Search

Photomask issues can result in shifted pattern defects printed on the wafer. In the case of sub-1x nm nodes, these pattern defects of interest (DOI) can be difficult for conventional optical inspections to detect. In this paper we present a case study of a new mask qualification for a MOL gate open (GO) contact mask layer. The new mask was introduced to compensate for a known open between trench silicide (TS) contact and GO. During qualification, a shift in the GO overlay was seen on one section of the wafer and suspected to be the cause of a TS-gate short. A Design of Experiments (DOE) was created to investigate if the issue was solely mask related or if it could be mitigated during processing (litho/etch). Physical mode e-beam inspection was used to monitor the DOE wafers, however the resolution of the e-beam inspection tool was not sufficient to conclusively classify the defects observed. A high resolution, high landing energy SEM defect review was introduced post e-beam inspection to better monitor the splits running as part of the DOE.

We report the application of perylenetetracarboxylic diimide (PTCDI) nanowires for sensing ethyl acetate. The conductivity of the crystalline nano/microwires increases quickly and selectively in the presence of ethyl acetate vapor, but not with water, acid and alcohol vapors, suggesting that the nanowires of PTCDI may be used for monitoring ethyl acetate during a wine manufacturing process.

We have recently fabricated new nano/mesowires of perylene tetracarboxylic diimide (PTCDI) without side chains by self-assembling them from a gas phase. In this letter, we discuss a single PTCDI mesowire transistor that was successfully fabricated, characterized, and modeled. This organic n-channel field effect transistor shows good output and transfer characteristics. Our transistor model includes the Poole-Frenkel electric field dependence of charge carrier mobility in organic materials and fits all experimental output characteristics of the transistor. The zero-field charge carrier mobility of the PTCDI mesowire is found to be 0.72 cm2/(V·s). The experimental results are promising for the further development of single nanowire transistors and advancement of organic nanoelectronics.

Mask blank defectivity remains a challenge in Extreme Ultraviolet (EUV) lithography. One of the mitigation strategies has been to identify the source of particles causing defects in the mask blank deposition tools. Vacuum components like valves, valve seals, stages, filters, etc. could be a possible source of particles in the tools. Therefore, it is necessary to quantify the amount of particles generated by the vacuum components. This feedback to the supplier can be used to help make vacuum components that shed fewer particles. We show results from a valve and nanoparticle particle test system at the College of Nanoscale Science and Engineering (CNSE) in collaboration with SEMATECH. The setup consists of a condensation particle counter (CPC), which can detect particles between 10 nm – 3 um, and a scanning mobility particle sizer (SMPS), which can provide the size distribution of the particles between 10 nm – 280 nm. We show results from testing two different types of 300 mm valves and compare the particle counts per cycle detected by the CPC for both. Moreover, choosing the best operating parameters of the valve can reduce the number of defects generated. We will present the optimized operating parameters. Selection of appropriate valve seal materials for plasma environments can also be crucial for reducing their degradation.

During exposure in an EUV scanner, photoresist and other materials coated on a wafer are known to outgas various species. As a requirement to pattern materials in an ASML NXE scanner, these materials need to be screened for outgassing and possible optics contamination. As part of the testing process, a resist-coated wafer is exposed in a vacuum chamber mimicking the conditions inside an EUV scanner. The resist exposure source can be either EUV photons or electron beam (e-beam). This presentation will cover the results to date on a SEMATECH program to study resist outgassing from both the commercial system from EUV Tech and a custom Resist Outgassing and Exposure (ROX) tool. The EUV Tech results reported will be based on electron exposures of the photoresist, and the ROX results reported will be based on EUV photon exposures of the photoresist. The results reported will cover both tools and the measurements of over 80 commercial photoresists.

The development of resists that meet the requirements for resolution, line edge roughness and sensitivity remains one of the challenges for extreme ultraviolet (EUV) lithography. Two important processes that contribute to the lithographic performance of EUV resists involve the efficient decomposition of a photoacid generator (PAG) to yield a catalytic acid and the subsequent deprotection of the polymer in the resist film. We investigate these processes by monitoring the trends produced by specific masses outgassing from resists following EUV exposure and present our initial results. The resists tested are based on ESCAP polymer and either bis(4-tert-butylphenyl)iodonium perfluoro-1-butanesulfonate or bis(4-tert-butylphenyl)iodonium triflate. The components originating from the PAG were monitored at various EUV exposure doses while the deprotection of the polymer was monitored by baking the resist in vacuum and detecting the cleaved by-product from the polymer with an Extrel quadruple mass spectrometer.

Optics contamination remains one of the challenges in extreme ultraviolet (EUV) lithography. Dependence of contamination rates on key EUV parameters was investigated. EUV tools have optics at different illumination angles. It was observed that at shallower angles, the carbon contamination rate and surface roughness was higher on the optics surface. This is a concern in EUV optics as higher roughness would increase the scattering of the EUV radiation. Secondary ion time of flight mass spectrometer (TOF-SIMS) data indicated that the carbon contamination film might be a polymer. Three chemical species were used to investigate the dependence of polymerization and reactivity on the contamination rate. Acrylic acid was found to have a measurable contamination rate above background compared to propionic acid and methyl methacrylate. Secondary electron dissociation is one of the mechanisms considered to be a cause for the growth of the carbon contamination film. Multiple experiments with two substrates having different secondary electron yields were performed. The substrate with the higher secondary electron yield was found to give a higher contamination rate.

Optics contamination remains one of the challenges in extreme ultraviolet (EUV) lithography. In addition to the desired wavelength near 13.5 nm (EUV), plasma sources used in EUV exposure tools emit a wide range of out-of-band (OOB) wavelengths extending as far as the visible region. We present experimental results of contamination rates of EUV and OOB light using a Xe plasma source and filters. Employing heated carbon tape as a source of hydrocarbons, we have measured the wavelength dependence of carbon contamination on a Ru-capped mirror. These results are compared to contamination rates on TiO 2 and ZrO 2 capping layers.

We investigated the possibility of doping poly (sodium poly[2-(3-thienyl)-ethoxy-4-butylsulfonate) (PTEBS) with perylene tetracarboxylicdiimide (PTCDI) nanobelts through ultraviolet photoelectron spectroscopy (UPS) measurements. For our experiment, PTEBS was tuned to absorb maximum light in the range of 450 nm to 550 nm which corresponds to the maximum solar irradiance of the Earth’s atmosphere. Nanobelts of PTCDI were synthesized by gas phase self assembly process. Doping PTEBS with PTCDI nanobelts causes a shift in the Fermi level of the composite material with respect to the vacuum level as observed in the photoemission spectrum. With increased PTCDI doping, PTCDI does not act much like an electron donor, but more like an electron acceptor. The peaks corresponding to the sigma bonds shift towards the vacuum level with higher concentrations of the dopant. Using angled resolved photoemission spectra from a 3m toroidal grating monochromator, PTEBS displays change in the highest occupied molecular orbital in respect to its Fermi level when the side groups were substituted by H+ or OH- groups. The results confirm that the binding energy decreases with increase in activity of the dissolved hydrogen ions. It is evident that there is an increase in the density of states near the Fermi level and shifts to lower binding energies of the occupied molecular orbitals with pH level decrease, which is in agreement with the published optical absorption characteristics of PTEBS. Since UPS data confirm that PTCDI nanobelts dope PTEBS, along with its tunable absorption characteristics, this composite might be a promising material for optoelectronic application.