High Refractive Index Nanocomposite Fluids for Immersion Lithography
High Refractive Index Nanocomposite Fluids for Immersion Lithography
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DOI：
10.1021/la8026896
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发表时间：
2009-02-17
期刊：
影响因子：
3.9
通讯作者：
Jahromi, S.
中科院分区：
文献类型：
--
作者：
Bremer, L.;Tuinier, R.;Jahromi, S.
从理论和实验的角度探讨了在浸没式光刻中使用纳米粒子分散体作为高折射率流体的概念。在理论部分，我们表明，凝胶和脱混可以控制在高固体分散，需要实现高（折射率），通过使用短稳定刷。我们用统计热力学和用液态方法计算的渗流来考虑流体与流体的分离。当发生脱混或渗透时，纳米颗粒的分散不适合浸没光刻。假设稳定悬浮液中颗粒和空间稳定剂作为具有范德华引力的硬球，估计了稳定悬浮液稳定层的最小厚度。由于范德华引力可以与粒子和色散介质的光学性质有关，因此也可以估计复合浸没流体可以获得的折射率。使用已知在193nm波长高度透明的材料，可以获得高于1.8的指数。由于紫外线吸收的蓝移，其他具有更高指数的材料预计在193nm处是透明的，并且可以实现更高的指数。在实验中，我们证明可以制备直径约为4 nm的悬浮液，在波长为193 nm时，连续相的折射率提高0.2。这些色散体的折射率和密度与色散相的体积分数成正比，并表明复合流体的折射率可以很好地由组分的光学性质来预测。此外，通过二氧化硅纳米颗粒的分散进行了成功的成像实验。这些发现表明，使用纳米颗粒分散体的浸没光刻确实是可能的。
The concept of using dispersions of nanoparticles as high refractive index fluids in immersion lithography is examined both from a theoretical and experimental point of view. In the theoretical part we show that gelation and demixing can be controlled in high solid dispersions, needed to achieve a high (refractive) index, by using short stabilizing brushes. We considered both fluid-fluid demixing by using statistical thermodynamics and percolation, computed using liquid-state approaches. Whenever demixing or percolation takes place, the nanoparticle dispersion is unsuited for immersion lithography. The minimum thickness of the stabilizer layer of a stable suspension is estimated assuming particles plus steric stabilizer to act as hard spheres with van der Waals attraction between the cores. Since the van der Waals attraction can be related to the optical properties of the particles and dispersion medium, it is also possible to estimate the refractive index that can be attained with composite immersion fluids. Using materials that are known to be highly transparent in the bulk at a wavelength of 193 nm, indices above 1.8 can be attained. Other materials with higher indices are expected to be transparent at 193 nm due to a blue shift of the UV absorption and enable much higher indices. In the experiment, we show that it is possible to prepare suspensions with particles of about 4 nm diameter that increase the refractive index of the continuous phase with 0.2 at a wavelength of 193 nm. The refractive index and density of such dispersions are proportional to the volume fraction of the disperse phase, and it is shown that the refractive index of the composite fluid can be predicted very well from the optical properties of the components. Furthermore, successful imaging experiments were performed through a dispersion of silica nanoparticles. These findings lead to the conclusion that immersion Lithography using nanoparticle dispersions is indeed possible.