基于水平集方法的离子束刻蚀碲镉汞的轮廓演变模拟

用水平集方法建立了碲镉汞的离子束刻蚀轮廓的数值模型,模型的输入参数包括掩膜厚度、掩膜侧壁倾角、掩膜沟槽宽度、离子束散角、刻蚀速度等参数.对碲镉汞的刻蚀轮廓和刻蚀速度减缓现象进行了模拟和实验验证,结果表明,在沟槽宽度为4～10μm的范围内,计算得到的刻蚀深度和SEM测量结果相差6～20%.对掩膜的轮廓演变进行了模拟,给出了一个优化设计掩膜厚度来提高深宽比的实例.     

等离子体刻蚀工艺中的OES监控技术

采用光学发射光谱(OES)原位检测技术,对等离子体刻蚀机中的等离子体状态进行实时监控,讨论了其在故障诊断、分类、刻蚀终点的判断及控制方面的应用。实验平台为在新研发的高密度等离子体刻蚀机,采用化学气体HBr/Cl₂为刻蚀气体进行多晶硅刻蚀工艺实验,实验过程中所采集的OES数据通过PCA法进行分析,得到与刻蚀过程相关的特征谱线。实验结果表明：OES技术适合于深亚微米等离子体刻蚀工艺过程的终点检测及故障诊断。最后就OES技术未来发展面临的挑战进行了讨论。     

超微细加工与等离子体技术

等离子体刻蚀是基于辉光放电低温低电离等离子体中的激活中性粒子(基团)与固体表面产生化学反应。由于原子团在等离子体中作随机运动,所以成为各向同性刻蚀,难以得出高精度的微细图形。在用平行平板型刻蚀装置在低气压下工作的情况下,反应性离子被电极表面附近形成的自偏压所加速,产生物理反应与化学反应,可以产生各向异性和选择性刻蚀。用这种方法,可能形成高精度的微细图形。     

ICP技术在化合物半导体器件制备中的应用

介绍了ICP刻蚀工艺技术原理和在化合物半导体器件制备中的应用,包括ICP刻蚀技术中的低温等离子体的形成机理、等离子体与固体表面的相互作用等,并对影响ICP刻蚀结果的因素进行了分析.研究了不同的工艺气体配比、腔体工作压力、ICP源功率和射频源功率对刻蚀的影响,并初步得到了一种稳定、刻蚀表面清洁光滑、图形轮廓良好、均匀性较好和刻蚀速率较高的干法刻蚀工艺.     

碲镉汞深微台面列阵干法隔离的轮廓研究

文章报道了碲镉汞（HgCdTe）深微台面列阵干法隔离的轮廓研究的初步结果。采用诱导耦合等离子体（ICP）增强反应离子刻蚀（RIE）技术获得的HgCdTe深微台面列阵，在金刚刀解理后，通过扫描电子显微镜（SEM）观察了其干法刻蚀图形的剖面轮廓。进一步研究了刻蚀时间和刻蚀槽开口宽度对刻蚀图形轮廓的影响，获得了一些有助干深微台面芯片工艺设计的实验结果。     

高纵横选择比低损伤多晶硅栅的工艺实现

分析了采用微波高密度等离子体刻蚀(HDP)系统刻蚀实现高纵横向刻蚀选择比、低等离子体损伤、精细线条尺寸的MOSFET多晶硅栅的可行性。研究了刻蚀用气体中CH4和SF6等离子体分别在多晶硅栅刻蚀当中的作用及其分别对刻蚀速率、多晶硅栅侧壁形貌的影响原理。提出了实现MOSFET多晶硅栅高速低损伤刻蚀及聚合物清洗相结合的两步刻蚀工艺技术。借助终点检测技术(EPD),通过优化各气体体积流量及合理选择两步刻蚀时间较好实现了较高的纵横向选择比、低刻蚀损伤及精细线条的MOSFET多晶硅栅刻蚀。     

感应耦合等离子体干法刻蚀锑化铟薄膜研究

应用感应耦合等离子体技术首次实现了对锑化铟薄膜的干法刻蚀。朗缪尔探针诊断结果表明 :射频电源功率为 2 0 0 W时 ,在刻蚀样品附近的等离子体离子密度最大达 6.71 70× 1 0 1 0 cm- 3。以 CCl F2 为刻蚀气体 ,进气流量 2 m L/min,RF功率 2 0 0 W,等离子体反应刻蚀运行气压 7.98Pa时 ,对 In Sb-In薄膜进行了感应耦合等离子体干法刻蚀 ,获得刻蚀图形 ,宽深比为 5     

InGaAs探测器制备的ICP刻蚀方法研究

采用Cl2/BCl3/Ar感应耦合等离子体对InP/In0.55Ga0.45As/InP进行了刻蚀。讨论了不同的气体组分、ICP功率、直流自偏压下对刻蚀速率、表面粗糙度的影响。初步得到了一种稳定、刻蚀表面清洁光滑、图形轮廓良好、均匀性好和刻蚀速率较高的工艺。利用此工艺制作的8元InP/In0.55Ga0.45As/InP(PIN)探测器,峰值探测率为1.04×1012cmHz1/2W-1。     

先进CMOS器件中poly-Si/TaN/HfSiON栅结构的干法刻蚀研究

研究了先进CMOS器件中poly-Si/TaN/HfSiON栅结构的干法刻蚀工艺。对于poly-Si/TaN/HfSiON栅结构的刻蚀,我们采用的策略是对栅叠层中的每一层都进行高选择比地、陡直地刻蚀。首先,对于栅结构中poly-Si的刻蚀,开发了一种三步的等离子体刻蚀工艺,不仅得到了陡直的poly-Si刻蚀剖面而且该刻蚀可以可靠地停止在TaN金属栅上。然后,为了得到陡直的TaN刻蚀剖面,研究了多种BCl3基刻蚀气体对TaN金属栅的刻蚀,发现BCl3/Cl2/O2/Ar等离子体是合适的选择。而且,考虑到Cl2对Si衬底几乎没有选择比,采用优化的BCl3/Cl2/O2/Ar等离子体陡直地刻蚀掉TaN金属栅以后,我们采用BCl3/Ar等离子体刻蚀HfSiON高K介质,改善对Si衬底的选择比。最后,采用这些新的刻蚀工艺,成功地实现了poly-Si/TaN/HfSiON栅结构的刻蚀,该刻蚀不仅得到了陡直的刻蚀剖面且对Si衬底几乎没有损失。     

感应耦合等离子体技术用于熔融石英表面凹凸光栅的刻蚀

感应耦合等离子体(ICP)刻蚀技术是一种新的干法刻蚀技术,具有刻蚀速率高和各向异性刻蚀等优点,并且能够独立控制等离子体密度和自偏置电压。然而,在利用这种技术进行刻蚀的过程中,经常会发生聚合物的沉积,从而阻碍了刻蚀过程的继续。我们报道了在熔融石英表面刻蚀光栅时不产生聚合物沉积的技术,给出了优化参数。所制作的熔融石英普通光栅和600线／mm的高密度光栅的表面很干净,没有聚合物沉积。光栅衍射效率的实际测量值和预期的理论值吻合得很好。最后还研究了ICP技术的刻蚀速度,刻蚀均匀性和过程可重复性等参数。     

Plasma enhanced in situ chamber cleaning evaluated byextracted-plasma-parameter analysis

We have demonstrated that high-efficiency in situ chamber cleaning with short gas residence time is possible for SiO₂ etching chambers by use of NF₃ plasma, and that the endpoint determination of the cleaning is possible by monitoring the optical emission intensities of CO or H. Nitrogen trifluoride (NF₃), which has a low N-F bond energy, can generate a plasma with a high density of ions and radicals featuring low kinetic energy. The cleaning efficiency of several halogenated-gas plasmas has been evaluated based on extracted-plasma-parameter analysis. In this analysis important plasma parameters, such as ion energy and ion flux density, can be extracted through a simple rf waveform measurement at the plasma excitation electrode. The accuracy of this technique has been confirmed with a newly developed rf plasma direct probing method and by ion current measurements     

Temperature effects on tungsten etching

The influence of the substrate temperature (from T_s = +20°C to T_s = −45°C) on the etching characteristics (etch rate and anisotropy) of tungsten material has been investigated using a surface-wave sustained magnetoplasma reactor operated with SF₆. By correlating the F-atom concentration and the ion current density to the etching characteristics, we found that ion-assisted etching becomes more important than spontaneous chemical etching as the substrate temperature and SF₆ gas pressure decrease, ensuring, in absence of external biasing, high etching anisotropy together with high microscopic uniformity for submicrometer features (0.2 to 1 μm). Our results reveal the competitive influence between substrate temperature (which inhibits spontaneous chemical reaction as it is lowered) and gas pressure (which favours spontaneous chemical reaction as it is increased). Obtaining high anisotropy requires, in the present case, a substrate temperature of T_s = −20°C for P = 0.5 mTorr and a temperature as low as T_s = −35°C for P = 1.5 mTorr.     

Bulk oxide charge and slow states in Si–SiO2 structures generated by RIE-mode plasma

The damage induced in the thin SiO₂–Si system after an exposure to O₂ and N₂ plasma working in reactive ion etching (RIE) mode has been studied. A generation of high density (up to 5×10¹² cm⁻² in the first 15 s plasma exposure) of positive oxide charge in bulk traps as well as in slow states has been established. The RIE damage effects become highly process dependent as the plasma time increases, the fixed oxide charge first increases and then slows down or even turns around depending on discharge conditions. It is suggested that the relative contribution of the two main plasma components (ion bombardment and vacuum UV photons) at different discharge regimes is the reason for the appearance or the absence of the “turn-around” effect. It is established that the combination O₂ plasma and low pressure is critical for the degradation of the plasma treated samples. The results reveal a strong linear correlation between the leakage current detected and plasma created positive charge.     

Minimizing damage and contamination in RIE processes byextracted-plasma-parameter analysis

It is reported that important plasma parameters for reactive ion etching (RIE) processes, such as ion energy and ion flux density, can be extracted from a simple RF waveform analysis at the excitation electrode in a conventional cathode-coupled, parallel-plate plasma RIE system. This analysis does not introduce any contamination or disturbances to the process. By using the extracted plasma parameters, surface damage and contamination in Si substrates induced by reactive ion etching in a SiCl₄ plasma were investigated. Optimum RIE conditions were then confirmed by studying the relationship between these parameters and the etching performance. It is shown using the experimental data that low-energy high-flux etching is the direction for high performance RIE in future ULSI fabrication     

Comparison of plasma etch techniques for III–V nitrides

Fabrication of group-III nitride devices relies on the ability to pattern features to depths ranging from 1000 Å to >5 μm with anisotropic profiles, smooth morphologies, selective etching of one material over another and a low degree of plasma-induced damage. In this study, GaN etch rates and etch profiles are compared using reactive ion etch (RIE), reactive ion beam etching (RIBE), electron cyclotron resonance (ECR) and inductively coupled plasma (ICP) etch systems. RIE yielded the slowest etch rates and sloped etch profiles despite dc-biases >−900 V. ECR and ICP etching yielded the highest rates with anisotropic profiles due to their high plasma flux and the ability to control ion energies independently of plasma density. RIBE etch results also showed anisotropic profiles but with slower etch rates than either ECR or ICP possibly due to lower ion flux. InN and AlN etch characteristics are also compared using ICP and RIBE.     

激光诱导化学反应刻蚀石英玻璃的实验研究

针对目前常用的超短脉冲激光加工、激光诱导等离子加工、纳秒紫外激光加工石英玻璃刻蚀率低下的问题,提出一种能够大范围、高刻蚀率、低裂损刻蚀石英玻璃的新方法,即利用1064nm红外激光诱导Ba(OH)2化学反应刻蚀。本文主要从不同能量密度激光诱导化学反应刻蚀机理进行分析,实验表明,当激光能量密度超过16 J/cm2时,石英玻璃被刻蚀;当激光能量密度在16~24 J/cm2之间时,仅物理作用去蚀石英玻璃,故刻蚀率随激光能量变化较小;当激光能量密度在24~42 J/cm2之间时,刻蚀率随激光能量密度变化较大,该阶段Ba(OH)2以及其分解生成的BaO在高温条件下都与石英玻璃主要成分SiO2发生化学反应并生成BaSiO3,故刻蚀率较高;激光能量密度在42~46 J/cm2时,化学反应速率趋于饱和,故该阶段刻蚀率随激光能量密度变化较小。     

高密度RF等离子体刻蚀工艺直流自我偏压的研究

直流自我偏压作为高密度射频(RF)等离子体刻蚀工艺中的重要电学参数,反映出具有高能量的离子对待刻蚀晶片的轰击效果,后者决定了刻蚀工艺的各向异性、刻蚀速率、选择比及形貌特征等工艺结果。该文以HBr作为刻蚀气体,采用电感耦合等离子体(ICP)金属刻蚀系统针对刻蚀工艺中的直流自我偏压进行研究。研究中分别改变离子源功率、衬底偏压功率、刻蚀压力及HBr气体流量,观察直流自我偏压及其峰值的相应变化规律。实验结果表明,随着离子源功率的升高,直流自我偏压将会轻度降低;升高偏压功率则会显著提升直流自我偏压。刻蚀压力与直流自我偏压呈正比例关系,HBr气体流量的变化及待刻蚀晶片的材质对直流自我偏压无显著影响。     

掺镁铌酸锂晶体的ICP刻蚀性能

掺镁铌酸锂晶体(Mg:LiNbO3)是一种相对难刻蚀的晶体,Mg:LiNbO3的干法刻蚀速率和刻蚀形貌控制是铌酸锂光电子器件加工中的关键技术之一。采用牛津仪器公司的Plasmalab System 100以SF6/Ar为刻蚀气体,具体研究Mg:LiNbO3的刻蚀速率随着感应耦合等离子体(ICP)功率、反应离子刻蚀(RIE)功率、气室压强和气体流量配比等刻蚀参数的变化,同时研究发现SF6/(Ar+SF6)气体流量配比还会影响刻蚀表面的粗糙度。实验结果表明:在ICP功率为1000W,RIE功率为150W,标准状态(0℃,1个标准大气压)下气体总流量为52mL/min,压强为0.532Pa,SF6/(Ar+SF6)气体体积分数为0.077的条件下,刻蚀速率可达到152nm/min,刻蚀表面粗糙度为1.37nm,可获得刻蚀深度为2.5μm,侧壁角度为74.8°的表面平整脊形Mg:LiNbO3结构。     

Gallium arsenide surface chemistry and surface damage in a chlorine high density plasma etch process

In an effort to monitor ion-driven surface chemistry in the high density plasma etching of GaAs by Cl₂/Ar plasma chemistries, we have applied mass spectrometry and careful substrate temperature control. Etch product chlorides were mass analyzed while the substrate temperature was monitored by optical bandgap thermometry and as pressure (neutral flux), microwave power (ion flux) and rf bias of the substrate (ion energy) were varied. By ensuring that the substrate temperature does not deviate during process variations, the changes in product mass peak intensities are a direct measure of changes in the ionassisted surface chemistry which promotes anisotropic etching. Experimental results show that ion-assisted surface chemistry is optimum when sufficient Cl and Cl⁺ are present in the incident plasma flux. These conditions are met at low coupled microwave powers (<300 W) and low total process pressures (<1.0 mTorr) for input gas mixtures of 25% Cl₂ in Ar. Three mechanistic regions are identified for surface chemistry as a function of incident ion energy: 1) largely thermal chemistry for <50 eV; 2) ion-assisted chemistry for 50–200 eV; and 3) sputtering for >200 eV. Photoreflectance measurements of the surface Fermi level show significant damage for ion energies >75 eV. However, in situ and ex situ surface passivations can recover the surface Fermi level for up to 200 eV ion energies, in good correlation to the onset of sputtering and subsurface damage. Thus, anisotropic, low damage pattern transfer is possible for ion energies between 50 and 200 eV.