Resist Poisoning Studies of Gap Fill Materials for Patterning Metal Trenches in Via-First Dual Damascene Process

Abstract

The via-first dual damascene process is the current manufacturing technology for copper/low-k interconnect fabrication. In the conventional via-first dual damascene process, metal trench patterning lithography is applied after filling the vias with sacrificial organic materials under the resist, such as gap fill materials and bottom antireflective coating. Resist poisoning has become a serious problem for the 65 nm technology node and beyond owing to the use of porous low-k dielectric materials. This study describes the newest method of evaluating resist poisoning. The dependence of film thickness on resist poisoning was observed, and the effects of the gap fill materials with different polymers were also clarified. One gap fill material was found to have an excellent resist poisoning blocking property as determined from the bias of trench patterning size between the center and edge areas. In addition, to evaluate the resist poisoning in lithography, a chemical approach using the developed gap fill materials can potentially allow the skipping of the additional thermal annealing process and achieve high throughput wafer processing by only coating the gap fill material on the substrates that generate resist poisoning. Continuing the via-first dual damascene process using porous low-k dielectric materials in an advanced lithography will be valuable in future studies based on this evaluation method, compared with the trench-first dual damascene process owing to the higher cost of the latter.

Dielectric Barrier, Etch Stop, and Metal Capping Materials for State of the Art and beyond Metal Interconnects

“…20,21 Resist poisoning.-"Resist poisoning" is a phenomenon where photoresist patterns generated in an optical lithography process are not precisely formed as intended. 91 One mechanism largely believed to lead to resist poisoning in low-k/Cu interconnect patterning is a reaction between the photoresist and residual amines (NH 3 ) in the low-k ILD that prevents the photoresist from developing properly. 91,92 Based on this mechanism, an additional integrated requirement for low-k DB materials is to prevent amines present in underlying metal layers from outgassing into the top metal layer being patterned.…”

“…91 One mechanism largely believed to lead to resist poisoning in low-k/Cu interconnect patterning is a reaction between the photoresist and residual amines (NH 3 ) in the low-k ILD that prevents the photoresist from developing properly. 91,92 Based on this mechanism, an additional integrated requirement for low-k DB materials is to prevent amines present in underlying metal layers from outgassing into the top metal layer being patterned. This requirement also implies that the low-k DB may not be a source of amines.…”

Review of methods for the mitigation of plasma‐induced damage to low‐dielectric‐constant interlayer dielectrics used for semiconductor logic device interconnects

“…Third, trench patterning is used to form a stack of a spin‐on‐glass (SOG) layer and a top resist layer. The SOG mask controls the etching amount of the bottom resists in via holes . To achieve the better‐patterned shape, a tri‐layer consisting of a top layer of thin resist for patterning, a SOG interlayer, and a spun‐on carbon (SOC) film bottom layer was introduced in DD schemes, called a stacked mask process (S‐MAP) .…”

Process Technology for Copper Interconnects

“…In contrast, for the via-first process, the via lithography is relatively simple, but the trench etch is difficult [33,34]. The organic ARC layer planarizes the topography from the vias, protects the etch stop layer from erosion during the trench etch, and can help prevent resist poisoning, by slowing down amine diffusion in the resist [37][38][39]. An organic anti-reflective coating (ARC) is generally used during trench lithography ( Figure 8.6B) [37].…”

“…During the trench lithography process, amines in the dielectric stack can diffuse from the vias into the deep UV resist during bakes and neutralize the photo-acid catalyst [38,39]. A fence can form around the via in a via-first process in two different ways.…”