In this paper, we present detailed reverse leakage data on laser annealed diodes which were formed by implanting 1 × 1013 and 1 × 1014 /cm2 B atoms at 20 keV and by implanting 1× 1014 and 1× 1015/cm2 As atoms at 50 keV into Si. The implant is made into bare Si through oxide windows where 1700Å thermal SiO2 is both the implant mask and the diode edge passivation. The thermal controls were annealed at 900°C for the B and 950°C for the As for 30 minutes. Diode reverse leakage curves versus voltage are reported for devices with variable perimeter to area ratios. The results indicate that B diodes can easily be made with characteristics similar to thermally annealed devices with leakage at 1V in the 10−9 A/cm2 range. For As implanted diodes, the results are mixed. For As implants of 1 × 1014 /cm2 the diodes had leakage currents at 3V in the high 10−9 A/cm2 range. At the 1 × 1015/cm 2 level devices with significantly higher leakage values at high reverse bias were obtained. The leakage and sheet resistance are determined in both cases and an optimum is shown as a function of laser power.

Successful annealing of p+ n arrays fabricated by ion-implantation of 11B (50 keV, 1 × 1014 cm-2) into Si (100 has been performed using a broadly rastered, low-resolution (0.25-inch diameter) electron beam. A complete 2" wafer could be uniformly annealed in ≃20 sec with high electrical activation (>75%) and small dopant redistribution (≃450 Å). Annealing resulted In p+n junctions characterized by low reverse current (≃4 nAcm-2 at 5V reverse bias) and higher carrier lifetime (80 μsec) over the entire 2" wafer. Based on the electrical characteristics of the diodes, we estimate that the electron beam anneal was able to remove ion implantation damage and leave an ordered substrate to a depth of 5.5 m below the layer junction.

It is demonstrated that swept-line electron beam (SLEB) annealing can be successfully employed to recrystallize relatively deep (∼0.5 μm) Si-implanted amorphous silicon layers. DLTS and C-V analysis of these layers show significant reductions in concentration of residual defects and magnitude of dopant redistribution effects. For comparison, similar data for furnace annealed material is also presented.

Three modes of beam processing are distinguished, characterised by the heat pulse duration. The suitability of each of these modes as a process step in integrated circuit fabrication is discussed with reference to six criteria for applicability. Some conclusions are made as to the eventual application of each mode of processing.

Bipolar transistors with laser annealed base and emitter, as well as those with furnace annealed base and laser annealed emitter, have been successfully fabricated using Q-switched ruby laser pulse irradiation. The performance of laser asannealed transistors is rather poor. However, it can be improved, to some extent, by relatively low temperature furnace annealing after laser irradiation. DC and RF characteristics of laser annealed transistors are presented in conjunction with laser irradiation effects on the characteristics of conventionally fabricated transistors.

Conditions for the scanning e-beam activation of P and As implanted source and drain junctions in production NMOS Si gate devices have been established. MOS devices with e-beam annealed, As-implanted, source and drain regions have been produced. The transistor parameters are found to be close to those of furnace annealed control devices, but e-beam annealed devices exbibit a smaller short-channel effect.

The use of an antireflection oxide film applicable to laser annealing process has been investigated. The optical properties of the antireflection oxide film are changed by ion implantation although the antireflection characteristics are similar to calculations based on nominal optical constants. Implantation annealing can be achieved at powers lower than predicted by calculations. Using the antireflection(AR) technique, n+-p junction diodes were fabricated. Reverse bias junction leakage is around 10-9 A/cm2 , comparable to those annealed thermally. Short channel MOS devices were also fabricated and indicated much better resistance to the short channel effect than those thermally annealed.

The electrical effects associated with pulsed laser irradiation of thermal oxides of silicon were investigated. Three of the functions performed by thermal oxides are control of field effects, junction passivation and electrical isolation. Representative oxide thicknesses suitable for these applications were studied: ≈ 100 nm; ≈ 500 nm and ≥, 1.0 μm respectively. The oxides were irradiated by a repetitively Q-switched Nd 3+:YAG laser operated at the fundamental frequency. The key laser parameters of energy and power density were varied over a wide range, from no change to the onset of discernible change and irreversible damage. The range of energy densities over which the oxide was not electrically degraded was established for each thickness of the oxide. This range of energy densities is compared to the useful range of energy densities for annealing polysilicon and for activating an implant through an oxide. The electrical data was obtained using a mercury probe and through the analysis of a large number of MOS capacitors formed on the irradiated oxides. Parameters measured include: breakdown voltages, surface state charge densities and flat band voltages.

High-dose ion implantation (1017 ions-cm−2) of C+, N+, and O+ at 50 KeV into silicon followed by pulsed laser annealing at 1.06 μm was studied. Formation of SiC, Si3N4, and SiO2 has been observed and investigated using Transmission Electron Microscopy (TEM) and Differential Fourier-Transform Infrared (FT-IR) Spectroscopy. Furthermore, in N+-implanted and laser-annealed silicon samples, we have observed a cell-like structure which has been identified to be spheroidal polycrystalline silicon formed by the rapid laser irradiation.

A comparative study of solid phase epitaxy (SPE) of deposited and ion-implanted amorphous Si films was conducted with the use of a newly developed laser technique. The effects of interface contaminants and contaminants distributed within a deposited film on the rate of SPE and final crystal quality are reported. In the absence of impurities, deposited Si films crystallize at the same rate as ion-implanted layers and yield epitaxial films with comparable crystal quality. The presence of impurities in deposited films at the interface or distributed within the film can severely retard the SPE growth, causing several deleterious effects which ultimately degrade the film quality. These effects are more severe at high temperatures.

The redistribution of antimony impurity atoms implanted in (111) and (100) substrates was studied as a function of the power density of Q-switched YAG laser radiation (λ = 0.53μm) used to recrystallize 4700Å films of amorphous silicon vapor deposited over blanket and patterned Sb buried layer structures. Results for fully crystallized layers show impurity profiles ranging from a sharp interface displaced outward slightly relative to the as-grown interface, to complete redistribution of antimony into the deposited layer. Studies of patterned buried layer structures indicate that epitaxial crystallization can be achieved on (111) and (100) substrates without serious damage to the surface topography necessary for subsequent mask alignment.

Silicon layers evaporated on crystalline Si have been crystallized by Q-switched Nd:YAG laser irradiation. A strong correlation was observed between the density of a-Si films and the quality of the epitaxial regrowth from the liquid phase. Dense films crystallized epitaxially in a wide range of laser energy densities. Layers with 20% lower density, as determined by spectroscopic ellipsometry, had higher crystallization thresholds and suffered from severe pitting of the surface. Coalescence of the excess void volume into microbubbles, stabilized by gaseous contaminants, is responsible for the surface degradation.

In polycrystalline films on amorphous insulating substrates laser melting changes the grain distribution. Rapid melting and solidification of small diameter spots creates concentric rings of large crystallites. This characteristic pattern is explained by a simple model, based on the kinetics of crystallization.

Research on a new process is described which utilized a laser to achieve controlled crystallization of amorphous Si thinfilms for photovoltaic applications. Amorphous Si films are deposited on suitable substrates using RF sputtering. A laser is used to inoculate these films with crystalline embryos at specific locations. These embryos should then grow in a controlled atmosphere annealing furnace under conditions optimized to maintain the nucleation rate at zero and the transformation rate (from amorphous to crystalline silicon) at a maximum value. The result will be a polycrystalline silicon film with a large grain size to film thickness ratio, where the ultimate grain size will be determined by the laser inoculation spacing.

The basic crystallographic and electronic properties of cw laser recrystallized thin polysilicon films are presented and shown to be suitable for fabrication of MOSFET devices. Devices and simple integrated circuits fabricated to explore the potential of this material have electrical characteristics similar to devices fabricated on single crystal material and offer significant promise for future applications.

CW laser recrystallization has been used to process silicon thin films as an integral step in semiconductor device fabrication. On continuous films of polycrystalline silicon, a silicon-nitride encapsulant is used to control surface morphology during laser recrystallization. For thin films on bulk glass substrates it is necessary to pattern the silicon layer in order to minimize microcracking as well as to control recrystallization. Over single crystal silicon substrates, test devices have been fabricated in silicon islands on dual-dielectric layers. Materials and device evaluation included TEM, current-voltage, capacitance-voltage, and EBIC measurements, and the test devices consisted of p-n junction diodes, MOS capacitors, and MOS field-effect transistors.

Large crystals of silicon were obtained via pulsed laser annealing of thinfilms of fine grain CVD polycrystalline silicon. These films were analyzed using a novel technique that provides rapid feedback of crystallographic and defect information. The technique uses very shallow angle metallurgical sections in conjunction with chemical decoration and scanning electron microscopy and results in excellent depth resolution (<10 nm) across large spatial distances (>100 μm). The technique was used to reveal conversion of very large areas (≈ 1 mm 2) of polysilicon films deposited on silicon into single crystal film, albeit with point defects, without requiring the melt depth to reach the polysilicon/silicon interface. A gradual transition from single crystal to increasingly polycrystalline material was observed going from top to bottom of the initially uniform polycrystalline film depending on the pulse energy used. Polysilicon on top of an oxide layer, on the other hand, transforms into large (≈ 10 μm) single crystals with grain boundaries penetrating the entire polysilicon film thickness. These experimental results shed new light on two very important questions: (1) Is laser annealing entirely an epitaxial process or is it strongly influenced by the thermal properties of the underlying substrate, and (2) Whether substantial regrowth of polysilicon requires equilibrium thermodynamics.

Various characterization techniques are applied to pulsed and cw laser-annealed polysilicon layers deposited on oxide layers. The results are used to compare these techniques as to the type and completeness of information provided, as well as sample preparation requirements and general ease or difficulty of measurement. The techniques employed include scanning electron microscopy (SEM), electron channeling micrographs and selected area channeling patterns (SACP), reflection (high energy) electron diffraction (RHEED), transmission electron microscopy (TEM) and selected area diffraction (SAD), x-ray diffraction, optical techniques and etching techniques.

The importance of controlled lateral heat flow in the growth of single crystal silicon islands on amorphous substrates is demonstrated. In one approach the thermal profile on and around the islands is determined by varying the optical absorption with a variety of thin film structures. In another, beam spot shaping is used. Competitive nucleation is suppressed and continued in-plane epitaxial zone growth is enhanced. In this way we are able to produce single crystal islands 20μm wide and >20μm long. Routine production of such islands would enable new thin film transistor technologies.

Beam processing can be applied to thin, polycrystalline silicon films on amorphous substrates to: a( increase grain size, b( produce single, isolated crystals, and c( to produce oriented single crystals. Specific methods for these tasks are outlined. Crystal growth and heat flow consideration appropriate to each are presented.

Thermally-assisted pulsed-laser annealing has been performed on ion-implanted silicon-on-sapphire(SOS) by irradiating Q-switched(20 nsec) ruby laser light during thermally heating. Raman scattering measurements have been made to estimate the residual strain of the annealed SOS. It was observed that Raman shift of SOS annealed in the temperature range of 400°C to 500°C was very close to that of single crystal silicon and the depolarization factor(the Raman intensity ratio of allowed z(xy)z to forbidden z(xx)z scattering configuration) was infinite, while Raman shift of SOS annealed at room temperature was shifted down to about 5 cm-1 and the depolarization factor was finite. It was found that the residual strain of SOS was relieved by the thermally-assisted pulsed-laser annealing, but the residual strain of SOS annealed at room temperature was inhomogeneous and attained to 7×10−3. The annealing temperature dependences of the residual strains were not explained well with a strictly thermal melting and recrystallization model in conjunction with the thermal expansion difference between silicon and sapphire, and suggested to need a new model.