Damage to low-k porous organosilicate glass from vacuum-ultraviolet irradiation

Abstract

We investigate the effects of VUV and UV radiation on a number of low-k dielectric films. Two different systems were used to investigate the effects: (1) a synchrotron radiation system as a pure VUV radiation source, and (2) an electron-cyclotron resonance (ECR) plasma system as a plasma source (VUV plus ions). Using the synchrotron-radiation system, we find VUV causes trapped charge accumulation within low-k dielectric films by electron depopulation from the defect states. For organosilicate glass (SiCOH) , the defect states were located 1 eV above the valence band of the dielectric. A model was developed to calculate in-situ charge accumulation. Trapped charges can be depleted with UV-lamp exposure. We examined the use of different energy barriers between layers so that less charge will be accumulated. Using the ECR plasma system, the photon effects can be separated from charged particle effects using a capillary-array window to cover the low-k dielectric films so that only photons from plasma can reach the dielectric. Photon fluence from the plasma can be predicted with a model and measured with a VUV monochromator. Photons from the plasma were shown to be responsible for trapped-charge accumulation within the dielectric, while it was found that ions bombardment results primarily on charge on the surface of the dielectrics.

Area-Selective Molecular Layer Deposition of a Silicon Oxycarbide Low-k Dielectric

“…However, further optimization, such as tuning the chemical composition and film density, could potentially reduce the k value of the SiOC films down to 2.5 as previously reported . Compared to the siloxane-type low- k materials deposited by CVD, the MLD SiOC film has noticeably higher hysteresis (∼900 and ∼2700 mV for 8.8 and 28.1 nm samples, respectively) and leakage current (1.4 × 10 –6 and 6.3 × 10 –7 A cm –2 at −1 MV cm –1 for 8.8 and 28.1 nm samples, respectively; curves not shown), implying a high trap density. The higher hysteresis for the thicker film could be attributed to an increase in the trapped oxide charges inside the SiOC films because of the increased thickness.…”

Real-time VUV radiation monitoring in low-pressure hydrogen plasma based on fluorescence of sodium salicylate

“…Recently, surface interactions between high-energy photons, such as vacuum ultraviolet (VUV) and/or ultraviolet (UV), and various polymeric substrates, photoresists and low-k materials, have attracted strong interest. While VUV/UV photons can have a beneficial impact for some applications, in some cases VUV presence can lead to drawbacks such as surface-induced damage [2][3][4][5][6]. For example, UV photons in the wavelength (λ) region of (200-400) nm are used for UV curing, crucial for the fabrication of low-k materials with good mechanical properties [3].…”

“…crystalline SiO 2 and organosilicate glass) with an absorption edge above 8 eV, which leads not only to low-k material bond cleavage but also to charge trapping at defect sites [5]. As a result, undesirable damage, such as poor mechanical property, RC delay, low breakdown voltage and leakage currents, is induced on the low-k inter-metal dielectrics [4][5][6][7]. Therefore, quantifying the plasma VUV/UV photon radiation is crucial to understand and predict the VUV/UV-induced effects during semiconductor manufacturing.…”