波前分割无掩模激光干涉光刻的实现方法

激光干涉光刻不受传统光学光刻系统光源和数值孔径的限制,其极限尺寸CD达到曝光波长 的1/4,研究了波前分割双光束、三光束方法及四光束无掩模激光干涉光刻方法,提出了可用于五光束和多种多光束和多次曝光的梯形棱镜波前分割干涉光刻方法。用自行建立的梯形棱镜波前分割系统进行了多光束干涉曝光实验,得到孔尺寸约220nm的阵列图形。     

双光束双曝光与四光束单曝光干涉光刻方法的比较

双光束双曝光和四光束单曝光是无掩模激光干涉光刻的两种典型方法,都容易利用现有光刻工艺,在不需掩模和高精度光刻物镜的情况下,用简单廉价光学系统在大视场和深曝光场内形成孔阵、点阵或锥阵等周期性图形。双光束双曝光法得到的阵列图形周期极限为λ/2;四光束单曝光的周期略大,为前者的2倍。模拟和实验结果表明,通过控制曝光和显影工艺,双光束双曝光较四光束单曝光能更灵活地得到孔阵或点阵,而四光束单曝光得到的图形孔与孔之间没有鞍点,较双光束双曝光形成的孔侧壁更陡。这两种方法在需要在大面积范围内形成孔或点这类周期阵列图形的微电子和光电子器件的制造领域有很好的应用前景。     

制作光纤光栅的相移掩模-双光束干涉曝光方法

介绍将无铬相移掩模技术和双光束干涉曝光技术用于制作纳米级图形光纤光栅的基本原 理和实验系统设计。提出一种用可移动反射镜使写入光束扫描固定在一起的相移掩模和光纤组合体制作光纤光栅的方法,既便于系统调整,增强曝光能量,又可方便制作高分辨力、长尺寸光纤光栅,无论是周期光栅,还是非周期光栅。     

振幅分割无掩模激光干涉光刻的实现方法

无掩模激光干涉光刻中的分束方法一般有波前分割和振幅分割。研究和比较了振幅分割无 掩模激光干涉光刻方法和系统,包括振幅分割双光束干涉系统、三光束干涉系统、液浸式深紫外干涉系统及全自动干涉光刻系统。建立了双光束双曝光干涉光刻实验系统。模拟和实验结果表明,对点阵或孔阵图形,在同样的图形尺度下,无掩模干涉光刻比传统光刻简单得多。     

采用双向偏置曝光的成像干涉光刻技术

成像干涉光刻技术(IIL)具有干涉光刻技术(IL)的高分辨力和光学光刻技术(OL)产生任意形状集成电路特征图形的能力。在IIL中,按掩模图形的不同空间频率成份分区曝光,并使其在抗蚀剂基片上非相干叠加,得到高分辨抗蚀剂图形。本文在研究一般三次曝光IIL原理基础上,提出采用沿X轴正、负方向以及沿Y轴正、负方向偏置的双向偏置照明,分别曝光 X方向、-X方向、 Y方向、-Y方向的高空间频率分量并与垂直于掩模方向的低空间频率分量曝光相结合的五次曝光IIL。理论和计算模拟表明,该方法可以提高图形对比度和分辨力,并减小因调焦误差引起的图形横向位移误差,有利于改善抗蚀剂图形质量。     

成像干涉光刻技术及其频域分析

传统光学光刻技术(OL)由于其固有的限制,虽然可对任意图形成像,但分辨力较低。无掩模激光干涉光刻技术(IL)的分辨力可达l /4,却局限于周期图形。成像干涉光刻技术(IIL)结合了二者的优点,用同一个系统分次传递物体不同的空间频率,能更有效地传递物体的信息,以高分辨力对任意图形成像。初步模拟研究表明,在同样的曝光波长和数值孔径下,对同样特征尺寸的掩模图形,IIL得到的结果好于OL。在CD=150nm时,IIL相对于OL把分辨力提高了1.5倍多。     

用于大面积周期性图形制造的激光干涉光刻

用两束或多束相干激光束以不同的组合形式对光致抗蚀剂曝光,可在大面积范围内产生精细的二维周期性图形,这个方法特别适合于产生光电子器件和生电子器件的周期性结构。介绍激光干涉光刻的基本原理,对几种光束组合干涉方法给出了理论推导结果,并进行了计算机模拟。初步的实验结果表明,用激光干扰光刻技术产生大面积的亚微米级周期性孔、柱、锥图形是可行的。该方法不需要掩模、昂贵的光刻成像透镜、新的短波长光源和新型的抗蚀剂,提供了得到高分辨、无限焦深、大面积光刻的可能性。     

全息剪切干涉法测量透镜几何象差

本文用全息双频光栅剪切干涉装置对透镜几何象差的测量进行实验研究。将象差光束中两剪切干涉光线的交点看成点源,提出了用经典杨氏干涉观点、由剪切条纹图确定这些交点的空间位置而直接得到几何象差的杨氏条纹分析法。对几个透镜的象差作了测量和分析;与设计理论值作比较,二者符合良好。     

四个干涉图法的双曝光全息干涉术测物体变形

本文用Ar~+激光器作光源,BSO晶体作记录介质,电视-微机系统作探测器,把四个干涉图法应用到双曝光全息干涉术上,从而实现了全息干涉图的自动计算,获得表面变形的大小、方向和形状的全信息。为验证该法的实用性,测试了薄板受应力后变形情况。     

长度计量基础知识讲座(三十四)

第三十四讲干涉显微镜1结构和工作原理干涉显微镜(以下简称仪器)主要由主体、工作台、干涉头、测微目镜、照明系统和摄影系统等部分组成。图1为常用的双光束干涉显微镜的结构形式。仪器基于等厚干涉测量平面度的原理,将同一光源发出的光线分为两束或多束,使其产生干涉。显微镜系统将干涉条纹放大,根据干涉条纹的间距     

Investigation on fabrication of nanoscale patterns using laser interference lithography

Nanoscale patterns are fabricated by laser interference lithography (LIL) using Lloyd's mirror interferometer. LIL provides a patterning technology with simple, quick process over a large area without the usage of a mask. Effects of various key parameters for LIL, with 257 nm wavelength laser, are investigated, such as the exposure dosage, the half angle of two incident beams at the intersection, and the power of the light source for generating one or two dimensional (line and dot) nanoscale structures. The uniform dot patterns over an area of 20 mm x 20 mm with the half pitch sizes of around 190, 250, and 370 nm are achieved and by increasing the beam power up to 0.600 mW/cm2, the exposure process time was reduced down to 12/12 sec for the positive photoresist DHK-BF424 (DongJin) over a bare silicon substrate. In addition, bottom anti-reflective coating (DUV-30J, Brewer Science) is applied to confirm improvements for line structures. The advantages and limitations of LIL are highlighted for generating nanoscale patterns.     

Investigation of the effects of bottom anti-reflective coating on nanoscale patterns by laser interference lithography

Enhanced resolution of the structures can be achieved by employing the bottom anti-reflective coating (BARC) material in laser interference lithography process. The purpose of the BARC is to control the reflection of light at the surface of the wafer to minimize the effects caused by reflection. Lloyd's mirror interferometer is utilized for the experiment with 257 nm wavelength Ar-Ion laser used as the light source to generate one-dimensional nanoscale patterns. By adjusting reflectivity through application of the BARC material, scattering of the patterns are reduced. The effects of BARC material are explored to confirm the reduction of the vertical standing wave, which is the main cause of undesirable nanoscale patterns. It is also highlighted that improvements through utilization of BARC material enables smaller pattern size with a set pitch size by controlling the exposure energy.     

Simple technique for the measurement of two-dimensional linear retardation distributions of wave plates with a phase-shifting Nomarski prism

What we believe to be a new technique for the measurement of two-dimensional retardation distributions of a wave plate (WP) is presented. Phase-shifting interferometry has been applied for determining the relative retardation distribution using a Nomarski prism (NP) as a phase shifter. Absolute retardation distribution is obtained by accurately determining the position of zero retardation in the interference field using white light interference fringes and adjusting the phase distribution with respect to the zero retardation position. The measured absolute retardation distribution of the NP is subtracted from that obtained for the combination of the WP and NP, to get the desired retardation distributions for the WP. The technique is suitable for the measurement of phase retardation of both single and multiple order WPs, as the actual phase retardation distributions are obtained. Results obtained for WPs are presented.     

Fabrication of 380 nm ultra violet light emitting diodes on nano-patterned n-type GaN substrate

380 nm ultraviolet (UV) light emitting diodes (LEDs) were grown on patterned n-type GaN substrate (PNS) with silicon dioxide (SiO2) nano pattern to improve the light output efficiency. Wet etched self assembled indium tin oxide (ITO) nano clusters serves as dry etching mask for converting the SiO2 layer grown on n-GaN template into SiO2 nano patterns by inductively coupled plasma etching. Three different diameter of ITO such as 200, 250 and 300 nm were used for SiO2 nano pattern fabrication. PNS is obtained by n-GaN regrowth on SiO2 nano patterns and UV LEDs were grown on PNS template by MOCVD. Enhanced light output intensity was observed by employing SiO2 nano patterns on n-GaN. Among different PNS UV LEDs, LED grown on PNS with 300 nm ITO diameter showed enhancement in light output intensity by 2.1 times compared to the reference LED without PNS.     

Real-time single-molecule imaging of quantum interference

The observation of interference patterns in double-slit experiments with massive particles is generally regarded as the ultimate demonstration of the quantum nature of these objects. Such matter-wave interference has been observed for electrons, neutrons, atoms and molecules and, in contrast to classical physics, quantum interference can be observed when single particles arrive at the detector one by one. The build-up of such patterns in experiments with electrons has been described as the "most beautiful experiment in physics". Here, we show how a combination of nanofabrication and nano-imaging allows us to record the full two-dimensional build-up of quantum interference patterns in real time for phthalocyanine molecules and for derivatives of phthalocyanine molecules, which have masses of 514?AMU and 1,298?AMU respectively. A laser-controlled micro-evaporation source was used to produce a beam of molecules with the required intensity and coherence, and the gratings were machined in 10-nm-thick silicon nitride membranes to reduce the effect of van der Waals forces. Wide-field fluorescence microscopy detected the position of each molecule with an accuracy of 10?nm and revealed the build-up of a deterministic ensemble interference pattern from single molecules that arrived stochastically at the detector. In addition to providing this particularly clear demonstration of wave-particle duality, our approach could also be used to study larger molecules and explore the boundary between quantum and classical physics.     

Direct writing of large-area plasmonic photonic crystals using single-shot interference ablation

We report direct writing of metallic photonic crystals (MPCs) through a single-shot exposure of a thin film of colloidal gold nanoparticles to the interference pattern of a single UV laser pulse before a subsequent annealing process. This is defined as interference ablation, where the colloidal gold nanoparticles illuminated by the bright interference fringes are removed instantly within a timescale of about 6 ns, which is actually the pulse length of the UV laser, whereas the gold nanoparticles located within the dark interference fringes remain on the substrate and form grating structures. This kind of ablation has been proven to have a high spatial resolution and thus enables successful fabrication of waveguided MPC structures with the optical response in the visible spectral range. The subsequent annealing process transforms the grating structures consisting of ligand-covered gold nanoparticles into plasmonic MPCs. The annealing temperature is optimized to a range from 250 to 300?°C to produce MPCs of gold nanowires with a period of 300 nm and an effective area of 5 mm in diameter. If the sample of the spin-coated gold nanoparticles is rotated by 90° after the first exposure, true two-dimensional plasmonic MPCs are produced through a second exposure to the interference pattern. Strong plasmonic resonance and its coupling with the photonic modes of the waveguided MPCs verifies the success of this new fabrication technique. This is the simplest and most efficient technique so far for the construction of large-area MPC devices, which enables true mass fabrication of plasmonic devices with high reproducibility and high success rate.     

Coherently controlled ballistic charge currents injected in single-walled carbon nanotubes and graphite

Ballistic electrical currents are optically injected into aligned single-walled carbon nanotubes and bulk graphite at 300 K via quantum interference between single and two photon absorption of phase-related 700 and 1400 nm, 150 fs pulses. The transient currents are detected via the emitted terahertz radiation. Optical phase and power dependence are consistent with the quantum interference optical process. Under similar excitation conditions, the peak current for a forest of nanotubes, with a diameter distribution of approximately 2.5 +/- 1.5 nm, is 9 +/- 1 times larger than that in graphite. At peak focused intensities of 10 GW cm(-2) (1400 nm) and 0.15 GW cm(-2) (700 nm), the peak current is approximately 1 nA per nanotube. The peak current for pump light polarized along the tubes is approximately 3.5 times higher than that for light polarized perpendicular to the tubes.     

Directed placement of gold nanorods using a removable template for guided assembly

We have used a temperature sensitive polymer film as a removable template to position, and align, gold nanorods onto an underlying target substrate. Shape-matching guiding structures for the assembly of nanorods of size 80 nm × 25 nm have been written by thermal scanning probe lithography. The nanorods were assembled into the guiding structures, which determine both the position and the orientation of single nanorods, by means of capillary interactions. Following particle assembly, the polymer was removed cleanly by thermal decomposition and the nanorods are transferred to the underlying substrate. We have thus demonstrated both the placement and orientation of nanorods with an overall positioning accuracy of ≈10 nm onto an unstructured target substrate.     

Optical impedance matching using coupled plasmonic nanoparticle arrays

Silver nanoparticle arrays placed on top of a high-refractive index substrate enhance the coupling of light into the substrate over a broad spectral range. We perform a systematic numerical and experimental study of the light incoupling by arrays of Ag nanoparticle arrays in order to achieve the best impedance matching between light propagating in air and in the substrate. We identify the parameters that determine the incoupling efficiency, including the effect of Fano resonances in the scattering, interparticle coupling, as well as resonance shifts due to variations in the near-field coupling to the substrate and spacer layer. The optimal configuration studied is a square array of 200 nm wide, 125 nm high spheroidal Ag particles, at a pitch of 450 nm on a 50 nm thick Si(3)N(4) spacer layer on a Si substrate. When integrated over the AM1.5 solar spectral range from 300 to 1100 nm, this particle array shows 50% enhanced incoupling compared to a bare Si wafer, 8% higher than a standard interference antireflection coating. Experimental data show that the enhancement occurs mostly in the spectral range near the Si band gap. This study opens new perspectives for antireflection coating applications in optical devices and for light management in Si solar cells.