Plasma etching resist

Incorporation of cyclic aliphatic (aUcycHc) side groups markedly improves the plasma etch resistance of acryhc polymers, without reduciag optical transparency at 193 nm (91). Figure 32 presents stmctures of some acryhc polymers currendy under study for use ia 193-nm CA resists (92—94). Recendy, polymers with main-chain aUcycHc stmctures have been described that offer similar properties (95,96). 

Scanning electron microscopy confirmed sub-0.5p.m resolution capabilities in TBSS -acid generator resist films (Figure 3). Note that the edge profiles are nearly vertical. Preliminary results indicate that the plasma etching resistance is satisfactory for semiconductor device processing. 

When MCA is copolymerized with MMA, the resulting copolymer etches faster than PMMA, consistent with the PMCA and MCN/MCA results. Incorporation of MCA, a monomer with a-chlorine, has the effect of decreasing plasma etch resistance, as is observed for the MCA homopolymer. Sensitization by chlorine appears to be general (see Tables I, III, and VI), except for the case where the chlorine is Incorporated onto the aromatic side chain group. This effect was observed previously by Taylor and Wolf for other polymer systems. ( ) The C-Cl bond strength is lower than that for C-H and C-F, and there is much evidence that this bond can be easily cleaved, even in the solid state. (, ) This weaker side chain group leads to lower dry-etch resistance. 

The inorganic resist system is unique with respect to optical sensitivity coupled with 02 plasma resistance. Most organic polymers do not possess sufficient plasma etching resistance to withstand oxygen plasma etching of... 

Although the Novolak resin of the w-cresol-benzaldehyde failed to show a marked increase in CF4 plasma etching resistance, the Novolak resins of hydroxy-naphthalene-hydroxybenzaldehyde showed a remarkable increase in the plasma etching resistance. The resist films also yielded excellent patterns when used together with a diazo-naphthoquinone sensitizer almost non-diluted AZ2401 developer had to be used for image development due to the hydrophobic nature of the naphthalene group. 

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. 

Electron Beam Microliihography Good sensitivity and contrast, acceptable plasma etching resistance less scattering of electrons aiul therefore better resolution negative and positive resists possible. 

Novel terpolymer compositions containing 4-(di-trifluoromethyl-hydroxymethyl)-1-(di-trifluoromethy)methyl)cyclohexyl] vinylsulfonate have been prepared having excellent transparency, substrate adhesion, and plasma etching resistance. The introduction of perfluoronorbornene resulted polymers that were especially suitable for deep UV lithography. 

Several years ago, Taylor et al. (2,3) showed that the oxygen plasma-etch resistance of carbon-based polymers could be markedly enhanced by incorporating certain atoms into the polymer chain. Particularly effective were those elements such as silicon or titanium that form a refractory oxide during oxygen RIE. The oxide is formed at the surface of the resist and greatly retards the subsequent etching rate of the remaining resist. 

It has been found, however, that the etch rate of PBS can be reasonably controlled in both oxygen and CF4/O2 plasmas if the substrate temperature is kept below room temperature (9). This fact has been utilized to reduce the defect density in the manufacture of chrome photomasks by exposing the developed PBS pattern to a low-temperature oxygen plasma (descum) prior to wet-etching the chrome. We have now found that the plasma-etch resistance of PBS in a CF4/O2 plasma can be markedly enhanced at room temperature simply by exposing the resist to a short oxygen plasma pretreatment prior to exposure to the fluorinated plasma. This effect can be used in a variety of pattern transfer processes to controllably generate submicron features on wafers and masks. This paper examines the parameters associated with this effect, proposes a mechanism to account for the results and delineates some possible pattern transfer processes. 

Last two decades were period of a transition from a liquid toward dry etching. That is why plasma resistance is among the most important properties of a photoresist. In the case of fluorine-containing plasmas, etch resistance... 

The chemical amplification idea appeared when it was necessary to develop photoresist material having high sensitivity, high resolution, and good plasma etch resistance. It was desirable primarily when the 248 nm exposure became the requirement of the industry. And the result of implementation of the idea was very good. Chemical amplification as a basic ideology of the photoresist creation partly worked at the 193 nm millstone. ... 

Polymers formed from the ROP of [l]ferrocenophanes have been investigated for a variety of uses. Vancso et al. has tested them for nanolithographic and plasma etch-resistant materials.165,166 Pannel and co-workers have reported ferrocenylsilylene polymers for use as tapered optical-fiber sensors in the detection of ammonia and carbon dioxide.167... 

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. 

This paper addresses photoresist lithographic performance only. For a more complete view of these systems, the accompanying paper should be read where thermal flow characteristics as well as plasma etch resistance data are presented and compared for many of the photoresists evaluated in this work. 

Plasma etch resistance Very good Not very good... 

A major drawback of this sulfone terpolymer resist is its poor plasma etch resistance. 

The effect of the cross-linking of resist polymer films is to make the film stable to heat such that it cannot be made to flow or melt. A fully cross-linked resist polymer film is practically insoluble in most solvents, although it can be stripped with oxygen plasma etching. Its plasma etch resistance is superior to a similar film that is not cross-linked. 

Plasma development derives its advantage over its liquid counterpart mainly from the anisotropic nature of the process, except when loss from the unexposed area is vanishingly small, in which case the isotropy comes from that already in the latent image. The resist must be tough to avoid being eroded completely while the substrate underneath is etched. To improve the plasma etch resistance, aromatic compounds have been added to PMMA (50, 51). Hence, for... 

The sensitivity of this terpolymer is 170 times that of PMMA and is capable of sub-micron resolntion. Poly(aromatic snlfones) may also be nsed as positive resists [19]. Their quantum efficiency is low, however. Aromatic moieties ensnre a useful plasma etch resistance. 

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