The semiconductor industry is pursuing several process options that provide pathways to printing images smaller
than the theoretical resolution limit of 193 nm projection scanners. These processes include double patterning, side
wall deposition and pitch division. Pitch doubling lithography (PDL), the achievement of pitch division by addition
of a photobase generator (PBG) to typical 193 nm resist formulations was recently presented.<sup>1</sup> Controlling the net
acid concentration as a function of dose by incorporating both a photoacid generator (PAG) and a PBG in the resist
formulation imparts a resist dissolution rate response modulation at twice the frequency of the aerial image.
Simulation and patterning of 45 nm half pitch L/S patterns produced using a 90 nm half pitch mask were reported.<sup>2</sup>
Pitch division was achieved, but the line edge roughness of the resulting images did not meet the current standard.
To reduce line edge roughness, polymer bound PBGs and polymer bound PAGs were investigated in the PDL resist
formulations. The synthesis, purification, analysis, and functional performance of various polymers containing PBG
or PAG monomers are described herein. Both polymer bound PBG with monomeric PAG and polymer bound PAG
with monomeric PBG showed a PDL response. The performance of the polymer bound formulations is compared to
the same formulations with small molecule analogs of PAG and PBG.
Pitch division lithography (PDL) with a photobase generator (PBG) allows printing of grating images with twice
the pitch of a mask. The proof-of-concept has been published in the previous paper and demonstrated by
others. Forty five nm half-pitch (HP) patterns were produced using a 90nm HP mask, but the image had line
edge roughness (LER) that does not meet requirements. Efforts have been made to understand and improve the
LER in this process. Challenges were summarized toward low LER and good performing pitch division.
Simulations and analysis showed the necessity for an optical image that is uniform in the z direction in order for
pitch division to be successful. Two-stage PBGs were designed for enhancement of resist chemical contrast. New
pitch division resists with polymer-bound PAGs and PBGs, and various PBGs were tested. This paper focuses on
analysis of the LER problems and efforts to improve patterning performance in pitch division lithography.
Subsequent to 45 nm node, immersion lithography using topcoat process is approaching its next step for mass
production. However, microfabrication using immersion topcoat leads to increase in cost due to increase in process
steps. In order to deal with this problem, high throughput scanners equipped with a wafer stage which moves at higher
speed are under development. Furthermore, as resist process compatible with such high speed scanners, non-topcoat
resist is available and seems promising in reducing costs of the resist process. Non-topcoat resist contains hydrophobic
additives which are eccentrically located near the film surface. Because non-topcoat resist enables the formation of a
more hydrophobic surface, non-topcoat resist process is more suitable for high-speed scanning than topcoat resist
process. In the topcoat process, the function of topcoat material and resist material is separated. That is, the resist
material and the topcoat material are responsible for lithographic performance and immersion scanning performance,
respectively. However, the non-topcoat resist is expected both performances. That is, the non-topcoat resist are
required a fine resist profile, small LWR, and low development defects at high speed immersion scanning. In this
paper, we report the application of non-topcoat resist in 22 nm node devices. We investigate the influence of
hydrophobic additives on imaging performance in several base polymers. Additionally, the influence of chemical
species, molecular weight and amount of hydrophobic additive are investigated. Scan performance is also estimated by
dynamic receding contact angle using pin scan tool. 22nm node imaging performance is evaluated using Nikon NSRS610C.
The surface characteristics and lithographic performance of non-topcoat resist for 22 nm node devices are
The combination of immersion lithography and reticle enhancement techniques (RETs) has extended 193nm
lithography into the 45nm node and possibly beyond. In order to fulfill the tight pitch and small critical dimension
requirements of these future technology nodes, the performance of 193nm resist materials needs to further improve. In
this paper, a high performance 193nm photoresist system based on fluorosulfonamide (FSM) is designed and
developed. The FSM group has good transparency at 193nm. Compared to the commonly used hexafluoroalcohol
(HFA) group, the trifluoromethyl sulfonamide (TFSM) functionality has a lower pKa value and contains less fluorine
atoms. Polymers containing the TFSM functionality have exhibited improved dissolution properties and better etch
resistance than their HFA counterparts. Resists based on the FSM-containing polymers have shown superior
lithographic performance for line, trench and contact hole levels under the 45nm node exposure conditions. In
addition, FSM resists have also demonstrated excellent bright field and dark field compatibility and thereby make it
possible to use one resist for both bright field and dark field level applications. The structure, property and lithographic
performance of the FSM resist system are reported.
In the current optical lithography, the resolution is being pushed for 45 nm half-pitch, and the chemically amplified
resist will be used for wide variety of applications including immersion lithography. So far the chemical amplification
has brought high performance for lithography. In the future, for the ArF lithography beyond 45nm half-pith, it will be
important to control pattern size. On the other hand, chemically amplified resist which utilized acid catalyzed deprotecting
reaction is sensitive to physical and chemical factor. Thus, there are various factors in the each process
(Resist coating, Pre bake, Exposure, Post exposure bake, Development and Rinse) to cause the resist blur. For example,
it's acid diffusion on PEB. The influence of these factors for the resist blur is a significant issue for lithography beyond
45 nm half-pitch. Therefore the need to reduce these factors on the resist blur becomes higher in order to extend the ArF
lithography beyond 45 nm half-pith.
In this paper, acid diffusion coefficient (<i>D</i>) and resist blur with changing anion size of PAG, size of protecting group
in typical ArF resist was reported. The relationship between acid diffusion coefficient and resist blur was discussed on
the basis of their difference in structure and characteristics.