Evidence of ultra-low-k dielectric material degradation and nanostructure alteration of the Cu/ultra-low-k interconnects in time-dependent dielectric breakdown failure

127

115

Over the past decade, the primary focus for improving the performance of nano-electronic metal interconnect structures has been to reduce the impact of resistance-capacitance (RC) delays via utilizing insulating dielectrics with ever lower values of dielectric permittivity. The integration and implementation of such low dielectric constant (i.e. low-k) materials has been fraught with numerous challenges. For intermetal and interlayer (ILD) low-k dielectrics, these challenges have been largely associated to integration with metal interconnect fabrication processes and well documented and reviewed in the literature. Although equally important, less attention has been given to other low-k dielectrics utilized in metal interconnect structures that are commonly referred to as low-k dielectric barriers (DB), etch stops (ES), and/or Cu capping layers (CCL). These materials present numerous challenges as well for integration into metal interconnect fabrication processes. However, they also have more stringent integrated functionality requirements relative to low-k ILD materials that serve only a basic purpose of electrically isolating adjacent metal lines. In this article, we review the integration challenges and associated integrated functionality requirements for low-k DB/ES/CCL materials with a focus on the current status and future direction needed for these materials to facilitate both Moore's law (i.e. More Moore) and More than Moore scaling.

Section: Low-k Ild Cu Cumentioning

confidence: 91%

Dielectric Barrier, Etch Stop, and Metal Capping Materials for State of the Art and beyond Metal Interconnects

King

2014

127

115

“…Previous efforts to collect infrared spectra from patterned SiOC:H films using an FT-IR microscope have been reported by Lam et al 40,41 Spectral artifacts due to scattering and optical interferences from the IR beam reflected from the complex underlying structures could also affect spectral interpretation. 47,48 By using an AFM probe as a mechanical absorption sensor smaller than the diameter of the IR radiation, the AFM-IR technique detects the local thermal expansions that are in the near-field and minimizes optical artifacts in the far-field.…”

Section: Absorbance (Au)mentioning

confidence: 99%

“…[40][41][42] Thus, nanometer scale low-k a-SiOC:H/Cu interconnects represent an excellent test vehicle for demonstrating combined nanoscale chemical structure and physical property characterization.…”

Section: 37mentioning

confidence: 99%

“…36,37 Micron-scale transmission FTIR and nanoindentation measurements have been the dominant techniques for structure-property characterization of low-k materials, 38,39 but are largely incapable at the nanoscale and have been limited to examining blanket films or micron wide, ordered arrays of patterned structures. [40][41][42] Thus, nanometer scale low-k a-SiOC:H/Cu interconnects represent an excellent test vehicle for demonstrating combined nanoscale chemical structure and physical property characterization.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Nanoscale Chemical-Mechanical Characterization of Nanoelectronic Low-kDielectric/Cu Interconnects

Lo¹,

Dazzi

Marcott³

et al. 2015

Combined nanoscale chemical and mechanical property characterization has largely been limited by the inability to extend chemical structure identification techniques such as infrared (IR) absorption spectroscopy into the nanometer regime due to diffraction limitations. The recent development of atomic force microscope (AFM) based IR spectroscopy (AFM-IR) has now enabled infrared chemical spectroscopy with resolution well below the diffraction limit. However, the combination of AFM-IR with other AFM based techniques to achieve nanoscale chemical structure-mechanical property characterization has yet to be demonstrated. In this regard, we have combined AFM-IR chemical and contact resonance AFM (CR-AFM) mechanical measurements in the investigation of low dielectric constant (low-k) / Cu damascene structures fabricated using a 90 nm interconnect process technology. We show that the combined AFM-IR and CR-AFM results can be utilized to perform nanoscale chemical-mechanical characterization of both the nano-patterned metal and the low-k dielectric whose mechanical properties are sensitive to chemical modification by the interconnect fabrication process. The continued drive to seek and exploit new materials and phenomena at nanometer dimensions has increased the demand for metrologies capable of characterizing both chemical structure and physical properties at the nanoscale. The nanoelectronics industry in particular has identified metrologies capable of performing nanoscale structureproperty measurements on new materials and devices as an area of critical need in their industry technology roadmap.1,2 Such requirements for nanoscale physical property characterization have readily been met by the development of a range of scanned probe techniques capable of assessing the thermal, 3,4 mechanical, 5,6 and electrical 7,8 properties of materials at the nanoscale. 9 However, the development of nanoscale chemical structure metrologies has been hindered by the difficulty of scaling popular micron-scale techniques such as infrared (IR) absorption spectroscopy [10][11][12] into the nanometer regime due to diffraction limits defined by the Rayleigh equation.13,14 To overcome these limitations, a number of approaches combining optical spectroscopy with scanned probe microscopy (SPM) have been proposed and demonstrated. [13][14][15][16][17][18][19][20] Of these, the atomic force microscope (AFM) IR technique, which is based on photothermally induced resonance (PTIR), 21,22 has recently garnered significant interest due to a demonstrated spatial resolution of 25-100 nm, and a close correlation to micron-scale Fourier transform infrared (FTIR) spectroscopy. 13,14 This combination has resulted in the utilization of AFM-IR in a number of biological, 23-25 polymeric, 26-28 and semiconductor [29][30][31] applications. However, AFM-IR and related techniques have yet to be routinely combined with other AFM based techniques to achieve the ultimate goal of nanoscale structure-property characterization. In this regard, we provide a compelling...

“…[4][5][6] For low-k materials, T-FTIR spectroscopy has shown great utility for qualitatively understanding structure-property relationships and fine tuning of material properties to meet the industry's need. [7][8][9][10][11][12][13][14] However, several problems are encountered when attempting to quantitatively analyze T-FTIR spectra of these and other types of thin films on thick substrates. These challenges are primarily due to the presence of strong interference fringes in the spectra produced by multiple reflections within the substrate and thin film.…”

mentioning

confidence: 99%

Analysis of Low-k Dielectric Thin Films on Thick Substrates by Transmission FTIR Spectroscopy

Milošević¹,

King²

2014

Transmission Fourier-transform infrared (T-FTIR) spectra of thin films on thick substrates are characterized by strong interference fringes that hamper quantitative analysis of the observed thin film absorption bands. In this article, we review and present methods for removing these fringes to extract the pure thin film absorption coefficient from the experimental T-FTIR spectra. To illustrate the benefits of a recently developed method for removing such fringes, we analyze T-FTIR spectra for a series of a-SiO2 and a-SiOC:H thin films typically utilized in nano-electronic interconnect structures as low permittivity (i.e. low-k) interlayer dielectrics. The sources and magnitude of the errors present in analysis of both the uncorrected and corrected experimental T-FTIR spectra are compared. We demonstrate that conventional analysis of the uncorrected low-k a-SiOC:H T-FTIR spectra can lead to substantial quantitative errors that are dramatically reduced using the described method for appropriately removing the experimental thin film fringes.