Plasma damage mechanisms for low-k porous SiOCH films due to radiation, radicals, and ions in the plasma etching process

Abstract

Low dielectric constant (low-k) films have been widely used as insulating materials in ultra-large-scale integrated circuits. Low-k films receive heavy damage during the plasma processes of etching or ashing, resulting in an increase in their dielectric constant. In order to realize damage-free plasma processes for low-k films, it is essential to determine the influence of radiation, radicals, and ions emitted in the plasma process on the characteristics of low-k films. We have developed a technique to evaluate the influence of radiation, radicals, ions, and their synergies on films in real plasma processes and have named it pallet for plasma evaluation (PAPE). Using the PAPE, plasma-induced damage on porous SiOCH films were investigated in dual-frequency capacitively coupled H2∕N2 plasmas. The damage was characterized by ellipsometry, Fourier-transform infrared spectroscopy, and thermal desorption spectroscopy. On the basis of the results, the damage mechanisms associated with vacuum ultraviolet (VUV) and UV radiation, radicals, and ions were clarified. The damage was caused not only by ions and radicals but also by VUV and UV radiation emitted by the plasmas. Moreover, it was found that the synergy between the radiation and the radicals enhanced the damage.

Optical and electrical characterization methods of plasma-induced damage in silicon nitride films

“…5) In the case of the plasma-induced physical damage (PPD), it creates local defect structures in materials such as vacancies and interstitials. These damage structures are considered to behave as carrier-trapping sites, thus, result in the changes in the dielectric constant ε and the capacitance C. Regarding the PID to dielectric materials, the previous studies showed that the PID to "low-k" films -interlayer dielectric materials -led to changes in ε 6,7) and C. 8,9) Shinohara et al investigated 10) the time evolution of leakage current flowing through dielectric materials under constant voltage stressing for the evaluation of PID in thick SiO 2 films. They found that the initial electron trapping rate depends on the amount of PID.…”

Dielectric Recovery of Plasma Damaged Organosilicate Low-k Films

“…During plasma etching and ashing processes, carbon depletion, surface hydrophilisation, and surface densification have been observed, increasing the effective dielectric constant and leakage current [3][4][5][6][7][8][9][10][11]. These plasma damages limit the further scaling of low-k structures and have stimulated considerable interests in the study of dielectric recovery by silyation methods, using vapor-phase [12], liquidphase [13][14], and supercritical CO 2 processes [15][16][17].…”

Optical Observation of Deep Bulk Damage in Amorphous Perfluorocarbon Films Produced by UV Photons Emitted from Low-Pressure Argon Plasma

“…As with electrical charge-up and ion bombardment, photons in the UV and especially in the vacuum ultraviolet (VUV) regions emitted from plasma also induce damage on device materials [9][10][11][12][13][14][15][16][17]. Although the number of reports on UV-induced damage in LSI fabrication is much smaller than those on damage induced by electrical charge-up and ion bombardment, the recent increase in the use of organic materials in electronic devices, e.g., for low-k dielectric barrier and flexible semiconductors, has highlighted the ever-growing importance of the study on UV-induced damage in plasma processing.…”