Schematic illustration of the GaN-based (a) HEMT, (b) MOSHEMT and (c) MOSFET wafers evaluated in this work (after [26]). 59 Table 5.1 The treatments and gate oxide layers of the GaN MOSCAP samples investigated in this work.
III-V materials
Lists electron and hole mobilities, electron and hole effective mass, band gap and permittivity for Si, Ge and typical III-V compound semiconductors. Furthermore, InGaAs is of particular interest for future nFET applications due to its compatibility with conventional Si processing a) Electron mobility of group III-V compound semiconductors.
GaN devices
But at lower temperature (below room temperature 300℃), no significant degradation was observed in either the Schottky contact or the ohmic contact. Charge collection is created during fabrication and is driven by pre-existing defects on the AlGaN surface.
Radiation effects overview
Between oxide and interface traps, the near-interface oxide traps that communicate with the Si are called "interface traps". The voltage shift is the result of both oxide-fall charge Vot and interface-trap charge Vit.
Low-frequency noise theory
Bw is white noise and is usually negligible compared to 1/f noise because the spectral power is independent of frequency. Three types of PSDs are commonly used to evaluate the 1/f performance, namely the drain voltage power spectral density Svd, the drain current power spectral density Sid, and the gate voltage power spectral density Svg.
Overview of dissertation
To migrate the advanced Si 200mm platform, we start by evaluating the gate stack structure and handling in the simple capacitor structure. Devices with shorter gate lengths show greater radiation-induced charge trapping than devices with longer gate lengths, most likely due to the electrostatic effects of charge trapped in the surrounding SiO2 insulation and SiO2 separating oxides /Si3N4 [85], [86].
Device structure and experimental setup
Device fabrication and structure
Magnified perspective highlighting the gate stack and spacer oxides in (a) exterior view and (b) cross-sectional view. 2.2 (a) and (b) provides a zoomed-in perspective highlighting the gate stack and spacer oxides in different views.
Device layout and DUT
The effective channel width is calculated as 2 times the rib height and the rib width. Therefore, the area of the door can be calculated by multiplying the effective width of the channel by the length of the door.
Radiation experimental setup
Equipment from top to bottom is: SR760 FFT Spectrum Analyzer, HP4140B DC Power Supply, ESD Protected Resistor Box (left), Keysight 34461A Digital Multimeter (right), HP3476A Multimeter (left) and SR560 Low Noise Preamplifier (right ). Equipment from top to bottom is: SR760 FFT Spectrum Analyzer, HP4140B DC Power Supply, ESD Protected Resistor Box (left), Keysight 34461A Digital Multimeter (right), HP3476A Multimeter (left) and SR560 Low Noise Preamplifier (right ).
Results and discussion
I-V characteristics
Vth shifts as a function of irradiation dose and annealing time for irradiation, bias only, and bias voltage-matched irradiation conditions for (a) VG = +1 V and (b) VG = -1 V during irradiation for the devices shown in Figs. For the bias-only condition at VG = +1 V, there is a positive Vth shift of about 15 mV. The results that follow are similarly corrected for the small bias-induced shifts that occur on time scales similar to those of the irradiances [9] , [93] .
Gate bias and length dependence
Excessive positive charge trapping occurs during negative bias irradiation as radiation-induced holes are generated in the Al2O3 layer of the dielectric stack (Fig. A similar mechanism most likely leads to enhanced charge trapping in the SiO2/Si3N4 spacers (Fig. 2.2 ) under negative voltage). During positive bias irradiation, radiation-induced electrons generated in the SiO2 are transported to the Si3N4 and captured [93], [97].
Room-temperature 1/f noise results
Svd as a function of frequency for different values of Vd for a device with a gate length of 1.03 m (a) before irradiation and (b) after irradiation. Svd as a function of frequency for different values of Vg - Vth for a device with a gate length of 1.03 m (a) before irradiation and (b) after irradiation. When β < 2, the effective density of boundary traps increases towards the semiconductor conduction band (for electron conduction) or valence band (for hole conduction.
Summary
In the previous chapter, we evaluated the TID response and low-frequency noise at room temperature of the first generation 16nm InGaAs nMOS FinFET. To evaluate the energy distributions of defects that are sources of 1/f noise and to provide insight into the microstructures of noise-inducing defects, the temperature-dependent DC and 1/f noise in the first generation InGaAs FinFET is evaluated in this chapter. Additional noise contributions from defects in the GaAs interlayer are also likely, especially at low temperatures.
DC characteristics from 85K to 400K
The increased thermal generation of carriers in the depletion region is also seen as a consequence of the increased radiation-induced defects, which can act as generation recombination centers. The deterioration of the Vth, ON/OFF ratio, and hysteresis at higher temperatures represents increased interface and boundary drop defects. The hysteresis increases with dose, indicating that the density of slow traps increases with increasing dose; and decreases with temperature due to the increased rate of charge exchange of interface and boundary traps at elevated temperatures.
Temperature dependence 1/f noise
This peak is consistent with the change in the slope of the voltage dependence of the room temperature noise in Fig. This allows comparison of the gate stack and SRB layer defect level with the Fermi level determined by n-channel type InGaAs (approximately as the conduction band edge). Using low-frequency noise measurements and DFT calculations, we demonstrate that O vacancies in HfO2 are primarily responsible for trapping radiation-induced holes in the gate dielectric layers.
Device structure and experimental setup
Device structure and layout
In all cases, the TiN layer serves as the HfO2 contact layer and defines the work function of the gate stack. The InGaAs FinFET wafer layout evaluated in this work is the same as Chapter 2. The effective channel width and gate area are calculated and the results are shown in Table 4.1.
Experimental setup
Results and discussion
- I-V characteristics
- Pure-TID separation
- Hysteresis results
- Gate bias and length dependence
- Comparison of gate stack responses
In Wafer 2, at VG = +1 V, the Vth shift calculated by TID results (black arrow) all come from bias-induced charging (red arrow), leading to negligible radiation-induced shifts. At VG = −1 V, the pure radiation-induced charging (blue arrow) has a smaller shift compared to observed IV curves (black arrow). This leads to the almost complete neutralization of radiation-induced trapped holes in the HfO2 in Wafer.
Summary
5 GATE STACK AND HANDLING COMPASSION OF GAN MOSCAP DEVICES From this chapter, the DC characteristics and 1/f noise performance are evaluated in the GaN-based Metal Oxide Semiconductor Capacitor (MOSCAP), Metal Oxide Semiconductor High Electron Mobility Transistor (MOSHEMT), Metal Oxide Semiconductor Field Effect Transistor (MOSFET) and High Electron Mobility Transistor (HEMT) devices. To investigate the performance of the gate stack, C-V and hysteresis measurements were performed under three conditions: Fresh, Anneal (FGA at 400C for 20 minutes) and Ohmic Anneal (N2 at 565C for 90 seconds) at both room temperature as high temperature (200C). The shifts of step charge density (Dit), dispersion and flat band voltage (Vfb) are extracted at different temperatures and annealing conditions to characterize the gate stack quality and treatment during processing.
To evaluate the performance of the gate assembly under different annealing conditions, all samples were measured under three different conditions: fresh, annealed (FGA at 400 °C for 20 minutes) and ohmic annealing (N2 at 565 °C for 90 seconds) as shown. on picture. To ensure consistency of results, 6 multi-frequency C-V measurement devices and 18 hysteresis measurement devices were measured for each sample condition.
Multi-frequency C-V results
This in (a) fresh condition, and (b) after ohmic annealing for all GaN MOSCAP samples at a temperature of 25˚C and 200˚C. Accumulation dispersion D% at a temperature equal to (a) 25˚C, and (b) 200˚C after fresh, annealing and ohmic annealing conditions for all samples. Flatband voltage Vfb at a temperature equal to (a) 25 ˚C, and (b) 200 ˚C after fresh, annealing and ohmic annealing conditions for all samples.
Hysteresis results
A band diagram representation of the impact of a widely distributed defect band on the hysteresis measured with different Vstart in the case of (a) Si MOS device and (b) InGaAs/Al2O3. In this work, we measure the hysteresis of the GaN capacitor with different Vstart, to analyze the hysteresis of the devices with different gate stacks under different temperatures and annealing conditions. The flatband voltage shift has been used to demonstrate the hysteresis under different starting voltage.
Summary
Therefore, in this work we use Al2O3 as the gate stack and the corresponding treatments were applied during the fabrication of the device. In this work, we focus on the 1/f noise performance on the same GaN RF devices. In this work, we show the detailed method for low-frequency noise measurement setup in the state-of-art GaN RF devices.
Device structure and layout
Schematic illustration of the GaN-based (a) HEMT, (b) MOSHEMT and (c) MOSFET wafers evaluated in this work (after [27]). For the MOSFET, the AlGaN barrier is completed, etched using an atomic layer etching (ALE) process to form a direct interface between the Al2O3 layer and GaN channel. Most of the devices we measured in the gray area are bad because of either low ON/OFF ratio or high leakage.
Experimental setup
DC characteristics
- Power spectral density overview
- Drain current power spectral density (S id )
- Gate voltage power spectral density (S vg )
- Drain voltage power spectral density (S vd )
Discharge current noise power spectral density (SId) for (a) HEMT, (b) MOSHEMT and (c) MOSFET at Vd=0.05V. Gate-voltage noise power spectral density at 10Hz as a function of Vg-Vt at Vd = 0.05 V for MOSHEMT devices with gate lengths ranging from 0.2m to 1m. 6.16 (a) shows the noise-power spectral density of the discharge voltage Svd for MOSHEMT devices with a gate length of 0.2m as a function of frequency at room temperature.
Temperature dependent 1/f noise
The device information and relationships among all wafers evaluated in this work are summarized in Figure. For the III-N devices, Chapters 5 and 6 demonstrate the DC characteristics and 1/f performance in GaN MOSCAP, MOSFETs, MOSHEMT, and HEMT. The device information and relationships among all wafers evaluated in this work are summarized.
Summary of III-V devices
Both the increased charge trapping at negative bias and the enhanced radiation-induced charge trapping in the short channel devices are most likely due to the electrostatic effects of trapped charge in the thick insulating oxides surrounding the transistor [57], [85]. The temperature-dependent noise and the DFT calculation show that O vacancies in the HfO2 are primarily responsible for the radiation-induced hole trapping in the gate dielectric layers. Oxygen vacancies in the Al2O3 layer contribute significantly to increased noise and lower limit stretching.
Summary of III-N devices
Liao et al., “Total-Ionization Dose Effects in Al/SiO2 Bimorph Electrothermal Microscanners,” IEEE Trans. Ren et al., “Total ionizing dose (TID) effects on gate-all-around (GAA) scaled ultrathin channel (NW) nanowire inGaAs MOSFETs,” IEEE Trans. Zhao et al., “Total-Ionization Dose Effects in Modified Gate-Stack InGaAs FinFETs,” IEEE Trans.
