High Performance Ir/TiPrO/TaN MIM Capacitors for Analog ICs Application

Abstract

In this paper, we demonstrate high quality material TiPrO and high density Ti x Pr 1-x O (x~0.67) metal-insulator-metal (MIM) capacitors using high work function (~5.3 eV) Ir top electrode. Very low leakage current of 7 10 -9 A/cm 2 at -1 V and high 16 fF/ m 2 capacitance density are achieved for 400 o C anneal TiPrO, which also meets the ITRS goals (at year 2018) of 10 fF/ m 2 density and /( ) 7 fA/(pF ) J C V V . Furthermore, the improved high 20 fF/ m 2 capacitance density TiPrO MIM is obtained at higher annealing temperature, where low leakage current 1.2 10 -7 A/cm 2 is measured at -1 V. These good performances indicate TiPrO MIM is suitable for analog/RF ICs Applications. IntroductionThe technology evolution for Metal-Insulator-Metal (MIM) capacitors (1)-(16) requires higher capacitance density with low leakage current at evaluating temperature (17). Besides, the MIM capacitors are also used for Analog/RF ICs and DRAM technology. Low voltage-or temperature-dependence of capacitance (VCC or TCC) is also needed for the multi-functional System-on-Chip (SoC) applications. Since the capacitance density equals /t , the only method for higher density, without increasing unwanted leakage current by decreasing dielectric thickness (t ), is to use higher dielectric constant dielectric ( ) materials. Thus, the MIM capacitors are continuously integrated with higher dielectrics from Al 2 O 3 ( =10) (3), HfO 2 -Al 2 O 3 ( ~15) (9), ZrO 2 , TiTaO (13), TiHfO (15) and TiNiO ( ~36) (16). One major drawback for higher-MIM device is the large leakage current due to low conduction band offset ( E C ) at evaluated temperature that leaks out the stored charge in capacitor (Q=C V). However, increasing dielectric constant ( ) usually leads to decreasing of E C with respect to the electrode. This is also the challenge of flash memory but unavoidable during IC operation due to large circuit density and high DC power dissipation due to leakage current. The possible solution is using high bandgap (E G ) dielectric to form the laminate (9) or multi-layer structure (10), but the overall value and voltage coefficient of capacitance (VCC) are largely degraded. Pr 2 O 3 is one of attractive rare earth metal oxides with many merits such as large conduction band offset ( E C~ 1 eV) (18), moderate dielectric constant ( ~15) and large bandgap (E G ~4 eV) (18). Furthermore, significantly larger Gibbs free energy of Pr 2 O 3 (+106 kcal/mol) (19)-(21) in contact with silicon than that of TiO 2 (+7.5 kcal/mol), Ta 2 O 5 (-52 kcal/mol), HfO 2 (+47 kcal/mol) and NiO (-51.4 kcal/mol) can avoid metal/oxide inter-diffusion or chemical reaction caused by oxygen exchange, which not only reduce the interfacial layer between dielectric layer and bottom electrode but also performs excellent thermal stability. Combining above advantages of high-Pr 2 O 3 with the high dielectric constant of TiO 2 (~50), mixed TiPrO dielectric overcomes the issue of leakage current without scarifying capacitance density.In this paper, we report Ir/TiPrO/TaN capacitors with cap...