T. Y. Hsieh

Photoluminescence and formation mechanism of chemically etched silicon

Room‐temperature photoluminescence (PL) from Si chemically etched (CE) in HF‐HNO3‐based solution has been observed. Scanning electron microscopy reveals that the etched Si has a surface morphology similar to that of luminescent porous Si fabricated by conventional anodization. PL spectra show an order of magnitude smaller luminescent intensity and a shorter wavelength intensity peak for CE Si. A CE Si thickness limitation was observed. The formation of CE Si can be readily explained by a local anodization model.

Intense photoluminescence from laterally anodized porous Si

We have studied photoluminescence (PL) from porous Si anodized laterally along the length of the Si wafer. Broad PL peaks were observed with peak intensities at ∼640 to 720 nm. Strong PL intensity could be observed from 550 to 860 nm. Room‐temperature peak intensities were within an order of magnitude of peak intensities of AlGaAs/GaAs multi‐quantum wells taken at 4.2 K, and total intensities were comparable. A blue shift of peak intensities from ∼680 to 620 nm could be observed after thermal anneal at 500 °C in O2 and subsequent HF dip.

Shallow junction formation by dopant diffusion from in situ doped polycrystalline silicon chemically vapor deposited in a rapid thermal processor

Shallow n+‐p junctions were formed by utilizing an in situ doped thin polycrystalline silicon layer as a diffusion source. The in situ arsenic‐doped polycrystalline silicon films were deposited by rapid thermal processing chemical vapor deposition. The dopant pileup phenomena were observed at both the polycrystalline silicon/silicon interface and at the surface. The dopant concentrations were higher when the deposition temperatures were lower. The observed pileup phenomena at the polycrystalline silicon/silicon interface were temperature dependent and mainly due to the segregation of arsenic at the grain boundary. The dopant distribution was mainly due to the grain boundary diffusion and grain growth mechanisms. Extremely shallow n+‐p junctions were achieved and laterally uniform delineated junctions were observed. The dopant concentration in the Si substrate drops two orders of magnitude in less than 500 A.

Selective deposition of in situ doped polycrystalline silicon by rapid thermal processing chemical vapor deposition

Selective polycrystalline silicon was successfully deposited and in situ doped wih arsenic for the first time by rapid thermal processing chemical vapor deposition (RTPCVD). The growth kinetics of SiH2Cl2/AsH3/H2 gas system have been studied by examining the dependence of growth rate on deposition temperature, volume percentage of SiH2Cl2, and AsH3 mole fraction. Submicron polycrystalline silicon layers with excellent selectivity and precise thickness control have been achieved with proper deposition conditions. The growth rate decreases as doping levels increase, and drastically decreases when the AsH3 mole fraction is higher. In addition, the growth rate is linearly proportional to the SiH2Cl2 flow rate for a fixed AsH3 flow rate.

In situ doping of GedxSi1−x with arsenic by rapid thermal processing chemical vapor deposition

We report the growth of GexSi1−x epitaxial layers in situ doped with arsenic by rapid thermal processing chemical vapor deposition at 800 and 900 °C. Films were grown with activated doping levels of up to 2×1019 cm−3 and dopant transition widths (1019–1015 cm−3) of better than 350 A. Doping was observed to reduce growth rates and significantly improve film quality. Defect densities of the order of 103 cm−2 were achieved with normalized film strains of up to 99%.

Selective epitaxial growth by rapid thermal processing

Rapid thermal processing chemical vapor deposition was employed for selective epitaxial growth of silicon. Defect‐free epitaxial islands were grown into oxide windows with 〈110〉 sidewall orientation on (100) silicon substrates. The effects of growth temperature on the degree of faceting have been studied. The hydrogen prebake temperatures as low as 1000 °C have proven to be sufficient for high quality Si deposition without sidewall oxide undercutting.

GexSi1−x optical directional coupler

We have fabricated and characterized the first GexSi1−x optical directional couplers. These structures were fabricated from GexSi1−x grown by rapid thermal processing chemical vapor deposition. The average attenuation of single, straight waveguide sections was 3.3 dB/cm at a wavelength of 1.52 μm. For the directional couplers, the coupling coefficient was 3.9 cm−1 for a waveguide separation of 1.5 μm.

Fluorinated thin SiO2 grown by rapid thermal processing

High quality ultrathin fluorinated gate oxides have been grown for the first time by rapid thermal processing in diluted NF3 and O2. The chemical and electrical properties of fluorinated oxides have been studied as a function of growth conditions.

Dopant-enhanced low-temperature epitaxial growth of in situ doped silicon by rapid thermal processing chemical vapor deposition

We have demonstrated, for the first time, that the epitaxial growth temperature can be lowered by dopant incorporation using rapid thermal processing chemical vapor deposition. Heavily arsenic‐doped epitaxial layers with very abrupt dopant transition profiles and relatively uniform carrier distributions have been achieved at 800 °C. In addition, it is found that defect formation is closely related to dopant concentration.

Selective epitaxial growth with oxide‐polycrystalline silicon‐oxide masks by rapid thermal processing chemical vapor deposition

We have used rapid thermal processing chemical vapor deposition for Si selective epitaxial growth using a mask consisting of a sandwich structure of SiO2 on doped polycrystalline Si on SiO2. Lateral polycrystalline Si growth from the sidewalls of the polycrystalline Si layer was also observed and resulted in polycrystalline ‘‘bumps’’ along the mask sidewalls. Otherwise, the epitaxial Si layer was defect‐free.