Flexible silicon

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Flexible silicon refers to a flexible piece of mono-crystalline silicon. Several processes have been demonstrated in the literature for obtaining flexible silicon from single crystal silicon wafers (either before or after fabrication of CMOS circuits). [1]

Contents

Background

According to beam theory and the 3-point test of a rectangular beam of an isotropic linear material, a perpendicular specific force applied to a rectangular beam would cause it to deflect as a function of its dimension parameters and material properties (i.e., flexural modulus). All parameters are fixed, and the dependence of the deflection on thickness is inversely proportional, i.e., the thinner the beam, the more it deflects when the same force is applied. Simplistically, the applied force per unit area is the stress experienced by the beam. For two beams made of similar materials, but one is thinner than the other, a lower force (stress) is required to achieve the same deflection in the thinner beam. This opens up the possibility of reducing a beam's thickness to adjust the magnitude of stress it can handle before physically breaking if the deflection requirement is the same. Applying this concept to the commonly used brittle Monocrystalline silicon (100) substrates, it can achieve some flexibility (note that silicon is an anisotropic material and requires dealing with an elasticity matrix, a tensor, not a simple value for flexural modulus). This is done using various micro-fabrication techniques and novel approaches to reduce the silicon substrate thickness to a few to tens of micrometers, enabling bending up to 0.5 cm radius without breaking.

Processes

Etch protect release approach and backside etch are a few examples of how this can be achieved. These techniques have been extensively used to demonstrate flexible versions of traditional high-performance CMOS-compatible devices, including 3D fin-field effect transistors (finFETs) [2] [3] and planar metal–oxide–semiconductor FETs (MOSFETs), [4] metal-oxide-semiconductor/metal-insulator-metal capacitors (MOSCAPs and MIMCAPs), [5] [6] [7] ferroelectric capacitors and resistive devices, [8] [9] [10] [11] and thermoelectric generators (TEGs). [12]

References

  1. ↑ Hussain, Aftab M.; Hussain, Muhammad M. (June 2016). "CMOS-Technology-Enabled Flexible and Stretchable Electronics for Internet of Everything Applications". Advanced Materials. 28 (22): 4219–4249. Bibcode:2016AdM....28.4219H. doi:10.1002/adma.201504236. PMID   26607553. S2CID   28740742.
  2. ↑ Ghoneim, Mohamed; Alfaraj, Nasir; Torres-Sevilla, Galo; Fahad, Hossain; Hussain, Muhammad (July 2016). "Out-of-Plane Strain Effects on Physically Flexible FinFET CMOS". IEEE Transactions on Electron Devices. 63 (7): 2657–2664. Bibcode:2016ITED...63.2657G. doi:10.1109/TED.2016.2561239. hdl: 10754/610712 . S2CID   26592108.
  3. ↑ Torres Sevilla, Galo A; Ghoneim, Mohamed T; Fahad, Hossain; Rojas, Jhonathan P; Hussain, Aftab M; Hussain, Muhammad M (5 September 2014). "Flexible nanoscale high-performance FinFETs". ACS Nano. 8 (10): 9850–6. doi:10.1021/nn5041608. PMID   25185112.
  4. ↑ Rojas, Jhonathan P; Torres Sevilla, Galo A; Hussain, Muhammad M (10 September 2013). "Can we build a truly high performance computer which is flexible and transparent?". Scientific Reports. 3: 2609. Bibcode:2013NatSR...3.2609R. doi:10.1038/srep02609. PMC   3767948 . PMID   24018904.
  5. ↑ Ghoneim, Mohamed T.; Rojas, Jhonathan P.; Young, Chadwin D.; Bersuker, Gennadi; Hussain, Muhammad M. (26 November 2014). "Electrical Analysis of High Dielectric Constant Insulator and Metal Gate Metal Oxide Semiconductor Capacitors on Flexible Bulk Mono-Crystalline Silicon". IEEE Transactions on Reliability. 64 (2): 579–585. doi:10.1109/TR.2014.2371054. S2CID   11483790.
  6. ↑ Ghoneim, Mohamed T.; Kutbee, Arwa; Ghodsi, Farzan; Bersuker, G.; Hussain, Muhammad M. (9 June 2014). "Mechanical anomaly impact on metal–oxide–semiconductor capacitors on flexible silicon fabric". Applied Physics Letters. 104 (23): 234104. Bibcode:2014ApPhL.104w4104G. doi:10.1063/1.4882647. hdl: 10754/552155 . S2CID   36842010.
  7. ↑ Rojas, Jhonathan P; Ghoneim, Mohamed T; Young, Chadwin D; Hussain, Muhammad M (October 2013). "Flexible High-k Metal Gate Metal/Insulator/Metal Capacitors on Silicon (100) Fabric". IEEE Transactions on Electron Devices. 60 (10): 3305–3309. doi:10.1109/TED.2013.2278186. S2CID   39246663.
  8. ↑ Ghoneim, Mohamed T.; Hussain, Muhammad M. (23 July 2015). "Review on physically flexible nonvolatile memory for internet of everything electronics". Electronics. 4 (3): 424–479. arXiv: 1606.08404 . doi: 10.3390/electronics4030424 .
  9. ↑ Ghoneim, Mohamed T.; Hussain, Muhammad M. (3 August 2015). "Study of harsh environment operation of flexible ferroelectric memory integrated with PZT and silicon fabric". Applied Physics Letters. 107 (5): 052904. Bibcode:2015ApPhL.107e2904G. doi:10.1063/1.4927913. hdl: 10754/565819 .
  10. ↑ Ghoneim, Mohamed T.; Zidan, Mohammed A.; Alnassar, Mohammed Y.; Hanna, Amir N.; Kosel, Jurgen; Salama, Khaled N.; Hussain, Muhammad (15 June 2015). "Flexible Electronics: Thin PZT-Based Ferroelectric Capacitors on Flexible Silicon for Nonvolatile Memory Applications". Advanced Electronic Materials. 1 (6): 1500045. doi: 10.1002/aelm.201500045 . S2CID   110038210.
  11. ↑ Ghoneim, Mohamed T; Zidan, Mohammed A; Salama, Khaled N; Hussain, Muhammad M (30 November 2014). "Towards neuromorphic electronics: Memristors on foldable silicon fabric". Microelectronics Journal. 45 (11): 1392–1395. doi:10.1016/j.mejo.2014.07.011.
  12. ↑ Torres Sevilla, Galo; Bin Inayat, Salman; Rojas, Jhonathan; Hussain, Aftab; Hussain, Muhammad (9 December 2013). "Flexible and Semi-Transparent Thermoelectric Energy Harvesters from Low Cost Bulk Silicon (100)". Small. 9 (23): 3916–3921. doi:10.1002/smll.201301025. PMID   23836675.
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