Kiyoteru Hayama

Degradation of Si/sub 1-x/Ge/sub x/ epitaxial heterojunction bipolar transistors by 1-MeV fast neutrons

Irradiation damage in n/sup +/-Si/p/sup +/-Si/sub 1-x/Ge/sub x//n-Si epitaxial heterojunction bipolar transistors (HBTs) by 1-MeV fast neutrons is studied as a function of fluence and germanium content for the first time. The degradation of the electrical performance of HBTs by irradiation increases with increasing fluence, while it decreases with increasing germanium content. The induced lattice defects in the base and the collector regions are studied by DLTS methods. In the base region, electron capture levels associated with interstitial boron are induced by irradiation, while two electron capture levels corresponding to the E centers and the divacancy are formed in the collector region. The degradation of device performance is then correlated with simulations of numbers of knock-on atoms. In order to examine the recovery behavior, isochronal thermal annealing is carried out for temperatures ranging from 75 to 300/spl deg/C. Based on the recovery of electrical performance, it is pointed out that the electron capture levels induced in the base and collector regions are mainly responsible for the increase of base current and the decrease of collector current.

Germanium content dependence of radiation damage in strained Si/sub 1-x/Ge/sub x/ epitaxial devices

The irradiation damage in n/sup +/-Si/p/sup +/-Si/sub 1-x/Ge/sub x/ epitaxial diodes and n/sup +/-Si/p/sup +/-Si/sub 1-x/Ge/sub x//n-Si epitaxial heterojunction bipolar transistors (HBTs) by fast neutrons and MeV electrons is studied as a function of fluence and germanium content for the first time. The degradation of the electrical performance of both diodes and HBTs by irradiation increases with increasing fluence, while it decreases with increasing germanium content. The damage coefficient of reverse current for x=0.12 and 0.16 diodes irradiated by neutrons is calculated to be 6.2/spl times/10/sup -21/ and 5.5/spl times/10/sup -21/ n/sup -1/ A cm/sup 2/, respectively. That of h/sub FE/ for electron-irradiated x=0.08, 0.12 and 0.16 HBTs is 7.6/spl times/10/sup -16/, 2.7/spl times/10/sup -16/ and 1.6/spl times/10/sup -16/ s/sup -1/ cm/sup 2/ respectively. >

Impact of 7.5-MeV proton irradiation on front-back gate coupling effect in ultra thin gate oxide FD-SOI n-MOSFETs

The degradation of deep submicron (0.1 /spl mu/m) fully depleted (FD)-silicon-on-insulator (SOI) n-channel metal oxide semiconductor field effect transistors (MOSFETs) subjected to 7.5-MeV proton irradiation is reported. The radiation-induced damage is investigated by studying the static characteristics of devices with different geometries and bias conditions. Special attention is paid to the analysis of the front-back gate coupling effect by changing the back-gate bias V/sub BG/. The change of the front and back channel parameters, the impact of the gate coupling effect and the gate-induced floating body effect are clarified. A correction procedure is proposed for the extraction of the front- and back-interface and oxide trap charge contribution to the threshold voltage shift by accounting for the front-back gate coupling.

Short-channel radiation effect in 60 MeV proton irradiated 0.13 /spl mu/m CMOS transistors

The impact of a 60 MeV proton irradiation on the static characteristics of 0.13 /spl mu/m CMOS transistors is investigated, as a function of the device length and width. It is shown that the degradation of the threshold voltage and of the transconductance exhibits a marked length dependence, with more pronounced changes for shorter devices. From the independence on the device width and the 2 nm gate dielectric (nitrided or reoxidized nitrided oxide), it is concluded that the basic damage mechanism is not related to the isolation or gate dielectric. The origin of the observed changes will be discussed in view of the two-dimensional doping profile, produced by lowly doped drain and pocket or halo implantations used to control the short-channel effects.

Degradation and recovery of In/sub 0.53/Ga/sub 0.47/As photodiodes by 1-MeV fast neutrons

Irradiation damage in In/sub 0.53/Ga/sub 0.47/As p-i-n photodiodes by 1-MeV fast neutrons is studied as a function of fluence for the first time. The degradation of the electrical and optical performance of diodes increases with increasing fluence. The induced lattice defects in the In/sub 0.53/Ga/sub 0.47/As epitaxial layers and the InP substrate are studied by DLTS methods. In the In/sub 0.53/Ga/sub 0.47/As epitaxial layers, hole and electron capture levels are induced by irradiation. The influence of radiation source on device degradation is then discussed by comparison to 1-MeV electrons with respect to the numbers of knock-on atoms and the nonionizing energy loss (NIEL). In order to examine the recovery behavior, isochronal thermal annealing is carried out for temperatures ranging from 75 to 300/spl deg/C. After 300/spl deg/C thermal annealing, the light current only recovers to 20% of pre-irradiation for a fluence of 1/spl times/10/sup 13/ n/cm/sup 2/, while it recovers to 53% for a fluence of 1/spl times/10/sup 15/ e/cm/sup 2/. The different of recovery behavior is thought to be due a different type of radiation damage.

Heteroepitaxial growth of Al2O3 film on Si using dimethylethylamine-alane and O2

Abstract Heteroepitaxial growth of Al 2 O 3 film on Si substrate was carried out by gas-source metalorganic molecular-beam epitaxy using dimethylethylamine-alane (DMEAA) as an aluminum source and O 2 as an oxygen source. The epitaxial temperature decreased from 800 to 700°C compared with that using trimethylaluminum (TMA) as an aluminum source. It was confirmed that the carbon contamination in the Al 2 O 3 film grown with DMEAA was lower than that of TMA at a relatively low temperature of 650°C, although the film crystallinity degraded and the carbon contamination increased with decreasing of growth temperature.

Degradation and recovery of proton irradiated Si/sub 1-x/Ge/sub x/ epitaxial devices

Irradiation damage in n/sup +/-Si/p/sup +/-Si/sub 1-x/Ge/sub x//n-Si epitaxial diodes and heterojunction bipolar transistors (HBTs) by protons is studied as a function of germanium content, proton fluence and energy for the first time. The degradation of the electrical performance of devices increases with increasing fluence, while it decreases with increasing germanium content and energy. The induced lattice defects in the Si/sub 1-x/Ge/sub x/ epitaxial layers and the Si substrate are studied by DLTS methods. In the Si/sub 1-x/Ge/sub x/ epitaxial layers for diodes, electron capture levels associated with interstitial boron complex are induced by irradiation, while two electron capture levels corresponding to the E center and the divacancy are observed in the collector region of the HBTs. The influence of the radiation source on device degradation is then discussed taking into account the number of knock-on atoms and the nonionizing energy loss (NIEL). The radiation source dependence of performance degradation is attributed to the difference of mass and the probability of nuclear collision for the formation of lattice defects. In order to examine the recovery behavior, isochronal thermal annealing is carried out for temperatures ranging from 75 to 300/spl deg/C. Based on the recovery of electrical performance, it is pointed out that the electron capture levels induced in the Si/sub 1-x/Ge/sub x/ epitaxial layers are mainly responsible for the increase of reverse diode current.

Effect of Oxygen Radicals for Epitaxial Growth of Al2O3 on Si

Epitaxial Al 2 O 3 films were grown on Si substrates by metal-organic molecular beam epitaxy (MOMBE) using oxygen radicals excited with remote rf plasma and trimethylaluminum (TMA) as source gases. The epitaxial temperature of AltOs on Si decreased from 800 o C to 700 o C using this method. The growth rate of the AltOs films increased 1.4-1.6 times at excitation rf power of 400 IV, compared with that without rf plasma excitation. The Auger electron spectroscopy (AES) measurement showed that the carbon contamination in the AltOs film was removed by the oxygen radicals during the growth. The flatness of the grown AltOs surface was improved using oxygen radicals

Recovery behaviour resulting from thermal annealing in n-MOSFETs irradiated by 20 MeV protons

The radiation damage of 20 MeV proton irradiated n-MOSFETs fabricated in a BiCMOS process is studied. From the input characteristics of the drain current, the activation energy of the voltage shift based on trapped-oxide charge (ΔVNot) and SiO2/Si interface traps (ΔVNit) for a total ionizing dose of 35 Mrad(Si) is calculated to be 0.40 and 0.26 eV, respectively. Also, the activation energy for the annealing of the density of radiation-induced interface traps (Nit) estimated from the base current of the bipolar mode operation corresponds to 0.27 eV. From the activation energy of the ohmic drain–source current recovery of 0.40 eV it can be concluded that the trapped-oxide charge is mainly responsible for the degradation of the transistor performance.

Effect of irradiation temperature on radiation damage in electron-irradiated MOS FETs

Results are presented of a study of radiation damage by high-temperature electron irradiation in submicron MOS FETs with standard thermal oxide and nitrogen annealed gate oxide as gate dielectric material. n-Channel MOS FETs were irradiated by 2-MeV electrons for the fluence of 1 × 1015 e/cm2 at 30, 100 and 200 °C. The drain leakage current in the cut-off region of MOS FETs increased with irradiation and the increase at 30 °C irradiation was the largest. However, the degradation of maximum transconductance of the MOS FETs tended to increase with increasing irradiation temperature due to the scattering induced by the change in positive trapped charge density and interface state density.