Peroxypolytungstic acids: A new inorganic resist material

Recently reported amorphous polytungstic acids containing peroxo groups are found to provide a new inorganic resist. A homogeneous resist film can be formed easily with the spin coating method. This film is made insoluble in water by deep ultraviolet, x ray, and electron beam irradiation. The oxygen reactive ion etching (O2 RIE) durability is found to be high enough that a bilayer resist scheme employing this resist as a top imaging layer gives a high resolution pattern (line and space: 0.38 μm). The mechanism for the radiation induced reaction is also discussed.