Integration of EUV lithography in the fabrication of 22-nm node devices

Abstract

On the road to insertion of extreme ultraviolet (EUV) lithography into production at the 16 nm technology node and below, we are testing its integration into standard semiconductor process flows for 22 nm node devices.In this paper, we describe the patterning of two levels of a 22 nm node test chip using single-exposure EUV lithography; the other layers of the test chip were patterned using 193 nm immersion lithography. We designed a full-field EUV mask for contact and first interconnect levels using rule-based corrections to compensate for the EUV specific effects of mask shadowing and imaging system flare. The resulting mask and the 0.25-NA EUV scanner utilized for the EUV lithography steps were found to provide more than adequate patterning performance for the 22 nm node devices. The CD uniformity across the exposure field and through a lot of wafers was approximately 6.1% (3σ) and the measured overlay on a representative test chip wafer was 13.0 nm (x) and 12.2 nm (y). A trilayer resist process that provided ample process latitude and sufficient etch selectivity for pattern transfer was utilized to pattern the contact and first interconnect levels. The etch recipes provided good CD control, profiles and end-point discrimination.The patterned integration wafers have been processed through metal deposition and polish at the contact level and are now being patterned at the first interconnect level.

High-sensitivity EUV Resists based on Tetrafluoroethylene contained Fluoropolymers

“…Relatively high sensitivity was obtained compared to high performance SSR3. The clearing dose (E 0 ) of the fluorinated-polymer based resist was 2.4 mJ/cm 2 while the E 0 of the SSR3 was 4.6 mJ/cm half-pitch (hp) 45 nm, a significantly high sensitivity of 6.3 mJ/cm2 was obtained.…”

Modeling and experiments of non-telecentric thick mask effects for EUV lithography

“…First, traditional OPC was performed with an assumed resist diffusion length. Then, as described further in reference [1], a density-based flare correction was applied. Finally, to account for HV effects, a simple bias of about 0.75nm/edge was applied to each edge.…”

“…Provided some remaining technical hurdles are overcome, such as development of a laser plasma EUV light source of sufficient power, the introduction of high volume manufacturing EUV scanners may soon become a reality [1]. From an OPC and mask pattern correction point of view, it is important to begin understanding the subtle differences between a DUV and an EUV lithographic tool and to begin developing correction strategies to account for them.…”

Evaluating scatterometry 3D capabilities for EUV

“…As extreme ultraviolet lithography (EUVL) [1,2] is more widely adopted to fabricate smaller and smaller patterns for electronic devices, scatterometry faces new challenges due to several reasons. For 14nm node and beyond, the feature size is nearly an order of magnitude smaller than the shortest wavelength used in scatterometry.…”