Heng-Hsin Liu

A paradigm shift in scatterometry-based metrology solution addressing the most stringent needs of today as well as future lithography

Advanced lithography is becoming increasingly demanding when speed and sophistication in communication between litho and metrology (feedback control) are most crucial. Overall requirements are so extreme that all measures must be taken in order to meet them. This is directly driving the metrology resolution, precision and matching needs in to deep sub-nanometer level as well as driving the need for higher sampling (throughput). Keeping the above in mind, a new scatterometry-based platform (called YieldStar) is under development at ASML. Authors have already published results of a thorough investigation of this promising new metrology technique which showed excellent results on resolution, precision and matching for overlay, as well as basic and advanced capabilities for CD. In this technical presentation the authors will report the newest results taken from YieldStar. This new work is divided in two sections: monitor wafer applications and product wafer applications. Under the monitor wafer application: overlay, CD and focus applications will be discussed for scanner and track hotplate control. Under the product wafer application: first results from integrated metrology will be reported followed by poly layer and 3D CD reconstruction results from hole layers as well as overlay-results from small (30x60um), process-robust overlay targets are reported.

Phase shift focus monitor for OAI and high NA immersion scanners

Phase Shift Focus Monitor (PSFM) has been successfully utilized as a focus monitoring tool for scanners and steppers from the g-line era to the most advanced immersion technology nodes. PSFM exhibits high sensitivity, linearity and repeatability for immersion scanners with the illumination conditions of conventional mode and NA0.93. A microlithography model was created using Hyperlith to study the PSFM sensitivity and linearity under the conditions of OAI (off-axis illumination) and high NA (0.95~1.35). The model predicts that a PSFM sensitivity of 700 ~ 1000 nm/um can be achieved when an OAI, 40 nm PSFM target and NA 1.35 are used. The model also studied the influence of various parameters on PSFM sensitivity and linearity. Wafer data verified the simulation results. PSFM linear focus range with the NA1.35 condition is shorter than that of NA0.93. The influence of illumination conditions on PSFM, such as OAI modes (annular, Quadra), NA / Sigma values and PSFM target sizes, has also been investigated by the microlithography model.

Estimation of 1D proximity budget impacts due to light source for advanced node design

The laser impacts on the proximity error are well known in many previous studies and papers. The proximity budget control is more and more important for advanced node design. The goal of this paper is to describe the laser spectral bandwidth and wavelength stability contributions to the proximity budget by considering general line/space and trench pattern design. We performed experiments and modeled the photolithography response using Panoramic Technology HyperLith simulation over a range of laser bandwidth and wavelength stability conditions to quantify the long term and short term stability contributions on wafer-to-wafer and field-to-field proximity variation. Finally, we determine the requirements for current system performance to meet patterning requirements and minimize the laser contribution on proximity error and within 4% of target CD Critical Dimension Uniformity (CDU) budget process requirement [2]. This paper also discusses how the wafer lithography drivers are enabled by ArFi light source technologies.