Evolution of Copper-Oxide Damascene Structures in Chemical Mechanical Polishing

Abstract

Test wafers comprising damascene structures were designed and fabricated to investigate Cu dishing and oxide erosion. The mask design covered a wide range of linewidths and pitches, from 0.5 to 100 m, to represent such features as signal and power transmission lines, and probing or wire-bonding pads. Experiments were conducted to investigate the evolution of the pattern profile during polishing and to determine the onset and rates of dishing and erosion. The effects of Cu linewidth and area fraction on the rates of pattern planarization, Cu dishing, and oxide erosion have been quantified. The effect of hardness of the composite surface on dishing and erosion were examined. An optimization scheme, employing particle size, particle hardness, and pad stiffness, to enhance the selectivity between SiO 2 , Ta, and Cu, and to reduce die-scale nonplanarity is proposed.

A dishing model for chemical mechanical polishing of metal interconnect structures

“…Another important result is that dishing strongly depends on linewidth, but minimally on pattern density. This is consistent with experimental observation [2,4,5,14,28].…”

“…Also, their model is not valid if the pattern density is greater than 0.83. Later, similar phenomenon has been observed in copper array line polishing [12,14,15]. Recently, a formula of steady-state dishing based on contact mechanics and statistical method has been proposed by Vlassak [16].…”

“…As shown in the experimental results, the steady-state dishing profile usually occurs after a short period of overpolishing [12,14]. Therefore, the present study will focus only on the steady-state …”

Potassium sorbate as an inhibitor in copper chemical mechanical planarization slurries. Part II: Effects of sorbate on chemical mechanical planarization performance

“…The dishing phenomenon has been attributed to uncontrolled dissolution of the copper structures and to the bending of the used CMP pad. Many researchers have tried to elucidate the cause of dishing with physical modeling and simulations [10][11][12]. The most widely accepted model for dishing was proposed by Steigerwald [13].…”

A Combined Triboelectrochemical QCM for Studies of the CMP of Copper

“…5,6 Unfortunately, differences in removal rates of copper and the adjacent low dielectric materials result in unacceptable surface features such as dishing of copper or erosion of the dielectric material, which require additional processing steps to correct. 5,7,8 In addition, many of copper's inherent properties make control of surface topography during the various wet and dry processing steps difficult.…”