The fabrication of sigma-shaped silicon recess normally consists of dry etch process to shape the silicon trench and post etch treatment to form the sigma-shaped cavity within bulk silicon substrate. Here we are dedicated to the optimization of silicon recess dry etch process and its effect on the final sigma-shaped SiGe physical performance. Results show the isotropic ratio of horizontal over vertical direction could be doubled. This caters much larger process window for the desired strain introduction at the hetero-junction of SiGe/Si. Besides, the corresponding dry etching solutions are also disclosed from the point of view of tip depth adjustment and tip horizontal pull-back control. Both physical indexes could be independently controlled to deliver the required sigma-shaped Si recess trench.

As CMOS technology has been continuously scaling down and the dual-stress liner scheme is introduced for simultaneous stress enhancement of both n-MOS and p-MOS, contact etch has started to act as a critical role for the robust performance of integrated circuit. In this work, we investigated the impact of dry etching process on contact hole profile. Results demonstrate the overall contact hole profile can be rigorously controlled if the radio frequency (rf) powers and etching chemistries in inter layer dielectric (ILD) etch step are well balanced. Free local pull-back at contact hole sidewall has to leverage the optimization of etch selectivity of silicon nitride over silicon oxide in liner removal step. Besides, the post etch treatment (PET) is also proven to be imperative for the process window enhancement for such pull-back reduction.

High-K metal gate (HKMG) approach has been introduced to enhance the device performance via lowering device current leakage. Dummy poly gate removal (DPGR) process is introduced in HKMG process to form the metal gate with different work functions for n/p-MOS. However, the introduction of this technology does pose many new challenges to various fabrication processes, especially for etch process at 14nm node and beyond. In FinFET technology, ploy-si is removed simultaneously for both n-MOS and p-MOS. normally, the partial dry etch and partial wet etch scheme is adopted for less plasma damage. This paper will introduce full dry etch process to complete poly-si removal. This definitely requires soft etch process to avoid the damage of Fin top and channel while meeting all the physical targets.

This work mainly focuses on the post-etch treatment (PET) in dielectric etch processes from contact etch, trench etch to all-in-one etch. PET step is optimized not only to efficiently remove the byproducts formed on the sidewall/bottom of contact/via hole during etch proceses but also to eliminate the surface corrosion of the etched metal comprising feature. Besides, we also leveraged PET to repair low-k damage and prevent the formation of mositure on film surface by modifing film from hydrophilic to hydrophobic, especially for low-k/ultra low-k dielectric processes. Results show the actual effect of PET in terms of reliability performance highly relies on the specific etch recipe, wet clean condition and substrate material in back end of line (BEOL). We also addressed the pre-etch treatment to effectively reduce the impact of photo-resist scumming in contact etch. In brief, plasma-based etch treatment is imperative to extend the tightened process window margin.

OCD metrology has been proven to be a fast, accurate, and non-destructive knob for in-situ monitoring of line width and profile. In order to main Moore's law, device dimension is moving towards 45nm technology node and beyond, it is becoming increasingly difficult to perform the in-situ evaluation for those complicated structures by either CD-SEM or AFM. In this work, we come up with one specific 3D pattern to realize the 3D monitoring of p-MOS silicon recess (PSR) etch performance. The corresponding OCD library was identified and implemented on Nova OCD 3090 next. Several key floating parameters include PSR & STI depth, gate & AA CD, nitride spacer width and SWA. Good CD correlation between OCD and CD-SEM is obtained on the same 3D pattern. Consistent trench depth match is also observed between OCD and blanket pattern based AFM. Besides, dynamic repeatability test shows the acceptable reliability for 3D PSR OCD monitoring as well.