Three-color lithography (3CL) can produce high-resolution features using visible light. This technique uses one beam to pre-activate a photoresist, a second beam to deactivate it, and a third beam to activate the pre-activated regions that have not been deactivated. The deactivation beam is used to trim features, allowing for improved feature size and resolution. Although this 3CL was pioneered with 2-photon excitation, the ultimate goal is to use thin films with linear excitation, such that it is compatible with industrial requirements. We will discuss the first thin-film 3CL studies, which are a promising step towards large-area patterning.
The demand to create ever finer features at ever tighter pitches has fueled the drive towards lithographic methods that use radiation with the shortest possible wavelength. This approach, however, faces a considerable number of technological challenges that need to be addressed. An alternative, cost-effective approach is multicolor lithography. Inspired by the technology for superresolution in optical microscopy, multicolor visible light approaches led to achieving features down to λ/20 using 3-D multiphoton absorption polymerization (MAP). Although these original efforts in the field involved the use of two colors of light, it has become apparent that 3-color approaches will be required to address the need to pack features together tightly. In this work, we present some of the latest progress in the benchmarking and development of three-color photoresist materials, and demonstrate how the addition of a third color in the exposure scheme can lead to substantial improvements in resolution.
A three-color lithographic (3CL) scheme has been developed to achieve high resolution through the use of visible and near IR wavelengths. The intrinsic kinetic properties of 3CL materials are used to optimize the efficiency of deactivation, a crucial step in overcoming background buildup in multipatterning using this technique. To study materials of interest for 3CL, we have developed an in situ technique to monitor exposure and deactivation. A two-beam interference pattern is polymerized on a photoresist and the diffraction of a continuous-wave probe laser is measured in order to identify the polymerization and deactivation thresholds. Here we present preliminary results on the time dependence of the deactivation efficiency of 3CL materials and in situ detection of polymerization thresholds. This is a study of the kinetics for polymerization of 3CL materials to optimize the 3CL scheme to achieve the highest resolution and elucidate its mechanism.
Multicolor photolithography using visible light holds the promise of achieving wafer-scale patterning at pitches on the 10 nm scale. Although substantial progress has been made on multicolor techniques, a number of challenges remain to be met before the ultimate resolution of these methods can be reached. These challenges include the development of improved materials, creation of high-quality thin films, transitioning to exposure schemes that rely completely on linear absorption, scaling up to large-area patterning, and developing methods for effective pattern transfer. This paper discusses the state of the art in multicolor photolithography, presents some of the most recent advances in this field, and examines the prospects moving forward.