纳米级电子束直写曝光的基础工艺

电子束光刻技术具有极高的分辨率，其直写式曝光系统甚至可达到几纳米的加工能力。本重点对不同的抗蚀剂、电子束／光学系统的混合光刻及邻近效应修正等技术进行了研究。     

纳米级电子束直写曝光的基础工艺

电子束光刻技术具有极高的分辨率,其直写式曝光系统甚至可达到几纳米的加工能力.本文重点对不同的抗蚀剂、电子束/光学系统的混合光刻及邻近效应修正等技术进行了研究.     

纳米级电子束直写曝光的基础工艺

电子束光刻技术具有极高的分辨率,其直写式曝光系统甚至可达到几纳米的加工能力.本文重点对不同的抗蚀剂、电子束/光学系统的混合光刻及邻近效应修正等技术进行了研究.     

电子束光刻在纳米加工及器件制备中的应用

电子束光刻技术是推动微米电子学和微纳米加工发展的关键技术,尤其在纳米制造领域中起着不可替代的作用。介绍了中国科学院微电子研究所拥有JEOLJBX5000LS、JBX6300FS纳米电子束光刻系统和电子显微镜系统的电子束光刻技术实验室,利用电子束直写系统所开展的纳米器件和纳米结构制造工艺技术方面的研究。重点阐述了如何利用电子束直写技术实现纳米器件和纳米结构的电子束光刻。针对电子束光刻效率低和电子束光刻邻近效应等问题所采取的措施;采用无宽度线曝光技术和高分辨率、高反差、低灵敏度电子抗蚀剂相结合实现电子束纳米尺度光刻以及采用电子束光刻与X射线曝光相结合的技术实现高高宽比的纳米尺度结构的加工等具体工艺技术问题展开讨论。     

电子束光刻技术与图形数据处理技术

介绍了微纳米加工领域的关键工艺技术——电子束光刻技术与图形数据处理技术,包括:电子束直写技术、电子束邻近效应校正技术、光学曝光系统与电子束曝光系统之间的匹配与混合光刻技术、电子束曝光工艺技术、微光刻图形数据处理与数据转换技术以及电子束邻近效应校正图形数据处理技术。重点推荐应用于电子束光刻的几种常用抗蚀剂的主要工艺条件与参考值,同时推荐了可以在集成电路版图编辑软件L-Edit中方便调用的应用于绘制含有任意角度单元图形和任意函数曲线的复杂图形编辑模块。     

电子束光刻三维仿真研究

本文利用Monte Carlo方法及优化的散射模型,对电子束光刻中电子在抗蚀剂中的散射过程进行了模拟,通过分层的方法,对厚层抗蚀剂不同深度处的能量沉积密度进行了计算,建立了电子束光刻厚层抗蚀剂的三维能量沉积模型。根据建立的三维能量沉积模型,采用重复增量扫描策略对正梯锥三维微结构进行了光刻仿真。理论分析和仿真结果表明,利用分层的三维能量沉积分布模型能更精确地实现电子束光刻的三维仿真。     

纳米级精细线条图形的微细加工

对分辨率极高的电子束光刻技术和高选择比、高各向异性度的ICP刻蚀技术进行了研究,形成一套以负性化学放大胶SAL-601为电子抗蚀剂的电子束光刻及ICP刻蚀的优化工艺参数,并利用这些优化参数结合电子束邻近效应校正等技术制备出剖面形貌较为清晰的30nm精细线条图形.     

纳米级精细线条图形的微细加工

对分辨率极高的电子束光刻技术和高选择比、高各向异性度的ICP刻蚀技术进行了研究,形成一套以负性化学放大胶SAL-601为电子抗蚀剂的电子束光刻及ICP刻蚀的优化工艺参数,并利用这些优化参数结合电子束邻近效应校正等技术制备出剖面形貌较为清晰的30nm精细线条图形.     

新型抗蚀剂的电子束曝光性能研究

为了满足越来越多的特殊结构纳米电子器件的制作要求,亟需进一步提高电子束光刻的分辨率与质量,选择适合的高分辨率电子束抗蚀剂材料显得尤为重要。从曝光剂量以及显影与烘烤过程中具体工艺条件的影响等方面对三种新型抗蚀剂材料HSQ,Calixarene和ARN7520进行了电子束曝光性能的研究,同时也对三者的优缺点进行了讨论。通过实验可知,三种新型抗蚀剂均有小于50 nm的高曝光分辨率。HSQ与衬底有更好的附着力,具有较高的机械强度和对比度,在小面积密集图形的制作中具有较好的性能。而ARN7520具有较高的灵敏度,受电子束邻近效应的影响较小,更适合复杂版图的制作。Calixarene虽然也具有较高的曝光分辨率,但过低的灵敏度严重限制了其实用性。     

各种光刻技术极限性能比较

本文介绍紫外线光刻、X射线光刻及电子束光刻的分辨率、套刻精度及象场尺寸的极限,但不涉及这些光刻方法的经济性比较及其在特殊薄膜器件应用方面的适用性问题。研究得出的部分结论如下:(1)在1μm线宽时,光字投影光刻的对比度可高于电子束光刻法;(2) 当线宽大于0.1μm时,X射线光刻可给出最高的对比度和抗蚀剂纵横比值,但在小于0.1μm的尺寸下,能获着最大纵横比值的则是电子束光刻技术;(3)用电子束对大面积样品曝光时,倘若抗蚀剂层很薄,则其在50nm线宽下所达到的对比度几乎和μm线宽时之值相同;(4)归根结底,在电子束光刻中,次级电子射程对分辨率的限制,完全同X射线光刻中光电子射程对分辨率所造成的限制一样。在这两种情况下,其密集图形的最小线宽和间距均约为20nm。     

Structural Transformation of Acrylic Resin upon Controlled Electron‐Beam Exposure Yields Positive and Negative Resists

Zwitter polymers are defined as polymers that undergo transformation from a linear to a crosslinked structure under electron‐beam irradiation. A resist polymer may be either linear or crosslinked, depending on electron‐beam dosage. The structural transformation of acrylic resin make it suitable for applications in positive and negative resists in the semiconductor field. The contrast ratio and threshold dose both increase with increasing resist thickness for both the positive and negative resists, while the positive resist exhibits better contrast than the negative. The intensity of the characteristic Fourier‐transform infrared absorption band at 1612 cm^–1 (vinyl group) is used to explain the phenomena behind these resist transformations. We evaluate the effects of two important processing conditions: the soft baking and post‐exposure baking temperatures. Pattern resolution decreases upon increasing the baking temperature, except for soft baking of the negative resist. The effect of electron dose on the pattern resolution is also discussed in detail for both resists. High electron‐beam exposure does not improve the etching resistance of the resist because of the porous nature of the resist that develops after high‐dosage irradiation.     

一种基于元胞自动机的显影模型

本文利用元胞自动机的方法建立电子抗蚀剂显影模型,阐述了用该模型确立电子抗蚀剂显影后轮廓的方法,在结合相应的能量沉积模型和显影速率模型后,给出了电子抗蚀剂最终显影轮廓的模拟结果,并用ZEP520电子抗蚀剂进行实验验证.     

Resist thickness effects on ultra thin HSQ patterning capabilities

This work focuses on the effect of resist thickness on resolution performance of hydrogen silsesquioxane (HSQ) electron beam resist. Contrast, sensitivity, surface morphology and resolution of the formed structures were found to be substantially dependent on film thickness. Method of resist drying in vacuum at room temperature was found to reduce surface roughness of ultra thin HSQ films compared to hot plate drying at 90 °C in air. Results of Monte Carlo simulations of the exposure process are in good agreement with proposed mechanism of sensitivity loss and structure linewidth broadening with increase of resist thickness.     

Chemical Amplification of a Triphenylene Molecular Electron Beam Resist

Molecular resists, such as triphenylene derivatives, are small carbon rich molecules, and thus give the potential for higher lithographic resolution and etch durability, and lower line width roughness than traditional polymeric compounds. Their main limitation to date has been poor sensitivity. A new triphenylene derivative molecular resist, with pendant epoxy groups to aid chemically amplified crosslinking, was synthesized and characterized. The sensitivity of the negative tone, pure triphenylene derivative when exposed to an electron beam with energy 20 keV was ～ 6 × 10^–4 C cm^–2, which increased substantially to ～ 1.5 × 10^–5 C cm^–2 after chemical amplification (CA) using a cationic photoinitiator. This was further improved, by the addition of a second triphenylene derivative, to ～ 7 × 10^–6 C cm^–2. The chemically amplified resist demonstrated a high etch durability comparable with the novolac resist SAL 601. Patterns with a minimum feature size of ～ 40 nm were realized in the resist with a 30 keV electron beam.     

Resolution, overlay, and field size for lithography systems

Resolution, overlay, and field size limits for UV, X-ray, electron beam, and ion beam lithography are described. The following conclusions emerge in the discussion. 1) At 1-µm linewidth, contrast for optical projection can be higher than that for electron beam. 2) Optical cameras using mirror optics and deep UV radiation can potentially produce linewidths approaching 0.5 µm. 3) For the purpose of comparing the resolution of electron beam and optical exposure, it is useful to define the minimum linewidth as twice the linewidth at which the contrast of the exposure system has fallen to 30 percent. 4) X-ray lithography offers the highest contrast and resist aspect ratio for linewidths above about 0.1 µm, but for dimensions below 0.1 µm, highest aspect ratio is obtained with electron beam. 5) With electron beam exposure on a bulk sample, contrast for a 50-nm linewidth is the same as that for 1-µm linewidth, provided the resist is thin. Higher accelerating voltages make it easier to correct for proximity effects and to maintain resolution with thick resist. 6) Ultimately the range of secondary electrons limits resolution in electron beam lithography, just as the range of photoelectrons limits resolution in X-ray lithography. In both cases, minimum linewidth and spacing in dense patterns is about 20 nm. Resolution with ion beams will probably be about the same because the interaction range of the ions will be similar to the electrons.     

Computer-controlled resist exposure in the scanning electron microscope

In modern microelectronics, complicated structures with very small dimensions must be fabricated on active-device materials. This task has been traditionally accomplished by photolithographic techniques, but electron-beam exposure of resist materials has recently been explored [1]-[3]. Submicron electron devices have been fabricated in several laboratories, often featuring a flying-spot scanner to generate the pattern being exposed [4]-[7]. Paper tape drives have been used for repetitive patterns [8], and computer control of the electron beam has been reported also [1], [9]. The electron resist that has shown the highest resolution to date appears to be poly-(methyl methacrylate) (PMM). We have used this material in a resist form for microelectronic device fabrication, and in bulk form to determine energy dissipation profiles. The exposure is performed with a computer-controlled scanning electron microscope (CCSEM). In this paper, we describe the electron beam system briefly, discuss the processes involved in resist exposure and development, describe our exposure procedures using the CCSEM, and show results of fabricated devices and energy dissipation studies.     

Zinc-Imidazolate Films as an All-Dry Resist Technology

Motivated by the drawbacks of solution phase processing, an all-dry resist formation process is presented that utilizes amorphous zinc-imidazolate (aZnMIm) films deposited by atomic/molecular layer deposition (ALD/MLD), patterned with electron beam lithography (EBL), and developed by novel low temperature (120 °C) gas phase etching using 1,1,1,5,5,5-hexafluoroacetylacetone (hfacH) to achieve well-resolved 22 nm lines with a pitch of 30 nm. The effects of electron beam irradiation on the chemical structure and hfacH etch resistance of aZnMIm films are investigated, and it is found that electron irradiation degrades the 2-methylimidazolate ligands and transforms aZnMIm into a more dense material that is resistant to etching by hfacH and has a C:N:Zn ratio effectively identical to that of unmodified aZnMIm. These findings showcase the potential for aZnMIm films to function in a dry resist technology. Sensitivity, contrast, and critical dimensions of the patterns are determined to be 37 mC cm⁻², 0.87, and 29 nm, respectively, for aZnMIm deposited on silicon substrates and patterned at 30 keV. This work introduces a new direction for solvent-free resist processing, offering the prospect of scalable, high-resolution patterning techniques for advanced semiconductor fabrication processes.     

Enhancement of resist plasma erosion rates by electron-beam hardening

A nonthermal method of hardening positive photoresists by means of a scanned high-energy electron beam in preference to direct resist heating is described. It has been established that moderate electron doses produce significant resist cross-linking without flow. Plasma etch resistance can be enhanced in the resists with no degradation of the as-developed line profile.     

Metal lift-off using a trilevel resist system for electron beam lithography

Multilayer resist optical lithography is transposed into trilevel resist electron beam lithography. A thin electron-sensitive multilayer resist is exposed in a dedicated scanning transmission electron microscope. The upper resist layer is chemically developed, the underlying layers are patterned by reactive ion etching. Very fine titanium lines (1 μm to 30 nm) are obtained after evaporation and lift-off process.