Research Update: Electron beam-based metrology after CMOS

Abstract

The magnitudes of the challenges facing electron-based metrology for post-CMOS technology are reviewed. Directed selfassembly, nanophotonics/plasmonics, and resistive switches and selectors, are examined as exemplars of important post-CMOS technologies. Materials, devices, and architectures emerging from these technologies pose new metrology requirements: defect detection, possibly subsurface, in soft materials, accurate measurement of size, shape, and roughness of structures for nanophotonic devices, contamination-free measurement of surface-sensitive structures, and identification of subtle structural, chemical, or electronic changes of state associated with switching in non-volatile memory elements. Electron-beam techniques are examined in the light of these emerging requirements. The strong electron-matter interaction provides measurable signal from small sample features, rendering electron-beam methods more suitable than most for nanometer-scale metrology, but as is to be expected, solutions to many of the measurement challenges are yet to be demonstrated. The seeds of possible solutions are identified when they are available.

Metrology for the next generation of semiconductor devices

“…Other improvements that could extend the use of CD-SEMs for GAA and beyond include low-damage and very low-energy operation (coupled with electrons from higher brightness sources), very low-electron-energy variation, and use of innovative aberration-corrected electron-optical columns 66 , eliminating electron-beam-induced contamination, and dose rate management to minimize sample damage. Low-energy operation would be useful in measuring beam-sensitive low-contrast materials or filaments in nanoionics memristors as was previously done for Ag filaments in an Ag/H2O/Pt structure 67 or other types of beyond CMOS resistive switches and selectors 68 .…”

Simulating HV-SEM imaging of HAR and buried features

“…NIST has supported ongoing improvement and validation efforts since, and it is now well validated for non-charging cases, with some use by a small user community. [1][2][3][4][5][6][7][8][9][10][11][12][14][15][16][17][18][19] JMONSEL uses finite element analysis (FEA) to track primary electrons as they enter a material, scatter, lose energy, and generate secondary & backscattered electrons. By monitoring the electrons that exit the material and are captured by a detector (software counter element), the electron yields can be found at any point designated as a target pixel.…”

“…In this work, a few of the most important use cases for HV-SEM will be explored, such as HAR hole and trench imaging with various profiles and depths, buried feature imaging to understand detection and effective resolution with depth for a few common materials sets of interest in the optical overlay cases, and buried defect and void detection will be explored using the SEM simulation software based on NIST's JMONSEL [1][2][3][4][5][6][7][8][9][10][11], AMAG SimuSEM [12], which makes possible, through its elegant and powerful GUI, detailed and thorough SEM simulation experiments with much utility, productivity, flexibility, visualization, accessibility, and achievable complexity of designed features with fast simulation speeds, including running on remote cloud resources at large scale. The use of simulation DOEs to predict best conditions and performance for the above applications will be demonstrated, along with some validation in the HV-SEM process space for the JMONSEL/SimuSEM physics kernel by reproducing a few cases in the literature by simulation, and to images of various recent AMAG7 HAR measurement targets [13].…”

Review—Beyond the Highs and Lows: A Perspective on the Future of Dielectrics Research for Nanoelectronic Devices

“…802,803 It also important to note that the insulating nature of dielectric materials can present additional challenges to more established chargebased techniques such as the scanning and transmission electron microscopies (SEM/TEM) most commonly utilized for imaging and dimensional metrology (film thickness, device critical dimensions). 804 Specifically, the interaction between an electron beam and an insulating material can produce charging and film shrinkage side effects that lead to dubious or erroneous results. [805][806][807][808] In this regard, optical and x-ray-based techniques may eliminate some of these issues.…”