Hot carrier stressing is carried out on ultra-thin-film SOI/pMOSFET's under a front gate operation. Degradations of both front and back gate characteristics are estimated. Effects of trapped electron in the front and the back gate oxide on device characteristics are also estimated. In a triode region, it is found that degradation in front gate characteristics is correlated with that in back gate characteristics, although ΔVth(b) is twenty times as large as ΔVth(f), due to difference between the front gate and the buried oxide thickness. In a pentode region, Δβ/β0 in a forward-mode is larger than that in a reverse-mode. This is because of the non-uniformly distributed hot carrier damage along the channel. Based on the charge-coupling theory, damages in the front gate and buried oxide by hot carrier effects are estimated separately. Flat-band-voltage shift in the back gate due to trapped charges in the buried oxide, is obtained from Vth (f) dependence on back gate bias. For Leff=2.0 µm devices, the flat-band-voltage shift varies in the range of 1.00 to 1.50 V. This indicates that trapped electrons are created in the buried oxide. Trapped electrons in the buried oxide increase gm(f) through the effect equivalent to back gate bias. From gm(f) dependence on back gate bias, it is found that effective channel length is decreased by trapped electrons in the front gate oxide near the drain. Therefore, it is worth noticing that, in hot carrier effects in ultra-thin-film SOI/pMOSFET's, gm is increased not only by the reduction of effective channel length but also by the equivalent back gate bias effect.

A study of hot-carrier-induced photon emission in thin SOI/MOSFETs has been carried out both for bonded-SOI and SIMOX/SOI. The photon emission is observed not only in the drain region but also in the source region for SOI/MOSFETs, whereas only in the drain region for conventional bulk MOSFETs. From the emission spectrum, it can be concluded that the emission mechanism of the source region is probably a photon-assisted direct recombination of electrons and holes, while both the recombination and Bremsstrahlung are the possible mechanism for the drain region. The total photo intensity from SOI/MOSFETs increases as the SOI film thickness decreases, showing that strong impact ionization occurs near the drain region for thinner SOI devices. The relation between the lifetime and the photo intensity for SOI/MOSFETs is very similar to that between the lifetime and the substrate current for conventional bulk/MOSFETs, proving that photon emission is a good indicator of the hot carrier degradation in thin SOI/MOSFETs. The lifetime measurement using the photon emission both for SOI and bulk devices indicates that longer lifetime can be expected for thin film SOI/MOSFETs with a reduced drain bias which will be indispensable for future sub-half micron MOSFETs.

Optical and electrical measurements of thin film n-channel SOI-MOSFETs reveal that the exponential tail in photon emission spectra originates from electron-hole recombination. Bremsstrahlung radiation model as a physical mechanism of photon emission was experimentally negated. Negative threshold voltage shift at the initial stage of high field stress is found to be caused by hole trapping in buried oxide. Subsequent turnover characteristics is explained by a competing process between electron trapping in the front gate oxide and hole trapping in the buried oxide. As to the degradation of transconductance, generated surface state as well as trapped holes in the buried oxide which reduce vertical electric field in SOI film are involved in the complicate degradation of transconductance.