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This paper describes an all-digital phase-locked loop (ADPLL) for system-on-glass (SoG) with low-temperature poly-Silicon (LTPS) thin film transistor (TFT). Due to the large variations and mismatches of LTPS TFT, it is very difficult to implement an analog PLL on glass substrate and ADPLL is employed for the timing generation in SoG. The ADPLL is implemented with a 2μm LTPS TFT process technology and consists of 5-bit delay-line time-to-digital converter (TDC), 7-bit digitally controlled oscillator (DCO) and digital integrator. with a 20MHz reference clock, the ADPLL is locked within 36 periods of reference clock and shows 930ps peak-to-peak jitter.

The influence of twin boundaries on the characteristics of single grain-silicon thin film transistors has been analyzed by three-dimensional simulation. The simulations show that the orientation and the location of a twin boundary could affect the field-effect mobility and the leakage current of a device. The field-effect mobility increases with the increase of the angle between the normal direction of the twin boundary and the channel direction. A single twin boundary in contact with the drain can lead to higher leakage current because electron-hole generation is greatly enhanced by the trap states in the twin boundary.

In this paper a series of hydrogenated silicon thin films were prepared by high-pressure radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) using various plasma powers. The influence of plasma power on Raman crystallinity and deposition rate was investigated to study the silane depletion level during the deposition of silicon thin films. Based on these results the status of silane depletion were classified as un-depleted, depleted and over-depleted status. Additionally, the structural and opto-electrical properties were also investigated for those materials deposited under different silane depletion status. The results demonstrated that the μc-Si:H films, which are deposited at depleted status, have good opto-electrical properties and are suitable for application as intrinsic layers in solar cells.

We have developed a P-type 2.2″ QVGA LCD panel with integrated level shifters, shift registers, DC-DC converter, and demultiplexer for mobile application. We also have proposed a novel P-type level shifter to decrease the voltage amplitude of input control signals to fulfill the low power consumption requirement. Besides, we also have integrated a P-type DC-DC converter on the panel to supply the power for the panel. Therefore, the voltage amplitude of control logic signals for our P-type panel can be reduced to 5V, and the IC architecture can be greatly simplified.

We applied a deuterium plasma treatment to the surface of polycrystalline silicon films using PECVD and observed the change with AFM, XRD, ET-IR, and SIMS measurement. A bias temperature stressing (BTS) test was carried out to evaluate the reliability of the thin-film transistors (TFT). TFTs with channel lengths as small as 2 were electrically stressed fer up to 1000 sec at room temperature. From the parameter variation such as s-factor, leakage current and on/off ratio, we suggest that the deuterium plasma treatment suppress the hot carrier effect and improve the stability of TFTs.

Layer-by-layer growth of single-crystalline Si with doping was achieved by a temperature-modulation (TM) method combined with an intermittent supply of Si 2 H 6 and dopant precursor B 2 H 6 for p-type growth on Si(100). B 2 H 6 was introduced at a predetermined timing of supply in several doping modes. This TM Si molecular layer epitaxy enabled the growth of a flat surface with layer-by-layer growth in a self-limiting manner on Si(100) and with an outstanding high carrier concentration of over 5 X 10 20 cm -3 while maintaining selective epitaxy at the maximum temperature of 470°C. Based on the results of doping in several modes of growth, the incorporation mechanism of dopant on the growing surface is discussed with respect to the TM process.

Excimer-laser-induced lateral-crystallization of Si thin-films has been characterized numerically. The effects of the Si film thickness, light intensity profile and thermal properties of the underlayer on grain growth are discussed. The tilted melt-solid interface is essential for large grain growth and the super-cooled Si region in front of the melt-solid is also important for quick start of crystal growth. It was concluded that the gradient method is suitable for large grain growth, since it can satisfy both requirements. Elongating the melt duration using a low specific heat underlayer can effectively delay the nucleation, resulting in ultra-large grain growth. The crystalline growth velocity is fastest at the Si-underlayer interface and thus preventing the heterogeneous nucleation at the interface by, such as, insertion of a low melting-point thin-film, is also effective for realizing large grain growth.

Pulsed-laser-induced microcrystallization and amorphization of Si thin films were investigated by transient reflectance and conductance measurements. It was clarified experimentally that the complete melting of a Si film and subsequent supercooling induces both microcrystallization and amorphization. In the case of the microcrystallization of a 49.1-nm-thick Si film, nucleation among supercooled liquid Si was observed. The nucleation temperature and resulting nucleation rate under the microcrystallization condition were estimated to be 1047 K and 1.67×1025 events/(cm3·s), respectively. On the other hand, no significant nucleation was observed in the case of a laser amorphization of 20.7-nm-thick Si film although the film was melted for the relatively long duration of about 80 ns. Extremely fast quench of liquid Si films seems to suppress nucleation and results in solidification in amorphous phase.

A sputtered silicon thin film deposited on unannealed 1737 glass has been shown to transform to polysilicon at low energy density and below the full-melt threshold. The resulting polysilicon shows promise to enable high-yield manufacturing of highly-integrated, large-area LTPS displays. Materials properties and their implications are presented.

Effect of crystalline defects in metal-induced lateral crystallization (MILC) thin film transistors (TFTs) was studied and a new MILC method was proposed to improve the electrical properties of poly-Si TFTs. Defects at channel, which were formed by Ni in conventional MILC method, could be successfully removed by means of asymmetric Ni-deposition. Since the crystalline defects were removed at the channel, field-effect electron mobility increased by a large value up to 120 cm2/Vs, while the leakage current was reduced. Electrical properties of the TFTs fabricated by the new MILC method were dependent on which side of the channel was deposited with Ni.

Observation of the times involved in one switching cycle and the location of the conducting filament formed suggests a mechanism for switching. It is postulated that joule heating in the sample interior predetermines high conducting (avalanche) paths which in turn lead to RC discharge and filament formation.

We demonstrate, using molecular beam epitaxy and chemical vapour deposition grown silicon thin films, an all-optical modulator for single-mode guided light at 1.32 μm. A control beam of above band-gap light is used to generate electron–hole pairs via inter-band absorption and the resultant lowering of the effective refractive index brings the waveguide to cutoff thus limiting throughput. Near 100% modulation is obtained with less than 150 pJ energies with subnanosecond initiation and recovery times. The operation is stable and is polarization and wavelength independent in a three port geometry suitable for use as a logic gate. To reduce the total energy required to bring the waveguide to cutoff, the effects of using a small, already near cutoff and leaky region at the interaction region is investigated here. Preliminary measurements on a graded index, leaky mode, chemical vapour deposition sample resulted in a reduction by a factor of five or better in drive energy. By keeping the leaky region short, the losses can be kept to negligible values. Results in time resolved imaging of the guided mode are also presented along with the necessary design considerations for performance compatible with presently available communication solid state laser sources.

The optical transmission characteristics of polycrystalline thin films of silicon are reported with a view to fabricating a compact, intensity-modulated, opto-electronic temperature sensor for real-time temperature measurement in industrial environments and inside high-voltage electrical machines.

The latest developments in our understanding of the initial stages of Ni and Co silicide formation are described. Particular attention is given to the composition and structure of the ultrathin silicide layer which forms upon room temperature deposition of Ni or Co on atomically clean Si(111). The role of these as-deposited silicide layers as precursors to the formation of epitaxial NiSi2 and CoSi2 at higher temperature will be discussed in some detail. Finally, our current state of knowledge concerning the geometric and electronic structures of the NiSi2Si(111) and CoSi2Si(111) interfaces will be reviewed.

A new reflectometric method enabling the complete optical analysis of weakly absorbing thin films deposited onto absorbing or non-absorbing substrates is described. The interpretation of the envelopes of the extrema present in the spectral dependence of the reflectance characterizing the film can be performed by means of explicit formulae which allow the spectral dependences of both the optical constants of the film to be determined. The thickness of the film can also be found by an explicit formula. The method is employed for analysing silicon thin films deposited onto glass plates. A comparison of the new method with a similar method using the envelopes in the spectral dependence of the transmittance is performed.

Optical measurements were performed from 0.5 eV to 3 eV in the temperature range 293–973 K on hydrogenated silicon thin films. The thicknesses of the films were chosen to obtain an accurate optical gap Eg and static refractive index n0. For a given sample, opposing variations in Eg and n0 are observed with measurement temperature for both amorphous and polycrystalline states. The observed decrease in these two parameters on crystallization is attributed to an increase in voids and to a variation in structural disorder.

c Ecole Polytechnique Federale de Lausanne (EPFL), 2000 Neuchâtel, Switzerland Abstract Efficient light trapping is essential for silicon thin-film solar cells. Excellent light trapping for silicon thin-film solar cells is achieved with randomly textured superstrates (TCO and/or glass). Due to a continuous and broad variation of occurring structure sizes in such textures, their optical simulation is challenging. In this paper we introduce an approach to establish a methodology for 3D optical simulation of silicon thin-film solar cells on randomly textured superstrates. The approach includes three steps. In a first step a fabricated structure is analysed to identify its typical geometric features. In a second step the single geometrical features are optically simulated using the rigorous coupled wave analysis (RCWA). The third step includes an investigation of how the results of the single features can be combined to describe the optical characteristics of the complete random structure. In this paper we concentrate on the first two steps. We introduce the analysis of an exemplary superstrate structure and investigate the optical properties of the single structure features. Preliminary results of this investigation are shown and a proposition of how to optimise the structure geometry is presented.

We have observed negative resistance behavior in evaporated silicon films at room temperature and at liquid nitrogen temperatures which we believe is due to double injection. This, to our knowledge, is the first reporting of double injection in silicon thin films, as well as the first reporting of an active device prepared from silicon thin films. Sample lengths in previous work have ranged from one hundred to several thousand microns. The films used in our work are 0.4 to 0.6 μ thick.

Interactions of evaporated Ni and Si thin films were investigated by a combination of backseat tering spectrometry and transmission electron microscopy. The presence of amorphous Si has no significant effects on Ni2Si and NiSi formation, but it drastically lowers the formation temperature of NiSi. Experiments with evaporated thin markers established that Ni is the dominant diffusing species in the growth of the three suicides. The stability of NiSi was examined by sequential evaporation of Ni34Si66 and Ni50Si50 thin films both on Si(100) and on evaporated Si substrates. The results showed that NiSi2 grows at the expence of NiSi when the stucture is in contact with evaporated Si, while it dissociates into NiSi and Si when in contact with single crystal Si.

Directed energy sources have been used to recrystallize implanted amorphous layers in bulk single - crystal silicon and to crystallize silicon thin films on insulating amorphous substrates. All investigated forms of beam annealing leave residual electronic defects in and near the recrystallized layer on bulk silicon, with densities in excess of those obtained by conventional furnace annealing. This paper summarizes the general observations that may be drawn from numerous experimental investigations of electronic defects in CW beam - recrystallized bulk silicon and affirms the timeliness of similar comprehensive studies of residual defects in crystallized - silicon thin films.

A set of analytical equations that accurately model the large-signal current-voltage and charge-storage characteristics of the poly-silicon thin film transistor (TFT) have been developed. The model is based on theories of conduction in materials with a bulkdistribution of gap states[l]. The equations are suitable for incorporation into a circuit simulator capable of transient-analysis of circuits, such as SPICE.

This paper summarizes the general observations that may be drawn from numerous studies of electronic defects in transient thermally annealed bulk single – crystal silicon and discusses the emerging subjects of electronic defect evaluation in beam – crystallized silicon thin films and in epitaxially – grown III – V semiconductors.

A general scheme for determining which metal-Si systems undergo solidphase amorphization (SPA) upon rapid thermal annealing is presented and used to investigate Ni-Si, Ti-Si, V-Si, Co-Si and Cr-Si reactions. SPA occurs only in the first three systems. With the glaring exception of Co-Si, the results agree with the thermodynamic predictions of SPA in systems in which the free energy of a glassy phase is significantly lower than the free energy of the separate components. The amorphization may also be influenced by the diffusing species and contamination. Following SPA, the first crystalline compound is determined by nucleation kinetics.

Amorphous and micro-crystalline Si films have been deposited by the hot-wire technique on deeply structured columnar ZnO films. It is found that nearly perfect conformal deposition occurs for amorphous films, similar to what was previously found for rf-plasma deposited films. Micro-crystalline films deposited by the hot wire technique are less conformal since deposition occurs preferentially on protruding features of the substrate, while films deposited by rf-plasma CVD exhibit high conformality.

In this work the microstructure transition width from amorphous to microcrystalline silicon is discussed. It is shown that the width of the transition depends on the input silane concentration level and indirectly on the silane depletion level. The higher the input silane concentration and depletion, the wider the transition. Experimental results are then compared to an analytical model and good agreement is obtained with a semi-empirical approach that takes into account the e®ect of the silane density in the plasma on the electron density.

Doping of boron into Si:H thin films by means of glow-discharge decomposition of SiH4 and B2H6 pre-mixed gas has been studied. Optical and electrical properties of these B-dopen Si:H films have been measured, and crucially discussed in relation to the contents of bonded H and incorporated B atoms in the specimens. A new deposition condition has been presented for obtaining “the p-type” film which has a wide optical gap amounting to 1.79 eV and dark conductivity exceeding 10-1 Ω-1cm-1.