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In 2009 Carl Zeiss stopped the manufacture of precision gratings. All users of precision gratings were very concerned about this decision, since they all need such gratings for their experiments. One of the institutes of the HZB, the Institute for Nanometer Optics and Technology (INT), has extensive experience in micro fabrication (technology group). In spring 2010, HZB decided to take over the old C. Zeiss grating fabrication and build up its own technology center for grating fabrication. Using governmental support, HZB has installed all necessary equipment and processes to fabricate high quality gratings for the synchrotron radiation community.

Soft UV NIL as replication technique was used to replicate sub 100 nm structures. The aim of this work is the stamp production and the replication of structures with dimensions smaller than 100 nm in a simple manner. Composite stamps composed of two layers, a thin hard PDMS h PDMS layer supported by a thick soft PDMS s PDMS layer are compared to common s PDMS stamps regarding the resolution by using a Siemens star star burst pattern as test structure. The master is fabricated by Electron Beam Lithography EBL in a 140 nm thick PMMA resist layer. The stamp is molded directly from the structured resist, without any additional anti sticking treatment. Therefore the resist thickness determines the aspect ratio, which is 1.5 at the resolution limit. The replication is done in a UV curing cycloaliphatic epoxy material. The employed test structure provides good comparability, the resolution limit at a glance, and it integrates a smooth transition from micro to nanostructures. Therefore it is a capable structure to characterize the UV NIL

In a close collaboration the team of Micromotion, micro resist technology, BESSY, and LSU-CAMD have successfully mastered the challenges of LIGA production of ultra-precision microparts for Micro Harmonic Drive® gears. The complementary expertise ranging from design and application know-how to process research and technical support resulted in high quality LIGA microparts and superior Micro Harmonic Drive® gears taking advantages of the free 2D design capability and material choice. It is also an excellent example that through contributions from partners with different background and expertise LIGA precision parts can be produced with high quality and yield and for a market competitive price.

First promising investigations of SU-8 removal experiments with a novel plasma etching technique are presented. The basic idea of this technique is to separate the highly effective generation of chemical radicals (e.g. oxygen radicals) using a traveling wave reactor (TWR) microwave source with water cooled plasma zone from the chemical reaction with the resist polymer. The etching tool operates in a remote and downstream mode with very high radical density allowing precise thermal management of the substrates on the chuck giving controlled process conditions without deviation in temperature, and generally preventing ion bombardment, at least resulting in gentle processing without jeopardizing the integrity of the metal structures. Very good removal of SU-8 with very few residues and very high etching rates up to 10 μm per minute are observed in first experiments which are offering chances to get even more than 20 μm per minute. The etching process is isotropic, and the rate stays stable during the whole removing process even for very thick films of 1 mm and more. First application examples of SU-8 removal are demonstrating the great potential of the presented microwave plasma based technique not only for the cleaning of metallic microparts but also for other more sensitive materials which is demonstrated by SU-8 removal from graphite X-ray mask substrates.

Here we describe the use of a backside exposure method for the creation of high aspect ratio tapered microstructures with nano-porous sidewalls. These sidewalls result from the exposure and curing conditions of the SU8 matrix. The structures show ultra-hydrophobic behavior with water contact angles of more than 160°, without an additional coating of the SU8 polymer. By choosing appropriate exposure conditions, needlelike structures can be created with a high level of porosity, covering their entire surface. The contact angle hysteresis values of such structures lie in the range of 20°. After an additional deposition of smooth and thin metallic gold film and coating it with an alkyl thiol selfassembled monolayer (SAM), we were able to decrease this hysteresis to values of around 10°. By using thin and rough metallic films like wet chemically oxidized titanium oxide and a fluoralkylsilane SAM, the hysteresis values could be reduced to only 4°.

Since the early 1990s a variety of applications ranging from precision metallic, ceramic, or polymeric parts to complex devices for micro-fluidic and micro-optic applications have been discussed with the assumption that LIGA can either make a significant contribution or is the sole technology able to make these products. The question today is, have individual LIGA groups or even the entire LIGA community achieved this goal? Despite major investments, a lot of hard work from many students and researchers, and some promising “prototypes”, a true mass product made by direct LIGA, i.e., using X-ray lithography and electroplating, has still not entered the market. This paper will briefly present the current status of direct-LIGA technology and discuss some examples of commercialization efforts as well as prospects for high-volume production.

A case study of use of negative type SU-8 X-ray sensitive resist for fabrication of advanced, highly precise, ultra tall direct LIGA mechanical microparts is presented in this paper. Using direct LIGA technique, ∼1 mm tall highly precise metallic gear wheels are being fabricated, previously using PMMA based process. Starting from a non-optimized non-satisfying SU-8 process, significant process parameters for process optimization were identified using statistical design of experiment. By varying the significant process parameters, SU-8 process was further optimized with respect to critical aspect of sidewall bow and tilt of metallic structures. After the optimization, metallic parts fabricated using SU-8 process showed comparable quality as those fabricated using PMMA based process.

A variety of different photo resists are used for fabrication of MEMS. Presently good results were reported for SU-8, a chemically amplified negative tone photoresist. But SU-8 has a disadvantage for some applications in LIGA technique, especially in the X-ray mask fabrication. After processing the finished resist pattern are hardly soluble from the substrate. This paper will briefly describe the current status of the development of the new negative tone photoresist CAR 44 whose big advantage is the easy removableness of the cross linked pattern.

High quality scatterometry standard samples have been developed to improve the tool matching between different scatterometry methods and tools as well as with high resolution microscopic methods such as scanning electron microscopy or atomic force microscopy and to support traceable and absolute scatterometric critical dimension metrology in lithographic nanomanufacturing. First samples based on one dimensional Si or on Si 3 N 4 grating targets have been manufactured and characterized for this purpose. The etched gratings have periods down to 50 nm and contain areas of reduced density to enable AFM measurements for comparison. Each sample contains additionally at least one large area scatterometry target suitable for grazing incidence small angle X ray scattering. We present the current design and the characterization of structure details and the grating quality based on AFM, optical, EUV and X Ray scatterometry as well as spectroscopic ellipsometry measurements. The final traceable calibration of these standards is currently performed by applying and combining different scatterometric as well as imaging calibration methods. We present first calibration results and discuss the final design and the aimed specifications of the standard samples to face the tough requirements for future technology nodes in lithography.

Scatterometry is a common technique for dimensional characterisation of nanostructures in the semiconductor industry. Currently this technique is limited to relative measurements for process development and process control. Although the high sensitivity of scatterometry is well known, it is not yet applied for absolute measurements of critical dimensions (CD) and quality control due to the lack of traceability. Thus we aim to establish scatterometry as traceable and absolute metrological method for dimensional measurements. Suitable high quality calibrated scatterometry reference standard samples are currently developed as one important step to enable traceable absolute measurements in industrial applications. The reference standard materials will base either on Si or on Si3N4. A traceable calibration of these standards will be provided by applying and combining different scatterometric as well as imaging calibration methods. First Silicon test samples have been manufactured and characterised for this purpose. The etched Si gratings have periods down to 50 nm and contain areas of reduced density to enable AFM measurements for comparison. We present the current design and first characterisations of structure details and the grating quality based on AFM measurements, optical, EUV and X-Ray scatterometry as well as spectroscopic ellipsometry. Finally we discuss possible final designs and the aimed specifications of the standard samples to face the tough requirements for future technology nodes in lithography.

Interest in thick-photoresist applications is steadily growing. In addition to bump fabrication and wire interconnect technology (WIT), the process of patterning thick-layer photoresists by UV lithography is specially qualified for applications in microelectromechanical systems (MEMS). 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, the process of patterning these thick resists, and to deal with the difficulties of the following galvanoplating step. As one of the most critical steps in thick-photoresist processing, the baking procedure was investigated. Positive tone photoresists (AZ 4562, ma-P 100) were processed by means of three different baking methods: air-forced oven, ramped hotplate, and IR radiation. It could be shown that IR baking is advantageous compared to the other methods with respect to process duration and energy consumption. As for edge steepness, resolution, edge loss, and surface roughness, all methods deliver nearly the same results. A minimum width of 2-3 µm for the resist bars was found to be necessary to withstand the fabrication process of lines and spaces in about 15 µm thick resists. For thicker layers, high aspect ratios of about 10 as well as steep edges of more than 88° could be fabricated. The development of SU-8, a chemically amplified negative tone photoresist for the 300-450 nm region opened totally new dimensions for the UV depth lithography. Even under development, SU-8 delivers results otherwise only achievable by x-ray lithography. The deposition of photoresist on highly-structured surfaces demands advanced methods. Electrodeposition of resist is one solution. PEPR 2400 was used for patterning by UV light in order to generate resist patterns around a free standing silicon bar. The achieved resist patterns were moulded by using electroplating. For microsystem applications some metals and alloys were deposited. Three-dimensional micro components were fabricated as demonstrators for the new technique. Electrodeposition allows the use of materials with interesting properties which could not be provided by standard processes in microelectronics.

Interest in thick photoresist applications is steadily growing. Specialised equipment has been developed to cope with the new challenges to process and pattern extremely thick photoresist layers. A decisive step in the preparation of resist layers is the prebaking. The impact of three different prebaking technologies on the resist performance has been investigated. Resist patterns obtained after oven, hotplate or IR prebaking exhibit equal high quality. Compared to oven and hotplate baking the process length and energy consumption is markedly reduced using IR radiation favouring this variant to be the optimum prebaking process for very thick photoresist layers.

SiN is a promising candidate for the fabrication of photonic crystals (PCs) with band gaps in the wavelength range between 550 nm and 850 nm. Here, we investigate the optical properties of cavities in SiN PC membranes by fluorescence spectroscopy of embedded emitters. For this purpose a dye solution is spin-cast on top of the PC membranes and the fluorescence is studied using a confocal microscopy setup. We observe strong emission resonances of molecules spatially and spectrally coupled to the cavity modes. These resonances are compared to finite-difference time-domain simulations of the PC structures, allowing an optimization of the cavity geometry to achieve high quality factors (several hundreds to nearly one thousand). Furthermore, we study routes to selectively incorporate single emitting particles into the cavities applying scanning probes. In this way we introduce SiN PC cavities as universal tools for the manipulation of the emission properties of a huge variety of different emitters in the visible.

The production of X-ray masks is one of the key techniques for X-ray lithography and the LIGA process. Different ways for the fabrication of X-ray masks has been established. Very sophisticated, difficult and expensive procedures are required to produce high precision and high quality X-ray masks. In order to minimize the cost of an X-ray mask, the mask blank must be inexpensive and readily available. The steps involved in the fabrication process must also be minimal. In the past, thin membranes made of titanium, silicon carbide, silicon nitride (2-5μm) or thick beryllium substrates (500μm) have been used as mask blanks. Thin titanium and silicon compounds have very high transparency for X-rays; therefore, these materials are predestined for use as mask membrane material. However, the handling and fabrication of thin membranes is very difficult, thus expensive. Beryllium is highly transparent to X-rays, but the processing and use of beryllium is risky due to potential toxicity. During the past few years graphite based X-ray masks have been in use at various research centers, but the sidewall quality of the generated resist patterns is in the range of 200-300 nm Ra. We used polished graphite to improve the sidewall roughness, but polished graphite causes other problems in the fabrication of X-ray masks. This paper describes the advantages associated with the use of polished graphite as mask blank as well as the fabrication process for this low cost X-ray mask. Alternative membrane materials will also be discussed.

Poly-methylmethacrylate (PMMA), a positive resist, is the most commonly used resist for deep X-ray lithography (DXRL)/LIGA technology. Although PMMA offers superior quality with respect to accuracy and sidewall roughness but it is also extremely insensitive. In this paper, we present our research results on SU-8 as negative resist for deep X-ray lithography. The results show that SU-8 is over two order of magnitude more sensitive to X-ray radiation than PMMA and the accuracy of the SU-8 microstructures fabricated by deep X-ray lithography is superior to UV-lithography and comparable to PMMA structures. The good pattern quality together with the high sensitivity offers rapid prototyping and direct LIGA capability. Moreover, the combinational use of UV and X-ray lithography as well as the use of positive and negative resists made it possible to fabricate complex multi-level 3D microstructures. The new process can be used to fabricate complex multi-level 3D structures for MEMS, MOEMS, Bio-MEMS or other micro-devices.

During the past few years, graphite based X-ray masks have been in use at CAMD and BESSY to build a variety of high aspect ratio microstructures and devices where low side wall surface roughness is not needed In order to obtain lower sidewall surface roughness while maintaining the ease of fabrication of the graphite based X-ray masks, the use of borosilicate glass was explored. A borosilicate glass manufactured by Schott Glas (Mainz, Germany) was selected due to its high purity and availability in ultra-thin sheets (30 μm). The fabrication process of the X-ray masks involves the mounting of a 30 μm glass sheet to either a stainless steel ring at room temperature or an invar ring at an elevated temperature followed by resist application, lithography, and gold electroplating. A stress free membrane is obtained by mounting the thin glass sheet to a stainless steel ring, while mounting on an invar ring at an elevated temperature produces a pre-stressed membrane ensuring that the membrane will remain taut during X-ray exposure. X-ray masks have been produced by using both thick negative- and positive-tone photoresists. The membrane mounting, resist application, lithography, and gold electroplating processes have been optimized to yield X-ray masks with absorber thicknesses ranging from 10 μm to 25 μm. Poly(methyl methacrylate) layers of 100 μm to 400 μm have been successfully patterned using the glass membrane masks.

In 2009 Carl Zeiss stopped the manufacture of precision gratings. All users of their gratings were very concerned about this decision, since they all need precision gratings for their experiments. One of the institutes of the HZB, the Institute for Nanometer Optics and Technology (INT), has extensive experience in micro fabrication (technology group). In spring 2010, HZB decided to take over the old C. Zeiss grating fabrication and build up its own technology center for grating fabrication. In March 2010, the INT applied to the Senate of Berlin for funding for our project from the European Regional Development Fund (ERDF). In October 2010, HZB received an approval of its application from the Senate of Berlin (contract No 20072013 2/43). Using this governmental support, HZB will install all necessary equipment and processes to fulfill these demands until end of 2013.

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 microelectro-mechanical-systems (MEMS). 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, the process of patterning these thick resists, and to deal with the difficulties of the following galvanoplating step. As one of the most critical steps in thick photoresists processing, the baking procedure was investigated. Two positive tone photoresists were processed by means of three different baking methods: air-forced oven, ramped hotplate, and IR radiation. Furthermore, combinations between the methods were tested. It could be shown that IR baking is advantageous compared to the other methods with respect to process duration and energy consumption. Compared to edge steepness, resolution, edge loss, and surface roughness, all methods deliver nearly same results. A minimum width of 2-3 micrometers for the resist bars was found to be necessary to withstand the fabrication process of lines and spaces in about 15 micrometers thick resist. For thicker layers high aspect ratios of more than 10 as well as steep edges of more than 88 degrees could be fabricated. The resist patterns can be molded by using electroplating.

A new technology called 3D UV-Microforming consisting of an advanced resist preparation process, UV lithographic steps, resist development, moulding procedures by electrodeposition, and finally stripping and cleaning for finishing the structures was developed for application in microsystem technology. It enables the low-cost fabrication of a wide variety of micro components for many different users. During resist preparation, layers up to two hundred pm thickness have been obtained until now. By using a standard UV mask aligner as an exposure tool followed by immersion development, thick resist layers up to 100 jim could be patterned in a single step on pre-processed silicon wafers. Repeated exposure and development were successfully used for structuring resist layers of up to 200 R thickness. 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 pulse or DC electroplating. For microsystem applications some metals and alloys were deposited. Three-dimensional micro components were fabricated as demonstrators for the new technique. It allows the use of materials with interesting properties which could not be provided by standard processes. Keywords: 3D UV-Microforming, electrochemical microfabrication, UV lithography, thick photoresist layers, high aspect ratio, steep edges, moulding by electrodeposition, sacrificial layers, 3D surface components, low-cost technology

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 (3D) UV‐microforming was developed, consisting of a resist preparation process for very thick photoresists (positive or negative tone), UV lithographic steps, resist development, moulding procedures by galvanodeposition, and finally stripping and cleaning for finishing the structures. A minimum width of 3 μm for the resist bars was found to be necessary to withstand the fabrication process of line...

Very thick photoresist layers were patterned by contact ultraviolet (UV) lithography. In a following microelectrodeposition step the generated resist patterns were molded and three-dimensional (3D) microstructures were fabricated directly onto system surfaces. The new technology, called 3D UV-microforming, consists of an advanced resist preparation process, an UV lithographic step, resist development, a molding procedure by electrodeposition, and finally stripping and cleaning for finishing the structures. It enables the low-cost fabrication of a wide variety of microcomponents for many different uses. During resist preparation, layers up to 200 mu m thickness were obtained. By using a standard UV mask aligner as an exposure tool followed by immersion development, thick resist layers up 100 mu m could be patterned in a single step on preprocessed silicon wafers. Repeated exposure and development were successfully used for structuring resist layers of up to 200 mu m thickness. Using AZ 4000 Series photoresist, the resolution is also limited by mechanical stability. For lines and spaces in 15- mu m-thick resist a minimum width of 3 mu m for the resist was found to be necessary to overcome the fabrication process. For thicker layers high aspect ratios of more than 10 as well as steep edges of more than 88 degrees could be fabricated. The resist patterns used were molded by pulse or by direct current electroplating. For microsystem applications some metals and alloys were deposited. Three-dimensional microcomponents were fabricated as samples for demonstrating the new technique. The technique allows the use of materials with interesting properties, ones that could not be provided by standard processes.