Papers by Keyword: Recombination Lifetime

Abstract: We present a new method to potentially map the effective minority charge carrier lifetime by means of a chopped electron beam induced current in a scanning electron microscope using a digital lock-in amplifier. While previous authors have been mainly interested in measuring the diffusion length and some even the minority charge carrier lifetime using line-scans, we show that this method could be extended to measure the lifetime locally in the cross section of a given device. In our case, we use a simple SiC pn-junction. The decrease of current with increasing chopping frequency of the electron beam makes a direct measurement of the effective lifetime possible. Inspired by optical beam induced current (OBIC), this novel approach has great potential to measure the minority charge carrier lifetime locally and is going to help device and process engineers to develop the next generation of SiC power devices.

Abstract: This paper presented the corresponding between the yield equation prediction from Poisson, Murphy with wafer actual yield on the silicon wafer with 0.8 μm CMOS technology. The defect analysis with derivative method, current - voltage and capacitance-voltage of diode characteristic measurement, is used to define the defect in p-n junction on silicon wafer. The different sampling numbers of chips are used to calculate the yield. Finally the calculated data and actual would be compared and found that at sampling number is 25, the tolerance from actual yield is less than 3%.

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: Annealing of high purity semi-insulating (HPSI) 4H-SiC is investigated as a method to improve bulk photoconductive semiconductor switches through recombination lifetime modification. Five samples of HPSI 4H-SiC were annealed at 1810 °C for lengths of time ranging from 3 to 300 minutes. The recombination lifetime of the unannealed and annealed samples was measured using a contactless microwave photoconductivity decay (MPCD) system. The MPCD system consists of a 35 GHz continuous microwave probe and a tripled Nd:YAG pulsed laser. The recombination lifetime was increased from 6 ns, as received, up to 185 ns by annealing for 300 minutes. To experimentally verify switch improvements, identical switches from unannealed and annealed material were fabricated and tested at low voltage. The unannealed device generated a 15 ns pulse with a 2 ns rise-time. The annealed device conducted for upwards of 300 ns with a comparable 2 ns rise-time. The increased recombination lifetime resulted in lower on-state resistance and increased energy transfer.

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: Effective recombination lifetimes of 4H-SiC PiN epitaxy wafers are measured by -PCD (microwave photoconductive decay) system at wafer level. Lifetimes measured in presence and absence of the p+ layer show lower lifetime values with p+ layer present. This is attributed to high recombination rate at p+/n- interface. Lifetimes at various buffer thicknesses show lower values at the buffer layer of about 50 m due to high interface recombination rate resulting from rougher surface of the buffer layer. Lifetimes of PiN wafers from interrupted and continuous p+/n- growth 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: The impact of nickel on minority carrier recombination lifetime has been studied in ptype CZ silicon using SPV and μ-PCD techniques. The results show that small oxide precipitates can be used to improve drastically the detection limit of nickel. This is explained by the decoration of oxide precipitates by nickel, which results in the enhanced recombination activity. In the absence of oxide precipitates or other related bulk microdefects nickel precipitates preferably to wafer surfaces, which does not have such a high impact on the measured recombination lifetime, at least on a low concentration level. Low temperature anneal at 180°C or light illumination of the wafers after nickel in-diffusion did not reveal any further change in lifetime in any of the wafers, which may indicate that nickel precipitates efficiently during air-cooling from high temperature.

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).