SCIENCE CHINA Information Sciences, Volume 61 , Issue 6 : 060419(2018) https://doi.org/10.1007/s11432-018-9430-2

Parylene-MEMS technique-based flexible electronics

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  • ReceivedJan 10, 2018
  • AcceptedMar 27, 2018
  • PublishedMay 14, 2018



This work was financially supported by National Natural Science Foundation of China (Grant No. U1613215), Beijing Natural Science Foundation (Grant No. L172005), and National Basic Research Program of China (973) (Grant No. 2015CB352100).


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  • Figure 1

    (Color online) Schematic illustration of the work principle of the proposed parylene-MEMS based flexible electronics. (a) Top view of two units and the parylene-filled trenches around them; (b) cross-sectional view of a set of parallel parylene-filled trenches; (c) the bended structure upon applied forces.

  • Figure 2

    (Color online) Microfabrication process of the flexible temperature controlling array. (a) Metal pattering on the silicon oxide layer; (b) trench etching; (c) parylene deposition to fill the trenches; (d) parylene etching by the oxygen plasma; (e) Au wires electroplating; (f) parylene deposition and patterning; (g)removing the silicon beneath the trench;protect łinebreak (h) parylene deposition after removing all the remnant silicon.

  • Figure 3

    (Color online) Results of the parylene trench-filling experiments. (a) SEM photos of the conformal deposition and the keyhole in the parylene-filled trench; (b) definitions of $X_b$ and $X_t$; (c) definition of the slant angle; (d) conformal ratios for the cases with different width of the trench: 3.3, 6.5, 15, 30 $\mu$m, the depth was 40 $\mu$m; (e) conformal ratios for the cases with different depth of the trench: 4, 18, 38, 60, 92 $\mu$m, the width was 5.5 $\mu$m; (f) conformal ratios for the cases with different slant angle of the trench: $-$0.8$^\circ$, 0$^\circ$, 2.3$^\circ$; the depth was 18 $\mu$m and the width of the bottom was 3 $\mu$m.

  • Figure 4

    (Color online) SEM images. (a) Profile of one-step-filled trenches, the inserted one is a magnified view of the trench opening; (b) profile of the trenches after a filling-etching-refilling process, the inserted one is a magnified view of the trench opening; (c) surface of the parylene-filled trenches.

  • Figure 5

    (Color online) Performances of thermal isolation, electrical isolation and mechanical connection of the parylene-filled trenches. (a) Schematic of the thermal isolation test; (b) schematic of the electrical isolation test; (c) schematic of the mechanical connection test; (d) the temperature variation of units 1 and 2 when unit 1 was heated; (e) I-V relationship of air, parylene-filled trenches, PMMA and glass, inset showed the details of the former three samples; (f) displacement of the unit when force was applied.

  • Figure 6

    (Color online) Simulation results. (a) Strains and displacements of the deformation model before and after the removal of the remnant silicon; (b) the influence of trench width on the displacement of array; (c) the influence of trench width on the approximate radius of array.

  • Figure 7

    (Color online) Photos of the flexible temperature controlling array. (a) Bending to the front side; (b) bending to the back side; (c) rolling the flexible array on a cylinder with a diameter of 5 mm.

  • Table 1   Comparisons of the three fabrication strategies for flexible electronics
    Organic semiconductor-based approach Thin-functional structure transferring approach MEMS-based hybrid fabrication/integration approach
    Materials Organic semiconductor Ultrathin inorganic materials, PDMS Silicon/parylene
    Fabrication Printing and surface modification Microfabrication and transferring assembly methods MEMS
    Advantages Intrinsically flexible High performance (mobility of silicon: 710 cm$^2$V$^{-1}$s$^{-1}$ [16]) High and complex performance
    Relatively high stretchability (fracture strain of 800% [11]) Good flexibility (radius ofłinebreak 0.5 mm [17]) Compatible with mass production
    Limitation Limited performance and function (low mobility, recent report of record: 1.32 cm$^2$V$^{-1}$s$^{-1}$ [12]) Limited functionality and reliability due to the ultrathin structure Limited flexibility /stretchability
  • Table 2   Geometrical parameters of different parylene-filled trenches and the thermal isolation efficiency
    Width of the Depth of the Width between two Thermal isolation
    trench ($\mu$m) trench ($\mu$m) units ($\mu$m)efficiency (%)
    Control 3
    Sample 1 2 100 150 69.7
    Sample 2 4 100 150 70.8
    Sample 3 7 50 100 72.5