Papers by Keyword: Generation Lifetime

Abstract: This paper presents the defect distribution and yield analysis on silicon wafer. The generation and recombination lifetime were the key parameters and obtained from the currentvoltage and the capacitancevoltage of diode characteristics for forward bias. Then 3D contour maps were plotted as defect distribution and can be analyzed for the whole wafer which is useful for the yield analysis of the defects that were caused from fabrication process.

Abstract: This paper is proposed to extract the local carrier generation lifetime from forward current-voltage (I-V) characteristics of p-n junctions in case of non-uniform defects. The different geometry p-n junctions have been fabricated by a standard CMOS technology. The forward I-V and high frequency capacitance-voltage (C-V) characteristics of p-n junctions have been measured. The recombination current density can be extracted from the area forward current density by subtracting with the area diffusion current density. Form the recombination current density, the local generation and recombination lifetime can be obtained.

Abstract: An effect induced by x-ray irradiation on Boron-doped crystalline Si at room temperature was closely investigated in this paper. Irradiation of X-ray energy of 40, 55 and 70keV has been performed on P-N junction diodes fabricated at Thai Microelectronics Center. Minority carrier life time of the device has been calculated before and after irradiation for comparison. The results show no significant change on the value between exposed and unexposed device. Therefore, any permanent lattice modified or any defects caused by X-ray in the device bulk seem to be unconfirmed in this range of energy. However, from this study, X-ray irradiation still effects on electrical characteristics of the diodes. Current-voltage (I-V) measurement has been carried out to study characteristic variation of the device. Biasing of the device was performed from -10 to 1 V and, after the exposure, the leakage current was obviously decreased by 25% and forward current was dramatically increased by 3 order of magnitude related to increment of X-ray energy.

Abstract: The pulsed MOS-C (Metal Oxide Semiconductor-Capacitor) technique was used to measure generation lifetimes in 4H-SiC epitaxial wafers. The ratio of generation to recombination lifetime has been investigated to understand the dominant defect for generation lifetime. The EH6/7 defect level is considered to limit generation lifetime and field enhanced emission is proposed to explain extremely large variation of generation lifetime in a small area. Generation lifetime is limited by dislocations when they are above a threshold density of about 106cm-2. Generation lifetimes measured on 4 and 8 degree off-cut angle epi-substrates are very comparable.

Abstract: Compared to silicon, there have been relatively few comparative studies of recombination and carrier lifetimes in SiC. For the first time, both generation and recombination carrier lifetimes are reported from the same areas in 20 m thick 4H SiC n-/n+ epi-wafer structures. The ratio of the generation to recombination lifetime is much different in SiC compared to Si. Activation energy calculated from SiC generation lifetimes shows that traps with energy levels near mid-gap dominate the generation lifetime. Comparison of both generation and recombination lifetimes and dislocation counts measured in the device area show no correlation in either case.

Abstract: This paper aims at reviewing the possibilities of using p-n junction diodes for lifetime and defect analysis in semiconductor materials. In a first part, the theoretical basis of lifetime extraction based on p-n junction current-voltage and capacitance-voltage characteristics will be discussed. In the next parts, these methods will be applied to different cases relevant for advanced semiconductor materials and device processing. First, the impact of the initial interstitial oxygen content and thermal pre-treatment of Czochralski silicon substrates on the carrier generation and recombination lifetime is discussed. A comparison will also be made with epitaxial and Float-Zone silicon. In a next part, the impact of proton-irradiation damage on the diode behavior will be presented. In the final part, the application of the technique on SiGe and Ge based p-n junctions is described. Whenever possible and useful, the information extracted from p-n junction characteristics will be compared with direct lifetime measurements using microwave techniques. Additional defect information has also been gained from other well-known techniques like Deep- Level Transient Spectroscopy (DLTS), Electron-Beam-Induced Current (EBIC), etc and will be correlated with the p-n junction results. The review is wrapped up in a summary followed by an outlook on future evolution and requirements.

Abstract: An overview is given of analytical techniques for the characterization of the electrical and transport parameters in thin (<1 µm) semiconductor layers. Some of these methods have been applied to the lifetime and diffusion length study in thin strain-relaxed buffer (SRB) layers of strained silicon (SSi) substrates, while a second group was dedicated to Silicon-on-Insulator (SOI) materials and devices. The employed techniques can be divided into two groups, whether a device structure (junction, MOS capacitor, MOSFET) is required or not. However, the MicroWave Absorption (MWA) technique can be used in both cases, making it a versatile tool to study both grown-in and processing-induced electrically active defects. The transport properties of SSi wafers are strongly determined by the density of threading and misfit dislocations, although the dependence of the recombination lifetime is weaker than expected from simple Shockley-Read-Hall (SRH) theory. This is related to the high injection regime typically employed, enabling the characterization of the 250-350 nm thick Si1-xGex layer only. At longer carrier decay times, multiple trapping events dominate that can be described by a stretched exponent approach, typical of disordered materials. For SOI substrates, transistor-based techniques will be demonstrated that enable to assess the generation or recombination lifetime in the thin silicon film (<100 nm). The lifetime can be severely degraded by irradiation or hot-carrier degradation. Finally, it will be shown that Generation-Recombination (GR) noise spectroscopy as a function of temperature allows identifying residual ion-implantation-damage related deep levels, which are otherwise hard to detect even by Deep Level Transient Spectroscopy (DLTS).