Dr. Reinhard R. Galler Profile

Dr. Reinhard R. Galler

Managing Director at EQUIcon Software GmbH Jena

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Publications (10)

PROCEEDINGS ARTICLE | September 9, 2013

E-beam GIDC resolution enhancement technology in practical applications

Proc. SPIE. 8880, Photomask Technology 2013

KEYWORDS: Point spread functions, Etching, Silicon, Resistance, Photomasks, Line width roughness, Cadmium sulfide, Semiconducting wafers, Resolution enhancement technologies, Chemically amplified resists

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For nearly all relevant applications of e-beam lithography the resolution and pattern quality requirements are approaching or exceeding the limits of the available process. On one hand, for shrinking feature dimensions, the e-beam proximity effect and process effects such as photo acid diffusion limit the pattern contrast and process window. On the other hand, e-beam process related parasitic effects such as shot noise, fogging, developer loading, heating, charging, and inhomogeneous bake introduce some significant errors. Even though e-beam tool and process tool suppliers continue to implement new or improve current strategies to avoid or correct these effects, the amount of residual errors requires some reasonable e-beam process window, in particular for high end applications. For some patterns the undersize-overdose approach (SIZE) improves the pattern fidelity and process window. However, for patterns with high fill factors this approach increases the overall deposited electron dose, which due to the increased backscattering diminishes or even eliminates the advantages. The geometrically induced dose correction (GIDC) method overcomes this issue by combining the SIZE concept with a short range framing technique, which reduces the deposited dose in large filled pattern areas. This paper provides a comparison of the standard, SIZE, and GIDC correction approaches for 1D test patterns as well as production patterns. For a broad comparison, patterns were printed onto negative and positive chemically amplified resists and on wafer and mask substrates using a Vistec SB352HR variable shape e-beam writer. Both wafers were also etched. The outcome of the study is that the SIZE and GIDC approaches often outperform the standard proximity effect correction. For dense patterns, GIDC still provides a better pattern quality and process window, while the SIZE approach suffers from the increased overall deposited electron dose and clearly falls behind GIDC in terms of process window. Further it was shown that the lowering of the dose in inner areas due to GIDC does not impact the etch resistance.

PROCEEDINGS ARTICLE | April 17, 2012

Pointwise process proximity function calibration: PPFexplorer application results

Proc. SPIE. 8352, 28th European Mask and Lithography Conference

KEYWORDS: Target detection, Electron beam lithography, Electron beams, Cadmium, Sensors, Calibration, Scanning electron microscopy, Photomasks, Critical dimension metrology, Photoresist processing

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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.

PROCEEDINGS ARTICLE | October 14, 2011

PPF-Explorer: pointwise proximity function calibration using a new radial symmetric calibration structure

Proc. SPIE. 8166, Photomask Technology 2011

KEYWORDS: Semiconductors, Lithography, Electron beam lithography, Point spread functions, Scattering, Calibration, Monte Carlo methods, Cadmium sulfide, Critical dimension metrology, Photoresist processing

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Lithographic patterning encounters growing challenges to meet the requirements of current and future semiconductor technology nodes. Even e-beam lithography is challenged due to the physical characteristic of the whole transfer process including the e-beam blur, electron scattering, and resist effects. These effects cause an unavoidable blurring of the exposed shapes and are often described as process proximity effect. Besides the correction of this process proximity effect pattern contrast and process window for the lithography step have to be regarded. There are promising approaches for contrast enhancing proximity effect correction concepts. To enable a stable patterning great efforts have to be put into decreasing the errors of all involved technologies. The blurring resulting from the transfer process is usually described by a so-called process proximity function (PPF) and mostly approximated by a superposition of two or more Gaussian functions. All algorithms for proximity effect correction use that PPF to perform their correction. Thus, an accurate determination of that PPF contributes to reducing the error budget of the proximity effect correction scheme. Several methods for PPF calibration were introduced in the past. Some are based on modelling the transfer process and performing Monte Carlo simulations. Another common approach is to design and expose calibration patterns, measure the resulting CDs, and obtain the process proximity function as the result of a simulation based parameter fitting to a model function such as a sum of Gaussian functions. In order to respect the increased accuracy requirements an even more accurate description of the PPF is expected. This paper describes the newly developed PPF-explorer method for the calibration of a pointwise proximity function as a complementary technique, which is based on the exposure and evaluation of new calibration layouts. Following the common assumption that a process proximity function is radial-symmetric, we developed radial-symmetric calibration layouts.

SPIE Journal Paper | October 1, 2011

Fast characterization of line end shortening and application of novel correction algorithms in e-beam direct write

Freitag, Martin , Choi, Kang-Hoon , Gutsch, Manuela , Hohle, Christoph , Galler, Reinhard , Krüger, Michael , Weidenmüller, Ulf

JM3 Vol. 10 Issue 04

KEYWORDS: Cadmium, Semiconducting wafers, Computer simulations, Electron beams, Detection and tracking algorithms, Electron beam lithography, Point spread functions, Model-based design, Modulation, Nanoelectronics

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PROCEEDINGS ARTICLE | April 4, 2011

Fast characterization of line-end shortening and application of novel correction algorithms in e-beam direct write

Proc. SPIE. 7970, Alternative Lithographic Technologies III

KEYWORDS: Electron beam lithography, Point spread functions, Electron beams, Detection and tracking algorithms, Modulation, Computer simulations, Cadmium sulfide, Electron beam direct write lithography, Semiconducting wafers, Nanoelectronics

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PROCEEDINGS ARTICLE | April 2, 2011

Geometrically induced dose correction: method and performance results

Proc. SPIE. 7985, 27th European Mask and Lithography Conference

KEYWORDS: Lithography, Electron beam lithography, Cadmium, Modulation, Backscatter, Scattering, Cadmium sulfide, Line edge roughness, Photoresist processing, Chemically amplified resists

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PROCEEDINGS ARTICLE | September 25, 2010

Geometrically induced dose correction method for e-beam lithography applications

Proc. SPIE. 7823, Photomask Technology 2010

KEYWORDS: Electron beam lithography, Electron beams, Modulation, Scattering, Laser scattering, Cadmium sulfide, Convolution, Line edge roughness, Photoresist processing, Chemically amplified resists

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PROCEEDINGS ARTICLE | May 15, 2010

Modified dose correction strategy for better pattern contrast

Proc. SPIE. 7545, 26th European Mask and Lithography Conference

KEYWORDS: Semiconductors, Electron beam lithography, Calibration, Laser scattering, Computer simulations, Data processing, Line width roughness, Convolution, Photoresist processing, Data corrections

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All patterning technologies, including e-beam writing, encounter growing challenges to meet the requirements of current and future semiconductor technology nodes. For e-beam writing the electron proximity effect is one of the most prominent influencing factors and its optimal correction is a key for achieving sufficient pattern fidelity. Leading correction algorithms like PROXECCO® currently use a dose modulation strategy for correcting the electron proximity effect. For obtaining minimum feature sizes of below 50 nm and for most demanding patterns like dense line geometries additional correction strategies seem to be necessary to meet the pattern fidelity requirements of the semiconductor industry. The dense line geometries are so sensitive to suboptimal correction because of the achievable contrast in that case, which is minimal. The result is a small process window and an increased line width roughness (LWR). One of the possible modifications of the correction strategy is a combination of dose correction and a variation of the pattern shape. For the scope of this paper we will investigate the potential gains (contrast enhancement) and losses (increase in data prep and writing time) resulting from the so called "geometrically induced dose correction" method available in the current version of PROXECCO® integrated in the ePLACE® software package. ePLACE means eBeam Direct Write and Mask Data Preparation Layout Console and offers the ability to process layout data as well as a state-of-the-art visualization and exposure simulation capabilities. In this paper we show that especially the simulation capability can be used to reduce experimental work significantly. The "geometrically induced dose correction" method is in fact a shape size biasing operation followed by a special dose correction to meet the intended shape edges. By theoretical considerations and by applying the ePLACE® automatic simulation & measurement feature to a huge number of measurement areas we investigate the influence of the geometrically induced dose correction on exposure contrast and CD uniformity for test and real patterns. We also discuss how the geometrically induced dose correction influences the data prep time and finally the e-beam writing time.

PROCEEDINGS ARTICLE | September 23, 2009

Latest results and computing performance of the ePLACE data preparation tool

Proc. SPIE. 7488, Photomask Technology 2009

KEYWORDS: Lithography, Electron beam lithography, Magnesium, Visualization, Data processing, Photomasks, Beam shaping, Data conversion, Computer architecture, Standards development

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PROCEEDINGS ARTICLE | May 27, 2009

A solution to meet new challenges on EBDW data prep

Proc. SPIE. 7470, 25th European Mask and Lithography Conference

KEYWORDS: Lithography, Electron beam lithography, Electron beams, Magnesium, Visualization, Computer simulations, Data processing, Photomasks, Algorithm development, Electron beam direct write lithography

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