Pcm Resist Process With Rie Development Method Applied For The Aluminum Etching Process

Abstract

A new Portable Conformable Mask (PCM) bilayer process has been developed that uses Reactive Ion Etching (RIE) for development of the bottom PMMA layer to produce steep resist profiles. This new process uses a gas mixture of ( C2F6+CHF3 ) that effectively removes the PMMA resist, interfacial layer and that has a high rate of anisotropic development for the bottom PMMA layer --- combining the advantage of performance on a trilayer process with the relative simplicity of PCM. The development rate of the top resist layer is very small and result in very little thickness loss of the top imaged positive resist. The top layer of positive photoresist remains intact to protect the PMMA during etching process. This eliminates the requirement of an intermediate barrier layer or special resist materials. For the additional protection during etching process, the resist can be hardened by a deep ultraviolet ( DUV ) exposure after RIE development of PMMA and it is observed that small amount of DUV exposure effectively improves the plasma resistance on this resist structure. This new PCM process has been used for the dry etching process of aluminum film using a gas mixture of BC13+CF4+02. An optional layer of sputtered amorphous silicon can be used between the aluminum and the PMMA to act as an antireflection layer. Using this process and an EATON-OPTIMETRIX MODEL 8605H wafer stepper, 0.6μm line and space of equal width have been exposed and etched into 9000A of aluminum film. Critical process steps are given, the effects of variation in process parameters are described, and SEM photographs of the final results are shown.