Impacts of Vertically Stacked Monolithic 3D-IC Process on Characteristics of Underlying Thin-Film Transistor

Abstract

In this work, the high-performance junctionless-mode (JL) and low-power inversion-mode (IM) polycrystalline-silicon (poly-Si) thin-film transistors (TFTs) with nanosheet channels (less than 10-nm in thickness) are vertically integrated in monolithic three-dimensional integrated circuit (3D-IC) structure. Both JL and IM TFTs can exhibit high on/off current ratio over 10 7 to demonstrate their performance. The JL TFT has much higher on-state current ~ 24 times than it of the IM TFT. And the IM-TFT has much lower SS ~ 0.104 V/decade and off-current ~ 0.04 times than them of the JL TFT. However, the fabrication of the top-devices (JL TFTs) would degrade the performance of underlying-devices (IM TFTs), resulting in the threshold voltage shift of the IM TFTs from 0.61 to 2.17 V, SS increase from 0.104 to 0.218 V/decade and on-state current degradation from 16 to 3 A. In order to further understand the reasons, the IM TFT with top-device removal process is also fabricated, which exhibits a partial recovery in performance. The results indicate the presence and fabrication process of the top-device would lead to the defect generation in the underlying-device. The results provide a new consideration for monolithic 3D-IC manufacturing technology. Index Terms-Monolithic 3D-IC; nanosheet channel; low power; thin-film transistor.

Optimized method for thermal through silicon via placement with non-uniform heat sources in 3-D-IC

“…With an assumption of vertical and lateral heat transfer of 3D-IC in [12], a numerical model of the equivalent, the anisotropic thermal conductivity was researched. In [13], the effect of TSVs arrangement on transmission performance was analyzed. In [14], a method of reducing the temperature by adding the heat sink to the TTSV in 3D-IC was proposed.…”

Exploring Performance and Reliability Behavior of Nanosheet Channel Thin-Film Transistors under Independent Dual Gate Bias Operation

“…Polycrystalline-silicon (poly-Si) thin-film transistors (TFTs) have been widely studied for applications in display panels, 1,2 nonvolatile memory, 3,4 and 3D integrated circuits. 5,6 With the evolution of semiconductor processes, miniaturization of the poly-Si TFTs results in severe short-channel effects. [7][8][9] Thinning the channel thickness to form a nanosheet (NSH) structure effectively suppresses shortchannel effects and improves device performance due to enhanced on/off switching ability, 10,11 becoming a development trend of the transistor structure in very-large-scale integrated circuits.…”