Most semiconductor companies are using Bottom Anti-Reflective Coating (BARC) on their lithography process to
reduce bottom reflectivity, which is cause of standing wave, pattern collapse, and bad pattern profile, and to improve
lithographic performance. BARC has been diversified to adapt to the wavelength of exposure light and refractive indices
of photoresists and substrates. Recently, many semiconductor companies introduce new process, such as immersion
process and double patterning process, to get high resolution for next generation semiconductor and they are trying to
apply these processes to their mass production. Among those process solutions, a strong candidate for high resolution is
introduction of hyper NA(Numerical Aperture) exposure tool, using immersion process. There is one thing to solve for
BARC material when immersion process is applied. It is reflectivity. As NA of exposure tool increases, reflectivity from
a substrate also increases, simultaneously. We simulated the difference of reflectivity with increasing NA and we found a
proper way how to control reflectivity on immersion process with refractive indices of BARC. We will report simulation
data for immersion process and introduce our new developed BARC for hyper NA process in this paper.
As the feature size becomes smaller, it is difficult for the lithography progress to
keep pace with the acceleration of design rule shrinkage and high integration of memory device.
Extreme Ultra Violet Lithography (EUVL) is a preferred solution for the 32nm node. In this
paper, we have synthesized two types of polymers. One is based on hydroxy phenol, the other
is based on hydrocarbon acrylate type polymer. We have diversified each polymer type
according to different activation energies for deprotection reaction. In this experiment, we have
observed on the resist lithographic performance such as resolution, LER (Line Edge
Roughness), photo-sensitivity, and out-gassing during exposure. Different properties according
to activation energy were well explained by acid diffusion and polymer free-volume.
Recently, there are lots of interest in using chemical amplification (CA) on electron beam lithography for application to photo mask fabrication, direct writing, and projection printing. E-beam resists introducing chemically amplification concepts provide superior lithographic performance in comparison with traditional non CA E-Beam resist in particular high resolution and sensitivity. In first approach, we applied CA concepts to acetyl polymer based E-beam resist (resist thickness: 4,000Å), which can print fine images (<100nm), meet sensitivity (10μC/cm2), and have stability against post exposure delay (PED)(>10hrs) using 50KeV E-beam exposure tool. But, there is vacuum delay problem (40nm CD shrinkage/5hrs) due to thermally unstable blocking group in polymer. To prevent this vacuum delay problem due to polymer-inherent thermal instability in low-activation-energy-acetal polymer, we newly designed various poly(hydroxystyrene-acrylate) copolymer derivatives that contained thermally stable (acrylate) acid-blocking group. In this presentation, first we will discuss the chemistry of newly designed copolymer derivatives, and second, vacuum delay effects and other lithographic performances (resolution, sensitivity, line edge roughness) of these resist systems.
To accomplish minimizing feature size to sub 100nm, new light sources for photolithography are emerging, such as ArF(193nm), F2(157nm), and EUV(13nm). However as the pattern size decreases to sub 100nm, a new obstacle, that is pattern collapse problem, becomes most serious bottleneck to the road for the sub 100 nm lithography. The main reason for this pattern collapse problem is capillary force that is increased as the pattern size decreases. As a result there were some trials to decrease this capillary force by changing developer or rinse materials that had low surface tension. On the other hands, there were other efforts to increase adhesion between resists and sub materials (organic BARC). In this study, we will propose a novel approach to solve pattern collapse problems by increasing contact area between sub material (organic BARC) and resist pattern. The basic concept of this approach is that if nano-scale topology is made at the sub material, the contact area between sub materials and resist will be increased. The process scheme was like this. First after coating and baking of organic BARC material, the nano-scale topology (3~10nm) was made by etching at this organic BARC material. On this nano-scale topology, resist was coated and exposed. Finally after develop, the contact area between organic BARC and resist could be increased. Though nano-scale topology was made by etching technology, this 20nm topology variation induced large substrate reflectivity of 4.2% and as a result the pattern fidelity was not so good at 100nm 1:1 island pattern. So we needed a new method to improve pattern fidelity problem. This pattern fidelity problem could be solved by introducing a sacrificial BARC layer. The process scheme was like this. First organic BARC was coated of which k value was about 0.64 and then sacrificial BARC layers was coated of which k value was about 0.18 on the organic BARC. The nano-scale topology (1~4nm) was made by etching of this sacrificial BARC layer and then as the same method mentioned above, the contact area between sacrificial layer and resist could be increased. With this introduction of sacrificial layer, the substrate reflectivity of sacrificial BARC layer was decreased enormously to 0.2% though there is 20nm topology variation of sacrificial BARC layer. With this sacrificial BARC layer, we could get 100nm 1:1 L/S pattern. With conventional process, the minimum CD where no collapse occurred, was 96.5nm. By applying this sacrificial BARC layer, the minimum CD where no collapse occurred, was 65.7nm. In conclusion, with nano-scale topology and sacrificial BARC layer, we could get very small pattern that was strong to pattern collapse issue.