The Edge Placement Error (EPE) is growing concerns due to the complexity increases of process variation as the design rule shrinkage of DRAM device. The EPE is a well-accepted metric which can be derived from CD, Overlay and LER measurements from more than patterning layers that concerned. Therefore, real time EPE measurement becomes a major factor to monitor and control the pattern fidelity. The pattern fidelity could be found from the edge placement measurement as a distance to design intent as possible without pattern defects. However, the traditional application of photolithography and etch biases according to a design rule or model for identifying pattern fidelity has inherent low TMU, multiple non consistence data sources and time-consuming off-line analysis. In previous works, we demonstrated the innovative e-Beam EPE metrology application using All-In-One (AIO) methodology to comply the required Total Measurement Uncertainty (TMU) and Time to Result (TTR) on the advanced DRAM nodes. AIO imaging and analysis methodology that deconvolute CD, overlay and relevant EPE metrics from a single see-through image is the most important differentiation for this EPE analysis approach. The in-cell direct EPE measurement with All-In-One (AIO) imaging and massive sampling demonstrates the better process controls and monitoring from the co-optimization of multiple control parameters and direct measurement of the yield relevant metrics. In this paper, we would like to show a couple of EPE monitoring use cases which shows good correlation to the final yield map through the massive and multi-layer measurements. Especially, it is expected that the EPE component which measures the edge-to-edge distance between different features of multi-layers can be a useful indicator for predicting yield along with CD and overlay. To investigate the local and random variabilities, which local stochastic effects are contained, we also studied the degree of yield prediction of the EPE component with increasing number of measurement sites in local area. It is proposed that using a large amount of measurement sites allows to improve the yield prediction accuracy to a certain extent, which means the local stochastic effects can be effectively analyzed with the use of massive metrology approach. In addition, from the prediction accuracy study using EPE model-based machine learning, we proved that the EPE is sufficiently sensitive indicator to capture potential yield-loss problems in normal wafer, as well. Therefore, in-line EPE monitoring using AIO metrology enables the root-cause analysis of patterning weak points and provides a better process monitoring/correction solution to enable faster advanced DRAM node development ramp and high-volume stability.
With the extreme ultraviolet (EUV) lithography and its pitch scaling, the resist shrinkage from electron beam has returned to an important critical dimension (CD) control issue—unlike multi-patterning where the smallest CD is larger than 40nm. The resist height reduces to maintain the aspect ratio below 2:1 which is critical factor for the prevention of the resist collapse. This leads to huge challenges to minimize the shrinkage of resist during the scanning electron microscope (SEM) measurement. Accurate and precise metrology of chemically amplified resist (CAR) type EUV photoresist processed pattern utilizing classical beam energy for lithography pattern such as 500V is great challenging as electron beam exposure of 1st measurement already fully shrunk the pattern. Moreover, occurrence of carbonization along with shrinkage hinders finding best conditions for not only metrology optimization but also minimized process impact. In this work, we evaluated the magnitude of shrinkage of CAR type EUV photoresists with several approaches including 0th and 1st shrinkage estimation utilizing line & space pattern and contact hole pattern as a function of landing energy dose and static/dynamic repeatability method to distinguish behaviors of shrinkage and carbonization by controlling interaction time of photoresist to its environment. One approach to trace minimized 0th shrinkage and metrology uncertainty in lithography process is utilizing 1st shrinkage (1st CD – 2nd CD) analysis together with plotting absolute value of the 1st CD as a function of dose. The other approach to trace optimization condition was comparing exposed area with electron beam and non-exposed area achieved by comparing litho/etch consecutive process on the same area. Furthermore, model fits, a simulation study were also performed.
With the extreme ultraviolet (EUV) lithography and its pitch scaling, the resist shrinkage from electron beam has returned to an important critical dimension (CD) control issue - unlike multi-patterning where the smallest CD is larger than 40nm. The resist height reduces to maintain the aspect ratio below 2:1 which is critical factor for the prevention of the resist collapse. This leads to huge challenges to minimize the shrinkage of resist during the scanning electron microscope (SEM) measurement. Accurate and precise metrology of chemically amplified resist (CAR) type EUV photoresist processed pattern utilizing classical beam energy for lithography pattern such as 500V is great challenging as electron beam exposure of 1st measurement already fully shrunk the pattern. Moreover, occurrence of carbonization along with shrinkage hinders finding best conditions for not only metrology optimization but also minimized process impact. In this work, we evaluated the magnitude of shrinkage of CAR type EUV photoresists with several approaches including 0th and 1st shrinkage estimation utilizing line & space pattern and contact hole pattern as a function of landing energy dose and static/dynamic repeatability method to distinguish behaviors of shrinkage and carbonization by controlling interaction time of photoresist to its environment. One approach to trace minimized 0th shrinkage and metrology uncertainty in lithography process is utilizing 1st shrinkage (1st CD – 2nd CD) analysis together with plotting absolute value of the 1st CD as a function of dose. The other approach to trace optimization condition was comparing exposed area with electron beam and non-exposed area achieved by comparing litho/etch consecutive process on the same area. Furthermore, model fits, a simulation study were also performed.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.