Feasibility of multiwavelength Raman spectroscopy was studied as a potentialin-line monitoring technique for grain size distribution in channel poly-Si usedin three dimensional stacked NAND (3D NAND) Flash memory devices. Variouschannel poly-Si materials in 3D-NAND Flash memory devices, converted fromchemical vapor deposition (CVD) grown a-Si, were characterized usingnon-contact, multiwavelength Raman spectroscopy and high resolutioncross-sectional transmission electron microscopy (HRXTEM). The Ramancharacterization results were compared with HRXTEM images. The correlationbetween the grain size distribution characterized by multiwavelength Ramanspectroscopy and “on current” (ION) of 3D NANDFlash memory devices was investigated. Good correlation between these techniqueswas seen. Multiwavelength Raman spectroscopy is very promising as anon-destructive in-line monitoring technique for grain size distribution inchannel poly-Si used in 3D NAND Flash memory devices.

The quality of interface between ultrathin silicon dioxide films and their silicon (Si) wafers was characterized using room-temperature photoluminescence (RTPL) and Raman spectroscopy. Three types of low-temperature (350 °C or room temperature) oxide films on Si grown by different techniques were measured and compared with Si wafers having native oxide and high-temperature thermally grown oxide films. Significant RTPL spectra and intensity variations were measured among low-temperature oxide films. Very strong excitation wave length dependence of RTPL spectra and intensity was observed from the low-temperature oxide films on Si whereas the RTPL spectra and intensity from Si with native oxide and thermally grown oxide films were consistent. Stress in the Si lattice, with different low-temperature oxide layers, showed noticeable differences depending on the oxidation technique used. Key device performance parameters of image sensor devices fabricated using three different low-temperature oxide films showed good correlation with the RTPL and Raman measurement results. The RTPL spectra and Raman shifts are very sensitive to the quality of the oxide/Si interface and can be used as an interface quality monitoring technique.

Boron-doped, single (∼54 nm) or double (∼21 + 54 nm) Si1−xGex layers were epitaxially grown on 300-mm-diameter p−-Si(100) device wafers with 20 nm technology node design features, by ultrahigh vacuum chemical vapor deposition. The Si1−xGex/Si wafers were annealed in the temperature range of 950–1050 °C for 60 s to investigate the effect of annealing on possible changes of Ge content and Si stress near the Si1−xGex/Si interface. High spectral resolution, micro-Raman spectroscopy was used as a nondestructive characterization technique with five excitation wavelengths of 363.8, 441.6, 457.9, 488.0, and 514.5 nm. Ge diffusion and generation of compressive stress at the Si1−xGex/Si interface were measured on all annealed wafers. Ge diffusion and the accumulation of compressive Si stress after annealing showed significantly different behaviors between single- and double-layer Si1−xGex/Si wafers. Raman characterization results were compared with secondary ion mass spectroscopy and high-resolution x-ray diffraction results.

The possibility and suitability of micro-Raman spectroscopy as a noncontact, in-line measurement technique for boron (B) concentration in ultrathin (20~35 nm thick) Si1–xGex layers epitaxially grown on 300 mm diameter p−-Si(100) wafers, by ultrahigh vacuum chemical vapor deposition, was investigated. Raman spectra from Si1–xGex/Si(100) wafers were measured under 363.8, 457.9, 488.0, and 514.5 nm excitation. Strong correlation was found between B content and characteristics of the Si–Si Raman peak from the Si1–xGex films. As B concentration increased from undoped to 9.1 × 1020 atoms/cm3, the Si–Si Raman peak broadened and the peak height became smaller for a given Ge content. The B concentration in Si1–xGex film estimated from Raman measurement was in good agreement with secondary ion mass spectroscopy analysis results. Boron concentration as low as 8.7 × 1017 atoms/cm3 can be detected by Raman spectroscopy, which is ~30 times more sensitive than the detection limit (2.7 × 1019 atoms/cm3) of high-resolution x-ray diffraction.

In every wafer processing step wafer stress management is extremely important for advanced device manufacturing. Thermally induced stress on device wafers has a large impact on lithography and affects device yield. Thermally induced stress during rapid thermal annealing (RTA) steps in high density 512MB DRAM device fabrication was investigated using a lamp-based (cold wall) RTA system and compared to results using a furnace-based (hot wall) single wafer RTA system. Compared to the lamp-based (cold wall) system, RTA in a furnace-based (hot wall) system was found to be very effective in suppressing thermally induced stress and increasing device yield due to superior pattern transfer characteristics in lithography.

Fluorine doping of silicon dioxide films in tetraethylorthosilicate (TEOS)-based plasma enhanced chemical vapor deposition (PECVD) processes was investigated using two fluorine dopant sources, C2F6 and 1,2 bis[methyldifluorosilyl]ethane (FASi-4). Much as TEOS-based undoped silica glass (USG) films display improved step coverage over silane-based USG films, it was suspected that fluorinated silica glass (FSG) films deposited using the relatively new TEOS-based fluorine source FASi-4 might have improved gap fill capabilities as compared to FSG films deposited using gas-based C2F6 fluorine sources. The physical properties and intermetal gap filling capabilities of FSG films deposited using FASi-4 as a fluorine dopant source were compared with the properties of FSG films deposited using C2F6 as a fluorine source. Fluorine dopant levels in the films were found to be linear functions of C2F6TEOS and FASi-4yTEOS ratios. The RI, film stress, and gap fill capability were found to be strongly dependent on the Si–F content in the film regardless of dopant source reagents. Improved gap fill characteristics were observed in films doped with FASi-4 at a given Si–F/Si–O% as compared to C2F6-based FSG films. Dopant source dependence of doping characteristics, physical properties, and gap filling capability of FSG films is reported.

As an attempt to explain polytype formation and crystal growth of SiC we propose an electrostatic model in which electrostatic Coulomb force is considered as an interatomic force. The dependence of surface potential on the stacking sequence of atoms in substrates was investigated, and the growth simulation was tried considering the energetic balance under various interaction lengths.The model predicts the double positioning twin formation and the difference in area between twins in cubic 3C-SiC growth on hexagonal 6H-SiC and rhombohedral 15R-SiC substrates. The prediction was experimentally tested by simultaneous chemical vapor deposition growth on basal planes of 6H-SiC(0001) and 15R-SiC(0001). Polytype and interface structure of both specimens were investigated by reflection high energy electron diffraction (RHEED) and high resolution transmission electron microscopy (HRTEM).

Polytype control and crystal growth on 3C-SIC substrates have been investigated by using a sublimation growth technique. Single crystalline 3C-SiC(100) films (∼10μm thick) grown on Si (100) were used as substrates after removing Si by etching with a HF+HNO3 mixture. Polytypes of crystals grown on 3C-SiC(100) were examined by photoluminescence, Raman scattering, X-ray diffraction and reflection high energy electron diffraction analyses. Polytypes of grown crystals change from cubic 3C-modification to hexagonal 6H-modification with temperature increase. 6H-SiC(0114) was grown on 3C-SiC(100) substrates at high temperatures. For the first time, polytypes of grown crystals were controlled to be 3C- and 6H-modifications, and the reproducibility of polytype control was confirmed through many growth runs. 6H-SiC ingots up to 20mm in diameter and 10mm in length were grown on 3C-SiC for 6 hours. The growth mechanism of 6H-SiC on 3C-SiC was discussed based on experimental study of thermal stability of 3C-SIC. Electrical properties of 6H-SiC ingots were investigated.