Thickness Of Photoresist Layer Research Articles

UV-assisted nanoimprint lithography: the impact of the loading effect in silicon on nanoscale patterns of metalens.

This work studies the impact of the silicon (Si) loading effect induced by deep reactive ion etching (DRIE) of silicon master molds on the UV-nanoimprint lithography (NIL) patterning of nanofeatures. The silicon molds were patterned with metasurface features with widths varying from 270 to 60 nm. This effect was studied by focus ion beam scanning electron microscopy (FIB-SEM) and atomic force microscopy (AFM). The Si loading etching effect is characterized by the variation of pattern feature depth concerning feature sizes because smaller features tend to etch more slowly than larger ones due to etchants being more difficult to pass through the smaller hole and byproducts being harder to diffuse out too. Thus, the NIL results obtained from the Si master mold contain different pattern geometries concerning pattern quality and residual photoresist layer thickness. The obtained results are pivotal for NIL for fabricating devices with various geometrical nanostructures as the research field moves towards commercial applications.

Influence of photoresist layer on unetched guided mode resonance filter

During guided mode resonance (GMR) filter fabrication by ion beam etching in a vacuum chamber, the most difficult aspect of the process is accurate control of the groove depth. Because the resonant wavelength of the GMR filter is susceptible to variations in the fabrication parameters, such as the groove depth and period of the grating, it is very difficult to fabricate an ideal GMR filter that has the same parameters as the designed filter. Therefore, to simplify this fabrication process, a GMR filter that can be fabricated without etching is presented in this paper. However, the proposed filter will bring new problems in that the lack of etching may lead to the presence of a residual photoresist layer during the holographic interferometry process. In this paper, we focus on the influence of the residual photoresist layer on the unetched GMR filter. The effects of different photoresist layer thicknesses and different development times are investigated. Using numerical methods based on rigorous coupled wave analysis (RCWA), the spectral curve shows a blue shift with increasing development time. Moreover, with a constant development time and exposure time, there is a red shift with the increase of the photoresist layer thickness. It is found experimentally that this spectral shift trend agrees well with the results of the theoretical analysis.

Single photoresist masking for local porous Si formation

A simple process for local electrochemical porous Si formation on a Si wafer using a photoresist mask was developed. In this respect, the AZ9260 photoresist from MicroChemicals was used, which is easily removed by simple immersion in acetone after the electrochemical process. The photoresist layer thickness and its adhesion to the Si substrate were optimized for increased etch resistance to the anodization solution. Using the above process, mesoporous Si layers as thick as 50 μm were locally formed on the Si wafer through the photoresist mask. The developed process paves the way towards a simple industrial batch Si technology process for the fabrication of mixed Si wafers containing local porous Si areas. These wafers are very interesting for future system-on-chip (SoC) applications, including RF analog/digital and sensors/electronics SoCs.

Mathematical modeling and experimental study on photoresist whirl-coating in convex-surface laser lithography

In this paper, we present a thickness distribution model of photoresist whirl-coating in convex-surface laser lithography based on hydrodynamics and calculus. A multivariable PDE (partial differential equation) of the photoresist-layer thickness distribution has been worked out in constant rate whirl-coating through analyzing and deducing the flow equation on a convex surface. A mathematical model of the photoresist thickness distribution on a convex-surface substrate with respect to various experimental parameters such as the type of photoresist, the viscosity of the photoresist solution, the rotation speed of the spinner, the geometrical dimension of the substrate and the coating time is presented. Furthermore, a homologous uniformity model of the photoresist layer with respect to the rotation speed and the coating time is established during whirl-coating on a convex-surface substrate. By means of a spinner with a high-precision stepping motor, spectroscopy, ellipsometry and profilometry, some experiments were carried out. The results show that the differences between the theoretical thickness distribution model, the uniformity model and their respective measured values are small. According to the first model, it is possible to acquire an arbitrary thickness distribution of the photoresist layer theoretically. The second model could monitor, modify and improve the uniformity of the photoresist-layer distribution on the convex surface so as to facilitate the subsequent lithography procedure and eventually guarantee the line quality in convex-surface laser lithography.

Photolithography on bulk micromachined substrates

Photolithography on high topography substrates, such as the sidewalls or the bottom of cavities and trenches created by bulk micromachining, enables the design of complex three-dimensional structures. When a contact lithography system is used to pattern such substrates, local gaps exist between the mask and the substrate. In this paper we investigate the deformation of patterns as a result of these local gaps. We determine the position accuracy and the minimum size of features that can be patterned as a function of the gap distance. Deformations introduced by the optical system are quantified for a common exposure tool, and compared to pattern deformation due to variations in photoresist layer thickness. Finally, methods to improve the quality of patterns transferred through gaps up to 350 µm are discussed.

Fine patterning of ceramic thick layer on aerosol deposition by lift-off process using photoresist

Ceramic fine patterning using aerosol deposition (AD) method and lift-off process was reported. Pre-baking conditions and thickness of photoresist layer were selected carefully to minimize the dimensions of the patterned structure. As a result, a pattern width less than 10 µm for 2 µm thick PZT and α-Al2O3 AD-deposited layers was obtained on Si substrate at room temperature.

Rigorous electromagnetic modeling of near-field phase-shifting contact lithography

Electromagnetic absorption in a photoresist layer sandwiched between a silicon substrate and a quartz binary phase-shifting mask (employed in near-field phase shift contact lithography) is theoretically analyzed. A rigorous coupled-wave analysis is used to compute the distribution of specific absorption rate (SAR) in the photoresist layer on either monochromatic and polychromatic illumination. The nonuniform distribution of the SAR in the photoresist layer for the printing of high-aspect-ratio features is systematically examined in relation to the geometric dimensions of the binary phase mask, the photoresist layer thickness, and the polarization state of the incident plane wave. Two methods for the improvement of feature resolution and profile are also discussed.

Linewidth variations in photoresist patterns on profiled surfaces

Photoresist thickness nonuniformities in the vicinity of profile steps on substrate surfaces lead to linewidth variations of AZ 1350 photoresist geometries. The effect increases with increasing reflectivity of the substrate, decreasing photoresist layer thickness, and decreasing contrast transfer of the exposure system. It is shown that the photoresist linewidth is maximum when the resist thickness is a multiple of half the exposure wavelength in the resist.