discuss the extension of our framework to coherent and (the more practical) partially coherent imaging systems     

Mask design for optical microlithography--an inverse imaging problem.

In all imaging systems, the forward process introduces undesirable effects that cause the output signal to be a distorted version of the input. A typical example is of course the blur introduced by the aperture. When the input to such systems can be controlled, prewarping techniques can be employed which consist of systematically modifying the input such that it (at least approximately) cancels out (or compensates for) the process losses. In this paper, we focus on the optical proximity correction mask design problem for "optical microlithography," a process similar to photographic printing used for transferring binary circuit patterns onto silicon wafers. We consider the idealized case of an incoherent imaging system and solve an inverse problem which is an approximation of the real-world optical lithography problem. Our algorithm is based on pixel-based mask representation and uses a continuous function formulation. We also employ the regularization framework to control the tone and complexity of the synthesized masks. Finally, we discuss the extension of our framework to coherent and (the more practical) partially coherent imaging systems.     

Level-specific lithography optimization for 1-Gb DRAM

A general level-specific lithography optimization methodology is applied to the critical levels of a 1-Gb DRAM design at 175- and 150-nm ground rules. This three-step methodology-ruling out inapplicable approaches by physical principles, selecting promising techniques by simulation, and determining actual process window by experimentation-is based on process latitude quantification using the total window metric. The optimal lithography strategy is pattern specific, depending on the illumination configuration, pattern shape and size, mask technology, mask tone, and photoresist characteristics. These large numbers of lithography possibilities are efficiently evaluated by an accurate photoresist development bias model. Resolution enhancement techniques such as phase-shifting masks, annular illumination and optical proximity correction are essential in enlarging the inadequate process latitude of conventional lithography     

A new role for e-beam: electron projection

In the Scalpel system, a wide beam of electrons replaces light as the means of wafer exposure, and throughput is aided by a step-and-scan approach. One of the leading candidates for next generation lithography is Scalpel, which stands for scattering with angular limitation projection electron-beam lithography. Scalpel is a reduction image-projection technique that relies on 100 keV electrons and the contrast caused when they are scattered. The use of electrons gets round the diffraction limitation of optical lithography. The mask consists of a membrane with a low atomic number, covered with a layer of material with a high atomic number, in which the pattern is delineated. The mask is almost completely transparent to electrons at 100 keV, but contrast is generated from the difference in electron scattering characteristics between the membrane and patterned material. The membrane scatters electrons weakly and to small angles, while the patterned layer scatters them strongly and at large angles. An aperture in the back-focal plane (pupil) of the projection optics blocks the strongly scattered electrons, forming a high-contrast aerial image at the wafer plane. The functions of contrast generation and energy absorption are thus divided between mask and aperture. This division of labor means that very little of the incident energy is actually absorbed by the mask, which therefore is almost immune to thermal instabilities     

Blazed diffraction gratings fabricated using X-ray lithography: fabrication, modeling and simulation

Diffraction gratings are used in optical communications devices, spectrographs, optical scanners, monochromators, and in other instances. Diffraction gratings are either transmission or reflection. Reflective gratings are, usually, either ruled or holographic. Blazed gratings (step-echelette or phase gratings) are non-planar gratings. We present the fabrication of blazed diffraction gratings using X-ray lithography. We model, theoretically, the development process of X-ray exposed X-ray sensitive resist material (polymethyl methacrylate), and we establish a simulation algorithm, the ray-tracing algorithm based on the Hamilton–Jacobi equation. Theoretical predictions based on simulation results validate fully the fabricational results.