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AlGaN/GaN MISHEMTs with AlN gate dielectric grown by thermal ALD technique.

Liu XY, Zhao SX, Zhang LQ, Huang HF, Shi JS, Zhang CM, Lu HL, Wang PF, Zhang DW - Nanoscale Res Lett (2015)

Bottom Line: Recently, AlN plasma-enhanced atomic layer deposition (ALD) passivation technique had been proposed and investigated for suppressing the dynamic on-resistance degradation behavior of high-electron-mobility transistors (HEMTs).In this paper, a novel gate dielectric and passivation technique for GaN-on-Si AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MISHEMTs) is presented.The MISHEMTs with thermal ALD AlN exhibit enhanced on/off ratio, reduced channel sheet resistance, reduction of gate leakage by three orders of magnitude at a bias of 4 V, reduced threshold voltage hysteresis of 60 mV, and suppressed current collapse degradation.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, 220 Han Dan Road, Shanghai, 200433 China.

ABSTRACT
Recently, AlN plasma-enhanced atomic layer deposition (ALD) passivation technique had been proposed and investigated for suppressing the dynamic on-resistance degradation behavior of high-electron-mobility transistors (HEMTs). In this paper, a novel gate dielectric and passivation technique for GaN-on-Si AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MISHEMTs) is presented. This technique features the AlN thin film grown by thermal ALD at 400°C without plasma enhancement. A 10.6-nm AlN thin film was grown upon the surface of the HEMT serving as the gate dielectric under the gate electrode and as the passivation layer in the access region at the same time. The MISHEMTs with thermal ALD AlN exhibit enhanced on/off ratio, reduced channel sheet resistance, reduction of gate leakage by three orders of magnitude at a bias of 4 V, reduced threshold voltage hysteresis of 60 mV, and suppressed current collapse degradation.

No MeSH data available.


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HRTEM cross-sectional view of AlN-MISHEMT.
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Fig2: HRTEM cross-sectional view of AlN-MISHEMT.

Mentions: In order to study the performance enhancement caused by incorporation of thermal ALD AlN through the comparison between the AlN-MISHEMTs and the SGHEMTs, those devices have an identical layout. The fabrication processes are almost the same except the AlN ALD process step before gate metal deposition. The samples are 2 cm × 2 cm square pieces sliced from the same 6-in GaN-on-Si wafer. The AlGaN/GaN heterostructure on the epi-wafer was grown by metalorganic chemical vapor deposition (MOCVD) on a high-resistivity silicon wafer and consists of 2.5-μm carbon-doped GaN buffer layer, 500-nm i-GaN layer, 1-nm AlN interlayer, 23-nm undoped Al0.25Ga0.75N top barrier layer, and 5-nm GaN cap layer. The sheet carrier density of 9.86 × 1012 cm−2, the two-dimensional electron gas (2DEG) mobility of 906 cm2/Vs, and channel sheet resistance of 700 Ω/sq were obtained by Hall measurement. In the first step, the mesas were defined by BCl3-based reactive-ion etching (RIE). Secondly, ohmic contacts were formed by e-beam evaporation and lift-off of Ti/Al/Ni/Au followed by a rapid thermal annealing at 850°C. The specific contact resistivity and contact resistance were 5.71 × 10−5 Ω · cm2 and 2 Ω · mm, respectively, obtained by transmission line measurement (TLM). Due to the variation of ohmic contact in the fabrication process, the specific contact resistivity and contact resistance of the AlN-MISHEMT sample are 1.81 × 10−5 Ω · cm2 and 1.27 Ω · mm, respectively. The AlN-HEMTs have an AlN gate dielectric layer deposited at a growth temperature of 400°C by using a BENEQ TFS 200 ALD reactor (Beneq Oy, Vantaa, Finland). Before AlN deposition, the surface native oxide was removed by dipping the samples in HCl:H2O (1:10) for 60 s. Trimethylaluminum (TMA) and NH3 have been utilized as aluminum and nitrogen sources, respectively. During all growth experiments, the NH3 gas flow rate was 100 sccm, exposure time was 0.9 s, TMA pulse time was 0.2 s, and purge time in between precursor pulses was 9 s. A total of 100-cycle AlN layers were deposited on the samples. The thickness was about 10.6 nm, measured in the TEM picture in Figure 2. The material composition property of the film is measured by XPS and will be published in the following paper. Atomic concentrations of Al, N, O, and C are 46.8%, 43.2%, 7.4%, and 2.6% respectively. The SGHEMTs omit this AlN thermal ALD step. Finally, Ni/Au gate electrodes were formed by e-beam evaporation and lift-off on both HEMTs.Figure 2


AlGaN/GaN MISHEMTs with AlN gate dielectric grown by thermal ALD technique.

Liu XY, Zhao SX, Zhang LQ, Huang HF, Shi JS, Zhang CM, Lu HL, Wang PF, Zhang DW - Nanoscale Res Lett (2015)

HRTEM cross-sectional view of AlN-MISHEMT.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385223&req=5

Fig2: HRTEM cross-sectional view of AlN-MISHEMT.
Mentions: In order to study the performance enhancement caused by incorporation of thermal ALD AlN through the comparison between the AlN-MISHEMTs and the SGHEMTs, those devices have an identical layout. The fabrication processes are almost the same except the AlN ALD process step before gate metal deposition. The samples are 2 cm × 2 cm square pieces sliced from the same 6-in GaN-on-Si wafer. The AlGaN/GaN heterostructure on the epi-wafer was grown by metalorganic chemical vapor deposition (MOCVD) on a high-resistivity silicon wafer and consists of 2.5-μm carbon-doped GaN buffer layer, 500-nm i-GaN layer, 1-nm AlN interlayer, 23-nm undoped Al0.25Ga0.75N top barrier layer, and 5-nm GaN cap layer. The sheet carrier density of 9.86 × 1012 cm−2, the two-dimensional electron gas (2DEG) mobility of 906 cm2/Vs, and channel sheet resistance of 700 Ω/sq were obtained by Hall measurement. In the first step, the mesas were defined by BCl3-based reactive-ion etching (RIE). Secondly, ohmic contacts were formed by e-beam evaporation and lift-off of Ti/Al/Ni/Au followed by a rapid thermal annealing at 850°C. The specific contact resistivity and contact resistance were 5.71 × 10−5 Ω · cm2 and 2 Ω · mm, respectively, obtained by transmission line measurement (TLM). Due to the variation of ohmic contact in the fabrication process, the specific contact resistivity and contact resistance of the AlN-MISHEMT sample are 1.81 × 10−5 Ω · cm2 and 1.27 Ω · mm, respectively. The AlN-HEMTs have an AlN gate dielectric layer deposited at a growth temperature of 400°C by using a BENEQ TFS 200 ALD reactor (Beneq Oy, Vantaa, Finland). Before AlN deposition, the surface native oxide was removed by dipping the samples in HCl:H2O (1:10) for 60 s. Trimethylaluminum (TMA) and NH3 have been utilized as aluminum and nitrogen sources, respectively. During all growth experiments, the NH3 gas flow rate was 100 sccm, exposure time was 0.9 s, TMA pulse time was 0.2 s, and purge time in between precursor pulses was 9 s. A total of 100-cycle AlN layers were deposited on the samples. The thickness was about 10.6 nm, measured in the TEM picture in Figure 2. The material composition property of the film is measured by XPS and will be published in the following paper. Atomic concentrations of Al, N, O, and C are 46.8%, 43.2%, 7.4%, and 2.6% respectively. The SGHEMTs omit this AlN thermal ALD step. Finally, Ni/Au gate electrodes were formed by e-beam evaporation and lift-off on both HEMTs.Figure 2

Bottom Line: Recently, AlN plasma-enhanced atomic layer deposition (ALD) passivation technique had been proposed and investigated for suppressing the dynamic on-resistance degradation behavior of high-electron-mobility transistors (HEMTs).In this paper, a novel gate dielectric and passivation technique for GaN-on-Si AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MISHEMTs) is presented.The MISHEMTs with thermal ALD AlN exhibit enhanced on/off ratio, reduced channel sheet resistance, reduction of gate leakage by three orders of magnitude at a bias of 4 V, reduced threshold voltage hysteresis of 60 mV, and suppressed current collapse degradation.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, 220 Han Dan Road, Shanghai, 200433 China.

ABSTRACT
Recently, AlN plasma-enhanced atomic layer deposition (ALD) passivation technique had been proposed and investigated for suppressing the dynamic on-resistance degradation behavior of high-electron-mobility transistors (HEMTs). In this paper, a novel gate dielectric and passivation technique for GaN-on-Si AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MISHEMTs) is presented. This technique features the AlN thin film grown by thermal ALD at 400°C without plasma enhancement. A 10.6-nm AlN thin film was grown upon the surface of the HEMT serving as the gate dielectric under the gate electrode and as the passivation layer in the access region at the same time. The MISHEMTs with thermal ALD AlN exhibit enhanced on/off ratio, reduced channel sheet resistance, reduction of gate leakage by three orders of magnitude at a bias of 4 V, reduced threshold voltage hysteresis of 60 mV, and suppressed current collapse degradation.

No MeSH data available.


Related in: MedlinePlus