Polishing damages to electrical properties of BLT thin film capacitors fabricated by damascene process of chemical mechanical polishing
BLT thin film capacitor was fabricated by the novel method of chemical mechanical polishing (CMP) process. The electrical characteristics including P-V and I-V of BLT capacitor were damaged by the polishing pressure which is one of the main factors to improve the CMP performance for BLT thin film; therefore, the lower polishing pressure must be selected for the good electrical characteristics although the removal rate was lower.
Platinum chemical mechanical polishing (CMP) characteristics for high density ferroelectric memory applications
The key component of ferroelectric random access memory (FeRAM) is a capacitor including a ferroelectric thin film and electrode materials. Platinum is one of the suitable metals which meet requirements such as low resistivity, high thermal stability, and good oxygen resistance. Generally, the ferroelectric and the electrode materials were patterned by a plasma etching process. The application possibility of chemical mechanical polishing (CMP) processes to the patterning of ferroelectric thin film instead of plasma etching was investigated in our previous study for improvement of an angled sidewall which prevents the densification of FeRAM. In this study, the characteristics of platinum CMP for FeRAM applications were also investigated by an approach as bottom electrode materials of ferroelectric material in CMP patterning. The removal rate was increased from 24.81nm/min by the only alumina slurry (0.0wt% of H"2O"2 oxidizer) to 113.59nm/min at 10.0wt% of H"2O"2 oxidizer. Electrochemical study of platinum and alumina slurry with various concentrations of H"2O"2 was performed in order to investigate the change of the removal rate. The decreased particle size in the alumina slurry with an addition of 10.0wt% H"2O"2 oxidizer made the improved surface roughness of the platinum thin films. Micro-scratches were observed in all polished samples.
Mechanical behaviour and durability of high volume fly ash cementitious composites
The purpose of this research is to separate different morphological particles of ASTM class F fly ash, and study their effect on mechanical behaviour and durability of high volume cementitious mixtures. In this research wet separation of raw fly ash is carried out, which resulted in three layers of different morphological particles. The first layer of particles float, comprise of about 1-5% of fly ash, is identified as cenospheres or hollow spheres. The second layer of particles is measured to be 55-60% of raw fly ash and consisting of porous spherical and rounded particles rich in Si and Al. The third layer particles is measured to be about 35-40% of raw fly ash. High volume fly ash cementitious composites containing second or third layer particles are tested under compression and bending, highlighting a higher strength and ductility in comparison to cementitious ones containing raw fly ash particles. KEYWORDS. Cementitious matrix; Raw fly ash; Second layer particles; Third layer particles.