High-quality HfSixOy gate dielectrics fabricated by solid phase interface reaction between physical-vapor-deposited metal–Hf and SiO2 underlayer

Abstract

We fabricated high-quality Hf–silicate (HfSixOy) gate dielectrics by utilizing the solid phase interface reaction between physical-vapor-deposited metal–Hf (typically 0.5nm thick) and SiO2 underlayers. Metal diffusion to the SiO2 layer increases the permittivity of the underlayer, while preservation of the initial SiO2∕Si bottom interface ensures good electrical properties of the gate dielectrics. The Hf–silicate layer remains amorphous and the poly-Si∕HfSixOy gate stack endures activation annealing at 1000°C. The interface trap density was comparable to that of conventional SiO2 dielectrics and the hysteresis of capacitance–voltage curves was as low as 4mV for a bias swing between −2 and +2.5V. Moreover, high electron mobility, equal to 89% of the universal mobility, was obtained for the high-k gate transistor.

Dielectric relaxation of high-k oxides

“…Among them are cerium oxide CeO 2 [16-23], cerium zirconate CeZrO 4 [24], gadolinium oxide Gd 2 O 3 [25-27], erbium oxide Er 2 O 3 [28,29], neodymium oxide Nd 2 O 3 [30,31], aluminum oxide Al 2 O 3 [32,33], lanthanum aluminum oxide LaAlO 3 [34,35], lanthanum oxide La 2 O 3 [36], yttrium oxide Y 2 O 3 [37], tantalum pentoxide Ta 2 O 5 [38], titanium dioxide TiO 2 [39], zirconium dioxide ZrO 2 [40,41], lanthanum-doped zirconium oxide La x Zr 1 −x O 2 −δ [42,43], hafnium oxide HfO 2 [44], HfO 2 -based oxides La 2 Hf 2 O 7 [45], Ce x Hf 1-x O 2 [46], hafnium silicate HfSi x O y [47], and rare-earth scandates LaScO 3 [48], GdScO 3 [49], DyScO 3 [50], and SmScO 3 [51]. Among them, HfO 2 , HfO 2 -based materials, ZrO 2 , and ZrO 2 -based materials are considered as the most promising candidates combining high dielectric permittivity and thermal stability with low leakage current due to a reasonably high barrier height that limits electron tunneling.…”

High dielectric constant oxides

“…The SiO will also desorb from a buried layer through a high K oxide covering. The second way is to react the metal such as Hf with the SiO 2 to displace Si [58,59].…”

Fabrication of high-k gate dielectrics using plasma oxidation and subsequent annealing of Hf/SiO<inf>2</inf>/Si structure

“…To solve this problem, high-permittivity (high-k) gate dielectrics are used because they maintain a gate capacitance equivalent to several monolayers of Si0 2 with greater physical thickness, which successfully reduces the J 1eak • Among various high-k materials, Hf-based high-k dielectrics, such as HtD 2 and the Hf silicates (HfSiO or HfSiON), have been intensively studied as promising candidates [1][2][3], and the high-k dielectrics and metal gate electrodes integrated on a Si substrate appeared in the market in late 2007.…”