Image-based overlay measurement using subsurface ultrasonic resonance force microscopy

Image-based overlay measurement using subsurface ultrasonic resonance force microscopy

Tamer, M.S.
van der Lans, M.J.
Sadeghian Marnani, H.

Ukraintsev, V.A. (editor)
Adan, O. (editor)

2018

Image Based Overlay (IBO) measurement is one of the most common techniques used in Integrated Circuit (IC) manufacturing to extract the overlay error values. The overlay error is measured using dedicated overlay targets which are optimized to increase the accuracy and the resolution, but these features are much larger than the IC feature size. IBO measurements are realized on the dedicated targets instead of product features, because the current overlay metrology solutions, mainly based on optics, cannot provide sufficient resolution on product features. However, considering the fact that the overlay error tolerance is approaching 2 nm, the overlay error measurement on product features becomes a need for the industry. For sub-nanometer resolution metrology, Scanning Probe Microscopy (SPM) is widely used, though at the cost of very low throughput. The semiconductor industry is interested in non-destructive imaging of buried structures under one or more layers for the application of overlay and wafer alignment, specifically through optically opaque media. Recently an SPM technique has been developed for imaging subsurface features which can be potentially considered as a solution for overlay metrology. In this paper we present the use of Subsurface Ultrasonic Resonance Force Microscopy (SSURFM) used for IBO measurement. We used SSURFM for imaging the most commonly used overlay targets on a silicon substrate and photoresist. As a proof of concept we have imaged surface and subsurface structures simultaneously. The surface and subsurface features of the overlay targets are fabricated with programmed overlay errors of ±40 nm, ±20 nm, and 0 nm. The top layer thickness changes between 30 nm and 80 nm. Using SSURFM the surface and subsurface features were successfully imaged and the overlay errors were extracted, via a rudimentary image processing algorithm. The measurement results are in agreement with the nominal values of the programmed overlay errors.

High Tech Systems & Materials
Electronics
Industrial Innovation
Atomic Force Microscopy
Image-Based Overlay Measurement
Inspection
Metrology
Subsurface microscopy
Subsurface Ultrasonic Force Microscopy

http://resolver.tudelft.nl/uuid:32d7cb9e-3b0d-46d1-ae92-5744857abf9e

788781

SPIE

9781510616622

0277-786X

Metrology, Inspection, and Process Control for Microlithography XXXII 2018, 26 February - 1 March 2018, San Jose, CA, USA, 10585

Proceedings of SPIE - The International Society for Optical Engineering

105850O

conference paper