The Ni:Si/Ge characteristics and their applications on OEIC

• Main Authors: Elvis Chuan-Yi Lin, 林全益
• Other Authors: Albert Chin
• Format: Others
• Language: en_US
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/88755164751895825056

博士 === 國立交通大學 === 電子工程系 === 91 === In this work, the techniques of room temperature crystallization, advanced silicide, and SiGe/Si MOS tunneling diode have been studied. The first topic was regarding the crystallization. Electron-beam crystallization at room temperature for poly-Si thin-film transistor was applied and discussed. In contrast to the high crystallization temperature and long duration of conventional furnace crystallization, electron-beam crystallization could be performed at a low thermal budget even without substrate heating. It also provides better device characteristics than conventional furnace annealing, including smaller threshold voltage, higher mobility, smaller subthreshold swing, and larger ION/IOFF ratio. The much smoother surface than excimer laser annealed sample is also important for further gate oxide integrity and device performance improvement. The second part discusses the NiSi or CoSi2 characterization and its applications as a gate electrode as well as germano silicide. We have fabricated the fully silicided NiSi on La2O3 for n- and p-MOSFETs. For 900 oC fully silicided CoSi2 on La2O3 gate dielectric with 1.5 nm EOT, the gate dielectric has large leakage current by possible excess Co diffusion at high silicidation temperature. In sharp contrast, very low gate leakage current density of 2×10-4 A/cm2 at 1 V is measured for 400 oC formed fully silicided NiSi and comparable with Al gate. The extracted work function of NiSi was 4.42 eV, and the corresponding threshold voltages are 0.12 and -0.70 V for respective n- and p-MOSFETs. Electron and hole mobilities of 156 and 44 cm2/V-s obtained by n- and p-MOSFETs are comparable with the HfO2 MOSFETs without using H2 annealing. The Ni and Co germano-silicide on Si0.3Ge0.7/Si have also different behavior. The Ni germano-silicide shows a low sheet resistance of 4-6 W/? on both P+N and N+P junctions, which is much smaller than Co germano-silicide. Besides, small junction leakage currents of 3´10-8 A/cm2 and 2´10-7 A/cm2 are obtained for Ni germano-silicide on P+N and N+P junctions, respectively. The good germano-silicide integrity is due to the relatively uniform thickness as observed by cross-sectional TEM. The third part is related to the optical communication realization on single crystalline SiGe/Si substrate. We have compared the electroluminescence of SiO2 tunnel diode, Al2O3 tunnel diode, and Al2O3/ITO superlattice tunnel diode on Si. The electroluminescence intensity of 2.3nm Al2O3 tunnel diode is more than one order of magnitude higher than 2nm SiO2 tunnel diode or 0.18mm MOSFET, while the electroluminescence intensity of 3 periods 20Å-ITO/15Å-Al2O3 superlattice tunnel diode has three orders of magnitude larger than 20Å SiO2 tunnel diode. By Al2O3/Si1-xGex MOS tunnel diodes on Si scheme, we have fabricated SiGe/Si LED with emitting light at around 1.3 mm, for x = 0.7. The emitted photon energy is smaller than the bandgap energy of Si, thus avoiding strong light absorption by the Si substrate. The optical device structure is compatible with that of a MOSFET, since a conventional doped poly-Si gate electrode will be transparent to the emitted light. Increasing the Ge composition from 0.3 to 0.4 only slightly decreases the light emitting efficiency.