Due to their increasingly complex 3D geometries, upcoming gate all around (GAA) devices pose new metrology challenges for which there is not yet any established HVM metrology solution, in particular for various critical timed etch steps [5]. Soft x-ray (SXR) scatterometry using 10-20 nm wavelength light is a promising next-generation metrology technique for 3D profile metrology and overlay (OVL) applications. This wavelength regime offers unique benefits over existing metrology techniques today: (1) Short wavelengths allow for higher resolution measurements than traditional visible wavelengths could offer, enabling measurement of structures at device pitches. (2) Primarily single scattering yields low correlation between parameters and aids physical interpretation of signals. This enables many parameters of interest to be extracted accurately and simultaneously. (3) SXR provides 3D capability, with stack heights up to 400 nm supported and high depth resolution due to the broadband source and sensor. These properties together make SXR suitable for measuring the 3D profiles of advanced devices such as gate all around (GAA) transistors, as well as after develop (ADI) overlay at device pitch. In this paper, we demonstrate SXR for profile metrology of GAA devices. We show sensitivity to average SiGe lateral recess etch depth as well as individual nanosheet critical dimensions, which cannot be reliably accessed by other nondestructive, inline metrology techniques available today. We furthermore demonstrate sensitivity in ADI OVL measurements directly on device-pitch structures in the presence of an underlying patterned nuisance layer.
The logic manufacturing process requires small in-device metrology targets to exploit the full dose correction potential of the modern scanners and process tools. A high-NA angular resolved scatterometer (YieldStar S-1250D) was modified to demonstrate the possibility of OCD measurements on 5x5µm2 targets. The results obtained on test wafers in a logic manufacturing environment, measured after litho and after core etch, showed a good correlation to larger reference targets and AEI to ADI intra-field CDU correlation, thereby demonstrating the feasibility of OCD on such small targets. The data was used to determine a reduction potential of 55% for the intra-field CD variation, using 145 points per field on a few inner fields, and 33% of the process induced across wafer CD variation using 16 points per field full wafer. In addition, the OCD measurements reveal valuable information on wafer-to-wafer layer height variations within a lot.
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.