In this paper, we describe the studies conducted at Etec Systems, Inc., an Applied Materials company, using various resists from photoresist manufacturers. Etec undertook this investigation with the objective of creating 257-nm resist processes that would allow the continued use of precoated mask blanks from commercial suppliers. Successful delivery of this technology would allow the industry to adopt next-generation maskmaking systems without having to change current business practices, avoiding being forced to invest heavily in capital equipment, facilities, and the associated technology development programs necessary for local coating of mask blanks. The main criteria used to select an appropriate resist candidate were commercial availability, environmental stability, and across-plate critical dimension (CD) uniformity. The aging data provides an indication of shelf life-pre-exposure ranging from hours to months of delay. Methods for measuring the incoming plate quality are highlighted. The importance of a highly consistent, tightly controlled bake process-post-exposure bake (PEB) and post-apply bake (PAB)-is illustrated in detail. This paper also shows controlled CD structures below the wavelength: 257 nm. The authors describe the processing difficulties encountered while attempting to create a photomask manufacturing-capable process and the techniques used to address the difficulties. Bottom antireflective coatings, photobase, and chemical amplification are areas of focus, as are their resulting effects on the final photomask.
This paper discusses methods used for photoresist selection and etch processing for laser mask patterning tool characterization. A major requirement of a deep ultraviolet (DUV) resist is that is has a storage capability of more than 90 days. This means the material does not have to be coated on demand to deliver exceptional lithographic performance. Process difficulties in the development and implementation of an advanced DUV maskmaking solution and how they are being addressed is also described. The purpose of this paper is to provide a look at the resist, develop, and etch processes being developed at Etec Systems, Inc. for DUV maskmaking applications. Key topics are etch characterization and resist process optimization at 257nm associated with the migration to DUV from i-line manufacturing environments and turning from wafer to mask patterning applications. The paper also shows results of work being done to assess alternative resist chemistries in an attempt to maintain a precoated mask blank option for mask shop use. The paper points out issues to be considered when moving from diazoquinone (DNQ) chemistry to chemically amplified resists (CAR) processing in a mask manufacturing environment.