Electrical Reliability of Cu and Low-K Dielectric Integration

Abstract

The recent demonstrations of manufacturable multilevel Cu metallization have heightened interest to integrate Cu and low-K dielectrics for future integrated circuits. For reliable integration of both materials, Cu may need to be encapsulated by barrier materials since Cu ions (Cu + ) might drift through low-K dielectrics to degrade interconnect and device integrity. This paper addresses the use of electrical testing techniques to evaluate the Cu + drift behavior of low-K polymer dielectrics. Specifically, bias-temperature stress and capacitance-voltage measurements are employed as their high sensitivities are well-suited for examining charge instabilities in dielectrics. Charge instabilities other than Cu + drift also exist. For example, when low-K polymers come into direct contact with either a metal or Si, interface-related instabilities attributed to electron/hole injection are observed. To overcome these issues, a planar Cu/oxide/polymer/oxide/Si capacitor test structure is developed for Cu + drift evaluation. Our study shows that Cu + ions drift readily into poly(arylene ether) and fluorinated polyimide, but much more slowly into benzocyclobutene. A thin nitride cap layer can prevent the penetration.

High-Performance Polymer Type Capacitors

“…For reliable integration of both materials, Cu may need to be encapsulated by barrier materials. Wong et al [70] advocated the use of electrical testing techniques to evaluate the Cu+ drift behavior of low-κ polymer dielectrics. Specifically, they employed biastemperature stress and capacitance-voltage measurements as their high sensitivities were well-suited for examining charge instabilities in dielectrics.…”

“…BErT/PI based thin films gave encouraging results in flexible optoelectronic devices and embedded capacitors [88]. High temperature, flexible polymer film capacitor applications used for developing low-cost processes for memory devices that employ relatively inexpensive materials, and Cu based nanocomposite applications demonstrated very good performances [70]. Wide temperature dielectric properties and corona resistance were obtained using polyimide and ZrO 2 nanocomposites for high energy density capacitor applications at high temperature.…”

Electro-discharge machining of mesoscopic parts with electroplated copper and hot-pressed silver tungsten electrodes

“…Silver as well as copper are known to destroy electronic devices by diffusion into the bulk silicon. Recent advances in diffusion barriers [8] allow the use of copper in integrated circuits, but at elevated temperatures in particular (>750 • C) [9] these barrier layers tend to fail.…”