Dry etching process

In order to design and optimize anisotropic dry etching processes, severai issues must be understood ... 

In 2004, Olayo-Valles et al. described a related dry-etch processing of self-assembled block copolymer films to generate porous materials for use as magnetic material templates [50]. These authors employed thin films of... 

A number of fabrication techniques meet the general requirements for constructing an efficient and compact microreactor. Popular methods include LIGA, wet and dry etching processes, micromachining, lamination, and soft lithography. 

From an IC manufacturing standpoint, two additional considerations fuel the drive toward dry etch processes. Relatively large volumes of dangerous acids and solvents must be handled and ultimately recycled or disposed of with wet etching or resist stripping techniques. Dry etching or resist stripping operations use comparatively small amounts of chemicals. 

The past five years have witnessed significant progress in the understanding and control of plasma etch processes. Nevertheless, much of the fundamental chemistry and physics occurring in these reactive atmospheres remains ill-understood, or indeed unknown. The following sections assimilate the information currently available on dry etch processes, and present a framework within which plasma etching can be viewed. 

Figure 13a shows the resist in a three-layer Al-RIE-PCM system by Havas et al. The dry etching conditions were similar to those of plasma etching. Therefore, an undercut was produced under the Al PCM to facilitate lift-off. Figure 13b shows the resist image in a three-layer siloxane RIE PCM system. The dry etching process was sufficiently anisotropic to eliminate the undercut. 

The polymer resist exhibiting the lowest PE rate or highest etch resistance versus PMMA or oxide is poly(styrene) (see Table IV). This system, like the others of Table IV, is representative of a vinyl pol3mier with general structural formula of -(CH2-CXY)-. Poly(chlorostyrene), a chlorinated derivative of the aromatic poly(styrene), exhibits equal resistance towards all three dry etch processes. Here halogenatlon has not enhanced the etch rate or reduced the resistance as seen before for PTECM, PTFEM, and PMCA nonaromatic systems. Therefore, the aromatic side group must... 

In CF4 plasma etching at 0.5 to 1 Torr pressure, the active species are neutral free radicals like F atoms and CF3 (28). Novolak resins have fairly strong CF4 plasma etch resistance (29), which, because of widespread use of the dry etching process, is one of the required features for resins used as resist materials for IC manufacturing processes. 

Figure 1. Cross sections of films etched with liquid or plasma etchants. The isotropic profile is the result of zero overetch and can be generated with liquid or plasma etch techniques. The anisotropic (vertical) profile requires plasma or dry-etch processes. W is the width of the resist pattern. (Reproduced from reference 2. Copyright 1983 American Chemical Society.)...

The vias are extended down through layers 48, 52 and 53 by using a plasma dry etching process. A wet etching process is then used to smooth the surfaces of the vias. An electrically conductive layer of indium is formed over the photoresist masking layer and within the vias in electrical contact with the region 64 and the input pad 58. The photoresist masking layer and... 

With the increase of the degree of integration of microcircuits, the multilevel interconnect technology becomes inevitable for future VLSI manufacture. Polyimide exhibits superior planarity over stepped structures and is expected to be one of the most promising materials for the dielectric insulation of VLSI s. However, since the smallest via holes so far achieved by wet etching is 3 pm (1), the formation of fine via holes by a dry etch process is needed for the application of polyimide to VLSI having fine metal wiring. 

The use of iodate and periodic acid as oxidizers for noble metal CMP has also been attempted. Similar to W CMP, a surface oxidation or modification is required for the subsequent removal by mechanical force. For example, the potential use of ruthenium as bottom electrode capacitor for next-generation DRAM devices [40] has been explored. Owing to the fact that a dry-etch process can lead to the formation of toxic RUO4 [41], the possibility of using CMP to implement Ru has gained interest recently. The studies in this area have indicated that the formation of stable passive layers such as RUO2 [41,42] and RU2O5 [42] are important steps in the Ru CMP. 

The mass spectroscopic analysis of the gases formed in thermal development of the UV exposed poly(l-butene sulfone)/pyridine N-oxide revealed only 1-butene and S02 as the products, which indicated depolymerization of the polymer initiated by energy transfer form the sensitizer. These photosensitized poly(olefin sulfones) are not suitable for dry etching processes, and they are not reactive ion etching resistant. Resists made of poly(olefin sulfones) and novolac resins which will be described next are CF plasma etch resistant with reasonable photosensitivities. 

Etching durability high against etching of thin Cr film high against various dry-etching processes... 

Many negative electron resists recently developed for dry-etching processes are based on the polystyrene (PSt) structure because of the relatively high stability against dry-etching reactions and high Tg of PSt. Another advantage of PSt is the availability of nearly mono-dispersed polymer. 

Optimum design was made theoretically on P(CMS-2VN) system. Design method was developed based on theoretical analysis for copolymer resist sensitivity and on dry etch rate dependence on polymer structure obtained by a series of experiments. P(CMSq -2VN9i) (Mw =7.8 x 10, Mw /Mp = 1.3) proved to have high sensitivity (Dg=0.9 jtC / cm2) and high resolution (<0.5 /nm) as well as high dry etch resistance. This resist is suitable for microfabrication especially for dry etching processes. 

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