Düşük Sıcaklıkta Kimyasal Buhar Biriktirme (CVD) Yöntemiyle Epitaksiyel SiGe Film Büyütme Ve Film Karakterizasyonu

Abstract

In the scope of thesis, selective epitaxial growth of monocrystal silicon-germanium-carbon (SiGeC) and monocrystal silicon (SiCap) were deposited on silicon substrate at low temperature by using reduced pressure chemical vapor deposition (RPCVD) technique. Silane as silicon source, german as germanium source, diborane as boron source and metilsilane as carbon source were used at film deposition. SiGeC and SiCap films were applied SiGeC HBT (Silicon-Germanium-Carbon Heterojunction Bipolar Transistor) technology which is the first step of 0,25 µm SiGeC BiCMOS (Silicon-Germanium-Carbon Bipolar Complementray Metal Oxide Semiconductor) process technology and electrical performance of the films in the transistor was evaluated. At the first step of the study, the optimum temperature of the film growth in the RPCVD reactor using silane was determined. The SiGeC film thickness, germanium ratio and film quality was characterized by spectroscopic ellipsometer. Evaluating with growth temperature and process time, the optimum temperature for a single crystal SiGeC film which grown at SiGeC HBT which is the first step of 0,25 µm SiGeC BiCMOS was found to be 625°C. Secondly, selective epitaxial SiGeC film was studied due to presence of silicon nitride film on the base sidewall SiGeC BiCMOS transistor. Hydrochloric acid (HCl) was added to the process gases for creating selective property. Film thickness was characterized spectroscopic ellipsometry and images of surface morphology of sidewall was obtained by scanning electron microscopy (SEM). As a result of the characterization studies, selective epitaxial growth of SiGeC film was provided with 25 ml/min HCl gas flow at 625°C. In the second step of the study, monocrystal SiCap film was grown on the SiGeC film. SiCap film prevents diffusion of phosphorus ions from emitter to base region. Initially, the optimum temperature of film growth with silane gas at RPCVD reactor was determined. Secondly, as in SiGeC film, selective epitaxial growth of SiCap film was also studied. As a result of the characterization studies, selective epitaxial growth of SiCap film was provided with 35 ml/min HCl gas flow at 675°C. Structural and morphological characterization of epitaxial films was done by spectroscopic ellipsometer, SEM, transmission electron microscopy (TEM), secondary ion mass spectroscopy (SIMS) and high resolution x-ray diffraction (HRXRD) analysis. SIMS analysis has shown that boron ions couldn’t diffuse into the collector region from the epitaxial SiGeC film which grown in the transistor base region using silane gas at low temperature (625°C). HRXRD analysis proved the SiGeC film to be a single crystal and strained form. TEM analysis has shown that dislocation density of SiGeC film which has the single crystal form is at a level of 3×107cm-2. For electrical characterization of the growth film, SiGeC and SiCap films were grown to the base region of SiGeC HBT structure and current-voltage (I-V) measurements were evaluated for determining electrical performance of the transistor. The epitaxial films which grown at high temperature with SiCl2H2 (dichlorosilane) and low temperature with SiH4 (silane) were applied to the SiGeC HBT structure. The films were electrically compared on the basis of current gain of transistor. The epitaxial films of silane gas at low temperature has approximately ten times more current gain than the films of dichlorosilane.