MoS₂ as an Effective Cu Diffusion Barrier with a Back-End Compatible Process

Abstract

This study demonstrates molybdenum disulfide (MoS2) as a superior candidate as a diffusion barrier and liner. This research explores a newly developed process to show how effectively MoS2 can be applied. First, a new approach is developed to prepare molybdenum disulfide (MoS2) by microwave plasma-enhanced sulfurization (MW-PES). MW-PES can rapidly and directly grow on the target substrate at low temperatures, which is compatible with the back-end-of-line (BEOL) technology. Second, the performance of MW-PES MoS2 as a diffusion barrier and liner is reported in the subsequent section. Through time-dependent dielectric breakdown (TDDB) measurements, MoS2 is shown to have a barrier property better than that of the current material, Ta, with the same thickness. According to the model fitting, the lifetime of the device is about 45.2 times the lifetime under normal operating conditions. Furthermore, MoS2 shows its superior thermal stability in maintaining the barrier properties. MoS2 is proven to be an excellent interface as a liner as it can provide sufficient adhesion and wettability to further effectively reduce the surface scattering of copper (Cu) and significantly lower the circuit resistance.

Excitonic Rydberg States in a Trilayer to Monolayer H2-Aided CVD-Grown Large-Area MoS2 Film with Excellent UV to Visible Broad Band Photodetection Applications

“…Raman spectra of all the films at RT as presented in Figure a show two prominent characteristic (E 2g 1 and A 1g ) peak of the Mo–S phonon modes of 2H–MoS 2 with a narrow full width at half-maximum (FWHM) value indicating high crystallinity of the films. The in-plane E 2g 1 and the out-of-plane A 1g modes in the Raman spectra show a difference of 22.4 cm –1 for MAr which corresponds to the trilayer MoS 2 . The zoomed-in Raman spectra of MArH5 and MArH10 are shown in the inset in Figure a, while for MArH5 and MArH10, the peak difference between E 2g 1 and A 1g peaks has been reduced to 20 cm –1 , indicating the formation of the monolayer film as conventionally used metrics in the reported literature studies …”

“…The in-plane E 2g 1 and the out-ofplane A 1g modes in the Raman spectra show a difference of 22.4 cm −1 for MAr which corresponds to the trilayer MoS 2 . 27 The zoomed-in Raman spectra of MArH5 and MArH10 are shown in the inset in Figure 2a, while for MArH5 and MArH10, the peak difference between E 2g 1 and A 1g peaks has been reduced to 20 cm −1 , indicating the formation of the monolayer film as conventionally used metrics in the reported literature studies. 28 Figure 2b,c displays the AFM images of MAr and MArH10, along with their respective height profiles (across the green line), which reveal height differences of ∼2.1 and ∼0.8 nm between the film's surface and the substrate (discernible through a scratch) for MAr and MArH10, respectively.…”

Graphene-All-Around Cobalt Interconnect with a Back-End-of-Line Compatible Process

“…The time to fail with a probability of 50% (TTF 50% ) was used to evaluate the device lifetime. 47 The TTF 50% of graphene barriers was enhanced from 109 to 642 s (5.9 times) at 6 MV/cm, from 41 to 173 s (4.2 times) at 7MV/cm, and from 13 to 50 s (3.8 times) at 8 MV/cm, showing a significant improvement in the device lifetime. Furthermore, we also achieved direct growth graphene on the dielectric by using HW-CVD in conjunction with ammonia (NH 3 ), as shown in Figure S6.…”

“…Furthermore, due to previous studies that diverge on whether Co interconnects require a diffusion barrier 44,45 or not, 46 the TDDB measurements were conducted to evaluate the graphene diffusion barrier property, serving as a barrier layer in GAA structures, which is a standard test commonly employed to assess the reliability of the gate dielectric in semiconductor devices. 47 The TDDB measurement applied a constant electric field at room temperature across the capacitor structure when graphene was used as a barrier layer; it could reduce the rate of diffusion of the Co ion into the dielectric, thus further enhancing the device lifetime (Figure 3a). The electric field drives Co ions into dielectric, causing accumulation and the formation of the trap-assisted conduction path that leads to device breakdown.…”

“…Additionally, Raman measurements were performed on the breakdown regions, revealing the presence of a significant 2D peak in the graphene even after breakdown, confirming its continued existence after breakdown (Figure S5). Furthermore, due to previous studies that diverge on whether Co interconnects require a diffusion barrier , or not, the TDDB measurements were conducted to evaluate the graphene diffusion barrier property, serving as a barrier layer in GAA structures, which is a standard test commonly employed to assess the reliability of the gate dielectric in semiconductor devices . The TDDB measurement applied a constant electric field at room temperature across the capacitor structure when graphene was used as a barrier layer; it could reduce the rate of diffusion of the Co ion into the dielectric, thus further enhancing the device lifetime (Figure a).…”