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Fast Flexible Transistors with a Nanotrench Structure.

Seo JH, Ling T, Gong S, Zhou W, Ma AL, Guo LJ, Ma Z - Sci Rep (2016)

Bottom Line: On the other hand, recent advances in nanoimprinting lithography (NIL) may enable the fabrication of large-area nanoelectronics, especially flexible RF electronics with finely defined patterns, thereby significantly broadening RF applications.A unique 3-dimensional etched-trench-channel configuration was used to allow for TFT fabrication compatible with flexible substrates.Optimal device parameters were obtained through device simulation to understand the underlying device physics and to enhance device controllability.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA.

ABSTRACT
The simplification of fabrication processes that can define very fine patterns for large-area flexible radio-frequency (RF) applications is very desirable because it is generally very challenging to realize submicron scale patterns on flexible substrates. Conventional nanoscale patterning methods, such as e-beam lithography, cannot be easily applied to such applications. On the other hand, recent advances in nanoimprinting lithography (NIL) may enable the fabrication of large-area nanoelectronics, especially flexible RF electronics with finely defined patterns, thereby significantly broadening RF applications. Here we report a generic strategy for fabricating high-performance flexible Si nanomembrane (NM)-based RF thin-film transistors (TFTs), capable of over 100 GHz operation in theory, with NIL patterned deep-submicron-scale channel lengths. A unique 3-dimensional etched-trench-channel configuration was used to allow for TFT fabrication compatible with flexible substrates. Optimal device parameters were obtained through device simulation to understand the underlying device physics and to enhance device controllability. Experimentally, a record-breaking 38 GHz maximum oscillation frequency fmax value has been successfully demonstrated from TFTs with a 2 μm gate length built with flexible Si NM on plastic substrates.

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Related in: MedlinePlus

Measured (solid lines) and simulated (dashed lines) RF characteristics of the trench TFTs with various trench gaps/channel lengths (Lch).The gate length (Lg) in all TFTs is 2 μm. Current gain (H21) and power gain (Gmax) as a function of the frequency of a Si NM TFT with a (a) 100 nm, (b) 200 nm, and (c) 500 nm wide trench (Lch). (d,e) fT and fmax as a function of gate bias under a fixed drain bias (Vds = 1.5 V) and as a function of drain bias under a fixed gate bias (Vg = 0.6 V for 100 nm and 200 nm TFTs and Vg = 1.2 V for 500 nm TFTs). (f,g) fT and fmax as a function of bending induced external strain. (h) The small-signal equivalent circuit model used for TFT parameters extraction. (i) Image of bending setup for RF measurements.
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f5: Measured (solid lines) and simulated (dashed lines) RF characteristics of the trench TFTs with various trench gaps/channel lengths (Lch).The gate length (Lg) in all TFTs is 2 μm. Current gain (H21) and power gain (Gmax) as a function of the frequency of a Si NM TFT with a (a) 100 nm, (b) 200 nm, and (c) 500 nm wide trench (Lch). (d,e) fT and fmax as a function of gate bias under a fixed drain bias (Vds = 1.5 V) and as a function of drain bias under a fixed gate bias (Vg = 0.6 V for 100 nm and 200 nm TFTs and Vg = 1.2 V for 500 nm TFTs). (f,g) fT and fmax as a function of bending induced external strain. (h) The small-signal equivalent circuit model used for TFT parameters extraction. (i) Image of bending setup for RF measurements.

Mentions: Figure 5(a–c) present current gain (H21) and maximum stable/available gain (MSG/MAG, Gmax) derived from the measured scattering (S-) parameters at a Vds of 1.5 V and a Vg of 0.6 V for TFTs with 100 nm and 200 nm wide trenches, and a Vds of 1.2 V and a Vg of 0.6 V for a TFT with a 500 nm wide trench, respectively. The fT and fmax were measured at 5 GHz and 38 GHz for a TFT with a 100 nm wide trench, 4.9 and 31 GHz for a TFT with a 200 nm wide trench, and 4.2 and 25 GHz for a TFT with a 500 nm wide trench. These results represent the highest speed of flexible TFTs made of Si. Regardless, these numbers do not imply the speed limit of the Si NM nano trench TFTs. As mentioned earlier, deeper etching of the narrower trenches (e.g., for the 100 nm case) will significantly improve the gate controllability of the channel and thus further greatly enhance both the fT and fmax of the TFTs (see Figsure S5 for the speed predications using simulations under optimized dimensions). Figure 5(a–c) show that there was a reasonable agreement between the measured and simulated fT and fmax values for the devices under the actually fabricated dimensions. The RF characteristics were further analyzed by employing a small-signal equivalent circuit model, the ADS2013 (Agilent Technology), to extract each parameter from the measured S-parameters at the bias conditions where the highest frequency responses were measured25 (Fig. 5(h)). The extracted figure-of-merit (FOM) values for various TFTs with different trench widths are summarized in Table 1. The extracted parasitic capacitance value of Cgs + Cgd obtained from the RF analysis was about 23 to 30 fF, which was comparable to that determined from the direct measurements of fT and gm. The fT value of ~5 GHz was extracted using the equation (2) 23,


Fast Flexible Transistors with a Nanotrench Structure.

Seo JH, Ling T, Gong S, Zhou W, Ma AL, Guo LJ, Ma Z - Sci Rep (2016)

Measured (solid lines) and simulated (dashed lines) RF characteristics of the trench TFTs with various trench gaps/channel lengths (Lch).The gate length (Lg) in all TFTs is 2 μm. Current gain (H21) and power gain (Gmax) as a function of the frequency of a Si NM TFT with a (a) 100 nm, (b) 200 nm, and (c) 500 nm wide trench (Lch). (d,e) fT and fmax as a function of gate bias under a fixed drain bias (Vds = 1.5 V) and as a function of drain bias under a fixed gate bias (Vg = 0.6 V for 100 nm and 200 nm TFTs and Vg = 1.2 V for 500 nm TFTs). (f,g) fT and fmax as a function of bending induced external strain. (h) The small-signal equivalent circuit model used for TFT parameters extraction. (i) Image of bending setup for RF measurements.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4837400&req=5

f5: Measured (solid lines) and simulated (dashed lines) RF characteristics of the trench TFTs with various trench gaps/channel lengths (Lch).The gate length (Lg) in all TFTs is 2 μm. Current gain (H21) and power gain (Gmax) as a function of the frequency of a Si NM TFT with a (a) 100 nm, (b) 200 nm, and (c) 500 nm wide trench (Lch). (d,e) fT and fmax as a function of gate bias under a fixed drain bias (Vds = 1.5 V) and as a function of drain bias under a fixed gate bias (Vg = 0.6 V for 100 nm and 200 nm TFTs and Vg = 1.2 V for 500 nm TFTs). (f,g) fT and fmax as a function of bending induced external strain. (h) The small-signal equivalent circuit model used for TFT parameters extraction. (i) Image of bending setup for RF measurements.
Mentions: Figure 5(a–c) present current gain (H21) and maximum stable/available gain (MSG/MAG, Gmax) derived from the measured scattering (S-) parameters at a Vds of 1.5 V and a Vg of 0.6 V for TFTs with 100 nm and 200 nm wide trenches, and a Vds of 1.2 V and a Vg of 0.6 V for a TFT with a 500 nm wide trench, respectively. The fT and fmax were measured at 5 GHz and 38 GHz for a TFT with a 100 nm wide trench, 4.9 and 31 GHz for a TFT with a 200 nm wide trench, and 4.2 and 25 GHz for a TFT with a 500 nm wide trench. These results represent the highest speed of flexible TFTs made of Si. Regardless, these numbers do not imply the speed limit of the Si NM nano trench TFTs. As mentioned earlier, deeper etching of the narrower trenches (e.g., for the 100 nm case) will significantly improve the gate controllability of the channel and thus further greatly enhance both the fT and fmax of the TFTs (see Figsure S5 for the speed predications using simulations under optimized dimensions). Figure 5(a–c) show that there was a reasonable agreement between the measured and simulated fT and fmax values for the devices under the actually fabricated dimensions. The RF characteristics were further analyzed by employing a small-signal equivalent circuit model, the ADS2013 (Agilent Technology), to extract each parameter from the measured S-parameters at the bias conditions where the highest frequency responses were measured25 (Fig. 5(h)). The extracted figure-of-merit (FOM) values for various TFTs with different trench widths are summarized in Table 1. The extracted parasitic capacitance value of Cgs + Cgd obtained from the RF analysis was about 23 to 30 fF, which was comparable to that determined from the direct measurements of fT and gm. The fT value of ~5 GHz was extracted using the equation (2) 23,

Bottom Line: On the other hand, recent advances in nanoimprinting lithography (NIL) may enable the fabrication of large-area nanoelectronics, especially flexible RF electronics with finely defined patterns, thereby significantly broadening RF applications.A unique 3-dimensional etched-trench-channel configuration was used to allow for TFT fabrication compatible with flexible substrates.Optimal device parameters were obtained through device simulation to understand the underlying device physics and to enhance device controllability.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA.

ABSTRACT
The simplification of fabrication processes that can define very fine patterns for large-area flexible radio-frequency (RF) applications is very desirable because it is generally very challenging to realize submicron scale patterns on flexible substrates. Conventional nanoscale patterning methods, such as e-beam lithography, cannot be easily applied to such applications. On the other hand, recent advances in nanoimprinting lithography (NIL) may enable the fabrication of large-area nanoelectronics, especially flexible RF electronics with finely defined patterns, thereby significantly broadening RF applications. Here we report a generic strategy for fabricating high-performance flexible Si nanomembrane (NM)-based RF thin-film transistors (TFTs), capable of over 100 GHz operation in theory, with NIL patterned deep-submicron-scale channel lengths. A unique 3-dimensional etched-trench-channel configuration was used to allow for TFT fabrication compatible with flexible substrates. Optimal device parameters were obtained through device simulation to understand the underlying device physics and to enhance device controllability. Experimentally, a record-breaking 38 GHz maximum oscillation frequency fmax value has been successfully demonstrated from TFTs with a 2 μm gate length built with flexible Si NM on plastic substrates.

No MeSH data available.


Related in: MedlinePlus