Impact of VUV photons on SiO2 and organosilicate low-k dielectrics: General behavior, practical applications, and atomic models

Abstract

This paper presents an in-depth overview of the application and impact of UV/VUV light in advanced interconnect technology. UV light application in BEOL historically was mainly motivated by the need to remove organic porogen and generate porosity in organosilicate (OSG) low-k films. Porosity lowered the film's dielectric constant, k, which enables one to reduce the interconnect wiring capacitance contribution to the RC signal delay in integrated circuits. The UV-based low-k film curing (λ > 200 nm) proved superior to thermal annealing and electron beam curing. UV and VUV light also play a significant role in plasma-induced damage to pSiCOH. VUV light with λ < 190–200 nm is able to break Si-CH3 bonds and to make low-k materials hydrophilic. The following moisture adsorption degrades the low-k properties and reliability. This fact motivated research into the mechanisms of UV/VUV photon interactions in pSiCOH films and in other materials used in BEOL nanofabrication. Today, the mechanisms of UV/VUV photon interactions with pSiCOH and other films used in interconnect fabrication are fairly well understood after nearly two decades of research. This understanding has allowed engineers to both control the damaging effects of photons and utilize the UV light for material engineering and nanofabrication processes. Some UV-based technological solutions, such as low-k curing and UV-induced stress engineering, have already been widely adopted for high volume manufacturing. Nevertheless, the challenges in nanoscaling technology may promote more widespread adoption of photon-assisted processing. We hope that fundamental insights and prospected applications described in this article will help the reader to find the optimal way in this wide and rapidly developing technology area.

Charge Transport Mechanism and Trap Origin in Methyl‐Terminated Organosilicate Glass Low‐κ Dielectrics

“…These and other UV radiation–related phenomena were described and discussed in many original publications, which have been systemized and analyzed in detail in a recently published review article. [ 18 ] Finally, to summarize available experimental data, different leakage current enhancement mechanisms can be considered. The task of analyzing the mechanism becomes even more complicated when using UV curing, as well as in the presence of different carbon groups in the dielectric.…”

Use of a Thermally Degradable Chemical Vapor Deposited Polymer Film for Low Damage Plasma Processing of Highly Porous Dielectrics

“…Bulk and near-surface must be considered differently. It is known that the penetration depth of VUV photons in porous OSG low- k varies from ∼50–60 nm at λ ≤ 120 nm to ∼120 nm at λ = 180 nm, i.e., deep into the sample. Although it has been demonstrated that various polymers can capture VUV photons, , only part of the flux is absorbed by the filler.…”

Review on vacuum ultraviolet generation in low‐pressure plasmas

“…[ 17 ] Generally, in the case of low‐ k dielectrics, used in the semiconductor industry and processed in plasma, VUV photons can induce photoconduction, photoemission, and photoinjection, all of which can generate trapped charges within the dielectric and degrade electrical properties of the dielectric. [ 18 ] For more information on the impact of VUV photons on low‐ k dielectrics, we recommend a recent review by Baklanov et al [ 19 ]…”

“…[17] Generally, in the case of low-k dielectrics, used in the semiconductor industry and processed in plasma, VUV photons can induce photoconduction, photoemission, and photoinjection, all of which can generate trapped charges within the dielectric and degrade electrical properties of the dielectric. [18] For more information on the impact of VUV photons on low-k dielectrics, we recommend a recent review by Baklanov et al [19] The VUV radiation is not often reported in the scientific literature on plasma treatment of solid materials. Plasmas are often characterized by simple spectrometers, which will not detect the VUV radiation.…”