Double patterning based on existing ArF lithography technology is one of the most promising candidates for sub-40nm half-pitch devices. Several variation of double patterning processes have been reported by research groups, including a dual-trench process (litho-etch-litho-etch) and a dual-line process (litho-litho-etch). Between these, the dual-line process is attracting the most attention because it is a simple process that achieves high throughput. However, there is concern that the second lithographic process damages the first litho patterns in the dual-line process. Therefore, new technology must be developed to keep the configuration of first litho patterns during the second lithographic step for this patterning process to be practical.
Recently, we have succeeded in forming sub-40nm half-pitch litho patterns by the introduction of a new "freezing" step to this process. This step involves covering the first litho pattern with chemical freezing materials to prevent damage by the second litho pattern creating a dual-line process composed of litho-"freezing"-litho-etch processes. In this paper, the details of dual-line process including a "freezing" step are explained and sub-40nm half-pitch litho patterns by this process are shown.
Contact hole shrink process is becoming more important option for 45nm node design rules. In general, lithography of contact hole has been harder than that of line and space application due to the low contrast of incident light. The contact hole size for 45nm node device will be around 60nm and this hole size will be the limit of 193nm lithography. High NA exposure tool for 193nm lithography achieves 60nm contact hole resolution, but both under dose margin and depth of focus will be limited. This fact results in the insufficient process window of 193nm lithography. Thus some supporting process should be necessary and a chemical shrink process is one of the possible approach to resolve 60nm contact hole with appropriate process margin. The general chemical shrink process is as follows. Chemical Shrink Material (CSM) is coated on patterned photoresist, and following bake process controls chemical cross-linking reaction and forming a layer insoluble into the developer. As a result pattern size is reduced to desired CD. However current CSM has several issues: i.e. inferior etching durability of CSM than that of 193nm resist and pattern profile degradation after the process. This will be the critical problem for pattern transfer process using CSM. From this point of view, we developed a novel CSM which has good etching durability compared with 193nm resist and does not have a pattern profile degradation. This material consists of aromatic moiety to satisfy good etching durability. Also, the shrink rate and amount are not pitch dependent.