Resist Reflow Modeling Including Surface Tension and Bulk Effect

Abstract

Resist reflow is a simple and cost-effective technique of fabricating a sub-100 nm contact hole (CH) pattern. The predominant factors affecting resist reflow include baking temperature and time, the volume surrounding the CH, the pattern layout, and the resist material properties. Thus, to optimize the layout design and process parameters, we developed a simple resist flow model that could predict the resist reflow tendency as functions of the reflow temperature, CH size, and the initial shape, the pitch and irregularity of CH array. The basic fluid equation was used to express the flow of the resist, and the variations of viscosity and density as functions of reflow temperature and time were considered. We also included the surface tension and bulk effect in our reflow model, so that we could see the difference in CH surface roundness with different surface tensions. We could also see the difference in CH size among the irregular CHs and those with different duty ratios by including the bulk effect. Moreover, we simply attempted to correct the critical dimension difference with pitch as imposing a bias on each afterdevelopment contact hole.

Vertically tapered layers for optical applications fabricated using resist reflow

“…The resist reflow is mainly used for surface planarization and as a low-cost IC-compatible technique for the fabrication of micro-lenses [7][8][9]. The resist reflow technique is also used in the fabrication of submicron contact holes [10,11]. Recently, resist reflow has also been investigated for IC-compatible fabrication of tapered structures with a relatively large taper ( z/L = 10 μm/1 mm) for optical coupling [3,6].…”

Anisotropic Resist Reflow Process Simulation for 22 nm Elongated Contact Holes

“…2) H is the height (300 nm) of the resist. By using the constant values given above and adjusting unknown constants to fit the experimental data, we correctly predicted the experimental behavior, 2) which is dependent on various parameters, such as pitch, random array, and reflow temperature and time. We calculated one-dimensional (x) resist reflow with depth (z) and one-dimensional (y) resist reflow with depth (z).…”

“…By homemade RRP simulation, we could predict the CH RRP tendency as a function of temperature, adhesion strength, viscosity, surface tension, and so on. 1,2) However, we could not apply RRP to elongated CHs because their initial structure is more complex than that of normal CHs. Moreover, we need to consider two target critical dimensions (CDs), because elongated CHs have two CDs for the major and minor axis.…”

Critical Dimension Control for 32 nm Node Random Contact Hole Array Using Resist Reflow Process

“…The viscosity, adhesion strength, RRP temperature, 1) and surface tension 2) of photoresists are the main factors of RRP. To solve RRP behavior we use the Navier-Stokes equation in the two-dimensional (2D) Cartesian coordinate system,…”