H. Luan

Performance and reliability of ultra thin CVD HfO/sub 2/ gate dielectrics with dual poly-Si gate electrodes

MOSFETs with high quality ultra thin (EOT/spl sim/10.3 /spl Aring/) HfO/sub 2/ gate stacks and self-aligned dual poly-Si gate are fabricated and characterized. Both n- and p-MOSFETs show good electron and hole mobility, respectively, and excellent sub-threshold swings. In addition, the HfO/sub 2/ gate stack exhibits excellent thermal stability with poly-Si gates up to 1050/spl deg/C/30 s gate activation annealing and shows excellent TDDB reliability characteristics with negligible charge trapping and SILC under high-field stressing.

High quality ultra thin CVD HfO/sub 2/ gate stack with poly-Si gate electrode

We have developed and demonstrated an in-situ rapid thermal CVD (RTCVD) process for the fabrication of high quality ultra thin CVD HfO/sub 2/ gate stack that is compatible with conventional self-aligned poly-Si gate technology. These poly-Si gated HfO/sub 2/ gate stack show excellent interface properties, EOT=10.4 /spl Aring/, and leakage current Jg=0.23 mA/cm/sup 2/ @Vg=-1 V which is several orders of magnitude lower than RTO SiO/sub 2/ with poly-Si gate. In addition, the HfO/sub 2/ gate stack is thermally stable in direct contact with n/sup +/-poly Si gate under typical dopant activation conditions. These films also show excellent reliability under high-field electrical stress. We have also fabricated and demonstrated NMOSFETs, and studied boron penetration in HfO/sub 2/ gate stack with p/sup +/-poly Si gate.

Metal gate work function engineering using AlNx interfacial layers

Metal gate work function enhancement using thin AlNx interfacial layers has been evaluated. It was found that band edge effective work functions (∼5.10eV) can be achieved on hafnium-based high dielectric constant (high-k) materials using the AlNx interfacial layer and TiSiN electrodes. It was also found that the effective work function enhancement by the AlNx interfacial layer increased when the concentration of SiO2 in the gate dielectric was increased. Thus, the enhancement was minimal for HfO2 and maximum for SiO2. A model is proposed to explain these results and a bonding analysis is presented to support the proposed model.

MOS devices with high quality ultra thin CVD ZrO/sub 2/ gate dielectrics and self-aligned TaN and TaN/poly-Si gate electrodes

In this paper, we have successfully fabricated and characterized self-aligned TaN and TaN/poly-Si gated n-MOSFETs with ultra thin (EOT=11 /spl Aring/) CVD ZrO/sub 2/ gate dielectrics. It is show that while both gate stacks show excellent leakage current and good thermal stability after a 900/spl deg/C, 30 s, N/sub 2/ anneal, the TaN/poly-Si ZrO/sub 2/ devices exhibit superior thermal stability even after 1000/spl deg/C, 30 s, N/sub 2/ anneal. In addition, the TaN/poly-Si devices show negligible frequency dependence of CV, charge trapping, and superior TDDB characteristics, compared to TaN devices. Well-behaved N-MOSFETs with both TaN and TaN/poly-Si gate electrodes are demonstrated.

Thermally Stable N-Metal Gate MOSFETs Using La-Incorporated HfSiO Dielectric

We report a thermally stable N-metal process in which surface passivation of HfSiO dielectric using thin layers of La₂O₃, deposited by either MBE or PVD, significantly shifts the metal gate effective work function toward the Si conduction band edge. Well-behaved transistors with L_g down to 70 nm have been fabricated with threshold voltage of 0.25V, mobility up to 92% of the universal SiO₂ mobility, and T_inv ~1.6 nm

Effective work function modification of atomic-layer-deposited-TaN film by capping layer

We demonstrate that the metallic capping layer has a strong impact on the effective work function (EWF) of the metal gate. Specifically, the EWF of atomic-layer-deposited (ALD)-TaN could be increased from 4.5to4.8eV with chemical-vapor-deposited-TiN capping, which is sufficient amount of work function modification for silicon on insulator based devices. A strong interdiffusion of Ti atoms into the ALD-TaN film is observed and correlated well with the changes in the EWF change. Ti capping experiments confirm that the Ti interdiffusion can actually modify the EWF of Ti/ALD-TaN stack.

MOS characteristics of ultra thin rapid thermal CVD ZrO/sub 2/ and Zr silicate gate dielectrics

In this paper, we report MOS characteristics of ultra thin, high quality CVD ZrO/sub 2/ and Zr silicate (Zr/sub 27/Si/sub 10/O/sub 63/) gate dielectrics deposited on Si substrates by in-situ rapid thermal processing. These high-K gate dielectrics show excellent equivalent oxide thickness (EOT) of 8.9 /spl Aring/ (ZrO/sub 2/) and 9.6 /spl Aring/ (Zr/sub 27/Si/sub 10/O/sub 63/) with extremely low leakage current of 20 mA/cm/sup 2/ and 23 mA/cm/sup 2/ @Vg=-1 V, respectively. The thermal stability of ZrO/sub 2//Si as well as the poly-Si/ZrO/sub 2/ interfaces are examined using in-situ XPS. We also investigate the conduction mechanisms and long-term reliability in these gate stacks. In addition, the effects of various gate electrode materials (Al/TiN, poly-SiGe, and poly-Si) on the electrical properties of gate stacks are studied. Finally, we also study the boron diffusion behaviors in p/sup +/-poly-Si PMOS.

On Oxygen Deficiency and Fast Transient Charge-Trapping Effects in High-

This letter correlates fast transient charging (FTC) in high-k gate dielectrics to variations in its oxygen content. Analysis of electrical and physical data suggests that the observed enhancement of FTC may be caused by reduction of the oxygen content in the high-k film due to O scavenging process induced by the HfSix metal electrode. A hypothesis correlating O scavenging from the high-k dielectric to O vacancy formation, which contributes to FTC, is proposed

k

The effective work function (EWF) extracted on terraced oxide structures by capacitance-voltage-based techniques was compared with the work function calculated from the barrier height extracted by current-voltage measurements. The results show a reasonable correlation-within /spl plusmn/ 0.1 eV-in the EWF values for various metal gate electrodes, validating both techniques for EWF extraction.

Dielectrics

It is shown that the work function of Ta1−xAlxNy depends on the electrode and gate dielectric compositions. Specifically, the work function of Ta1−xAlxNy increased with SiO2 content in the gate dielectric, reaching as high as 5.0eV on SiO2; the work function was nearly 400mV smaller on HfO2. In addition, the work function decreased with increasing nitrogen content in the Ta1−xAlxNy metal gate. Increasing Al concentration increased the work function up to about 15% Al, but the work function decreased for higher Al concentrations. Chemical analysis shows that Al–O bonding at the interface correlates with the observed work function values.