Simultaneous Determination of Young's Modulus and Density of Ultrathin Low‐k Films Using Surface Acoustic Waves

Abstract

The nondestructive testing (NDT) of mechanical properties in ultrathin low dielectric constant (low‐k) films is a major challenge in integrated circuit manufacturing. Young's modulus and density are closely related parameters for low‐k films. This study presents a method for NDT of Young's modulus and density of porous low‐k black diamond (SiOC:H, BD) films. A linear frequency modulation (LFM) surface acoustic wave (SAW) interdigital transducer (IDT) with a frequency range of 20–250 MHz is designed to generate SAW signals on the samples. The series of SAW waveforms obtained on the samples are processed to obtain experimental SAW dispersion curves across a broad frequency range. By comparing these experimental curves with theoretical dispersion curves, as well as their first‐order derivatives, Young's modulus and density of porous low‐k BD films with thicknesses of 100, 300, 500, and 1000 nm are characterized. To verify Young's modulus measurements from the SAW method, a control experiment using nanoindentation is conducted. The results demonstrate that the SAW method can reduce the impact of the substrate and is independent of the film thickness. This study presents a highly accurate measuring method for simultaneous multiparameter evaluation of ultra‐thin low‐k films.