A. Banerjee et al., Fabrication and performance of selective HSG storage cells for 256 Mb and 1 Gb DRAM applications, IEEE DEVICE, 47(3), 2000, pp. 584-592
Fabrication of rapid thermal nitrided HSG transformed crown capacitor stora
ge cells incorporating an ultrathin low pressure chemical vapor deposition
(LPCVD) Ta2O5 and Si3N4/SiO2(NO) dielectric is proposed, 256 Mb array with
HSG crown cells of 0.3 mu m diameter x 0.6 mu m height and 49 A T-eff showe
d an area enhancement factor of 1.7 (relative to untransformed crown cell),
C-min/C-max ratio of >0.95, and capacitance of 16.7 fF/cell is obtained. A
measured leakage current density of 0.7 nA/cm(2) at 1.2 V is reported.
Metal-oxide-semiconductor capacitor (MOSCAP) devices with HSG electrode for
1 Gb application are characterized using capacitance-voltage (C-V) and cur
rent-voltage (I-V) analyses. Detailed HSG grain characterization results ar
e presented with correlation to the electrical behavior of the devices. Dev
ices are formed using LPCVD Ta2O5 and/or Si3N4 dielectric. HSG films formed
from 4 x 10(20) atoms/cc phosphorus doped amorphous silicon show depletion
in C-V behavior. It is shown that phosphine doping of HSG film is required
to avoid depletion. Process selectivity of UHV/CVD HSG transformation mech
anism applied to thermal oxide and nitride field dielectrics is fully explo
red. Selectivity limits for different types of dielectric are also presente
d. Effect of critical parameters such as a-Si dopant concentration, HSG inc
ubation time, anneal conditions, and a-Si layer thickness on HSG transforma
tion are discussed for 1 Gb crown cells.