In this contribution, we present the results of a systematic material variation for the development of a resist material for high resolution positive tone electron beam lithography (EBL). Several acrylic copolymer materials with different compositions, that is varying mass fractions of the comonomers and different molecular weights, were synthesized and – as resist solutions – evaluated in terms of EBL performance at acceleration voltages of 30 kV and 100 kV. The resist material exhibiting the best combination of the desired properties, named mr-PosEBR, is two times more sensitive than PMMA 495k and performs comparably to the known high resolution resist ZEP520A at 30 kV. For example, a grating pattern with 29 nm wide lines with a period of 100 nm could be lithographically generated in films of mr-PosEBR with an area dose of 100 μC/cm2. In terms of resolution, single lines of only 35 nm width could be fabricated via metal liftoff. Furthermore, the dry etch stability of mr-PosEBR in a CF4/SF6 process is similar to the one of ZEP520A. Consequently, via dry etching nano patterns in mr-PosEBR could be smoothly transferred into the underlying Si substrate with high fidelity. Moreover, mr-PosEBR was evaluated as electron beam grayscale patterning and reflow resist. It was shown that the resist exhibits a good grayscale and reflow performance very similar to PMMA 120k and ZEP520A. Via these well controllable processes the generation of a wide variety of features and applications is possible.
Microlithography uses a variety of resists and polymer materials to create patterns and lithographic structures on several
types of substrates. Excellent adhesion of the resists and polymers to the substrate is a prerequisite for successful
patterning and pattern transfer. This paper presents the results of an investigation of the effects of an adhesion promoter,
SurPass, on the lithographic process when used in combination with a variety of resists, and substrate materials. SurPass
is a waterborne, non-hazardous, cationic organic surface active agent that promotes adhesion by modifying the substrate
surface energy without deposition, chemical change or impact on electrical properties of the substrate material. The
effectiveness of SurPass in combination with several novolac and epoxy resists on various substrate materials will be
presented.
Thick photoresists, e.g. up to 1 mm layer thickness, are widely used for the manufacture of high aspect ratio
microstructures, e.g. as mould for the fabrication of metallic micro parts. Such resists or materials exhibit high
mechanical and chemical stability to non-deformably withstand a pattern transfer process, e.g. by electroplating. After
the pattern transfer a solvent based removal is difficult or not possible in many cases. A selective mould removal –
without the damage of electroplated metal structures – is required for the fabrication of single micro parts. As second
application example UV curable and strongly crosslinkable inorganic-organic hybrid polymers such as OrmoComp ® and
OrmoStamp ® are used in UV moulding. The cleaning and rework of these moulds or also of stamps for nanoimprint
lithography (NIL) is a challenging task with increasing importance. The life time of an expensive master mould or stamp
as well as of the replicated working stamps is important, and therefore the ability to rework such stamps without any
defect or decreased resolution. Hence, we demonstrate the application of a plasma-assisted removal using the STP 2020
etching tool from MUEGGE [1] for remote dry etching of strongly crosslinked materials, i.e. the development of
processes for the isotropical etching of highly crosslinked photoresists and hybrid polymer materials will be presented. In
combination with this specific etching tool this technique shows a high potential to make plasma-assisted removal ready
for industrial production.
Photostructurable polymers, such as SU-8, have large potential impact on the field of MEMS/NEMS, allowing simple
fabrication of plastic MEMS/NEMS devices with nearly vertical sidewalls and high aspect ratios using standard
photolithographic procedures. Functional properties (as electrical conductivity or photoluminiscence) can be added to a
photostructurable polymer by doping the material with nanoparticles and/or nanocrystals. We present here the case in
which the resulting material presents opto-thermal properties if it is combined with an undoped polymer. From all the
different mechanisms for heating the structure, opto-thermal actuation is interesting from the point of view that it is
possible to obtain a mechanical energy transduction without requiring physical contact or proximity interaction, i.e.
devices can be moved merely by focusing light on it.
LIGA is a well-established process to fabricate metallic micro parts with high resolution, high precision and very low sidewall
roughness by means of X-ray lithography and electroplating. Typical mask substrate materials, e.g. beryllium, carbon based foils,
Si3N4 or SiC show different disadvantages such as low X-ray transparency or high toxicity or high prices or low conductivity or high
thermal expansion or surface porosity causing X-ray scattering. Due to the amorphous structure of vitreous carbon this mask material
proved to significantly reduce the amount of side wall striations, leading to extremely smooth pattern sidewalls. For the fabrication of
X-ray masks, PMMA with its unique features such as high aspect ratio patterns with high precision, exhibits low sensitivity and the
layers preparation is not easy. SU-8, an epoxy-based UV and X-ray sensitive, chemically amplified negative tone photoresist exhibits
high aspect ratio patterns with vertical sidewalls. The difficult remove of the resist after the electroplating process significantly
hinders the inspection of the fabricated X-ray mask. We present the suitability of an UV sensitive, chemically amplified, aqueous-alkaline
developable, and easy removable positive tone photoresist, XP mr-P 15 AV for the fabrication of X-ray masks by means of
UV lithography on vitreous carbon substrates.
There is an increasing need for highly viscous and easy to process thick and ultra thick photoresists for the production of Micro-Electro-Mechanical-Systems (MEMS) and advanced packaging. Here we present results with some novel positive tone photoresists formulated for this purpose. For that we transfered the concept of chemically amplified resists (CARs), originally designed to meet the IC-industry demands for miniaturization and higher resolution, to highly viscous resists. Various polymeric materials have been tested regarding their use in thick CARs. Appropriate resist formulations were developed and their lithographic performance was investigated in a thickness range of 50-150 microns. The CARs are sensitive to UV400.
Proc. SPIE. 3676, Emerging Lithographic Technologies III
KEYWORDS: Lithography, Electron beam lithography, Electron beams, Deep ultraviolet, Etching, Ultraviolet radiation, Photoresist materials, Absorbance, Photoresist processing, Picture Archiving and Communication System
Results of electron beam exposure of a DUV sensitive negative tone photoresists composed of a novolak/aromatic bisazide system are presented. Contents of the components of the resist solution were varied to cover a wide range of film thicknesses and to attain optimal performance of the resist. Dense patterns with dimensions of 100 nm and below of the resists patterned by electron beam exposure demonstrate its excellent resolution capability and the possibility to generate patterns with steep side walls and high aspect ratios.
A series of AZ-compatible negative photoresists composed of a novolak resin and azide sensitizers for the micro and nano-lithography is presented. The ma-N 2400 and ma-N 300 are sensitive to light of the deep UV region (248 nm, 254 nm, 308 nm), the ma-N 400 and ma-N 1400 are sensitive to light of the mid UV region, the latter has a high sensitivity to the i-line (365 nm). The thickness of the resist layers prepared by spin coating is up to 8 micrometers depending on the composition of the resist solution. All resists are non-swelling during aqueous alkaline development after exposure. Using special lithography, these photoresists have a resolution capability up to 0.1 micrometers . The resistance to wet etch solutions and to dry etch gases is superior and higher than that of the most positive resists based on novolak.
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