450mm lithography status for high volume manufacturing

The Global 450mm Consortium (G450C), which is located at the SUNY Poly campus in Albany, NY was created to develop and evaluate a manufacturing tool set for 450mm wafers. The Lithography cell at G450C consists of a Nikon NSR-S650D 193nm immersion scanner and a SCREEN SOKUDO DUO DT-4000 track. The Lithography cell was installed and qualified in 2015, and with over a year of tool availability we have been able to perform extensive testing on the system to determine the equipment readiness for volume manufacturing. For the purposes of this paper we are focusing on the Edge Placement Error (EPE) [1] contributors of Critical Dimension Uniformity (CDU) and Overlay [2]. We will show the initial results as well as the improvements that have been made since tool acceptance. The 450mm results will be compared to 300mm tools in production today, as well as against the seven nanometer node (N7) expected requirements. Lastly, we plan to demonstrate the Nikon scanner's ability for focus control on stressed or bowed wafers, which are characteristic challenges of large silicon substrates. This paper will showcase the current 450mm lithography performance for CDU on both Line/Space (LS) and Contact Hole (CH) patterns. We will demonstrate the process window for LS and CH features on multiple resists specially formulated for 450mm. Both Post Exposure Bake (PEB) tuning on the SCREEN track as well as CDU Master (CDUM) Corrections from the Nikon Turnkey Solution software suite will be utilized for performance improvements on 450mm wafers. The G450C goal is to drive CDU down to less than 1nm 3s across the entire wafer with 1.5mm edge exclusion zone." In addition to our test masks, G450C has designed a three layer mask set and with these masks we gathered "on product" CDU performance on a Back End Of Line (BEOL) metal stack. In the current reality of high volume manufacturing, multi-patterning is used to achieve the required Critical Dimension (CD) and pitch combination. The largest contributor to EPE is scanner overlay performance. We will demonstrate the Single Machine Overlay (SMO) performance as well as some Mix and Match Overlay (MMO) results. The lithography cell at G450C is the only 450mm linked lithography cell in the world. In order to create MMO wafers we were required to expose the first print at the Nikon factory in Japan and etch them at G450C to generate an align-to layer. As the wafers' size scales, so do some of the process effects including film stress and wafer bow. The current G450C BEOL integrated process has measured wafer bow of up to 350um. We will demonstrate how the S650D measures the wafer topography and adjusts the exposure to compensate for wafer bow.