A Trench isolation technology has been developed and applied to high-speed bipolar LSI production. In general, the wafer surface after a conventional ploy-Si Chemical-Mechanical-Polishing (CMP) is contaminated with silica particles and chemical impurities. These contaminations produce some unexpected patterns and crystal defects in the wafer surface layer after oxidation. It is difficult to remove them by the conventional cleaning techniques. Therefore, we have established the new post CMP cleaning method, using the electrolytic ionized water containing chemical additive of a small quantity. The anode water has the cleaning effect for the metallic and organic contaminations, and the cathode water has the removing effect for the particles and the etching effect for the poly-Si surface. For this new cleaning process, it is important to avoid the chemical mechanical damages on the surface and to control the surface roughness. Our experimental work has been focused on the large numbers of the remaining particle and the surface roughness using a particle counter and an atomic force microscopy (AFM). We herein report the properties of the electrolytic ionized water and the examined results of poly-Si surface after CMP process. It was found that the electrolytic ionized water is effective for surface control, and the new cleaning process is useful for CMP process.

Erbium (Er) was co-implanted with ( i ) nitrogen (N), ( ii) oxygen (0) and (iii) N and 0 into Al0.7Ga0.3As substrates. Compared with the Al0.7Ga0.3As:Er sample, the 20 K Er3+ -related 1.54 μm integrated photoluminescence (PL) intensity from the Al0 7Ga0.3As:Er,N and Al0.7Ga0.3As:Er,N,O samples were enhanced approximately fifteen and ten times more, respectively. Thermal quenching of Er3+-related emission from Al0.7Ga0.3As:Er,N,O was smaller than that of Er3+-related emission from Al0.7.Ga0.3As-Er,N The 20 K Er3+-related 0.98 μm PL which was radiated by transition from the second excited state (4I1/2) to the ground state (4I1/2) was observed. The 0.98 μm PL intensity from Al0.7Ga0.3As:Er,N,O generally decreased with increasing 0 dosage from 1 × 1013 cm−2 to 1 × 1015 cm−2. These results suggest the formation of different complexes composed of Er and the impurities (N,O). This leads to the generation of complex related traps in the band-gap of Al0.7Ga0.3As as a result of the co-implantation of the impurities. It was found that the trap level of the Er-N complex center lay between 2.05 eV and 1.26 eV, and that of the Er-N-O complex center lay between 1.26 eV and 0.82 eV.

A combined ion beam and molecular beam epitaxy (CIBMBE) method was applied for the deposition of a Ge1−x, Cx, alloy on Si(100) using a low-energy ( 50 – 100 eV ) C+ ion beam and a Ge molecular beam. Metastable Ge1−xCx solid solutions were formed up to x= 0.047, and the CIBMBE method was shown to have a very high potential to grow metastable Ge1−xCx alloys. It was also revealed that the sticking coefficient of C+ ions into Ge was ˜28% for Ei = 100 eV and ˜18% for Ei. = 50 eV. Structural characterization suggests that the deposited films are single crystals grown epitaxially on the substrate with twins on {111} planes. Characterization of lattice dynamics using Raman spectroscopy suggested that the deposited layers have a small amount of ion irradiation damage.

A combined ion beam and molecular beam epitaxy (CIBMBE) method was applied for the deposition of a Ge1-xCx alloy on Si(100) using a low-energy ( 50 – 100 eV ) C+ ion beam and a Ge molecular beam. Metastable Ge1-xCx solid solutions were formed up to x = 0.047, and the CIBMBE method was shown to have a very high potential to grow metastable Ge1-x,Cx alloys. It was also revealed that the sticking coefficient of C+ ions into Ge was ∼28% for Ei, = 100 eV and ∼18% for Ei = 50 eV. Structural characterization suggests that the deposited films are single crystals grown epitaxially on the substrate with twins on {111} planes. Characterization of lattice dynamics using Raman spectroscopy suggested that the deposited layers have a small amount of ion irradiation damage.

Synthesis of metastable group-IV binary alloy semiconductor thin films on Si was achieved by the crystalline growth of Si1-xSnx layers using Sn ion implantation into Si(100) followed either by ion-beam-induced epitaxial crystallization (IBIEC) or solid phase epitaxial growth (SPEG). Si(100) wafers were implanted at room temperature with 110keV 120Sn ions to a dose of 1×1016 cm-2 (x=0.029 at peak concentration) and 2x1016 cm-2 (x=0.058 at peak concentration). By this process about 90nm-thick amorphous Si1-xSnx and about 30nm-thick deeper amorphous Si layers were formed. IBIEC experiments performed with 400keV Ar ions at 300–400°C have induced an epitaxial crystallization of the amorphous alloy layers up to the surface and lattice site occupation of Sn atoms for samples with the lower Sn concentration (LC). XRD analyses have revealed a partial strain compensation for the crystallized layer. Samples with the higher Sn concentration (HC) have shown an epitaxial crystallization accompanied by defects around the peak Sn concentration. SPEG experiments up to 750°C for LC samples have shown an epitaxial crystallization of the fully strained alloy layer, whereas those for HC samples up to 750°C have revealed a collapse of the epitaxial growth around the interface of the alloy layer and the Si substrate. Photoluminescence (PL) emission from both IBIEC-grown and SPEG-grown samples with the lower Sn concentration has shown similar peaks to those by ion-implanted and annealed Si samples with intense I1 or I1-related (Ar) peaks. Present results suggest that IBIEC has a feature for the non-thermal equilibrium fabrication of Si-Sn alloy semiconductors.

We report on the synthesis of β-FeSi2 bulk materials using Horizontal Gradient Freeze (HGF) method. Chunk and powder FeSi2 or high-purity Fe (4N) and Si (9N) were used as starting materials. Three values (1:2, 2:5 and 1:3) of the Fe:Si ratio were selected in the very narrow α and β ranges of the equilibrium phase diagram. Samples were melted between 1300°C and 1500°C in high purity graphite crucibles covered with boron nitride. After cooling, the samples were kept at 800°C and 900°C during 66 to 100 hours, leading to transformation from α to β phase. Cooling rate and annealing time were taken as the two main parameters to optimize the growth conditions. Principal structural characterization was made by X-ray diffraction (XRD). Correlation with stoichiometry was achieved using the results of Rutherford Backscattering Spectroscopy (RBS) and Electron Probe X-Ray Micro Analysis (EPXMA). The samples obtained from 1:2 ratio exhibited mainly β phase while the 2:5 ratio specimens revealed almost α phase structure. The samples prepared with 1:3 ratio was found as a mixture of α and β phases under Si-rich conditions.

Epitaxial layers of Si1-x-yGexCy on Si(100) (x=0.13 and y=0.014 at peak concentration) were formed by ion implantation of Ge ions and C ions at room temperature (RT) and by subsequent IBIEC (ion-beam-induced epitaxial crystallization) process with 400keV Ge and ar ions at 300-400°C and SPEG (solid phase epitaxial growth) process up to 840°C. Crystallization up to the surface both by IBIEC and SPEG processes has been confirmed with RBS-channeling analysis. X-ray diffraction experiments have demonstrated strain compensation by incorporation of C atoms for IBIEC-grown Si1-x-yGexCy/Si samples, whereas strain accommodation due to C precipitation has been observed for SPEG-grown Si1-x-yGexCy/Si samples. Photoluminescence (PL) observed at 2K from IBIEC-grown samples has shown intense I1 peak with/without I1 related (Ar) peak and that from SPEG-grown samples has shown G line emission. these optical properties could suggest that small vacancy agglomeration is dominant in IBIEC-grown samples and C agglomeration is dominant in SPEG-grown samples, respectively.

Carbon ion (C+) irradiation during molecular beam epitaxy (MBE) growth of GaAs/GaAs and in0.53.Ga0.47As/InP layers was carried out using CIBMBE (combined ion beam and molecular beam epitaxy) method as a function of wide acceleration energy (Ea=30 eV-30 keV) at a constant ion beam current density. Judging from the monitored current density and the net hole concentration (INA-ND|) obtained from Hall effect measurements, activation rate as high as 88% was achieved for as-grown GaAs layers by C+ ion irradiation of Ea=~170eV. It was revealed that by annealing at 800°C, a slight enhancement (~ 10%) of INA-ND| is practiced for Ea <~ 130eV but a significant increase of INA-ND| is realized for Ea>~lkeV. IN in0.53Ga0.47As/InP layers with increasing Ea, a type conversion of electric conduction from n to p was found to occur at Ea= ~70~100eV. these observations describe that Ea plays a vital role to determine the location of incorporated electrical and optical active impurities in GaAs and inGaAs. Further for comparison, C+-implanted GaAs layers were prepared by high-energy (400 keV) ion-implantation as a function of substrate temperature (T1=RT-600 °C). For C dose concentration of lxl018cm-3\ the highest activation rate of ~20 % was obtained at T1=~150 °C. This result states that CIBMBE method is a superior doping method in view of activation rate of introduced dopants and the formation of damage-free ion-irradiated layers.

We have developed successfully the combined ion beam and molecular beam epitaxy (CIBMBE) system with a newly designed Knudsen cell for Si effusion. The CIBMBE system was applied to the epitaxial growth of Sil., Cx alloy thin films on Si using low-energy ( 100 – 300 eV ) C+ ion beam. Preliminary results on the characterization of the deposited films suggest high potential and reliability of the new Knudsen cell for Si effusion, as well as high ability of the CIBMBE method to produce thermally non-equilibrium materials. In addition, they indicate that the value of x decreases with increasing IC, which suggests that the selective sputtering for deposited C atoms by incident C+ ion beams takes place during CIBMBE processing. Precipitates of β-SiC were also found to be formed in the deposited films, whose amount was observed to increase with increasing IC.

For the evaluation of an implanted layer, photoluminescence (PL) and photoluminescence excitation (PLE) measurements, which are nondestructive and sensitive methods for identifying impurities and defects, were performed. Yb3+ -related sharp luminescence was observed at a wavelength of 1002nm, due to the transitions which occurred between the spin-orbit levels 2F5/2→2F7/2 of Yb3+ (4f13). Most efficient luminescence of Yb3+ was achieved at an excitation wavelength of around 880nm. The luminescence intensity of this peak (Yb3+) decreased with an increase in annealing temperature. Since the peak has not been observed for good samples in crystallinity, it may indicate that new, efficient energy transfer processes to rare-earth ions occur through the defect energy level. Especially, for the sample annealed at 600°C, Yb-related luminescence intensity excited by the photon energy below the band gap is about 3 times larger than that of excited by the photon energy above the band gap.

Optical direct and indirect excitation of erbium (Er) ions in silicon substrates was performed in order to investigate the high efficiency of Er3+− related 1.54μm emission (4I13/2→4I15/2) for direct excitation that is not concerned with the indirect band gap and low quantum efficiency of a Si host. The samples were prepared by ion-implantation or thermal diffusion methods. In each sample, photoluminescence (PL) showed the peaks originating from 4I13/2→4I15/2 of Er3+ ions.

In Er thermally diffused samples, optical excitation for energy level 4I11/2 of Er3+ ions was successfully effected by photoluminescence excitation spectroscopy (PLE). The PLE spectra consisted six peaks (963.1nm, 965.0nm, 976.lnm, 978.9nm and 980.9nm) which were caused by direct excitation (4I15/2→4I11/2) of Er3+ ions. The emission directly excited is about 2 times more intense than the indirectly excited emission. The six peaks originating from the splitting of the 4I11/2 levels meant that Er3+ ions were in the sites of noncubic symmetry. The samples prepared by Er ion-implantation did not show the effect.

Optical direct and indirect excitation of erbium (Er) ions in silicon substrates was performed in order to investigate the high efficiency of Er3+− related 1.54µm emission (4I13/2→4I15/2) for direct excitation that is not concerned with the indirect band gap and low quantum efficiency of a Si host. The samples were prepared by ion-implantation or thermal diffusion methods. In each sample, photoluminescence (PL) showed the peaks originating from 4I13/2→4I15/2 of Er3+ ions.

In Er thermally diffused samples, optical excitation for energy level 4I11/2 of Er3+ ions was successfully effected by photoluminescence excitation spectroscopy (PLE). The PLE spectra consisted six peaks (963. lnm, 965.Onm, 976.lnm, 978.9nm and 980.9nm) which were caused by direct excitation (4I15/2→4I11/2) of Er3+ ions. The emission directly excited is about 2 times more intense than the indirectly excited emission. The six peaks originating from the splitting of the 4I11/2 levels meant that Er3+ ions were in the sites of noncubic symmetry. The samples prepared by Er ion-implantation did not show the effect.

Implantation of Mg+ and C+ ions is carried out in bulk InP substrates using single or several energies up to 400 keV. The net carrier concentration profile at 300K is measured by capacitance-voltage (C-V) method. The ground and excited states binding energies of Mg and C acceptors are determined by low-temperature selective excitation of photoluminescence (PL). Additional sharp exciton-Iike emissions are detected after annealing of the samples. Their intensity is found to decrease with increasing Mg+ or C+ dose. Annealing-induced activation and/or formation of complex defect are the likely candidate mechanisms for the involved defect.