Graduation Year

2007

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

Mechanical Engineering

Major Professor

Ashok Kumar, Ph.D.

Keywords

Temperature, Tribology, Slurry, Electrochemistry, Abrasive particles, Scratches, Pad conditioning, Coefficient of friction

Abstract

Chemical Mechanical Planarization (CMP) is one of the most critical processing steps that enables fabrication of multilevel interconnects. The success of CMP process is limited by the implementation of an optimized process and reduction of process generated defects along with post CMP surface characteristics such as dishing and erosion. This thesis investigates to identify various sources of defects and studies the effect of factors that can be used to optimize the process. The major contributions of this work are: Understanding the effect of temperature rise on surface tribology, electrochemistry and post CMP pattern effects during the CMP process; investigating the effect of pad conditioning temperature and slurry flow rate on tribology and post CMP characteristics; development of novel slurries using polymer hybrid particles and improvement in slurry metrology to reduce surface damage during CMP.

From the current research, it was shown that the effect of temperature on CMP tribology is predominantly affected by the polishing parameters and the polishing pad characteristics more than the chemical nature of the slurry. The effect of temperature is minimal on the resulting surface roughness but the with-in die non-uniformity is significantly affected by the temperature at the interface. Secondly, in this research it was shown that the effectiveness and aggressiveness of the pad conditioning process is highly influenced by the conditioning temperature. This aspect can be utilized to optimize the parameters for the pad conditioning process. Further, post CMP characteristics such as dishing, erosion and metal loss on patterned samples were shown to decrease with increase in slurry flow rate. This research then concentrates on the development of novel low defect slurry using polymer hybrid abrasive particles.

Several varieties of surface functionalized polymer particles were employed to make oxide CMP slurries. These novel slurries proved to be potential candidates to reduce surface damage during CMP as they resulted in low coefficient of friction and much less surface scratches as compared to conventional abrasives. Thus, this research helps to reduce defects and non-planarity issues during CMP process thereby improving yield and reducing the cost of ownership.

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