In this paper we investigate fundamental resist properties to enhance resolution and focus margin for immersion
contact hole patterning. Basic chemistry factors have been used to manipulate the iso-focal region (the region of
smallest critical dimension variation through focus) of the photoresist and study the impact on resolution and focus
margin for small isolated contact holes. Acid diffusion length is one of the key factors investigated, which can be
controlled by polymer, PAG, quencher, bake temperature and bake time. The various criteria investigated for this study
were: focus and exposure latitude for dense L/S, dense C/H and semi-dense C/H. The effect of manipulating the acid diffusion of the photoresist on imaging small contact holes was verified using ultra-high NA immersion imaging at 1.35
KEYWORDS: Reflectivity, Lithography, Critical dimension metrology, Line width roughness, Immersion lithography, Optical lithography, Photomasks, Scanning electron microscopy, Electroluminescence, Control systems
Reflectivity comparison study of bottom anti reflectivity coating (BARC) was investigated at 30nm node devices with same gate width at different pitch sizes. The goal of this study is to elucidate the practical target of reflectivity for high NA immersion lithography especially focusing on the changes in the CD variation. Using double patterning technology (DPT) and single patterning technology (SPT) patterns in high NA systems, we studied the impact of reflectivity to the lithography performance for various ARC thicknesses.
A strong dependence of n, k values (of BARC and substrate) on reflectivity was confirmed by simulation. Standing wave effects were investigated by vertical profiles inspection and changes in lithographic performances. Finally, we investigated the critical dimension uniformity (CDU), and line width roughness (LWR) variations for various reflectivities using hard mask substrates. Our experimental and simulation results clearly show that a 0.1% reflectivity target is highly recommendable for the sub-30 nm device process using high NA immersion lithography.
Virtual OPC concept is suggested for soothing the problem that the roadmap of semiconductor devices proceeds the rate of development of exposure tools. Virtual OPC uses the simulated CD data for an OPC modeling instead of the measured CD data. For successful virtual OPC, the extreme accuracy of the simulation is required for obtaining the simulated CD data close to the actual CD values. In this paper, our efforts to enhance the simulation accuracy are presented and the accuracy of simulated sample data for OPC is verified. The applicability of virtual OPC to the production of devices was verified by performing the virtual OPC using the simulated sample data at 1.2 NA lithography and the result also is presented.
ArF lithography is in the early stage of mass production and also is going to be further extended to 40nm generation
with the aid of immersion lithography. Therefore, it is important to make ArF process production-friendly and extendible
for the continuous shrinkage of design rule. Development of ArF process has proceeded with the increase of numerical
aperture (NA) and the decrease of resist thickness, which are causing several problems both in mass production and
development stage. NA is going to exceed unity in immersion, which necessitates the use of dual bottom antireflective
coating (BARC) with increased process complexity and cost. Resist thickness, on the other hand, is expected to further
decrease below 100 nm. Therefore, it is inevitable to use additional hard masks, which increases production cost due to
chemical vapor deposition (CVD) process. Here we disclose our novel spin-on hard mask system with dual BARC
property to overcome both problems aforementioned. Spin-on hard mask composed of two layers of siloxane and carbon
materials shows high etch selectivity between thin resist and several substrates. Composition and etch chemistries of two
layers are intensively studied to give CVD-comparable step-by-step etch selectivity to transfer various patterns of thin
resist including line/space and contact holes to the various substrates. In addition, optical properties of two layers are
finely designed from comprehensive optical simulation to be applied to various generation of ArF lithography from dry
to immersion process. Such designed optical properties are incorporated to the above two layers of spin-on hard mask.
This novel system is under extensive optimization to be applied to various generation of ArF lithography from mass
production to the most pioneering semiconductor devices utilizing immersion lithography.