Hydrogen diffusion behavior in CH2P-molecular-ion-implanted silicon wafers for CMOS image sensors

Three-dimensional (3D) stacked complementary metal oxide semiconductor (CMOS) image sensors require reduction in leakage current due to interface state defects at the SiO2/Si interface. Hydrocarbon molecular ion implanted silicon wafers have identified the hydrogen termination effect of such wafer, contributing to high performance of CMOS image sensors. However, recently, low-temperature heat treatment during a device process has been shown to reduce the concentration of hydrogen diffusing from the hydrocarbon-molecular-ion-implanted region. Thus, a new method of molecular ion implantation with phosphorus added has been developed. In this paper, we present the results of our analysis of the diffusion behavior of hydrogen in a hydrocarbon molecule with phosphorus (CH2P) by reaction kinetic analysis and TCAD simulation. The results of reaction kinetic analysis show binding energies of 0.76 eV (C–H2 binding state) and 0.45 eV (P–H binding state). TCAD simulation results show that the 0.76 eV binding energy indicates that hydrogen is adsorbed in a carbon and silicon self-interstitial cluster (C/I cluster). On the other hand, the binding energy of 0.45 eV indicates that hydrogen is trapped in phosphorus complexes. Hydrogen in the CH2P-implanted region diffuses owing to the difference in between these binding states. Thus, a reduction in the interface state density of Si/SiO2 can be expected.