Proximity effect (electron beam lithography)

About: Proximity effect (electron beam lithography) is a research topic. Over the lifetime, 940 publications have been published within this topic receiving 8508 citations.

High resolution electron‐beam lithography on thin films

Abstract: The influence of electron scattering on the resolution of electron‐beam lithography has been studied. Theoretically, we have used two different Monte‐Carlo approaches to study the spatial extent of energy dissipation in a thin film of electron sensitive polymer film coated on various thicknesses of silicon substrates. The two Monte‐Carlo approaches are the conventional continuous‐slowing‐down approximation approach and the direct simulation approach in which individual inelastic scattering is taken into account. Experimentally, we have exposed lithographic patterns on the structures mentioned above. Agreement between both Monte‐Carlo approaches and experiment is satisfactory. Results show that higher resolution in electron beam lithography can be achieved by using thin electron sensitive resist layers and thin substrates. Improvement in proximity effect is also obtained for thin structures.

Silicon transfer layer for multilayer resist systems

Abstract: Thin film silicon is found to be a desirable interlayer material for e‐beam lithography with multilayer resist systems. It is easily etched in CF4 plasma (Si/PMMA: 30/1) yet resists O2 reactive ion etch (Si/HPR: 1/300). It is sufficiently conductive to avoid charging effects, both during lithography and SEM inspection. High optical contrast aids in inspection. Monte Carlo calculations show that a 2.5 μm bottom layer of polymer can substantially alleviate the proximity effect, even with an 80 nm Si interlayer. Pattern transfer with less than 100 nm linewidth loss is demonstrated. Lines as narrow as 200 nm in 2 μm of Hunt positive resist were holographically produced.

Low-Energy E-Beam Proximity Lithography (LEEPL): Is the Simplest the Best?

Abstract: Low-energy e-beam proximity lithography (LEEPL) is proposed as the simplest integrated circuit lithography for minimum feature sizes ≤0.1 µm. This new e-beam lithography is similar to 1× X-ray proximity lithography except that the X-ray beam is replaced with a beam of low-energy electrons of 2 kV. This low e-beam energy permits the use of single-crystal 0.5-µm-thick silicon stencil masks without an absorbing metal layer of high atomic number. This membrane mask is thick enough for good heat conduction and thin enough for feature sizes ≤0.1 µm. Mask distortion caused by fabrication can be corrected by a fine-tuning deflector. Therefore, a mask with a residual distortion of more than 100 nm is acceptable. This eliminates the main difficulty of X-ray proximity lithography. The proposed system is not affected by a space-charge effect in the electron optics column, and a proximity effect with respect to both wafer and mask writings, and it is fundamentally low-power lithography which needs no special cooling system. The analysis shows that the e-beam column can be made entirely of electrostatic components to achieve sufficient resolution. For an appropriate resist process for this low-energy e-beam, we propose a bilayer process such as the chemical amplification of resist lines (CARL) process which consists of a chemically amplified thin deep ultraviolet (DUV) photoresist and a thick planarizing layer as a starting point. We estimated a throughput of about 40 12 inch wafers per hour and a resolution of a significantly less than 50 nm.

UV thermoresists: sub-100-nm imaging without proximity effects

Abstract: Thermoresists offer the possibility of greatly enhanced resolution and process window, mainly depth of focus, using conventional masks and modified conventional steppers. Unlike photoresists, which respond to total exposure, thermoresists ignore all exposures below their threshold provided that the exposures are separated in time by more than a few tens of nanoseconds. This allows thermoresists to ignore sidelobes and stray light that result from improving the resolution and depth of focus if nearby features are not imaged at the same time. Conventional steppers can be modified by adding a piezoelectrically-scanned microlens array above the mask and by adding an apodizing function to the reduction lens system. The microlens array eliminates all optical proximity effects by breaking the image into an array of dots that are moved between pulses of the stepper's laser, causing image features to be separated in time as well as space. Thermoresists also offers an advantage when imagin on non-planar materials if the intensity of the exposure is adjusted so that image spots will only reach the threshold of the resist when they are in focus. By making multiple image exposures with the focus shifted towards and away from the resist, a high-resolution image can be produced on a rough surface.

Proximity effect compensation in scattering-mask lithographic projection systems and apparatus therefore

Abstract: In electron beam lithography, formation of micron and submicron size features is complicated by undesired nonuniform (pattern-density dependent) resist exposure from electrons backscattered from the underlying substrate. The disclosed technique uses a combination of a scattering mask and a scattering filter to add a leveling background exposure automatically and thus provide uniform contrast across the entire exposure pattern.