Chrome(Cr) is indisputably the most (and almost only) used material for photomask making since it took over from the emulsion material for many years ago. Wet etching is widely used and has shown to be very reliable and extendable to gradually smaller linewidths. Recently, wet etching will no longer be able to deliver the required pattern edge accuracy and uniformity over the reticle field. It is generally believed that wet etching of chrome will start to fail below 1um CD on mask level.
Dry etching of chrome will be required and has been investigated in detail already in a large number of laboratories. Although it is certainly not impossible, it has some disadvantages. The main reason for this is the difficulty of etching chrome in any other plasma than one that is chlorine based. Even so, most typical long etching times and hence the obtained selectivities to resist are rather low. To solve these problems, we investigated a new photomask blank materials using Mo-Cr alloy film deposited on quartz substrates instead of Cr absorber.
Mo-Cr films have several advantages including improved optical and electrical properties, chemical durability, and improved dry etch rate in comparison with that of Cr films. In this paper, we describes the results characterizing the new photomask blank materials, namely the Mo-Cr alloy films.
Mo film can not suitable materials for phohomask absorber that is soluted by hydrogen peroxide solution. In case of bulk, Mo-Cr alloy have improved chemical durability when it contains up to 20wt% of Cr. Even though Mo70% film is more durable in hydrogen peroxide solution compare to Mo90% and Mo100% film, finally whole film is soluted by the solution. With the fact that more phase separation lead the weakness of durability in case of bulk heat treatment, we tried find the phase separations in the film. But it can not be fully found in the film due to some problems of samples and limation of analysis equipments.
