Beleggia, Marco

Greibe, Tine

Han, Anpan

Tiddi, William

Online Research Database In Technology

                       General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.  • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal   If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.     Downloaded from orbit.dtu.dk on: Nov 08, 2017Proximity Effects in a Chemically Amplified Electron Beam Resist Patterned at 100 keVTiddi, William; Greibe, Tine; Beleggia, Marco; Han, AnpanPublished in:Book of Abstracts. DTU's Sustain Conference 2015Publication date:2015Document VersionPublisher's PDF, also known as Version of recordLink back to DTU OrbitCitation (APA):Tiddi, W., Greibe, T., Beleggia, M., & Han, A. (2015). Proximity Effects in a Chemically Amplified Electron BeamResist Patterned at 100 keV. In Book of Abstracts. DTU's Sustain Conference 2015 [P-12] Lyngby: TechnicalUniversity of Denmark (DTU).   Proximity Effects in a Chemically Amplified Electron Beam Resist Patterned at 100 keV W.Tiddi1,2*, T. Greibe1, M. Beleggia2, A. Han1 1: DTU Danchip; 2: DTU CEN *wiltid@dtu.dk  Electron beam lithography (EBL) is a patterning technique providing nanometric resolution. It is widely used in research, optical and nanoimprint lithography mask production, and parallel EBL is intended to be adopted in future next generation high through-put semiconductor device production [1]. Sub-20 nm patterning has been demonstrated on negative tone, epoxy-based chemically amplified EBL resists such as mr-EBL 6000 [2]. This material is characterized by significantly reduced dose sensitivity, which would provide faster, more cost-effective production. When distances between structures are comparable to the intended critical (smallest) feature dimension, proximity effects (PE) caused by forward and back scattered electrons deteriorate the quality of the resulting pattern. PE on mr-EBL 6000 were observed when patterning with 10 and 20 keV electron beams, and compensated through dose modulation algorithms [3]. The present investigation focused instead on PE in mr-EBL at substantially higher electron energy and is to our knowledge new. To understand these conditions and their expected profound influence on PE, we patterned carefully arranged structures at  100 keV, and transferred them into a silicon substrate by reactive ion etching (RIE). We successfully patterned 50 to 500 nm wide lines, and we observed pattern deterioration when feature separation approached 5 times the line width (Fig. 1). We attribute this to PE. As a simple optimization, we showed how under-dosed patterns offer appreciable improvements in minimum obtainable pitch, and obtained analogous results in films thinner than 40 nm, an expected mandatory requirement to push manufacturing towards sub-10 nm half-pitch resolution [4]. [1] G. de Boer et al., Proc. Of SPIE 8680 (2013) 86800O-12. [2] B. Bilenberg et al., J. Vac. Sci. Technol. B 24 (2006) 1776. [3] G. Rius, E-beam litho. for Nanofabrication, Ph.D. Thesis, Dept. of Phys., Uni. Autò. Barcelona, 2008. [4] A. Tavakkoli K. G. et al., J. Vac. Sci. Technol. B 29 (2011) 011035.       Figure 1 – Cross sectional SEM image of progressively closer spaced lines patterned in resist (a)  and transferred into silicon through RIE (b). We observe overexposure in denser patterns because of PE; the resulting distorted pattern is this way reproduced into the underlying substrate. Sustain DTU Abstract: P-12

Proximity Effects in a Chemically Amplified Electron Beam Resist Patterned at 100 keV

                       General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.  • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal   If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.     Downloaded from orbit.dtu.dk on: Nov 08, 2017Proximity Effects in a Chemically Amplified Electron Beam Resist Patterned at 100 keVTiddi, William; Greibe, Tine; Beleggia, Marco; Han, AnpanPublication date:2015Document VersionPeer reviewed versionLink back to DTU OrbitCitation (APA):Tiddi, W., Greibe, T., Beleggia, M., & Han, A. (2015). Proximity Effects in a Chemically Amplified Electron BeamResist Patterned at 100 keV. Abstract from 41st International conference on Micro and Nano Engineering , TheHague, Netherlands.Proximity Effects in a Chemically Amplified Electron Beam Resist Patterned at 100 keV  W.Tiddi a, T. Greibe a, M. Beleggia b, A. Han a  a DTU Danchip, Technical University of Denmark, Kgs. Lyngby, 2800, Denmark b DTU Cen, Technical University of Denmark, Kgs. Lyngby, 2800, Denmark e-mail: anph@dtu.dk    Keywords: electron beam lithography, chemically amplified resist, negative resist, proximity effects Electron beam lithography (EBL) is a mask-less patterning technique providing nanometric resolution. It is widely adopted in research, optical and nanoimprint lithography mask production, and parallel EBL is intended for high through-put semiconductor device production [1]. Sub-20 nm patterning with significantly reduced dose sensitivities has been demonstrated on negative tone, epoxy-based chemically amplified EBL resists such as mr-EBL 6000 (from Micro Resist Technology GmbH) [2].   When distances between patterns are comparable to the pattern size, proximity effects (PE) caused by forward and back scattered electrons deteriorate EBL pattern quality. PE on mr-EBL 6000 were observed at 10 and 20 keV, and compensated through dose modulation algorithms [3]. However, we could not find prior work on its exposure to higher energy EBL, which is expected to influence these effects profoundly. To investigate PE at higher energy, we patterned carefully arranged structures at 100 keV, and transferred them into a silicon substrate by reactive ion etching (RIE).  We realized 90 nm thick films using mr-EBL 6000.1 XP resist solution on silicon substrates, and we exposed them with a JEOL JBX-9500 instrument operating at 100 keV. After a 5 min post-exposure bake at 110 ºC, we developed the samples for 40 s in mr-Dev 600, rinsed with isopropanol, and blow-dried. Patterns were transferred into the substrate with a C4F8/SF6 RIE process, and the residual resist removed by oxygen plasma. Platinum coating to avoid charging during SEM inspection was performed when necessary.  We successfully patterned 50 to 500 nm wide lines, and we observed pattern deterioration when feature separation approached 5 times the line width (Fig. 1). We attribute this to PE. Overexposure due to PE became even more evident for wider lines, and it was clearly very sensitive to dose (Fig. 2) which we attributed to the chemically amplified nature of the resist. Hence, to improve pattern quality, we carried out a series of exposure and resist characterization experiments to construct the contrast curve, and we measured 30 µC/cm2 as clearance dose for 100 nm isolated lines (D1). When patterning with doses one third lower than D1 we managed to resolve lines at higher density (Fig. 3) without need for PE corrective algorithms. Such lines showed tapering in the etched profile due to the underdosed sidewalls profile. We then diluted the original resist solution 1:1 with anisole, obtaining homogeneous films as thin as 30 nm, and we successfully used them to reproduce patterns as in the first approach (Fig. 4). Although we didn’t assess eventual improvements due to the reduced thickness, this is expected to limit forward scattering in the resist and it is considered a mandatory requirement to achieve sub-10 nm half-pitch resolution [4].   Our work focused on assessing PE in mr-EBL 6000 with 100 keV EBL. We observed PE-related overexposure in overlapping and neighboring features which was not present in isolated lines. As a simple optimization, we assessed the effects of under-dosing with appreciable results in the final profile. We then showed that uniform thinner resist films can be obtained and patterned as well, as a preliminary step to push its resolution limits. We combined these two approaches and obtained a superior pattern definition: although still imperfect, we show good resolution over most of the test structures. [1] G. de Boer et al., Proc. Of SPIE 8680 (2013) 86800O-12. [2] B. Bilenberg et al., J. Vac. Sci. Technol. B 24 (2006) 1776. [3] G. Rius, E-beam litho. for Nanofabrication, Ph.D. Thesis, Dept. of Phys., Uni. Autò. Barcelona, 2008. [4] A. Tavakkoli K. G. et al., J. Vac. Sci. Technol. B 29 (2011) 011035.   Figure 1. Cross sectional SEM image of progressively closer spaced lines patterned in resist (a) and transferred into silicon through RIE (b). We observe overexposure in denser patterns because of PE; the resulting distorted pattern is then reproduced into the underlying substrate.  Figure 2. SEM top view of resist line patterns 500 nm wide (a) and 200 nm wide (b). Decreasing doses from left to right: 22, 19, 16 µC/cm2. PE lead to over exposed lines and areas with interstitial residues between lines; a small decrease in dose significantly reduces these effects.  Figure 3. SEM image of underdosed lines transferred into silicon through RIE. Spacing down to 200 nm gets now properly resolved.. Figure 4. SEM top view of 100 nm wide test structures patterned in 38 nm thick resist and transferred into silicon through RIE. 

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Proximity Effects in a Chemically Amplified Electron Beam Resist Patterned at 100 keV

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