Mitigation of plasma-induced damage in porous low-kdielectrics by cryogenic precursor condensation

Synergistic effect of VUV photons and F atoms on damage and etching of porous organosilicate films

“…Nowdays, the most popular approaches are based on temporary densification of low‐k dielectrics by filling of the open pores with sacrificial materials. These approaches are known as post integration porogen removal (PIPR) when porogen is removed after the complete patterning and metallization, as well as post porosity plasma protection (P4) when the already formed pores are filled with sacrificial materials, and cryogenic etch when the low‐k dielectric is protected against the plasma damage by reaction products condensed in the pores . These methods have been targeted to avoid penetration of active species into low‐k dielectrics through the interconnected pores.…”

Damage-free plasma etching of porous organo-silicate low-k using micro-capillary condensation above −50 °C

“…Despite these studies, which led to a better understanding of plasma-ULK interactions, at present no simple way has been found to totally avoid plasma damage of the low-k during plasma etching. Many low damage options have been explored up till now 3 , 13 – 17 . The first type of approach consists of repairing the organo-silicate material after the etching process, through in-situ CH 4 plasma 18 or subsequent sylilation 13 Some restoration may be obtained, but it is partial and is typically restricted to a few nanometers, leading to residual bulk damage.…”

Mechanisms for plasma cryogenic etching of porous materials

“…[1][2][3][4][5] However, a lower dielectric constant normally requires increased pore size and interconnectivity, which will induce a high sensitivity to plasma processing, as radicals and ions can easily penetrate into the interconnected pores, causing severe damage and degrading the dielectric properties. [6][7][8][9][10][11] Especially when the feature dimensions drop to 14 nm, 12 the damage depth can be comparable with the narrow trench structures, [13][14] which will result in a significant degradation of the low-k material quality and a non-optimal isolation of adjacent metal lines. Therefore, protection of porous material becomes crucial during plasma processing.…”

“…[16][17][18][19] By filling the pores with polymer material, the penetration of radicals can be impeded, allowing the protection of the porous material. Compared to traditional pore stuffing approaches with pore stuffing and de-stuffing processes, an alternative protection approach, still at the research phase, was recently proposed, 14 and it also shows high potential for limited plasma induced damage (PID) during plasma etching. By cooling the wafer to cryogenic temperature in fluorocarbon based gas (e.g., C 4 F 8 , C 6 F 6 ) before plasma processing, this gas may condense in the pores as liquid, which can prevent the diffusion of radicals in the interconnected pores during the subsequent plasma etching.…”

“…The EDL decreases monotonously upon lower chuck temperature below -80 °C (i.e., the temperature at which C4F8 starts condensing 14 ) because C4F8 condenses inside the pores, which significantly reduces the number of penetration channels between the pores. The EDL values from both experiments and simulation become extremely small when the temperature approaches -110 °C.…”