Developed profile of holographically exposed photoresist gratings

Abstract

A simulation of the profile of holographically recorded structures in photoresists is performed. In addition to its simplicity this simulation can be used to take into account the effects that arise from exposure, photosensitization, development, and resolution of positive photoresists. We analyzed the effects of isotropy of wet development, nonlinearity of the photoresist response curve, background light, and standing waves produced by reflection at the film-substrate interface by using this simulation, and the results agree with the experimentally recorded profiles.

Systematic study of resonant transmission effects in visible band using variable depth gratings

“…The next step in the LIL process consists in dissolving the resist in a developer. As the resist development rate depends monotonically on the absorbed energy dose 31 , the topology of the developed surface corresponds to the total intensity distribution of the previous exposition step. Figure 1 demonstrates a usual setup with two point sources, where the plane wave approximation is applicable in a relatively small zone far from the sources.…”

Subwavelength diffraction gratings with macroscopic moiré patterns generated via laser interference lithography

“…In the second step, the absorbed light changes the resist chemical structure and makes the exposed areas more soluble for the developer. Contrast curves describing the development rate / exposure dose dependence are often used to numerically predict the final grating profile [30][31][32]. Fig.…”

Metallic submicrometer sieves fabricated by interferometric lithography and electroforming

“…Figure 3(a) shows a simulation of a typical light pattern resulting from the superimposition of two successive orthogonal fringe patterns. In figure 3(b) is shown a simulation of the resulting profile recording in a positive photoresist, assuming a linear development condition (development rate proportional to the local light dose) [10,11]. Although this simple model does not consider the nonlinearity of the development [10] nor its isotropic action [11], it is useful to analyze some particularities of the interferometric lithography: As can be seen there is an asymptotic behavior indicating that the d/ range between 0.25 and 0.15 is more appropriate for interference lithography.…”

“…In figure 3(b) is shown a simulation of the resulting profile recording in a positive photoresist, assuming a linear development condition (development rate proportional to the local light dose) [10,11]. Although this simple model does not consider the nonlinearity of the development [10] nor its isotropic action [11], it is useful to analyze some particularities of the interferometric lithography: As can be seen there is an asymptotic behavior indicating that the d/ range between 0.25 and 0.15 is more appropriate for interference lithography. For ratios greater than 0.3 the repeatability and homogeneity of the recorded structures is very poor and ratios smaller than 0.15 require long development times that my release the photoresist during development.…”

“…The maximum height (h) of the photoresist structure depends on its diameter (d). The maximum aspect ratio (h/d) that can be reached in the photoresist structure depends on several parameters such as isotropy of the development process [11], contrast of the interference fringe pattern [11], the nonlinearity of the development [10,11], the absorption of the photoresist, etc. In our case by using a high contrast fringe pattern and a low absorption wavelength, with the AZ 1518 we can reach aspect ratios (h/d) of up to 4.…”