Electrical Properties of Poly-Si/ALD Hf-Silicate Gate Stacks with Various Controlled Hf/(Hf + Si) Composition Ratios Fabricated Using Hf[N(CH_3)(C_2H_5)]_4 and SiH[N(CH_3)_2]_3 Precursors

摘要

We studied the electrical properties of polysilicon/hafnium (Hf)-silicate gate stacks with various controlled Hf/(Hf + Si) compositions, which were fabricated by atomic layer deposition (ALD) using Hf[N(CH_3)(C_2H_5)]_4 and SiH[N(CH_3)_2]_3 precursors. The flatband voltages (V_(FB)) of p-metal oxide semiconductor field effect transistors (MOSFETs) were improved by reducing the Hf/(Hf + Si) composition ratio; the value of V_(FB) was improved to about 0.62 V for Hf-silicate gate stacks in which Hf/(Hf + Si) = 23 percent. The subthreshold swings were dependent on the Hf content in the p-MOSFETs, and were 92, 96, and 102 mV/decade for Hf/(Hf + Si) compositions of 23, 44, and 74 percent, respectively. For Hf-silicate gate stacks in which Hf/(Hf + Si) = 44 percent, the values were less than 60 mu A/mu m and the I_(on) values at |Vdd| = 1.1 V were greater than 350 and 150 mu A/pim for n- and p-MOSFETs, respectively. The leakage current densities of the Hf-silicate gate stacks were reduced by more than three orders of magnitude with respect to SiO7 reference films.