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Etching
Published in Kumar Shubham, Ankaj Gupta, Integrated Circuit Fabrication, 2021
The advantages of wet etching processes are the simple equipment, high etching rate, and high selectivity. However, there are many disadvantages. Wet etching is generally isotropic, which results in the etchant chemicals removing substrate material under the masking material. Wet etching also requires large amounts of etchant chemicals because the substrate material has to be covered with the etchant chemical. Furthermore, the etchant chemicals have to be consistently replaced in order to keep the same initial etching rate. As a result, the chemical and disposal costs associated with wet etching are extremely high. Some advantages of dry etching are its capability of automation and reduced material consumption. Dry etching (e.g. plasma etching) costs less to dispose of the products compared to wet etching. An example of purely chemical dry etching is plasma etching. A disadvantage of purely chemical etching techniques, specifically plasma etching processes, is that they do not have high anisotropy because reacting species can react in any direction and can enter from beneath the masking material. Anisotropy is when the etching exclusively occurs in one direction. This property is useful when it is necessary to remove material only in the vertical direction since the material covered by the masking material would not be removed. In cases where high anisotropy is vital, dry etching techniques that use only physical removal or a combination of both physical removal and chemical reactions are used.
High-k Material Processing in CMOS VLSI Technology
Published in Niladri Pratap Maity, Reshmi Maity, Srimanta Baishya, High-K Gate Dielectric Materials, 2020
It is a process to remove material either selectively or nonselectively. Different methods are available for etching (Madou, 1997; William et al., 2003; Pandhumsoporn et al., 1996; Vasile et al., 1994). The most commonly used etching is dry etching and wet etching/chemical etching. Wet etching is mainly used for cleaning, shaping, and polishing whereas dry etching is used for micro machining/precision machining. The advantages of dry etching are higher aspect ratio, high directionality, less corrosion problems for metal features in the structure and less undercutting and broadening of photoresist features. The problem of dry etching is low etched rate and high sensitive to operating parameters in comparison to wet etching. So it consumes much time and is difficult to balance. Etching may be isotropic or anisotropic depending on the mechanism of etching. In case of isotropic etching, the etching rate in crystallographic directions is same whereas in anisotropy case, the etching rate is different for different crystallographic directions (Sahu, 2013).
VLSI Scaling and Fabrication
Published in Manoj Kumar Majumder, Vijay Rao Kumbhare, Aditya Japa, Brajesh Kumar Kaushik, Introduction to Microelectronics to Nanoelectronics, 2020
Manoj Kumar Majumder, Vijay Rao Kumbhare, Aditya Japa, Brajesh Kumar Kaushik
Advantages and disadvantagesThe equipment used for dry etching is a simple and good selectivity for most of the materials.It exhibits a higher etching rate and selectivity as compared to dry etching.Mostly, it is isotropic, which requires a large amount of etchant chemical to maintain the same initial etching rate and to remove unwanted material from a silicon wafer.The cost required to perform wet etching is extremely higher as compared to dry etching.
Integrated fabrication process with multiple optimized factors for high power density of IPMC actuator
Published in International Journal of Smart and Nano Materials, 2022
Zicai Zhu, Changsheng Bian, Wanfa Bai, Qiao Hu, Suijun Chen
To study the effect of the membrane surface area on the performance improvement of the IPMC quantitatively, IPMCs were fabricated with mesoscopic hole arrays on their surfaces via hot pressing with micro-column structured molds. The key step in this case is the fabrication of the micro-column structure mold used for hot pressing. First, a microscale cylindrical hole array was produced on the wafer surface by dry etching, as shown in Figure 4(a). Then, a polydimethylsiloxane (PDMS; Sylgard 184, Dow Corning) solution was cast on the wafer surface. After curing, the PDMS film was peeled from the wafer. The film is shown in Figure 4(b) as a mold with micro-columns. As illustrated in Figure 4(c), the surface area of the Nafion membrane can be improved further by forming random microstructures on the 1 μm scale via sandblasting after hot pressing. This combination of hot pressing and sandblasting processes will cause the electrode-polymer interface area of the IPMC to be greatly increased after plating.
Application of Deep Belief Network for Critical Heat Flux Prediction on Microstructure Surfaces
Published in Nuclear Technology, 2020
A uniform microstructured surface can be fabricated via several micromanufacturing methods such as electrical discharge machining,4 reactive ion etching,5 laser etching,6 chemical vapor etching,6 and dry etching.7 Various microstructure designs, including cylindrical pillars in a square lattice, square pillars,8 pillars in a triangular lattice,9 staggered pillars,8 and piranha pillars,10 have been tested to measure CHF. For pool boiling CHF experiments, both water11 and FC-72 (Refs. 7 and 8) were primarily used to study the effects of microstructures on CHF. In most pool boiling experiments, the cuboidal substrates were primarily used while the disk-shape surfaces were tested in a limited number of experiments.12
A novel fabrication of TDMOSFETs using two-step trench etching and twice self-alignment technique
Published in International Journal of Electronics Letters, 2019
Jongdae Kim, Jimin Oh, Sang-Gi Kim, Yilsuk Yang
Following the first photolithography of the trench mask, a trench area was defined by dry etching the silicon nitride film and oxide film in sequence. The tetraethyl orthosilicate (TEOS) oxide was deposited and removed by using reactive ion etching (RIE) to obtain oxide spacers for pull-back regions. The first shallow trench was formed by the shallow etching of the p-well region. Using the first self-alignment technique with oxide space, arsenic (As) ion implantation and pre-drive in were performed to make n+ source region under the pull-back region, as shown in Figure 1(a). The second step deep trench etching through the p-well region was carried out to make a final trench structure with the depth of 1.8 μm. After the corner was fully exposed, the wafer was annealed briefly in a 950ºC chamber of hydrogen ambient to obtain a corner rounding, as seen in Figure 1(b).