Application of optical lithography for high aspect ratio microstructures

Abstract

Articles you may be interested inAg2Te/As2S3: A high-contrast, top-surface imaging resist for 193 nm lithography J.Interest in thick photoresist applications is steadily growing. Besides the bump fabrication and wire interconnect technology, the process of patterning thick layer photoresists by UV lithography is specially qualified for applications in micro electro mechanical systems. Specialized equipment and new photoresists have been developed or are under development to cope with the new challenges in the field of preparing extremely thick photoresist layers, to plan the process of patterning these thick resists, and to deal with the difficulties of the following galvanoplating step. A technology called three-dimensional ͑3D͒ UV-microforming was developed, consisting of a resist preparation process for very thick photoresists ͑positive or negative tone͒, UV lithographic steps, resist development, moulding procedures by galvanodeposition, and finally stripping and cleaning for finishing the structures. A minimum width of 3 m for the resist bars was found to be necessary to withstand the fabrication process of lines and spaces in 15 m thick resist. For thicker layers high aspect ratios of more than 10 as well as steep edges of more than 88°could be fabricated. The resist patterns were moulded by using electroplating. For microsystem applications metals and alloys can be deposited into the resist patterns. 3D UV-microforming, a combination of UV patterning of thick layer resists and galvanoplating, enables the low-cost fabrication of a wide variety of micro components for many different users.

LF55GN Photosensitive Flexopolymer: A New Material for Ultrathick and High-Aspect-Ratio MEMS Fabrication

“…While these resists are easier to strip than the SU-8, the attainable thickness is limited to only 100 µm in a single spin-coating step. Multiple spin coating has been used to form 1.5-mm-thick layers in the case of JSR THB-430N negative photoresist, but the obtained structures present an aspect ratio of 5 with very low resolution and poor sidewall quality [27]. All these limitations favor the use of SU-8 as the dominant photosensitive polymer for ultrathick microelectromechanical system (MEMS) fabrication today.…”

Dynamic Change in Color Filter Layers during the Baking Process by Multi‐Speckle Diffusing Wave Spectroscopy

“…Several studies on controlling the UV‐cured photoresist profile in the proximity photolithography process have been performed , . Chuang et al adjusted the wall profiles by effectively eliminating the UV light diffraction on the photoresist by using glycerol as an index‐matching material bridging the air‐gap between the photomask and photoresist.…”

“…The most common application for producing CF layers is based on the pigment method and employs a color photoresist. This technique comprises the following six stages [8,9]: (1) the formation of black matrix, (2) the coating of a color photoresist on a glass substrate surface, (3) the UV exposure through a photomask for insoluble layers, (4) the removal of unnecessary portions in a layer using a developing solution (e.g., a 1 wt % KOH aqueous solution) and the layer formation via a baking process, (5) Several studies on controlling the UV-cured photoresist profile in the proximity photolithography process have been performed [5][6][7]10]. Chuang et al [6] adjusted the wall profiles by effectively eliminating the UV light diffraction on the photoresist by using glycerol as an index-matching material bridging the air-gap between the photomask and photoresist.…”

Application of Laser Scan Lithography to Fabrication of Microcylindrical Parts

“…However, economical and inexpensive optical lithography is also starting to be investigated since superior resists with high transmittance for UV light have been developed. [1][2][3] In conventional applications, optical lithography has been applied to plane wafers and it has been difficult to print patterns on various curved surfaces. If novel patterning technology is developed for printing various patterns on curved surfaces, it will open new applications of micromachines.…”