Stau-catalyzed 6^6Li Production in Big-Bang Nucleosynthesis

If the gravitino mass is in the region from a few GeV to a few 10's GeV, the scalar lepton X such as stau is most likely the next lightest supersymmetry particle. The negatively charged and long-lived X^- may form a Coulomb bound state (A X) with a nucleus A and may affect the big-bang nucleosynthesis through catalyzed fusion process. We calculate a production cross section of Li6 from the catalyzed fusion (He4 X^-) + d \to Li6 + X^- by solving the Schr\"{o}dinger equation exactly for three-body system of He4, d, and X. We utilize the state-of-the-art coupled-channel method, which is known to be very accurate to describe other three-body systems in nuclear and atomic reactions. The importance of the use of appropriate nuclear potential and the exact treatment of the quantum tunneling in the fusion process are emphasized. We find that the astrophysical S-factor at the Gamow peak corresponding to T=10 keV is 0.038 MeV barn. This leads to the Li6 abundance from the catalyzed process as Li6|_{CBBN}\simeq 4.3\times 10^{-11} (D/2.8\times 10^{-5}) ([n_{X^-}/s]/10^{-16}) in the limit of long lifetime of X. Particle physics implication of this result is also discussed.Comment: 16 pages, 7 figure

Charge Form Factor and Cluster Structure of 6^6Li Nucleus

The charge form factor of ${}^6$Li nucleus is considered on the basis of its cluster structure. The charge density of ${}^6$Li is presented as a superposition of two terms. One of them is a folded density and the second one is a sum of ${}^4$He and the deuteron densities. Using the available experimental data for ${}^4$He and deuteron charge form factors, a good agreement of the calculations within the suggested scheme is obtained with the experimental data for the charge form factor of ${}^6$Li, including those in the region of large transferred momenta.Comment: 12 pages 5 figure

Geometrically induced dose correction method for e-beam lithography applications

The e-beam lithography is faced with increasing challenges to achieve a satisfying patterning of structures with critical dimensions of about 32 nm or below. The reason for this issue is the unavoidable blurring of the deposited e-beam energy due to beam blur, electron scattering (forward and backward), and resist effects. The distribution of the finally deposited dose differs from the dose weighted geometry of the printed layout. In general, the finally deposited dose is described as convolution of the layout with a process specific proximity function being a model for the unavoidable blurring. This process proximity function (PPF) is often approximated by a superposition of two or more Gaussian functions. Thus, the electron forward scattering and resist effects, being most critical to the pattern fidelity, are often described altogether by the so called alpha-parameter of the PPF. Due to these physical reasons, when the desired critical dimension of a structure is nea r or below the alpha-parameter of the PPF, it may be just impossible to print the structure because of the vanishing image contrast due to the blurring. It was shown by means of the simulation feature of the ePLACE data prep package that in this situation a modification of both the geometry and the dose assignment of the shapes will significantly increase the contrast of the deposited energy and thus, even preserve the printability of critical structures. This geometrically induced dose correction (GIDC) method is implemented in the ePLACE package. The simulation results for test structures are now validated by exposures of test patterns and its results clearly establish the practical advantage of the new method. In this paper we will publish the results of the related exposures - done on Vistec SB3050 series shaped e-beam writers - demonstrating the practical importance of the GIDC method for layouts with critical dimensions of 32 nm and below

Pointwise process proximity function calibration - PPFexplorer application results

The semiconductor industry and mask shops spend great efforts in order to keep pace with the requirements on pattern fidelity of the ITRS lithography roadmap. Even for e-beam lithography - often referred to as technology with "unlimited" resolution - the challenges increase with shrinking feature sizes in combination with applicable resist processes. The pattern fidelity, specifically CD control, is crucial for the application of e-beam lithography. One aspect in CD control is the intrinsic proximity effect of the electron beam. This together with other contributions like influences from resist process or beam generation which are summarized altogether under the term process proximity effect have to be corrected. An accurate e-beam process proximity effect correction is therefore a key component of e-beam lithography. Some process proximity effect correction algorithms provide not only accurate correction for the process proximity effect induced pattern deformation but also optimize pattern contrast by adjusting geometry and dose simultaneously. However, the quality of the process proximity effect correction is limited by the calibration accuracy of the used model, i.e., the accuracy of the utilized process proximity function (PPF). In a previous paper [R. Galler et al, "PPF - Explorer: Pointwise Proximity Function calibration using a new radialsymmetric calibration structure", BACUS 2011] the PPF-explorer - a new experimental method for pointwise process proximity function calibration - was introduced and some first promising calibration results were shown. This paper presents the progress of the PPFexplorer proximity function calibration. This progress, among others, comprises automatic generation of calibration patterns, including pre-correction with respect to a rough forecast of the process proximity function to be calibrated. This pre-correction approach significantly reduces the number of necessary calibration structures and the number of measurement sites, without sacrificing calibration accuracy. On the contrary, the pre-correction has positive impact on the calibration quality, since it allows unifying the pattern contrast at the measurement sites, which reduces the SEM measurement induced error. We present the results of a PPFexplorer calibration with special focus on minimizing the number of measurement sites. The results show that the PPFexplorer method can help to improve the proximity effect model calibration with controllable efforts

A solution to meet new challenges on EBDW data prep

As chip design becomes more and more complex and alternative lithography technologies like EBDW get broader usage, the challenges increase with respect to all parts of the entire process. For exposure data preparation, we want to introduce a novel solution that offers new approaches to a user-friendly GUI, to exposure simulation, project definition and control, combined with proven kernels for data post-processing, fracturing and Proximity Effect Correction. This new solution has been implemented to run in an efficient 64 bit parallel computing environment and is called ePlace (eBeam Direct Write and Mask Data Preparation Layout Console). ePlace has the ability to process layout data of (in principle) unlimited size, given in various formats (GDSII, OASIS, DXF, CIF and others) and distributed over multiple files and hierarchies. Data post-processing capabilities include common Boolean functions (AND, OR, XOR, and Negation) as well as sizing, scaling, translation, rotati on and overlap removal. Processed data can be fractured and formatted for ebeam writers (e.g. Vistec Shaped Beam (SB) tools). For Proximity Effect Correction both dose variations and newly developed geometry correction (EPC) algorithms are available and a simulation engine provides fast and precise results for exposure pattern predictions. In addition to the standard shape exposure, ePlace supports the latest Cell Projection (CP) feature of current Vistec's SB series as well as the upcoming Vistec Multi-Beam-Tool