1. Technical Field
This invention relates generally to the field of semiconductors and, more particularly, to a multilayer pattern transfer process for chemical guides.
2. Related Art
Many technological applications today require the ability to pattern precise structures with a periodicity (pitch) below a certain threshold (e.g., 60 nm). Existing optical lithography approaches are generally capable of high-throughput processing, but the patterning pitch of a single optical lithography step is limited to about 80 nm. One challenge for lithography is to provide tools, materials, and processes that can reliably and efficiently pattern structures with smaller dimensions and reduced pitch.
A significant challenge for directed self-assembly (e.g., DSA+i193 nm) or any patterning technique (e.g., extreme ultraviolet (EUV) lithography) with equivalent feature size and pitch is pattern transfer. Specifically, photoresist patterns are routinely created on multilayer stacks that are needed to reduce reflectivity, improve photoresist adhesion, minimize topographic roughness, and provide stable etch masks for subsequent pattern transfer into the underlying films. For i193 nm based patterning, individual layers such as organic planarizing layers (OPL) are typically 80-120 nm thick. Consequently, pattern transfer of the DSA pattern into this layer will result in OPL structures with aspect ratios ranging from 5:1 to 9:1. Such structures are prone to ‘wiggling’ and pattern collapse that may ultimately limit high-fidelity pattern transfer to the underlying silicon.