A novel technique for the production of iron oxide films from a polymer precursor is described. Films of poly(vinylferrocene) (PVFc) can be converted to iron oxide films in either a 2O0W oxygen plasma at room temperature or thermally in oxygen at 380~ The thermal decomposition appears to be more suitable for routine use, and process parameters for this technique have been optimized. The thermal conversion has been studied using infrared, visible, and u.v. spectroscopy and a decomposition reaction proposed. The iron oxide films prepared from PVFc have chemical and physical properties similar to the iron oxide films prepared using the iron pentacarbonyl process. Films prepared from PVFc are presently being evaluated for use as semitransparent photolithographic masks.The use of iron oxide for the fabrication of hard, semitransparent masks for use in the manufacture of integrated circuits is gaining rapid acceptance (1). Although the film material is primarily FeeOs, the exact structure is far more complicated than a pure Fe2Q system. Iron oxide was chosen from a large group of transition metal oxides and mixed oxides as having the best combination of chemical and physical properties required for use as a transparent mask material (2). The relevant properties are given by Peters et al. (3) as: (i) <1% transmission in the 360-400 nm spectral region; (it) >30% transmission at the sodium D line "(589 nm); (iii) an etching rate compatible with conventional photolithographic processes and materials; (iv) in addition, the physical integrity of the film (hardness, abrasion resistance, etc.) must be sufficient to sustain the abuses of routine handling. Three techniques ,are presently available for the deposition of thin films of iron oxide. The first is a chemical vapor deposition scheme using Fe(CO)~ developed by MacChesney et al. (4). Iron pentacarbonyl is thermally decomposed at temperatures in the 130 ~ 200~ range in an oxidizing atmosphere (CO2 + O2) on glass substrates. Films prepared by this technique have excellent mask properties, and this is presently the technique of choice for mask film manufacture. The. only substantial disadvantage of the procedure is using a poisonous compound, Fe(CO)2. A second deposition technique involving sputtering has been devised by Sinclair et al. (2, 3) for depositing Fe205films. The sputtering techniques used were conventional with the exception that it was found necessary to introduce CO2 + O2 as a discharge gas in order to increase the solubility of the deposited Fe205 films to an acceptable level for etching. The exact role that CO2 plays is not clear, but it appears likely th,at the pre sence of iron carbonate in films leads to increased solubility (3). The sputtering technique produces films which meet all mask requirements with the only disadvantage being that the process is slow and requires expensive vacuum equipment. The third general procedure, one similar to the process described in this paper, involves the decomposition of an organometallic compound in an oxidizing atmosp...