Mask Registration Metrology Systems
The LMS IPRO5 mask registration metrology system is designed to ensure that pattern placement on the mask is highly accurate and repeatable, down to the 20nm half-pitch node. At the 20nm node, most critical layers will be manufactured using double patterning lithography (DPL). DPL requires two masks to create one wafer layer, either interweaving the mask patterns or using the second mask to specify cuts in the first mask’s pattern. Triple- or quadruple-mask patterning technology is also being explored.
With double (or multiple) mask patterning lithography, the layer’s CD and overlay error allowances on the wafer must be divided between the two (or more) patterning steps. Because mask pattern placement error (PPE) contributes directly to wafer CD and overlay error, requirements for mask PPE must tighten considerably wherever multiple mask patterning lithography is used. The LMS IPRO5 mask registration metrology system is designed to ensure that all masks meet industry requirements for pattern placement accuracy down to the 20nm node. In addition, the LMS IPRO5 mask registration metrology system is ready for EUV development.
Based on the industry-proven IPRO platform, the LMS IPRO5 mask registration metrology system achieves its industry-leading performance by incorporating several new or improved features:
Mask process development and monitoring: LMS IPRO5 is the only mask registration metrology system to offer flexible, automated in-die metrology, industry-leading performance, and the ability to take through-pellicle measurements. In addition, the LMS IPRO5 mask registration metrology system's reticle data can be directly uploaded to the industry-leading K-T Analyzer software to assess the mask’s contribution to wafer overlay error.
Mask writer qualification and monitoring: Today’s mask writers are able to incorporate sub-nm pattern placement corrections, but to take advantage of this capability, pattern placement error must be measured with high sampling frequency. The LMS IPRO5 mask registration metrology system supplies the automation, performance and analytical software needed to fully characterize a test mask’s or production mask’s pattern placement error, to maximize and monitor the performance of the mask writer, so that fewer problems are discovered at outgoing quality control (OQC).
Mask OQC: Mask OQC: When a mask is shipped, many IC fabs now require that a densely sampled registration plot is provided along with the mask, not just a 3 sigma value. A single number to characterize a mask is no longer sufficient, given the tight specifications driven by today’s challenging lithography technologies. Likewise, an undersampled mask can harbor an unrecognized pattern registration excursion—which can result in a major yield hit for the IC fab. The LMS IPRO5 mask registration metrology system delivers all of the tools needed for a mask manufacturer to provide a fully characterized mask to the fab on schedule—and for both the mask shop and fab to have confidence that the mask is good.