Metal1 patterning study for random-logic applications with 193i, using calibrated OPC for litho and etch

Abstract

A Metal1-layer (M1) patterning study is conducted on 20nm node (N20) for random-logic applications. We quantified the printability performance on our test vehicle for N20, corresponding to Poly/M1 pitches of 90/64nm, and with a selected minimum M1 gap size of 70nm. The Metal1 layer is patterned with 193nm immersion lithography (193i) using Negative Tone Developer (NTD) resist, and a double-patterning Litho-Etch-Litho-Etch (LELE) process. Our study is based on Logic test blocks that we OPCed with a combination of calibrated models for litho and for etch. We report the Overlapping Process Window (OPW), based on a selection of test structures measured after-etch. We find that most of the OPW limiting structures are EOL (End-of-Line) configurations. Further analysis of these individual OPW limiters will reveal that they belong to different types, such as Resist 3D (R3D) and Mask 3D (M3D) sensitive structures, limiters related to OPC (Optical Proximity Corrections) options such as assist placement, or the choice of CD metrics and tolerances for calculation of the process windows itself. To guide this investigation, we will consider a 'reference OPC' case to be compared with other solutions. In addition, rigorous simulations and OPC verifications will complete the after-etch measurements to help us to validate our experimental findings.

Vertical Surrounding Gate Transistor for High Density and Low Voltage Operation in DRAM

“…The light source wavelength is 193 nm, and the numerical aperture (NA) is 1.35. The process window OPC is accessible in lithography process [16].…”

Optical proximity correction: A cross road of data flows

“…In the case of the trench printing process we use in this paper as an example, the litho-etch bias was observed to depend primarily on the litho CD itself as well as on the trench pitch. 7) We selected our calibration structures accordingly (i.e., structures with varying trench CD and pitch) and obtained a quite good model from this choice.…”