Peter Dress

Physical analysis of teflon coated capillary waveguides

Abstract A theoretical analysis of the properties of a liquid core waveguide (LCW) formed by a water filled, teflon AF2400 inner coated glass tube is presented. The theoretical analysis is based on numerical FD-BPM simulations and reflectivity calculations of the layer system in the LCW. The improvements due to this inner coating compared to other capillary cells are shown. A teflon AF2400 layer thickness of about 5 μm is sufficient to confine the optical intensity to the liquid core and thus avoid any absorption or scattering by the capillary material or any influence of the outside environment.

Liquid core waveguide with fiber optic coupling for remote pollution monitoring in the deep ultraviolet

A new combination of silica fibres, highly transparent in the ultraviolet (UV) and showing long term stability, combined with a teflon-coated liquid-core waveguide (LCW) is presented for remote sensing in the deep UV, for monitoring one of the major pollutants, nitrates, in water, but with potentially wider applicability. The arrangement exhibits low spectral loss in the range between wavelengths of 200 nm and 400 nm and can be used for analytical investigations to determine small concentrations of such impurities in water. The operation of the optical system to achieve guidance of UV light below a wavelength of 250 nm for fibre optic sensors is discussed. With an optical pathlength of 203 mm, nitrate concentrations as low as 22 μg/l could be detected.

Water-core waveguide for pollution measurements in the deep ultraviolet

A fiber optic system for water analysis with high transparency in the deep-UV region (lambda >/= 190 nm) is presented. The system consists of special UV-improved silica fibers and a liquid-core waveguide (LCW) as an optical cell. The apertures of both light guides, the silica fiber and the LCW, are matched. The optical losses of the device are investigated experimentally and compared with theory, especially with a standard free-space geometry. The performance of the system with respect to UV absorption spectroscopy is demonstrated for nitrate and chlorine pollution in pure water. For a 203-mm-long LCW the detection limits have been determined to be as low as 22 mug/L for nitrate and 26 mug/L for chlorine.

Optical fiber with a liquid H2O core

A novel concept of a liquid core lightguide in cylindrical geometry is presented. The coating of a hollow core glass tube with Teflon AFR leads together with a liquid filled core to such a guide. Effective coupling was obtained and low losses were observed. Using this liquid core guide as an optical cell in a spectrometer a significant increase in sensitivity, depending on the length of the guide, may be obtained.

Study on surface integrity in photomask resist strip and final cleaning processes

In recent years, photomask resist strip and cleaning technology development was substantially driven by the industrys need to prevent surface haze formation through the elimination of sulfuric acid from these processes. As a result, ozone water was introduced to the resist strip and cleaning processes as a promising alternative to a Sulfuric - Peroxide Mixture (SPM). However, with the introduction of 193i double patterning, EUVL (Extreme Ultraviolet Lithography) and NanoImprint Lithography (NIL) the demand on CD-linewidth control and surface layer integrity is significantly expanded and the use of ozone water is questionable. Ozone water has been found to cause significant damage to metal based mask surface layers, leading to significant changes in optical properties and CD-linewidth shift. In this paper HamaTech APE demonstrates the use of an alternative acid-free resist strip and cleaning process, which not only overcomes the named drawbacks of conventional ozone water use, but reduces resist strip time by 50% to 75%. The surface materials investigated during this study are; chrome absorber layers on binary masks, MoSi based shifters, chrome hard mask layers on EPSM, and ruthenium capping layers on EUV masks. Surface material integrity and CD-stability results using this new, acid-free approach are presented in the following pages.

Automated imprint mask cleaning for step-and-flash imprint lithography

Step-and-Flash Imprint Lithography (S-FIL) is a promising lithography strategy for semiconductor manufacturing at device nodes below 32nm. The S-FIL 1:1 pattern transfer technology utilizes a field-by-field ink jet dispense of a low viscosity liquid resist to fill the relief pattern of the device layer etched into the glass mask. Compared to other sub 40nm CD lithography methods, the resulting high resolution, high throughput through clustering, 3D patterning capability, low process complexity, and low cost of ownership (CoO) of S-FIL makes it a widely accepted technology for patterned media as well as a promising mainstream option for future CMOS applications. Preservation of mask cleanliness is essential to avoid risk of repeated printing of defects. The development of mask cleaning processes capable of removing particles adhered to the mask surface without damaging the mask is critical to meet high volume manufacturing requirements. In this paper we have presented various methods of residual (cross-linked) resist removal and final imprint mask cleaning demonstrated on the HamaTech MaskTrack automated mask cleaning system. Conventional and non-conventional (acid free) methods of particle removal have been compared and the effect of mask cleaning on pattern damage and CD integrity is also studied.

Megasonic cleaning: possible solutions for 22nm node and beyond

Megasonic energy transfer to the photomask surface is indirectly controlled by process parameters that provide an effective handle to physical force distribution on the photomask surface. A better understanding of the influence of these parameters on the physical force distribution and their effect on pattern damage of fragile mask features can help optimize megasonic energy transfer as well as assist in extending this cleaning technology beyond the 22nm node. In this paper we have specifically studied the effect of higher megasonic frequencies (3 & 4MHz) and media gasification on pattern damage; the effect of cleaning chemistry, media volume flow rate, process time, and nozzle distance to the mask surface during the dispense is also discussed. Megasonic energy characterization is performed by measuring the acoustic energy as well as cavitation created by megasonic energy through sonoluminescence measurements.

Effective EUVL mask cleaning technology solutions for mask manufacturing and in-fab mask maintenance

Extreme Ultraviolet Lithography (EUVL) is considered the leading lithography technology choice for semiconductor devices at 16nm HP node and beyond. However, before EUV Lithography can enter into High Volume Manufacturing (HVM) of advanced semiconductor devices, the ability to guarantee mask integrity at point-of-exposure must be established. Highly efficient, damage free mask cleaning plays a critical role during the mask manufacturing cycle and throughout the life of the mask, where the absence of a pellicle to protect the EUV mask increases the risk of contamination during storage, handling and use. In this paper, we will present effective EUVL mask cleaning technology solutions for mask manufacturing and in-fab mask maintenance, which employs an intelligent, holistic approach to maximize Mean Time Between Cleans (MBTC) and extend the useful life span of the reticle. The data presented will demonstrate the protection of the capping and absorber layers, preservation of pattern integrity as well as optical and mechanical properties to avoid unpredictable CD-linewidth and overlay shifts. Experiments were performed on EUV blanks and pattern masks using various process conditions. Conditions showing high particle removal efficiency (PRE) and minimum surface layer impact were then selected for durability studies. Surface layer impact was evaluated over multiple cleaning cycles by means of UV reflectivity metrology XPS analysis and wafer prints. Experimental results were compared to computational models. Mask life time predictions where made using the same computational models. The paper will provide a generic overview of the cleaning sequence which yielded best results, but will also provide recommendations for an efficient in-fab mask maintenance scheme, addressing handling, storage, cleaning and inspection.

90-nm mask making processes using the positive tone chemically amplified resist FEP171

A mask patterning technology for the 90nm technology node has been developed using the FujifilmARCH resist FEP171 and the state-of-the-art mask making tools SteagHamaTech mask coater ASR5000, Leica 50kV variable shaped e-beam writer SB350, SteagHamaTech developer ASR5000 and UNAXIS Mask Etcher III. A resist resolution of below 100nm dense lines and 150nm contact holes was demonstrated. The line width shrinking due to chrome etching varies between 25nm and 50nm per feature and a corresponding resolution of 125nm dense lines in a 105nm thick chrome absorber has been achieved. The global CD-uniformity with a 3σ of 7.7nm and a total range of 10.8nm met the requirements of the ITRS roadmap. The local uniformity with a 3σ of 3.8nm and a range of 5.6nm offers potential for future application of the Leica SB350. Applying of a new correction method taking electron scattering and process characeristics into account provides a linearity of 6.1nm. In addition, the line width of different featurees was kept in a range up to 12nm when the local pattern density was changed. The composite placement accuracy of 12nm fulfills already the requirements of the 65nm node. A special investigation proved the excellent fogging depression of the SB350.

Improved baking of photomasks by a dynamically zone-controlled process approach

A new type of bake system for photomasks, APB5000, has been developed, using a dynamic and multiple zone approach, to enable more precise Post Exposure Bake (PEB) and Post Coat Bake (PCB) of conventional and chemically amplified resists (CAR). The principal equipment concept and the optimization strategies are presented. The baking performance of the APB5000 is demonstrated for several surface temperatures between 90 degree(s)C and 150 degree(s)C. The temperature uniformity ranges achieved at the resist plane are better than 0.25 degree(s)C after stabilization at the final temperature and better than 1.5 degree(s)C during the ramping period. The repeatability of the bake temperature is better than +/- 0.07 degree(s)C for the setpoint temperature.