John J. Hench

Reflective electron-beam lithography: progress toward high-throughput production capability

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.

Forward solve algorithms for optical critical dimension metrology

A review of selected current and new Maxwell equation solve algorithms used in critical dimension metrology is presented. We show that the standard RCWA can have serious issues under certain conditions, even in some typical scatterometry applications. We present some results showing that some of the newer algorithms we developed can significantly outperform the RCWA. The strengths and weakness of algorithms are illustrated.

Opportunities and challenges for optical CD metrology in double patterning process control

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.

Shape recovery for rotating surfaces: A tutorial

One of the key elements of the metrology system for the rotating stage used in the Reflective Electron Beam Lithography (REBL) instrument is a set of laser interferometers that measures the distance to a rotating cylindrical ring shaped mirror. This metrology arrangement allows the lateral x-y motion of the stage to be measured independent from the other four degrees of motion. One source of error in this measurement is the non-roundness of the shape of the mirror. By using redundant interferometry measurements, the shape of the mirror may be computed and its effects can be removed from the lateral motion estimate. This tutorial gives an overview of the mathematics of the shape recovery algorithm used in REBL as well as a guide for some of the practical issues that arise in shape estimation and stage design, not the least of which is the angular placement of the sensors.

Applications of control systems and optimization in the design of semiconductor capital equipment

This tutorial presents several examples of high performance control systems in the Semiconductor equipment industry. Examples include technologies used in lithography and mask inspection.

Reflective electron-beam lithography performance for the 10nm logic node

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.