Bastos Fanta, Alice

Han, Anpan

Jansen, Henri

Todeschini, Matteo

Wagner, Jakob B.

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: Mar 29, 2019In-situ transmission Kikuchi diffraction for high T characterization in nanofabricationTodeschini, Matteo; Jansen, Henri; Wagner, Jakob Birkedal; Han, Anpan; Bastos da Silva Fanta, AlicePublication date:2018Document VersionPeer reviewed versionLink back to DTU OrbitCitation (APA):Todeschini, M., Jansen, H., Wagner, J. B., Han, A., & Bastos Fanta, A. (2018). In-situ transmission Kikuchidiffraction for high T characterization in nanofabrication. Abstract from 44th International conference on Microand Nano Engineering, Copenhagen, Denmark.In-situ transmission Kikuchi diffraction for high T thin-film characterization in nanofabrication Matteo Todeschini a, Henri Jansen a, Jakob B. Wagner a, Anpan Han a, Alice Bastos Fanta a  a DTU Danchip/Cen, Technical University of Denmark, 2800 Kongens Lyngby, Denmark e-mail: anph@dtu.dk   Keywords: transmission Kikuchi diffraction, in-situ analysis, ultra-thin metal film characterization The fabrication process of increasingly complex multi-material and multi-layer structures and devices in nanofabrication includes thermal treatments that might affect the nanostructure and stability of the films heavily. In particular, pre-bake and post-bake processes involve the use of a heat treatment on the sample for periods varying from one to 30 minutes (and even hours for the case of very thick resists) and using temperatures ranging from 100˚C to 200˚C. An important temperature-related problem for the application of such systems is solid-state dewetting1, the agglomeration of the film to form islands or nanoparticles when heated to sufficiently high temperatures, in order to minimize the total energy of the free surfaces of the film and substrate and of the film-substrate interface. This is due to the intrinsic thin-film metastability as a consequence of its formation far from equilibrium. Dewetting can have a harmful effect on the performances and time-stability of the fabricated devices, leading to the extreme case of interconnect failure and degradation of the electronic devices due to overheating. Dewetting has been characterized and described ex-situ with SEM and TEM mostly above 400˚C, while below 200˚C the film stability has not been studied in detail. Therefore the investigation of the changes in crystal structure, grain size and crystallographic texture of thin films due to thermal treatments requires the introduction of innovative techniques having nanoscale resolution and being able to operate in a wide range of temperatures.  In this study, we demonstrate the in-situ capabilities of transmission Kikuchi diffraction (TKD) for the analysis of ultra-thin Au films at high temperature2. The metal thin films were deposited by e-beam evaporation on MEMS-based heating microchips having a Pt coil-based embedded heating system (Fig. 1a). The research area is formed by 20 nm-thick electron transparent Si3N4 membranes having dimensions of roughly 5 x 20 μm (Fig. 1b). The microchip is mounted inside the SEM using a purpose designed holder with a built-in 45˚ tilt. When inside the microscope, the holder is tilted to 45˚, in order to place the microchip perpendicular with respect to the electron beam (Fig. 2). This way an on-axis Bruker‐Flash OPTIMUS detector is used to acquire TKD maps in an FEI Nova Nanolab 600 SEM. The TKD maps were acquired in low vacuum conditions (50 Pa). The dewetting of an Au thin film into Au nanoparticles upon heating was followed with orientation mapping in a temperature range between 20˚C and 900˚C. The evolution of grain size and film texture and the growth of holes in the film were tracked throughout the process with high resolution, accuracy and statistical significance. Several sources of influence on the quality and resolution of the acquired TKD maps were investigated: disturbance from infrared radiation, maximum measurable Au thickness, loss of crystalline order, thermal drift during heating, plasma cleaning of the sample and thickness variation of the film. A quasi in-situ TKD mapping was also used to observe the positive impact on the stability of the Au nanostructure at elevated temperatures due to the presence of Ti and Cr transition metals used as adhesion layers. The results showed that the continuity of the Au film was preserved up to 500˚C using either of the adhesion layers (Fig. 3), but also how Cr and Ti have a different impact on the final Au film nanostructure, in particular with the Cr layer stopping the Au grain growth almost completely. Further studies will include the high-resolution observation of the starting point of dewetting and the analysis of the stability of Au nanostructure when non-metallic adhesion layers, such APTMS3, are used. [1] C. V. Thompson, Annu. Rev. Mater. Res. 42 (2012) 399-434. [2] A. B. Fanta, M. Todeschini, A. Burrows, H. Jansen, C. D. Damsgaard, H. Alimadadi, J. B. Wagner, Mat. Charact. 139 (2018), 452-462. [3] J. Sukham, O. Takayama, A. V. Lavrinenko, R. Malureanu, ACS Appl. Mater. Interfaces 9 (29) (2017) 25049-25056.   Figure 1. a) Structure of the MEMS microchip with resistance (R) and current (I) contacts highlighted. b) Zoom of the research area: the electron transparent Si3N4 membranes and the embedded Pt heating coils are visible. Figure 2. Image of the TKD system configuration. The 45˚ tilted holder supporting the microchip and the on-axis TKD detector are visible.  Figure 3. Out of plane inverse pole figure (IPF) quasi in-situ TKD maps at selected temperatures, showing the nanostructure evolution with temperature of a 20 nm pure Au film (top), a 2 nm Ti/20 nm Au bilayer (middle) and a 2 nm Cr/20 nm Au bilayer system (bottom). The pure Au film starts to dewet between 100°C and 200˚C and at 500˚C the film is heavily damaged. When Ti and Cr adhesion layers are used, the film remains continuous up to 500˚C. 

In-situ transmission Kikuchi diffraction for high T characterization in nanofabrication

http://orbit.dtu.dk/ws/files/154891244/MNE_2018_Abstract_Matteo_Todeschini_FINAL.pdf

In-situ transmission Kikuchi diffraction for high T characterization in nanofabrication

Abstract

Similar works

Full text

Available Versions

Online Research Database In Technology