Stan D. Tsai

Cu Planarization in Electrochemical Mechanical Planarization

The electrochemical mechanical planarization (Ecmp) process is a revolutionary planarization technology uniquely combining removal rate controlled by charge with superior planarization efficiency in the near no-shear regime. A planarization mechanism for Ecmp is proposed to explain the high planarization efficiency. Meanwhile, the effects of applied voltage on removal rate and planarization efficiency are discussed. The electrical feature allows Ecmp to be a planarization process with removal rate independent of downforce, enabling a wide removal rate window and high planarization efficiency.

Development of a production worthy copper CMP process

A chemical mechanical polishing (CMP) process for copper damascene structures has been developed and characterized on a second generation, multiple platen polishing tool. Several formulations of experimental copper slurries containing alumina abrasive particles were evaluated for their selectivity of copper to Ta, TaN and PETEOS films. The extent of copper dishing and oxide erosion of these slurries is investigated with various process parameters such as slurry flow rate, platen speed and wafer pressure. The amount of dishing and erosion is found to be largely dependent on process parameters as well as the slurry composition. It is shown that the extent of oxide erosion and copper dishing can be significantly reduced by using a two slurry copper polish process (one slurry to polish copper and another to polish barrier layers) in conjunction with an optical end-point detection system.

A low cost and residue-free abrasive-free copper CMP process with low dishing, erosion and oxide loss

Traditional slurry copper (Cu) CMP processes have disadvantages in terms of dishing, erosion, Cu and oxide losses, micro-scratches and cost due in part to the presence of abrasive particles during polishing. A stable abrasive-free (AF) Cu CMP process and a low-abrasive barrier removal process have been developed. With these processes it has been possible to repeatably demonstrate metal-residue free wafers with low dishing, low erosion, low metal and oxide losses, over-polishing insensitivity, and low cost.

Copper CMP at low shear force for low-k compatibility

Copper CMP faces significant technical challenges at the 100 nm technology node and beyond as low-k dielectric materials replace conventional SiO/sub 2/ dielectrics. Low shear force becomes the focus of CMP process development. However, the effects of shear force during the CMP process have not been fully explored. In this paper, we studied the polishing shear force under various process conditions. The correlation between polishing shear force and low-k material delamination is experimentally established. A low shear force CMP process is developed that demonstrates low-k compatibility with comparable polishing performance to conventional high shear operation region.

Method for improved CMP pad conditioning performance

A new pad conditioning arm design enables the use of closed-loop control (CLC) to improve conditioning performance throughout the life of a pad and disk pair. Measured pad conditioner torque is used to monitor and control the conditioning and polish processes in situ and in real time. The CLC system maintains process performance throughout pad life by adjusting the conditioner down force to compensate for process drift, such as the loss of diamond aggressiveness as the disk ages.