The state of the art of photosensitive polyimides is reviewed with respect to the incorporation of photosensitivity into both polyimide precursors and soluble polyimides, for patterning in positive and negative modes. This paper emphasizes, in particular, the discussion of the performance of commercially available photosensitive polyimides with respect to their applications in electronics. The decisive properties, especially the patterning performance, and in the case of precursors the curing conditions, required to obtain full imidization, thermomechanical and electrical properties, solvent resistance and water uptake, as well as planarization of the commercially available materials, are compared with each other. An outlook presents the future demands on photosensitive polyimides.

Amorphous hydrogenated carbon (a–C:H) is introduced as a constituent of a two–layer resist system for lithography with a scanning tunneling microscope (STM) operating in air. The resist is made up of a thin electron sensitive and chemically amplified top resist (≤50 nm) and a–C:H as a thick conducting and etchable bottom resist. In this setup the bottom resist acts as the counter electrode allowing in principle operation on insulating substrates. We show that it is possible to generate structures with high aspect ratios by transfering the developed top resist patterns by means of oxygen reactive ion etching (RIE) into the bottom resist and halogen RIE into silicon substrates. Linewidths between 100 and 50 nm have been observed in the bottom resist as well as in the substrates.

Several silicon containing topresists for bilayer oxygen reactive ion etching systems were developed and examined. Each topresist consists of a silicon containing alkaline soluble copolymer and a 2‐diazo‐1‐naphthalenone‐4‐sulphonic acid ester photoactive compond (PAC). Half micron structures in the topresist were obtained with two different resist systems through deep‐UV (257 nm) or iline exposure. The etch rate ratios (planarizing layer:copolymer) vary between 7:1 and 13:1 under anisotropic etching conditions. Linewidth loss during oxygen RIE (reactive ion etching) pattern transfer is a problem for resists containing about 10% silicon, but equal lines and spaces after etching can be obtained through the use of thick topresists or linewidth bias in the topresist prior to etching.

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The patterning of organic layer materials is often hindered by the effects of the conditions used to “develop” the resist material, for example high temperatures for strong bases, which attack the substrate. The process described here allows the patterning even of delicate layers of oriented nonlinear optical polymers. The figure shown a patterned polyimide film 115 μm thick.