Klaus Elian

New stochastic post-exposure bake simulation method

A new method for simulating the post-exposure bake (PEB) of optical lithography is presented and applied to modeling the reaction-diffusion processes in a chemically amplified resist (CAR). The new approach is based on a mesoscopic description of the photoresist, taking into account the discrete nature of resist molecules and inhibitor groups that are attached to the resist polymers, but neglecting molecular details on an atomistic (microscopic) level. As a result, the time- and space-dependent statistical fluctuations of resist particle numbers, the correlations among them, and their effect on the printing result can be accounted for. The less molecules that are present in the volume of interest, the more important these fluctuations and correlations will become. This is the case for more and more shrinking critical dimensions (CD) of the lithographic structures but unchanged molecular sizes of the relevant resist species. In particular, the new PEB simulation method allows us to predict the behavior of statistical defects of the printed lithographic structures, which may strongly contribute to printing features like line edge roughness (LER).

Integration of polymer bonded magnets into magnetic sensors

This paper introduces a novel assembly and manufacturing technology for integrating permanent magnets into magnet sensor modules by use of plastic bonded magnets. High precision speed sensors in automotive applications, e.g. in anti-blocking-system or engine management, are based on a magnetic measurement principle [1]. Typical sensor modules contain a semiconductor based sensor chip and a permanent magnet providing the necessary bias field (see Fig. 1). This field is modulated by a passing external gear wheel out of material with high magnetic permeability, which is part of the magnetic circuit. The wheel speed can directly be determined by measuring the frequency of the magnetic field modulation. Permanent magnets are often assembled in a sequential pick and place process. We report a novel assembly technology by direct molding of thermoplast bonded magnets onto a chip carrier containing pre-assembled sensors. We will show, that this offers the following advantages: - Highest accuracy - Optimum working point, in particular for GMR sensors - High throughput by efficient parallel process - Simplification of the module assembly.

Negative-tone resist for phase-shifting mask technology: a progress report

With the objective to make smaller device structures at a given illumination wavelength the semiconductor industry is more and more trying to implement Phase-Shifting Masks (PSMs) as resolution enhancement technique for DUV lithography. However, with positive photoresists there is a phase edge problem. Using negative resists is the easiest approach to solve the phase edge problem. This is one of the reasons why negative resists are becoming more and more attractive for leading edge lithography. Therefore, we are developing a novel negative resist with 248/193 nm crossover capability. Most experiments were done in imitation of the CARLR bilayer resist process. The goal was to use established resist techniques and polymer materials, and just to change the generators and additives to get tone reversal. Using a photoacid generator (PAG) as additive leads to positive tone. In contrary with a photobase generator (PBG) and thermoacid generator (TAG) combination in a negative tone behavior is observed. Comprehensively, this blending concept allows the use of similar working polymers in both, positive and negative resists. The generator efficiencies were studied as well as the diffusion behavior of resist components during resist processing. Especially, process factors like baking conditions were investigated with the objective to control diffusion and limit resist outgassing in a high activation energy resist platform. Furthermore, in adaptation of the CARLR process, a separate liquid silylation step was integrated and investigated for various process conditions. In our paper we will discuss the characteristics and the lithographic capabilities of the novel methacrylate based negative resists. First promising results are based on DUV (248/193 nm) and ebeam exposures. Recent results with our positive version indicate the same outstanding possibilities. We expect a similar performance for the negative pendant in the near future.

Integrierte Zell-Sensorik in Lithium-Ionen-Akkus für Elektro- und Hybridfahrzeuge

Die Zustandsuberwachung von Traktionsbatterien beschrankt sich aktuell auf Strom, Spannung und eine Oberflachentemperatur. Durch den Einsatz von zellinterner Sensorik konnen Ziele wie Sicherheit, Leistung und Lebensdauer adressiert werden. Hierzu werden Anwendungsszenarien fur verschiedene Sensoren und Messgrosen dargestellt und die Anforderungen ausgearbeitet. Am Beispiel der Messgrosen Druck und Temperatur werden erste Messungen diskutiert, Potentiale aufgezeigt und die Herausforderungen fur eine Ubertragung in die Serie anschaulich dargestellt.

Resist technologies for ion projection lithography (IPL) stencil maskmaking

Corresponding to characteristics and manufacturing processes of IPL stencil masks, requirements of used resist technologies are determined. Two thin layer imaging (TLI) techniques, the single layer top surface imaging (TSI) and the bilayer CARL (chemical amplification of resist line) have been investigated and compared for stencil mask making. Especially the process design of CARL is discussed in detail. Additionally, a possible process integration of the carbon layer, that is deposited on the stencil mask and protects the membrane against damaging due to ion bombardment, is presented. Finally, results of silicon etching and complete manufactured stencil masks using the developed resist technologies are demonstrated.

Optimization of the e-beam sensitive bilayer CARL process for stencil mask making

Hardmask-less stencil mask making requires masks with a high aspect ratio. The bilayer CARL (chemical amplification of resist lines) process was evaluated and optimized with respect of generating irregular resist features below 180 nm in a film thickness of 750 nm. Especially the dry development was detailed investigated using statistical design and analysis of experiment. Processed CARL resist masks are compared with Top Surface Imaging results. Finally, results of a deep silicon etching process using the CARL resist masks are presented.

Correlation analysis : A fast and reliable method for a better understanding of simulation models in optical lithography

Nowadays, the advanced usage of simulation tools for optical lithography requires substantial knowledge about the impact of model parameters and process conditions on simulation results. In many cases up to 30 or 40 parameters have to be tuned for different experimental data in order to obtain reliable simulation results. Consequently, the investigation of the impact of all model and process parameters on simulation results can be very time consuming. Therefore, we applied a correlation analysis, a well known statistical method, that allows a sensitivity analysis of simulation parameters. We compared the results of the sensitivity analysis method with the outcome of a standard “one-factor-at-a-time-method” and discuss the advantages and disadvantages of both methodologies. A calibrated ArF photoresist model has been examined with both sensitivity analysis methods.

Methodology and practical application of an ArF resist model calibration

This paper focuses on a novel methodology for a fast and efficient resist model calibration. One of the most crucial parts when calibrating a resist model is the fitting of experimental data where up to 20 resist model parameters are varied. Although general optimization approaches such as simplex algorithms or genetic algorithms have proven suitable for many applications, they do not exploit specific properties of resist models. Therefore, we have developed a new strategy based on Design of Experiment methods which makes use of these specific characteristics. This algorithm will be outlined and then be demonstrated by applying it to the calibration of a Solid-C resist model for one ArF line/space resist. As characterizing dataset we chose: a) a Focus Exposure Matrix (FEM) for the dense array, b) linearity, c) OPE (optical proximity) curve and e) the MEEF (mask error enhancement factor) for a dense array. It turned out that a simultaneous fit of the complete data set was not possible by varying resist parameters only. Considering the optical parameters appeared to be crucial as well. Therefore the influence of the optical settings (illumination, projection, 3D mask effects) on the lithography process will be discussed at this point. Finally we obtained an excellent matching of model predictions and experimental results.