Collaborative Research: GOALI: Nonlinear Coupling in Pulsed Electronegative Plasmas: Multiple-sources, Multiple-frequencies, Multiple-time scales

从汽车到开门器，我们使用的几乎每一种科技产品都严重依赖于电脑、手机和无数的专业电路。不为人所知的是，这些电路主要包含在小型半导体芯片中，这些电路的组件的尺寸正在接近原子的大小，并且这些电路是在包含第四种物质状态--等离子体的机器中生产的。等离子体是可以产生化学反应环境的电离气体，由正离子、负离子、电子和中性原子和分子的混合物组成。低压等离子体将大量的自由基和离子输送到半导体晶片上，对制造微电子设备是必不可少的。然后，这些自由基和离子通过许多制造步骤对晶片表面进行刻蚀(去除材料)、沉积(添加材料)和钝化(改变表面成分)，以创建器件。还向保持晶片的衬底施加电压，以将离子加速到高能，以便激活这些晶片上的工艺。微电子制造中使用的一种重要的等离子体类型是电负性等离子体，其中负离子的密度比电子大得多。这些等离子体对工作条件(如功率、压力和气体混合物)非常敏感，经常不稳定。正在制造的器件的质量对这些不稳定性很敏感，因此对等离子体过程进行更严格的控制变得更加重要。脉冲等离子体(开关电源)和脉冲加速电压可产生尺寸更小的更高精度的元件，这转化为更强大的电子设备。虽然脉冲有很多优点，但脉冲也会产生不稳定性。为了优化用于制造微电子器件的等离子体工艺，必须了解、控制和预防电负性等离子体中的这些不稳定性。在本项目中，针对用于微电子制造的电感耦合等离子体(ICPs)类型，对脉冲电负性等离子体进行了实验和计算研究。其目标是量化产生等离子体的脉冲源和加速离子进入晶片的脉冲偏置之间的相互作用，不稳定性的发生，以及控制这些不稳定性的方法。这项研究是与我们的Goali合作伙伴LAM Research Corp.合作进行的，我们正在使用激光和电子探针诊断技术对电子密度、温度、等离子体电位、电流密度、磁场和离子能量分布进行三维、随时间变化的测量。第一性原理模型被用来研究脉冲瞬变、静电-电磁(E-H)转变以及脉冲源和偏置之间的相互作用过程中的基本等离子体传输。最终的结果将是极大地提高对用于材料处理的脉冲电负性等离子体类型的理解，这一理解被我们的GALI合作伙伴迅速转化为实践。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Society critically depends on computers, cell phones and a myriad of specialized electrical circuits in nearly every technological product we use, from cars to door openers. What is not widely known is that these electrical circuits are largely contained in small semiconductor chips, that the dimensions of components of those circuits are approaching the size of atoms, and that the circuits are produced in machines containing the fourth state of matter – plasma. Plasmas are ionized gases that can produce chemically reactive environments, and are composed of a mix of positive ions, negative ions, electrons and neutral atoms and molecules. Low pressure plasmas are essential to the fabrication of microelectronics devices by delivering fluxes of radicals and ions to a semiconductor wafer. These radicals and ions then etch (remove material), deposit (add material) and passivate (change surface composition) the wafer surface through many fabrication steps to create the devices. A voltage is also applied to the substrate holding the wafer to accelerate ions to high energies in order to activate these on-wafer processes. An important type of plasma used in microelectronics fabrication is an electronegative plasma in which the density of negative ions is much larger than electrons. These plasmas are very sensitive to operating conditions (such as power, pressure and gas mixture), with instabilities often. The quality of the devices being fabricated are sensitive to these instabilities and so tighter control of the plasma process is becoming more important. Pulsing the plasma (turning the power on-and-off) and pulsing the acceleration voltage results in higher precision components with smaller dimensions, whiich translates into more powerful electronics devices. Although pulsing provides many advantages, pulsing also produces instabilities. In order to optimize the plasma processes that are used to manufacture microelectronics devices, these instabilities in electronegative plasmas must be understood, controlled and, if possible, prevented.In this project, experimental and computational investigations of pulsed electronegative plasmas are being conducted for the type of inductively coupled plasmas (ICPs) that are used for microelectronics fabrication. The goal is to quantify the interactions between the pulsed sources that produce the plasma and the pulsed biases that accelerate ions into the wafer, the onset of instabilities, and methods to control those instabilities. This investigation is being conducted in collaboration with our GOALI partner Lam Research Corp. We are making 3-dimensional, time dependent measurements of electron density, temperature, plasma potential, current density, magnetic fields and ion energy distributions using laser and electrical probe diagnostics. First principles modeling is being used to investigate fundamental plasma transport during pulsed transients, electrostatic-to-electromagnetic (E-H) transitions and interactions of pulsed sources and biases. The end result will be a greatly improved understanding of pulsed electronegative plasmas of the type used for materials processing, with this understanding being rapidly translated to practice by our GOALI partner.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.