Peter De Bisschop received his PhD in physics from Leuven University, Belgium, with a Ph.D. thesis on hyperfine interactions of short-living Sr isotopes.
He moved to imec in 1986, where he worked on the development of a laser-assisted SIMS technique in the Materials Analysis department..
In 1995, he joined the Lithography Department. He worked on diverse topics related to exposure-tool-control and -qualification, imaging, masks, rigorous simulations, OPC, and DTCO. His focus in the past few years has been on stochastic effects in EUVL.
During the past 25 years, he has also been involved in a lithography-teaching program that imec provides to some of its member companies.
He moved to imec in 1986, where he worked on the development of a laser-assisted SIMS technique in the Materials Analysis department..
In 1995, he joined the Lithography Department. He worked on diverse topics related to exposure-tool-control and -qualification, imaging, masks, rigorous simulations, OPC, and DTCO. His focus in the past few years has been on stochastic effects in EUVL.
During the past 25 years, he has also been involved in a lithography-teaching program that imec provides to some of its member companies.
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Imec has already evaluated on test chip vehicles with different patterning approaches: 193i SAQP (Self-Aligned Quadruple Patterning), LE3 (triple patterning Litho Etch), tone inversion, EUV SE (Single Exposure) with SMO (Source-mask optimization). Following the run path in the technology development for EUV insertion, imec N7 platform (iN7, corresponding node to the foundry N5) is developed for those BEoL layers.
In this paper, following technical motivation and development learning, a comparison between the iArF SAQP/EUV block hybrid integration scheme and a single patterning EUV flow is proposed. These two integration patterning options will be finally compared from current morphological and electrical criteria.
To be effective during the lithographic EUV material screening phase for such tight pitches, it is necessary to implement complementary metrology analyses that can provide precise information on the resist roughness and a quick feedback on the quantification of nano-failures (nano-bridges, broken lines, merging or missing contacts) induced by a stochastic EUV patterning regime, the random nature of the light-matter interaction and consequent chemical reactions. Beside the traditional approach to characterize a resist with metrics as exposure latitude (EL%), depth of focus (DoF) and line-edge-roughness (LER) based on CDSEM measurements, we have used the power spectra density (PSD) [4] to get an unbiased value of the resist line roughness (LWR and LER) by using Fractilia metroLERTM commercial software. Further, we have used Stochalis imec software [5] to quantify patterning nano failures providing an early stage assessment on the patterning fidelity of the examined resists.
We present the resist characterization results for 32nm dense line-space pattern on different substrates and for 36nm dense and orthogonal contact hole pitch pattern for different photoresists. Two positive tone chemically amplified (CA) resists have been identified at the exposure dose of 45mJ/cm2 and 33mJ/cm2 for logic (pitch 32nm dense line/space) and memory (pitch 36nm dense contact holes) use cases, respectively.
We study stochastic responses for three technology nodes:
• An SRAM cell for 7 nm technology node, with Numerical Aperture = 0.33 and patterned with organic chemically amplified resist
• An SRAM cell for 5 nm technology node, with Numerical Aperture = 0.33 and patterned with:
o Organic chemically amplified resist
o Fast photospeed organic chemically amplified resist
o Metal-oxide resist
• An SRAM cell for 3 nm technology node, patterned with organic chemically amplified resist and:
o Numerical Aperture = 0.33 in single exposure
o Numerical Aperture = 0.33 with double exposure
o Numerical Aperture = 0.55 with anamorphic pupil
For each case, we optimize mask bias, source illumination and process conditions across focus to maximize the optical contrast. We did not apply optical proximity correction to the mask. The purpose of the work is to evaluate the stochastic behavior of different features as a function of material strategy, technology node, and lithographic approach.
This paper provides a thorough experimental assessment of the implementation of vote-taking, and discusses its pro’s and con’s. Based on N=4 vote-taking, we demonstrate the capability to mitigate different types of mask defects. Additionally, we found that blending different mask images brings clear benefit to the imaging, and provide experimental confirmation of improved local CDU and intra-field CDU, reduction of stochastic failures, improved overlay, ... Finally, we perform dedicated throughput calculations based on the qualification performance of ASML’s NXE:3400B scanner.
This work must be seen in the light of an open-minded search for options to optimally enable and implement EUV lithography. While defect-free masks and EUV pellicles are without argument essential for most of the applications, we investigate whether some applications could benefit from vote-taking.
We have successfully developed a triple patterning decomposition methodology that can effectively decompose an entire layout block or a chip. Formulating a triple patterning decomposition problem into a graph 3-color problem, the system first builds a graph to represent the layout. It then tries to reduce and partition the graph without changing its 3-colorability property. To color the reduced graph, we adopt a hybrid approach with a fast heuristic for coloring and an exact coloring algorithm for backup and conflict verification.
Unlike an odd cycle in double patterning, a triple patterning coloring conflict can’t be represented in a single loop. Another challenge for triple patterning is then how to report errors that the user can effectively use to fix them. For this purpose, minimum fix guidance – minimum to fix a conflict, and maximal minimum fix guidance – maximal choices are presented.
Stochastic and systematic patterning failure mechanisms for contact-holes in EUV lithography: Part 2
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