Development, positive photoresist

Finally, factories must collect and segregate spent solvent waste as a separate waste stream and thus incur additional cost. These cost of ownership issues are substantially decreased through the use of aqueous, metal-ion free developers based on tetramethylammonium hydroxide which are the semiconductor industry standard for developing positive photoresists. 

Miscellaneous Applications. PEIs and their derivatives ate used as cementation auxihaties in cmde oil exploration (459), and for breaking cmde oil emulsions (460) in cmde oil extraction. Seed coatings of water-soluble copolymers containing polyethyleneimine have been developed (461). Polyethyleneimine derivatives have positive photoresist properties (462) amidated polyethyleneimines improve the flow properties of cement (463) and with few exceptions, A/-acyla2iddines act as chemical sterilisers for insects (464). 

Fig. 6. Schematic illustration of the photohthographic patterning process used for defining features in siUcon dioxide using ( ) a positive photoresist that polymerizes light, where ( ) represents the mask (U) Si02 and ( ) Si. Development includes removal of the mask and undeveloped photoresist.

We have developed a novel silicone-based positive photoresist (SPP) for two-layer resist systems. SPP is composed of an acetylated poly(phenylsilsesquioxane)... 

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). 

Alkali-developable silicon-containing positive photoresists, development, 175 Alkoxysilanes, polymerization,... 

Interest in solution inhibition resist systems is not limited to photoresist technology. Systems that are sensitive to electron-beam irradiation have also been of active interest. While conventional positive photoresists may be used for e-beam applications (31,32), they exhibit poor sensitivity and alternatives are desirable. Bowden, et al, at AT T Bell Laboratories, developed a novel, novolac-poly(2-methyl-l-pentene sulfone) (PMPS) composite resist, NPR (Figure 9) (33,34). PMPS, which acts as a dissolution inhibitor for the novolac resin, undergoes spontaneous depolymerization upon irradiation (35). Subsequent vaporization facilitates aqueous base removal of the exposed regions. Resist systems based on this chemistry have also been reported by other workers (36,37). 

Figure 24. Electron micrographs of 1.2 pm lines in a positive photoresist exposed on a reflective substrate and developed in standard photoresist developer. (Reproduced with permission from Ref. 32)...

The latest addition to this list of dry developing resist materials is a contribution from IBM s San Jose Research Laboratory (66-67) that evolved from efforts to design positive-tone resist materials that incorporate chemical amplification. These efforts were stimulated by the fact that the quantum yield of typical diazoquinones of the sort used in the formulation of positive photoresists is 0.2 to 0.3 thus, three or four photons are required to transform a single molecule of sensitizer. This places a fundamental limit on the photo-sensitivity of such systems. 

Two component, positive photoresists (see Section 3.5.b) represent systems with unusual exposure characteristics caused by the standing wave effect (see Section 2.1.f) and "bleaching" or change in optical density during exposure (see Sections 3.5 and 3.9). Both of these phenomena result in nonlinear exposure throughout the thickness of the resist film, and result in uneven developing rates as a function of film thickness, making evaluation of these systems difficult. 

At the present time, most of the positive photoresists used in the manufacture of microcircuits consist of a low molecular weight phenolic resin and a photoactive dissolution inhibitor. This composite system is not readily soluble in aqueous base but becomes so upon irradiation with ultraviolet light. When this resist is exposed, the dissolution inhibitor, a diazoketone, undergoes a Wolff rearrangement followed by reaction with ambient water to produce a substituted indene carboxylic acid. This photoinduced transformation of the photoactive compound from a hydrophobic molecule to a hydrophillic carboxylic acid allows the resin to be rapidly dissolved by the developer. (L2,3)... 

A positive photoresist is one that becomes more soluble in the developing fluid as a result of exposure to light, and so dissolves away leaving the desired pattern in the form of undissolved resist a negative resist becomes less soluble on irradiation, so that it is then the illuminated areas that remain. 

An alternative strategy is to deposit a positive photoresist to mask areas where electrode material is to be absent. Upon exposure through the mask and development, the base substrate will be exposed where the electrode components are to be deposited. The electrode materials are then typically deposited over both the bare substrate and the photoresist. A liftoff procedure is then used to remove both the photoresist and excess deposited electrode film material by swelling the photoresist polymer in a suitable solvent, leaving the electrode array behind [40,45,47] with the underlying substrate also exposed in regions where no electrode is present. Increasingly complex patterns of application of multiple... 

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