SU-8 is a negative tone proxy type resist which allows high aspect ratio for micro machining. SU-8 molds can be used for micro casting and embossing for making high aspect MEMS. A quick way to produce prototypes (Design -> Expose -> Prototype) is presently an important task in the micro fabrication. In this work we demonstrate the ability of multiple layer and binary structuring of SU-8 using maskless photolithography by the DWL66 device. As light source, we used a 30 mW He-Cd-Laser at 325 nm wavelength. The intensity is varied over 31 steps (grey levels) by an acousto-optical modulator (AOM) which provides the desired grey tone levels. By means of microlens arrays (MLA) we represent the achieved results by back side exposures. It can be shown that in addition to producing the curvature of the lenses by intensity modulation, the total height of lenses can be controlled by using supplementary attenuation. The total achieved height of micro lenses is approximately 65 μm resulting from a 100 μm thick SU-8 25 resist made by multiple coating method. Good chemical, mechanical and optical properties make SU-8 interesting for different applications as micro devices in micro-optics and micro-optoelectronics.
This paper shows that a direct write laser has completely incoherent properties, even though the light used for illumination is coherent. As a result of this fact it has twice the resolving power of that of a coherent imaging system. Due to the extended depth of focus steep resist walls can be achieved using a direct write system. To demonstrate this exposure on 1.5 micrometers and 2.0 micrometers thick photoresist were made. A multiple- exposure technique is proposed to produce structures consisting of 0.25 micrometers lines and spaces, although the smallest structure which can be exposed is 0.75 micrometers .
As the feature size requirements of TJLSI devices continue to decrease below the practical limits of standard optical
metrology, alternate measurement methodologies will be utilized on a more routine basis during device fabrication. A
series of linewidth measurements of photoresist on polysilicon and etched polysilicon equal line/space gratings having
nominal linewidths ranging from 0.45 jim to 2.0 p.m has been performed using a variety of metrology techniques.
Features fabricated using a 248 nm deep UV laser stepper and 405 nm near UV stepper were used in the experiments.
Top-down low-voltage SEM measurements, electrical resistance measurements, confocal ultraviolet laser scanning
microscope profiles, and SEM measurements on cleaved cross sections are compared. By measuring a large number of
points on each line and die, the variability of the linewidths themselves, the measurement precision of the techniques, and
the measurement bias between the methods are isolated. Experimental procedures and measurement techniques are
described along with the resultant data.
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