Characteristics and mechanism of tunable work function gate electrodes using a bilayer metal structure on SiO/sub 2/ and HfO/sub 2/

Abstract

In this letter, we investigate a method to adjust the gate work function of an MOS structure by stacking two metals with different work functions. This method can provide work function tunability of approximately 1 eV as the bottom metal layer thickness is increased from 0 to about 10 nm. This behavior is demonstrated with different metal combinations on both SiO 2 and HfO 2 gate dielectrics. We use capacitance-voltage ( -) characteristics to investigate the effect of different annealing conditions and different metal/metal bilayer couples on the work function. By comparing the as-deposited and annealed films, and by comparing with metals that are relatively inert with each other, we deduce that the work function tuning behavior likely involves metal/metal interdiffusion.

TFET-Based Voltage Detector: Proposal and Investigation

“…The gate of the TFET is connected to VDD, forming a "normally-on" structure. Since the tunneling probability of silicon TFETs is low and a relatively high gate work function is applied, the BTBT is weak enough under normal operating voltages (below 1 V) and the leakage current can be controlled [3], [4], [17], [18]. When VDD is high enough, the TFET conducts, the BTBT current flows through R and a detection signal VDetect_TFET is generated.…”

Challenges in Dual Workfunction Metal Gate CMOS Integration

“…3. 20,21 Two metal layers are deposited in the stack, and the top metal layer is etched off from a portion of the wafer. Then, the EWF shift caused by intermixing can be used to differentiate the EWF of the electrodes.…”

Interface engineering through atomic dopants in HfO2-based gate stacks

“…8,9 For high-k based MOSFETs, / ef f of metals has been demonstrated to be strongly dependent on the processing conditions that the device is subjected to. [10][11][12][13][14] It has been reported that / ef f of many metal electrodes shifts toward the middle of the Si band gap upon high temperature annealing, regardless of its vacuum work function. 15 An emerging way to control the relative position of E F (or alternatively, / ef f ) is through the introduction of an interfacial dopant or "capping" layer either at the Si/HfO 2 interface or at the metal/HfO 2 interface.…”