Abstract
We studied the impact of H2 pressure during post-metallization annealing on the chemical composition of a HfO2/Al2O3 gate stack on a HCl wet-cleaned In0.53Ga0.47As substrate by comparing the forming gas annealing (at atmospheric pressure with a H2 partial pressure of 0.04 bar) and H2 high-pressure annealing (H2-HPA at 30 bar) methods. In addition, the effectiveness of H2-HPA on the passivation of the interface states was compared for both p- and n-type In0.53Ga0.47As substrates. The decomposition of the interface oxide and the subsequent out-diffusion of In and Ga atoms toward the high-k film became more significant with increasing H2 pressure. Moreover, the increase in the H2 pressure significantly improved the capacitance‒voltage characteristics, and its effect was more pronounced on the p-type In0.53Ga0.47As substrate. However, the H2-HPA induced an increase in the leakage current, probably because of the out-diffusion and incorporation of In/Ga atoms within the high-k stack.
Highlights
We studied the impact of H2 pressure during post-metallization annealing on the chemical composition of a HfO2/Al2O3 gate stack on a HCl wet-cleaned In0.53Ga0.47As substrate by comparing the forming gas annealing and H2 high-pressure annealing (H2-HPA at 30 bar) methods
post-metallization annealing (PMA) conditions (FGA at atmospheric pressure using 4% H2 gas balanced with N2 and H2-HPA at 30 bar using 100% H2 gas) were examined using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and angle-resolved X-ray photoelectron spectroscopy (ARXPS), and the results are shown in Figs 1 and 2, respectively
The thinness of the gate dielectric stack and the PMA performed in the absence of a gate metal electrode might yield results different from those of the thicker dielectrics used for electrical characterization, it is believed that a relative comparison would be possible between the samples with different PMA conditions
Summary
We studied the impact of H2 pressure during post-metallization annealing on the chemical composition of a HfO2/Al2O3 gate stack on a HCl wet-cleaned In0.53Ga0.47As substrate by comparing the forming gas annealing (at atmospheric pressure with a H2 partial pressure of 0.04 bar) and H2 high-pressure annealing (H2-HPA at 30 bar) methods. The decomposition of the interface oxide and the subsequent out-diffusion of In and Ga atoms toward the high-k film became more significant with increasing H2 pressure. Since the use of conventional Si-channel MOSFET devices, post-metallization annealing (PMA), termed as forming gas annealing (FGA) and typically performed at 300‒400 °C in a N2 atmosphere mixed with a small amount of H2, has been the most effective method for passivating the interface states (the dangling bonds) located within a Si band gap[4,5,6]. A further reduction in Dit could be achieved for high-k/n-type In1−xGaxAs MOS capacitors using H2 high-pressure annealing (H2-HPA)[10], whose effectiveness has been demonstrated in a high-k/Si system[11,12,13]. Correspondence and requests for materials should be addressed to H.K.
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