Qualification of aerial image 193nm inspection tool for all masks and all process steps

Aerial image mask inspection tools are effective in qualifying masks based upon printability assessments using scanner-based actinic (193nm) illumination conditions. Aerial imaging inspection application is relevant for masks that are at final process steps or resemble a completed mask. However, maskshops perform inspections at additional, intermediary, mask manufacturing stages, as well as on masks designed for 248nm scanners. In both of these cases, aerial image inspection using scanner-based actinic (193nm) illumination conditions was not considered relevant. This paper demonstrates that aerial imaging inspection tools can be easily configured to perform inspections using various non-aerial illumination modes, owing to their inherently flexible optical design. Aerial image mask inspection tools, running in these optical modes, are effective for detecting defects at various stages of the mask manufacturing process and even for inspecting 248nm masks. Accordingly, MP Mask has adopted the first and second generation aerial imaging mask inspection tools of Applied Materials for all of the following applications: Advanced front end reticle qualification, low and high transmission PSM masks, and immersion and non-immersion plates from 65nm to 45nm technology nodes for DRAM and flash products. A simple cost of ownership comparison of aerial image mask inspection tools with traditional inspection methodology indicates that these inspection tools are well-qualified for use on a wide spectrum of masks and process points. This paper presents qualification procedures and results obtained with this new tool based on a set of masks representing several exposure wavelengths, mask types, technology nodes, product families, and inspection points.