Browsing by Author "Heikkinen, Ismo T.S."

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Approaches to Open Source 3-D Printable Probe Positioners and Micromanipulators for Probe Stations
(2018-10) Hietanen, Iiro; Heikkinen, Ismo T.S.; Savin, Hele; Pearce, Joshua M.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Three types of highly-customizable open source probe positioning systems are evaluated: (a) mostly 3-D printed, (b) partially printed using OpenBeam kinematic constraints, and (c) a 3-level stack of low-cost commercial single axis micropositioners and some printed parts. All systems use digital distributed manufacturing to enable bespoke features, which can be fabricated with RepRap-class 3-D printer and easily accessible components. They are all flexible in material choice for custom components. The micropositioners can be set up for left-right use and flat or recessed configurations using either mechanical or magnetic mounting. All systems use a manual probe holder that can be customized and enable a quick swap probe system. System (a) is purchased for $100 or fabricated for 200 microns, (b) 40 microns and (c) 10 microns. A tradeoff is observed for 3-D printed percent between cost and accuracy. All systems provided substantial cost savings over proprietary products with similar functionality.
Atomic layer deposited aluminum oxide mitigates outgassing from fused filament fabrication–based 3-D printed components
(2020-03-25) Heikkinen, Ismo T.S.; Marin, Giovanni; Bihari, Nupur; Ekstrum, Craig; Mayville, Pierce J.; Fei, Yuhuan; Hu, Yun Hang; Karppinen, Maarit; Savin, Hele; Pearce, Joshua M.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Open-source scientific hardware based on affordable fused filament fabrication (FFF) 3-D printing has the potential to reduce the cost of research tools considerably. So far, development has focused on tools that do not require compatibility with vacuum environments. Highly porous 3-D printed plastics require surface treatments to mitigate their outgassing, and in this study we explored the outgassing reduction from 3-D printed black-colored acrylonitrile butadiene styrene (ABS) and polycarbonate (PC) using a commercial vacuum sealing resin as well as atomic layer deposited (ALD) aluminum oxide (AlOx). The outgassing properties of uncoated plastics could not be measured due to a too high level of outgassing, which was attributed to their high porosity and high specific surface area. However, both the commercial resin and the ALD coatings reduced the extent of outgassing from both ABS and PC, which enabled their comparison by residual gas analysis (RGA). Remarkably, the outgassing performance achieved with ALD AlOx was superior to the performance of the commercial vacuum resin across a temperature range of 40 to 100 °C for both plastics, despite the uneven coverage of the plastic surface with AlOx. Results indicated that both ABS and PC could be made compatible with at least moderate vacuums using ALD AlOx. Thus, the fabrication of laboratory vacuum tools can be realized with affordable 3-D printed plastics. However, further studies on the physical mechanisms behind the outgassing reduction and the durability of the coatings are required.
Can hydrogenation mitigate Cu-induced bulk degradation in silicon?
(2020) Heikkinen, Ismo T.S.; Wright, Brendan; Soeriyadi, Anastasia H.; Yli-Koski, Marko; Kim, Moonyong; Vähänissi, Ville; Hallam, Brett J.; Savin, Hele
A4 Artikkeli konferenssijulkaisussa
Many defects can cause significant bulk degradation in crystalline silicon, which inherently limits solar cell efficiency. Perhaps the most well-known source of light-induced bulk degradation (LID) in Czochralski-grown silicon is the boron-oxygen defect. However, metal impurities, such as copper, can also cause severe degradation. Advanced hydrogenation processes incorporating minority carrier injection can effectively passivate boron-oxygen complexes, but their effect on copper-induced degradation has not been studied previously. Herein, we explore the effect of hydrogenation on LID in copper-contaminated silicon. Without hydrogenation the bulk lifetime decreases down to 5\ \mu\mathrm{s} while in hydrogenated samples the bulk lifetime remains above 300\ \mu\mathrm{s} during the whole degradation cycle. The results thus indicate that even in heavily copper-contaminated silicon hydrogenation can passivate Cu precipitates and mitigate Cu-LID.
Chemical compatibility of fused filament fabrication-based 3-D printed components with solutions commonly used in semiconductor wet processing
(2018-10-01) Heikkinen, Ismo T.S.; Kauppinen, Christoffer; Liu, Zhengjun; Asikainen, Sanja M.; Spoljaric, Steven; Seppälä, Jukka V.; Savin, Hele; Pearce, Joshua M.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
3-D printing shows great potential in laboratories for making customized labware and reaction vessels. In addition, affordable fused filament fabrication (FFF)-based 3-D printing has successfully produced high-quality and affordable scientific equipment, focusing on tools without strict chemical compatibility limitations. As the additives and colorants used in 3-D printing filaments are proprietary, their compatibility with common chemicals is unknown, which has prevented their widespread use in laboratory chemical processing. In this study, the compatibility of ten widely available FFF plastics with solvents, acids, bases and solutions used in the wet processing of semiconductor materials is explored. The results provide data on materials unavailable in the literature and the chemical properties of 3-D printable plastics that were, are in line with literature. Overall, many 3-D printable plastics are compatible with concentrated solutions. Polypropylene emerged as a promising 3-D printable material for semiconductor processing due to its tolerance of strongly oxidizing acids, such as nitric and sulfuric acids. In addition, 3-D printed custom tools were demonstrated for a range of wet processing applications. The results show that 3-D printed plastics are potential materials for bespoke chemically resistant labware at less than 10% of the cost of such purchased tools. However, further studies are required to ascertain if such materials are fully compatible with clean room processing.