Review of metal-containing resists in electron beam lithography: perspectives for extreme ultraviolet patterning

Abstract

Background: Metal-containing resists entered the mainstream semiconductor industry process flow to mitigate the low absorbance of extreme ultraviolet (EUV) radiation by thin films of organic resists that lead to poor sensitivity and their inability to handle rigors of development and etching conditions.Aim: The long and rich history of using metal-containing resists in electron beam lithography can offer interesting lessons, pointers, and insights to the relatively newcomer EUV lithography, which is slightly over a decade old.Approach: Electron beam lithography has been enjoying a considerable amount of freedom in the choice of resist materials for close to 50 years; especially the use of metal-containing resists to attain not only single digit nanometer resolution, higher sensitivity, and etch resistance but also lower line-edge roughness. Here, we make a comprehensive historical review of the progress made in the patterning of metal-containing resists in electron beam lithography and derive insights that can be potentially useful in EUV patterning.Perspectives: Small molecular weight resists are proven to be crucial for achieving higher resolution with low line-edge roughness. Simplifying process flow by reducing etch-stack-layers is conceivable with metal-containing resists, along with direct-patterning of functional materials for heterogeneous integration. Efficient contact hole patterning at tighter pitches may be incumbent on progress in positive-tone resist research.

Induced Chemical Networking of Organometallic Tin in a Cyclic Framework for Sub-10 nm Patterning and Interconnect Application

“…21−26,30−48 While the market of semiconductor industries is skyrocketing, the need for resist compositions for low-cost and efficient patterning of advanced node device architecture, particularly nanopatterning at a single nanometer regime, is quite evident. 3,4 Owing to their importance in specialized applications, the cells of memory devices need complex metal interconnect features. 49 It is to be noted that the fabrication of advanced CMOS devices involves complex processes, wide-ranging advanced materials, and technologies, particularly considering current trends and market demand.…”

Negative Tone Metallic Organic Resists with Improved Sensitivity for Plasma Etching: Implications for Silicon Nanostructure Fabrication and Photomask Production

“…17 Different molecular negative resists have been published that show good performance. 18 Tin-oxo cages are known to work as negative tone photoresists under EUV exposure and in EBL.…”

“…Hydrogen silsesquioxane is an inorganic negative resist and has shown an excellent resolution of 7 nm lines at 30 nm pitch obtained with an exposure dose of 7000 pC/cm at 30 KV . Different molecular negative resists have been published that show good performance . Tin-oxo cages are known to work as negative tone photoresists under EUV exposure and in EBL.…”

“… 17 Different molecular negative resists have been published that show good performance. 18 Tin-oxo cages are known to work as negative tone photoresists under EUV exposure and in EBL. An exposure dose of 1300 μC/cm 2 is required to write 1 μm line/space patterns on the tin-oxo cage layer.…”

Patterning at the Resolution Limit of Commercial Electron Beam Lithography

“…More importantly, patterning on silicon nitride membranes, although good for the demonstration of resolution, severely limits the practical use of materials. It has been long observed that removing the lift-off and etching steps is crucial to achieving sub 10 nm resolution in the direct patterning of functional materials using conventional electron beam lithography. − By circumventing these lithographic steps and using a low-molecular-mass single-source precursor resist, we demonstrated patterning of features whose width is close to the probe diameter. We speculate that the use of single-source precursor resists of high atom economy coupled with improvements in the electron–optical column of conventional electron beam lithography machines incorporating spherical aberration correctors would make direct patterning of functional materials at an angstrom scale on silicon substrates a distinct possibility.…”