Maskless electron beam lithography has the potential to extend semiconductor manufacturing to the sub-10 nm technology node. KLA-Tencor is currently developing Reflective Electron Beam Lithography (REBL) for high-volume 10 nm logic (16 nm HP). This paper reviews progress in the development of the REBL system towards its goal of 100 wph throughput for High Volume Lithography (HVL) at the 2X and 1X nm nodes. In this paper we introduce the Digital Pattern Generator (DPG) with integrated CMOS and MEMs lenslets that was manufactured at TSMC and IMEC. For REBL, the DPG is integrated to KLA-Tencor pattern generating software that can be programmed to produce complex, gray-scaled lithography patterns. Additionally, we show printing results for a range of interesting lithography patterns using Time Domain Imaging (TDI).
Previously, KLA-Tencor reported on the development of a Reflective Electron Beam Lithography (REBL) tool for maskless lithography at and below the 22 nm technology node1. Since that time, the REBL team and its partners (TSMC, IMEC) have made good progress towards developing the REBL system and Digital Pattern Generator (DPG) for direct write lithography. Traditionally, e-beam direct write lithography has been too slow for most lithography applications. Ebeam direct write lithography has been used for mask writing rather than wafer processing since the maximum blur requirements limit column beam current - which drives e-beam throughput. To print small features and a fine pitch with an e-beam tool requires a sacrifice in processing time unless one significantly increases the total number of beams on a single writing tool. Because of the continued uncertainty with regards to the optical lithography roadmap beyond the 22 nm technology node, the semiconductor equipment industry is in the process of designing and testing e-beam lithography tools with the potential for HVL.
Proc. SPIE. 8323, Alternative Lithographic Technologies IV
KEYWORDS: Lithography, Electron beam lithography, Electron beams, Silicon, Reflectivity, Electroluminescence, Monte Carlo methods, Computer aided design, Semiconducting wafers, Direct write lithography
Maskless electron beam lithography can potentially extend semiconductor manufacturing to the 16 nm technology node
and beyond. KLA-Tencor is developing Reflective Electron Beam Lithography (REBL) targeting high-volume 16 nm
half pitch (HP) production. This paper reviews progress in the development of the REBL system towards its goal of 100
wph throughput for High Volume Manufacturing (HVM) at the 2X and 1X nm nodes. We will demonstrate the ability to
print TSMC test patterns with the integrated system in photoresist on silicon wafers at 45 nm resolution. Additionally,
we present simulation and experimental results that demonstrate that the system meets performance targets for a typical
foundry product mix.
Previously, KLA-Tencor reported on the development of a REBL tool for maskless lithography at and below the 16 nm
HP technology node1. Since that time, the REBL team and its partners (TSMC, IMEC) have made good progress towards
developing the REBL system and Digital Pattern Generator (DPG) for direct write lithography. Traditionally, e-beam
direct write lithography has been too slow for most lithography applications. E-beam direct write lithography has been
used for mask writing rather than wafer processing since the maximum blur requirements limit column beam current - which drives e-beam throughput. To print small features and a fine pitch with an e-beam tool requires a sacrifice in processing time unless one significantly increases the total number of beams on a single writing tool. Because of the continued uncertainty with regards to the optical lithography roadmap beyond the 16 nm HP technology node, the semiconductor equipment industry is in the process of designing and testing e-beam lithography tools with the potential for HVM.
We review early challenges and opportunities for optical CD metrology (OCD) arising from the potential
insertion of double patterning technology (DPT) processes for critical layer semiconductor production. Due to the
immaturity of these new processes, simulations are crucial for mapping performance trends and identifying potential
metrology gaps. With an analysis methodology similar in spirit to the recent NIST OCD extendability study1, but with
aperture and noise models pertinent to current or projected production metrology systems, we use advanced simulation
tools to forecast OCD precision performance of key structural parameters (eg., CD, sidewall angle) at litho (ADI) and
etch (ACI) steps for a variety of mainstream optical measurement schemes, such as spectroscopic or angle-resolved, to
identify strengths and weaknesses of OCD metrology for patterning process control at 32 and 22nm technology nodes.
Test case geometries and materials for the simulated periodic metrology targets are derived from published DPT process
flows, with ITRS-style scaling rules, as well as rather standard scanner qualification use cases. Consistent with the
NIST study, we find encouraging evidence of OCD extendability through 22nm node dense geometries, a surprising and
perhaps unexpected result, given the near-absence of published results for the inverse optical scattering problem for
periodic structures in the deep sub-wavelength regime.
Spectroscopic critical dimension (SCDTM) metrology on line gratings has previously been shown to be a sensitive and useful technique for monitoring lithographic focus and exposure conditions. Line end shortening (LES) effects are sensitive to focus and potentially more sensitive to focus variation than side wall angle or other profile parameters of line gratings. Rectangular line segment structures that exhibit line-end shortening behavior are arranged in a rectangular two-dimensional (2D) array to provide a scatterometry signal sensitive to the profile of the thousands of line ends in the measurement beam spot. Spectroscopic ellipsometry (SE)-based scatterometry measurements were carried out on 2D array targets of rectangular features exposed in a focus-exposure matrix (FEM). The focus and exposure sensitivities of multiple shape parameters were found to be good and uniquely separable. In addition, the side wall angle of the line ends was found to be nearly linearly dependent on focus and provide necessary focus direction information. Focus and exposure can be determined from SCD measurements by applying a model generated to describe the focus-exposure behavior of multiple shape parameters using KLA Tencor's KT Analyzer software. Several different models based on different combinations of shape parameters were evaluated. Focus measurement precision of 3nm 3σ was obtained, which will be useful for lithography processes with tight depth of focus.
The accelerating trend to smaller linewidths and low-k1 lithography makes metrology and process control more challenging with each succeeding technology generation. Optical CD metrology based on spectroscopic ellipsometry provides higher precision, improved matching, and richer information for line width and shape (profile) control which complement conventional litho metrology techniques. Analysis of site-to-site, within-field, field-to-field, and cross-wafer CD and line-shape distributions using KLA-Tencor SpectraCD permits separation of sources of variation between the stepper and track thus enabling proper process control. Focus-exposure analysis using SpectraCD data provides a more complete understanding of the lithography process window. Comparison between SpectraCD CD measurements on nominal 1:5 Line/Space ratio grating targets to isolated line CD-SEM measurements show excellent correlation over a large focus-exposure process range, including sub-100nm features. This result provides verification that SCD measurements on grating targets can be used to monitor and provide feedback to lithography process for isolated lines.
Laser induced formation of CO2 and desorption of O2 are initiated with femtosecond and picosecond laser excitation of a Pt(111) surface prepared with coadsorbed CO and O2 at 90 K. The nonlinear fluence dependent reaction yields were measured for 267, 400, and 800 nm wavelengths, and for pulse durations from 80 fs to 3.6 ps. Two-pulse correlation experiments measuring total O2 desorption yield versus time delay between 80 fs pulses show a 0.9 ps HWHM central peak and a slower 0.1 ns time-scale. At 267 nm the relative yields of O2 and CO2 are found to depend on fluence. Comparison of results at different wavelengths and pulsewidths shows that nonthermalized surface electrons play a role in the laser-induced surface chemistry.