Title :
UV-O3 and dry-O2: Two-step-annealed chemical vapor-deposited Ta2O5 films for storage dielectrics of 64-Mb DRAMs
Author :
Shinriki, Hiroshi ; Nakata, Masayuki
Author_Institution :
Hitachi Ltd., Tokyo, Japan
fDate :
3/1/1991 12:00:00 AM
Abstract :
A capacitor fabrication technique is developed to obtain an extremely thin Ta2O5 film with an effective SiO 2 film thickness of 2.8 nm (equivalent to 12 fF/μm2 ) for use in a low-power 64-Mb DRAM. A two-step annealing process is used after deposition of the Ta2O5 film by thermal chemical vapor deposition (CVD). The first step is ozone (O3) annealing with ultraviolet light irradiation, which is the most effective means of reducing leakage current. A model for explaining the effectiveness of the UV-O3 annealing treatment is proposed. Excited oxygen atoms in the singlet state (1D), which are generated selectively in the ozone gas irradiated by a mercury lamp, repair the oxygen vacancies existing in the as-deposited CVD-Ta 2O5 film, resulting in a marked reduction of the film´s leakage current. The second step is dry-O2 annealing, which reduces the defect density of initial breakdown. Sufficient capacitance can be obtained while maintaining a low leakage current and sufficient step coverage for a 1.5-V supply-voltage 64-Mb DRAM having a high-aspect three-dimensional memory cell
Keywords :
CVD coatings; DRAM chips; annealing; dielectric thin films; incoherent light annealing; tantalum compounds; 64 Mbit; DRAMs; O2; O3; Ta2O5-SiO2-Si; capacitor fabrication technique; defect density; dry oxygen annealing; high-aspect three-dimensional memory cell; initial breakdown; ozone annealing; singlet state; step coverage; thermal chemical vapor deposition; two-step annealing process; ultraviolet light irradiation; Annealing; Atomic layer deposition; Capacitance; Capacitors; Chemical vapor deposition; Electric breakdown; Fabrication; Lamps; Leakage current; Random access memory;
Journal_Title :
Electron Devices, IEEE Transactions on
