Absolute intensities of the vacuum ultraviolet spectra in oxide etch plasma processing discharges

Abstract

@In this paper, we report the absolute intensities of ultraviolet light between 4.9 eV and 24 eV ( 250 m-n to 50 mn ) striking a silicon wafer in a number of oxide-etch processing discharges. Our emphasis is on photons with energies greater than 8.8 eV, which have enough energy to damage Si02. These discharges were in an inductively-driven Gaseous Electronics Conference reference cell which had been modified to more closely resemble commercial etching tools. Comparisons of measurements made through a side port in the cell and through a hole in the wafer indicate that the VUV light in these discharges is strongly trapped. For the pure halocarbon gases examined in these experiments ( CzF& CHF3, C4F8 ), the fluxes of VUV photons to the wafer varied fi'om 1 x 1015 to 3 x 1015photons/cm2sec or equivalently from 1.5 to 5 mW/cm2. These measurements imply that O.10/0to 0.3 0/0 of the rf source power to these discharges ends up hitting the wafer as VUV photons for our typical 20 mT, 200 W rf discharges. For typical "ashing" discharges containing pure oxygen, the VUV intensities are slightly higher -about 8 mW/cm2 . As argon or hydrogen diluents are added to the fluorocarbon gases, the VUV intensities increase dramatically, with a 10/1 0/1 Omixture of Ad C2F~H2yielding VUV fluxes on the wafer 26 mW/cm2 and pure argon discharges yielding 52 mWlcm2 . Adding an rf bias to the wafer had only a small effect on the VUV observed through a side-port of the GEC cell.

Time-dependent dielectric breakdown of plasma-exposed porous organosilicate glass

“…5 During plasma processing, both ion bombardment and vacuum ultraviolet (VUV) irradiation can occur. [6][7][8][9] Defect states (and subsequent trapped charge) generated by both VUV irradiation and charged-particle bombardment of low-k dielectrics have been shown to adversely affect the capacitance, 10-12 breakdown voltage, 13 and leakage currents 14,15 in addition to causing chemical and structural changes 16 in organosilicate dielectrics. In this letter, it is shown that both photons and charged particles emitted during plasma processing have a deleterious effect on the time to dielectric breakdown, i.e., the dielectric lifetime.…”

Surface potential measurements of vacuum ultraviolet irradiated Al/sub 2/O/sub 3/, Si/sub 3/N/sub 4/, and SiO/sub 2/

“…Charge separation causes the dielectric to become polarized, which also contributes to the surface potential of the dielectric. To separate the damage effects, plasma-generated VUV radiation from charged-particle bombardment, we used monochromatic synchrotron radiation in the same photon energy range that is typically found in most processing plasmas [1]- [3]. The synchrotron source at the University of Wisconsin, Madison was used as a source of VUV photons to expose unpatterned dielectric-coated wafers.…”

The efficacy of post porosity plasma protection against vacuum-ultraviolet damage in porous low-k materials

“…For these reasons, very little relevant data on this topic can be found. 21,22 According to Woodworth et al, the dominant emission lines in the v-UV region with our plasma etching process (CF 4 /CH 2 F 2 /Ar) likely originate from argon emission at 105 nm and hydrogen emission at 103 nm and 122 nm. In addition, fluorine emission lines at 79 nm and 98 nm, fluorocarbon emission lines (above 190 nm), and carbon emission lines spread throughout the whole spectrum are also expected to significantly contribute to the plasma emission in the v-UV.…”

“…In addition, fluorine emission lines at 79 nm and 98 nm, fluorocarbon emission lines (above 190 nm), and carbon emission lines spread throughout the whole spectrum are also expected to significantly contribute to the plasma emission in the v-UV. 22 With regards to O 2 plasma, the major emission lines are expected from oxygen around 130 nm. For both plasma processes, additional emission lines at lower wavelengths may be present but have not been observed experimentally during plasma etching.…”