There are silicon nitride and silicon oxide thin films as typical Si based dielectrics used in process of electronic devices fabrication. Silicon nitride films have been widely used as the gate spacer and hard mask in Front End Of Line(FEOL), and the Inter-Layer Dielectrics (ILD) and etch stopper, particularly for Cu metalization, in Back End Of Line(BEOL). Silicon oxide films have been broadly utilized for the sealing oxide in Dynamic Random Access Memory (DRAM) transistor, the Inter-Metal Dielectrics (IMD) in integrated circuit (IC) processing, and the gate oxide in Thin Film Transistor Liquid Crystal Display (TFT-LCD) devices.
These Si based thin films are deposited by Low-Pressure Chemical Vapor Deposition (LPCVD) in the front-end processing or by Plasma-Enhanced Chemical Vapor Deposition (PECVD) in back-end processing. However, high process temperature of LPCVD and poor film quality of PECVD are being expected to limit the performance and the reliability of the state-of-art IC in the near future. Accordingly precise thickness control and excellent properties of silicon nitride and silicon oxide thin films are essential for the next-generation semiconductor and display devices. Recently, Atomic Layer Deposition (ALD) attracts much interest in silicon integrated circuit processing owing to its accurate thickness control, conformal coverage, high film quality, and lower processing temperature.
Silicon nitride thin films were deposited by atomic layer deposition (ALD) method using $SiCl_4$ or $SiH_2Cl_2$ as the Si precursor and $NH_3$ as the N precursor, and the deposited films were characterized comparatively. The thickness of the film increased linearly with the number of deposition cycles, so that we can precisely control the thickness of the film by the number of cycles. As compared with the deposition using $SiCl_4$, the deposition using $SiH_2Cl_2$ exhibited larger deposition rate at lower precursor exposures and the deposited films using $SiH_2Cl_2$ had lower wet etch rate. Silicon nitride films with the Si/N ratio of approximately 1 were obtained using both Si precursors at 550℃, however, the films deposited using $SiH_2Cl_2$ exhibited higher concentration of H as compared with those of the $SiCl_4$ case. Silicon nitride thin films deposited by ALD showed similar physical properties, such as composition or integrity, with the silicon nitride films deposited by low-pressure chemical vapor deposition, lowering deposition temperature by more than 200℃.
Silicon dioxide thin films were deposited on p-type Si (100) substrates by atomic layer deposition(ALD) using $SiH_2Cl_2$ and $O_3$. $O_3$ was generated by corona discharge inside the delivery line of $O_2$. The oxide film was deposited mainly from ozone not from $O_2$, because we could not observe the deposited film on the substrate without corona discharge at the same process condition. The growth rate of the deposited films increased linearly with the exposures of $SiH_2Cl_2$ and $O_3$, and was saturated at approximately 0.35 ㎚/cycle with the reactant exposures over $3.6×10^9L$. At a fixed $SiH_2Cl_2$ exposure of $1.2×10^9L$, growth rate increased with $O_3$ exposure and was saturated at approximately 0.28 ㎚/cycle with $O_3$ exposures over $2.4×10^{9}L$. The composition of the deposited film also varied with the exposure of $O_3$. The Si/O ratio gradually decreased to 0.5 with increasing the exposure of $O_3$. The silicon oxide film prepared by ALD at 300℃ showed better stoichiometry, wet etch rate and electrical properties than those of the silicon oxide films deposited by conventional LPCVD or APCVD methods at 400~800℃.
