Annealing effects on the interface and insulator properties of plasma-deposited Al/SiO_xN_yH_z/Si devices

Abstract

We have studied and compared the effects of conventional annealing in a forming gas atmosphere (430 • C, 20 min) and rapid thermal annealing (RTA) in an inert Ar atmosphere (400-1000 • C, 30 s) on Al/SiO x N y H z /Si devices. The samples were deposited by the electron cyclotron resonance plasma method at low temperature (T = 200 • C). The devices were characterized by surface photovoltage measurements before applying contacts and by capacitance-voltage measurements. All the as-deposited samples containing N had positive flat-band voltage, which corresponds to negative charge in the insulator and/or in the interface states (Q INS). Additionally, trapping of positive charge is observed when measuring from inversion to accumulation after measuring from accumulation to inversion. This behaviour is tentatively attributed to the presence of defects related to N, such as the K centre (N 3 ≡Si ↑) or the N dangling bond (Si 2 =N ↑), which may be present in a negatively charged state. For samples of SiO 2 composition, with a negligible N content, Q INS is positive. High densities of interface states (D it), above 10 12 eV −1 cm −2 , are observed in the as-deposited samples. Both the annealing in a forming gas atmosphere and the RTA result in the change of the sign of Q INS from negative to positive and a decrease of its absolute value, as well as a decrease of D it of about one order of magnitude. The trapping of positive charge is also greatly reduced. These improvements of the electrical properties are attributed to the passivation of defects by H present in the forming gas atmosphere or in the SiO x N y H z film itself in a non-bonded state. For RTA temperatures above 700 • C the properties of the devices degrade due to the release of H. The combination of RTA and annealing in a forming gas atmosphere results in the best properties.

A Review on Resistive Switching in High-k Dielectrics: A Nanoscale Point of View Using Conductive Atomic Force Microscope

“…The addition of some percentage of determined chemical elements in an insulator stack (as N and Si in hafnium-based insulators, leading to HfSiON) is not a new concept, but it has been widely used in the gate oxide engineering of MOSFETs. These dopants can modulate the properties of the insulating stack in the way it is needed [112,113] improving, for example, the instability of the high-k/SiO 2 interface [114,115]. In particular, the addition of Nitrogen has been proved to reduce the penetration of the substrate dopant to the insulator stack [116] and the addition of silicon has been shown to reduce the charge trapping [117].…”

Effect of PECVD SiN x /SiO y N x –Si int

“…[22] However, an increased oxygen content is incorporated into the dielectric layer; thus, 127301-3 the decrease of the Si-H bond density and the increase of the N-H bond density result in forming numerous oxygen-related silicon dangling bonds, such as N≡Si•, N 2 O≡Si•, NO 2 ≡Si•, and O≡Si•. [23] 10 12 10 13 The effect of the deposition temperature on the electrical properties of the interface between the SiO y N x /SiN x stacks and the Si substrate is studied. The D it and Q f of the stacks and the single SiN x layer-coated silicon wafers are summarized in Fig.…”

“…The annealing process affects the hydrogen content in the film [11] and changes the sign of charge in the film, with a negative charge in the film before being annealed and a positive charge after being annealed. [12] However, clarifying how the electrical properties of the interface between the dielectric film and the silicon wafer affect the silicon surface passivation needs in-depth investigation.…”