Bongki Mheen

1/f noise in Si/sub 0.8/Ge/sub 0.2/ pMOSFETs under Fowler-Nordheim stress

The 1/f noise in Si/sub 0.8/Ge/sub 0.2/ pMOSFETs was found to be lower than in all-silicon (Si) pMOSFETs, before and after Fowler-Nordheim (F-N) stress. The minimum noise in the Si/sub 0.8/Ge/sub 0.2/ pMOSFET occurred at the thinnest unconsumed Si-cap of approximately 2 nm, because of the reduced-oxide trap density (N/sub ot/) near the Fermi level (E/sub F/) in the device. However, all samples in this study, including the Si control and the Si/sub 0.8/Ge/sub 0.2/ pMOSFETs with different unconsumed Si-cap thicknesses of 21-64 /spl Aring/, revealed almost identical relative changes in 1/f noise due to the stress, despite the relatively wide range of initial noise values. This suggests identical relative changes in N/sub ot/ at the E/sub F/ in the devices during F-N stress.

The enhancement of Q factor in RPCVD SiGe varactors by the structural modification of the base-collector junction

We designed two silicon germanium (SiGe) varactors enhanced in Q factor through a structural modification by using a cost-effective SiGe heterostructure bipolar transistor (HBT) process, a conventional reduced-pressure chemical vapor deposition (RPCVD). As a result, the suggested structures showed a superiority in Q factor (160/GHz/pF at 2.5 GHz) to the conventional one (70/GHz/pF), even with neither a change in process nor an additional mask. We attributed the enhancement of Q factor to the structural feature of the varactors and quantitatively analyzed it with a lumped element model.

A low-temperature and high-quality radical-assisted oxidation process utilizing a remote ultraviolet ozone source for high-performance SiGe/Si MOSFETs

By utilizing a remote ultraviolet ozone source, a low-temperature (600–700 °C) radical-assisted oxidation (RAO) process to produce high-quality ultrathin (1.4–3.7 nm) gate oxides was successfully developed for the fabrication of high-performance SiGe/Si metal-oxide-semiconductor field effect transistors (MOSFETs). The oxide grown by this technique showed much improved leakage and breakdown properties, compared with that grown without ozone. The reactive oxygen species in the RAO process seemed to cure the unpaired bonds in oxide networks making them more robust and dense, without an increase in thermal budget. The Si0.8Ge0.2 p-channel MOSFET with a RAO gate oxide exhibited superior device and 1/f noise characteristics to that with a standard higher temperature furnace oxide. This was because of the suppressed Ge-related gate-oxide degradation at the reduced process temperature when the Si-cap layer was thinned to below 2 nm. These suggest that the RAO process is particularly suitable for SiGe/Si MOSFET devices requiring a high-quality and low-temperature oxidation process.

Improved quality and reliability of ultrathin (1.4–2.3 nm) gate oxides by radical-assisted oxidation utilizing a remote ultraviolet ozone source

A low-temperature and high-purity radical-assisted oxidation (RAO) process for the growth of ultrathin (1.4–2.3 nm) gate oxides was successfully developed utilizing a remote ultraviolet ozone source. The metal–oxide–semiconductor transistors with RAO gate oxides showed improved device characteristics and oxide reliability, in comparison with the devices with non-RAO or standard furnace oxides. The RAO process in this study was proven to be an effective technique to make the oxide network robust and dense, without an increase of growth temperature.

Structure dependence of the characteristics of SiGe varactor fabricated by RPCVD

Two high quality on-chip varactors were developed using a SiGe HBT process. The epitaxial layers of the varactor were grown by reduced pressure chemical vapor deposition (RPCVD) and the overall sequence followed a standard silicon process. The new varactors showed higher normalized Q factors (100 and 160 at 2.5 GHz) than that of a conventional SiGe bipolar varactor (70 at 2.5 GHz), although they suffered small variance of capacitance when the Q factor was high and vice versa. More details of measurement and analysis were presented based on the structural characteristics of the varactors.

Analysis of the SNR and sensing ability of different sensor types in a LIDAR system

LIDAR (light distance and ranging) systems use sensors to detect reflected signals. The performance of the sensors significantly affects the specification of the LIDAR system. Especially, the number and size of the sensors determine the FOV (field of view) and resolution of the system, regardless of which sensors are used. The resolution of an array-type sensor normally depends on the number of pixels in the array. In this type of sensor, there are several limitations to increase the number of pixels in an array for higher resolution, specifically complexity, cost, and size limitations. Another type of sensors uses multiple pairs of transmitter and receiver channels. Each channel detects different points with the corresponding directions indicated by the laser points of each channel. In this case, in order to increase the resolution, it is required to increase the number of channels, resulting in bigger sensor head size and deteriorated reliability due to heavy rotating head module containing all the pairs. In this paper, we present a method to overcome these limitations and improve the performance of the LIDAR system. ETRI developed a type of scanning LIDAR system called a STUD (static unitary detector) LIDAR system. It was developed to solve the problems associated with the aforementioned sensors. The STUD LIDAR system can use a variety of sensors without any limitations on the size or number of sensors, unlike other LIDAR systems. Since it provides optimal performance in terms of range and resolution, the detailed analysis was conducted in the STUD LIDAR system by applying different sensor type to have improved sensing performance.

RF performance tradeoffs of SiGe HBT fabricated by reduced pressure chemical vapor deposition

In this paper, we developed high cutoff frequency and low noise SiGe HBT devices using a low-cost high-throughput reduced pressure chemical vapor deposition (RPCVD) process. In addition, RPCVD can alleviate large thermal variations even on a single wafer, such as occurs in ultra-high vacuum chemical vapor deposition. We also adopted the cheap localized oxidation of silicon (LOCOS) instead of the shallow trench for isolation of terminals to reduce the parasitic from linkage at the RF arena. The cutoff frequency and maximum oscillation frequency of SiGe HBTs with emitter size of 1/spl times/2.5 /spl mu/m/sup 2/ were 48 and 62 GHz, respectively. With the tradeoff of base profile and by adopting a finger-type base structure, the measured minimum noise figure of 1.5 dB and associated gain of 16 dB at 1.5 GHz with collector current of 3.1 mA were also observed in the low noise device. Limitation of noise performance related with this process was also discussed.