Tantalum Pentoxide for Advanced DRAM Applications

Abstract

Tantalum pentoxide (Ta2O5) films were deposited from the reaction of tantalum pentaethoxide (Ta(OC2H5)5) and oxygen (O2) using the Lam Research Corporation DSM™9800 advanced LPCVD reactor. Typical films were deposited at a rate of 0.9 – 1.1 nm/min at 400°C. The films were stoichiometric with an O/Ta ratio of 2.57/1.00 and excellent compositional uniformity. Conformity was >95% indicating that the process is surface reaction rate limited. Films with non‐uniformities <2.2% were deposited on 300 mm wafers. The deposited non‐uniformity on 150mm and 200mm wafers was <2.0% ‐1σ within a wafer, wafer to wafer within a batch, and batch to batch. The dielectric constant for as‐deposited films was 22–24, and as high as 34 for films which were heat treated. Various post deposition heat treatments were performed to improve the capacitor's electrical properties. Superior results were obtained from rapid thermal annealing (RTA) in N2O compared with RTA in O2 and two‐step UV‐O3 followed by high temperature annealing in dry O2. Values for the leakage current of <10-8 A/cm2 at 1.2 volts negative bias (worst case) and breakdown >5 MV/cm at 1.6μΑ with tegox<2.5 nm have been obtained. These values meet the requirements for 256 Mbit DRAM memory devices Bottom and top electrode formation and integration issues are also addressed.

Structural and optical properties of different dielectric thin films for planar waveguiding applications

“…Table 1 gives the process parameters for each of the samples. Due to its high dielectric constant, high refractive index in the visible spectral range 26 , and high chemical and thermal stability, tantalum pentoxide thin films have been studied for applications such as high density dynamic random access memories (DRAMs) 27,28 , decoupling capacitors 29,30 , antireflection coatings 31,32 and optical waveguides 33 . Many different techniques to deposit Ta 2 O 5 thin films have been utilized allowing its use in compact photonics circuits and as a potential host for rare earth ions to achieve optical gain 34 .…”

Electrode Defects in Multilayer Capacitors Part II: Finite Element Analysis of Local Field Enhancement and Leakage Current in Three‐Dimensional Microstructures

“…[3][4][5][6][7] Also, notable is the fact that there is a considerable decrease in the insulation resistance of MLCCs with decreasing dielectric layer thickness, which can lead to a higher leakage current. However, with rapid miniaturization in the electronics industry, there has been a growing demand for increasing number of dielectric layers and scaling down the dielectric layer thickness to increase the volumetric capacitance.…”

Effect of Firing Rates on Electrode Morphology and Electrical Properties of Multilayer Ceramic Capacitors

“…Specifically, their performance can be severely affected by the morphology of the electrode–dielectric interface. Microstructural defects such as rough interfaces and electrode discontinuities have been found to affect the device properties adversely . Local field enhancements arising from electrode discontinuities and rough interfaces lead to a lower dielectric breakdown strength, a higher steady‐state leakage current, and limited performance in terms of operating voltage, yield, and capacitance levels for specific geometries .…”