Effects of He Plasma Pretreatment on Low-k Damage during Cu Surface Cleaning with NH[sub 3] Plasma

Abstract

In this study, the effect of the sequential He and NH 3 plasma treatments on a chemical vapor deposition SiOC:H low-k dielectric is evaluated in the wide range of experimental conditions. Results show that the active NH 3 plasma radicals penetrate the porous low-k bulk and remove the hydrophobic Si-CH 3 groups, which leads to hydrophilization and results in the degradation of dielectric properties. The implementation of He plasma pretreatment reduces the damage imposed by the NH 3 plasma by a stimulation of the surface recombination of active radicals from NH 3 plasma. He plasma causes a surface modification of 10-20 nm presumably due to the energy transfer from the extreme UV photons and the 2 1 S He metastable atoms to the low-k structure. The plasma damage reduction is proportional to He plasma density and the treatment time. The mechanism of plasma damage reduction is explained on the basis of the Knudsen diffusion mechanism and random walk theory.

Mechanisms for sealing of porous low-k SiOCH by combined He and NH3 plasma treatment

“…4,5,14 He þ and VUV photons (whose fluxes are also computed in the plasma equipment model) break Si-O bonds and remove H from CH 3 groups lining the pores to create the active sites. 4,5,14 He þ and VUV photons (whose fluxes are also computed in the plasma equipment model) break Si-O bonds and remove H from CH 3 groups lining the pores to create the active sites.…”

“…Cleaning using oxygen containing plasmas is then a trade-off between treatments that are long enough to fully remove the CF x polymer while not producing significant damage to the SiOCH. 4,5,14 Recent experimental results favor the latter mechanism. 4-6 Pretreatment with He plasmas is thought to create active surface sites which localize and accelerate the chemical reactions responsible for pore sealing.…”

“…[3][4][5][6][7] Dielectrics are typically etched in fluorocarbon plasmas in which there is deposition of a CF x polymer. [3][4][5][6][7] Dielectrics are typically etched in fluorocarbon plasmas in which there is deposition of a CF x polymer.…”

The effect of He plasma treatment on properties of organosilicate glass low-k films

“…22 This "stressed" layer is probably more chemically active: this is the reason why the following ammonia plasma treatment can lead to the complete sealing. The energy of He þ ions incident on the film surface was rather low, $25-50 eV only.…”

“…One of the most successful and popular approaches is related to the introduction of a diffusion-recombination model of plasma damage and to the direct measurement of recombination coefficients. For instance, the pretreatment of the lowk surface by He plasma with the following exposure to NH 3 plasma led to sealing the open pores of low-k materials 21,22 although the He plasma itself only partially densified the top layers. Uchida 15 recently reported an interesting study of plasma damage in very-high-frequency capacitively coupled plasma (CCP) reactors.…”