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Generation, Removal, and Passivation of Plasma Process Induced Defects
Published in Kazumi Wada, Stella W. Pang, Defects in Optoelectronic Materials, 2021
In plasma etching, energetic particles in the discharge can cause damage in devices [1–10]. These high energy particles, which include ions, electrons, and photons, can introduce radiation damage in materials. Often, defects induced by dry etching penetrate deeply into the devices, way beyond the typical ion penetration range [11, 12]. In addition, contamination from materials coming off the plasma system or etch mask, deposition from the reactive species in the discharge, or stoichiometry changes due to preferential etching or layer intermixing in the compound semiconductors can also result in device degradation [13–16]. Therefore, it is important to understand the mechanisms for plasma process induced damage and to develop plasma etching conditions with minimal or no surface damage. However, there are multiple requirements that need to be satisfied for dry etching electronic or optoelectronic devices. These include controllable etch rate, selectivity, profile, surface morphology, uniformity, reproducibility, etch stop, and low damage. In order to meet most of these needs, some surface defects could be generated by dry etching. Therefore, sensitive techniques to analyze these surface defects are important to identify their origins and their influence to device performance. In addition, surface passivation and damage removal techniques are also critical to restore the device performance after plasma processing.
Lithography
Published in Andrew Sarangan, Nanofabrication, 2016
The width of a line is difficult to maintain in a wet chemical etch. This is due to the isotropic nature of wet chemical processes. Plasma etching is an alternative to wet chemical etching because it can produce anisotropic etch profiles (Figure 6.60). For small features, this is the most common approach taken. The ions in a plasma are directed toward the cathode at nearly normal incidence. If the substrate to be etched is placed on the cathode, the etching will become directional with very little lateral etching. The details of etching processes will be discussed in Chapter 7. Lift-off is more forgiving toward line width control than etch-down. Extremely narrow lines can be lifted-off, assuming the photolithography process is able to produce lines with suitable sidewall profiles.
Fabrication of BioMEMS Devices
Published in Simona Badilescu, Muthukumaran Packirisamy, BioMEMS, 2016
Simona Badilescu, Muthukumaran Packirisamy
Dry etching, which uses gases for etching, is suitable for making very small features in thin films, and it is used when a high resolution is necessary. There are many classes of dry etching techniques called high-pressure plasma etching, reactive ion etching (RIE), deep reactive ion etching (DRIE), and ion milling. In high-pressure plasma etching, the reactive species that are created react with the material to be etched, and as a result, the material is dissolved at the surface. In the RIE technique, the material to be etched is introduced in a reactor where a plasma is formed by using an RF power source (Figure 7.10). The high-energy ions may either hit the material and remove atoms from the surface or react at the surface of the material. Because there are many more collisions with the horizontal surfaces than with the walls, the etching rate will be higher.
Linear analysis and head-on collision of dust ion-acoustic shock waves in un-magnetized electronegative collisional plasmas
Published in Waves in Random and Complex Media, 2022
‘In contrast to the electropositive plasma, the electronegative plasma contains negative ions in addition to electrons and positive ions. In electronegative plasma, the inertia comes from positive ions and the necessary restoring force is given by the negative ions and electrons. These ions not only modify the plasma parameters but also affect the basic properties of natural modes in the electronegative plasmas. The negative ions are formed by the attachment of electrons to the neutral atoms or molecules’ [17]. Electronegative plasma has been of growing interest to the plasma research community due to its existence in space plasma and its application in industry and laboratory experiments [18–21]. The plasma consists of negative ions in pair with positive ions (such as and ) additionally electrons occur in D- and F-regions of the Earth’s ionosphere [22–24] and the inner coma of comet Halley [25]. A few number of plasma researchers [26–29] have reported the scope of industrial application of electronegative plasma such as the microelectronics, the plasma etching of metals/silicons, and plasma processing. In electronegative plasma, the number of electrons decreases according to charge neutrality condition: , where , and indicate the densities of electron, positive ion and negative ion, respectively.
Dynamics of dust-ion acoustic cnoidal and solitary pulses in a magnetized collisional complex plasma
Published in Waves in Random and Complex Media, 2021
Asmaa Mohamed Abdelghany, Mohammed Shihab, Mahmoud Saad Afify
Radio-frequency capacitively coupled plasma reactors (RF-CCPs) are characterized with a simple configuration to generate low temperature plasma for various plasma processing applications as plasma etching, deposition, and sputtering [1, 2]. High rates of the plasma processing is achieved via increasing the plasma density over the substrates. This could be done using an external magnetic field as in RF magnetron [3, 4]. The magnetic field traps the plasma electrons allowing an increase of the ionization rate, and, consequently, an increase of the plasma bulk over the substrates. Accelerated ions in the plasma sheath may hit the target and produce dust particles. Also, dust particles may be added artificially to the discharge. The confinement of dust particles in plasma sheaths has been found to excite low-frequency acoustics modes. The dust acoustic waves have been found to propagate along the direction of streaming ions and gravity and to be a function of the applied magnetic field [5]. It is really interesting and mandatory for plasma processing to investigate the excitation of dust acoustic waves in this complex plasma and to compare our theoretical results with available experimental results.
Holistic modeling and analysis of multistage manufacturing processes with sparse effective inputs and mixed profile outputs
Published in IISE Transactions, 2021
The statistical analysis of MMPs has been conducted for decades (Shi, 2006; Li and Shi, 2007; Jin and Shi, 2012). However, there are two major limitations of the existing analytical methods. First, they are unable to be applied to intermediate product quality measurements of mixed types of data in an MMP, which are increasingly common in data-rich manufacturing environments. Here, “mixed types of data” means that the data collected from different stages have different dimensions and distinct characteristics. As an example, a semiconductor manufacturing process consists of hundreds of stages, including deposition, lithography, plasma etching, ion-implantations, chemical-mechanical polishing, etc. (Nishi and Doering, 2000). In different stages, the corresponding outputs can be of image types (e.g., spatial data such as film thickness of each layer at multiple locations on the wafer (De Witte et al., 2003), multivariate random fields such as the alignment error at hundreds of positions on a wafer’s surface (Huang et al., 2008), and images of the etched trenches captured by a scanning electron microscope (Lee et al., 2006)), and/or assorted functional curves (e.g., the temperature, pressure, and radiofrequency curves during the reaction processes). As will be discussed in the next section, Stream of Variation (SOV) modeling approaches (Shi, 2006) based on a state-space model is generally not suitable for an MMP with mixed type of data. There is a lack of appropriate analytical methods for MMPs where output sensing data contains mixed types of data, such as images or functional curves.