Microstructure evolution of nanometer-sized hemispherical-grained Si deposited by RTCVD

An uneven coating made of hemispherical-grained Si (HSG) was formed on an amorphous Si layer by using a rapid thermal CVD (RTCVD) process. The uneven coating increases the effective surface area of a capacitor electrode and subsequently increases by a factor of 2 the capacitance of a dynamic random access memory cell. The formation of HSG by RTCVD consists of “seeding” and subsequent isothermal annealing stages. During the “seeding” stage, hemispherical nanometer-sized Si single crystals are formed and distributed uniformly on the surface of the substrate. The rapid annealing at 665°C under high vacuum, for times between 5 and 20 s, increases the size of the Si grains and forms polycrystalline Si hemispheres. The RTCVD is a new process of HSG coating and it has advantages over the two main existing processes.