Rapid Prototyping of 2D Structures with Feature Sizes Larger than 8 μm (original) (raw)
Related papers
Rapid Prototyping of 2D Structures with Feature Sizes Larger than 8 �m
Anal Chem, 2003
This paper extends rapid prototyping for several types of lithography to the 8-25-µm size range, using transparency photomasks prepared by photoplotting. It discusses the technical improvement in photomask quality achieved by photoplotting, compared to the currently used image setting, and demonstrates differences in the resolution that can be obtained with photomasks with features in the 8-100-µm size range. These high-resolution photomasks were used to microfabricate microelectrodes, microlenses, and stamps for microcontact printing, following methods described previously.
Gray-scale photolithography using microfluidic photomasks
Proceedings of the National Academy of Sciences, 2003
The ability to produce three-dimensional (3D) microstructures is of increasing importance in the miniaturization of mechanical or fluidic devices, optical elements, self-assembling components, and tissue-engineering scaffolds, among others. Traditional photolithography, the most widely used process for microdevice fabrication, is ill-suited for 3D fabrication, because it is based on the illumination of a photosensitive layer through a ''photomask'' (a transparent plate that contains opaque, unalterable solid-state features), which inevitably results in features of uniform height. We have devised photomasks in which the light-absorbing features are made of fluids. Unlike in conventional photomasks, the opacity of the photomask features can be tailored to an arbitrary number of gray-scale levels, and their spatial pattern can be reconfigured in the time scale of seconds. Here we demonstrate the inexpensive fabrication of photoresist patterns that contain features of multiple and͞or smoothly varying heights. For a given microfluidic photomask, the developed photoresist pattern can be predicted as a function of the dye concentrations and photomask dimensions. For selected applications, microfluidic photomasks offer a low-cost alternative to present gray-scale photolithography approaches. P hotolithography is used to define critical feature size in the fabrication of the vast majority of microdevices including microelectronic circuits, microelectromechanical systems (MEMS), microfluidic devices, and nucleic acid͞protein microarrays (1). Essentially, photolithography consists of selectively illuminating a thin photosensitive layer (''photoresist'') with UV light through a mask containing opaque features (e.g., metal or ink emulsion) on a transparent background (e.g., glass or plastic). The photomasks impose two fundamental limitations on the features that can be produced. (i) The exposure is an all-or-none illumination process that results in photoresist features of uniform height; thus, the fabrication of threedimensional (3D) microstructures by traditional photolithography requires multiple exposure͞alignment steps. (ii) Photomask features are permanent, and thus design changes require the (costly and slow) fabrication of a new photomask, a major hurdle in research settings requiring fast-turnaround microdevice prototyping.
Analytical Chemistry, 2000
This paper describes a practical method for the fabrication of photomasks, masters, and stamps/molds used in soft lithography that minimizes the need for specialized equipment. In this method, CAD files are first printed onto paper using an office printer with resolution of 600 dots/ in. Photographic reduction of these printed patterns transfers the images onto 35-mm film or microfiche. These photographic films can be used, after development, as photomasks in 1:1 contact photolithography. With the resulting photoresist masters, it is straightforward to fabricate poly(dimethylsiloxane) (PDMS) stamps/molds for soft lithography. This process can generate microstructures as small as 15 µm; the overall time to go from CAD file to PDMS stamp is 4-24 h. Although access to equipmentsspin coater and ultraviolet exposure tools normally found in the clean room is still required, the cost of the photomask itself is small, and the time required to go from concept to device is short. A comparison between this method and all other methods that generate film-type photomasks has been performed using test patterns of lines, squares, and circles. Three microstructures have also been fabricated to demonstrate the utility of this method in practical applications.
Photolithography on bulk micromachined substrates
Journal of Micromechanics and Microengineering, 2009
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.
Soft lithography represents a non-photolithographic strategy based on selfassembly and replica molding for carrying out micro-and nanofabrication. It provides a convenient, effective, and low-cost method for the formation and manufacturing of micro-and nanostructures. In soft lithography, an elastomeric stamp with patterned relief structures on its surface is used to generate patterns and structures with feature sizes ranging from 30 nm to 100 µm. Five techniques have been demonstrated: microcontact printing (µCP), replica molding (REM), microtransfer molding (µTM), micromolding in capillaries (MIMIC), and solvent-assisted micromolding (SAMIM). In this chapter we discuss the procedures for these techniques and their applications in micro-and nanofabrication, surface chemistry, materials science, optics, MEMS, and microelectronics.
This paper reports a 3-D microstructure forming technique by inventing a new photomask making technique. This new mask is called Multi-Film Thickness mask (MFT mask). The paper also includes experiments by other two types of 3-D microstructure forming: (i) multi-dose lithography and (ii) Gray Scale Lithography mask (GSL mask). The MFT mask is proved to be economical for the lithography process of 3-D microstructure forming, which is typically applicable to the making of MicroElectro Mechanical Systems (MEMS). A limitation of the MFT mask is that only 3-D microstructures with vertical sidewall profiles can be made.
Maskless photolithography using UV LEDs
Lab on a Chip, 2008
A UV light emitting diode (LED) with a maximum output of 372 nm was collimated using a pinhole and a small plastic tube and focused using a microscope objective onto a substrate for direct lithographic patterning of the photoresist. Movement of the substrate with a motorised linear stage (syringe pump) allowed lines in SU-8 to be pattered with a width down to 35 lm at a linear velocity of 80 lm s −1 , while in the dry film resist Ordyl SY 330, features as narrow as 17 lm were made at a linear velocity of 245 lm s −1 . At this linear velocity, a 75 mm long feature could be patterned in 5 min. Functional microfluidic devices were made by casting PDMS on a master made by LED lithography. The results show that UV LEDs are a suitable light source for direct writing lithography, offering a budget friendly, and high resolution alternative for rapid prototyping of features smaller than 20 lm.
A Customizable and Low-Cost Ultraviolet Exposure System for Photolithography
Micromachines
For microfluidic device fabrication in the research, industry, and commercial areas, the curing and transfer of patterns on photoresist relies on ultraviolet (UV) light. Often, this step is performed by commercial mask aligner or UV lamp exposure systems; however, these machines are often expensive, large, and inaccessible. To find an alternative solution, we present an inexpensive, customizable, and lightweight UV exposure system that is user-friendly and readily available for a homemade cleanroom. We fabricated a portable UV exposure system that costs under $200. The wafer holder’s adjustable height enabled for the selection of the appropriate curing distance, demonstrating our system’s ability to be easily tailored for different applications. The high light uniformity across a 4” diameter wafer holder (light intensity error ~2.9%) was achieved by adding a light diffusing film to the apparatus. These values are comparable to the light uniformity across a 5” diameter wafer holder f...
Low-cost photolithography system for cell biology labs
Current Directions in Biomedical Engineering
Soft lithography, a tool widely applied in biology and life sciences with numerous applications, uses the soft molding of photolithography-generated master structures by polymers. The central part of a photolithography set-up is a mask-aligner mostly based on a high-pressure mercury lamp as an ultraviolet (UV) light source. This type of light source requires a high level of maintenance and shows a decreasing intensity over its lifetime, influencing the lithography outcome. In this paper, we present a low-cost, bench-top photolithography tool based on ninety-eight 375 nm light-emitting diodes (LEDs). With approx. 10 W, our presented lithography set-up requires only a fraction of the energy of a conventional lamp, the LEDs have a guaranteed lifetime of 1000 h, which becomes noticeable by at least 2.5 to 15 times more exposure cycles compared to a standard light source and with costs less than 850 C it is very affordable. Such a set-up is not only attractive to small academic and indus...