As process technology progresses beyond the 7 nm node, the critical dimension uniformity (CDU) requirement is now in the sub-1 nm regime due to patterning complexity or smaller patterning size. In this report, across-wafer CDU improvement by etch tool correction using the Hydra uniformity system in an advance Lam Research etch tool for a 7 nm FEOL logic application is discussed. The results show that CDU is improved by 60% compared to baseline performance of 3σ < 1 nm, and the post etch CDU is comparable to the ultimate target CDU of post EUV litho development. In conclusion, superior post-etch across-wafer CDU is achieved using the Hydra uniformity system by correcting local non-uniformity after the radial contribution is reduced by traditional multizone ESC tuning.
As feature critical dimension (CD) shrinks towards and beyond the 7nm node, patterning techniques for optical lithography with double and triple exposure will be replaced by EUV patterning. EUV enables process and overlay improvement, as well as a potential cost reduction due to fewer wafer passes and masks required for patterning. However, the EUV lithography technique introduces newer types of resists that are thinner and softer compared to conventional 193nm resists currently being used. The main challenge is to find the key etch process parameters to improve the EUV resist selectivity, reduce LER and LWR, minimize line end shrink, improve tip-to-tip degradation, and avoid line wiggling while still enabling previous schemes such as trench-first-metal-hard-mask (TFMHM), self-aligned via (SAV) and self-aligned contact (SAC).
In this paper, we will discuss some of the approaches that we have investigated to define the best etch process adjustments to enable EUV patterning. RF pulsing is one of the key parameters utilized to overcome most of the previously described challenges, and has also been coupled with stack optimization. This study will focus on RF pulsing (high vs. low frequency results) and bias control (RF frequency dependence). In particular, pulsing effects on resist morphology, selectivity and profile management will be reported, as well as the role of aspect ratio and etch chemistry on organic mask wiggling and collapse.
This work was performed by the Research Alliance Teams at various IBM Research and Development Facilities.