A maskless three-dimensional (3D) microfabrication method based on a digital micromirror device (DMD) is proposed for high lateral and vertical resolution. A substrate is scanned laterally under virtual masks of the DMD. The masks are allocated to a large number of virtual slices, all of which are projected in a single scan of the stage. A theoretical model for the cumulative dose distribution in a photoresist is derived and used to predict the resulting 3D profile. Experiments showed that the proposed method is promising for avoiding the stair-step problem and preventing misalignment errors.

Manufacturing fine metal mask (FMM) is the biggest hurdle to realize UHD grade AMOLED pixels for smartphone applications and even higher resolutions such as virtual reality displays. We have developed 800ppi or more grade fine metal mask processing system via femtosecond laser with unique thermal damage free process. Thanks to the unique processing strategy, without sacrificing the processing speed, UHD grade FMM is realized for AMOLED mobile displays. KeywordsFine metal mask; ultrashort pulse laser; UHD (Ultra High Definition); taper control; thermal effect free process

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We propose optical proximity corrections (OPCs) for digital micromirror device (DMD)-based maskless lithography. A pattern writing scheme is analyzed and a theoretical model for obtaining the dose distribution profile and resulting structure is derived. By using simulation based on this model we were able to reduce the edge placement error (EPE) between the design width and the critical dimension (CD) of a fabricated photoresist, which enables improvement of the CD. Moreover, by experiments carried out with the parameter derived from the writing scheme, we minimized the corner-rounding effect by controlling light transmission to the corners of a feature by modulating a DMD.

This paper investigated the effects of femtosecond laser beam polarization on ablation efficiency and microstructure symmetricity for 64FeNi alloy (Invar) sheet processing to fabricate fine metal masks. It was found that the ablation efficiency for linear polarization was approximately 15% higher than that for circular polarization due to electric field enhancement induced by low-spatial-frequency laser-induced periodic surface structures (LIPSS). The hole size and sidewall taper angles for the microstructures generated by linear polarization were asymmetric, whereas those generated by circular polarization were symmetric due to non-oriented LIPSS. The asymmetric and symmetric three-dimensional microstructure profiles, measured by using a confocal laser scanning microscope, were verified by employing an analytical model that was derived using the total input fluence and the ablation rates for linear and circular polarizations, respectively.