Wu Sun

Yield Enhancement with Optimized Offset Spacer Etch for 65nm Logic Low-leakage Process

This paper presents an effective way to reduce the degradation of the Ring-OSC speed with optimized offset spacer etch, improvement of the within-wafer uniformity of the offset spacer width and the reduction of its profile deviation. We have developed the lower offset spacer etch rate scheme for better control of plasma uniformity in order to achieve the above two targets. Compared with the 3Sigma of 1.3nm offset spacer width uniformity and 1.8nm profile deviation of conventional dielectric etcher with high etch rate, this low etch rate process has delivered the 3sigma of 0.5nm for the offset spacer width uniformity and 0.7nm offset spacer profile deviation. The corresponding Ring-OSC loss has been completely eliminated and the wafer-level yield is enhanced by 40%.

Etch Arts of Dual Damascus Structure and Their Impacts on WAT/VBD in 65nm Cu Interconnects

In this paper, based on the via-first DD technology, we focus on the profile tuning of via and trench and the liner removal in order to optimize the trench profile. Via profile tuning include how to realize the via with the bowling profile, vertical profile and tapering profile. Trench profile tuning emphasizes the formation mechanism of bowling profile and top rounding profile. Footing profile and under-cutting profile of via bottom in liner open step is also addressed. The effect of different etching profiles on Rc, VBD (Breakdown Voltage) are examined. Results show that different via profiles have no impact on Rc, top-rounding trench-profile results in worse VBD, while under-cut & footing liner would deliver lower and higher Rc, respectively.

Mechanism of via etch striation and its impact on contact resistance & breakdown voltage in 65nm cu low-k interconnects

The mechanism of two kinds of via etch striation (type I and type II) has been investigated to improve contact resistance (Rc) uniformity and solve breakdown voltage (VBD) issue in 65 nm Cu low-k interconnects. Heavy etching polymer deposition on the sidewall of capping layer and rapid photo-resist (PR) consumption on PR shoulder are two main resources to result in via etch striation. The effects of both via etch striations on Rc and VBD can be decoupled. Type I striation related to barc open (BO) step leads to worse Rc uniformity while type II striation formed in main etch (ME) and over-etch (OE) step degrades VBD performance.