A powerful new inspection technology enables the excursion control of fast patterning processes. Full images of 300mm
wafers are captured and processed to extract CD uniformity information of contact hole and line-space patterns. Suitable
masking filters are applied to process and analyze the information from active logic and/or memory areas separately.
Characteristic process tool signatures can then be detected based on die, exposure field and wafer-level pattern variations.
Based on inspection times of a few seconds per wafer, rapid monitoring of 100% of processed wafers at full surface is
feasible. CD-imaging is demonstrated for the monitoring of key patterning process steps in gate formation. Use cases for
stand-alone, integrated and smart sampling strategies are discussed.
Wafer Current Measurement (WCM) is an emerging technique for in-line process monitoring. A joint development project (JDP) has been conducted by Infineon Technologies and Applied Ma-terials (Process Diagnostics and Control Group). The main goal of this project was development of applications for the WCM technique in production environment and specifically for state of the art DRAM Infineon process. A new generation of SEM review tool with integrated FIB (Ap-plied SEMVision G2 FIB Defect Analysis system) was used for this work. A challenging layer approached in this work was the DTMO (Deep Trench Mask Open) which serves as a hard mask for subsequent deep trench (DT) capacitor formation in a silicon substrate. The aspect ratio of the openings in the DTMO layer can be as high as 20:1. As a result of the aggressive aspect ra-tio and sub-100 nm CDs the only available techniques for evaluating DTMO etch integrity (pos-sible under-etch and/or bottom CD variation) are destructive analysis methods. As a result of the extensive JDP, crucial yield limiting problems such as dielectric or/and stop layer under-etch as well as bottom CD violation have been revealed by the WCM in-line rather than by cross-sectioning in failure analysis laboratory or other destructive means. Besides, on the basis of bottom CD sensitivity of the WCM technique, etch chamber qualification (including matching and adjustment) feasibility was conducted. The motivation behind this is that chamber qualification is essential to shorten cycle time. In production environment the WCM technique is targeted for two basic applications: process monitoring including excursion control and early etch process drift warning and in-line etch chamber qualification. WCM "pilot" has been performed in production after DTMO for four novel DRAM products with CD down to 70 nm.
Infrared spectroscopic ellipsometry (IRSE) metrology is an emerging technology in semiconductor production environment. Infineon Technologies SC300 implemented the first worldwide automated IRSE in a class 1 clean room in 2002. Combining properties of IR light -- large wavelength, low absorption in silicon -- with a short focus optics -- no backside reflection -- which allow model-based analysis, a large number of production applications were developed. Part of Infineon IRSE development roadmap is now focused on depth monitoring for arrays of 3D dry-etched structures. In trench DRAM manufacturing, the areal density is high, and critical dimensions are much lower than mid-IR wavelength. Therefore, extensive use of effective medium theory is made to model 3D structures. IR-SE metrology is not limited by shrinking critical dimensions, as long as the areal density is above a specific cut-off value determined by trenches dimensions, trench-filling and surrounding materials. Two applications for depth monitoring are presented. 1D models were developed and successfully applied to the DRAM trench capacitor structures. Modeling and correlation to reference methods are shown as well as dynamic repeatability and gauge capability results. Limitations of the current tool configuration are reviewed for shallow structures.