Untitled in english

Author(s)

Alan Rodrigo Navia

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Escola Politécnica (EP/BC)
• Defense date: 2002-11-22

Examining board members

Sebastião Gomes dos Santos Filho; José Alexandre Diniz

• Advisor: Sebastião Gomes dos Santos Filho

Abstract

In this work, MOS capacitors with nickel gate onto polysilicon or aluminum were manufactured to be electrically characterized using Capacitance x Voltage and Current x Voltage curves. Nickel onto polysilicon or aluminum layers were also physically characterized using SEM (Scanning Electron Microscopy), AFM (Atomic Force Microscopy), RBS (Rutherford Backscattering Spectrometry) and XRD (X Ray Diffraction) techniques. The nickel plating onto the mentioned surfaces was performed surfaces was performed using the Electroless Technique, preceded by surface activation in a palladium based solution. Due to the fact of the reducing agent to be the hypophosphite species, the obtained film was an amorphous alloy of nickel and phosphorus. Nickel was deposited onto polysilicon layers presented good morphological characteristics and low roughness as observed from AFM and SEM measurements. RBS spectra showed the stoichiometry and film thickness evolution as function of time, allowing obtaining the phosphorus content in the alloy (12 to 17%) and an estimative of the nickel plating rate (81,2 nm/min). XRD analysis was performed to study the effect of annealing at 420°C. Several crystalline phases were observed including nickel/phosphorus alloy, and also, nickel and palladium silicides. MOS capacitors with nickel deposited onto polysilicon gates presented good electrical characteristics after annealing according to CxV curves. IxV measurements showed that nickel plating affected the electrical breakdown field, probably due to contamination in the gate oxide caused by the nickel plating solution. On the other hand, nickel onto aluminum structures presented only reasonable morphological characteristics and higher roughness as observed from AFM and SEM measurements. RBS spectra showed the stoichiometry and film thickness evolution as function of time, allowing obtaining high phosphorus content in the alloy (14 to 22%) and an estimative of the nickel plating rate (´approximately equal´100 nm/min). XRD analysis was performed to study the effect from annealing at 420°C. Several crystalline phases were observed including nickel/phosphorus alloy, and also, nickel/aluminum alloy. MOS Capacitors with nickel onto aluminum gate presented peculiar characteristics after nickel contact plating and annealing, such as a high interface state density and a capacitor area increase of about 30%. This increase was due to lower selectivity of the employed plating solution to cover the aluminum surface. IxV measurements showed that nickel plating slightly diminished the electrical breakdown field, probably due contamination in the gate oxide caused by the nickel plating solution. (AU)