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首页> 外文学位 >Characterization of surface reaction during sulfur hexafluoride etching of silicon in an electron cyclotron resonance (ECR) plasma reactor.
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Characterization of surface reaction during sulfur hexafluoride etching of silicon in an electron cyclotron resonance (ECR) plasma reactor.

机译：在电子回旋共振（ECR）等离子体反应器中对硅进行六氟化硫蚀刻时的表面反应特性。

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摘要

This investigation compares a surface chemistry model with an experimental SF{dollar}sb6{dollar} etching chemistry of polysilicon and silicon dioxide in ECR plasmas under low-energy ion bombardment. The surface chemistry model with the assumptions of sequential fluorination of silicon surface is based on a set of reaction parameters which include fluorine concentration, wafer ion flux, wafer ion energy, and wafer temperature. Ion-assisted etching mainly enhances the desorption of SiF{dollar}sb2{dollar} on the silicon surfaces. Sidewall etching comes from the spontaneous etching of silicon with fluorine atoms and its rate is determined by the balance of photoresist deposition and the stripping of the deposition. Patterned 4-inch silicon wafers with a 5000 A polysilicon film over a 1000 A SiO{dollar}sb2{dollar} are used to study the correlations between etch characteristics and reaction parameters, which were determined from optical emission actinometry and Langmuir probe measurements. The inherent capability of the ECR reactor is exploited to control the reaction parameters. Data were obtained by independently varying the microwave power and the wafer chuck position, while holding pressure and flow rates constant. Under these conditions, the fluorine concentration and ion energy were approximately constant at the wafer, while the ion current varied over a range of 0.5 mA/cm{dollar}sp2{dollar} to 20 mA/cm{dollar}sp2{dollar}. The etch rates were strongly correlated with the wafer ion current. In particular, the vertical polysilicon etch rate increased with ion current from 0.5 to 1.5 {dollar}mu{dollar}m/min, while the lateral etch rate decreased from 0.4 to 0.1 {dollar}mu{dollar}m/min for gas compositions of 95%SF{dollar}sb6{dollar}/Ar, pressure of 1 mTorr and photoresist patterns. These trends are also valid for different fluorine concentrations tried. Oxide etch rate appears strongly ion-assisted and varied almost linearly with ion current and fluorine concentration. These data fit well with current surface chemistry models and indicate that reaction parameters are the fundamental variables to the etch process. The models predict that anisotropic etching with high selectivity to oxide ({dollar}sim{dollar}10) can be achieved in SF{dollar}sb6{dollar}/Ar ECR plasmas at low fluorine concentration ({dollar}sim{dollar}10{dollar}sp{lcub}12{rcub}{dollar} atoms/cm{dollar}sp3{dollar}) and medium ion flux (6 mA/cm{dollar}sp2{dollar}) but sacrificing the etch rate ({dollar}sim{dollar}0.2 {dollar}mu{dollar}m/min). Suggestions for further study are presented.
机译：这项研究将表面化学模型与在低能离子轰击下的ECR等离子体中的多晶硅和二氧化硅的实验SF {dollar} sb6 {dollar}蚀刻化学进行了比较。假设硅表面依次氟化的表面化学模型基于一组反应参数，包括氟浓度，晶片离子通量，晶片离子能量和晶片温度。离子辅助蚀刻主要增强了SiF {dolb} sb2 {dollar}在硅表面的解吸。侧壁蚀刻来自具有氟原子的硅的自发蚀刻，其速率取决于光刻胶沉积与沉积剥离之间的平衡。图案化的4英寸硅晶片在1000 A SiO {dollar} sb2 {dollar}上具有5000 A多晶硅膜，用于研究蚀刻特性与反应参数之间的相关性，这些相关性是通过光发射光化法和Langmuir探针测量确定的。利用ECR反应器的固有能力来控制反应参数。在保持压力和流量恒定的同时，通过独立改变微波功率和晶片卡盘位置获得数据。在这些条件下，晶片上的氟浓度和离子能量大致恒定，而离子电流在0.5mA / cm 2至20mA / cm 2的范围内变化。蚀刻速率与晶片离子电流密切相关。特别地，对于气体组合物，垂直多晶硅蚀刻速率随着离子电流从0.5增加到1.5 {μm} / min，而横向蚀刻速率从0.4降低到0.1μm/ min。 95％SF {dollar} sb6 {dollar} / Ar的压力，1 mTorr的压力和光刻胶图案。这些趋势对于尝试过的不同氟浓度也有效。氧化物蚀刻速率似乎在离子辅助下很强，并且几乎随离子电流和氟浓度线性变化。这些数据与当前的表面化学模型非常吻合，表明反应参数是蚀刻工艺的基本变量。这些模型预测，在氟浓度低的{{dollar} sim {dollar} 10}的SF {dollar} sb6 {dollar} / Ar ECR等离子体中，可以实现对氧化物具有高选择性的各向异性蚀刻（{dollar} sim {dollar} 10） {dollar} sp {lcub} 12 {rcub}原子/ cm {dollar} sp3 {dollar}）和中等离子通量（6 mA / cm {dollar} sp2 {dollar}），但牺牲了蚀刻速率（{dollar } sim {dollar} 0.2 {dollar} mu {dollar} m / min）。提出了进一步研究的建议。

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