Daniel J. C. Herr

New frontiers: self-assembly and nanoelectronics

In the quest for new semiconductor materials and processes, researchers focus on self-assembly, a concept that draws from diverse disciplines like chemistry, biology, material science, and electrical engineering. The following areas are examined: information theory; thermodynamics, synergetics and self-assembly; ribosome based lithography; nanofabrication by self-assembly; molecular electronics; and smart matter.

Semiconductor Research Needs in the Nanoscale Physical Sciences: A Semiconductor Research Corporation Working Paper

The purpose of this paper is to identify areas in the basic physical sciences where additional research is needed to sustain the extraordinary progress in electronics that has now extended for several decades. Also, it is argued that basic research will provide the foundation for the discovery of new generations of nanoelectronic devices that will continue the experimental rate of reduction in cost per function. Some of the fundamental areas requiring further research are the chemistry and physics of material interfaces, conductivity at small dimensions, deterministic doping effects, and nanomagnetics. Discovery research also is needed in the functional synergy of nanoelectronic materials and non-traditional fabrication methods.

Dissolution inhibition mechanism of ANR photoresists: crosslinking vs. -OH site consumption

This paper reports our recent studies of crosslinking of phenolic resins with melamines through 1H and 13C NMR, GPC, and dissolution rate changes. For the NMR studies, we used model phenolic compounds such as 4-ethylphenol, and the hexafunctional crosslinker, hexamethoxymethylmelamine (HMMM). The NMR clearly reveals that the crosslinking reaction occurs quantitatively at the hydroxyl site of the phenol. This result raises the question of whether the dissolution inhibition observed in the ANR resists is due to -OH site consumption or to the rapid rise in molecular weight of the phenolic polymer. Comparison of tetrahydrofuran (THF) extraction vs. aqueous tetramethylammonium hydroxide (TMAH) development shows that the dose required to insolubilize the resist is much higher for THF. Gel permeation chromatography on the soluble fraction extracted into THF showed a fraction with molecular weights up to 400,000 Daltons. We believe that crosslinking and -OH site protection provide synergistic dissolution selectivity in TMAH, leading to high contrast and high resolution. Finally, we present results on the effect of (chi) , which is proportional to the ratio of phenolic hydroxyl groups to melamine methoxy groups, on the lithographic performance of ANR photoresists. At low (chi) , the DUV resists can be used as increased absorption resists over topography, and development times can be shortened significantly. We have also found that increasing the melamine loading can lessen the degree of bridging residue observed between lines.

On designing sub-70-nm semiconductor materials and processes

In this paper, the authors examine salient materials and processing technologies that we believe are necessary to sustain the continued cadence of mainstream silicon technology. Specifically, they discuss the need for technologies that yield atomically smooth interfaces and suggest that perhaps molecular beam epitaxy has reached the point where it can transition into mainstream silicon manufacturing. Patterning candidates for next generation lithography are discussed and the possible role of maskless patterning technologies is considered. The role of doping on the performance of projected future generation devices is discussed and the tradeoffs involved in the precise control of the number and location of dopants for devices in the far nanometer regime are considered. ESH issues and possible remedies for future generation processes are also briefly discussed.

Metrology and Characterization Challenges for Emerging Research Materials and Devices

The International Technology Roadmap for Semiconductors (ITRS) Emerging Research Materials (ERM) and Emerging Research Devices (ERD) Technology Workgroups have identified materials and devices that could enable continued increases in the density and performance of future integrated circuit (IC) technologies and the challenges that must be overcome; however, this will require significant advances in metrology and characterization to enable progress. New memory devices and beyond CMOS logic devices operate with new state variables (e.g., spin, redox state, etc.) and metrology and characterization techniques are needed to verify their switching mechanisms and scalability, and enable improvement of operation of these devices. Similarly, new materials and processes are needed to enable these new devices. Additionally, characterization is needed to verify that the materials and their interfaces have been fabricated with required quality and performance.

Editorial [device concepts, architectural strategies, and interfacing methodologies for realizing nanoscale sensor systems]

The papers in this special issue explore Device Concepts, Architectural Strategies, and Interfacing Methodologies for Realizing Nanoscale Sensor Systems. This is volume II of the special issue. Some of the papers are based in part on oral and poster presentations at the Nanoelectronic Devices for Defense and Security Conference, held in Fort Lauderdale, FL, from September 27-October 2, 2009.

Applications Of Response Surface Methodology: I. A General And Practical Approach To Process Optimization

Response surface methodology is used to model properties of positive photoresist which have been subjected to several operations in a photolithographic process. The impact of these models on process performance and latitude has been investigated and a general approach to process optimization has been proposed: m P[X(1),X(2), . . . 1 = fl F(i) i =0 where P[X(1),X(2), . . .1 represents an overall process optimization function. It measures the overall performance and stability of a process as a func-tion of process variables X(1), X(2), etc. This optimization function is defined as the product of normalized signal-to-noise ratios, F(i), for the set of responses, i, considered. The function F(i) quantifies the ability of a process to achieve the specified response and the sensitivity of the response to perturbations in the process variables. This approach is particularly useful when more than one response must be optimized with a given process. The application of this approach can result in a several-fold increase in process performance and latitude. Examples are presented and discussed.

The Need for Convergence and Emergence in Twenty-first Century Nano-STEAM+ Educational Ecosystems

This chapter examines the necessary attributes of Nanoscale STEAM+ education systems that can address strategic twenty-first century academic, government, industrial and societal needs. Such systems leverage the mutually supportive interdependence of all key stakeholders within the educational supply chain. They also nurture convergent, transdisciplinary and hands-on platform-enhanced educational opportunities. In this chapter, I share two sets of stories that highlight some similarities between the processes of innovation and education. These stories drive the proposed recommendations and guiding principles for twenty-first century educational ecosystems. Key chapter goals are to stimulate conversations on best practice processes and systems that: (1) Catalyze and sustain interest in Nano-STEAM+ education and (2) enable adaptive, convergent and innovative educational infrastructures. This chapter also recognizes that it may be a challenge for some stakeholders to engage in the proposed educational ecosystem, and recommends options to enhance accessibility.

Emerging Patterning Materials: Trends, Challenges, and Opportunities in Patterning and Materials by Design

Patterning technology is entering the nanomaterials era. Breakthrough advances in the basic sciences over the last twenty years are catalyzing novel material and assembly options. In the near future, these options may warrant consideration for fabricating advanced information processing technologies. However, material technology advances alone are not sufficient to induce changes and chemical substitution in manufacturing. In fact, manufacturing technology will change only when no other option exists. Therefore, the concurrent trend in lithographic challenges is noteworthy. Recent revisions of the International Technology Roadmap for Semiconductors (ITRS) indicate that it is becoming increasingly difficult for mainstream lithographic technologies to satisfy projected ITRS dimensional scaling requirements, shown in Table 1.

Device Concepts, Architectural Strategies, and Interfacing Methodologies for Nanoscale Sensor Systems

The twenty papers in this special issue explore device concepts, architectural strategies and interfacing methodologies for nanoscale sensor systems. Some of the papers are based in part on oral and poster presentations at the Nanoelectronic Devices for Defense and Security Conference, held in Fort Lauderdale, FL, from September 27-October 2, 2009.