First Demonstration of BEOL Wafer-Scale All-ALD Channel CFETs Using IGZO and Te for Monolithic 3D Integration

Abstract

In this work, we demonstrated for the first time Back-End-Of-Line (BEOL) compatible complementary field-effect transistors (CFETs) with wafer-scale all atomic-layer-deposited (ALD) channels for monolithic 3D integration. A p-type transistor based on Tellurium (Te)/Tellurium oxide (TeO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf>) heterostructure was fabricated on top of an InGaZnO (IGZO) n-type transistor using a common gate structure. An excellent IGZO device performance was achieved with an on-current (I<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</inf>) of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1\text{mA}/\mu\mathrm{m}$</tex> at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{V}_{\mathrm{d}\mathrm{s}}=1$</tex> V in an enhancement-mode operation with a channel thickness <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathrm{T}_{\mathrm{c}\mathrm{h}}$</tex>) of 2 nm. The uniform wafer-scale growth of p-type semiconductor Te was achieved by introducing methanol in ALD process. Transistor arrays were measured on a four-inch wafer, demonstrating good uniformity and yield based on statistical electrical characterization. The ALD CFET-inverters were fabricated and confirmed by cross-sectional scanning transmission electron microscopy (STEM). They exhibit good electrical performance with a high gain of 116.5 V/V and a large noise margin of 2.2V (88%) at V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DD</inf> = 5 V. The thermal budget of the entire ALD-CFET fabrication process is 225°C and BEOL compatible.

Topics & Concepts