Silicon Surface Damage Research Articles

Surface damage of silicon and copper by pulsed and pulse-periodic action of an Nd : YAG laser

An investigation was made of the damage to the surface of silicon and copper by pulsed and pulse-periodic action of an Nd : YAG laser. Anomalies were found in a probe Ne — He laser beam scattered by the surface of silicon when it was irradiated by a series of Nd : YAG pulses of I < Imelt intensity (I melt is the surface melting threshold). These anomalies were attributed tentatively to the formation of a defect-saturated surface layer.

In situ investigation of silicon surface cleaning and damage by argon electron cyclotron resonance plasmas

An argon electron cyclotron resonance (ECR) plasma process has been optimized to successfully remove oxide films from a silicon surface at elevated temperatures leaving smooth Si surfaces devoid of an amorphized silicon damage layer. Etch rates of over 10 nm/min have been achieved at ion energies below 100 eV. The low ion energy (−50 V dc bias) and high ion fluxes (1×1016 ions/cm2 s) represent a significant improvement from conventional Ar ion sputter cleaning processes. In situ spectroscopic ellipsometry and ex situ atomic force microscopy were used to characterize the surface condition during and after cleaning to establish a 700 °C argon plasma cleaning process for silicon. Real-time single wavelength ellipsometry was used to study the cleaning kinetics, determine the optimal end point, and elucidate a controversy about the level of damage in the argon ECR plasma cleaning process.

Gas Flow Engineering in Rapid Thermal Processing

ABSTRACTGas flow engineering involves gas dynamics optimization for effective ambient change before heating and for homogeneous convective cooling of the wafers during the heating steps. Multiple gas buffle system, dynamical gas handling, low pressure operation, low temperature edge guard ring and independent top and bottom heater bank control are the proper tools for this optimization. Silicon surface or interface damage during inert gas anneal can be avoided by addition of a small amount of oxygen.

The Performance Study of Ion Implanter Based Medium Energy Ion Spectroscopy with Solid State Detector

AbstractMedium-energy ion spectroscopy using a conventional ion implanter has been developed to study the properties of semiconductor subsurface regions. The system is equipped with solid state detector and operaties with He+ ion energy up to 200 keV. We have tested the system performance for various applications, such as, silicon diffusion through a thin Au layer, a low dose, low energy As implantion and damage of silicon surface caused by plasma treatment.

Ellipsometric study of silicon surface damage in electron cyclotron resonance plasma etching using CF4 and SF6

In situ ellipsometry has been used to measure in real time the surface damage introduced during electron cyclotron resonance (ECR) plasma etching of silicon as a function of rf bias to the substrate. CF4 and SF6 plasmas were employed. For all ECR plasma operating conditions, the amount of Si surface damage increases with the rf bias voltage, without an apparent damage threshold. It is shown that the surface damage depends on the ion current to the substrate and the gas, with SF6 plasmas resulting in the least surface damage.

Diffusion profiles of boron implanted into plasma-etched silicon surfaces

The diffusion of low-dose boron implanted into plasma-etched silicon surfaces is studied. The thermally grown oxide film on the silicon surface was plasma-etched in a CHF/sub 3//CO/sub 2/ plasma. The samples were successively implanted and activated with boron and arsenic to form n/sup +/-p-n junctions to obtain a range of surface doping profiles and junction depths. The chemical and electrically active dopant concentrations were measured using secondary ion-mass spectrometry (SIMS) and spreadings resistance profiling (SRP). The silicon surface damage was characterized using transmission electron microscopy (TEM). It was observed that the diffusion profiles of boron were significantly affected when implanted into plasma-etched silicon surfaces. The samples with oxide films etched in a wet chemical etchant provided the control for evaluating the effect of the plasma etching process. These results suggest that the damage created during the plasma etching process may have caused changes in the boron diffusion profiles. >

Silicon surface damage caused by reactive ion etching in fluorocarbon gas mixtures containing hydrogen

For selective etching of SiO2 on silicon, gases or gas mixtures containing hydrogen are often used. Hydrogen from the glow discharge promotes the formation of a thin film polymer layer responsible for the selectivity of the etching process. The reactive ion etch (RIE) process is known to create damage in the silicon substrate. The influence of hydrogen on the damage and deactivation of dopants is investigated in the present work. The distribution of hydrogen in silicon, after different etching and annealing conditions have been studied. The influence of the RIE process on the charge carrier concentration in silicon has been investigated. Various analytical techniques like contact resistivity measurements, four point probe measurements, and Hall measurements have been used to determine the influence of the RIE process on the electrical properties of processed silicon wafers. The hydrogen profile in as-etched and post annealed wafers was determined by the 1H(15N,αγ)12C nuclear reaction. The depth of the deactivated surface layer is discussed in terms of the impinging hydrogen ion energy, i.e., the possibility of H+ ions to pick up an energy equal to the peak-to-peak voltage of the rf signal.

ChemInform Abstract: Analysis and Reduction of Surface Damage in Silicon Following Hydrogen Passivation.

AbstractTreatment of polycrystalline Si with a hydrogen ion beam (Kaufman‐type source) is found to improve the electronic properties, but also to create a certain degree of surface damage which is quantified by near UV reflectivity and RBS measurements.

Analysis and Reduction of Surface Damage in Silicon Following Hydrogen Passivation

The Kaufman ion source used to passivate defects in polycrystalline silicon solar cells also produces surface damage. This damage has been quantified with Rutherford backscattering, and this quantification has allowed for a measure of surface damage using UV reflectivity. The latter is a rapid, easy technique which simplifies the task of assessing the degree of surface damage. The implications of this work for reducing surface recombination and making higher efficiency solar cells using hydrogen passivation are discussed.

Electrical and ellipsometric characterization of the removal of silicon surface damage and contamination resulting from ion beam and plasma processing

The silicon surface damage resulting from low-energy Ar ion beam and plasma bombardment under a variety of bombardment conditions has been measured and compared. Techniques used to characterize the damage and its removal included x-ray photoelectron emission spectroscopy and reflection ellipsometry to determine the type of incorporated impurities and the damage layer depth, respectively; and high-frequency and quasistatic capacitance-voltage measurements of interface trapped and fixed oxide charge to determine the electrical nature of the damage. While the ellipsometrically measured damage could be removed using various described treatments, the electrical damage persisted. Both electrical and optical differences resulting from lattice damage versus impurity-related damage associated with the different dry etching environments could be discerned.

Cross-sectional TEM technique applied to surface damage in silicon

Cross-sectional TEM technique applied to surface damage in silicon

Effect of Ion Bombardment on the Dopant Diffusion During Reactive Ion Etching (RIE) of Dielectric Films Deposited on Silicon

ABSTRACTWe report on the results obtained from a study conducted to understand the effect of reactive ion etching (RIE) of oxide films on the dopant diffusion in ion-implanted silicon. Thermally grown oxide films on silicon were plasma etched in a CHF3/CO2 plasma. The residual silicon surface damage created during plasma etching was removed by employing a low ion-bombardment, two-step surface plasma cleaning process. The samples with oxide films etched in a wet chemical etchant provided the control for evaluating the effect of the RIE process. The samples were implanted with boron and boron was activated under various conditions to form p-n junctions to obtain a range of boron doping profiles and junction depths. Some boron doped samples were implanted with arsenic to form a heavily doped n+ region at the silicon surface. The resulting doping profiles were analysed using spreading resistance profiling (SRP), four-point probe measurements, and secondary ion-mass spectrometry (SIMS) to understand the activation, diffusion, and precipitation of various dopants. Detailed transmission electron microscopy (TEM) analysis was used to study the microstructural effects. It was observed that plasma etching of the oxide films prior to the formation of boron diffused surface regions in silicon resulted in significant changes in boron diffusion. For low boron implant doses, plasma etched silicon surfaces resulted in retarded boron diffusion. For high boron implant doses, plasma etched silicon surfaces lead to enhanced boron diffusion.

Surface damage of single-crystal silicon abraded in ethanol and deionized water

Semiconductor grade, single-crystal silicon wafers of (1 0 0) p-type were abraded by a single-point, slow speed (2.3 cm sec−1) 90° pyramid diamond in ethanol and deionized water. The scratching was carried out in each of the fluids with a load of 0.5 N on the sliding diamond. The scratching produces a groove, the depth of which depends on the number of traverses of the diamond. A measure of the cross-sectional area of the groove was used to determine the abrasion rate in ethanol, which was about 1.3 times that in deionized water. Some of the samples scratched in deionized water were annealed at 1000° C for 1 h and these samples, along with those unannealed and scratched in both fluids, were fractured perpendicular to the scratch in a three-point bend apparatus. The fracture strengths and the mirror distances obtained by scanning electron microscope (SEM) observation were used to deduce tensile residual stresses of 15.6 and 99.0 MN m−2 beneath the grooves formed in deionized water and ethanol, respectively. The SEM investigation also showed that (a) the groove surfaces contained microcracks wedged with wear debris, and (b) dislocations were generated and propagated away from the groove surfaces as a result of annealing. The relatively higher tensile residual stress produced in the presence of ethanol is consistent with the higher wear rate in this fluid.

Effect of low energy Ar+ ion implantation on silicon surface barriers

The electrical characteristics of Schottky diodes fabricated on silicon surfaces subject to low energy (10 keV) Ar + implantation have been studied as a function of Ar + ion dose. Significant changes in electrical characteristics are seen for ion doses as low as 5×10 11 cm -2 , well below the amorphization threshold dose for silicon. In conjunction with the ion energy threshold established earlier for silicon surface damage effects (about 25 eV), these results outline fundamental limits on the effect of ion-assisted dry etching processes on silicon surface barriers.

The Effect of Beam Species and Anneal History on Silicon Surface Damage Induced by Ion Beam Etching

ABSTRACTIon beam etching and reactive ion etching have been shown to significantly damage silicon surfaces. In this investigation, ion beam damage is examined as a function of ion beam type (1 keV Ne+, Ar+, and Kr+) and anneal history (temperatures of 500°, 800°, and 1000°C in ambient gases Ar,dN2, and Ar + H2 ). Damage at 1 keV, as characterized by currentvoltage and ESR measurements, appears to be roughly proportional to the inverse of ion size. Relatively long anneals at high temperatures (1 hr. at 800'-1000°C depending upon ambient) are found to be necessary to restore original surface characteristics.

Surface Damage and Copper Precipitation in Silicon

AbstractMechanical polishing of silicon introduces considerable damage into the surface. Heating in air causes this damage to be annealed both by dislocation movement and by the formation of stacking faults. The dislocations are rearranged in planes parallel to the surface and stacking faults are formed in the slip planes which lie at an angle to the surface. Prolonged heating causes the defects to be removed by the oxide layer.Copper is preferentially precipitated at these defects. The type of precipitation depends on the copper concentration which is determined by the temperature at which the copper is diffused into the silicon: below 1000 °C the precipitates lie along dislocation lines; between 1000 °C and 1150 °C the precipitates lie as discrete particles parallel to {110} planes; at higher temperatures the precipitates are platelets which lie on the surface. Once a precipitate forms it grows preferentially and removes copper from the surrounding region.