Nanometer-scale imaging characteristics of novolak resin-based chemical amplification negative resist systems and molecular weight distribution effects of the resin matrix

Abstract

Molecular weight distribution effects of novolak resin-based chemical amplification negative resist systems are investigated for electron-beam lithography. The resist systems investigated consist of onium salts as an acid generator, a methoxymethyl melamine crosslinker, and a conventional/fractionated novolak resin matrix. Delineated patterns of both types of resist systems are compared to evaluate submicron-scale resolution. The conventional novolak resin-based system shows higher contrast than the fractionated one. High aspect ratio patterns are resolved for the conventional novolak-based resist, whereas poor results are obtained for the fractionated resin-based one on the submicron scale. Very thin films (30 nm) of both resist systems are delineated with a finely focused electron beam (diameter: approximately 2 nm at 5 kV) from a scanning electron microscope. Nanometer-scale edge roughness (nanoedge roughness) is observed for the conventional novolak resin-based resist. On the contrary, the degree of nanoedge roughness is greatly reduced for the fractionated one.

A study on the material design for the reduction of LWR

“…For the patterning of such an ultra-narrow patterns (<32nm), reduction of line-width roughness (LWR) becomes a critical issue, i.e., the demand of LWR reduction reaches down to 3 nm (3σ: σ is standard deviations). 1 For decades, the factors that contribute to LWR, such as molecular structures of resist polymers [2][3][4] and some processing parameters including aerial image fluctuations caused by mask roughness 5 and degradation of optical image, [6][7] distributions of deblocked polymer, [8][9] photoacid diffusion, [10][11] and development process 12 , have been investigated. It has been considered that LWR is a consequence of the complex interaction between the spatial distribution in polymer composition that results from exposure, baking, and development processes.…”

Radiation Chemistry in Chemically Amplified Resists

“…Since the early stages of this research, the effects of polymer properties have been investigated. The sizes of molecules (molecular weight or gyration radius), 12,13) molecular dispersion, 14,15) and rigidity 16) have been reported as causes of LER, particularly from the viewpoint of dissolution phenomena (development). These factors obviously affect LER because a polymer molecule is a minimum block for dissolution.…”

Challenges in Development of Sub-10 nm Resist Materials

“…The causes of LER formation have been intensively investigated [9][10][11][12][13]. Among many causes reported, the essential cause for latest chemically amplified resists is the inhomogeneous distribution of dissolution inhibitors (protected units in the case of chemically amplified resists) at the boundary between the soluble and insoluble regions of resist film.…”