Material design of plasma-enhanced chemical vapour deposition SiCH films for low-kcap layers in the further scaling of ultra-large-scale integrated devices-Cu interconnects

Abstract

Cap layers for Cu interconnects in ultra-large-scale integrated devices (ULSIs), with a low dielectric constant (k-value) and strong barrier properties against Cu and moisture diffusion, are required for the future further scaling of ULSIs. There is a trade-off, however, between reducing the k-value and maintaining strong barrier properties. Using quantum mechanical simulations and other theoretical computations, we have designed ideal dielectrics: SiCH films with Si–C2H4–Si networks. Such films were estimated to have low porosity and low k; thus they are the key to realizing a cap layer with a low k and strong barrier properties against diffusion. For fabricating these ideal SiCH films, we designed four novel precursors: isobutyl trimethylsilane, diisobutyl dimethylsilane, 1, 1-divinylsilacyclopentane and 5-silaspiro [4,4] noname, based on quantum chemical calculations, because such fabrication is difficult by controlling only the process conditions in plasma-enhanced chemical vapor deposition (PECVD) using conventional precursors. We demonstrated that SiCH films prepared using these newly designed precursors had large amounts of Si–C2H4–Si networks and strong barrier properties. The pore structure of these films was then analyzed by positron annihilation spectroscopy, revealing that these SiCH films actually had low porosity, as we designed. These results validate our material and precursor design concepts for developing a PECVD process capable of fabricating a low-k cap layer.

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

“…[402][403][404][405] Shimizu's results using precursors such as 1,1-divinyl silacyclopentane (DVScP) and 5-silaspiro- [4,4]-nonane (SSN) have shown that a-SiC:H films with a significant improvement in mass density can be achieved for a given dielectric constant relative to a-SiC:H films deposited using traditional tetramethylsilane (4MS) precursors. 403 Using similar precursors, 100 nm a-SiC:H films with k values as low as 3.1 that show Cu diffusion barrier performance equivalent to higher k = 5.0 a-SiCN:H have also been demonstrated.…”

“…Continued k scaling in Si-O-C-N system.-One interesting method that has been recently described by Shimizu attempts to utilize the incorporation of long Si-(CH 2 ) x -Si networks to achieve both a reduction in k and improvement in diffusion barrier performance for a-SiC:H thin films. [402][403][404][405] Shimizu's results using precursors such as 1,1-divinyl silacyclopentane (DVScP) and 5-silaspiro- [4,4]-nonane (SSN) have shown that a-SiC:H films with a significant improvement in mass density can be achieved for a given dielectric constant relative to a-SiC:H films deposited using traditional tetramethylsilane (4MS) precursors. 403 Using similar precursors, 100 nm a-SiC:H films with k values as low as 3.1 that show Cu diffusion barrier performance equivalent to higher k = 5.0 a-SiCN:H have also been demonstrated.…”

PECVD Synthesis of Silicon Carbonitride Layers Using Methyltris(diethylamino)silane as the New Single-Source Precursor

“…Therefore we can assume that the results of the silicon, nitrogen, carbon and oxygen content in silicon carbonitride films obtained by using the EDS are authentic. It should be noted that, according H. Shumizu et al, 3,59 the increased carbon content in the films with the ratio (C/Si ∼ 4) leads to the resistance against the plasma damage, decrease of porosity and improvement of barrier properties against copper diffusion.…”

“…One can mention that the measured dielectric constants 4.4-4.5 are low than the typical values observed for silicon carbonitride barrier layers developed for interconnect application (4.8-5.8). 1 H. Shimizu et al 59 showed that a lower porosity, i.e. highly packed atomic arrangement, improves the barrier properties against Cu diffusion.…”

Review of methods for the mitigation of plasma‐induced damage to low‐dielectric‐constant interlayer dielectrics used for semiconductor logic device interconnects

“…The increase in mechanical strength in hydrocarbon crosslinks was higher than in –O‐ bridges. Extensive studies are continuing to be conducted in the views of material design, for instance, written by Shimizu et al…”