Photoresist, types

TABLE 26.1 Summary for Dry-Film Photoresist Types and Chemistries... 

Photoresist type Develop solution Strip solution Application... 

In terms of volume used, the most popular photoresist type has been a physical combination of a phenol-formaldehyde novolak resin with a diazoqninone. The novolak (molecular weight of about 500-2000) does not dissolve in dilnte alkali when 20%-50% of a diazoketone is present in the dry film. However, UV light converts the alkali-insoluble diazoquinone into the hydrophilic carboxylate form via the Wolff rearrangement (Figure 13.9). Without the diazoquinone dissolution inhibitor in the exposed areas, the novolak now dissolves in dilute alkali. 

A unique but widely studied polymeric LB system are the polyglutamates or hairy rod polymers. These polymers have a hydrophilic rod of helical polyglutamate with hydrophobic alkyl side chains. Their rigidity and amphiphilic-ity imparts order (lyotropic and thermotropic) in LB films and they take on a F-type stmcture such as that illustrated in Fig. XV-16 [182]. These LB films are useful for waveguides, photoresists, and chemical sensors. LB films of these polymers are very thermally stable, as was indicated by the lack of interdiffusion up to 414 K shown by neutron reflectivity of alternating hydrogenated and deuterated layers [183]. AFM measurements have shown that these films take on different stmctures if directly deposited onto silicon or onto LB films of cadmium arachidate [184]. 

Pos twe-Tone Photoresists. The ester, carbonate, and ketal acidolysis reactions which form the basis of most positive tone CA resists are thought to proceed under specific acid catalysis (62). In this mechanism, illustrated in Figure 22 for the hydrolysis of tert-huty acetate (type A l) (63), the first step involves a rapid equihbrium where the proton is transferred between the photogenerated acid and the acid-labile protecting group ... 

Similar types of cross-linking reactions are observed for polymers to which photosensitive molecules ate chemically attached to the backbone of the polymer stmcture (Fig. 7). Radiation curing of polymers using uv and visible light energies is used widely in photoimaging and photoresist technology (Table 8) (58,59). 

Note that there are two types of photoresists- positive and negative. One is pol3nmerized (made insoluble in water) by exposure to light while the... 

New positive-type photoresist systems based on enzymatically synthesized phenolic polymers were developed. The polymers from the bisphenol monomers... 

IMS can be used for chemical analysis of vapours from electronics packaging [287]. IMS-QMS has been used to analyse headspace vapours in sealed electronic packages [275,288] and to follow outgassing of polymers [287]. Various types of photoresist solvents, phtha-late plasticisers and other polymer additives, such as BHT, were detected. Other applications of IMS in semiconductor technology involve failure analysis control of the efficiency of cleaning and etching steps characterisation of process media and surveillance of the atmosphere of clean rooms. 

Figure 6. O -RIE etching of poly(cyclohexylmethylsilane) (PCHMS) — A —, and a hardbaked AZ-type photoresist ( — — ) etch conditions 10 mTorr, 40 SCCM, -232V, 110W,...

Figure 8. Bilayer imaging of PCHMS using a PE-500 Microalign 1 1 projection printer (UV-2 mode). 0.16 pm PCHMS over 1.0 pm of a hardbaked AZ-type photoresist. 02-RIE image transfer, 0.75-pm images.

The object of this study is to develop new photoresists for deep-UV lithography, by using the reversible photoreaction of pyrimidine bases (17-19). Applicability of pyrimidine containing polymers to both negative and positive type photoresists is due to this photoreversible reaction in which cyclobutane dimers are either formed or cleaved depending on the exposure wavelength (Scheme 2). 

Experimental methods for determining 0 are well documented (2). These experiments are conveniently carried out and require only a method of producing reasonably narrow-bandwidth radiation, a method of measuring the flux of that radiation per unit area, and a UV-visible spectrophotometer. The quantum efficiency of typical diazonaphthoquinone sensitizers of the type that are used in the formulation of positive photoresists ranges from 0.2 to 0.3, whereas the quantum efficiency of the bis-arylazide sensitizers used in the formulation of two-component negative photoresists, ranges from 0.5 to 1.0. 

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