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PillarHall Test Chip introduction update 2018


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PillarHall® Test Chip is a special substrate for thin film deposition and related processes. The PillarHall® Test Chip consists of microscopic Lateral High-Aspect-Ratio (LHAR) test structures that offer an easy, fast and accurate way to characterize thin film processes in three dimensional substrate. PillarHall® approach is especially suitable for thin film conformality characterization by deposition methods such as ALD (Atomic Layer Deposition) and Chemical Vapor Deposition (CVD). PillarHall® Test Chips are useful for thin film R&D as well as their manufacturing process control and monitoring.
The core of the PillarHall® LHAR structures is the existence of a wide area lateral air gap under the thin silicon membrane with controlled 500 nm gap height. The name PillarHall comes from the microscopic silicon pillars that stabilize the thin silicon membrane roof. This lateral 3D approach is the core invention and benefit of the PillarHall® technology. The controlled lateral high aspect ratio structures enable fast analysis of thin film conformality without cross-sectioning and tedious sample preparation.
PillarHall® LHAR Test Chips are designed, developed and fabricated in VTT Technical Research Centre of Finland. The PillarHall® MEMS processes and manufacturing is carried out in Micronova Micro- and Nanomanufacturing Centre of VTT in Espoo, Finland.

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PillarHall Test Chip introduction update 2018

  1. 1. Lateral High Aspect Ratio (LHAR) Test Structures for Thin Film Conformality Measurements
  2. 2. 27/06/2018 2 Why conformal thin films are important?  Moore’s law – vertical scaling trend  Core value proposition of ALD: conformal thin films  New opportunities in manufacturing and material science MSW 13.-15.5.2018 Espoo, Finland 3D NAND Source: Applied Materials post 3D NAND FinFETs Mayer et al. APL 82 (2003) 2883.
  3. 3. 27/06/2018 3 Conformal film covers complex 3-D structures uniformly with the same thickness and properties Conformal film, schematic example: a. Optimized ALD  Same film top (1), sidewall (2), bottom (3), deep within (4) Partly conformal & non-conformal films, schematic examples b. Partly conformal, typical for CVD c. Noncormal with overhang, from line-of-sight deposition d. ”Superconformal”, i.e., preferential filling inside the 3-D feature (a) (c) (d)(b) (Side view) 1. 2. 3.4.
  4. 4. 27/06/2018 4 Traditional way of measuring conformality: Cross-sections of vertical trenches in silicon • Measurement takes time & effort, accuracy operator-dependent • Point-per-point analysis, wafer mapping quasi-impossible Vertical HAR procedure: Measure thickness 1. Top 2. Sidewall 3. Bottom Calculate conformality: • Bottom/top xx% • Sidewall/top yy% Aspect ratio (height/width, not in scale) max ~50:1 1. 2. 3. If thinner in trench  conformality <100%
  5. 5. 27/06/2018 5 Why chacterization of vertical microstructures is a PROBLEM ? Analysis needs cross-sectioning. • Sample preparation (FIB) + special analytical tools (HR-TEM) can take weeks and cost 2000-3000 euros for service • Access to test structures is also a headache. • PillarHall enables to do all this and much more without delay - in a price point of a test chip
  6. 6. 27/06/2018 6 Invention
  7. 7. 27/06/2018 7 PillarHall® Innovative LHAR Test Structures: Cross-section without cross-sectioning 1) Test chip as delivered – all silicon 2) Test chip after thin film deposition PillarHall +thin film (ALD,CVD)
  8. 8. 27/06/2018 8 Schematic: uncoated structure Structure after coating with ALD, CVD, … Structure after peeling off the top membrane PillarHall® lateral high-aspect-ratio (LHAR) all-silicon test chips
  9. 9. 27/06/2018 9 LHAR3 PillarHall® Test Chip features: 9 different and 8 parallel LHARs in rectangular test areas, AR from 2:1 to 10 000:1 (gap 500 nm) Scale 100 µm Vertical trenches Additional directional LHARs on edges Distance indicator markers Cleavage line Chip size: 15x20 mm 31 HAR test structures in one chip 1 gap height (default 500 nm) All silicon
  10. 10. 27/06/2018 10 Two basic ways to characterize thin films 1 2
  11. 11. 27/06/2018 11 PillarHall®: Remove top membrane to access detailed, reproducible information of film on Si Photo: Riikka Puurunen, VTT Distance from LHAR opening (µm) Reflectometry Al2O3 ALD For scientific publications, see: DOI 10.1116/1.4903941; DOI acs.langmuir.6b03007 More info to come: Puurunen et al., EuroCVD 2017, accepted; ALD 2017, submitted
  12. 12. 27/06/2018 12 Compatible surface analysis tools COMPATIBLE SURFACE ANALYSIS TOOLS e.g. •Optical microscopy image analysis •Optical reflectometry spectrometry (VIS to SWIR) •Line scans and spectral imaging •Small spot Ellipsometry •AFM and other SPMs •SEM/EDS plan-view •High resolution confocal microscopy •XPS, ToF-SIMS
  13. 13. 27/06/2018 13 Saturation profile terminology for ALD (as proposed by PillarHall) Distance l (µm, mm, …) Relative dimensionless distance (RDD) l / g [r.d.u.] (RDD ~ aspect ratio AR) Amount grown (nm, # of atoms, …) (per cycle) 50%-thickness- penetration-depth (PD50%) Slope at PD50% (  Lumped sticking coefficient) GPC just inside + initial slope Knee GPC just outside x1. 2. 3. 4. 5. 6.
  14. 14. 27/06/2018 14 Predicting and modelling thermal ALD Modeling growth kinetics of thin films made by atomic layer deposition in lateral high-aspect-ratio structures M.Ylilammi, O. Ylivaara and R. L. Puurunen, J.Appl.Phys. In press
  15. 15. 27/06/2018 15 PillarHall®: Benefits  Avoid the need for tedious cross-sections combined with electron microscopy, needed for traditional vertical features  Record-high aspect ratios >10000:1, exposing a parameter space beyond access with traditional vertical structures  Microscopic dimensions suitable for kinetic modelling  Wafer mapping possibility, even nondestructively  IC-compatible silicon test chips  Accuracy in 3 dimensions  Applicable at temperatures up to ~800°C
  16. 16. 27/06/2018 16 PillarHall Test Chip Offering  Test chips in VTT sales offering  Analysis guide manual  IC cleanliness proven certificate  Accompanying service options Chip size: 15 x 15 mm (LHAR4), 15x20 mm (LHAR3, in picture) Gap height: 500 nm + options Test Chips delivered in vacuum release trays (Gel-Pak)
  17. 17. 27/06/2018 17 Scientific publications using PillarHall® test chips 1. Modeling growth kinetics of thin films made by atomic layer deposition in lateral high-aspect- ratio structures, M. Ylilammi, O. M. E. Ylivaara, R. L. Puurunen, J. Appl. Phys. 123 (2018) art. 205301 (8 pages). 2. Microscopic silicon-based lateral high-aspect-ratio structures for thin film conformality analysis, F. Gao, S. Arpiainen, R. L. Puurunen, J. Vac. Sci. Technol. A 33 (2015) 010601., open access pdf. 3. Nucleation and Conformality of Iridium and Iridium Oxide Thin Films Grown by Atomic Layer Deposition, M. Mattinen, J. Hämäläinen, F. Gao, P. Jalkanen, K. Mizohata, J. Räisänen, R. L. Puurunen, M. Ritala, M. Leskelä, Langmuir 32 (2016) 10559-10569. 4. Influence of ALD temperature on thin film conformality: Investigation with microscopic lateral high-aspect-ratio structures, R. L. Puurunen, F. Gao, Proceedings of the International Baltic Conference on Atomic Layer Deposition, 2-4 Oct 2016, St. Petersburg, Russia. Electronically published in IEEE Xplore,
  18. 18. CONTACT: Dr. Mikko Utriainen Sales responsible of PillarHall @VTTFinland Tel. +358 40 753 7415 or