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. 2013:3:2609.
doi: 10.1038/srep02609.

Can we build a truly high performance computer which is flexible and transparent?

Jhonathan P Rojas  1 , Galo A Torres Sevilla, Muhammad M Hussain
Affiliations

Can we build a truly high performance computer which is flexible and transparent?

Jhonathan P Rojas et al. Sci Rep. 2013.

Abstract

State-of-the art computers need high performance transistors, which consume ultra-low power resulting in longer battery lifetime. Billions of transistors are integrated neatly using matured silicon fabrication process to maintain the performance per cost advantage. In that context, low-cost mono-crystalline bulk silicon (100) based high performance transistors are considered as the heart of today's computers. One limitation is silicon's rigidity and brittleness. Here we show a generic batch process to convert high performance silicon electronics into flexible and semi-transparent one while retaining its performance, process compatibility, integration density and cost. We demonstrate high-k/metal gate stack based p-type metal oxide semiconductor field effect transistors on 4 inch silicon fabric released from bulk silicon (100) wafers with sub-threshold swing of 80 mV dec(-1) and on/off ratio of near 10(4) within 10% device uniformity with a minimum bending radius of 5 mm and an average transmittance of ~7% in the visible spectrum.

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Figures

Figure 1
Figure 1. Fabrication process flow of p-type MOSFET on Si (100) fabric.
Detailed description is in the main text.
Figure 2
Figure 2. Scanning electron microscopy images of representative fabrication steps.
(a) Transistor layout after DRIE process showing hole distribution and depth. (Inset-Channel area zoomed-in). (b) ALD-based Al2O3 spacer after XeF2 etching showing isotropic profile. (c) Released ~15 μm silicon fabric after completed XeF2-based release.
Figure 3
Figure 3. Electrical performance of a representative device on a released fabric (L = 8 μm, W = 5 μm).
(a) ID–VG transfer characteristics in logarithmic scale (Inset-Gate leakage density current). (b) ID–VG transfer characteristics in linear scale. (c) ID–VD curves of same transistor.
Figure 4
Figure 4. Electrical performance comparison of a device before and after release.
(L = 9 μm, W = 5 μm). (a) ID–VG transfer characteristics in logarithmic scale. (b) ID–VG transfer characteristics in linear scale. (c) Gate leakage density current.
Figure 5
Figure 5
(a) Silicon fabric bended at minimum bending radius of 5 mm. (b) Nominal strain dependence on bending radii.
Figure 6
Figure 6. Bendability dependence of electrical properties of the transistor.
(a) Electrical measurement setup of a silicon fabric at 15 mm bending radius. (b) Ion and Ioff behavior under different strain conditions. (c) Vth and S behavior under different strain conditions. (c) Effective mobility versus gate voltage curves for several strain conditions.
Figure 7
Figure 7. Optical characterization.
(a) Silicon fabric with devices (delimited with dashed lines) on top of LED screen showing semi-transparency. (b) Light transmittance versus wavelength in the visible range (Inset-Silicon fabric with devices (delimited with dashed lines) showing diffraction and separation of light into its components as with a diffraction grating).
See this image and copyright information in PMC

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