Richard H. Livengood

Subsurface damage from helium ions as a function of dose, beam energy, and dose rate

In recent years, helium ion microscopy has produced high resolution images with novel contrast mechanisms. However, when using any charged particle beam, one must consider the potential for sample damage. In this article, the authors will consider helium ion induced damage thresholds as compared to other more traditional charged-particle-beam technologies, as a function of dose, dose rate, and beam energy, and describe potential applications operating regimes.

Progress in extreme ultraviolet mask repair using a focused ion beam

The key challenge in extreme ultraviolet (EUV) mask defect repair is to avoid or limit the damage to the sensitive reflective multilayer (ML) stacks on the mask substrate and repair <55 nm mask defects. Our EUV mask design employs an oxide buffer layer between the ML and the absorber to protect the ML during repair. We have developed both opaque and clear EUV mask defect repair processes using focus ion beam (FIB) based gas-assisted etching (GAE) and ion-induced deposition. The process has been successfully demonstrated on our TiN baseline mask by 10× EUV print tests of 100 nm resist lines/spaces. More importantly we have assessed the current FIB tool performance capability and compared it with the general requirements for repairing the EUV mask for the 70 nm lithography node. The characterization includes minimum “effective” beam size, etch selectivity, and edge placement precision. We discussed the required improvements and future directions in repair tool research and development in order for the mask ...

The Prospects of a Subnanometer Focused Neon Ion Beam

The success of the helium ion microscope has encouraged extensions of this technology to produce beams of other ion species. A review of the various candidate ion beams and their technical prospects suggest that a neon beam might be the most readily achieved. Such a neon beam would provide a sputtering yield that exceeds helium by an order of magnitude while still offering a theoretical probe size less than 1-nm. This article outlines the motivation for a neon gas field ion source, the expected performance through simulations, and provides an update of our experimental progress.

Gas field ion source and liquid metal ion source charged particle material interaction study for semiconductor nanomachining applications

Semiconductor manufacturing technology nodes will evolve to the 22, 15, and 11 nm generations in the next few years. For semiconductor nanomachining applications, further beam spot size scaling is required beyond what is capable by present generation Ga+ focused ion beam technology. As a result, continued Ga+ beam scaling and/or alternative beam technology innovations will be required. In this work, several alternative ion beam technologies are explored and compared to Ga+ beam for key nanomachining and substrate interaction attributes. First, thorough Monte Carlo simulations were conducted with various ion species incident on silicon and copper. Additionally, silicon and copper substrates were experimentally exposed to ion beams of helium, neon, and gallium. These substrates were subsequently analyzed to determine the sputter yields and subsurface damage.

Design for (physical) debug for silicon microsurgery and probing of flip-chip packaged integrated circuits

As transistor technology shrinks, well-planned structures for debug must be designed into the circuitry. Analyzing signals from the backside using pre-planned probing structures, or fixing logic or speed bugs using on-silicon microsurgery has become even more important as the photomasks and other lithographic costs climb. Quick and reliable throughput of silicon fixes is critical to the success of debug, which multi-layer tapeouts cannot provide in a timely fashion.

Helium ion microscope invasiveness and imaging study for semiconductor applications

The helium ion gas field ion source is a novel charged particle source technology with potentially greater capabilities than electron beam based tools for imaging and nanomachining [Ward et al., J. Vac. Sci. Technol. B (to be published); Morgan et al., Microscopy Today 14, 24 (2006); V. N. Tondare, J. Vac. Sci. Technol. A 23, 1498 (2005)]. Potential strengths of He ions over electrons (scanning electron microscopy) are improved thin film surface sensitivity, material contrast, IBIC voltage contrast, Rutherford backscattering material contrast, and the ability to utilize in situ electron charge neutralization on floating substrates which have enhanced charging properties (e.g., masks, photoresist). In this article, the authors will discuss and illustrate examples highlighting several of these attributes. Helium ions, unlike electrons, induce collision events in the material lattice. A critical area to understand is the operating conditions and sample types for which the advantages of helium ion imaging can...

Probe current distribution characterization technique for focused ion beam

Focused ion beam technology continues to scale into the nano regime to keep pace with the scaling of semiconductor processes and biological science research. As the requirements for higher image resolution and machining precision increase, the necessity for comprehensive analysis and fine tuning of the ion beam profile is becoming increasingly important and more challenging. Older techniques such as edge resolution analysis or ion beam spot burns provide only a limited understanding of the ion beam probe current distribution. In this paper, the authors discuss a quantitative ion beam probe current distribution measurement technique. The principle of the approach will be discussed; modeling and empirical results of a gallium beam profile are presented in this paper.

Application of advanced micromachining techniques for the characterization and debug of high performance microprocessors

Micromachining techniques such as focused ion beam milling have become an integral part of the design debug cycle at many companies for providing fast verification of bug fixes in silicon. With flip chip packaging becoming more prevalent for future high performance processors, it is necessary to perform circuit edits and bug fixes on the silicon while the chip is packaged in the flip chip package. With this technology, however, conventional frontside probing and traditional circuit rewiring of packaged devices are not practical. We have developed a combination of new micromachining techniques for directly accessing metal signals from the backside of the chip. Here we will describe this new process, the technologies used, and some basic applications.

Nanomachining with a focused neon beam: A preliminary investigation for semiconductor circuit editing and failure analysis

As the semiconductor device scaling trend continues, advancement in both focused ion beam source development and application innovations are needed to retain failure analysis and nanomachining application capabilities. In this work, a neon gas field ionization source was studied for its nanomachining properties. The authors have analyzed neon’s nanomachining precision at 10 and 20 keV on blank Cu and SiO2 thin films. Subsurface material amorphization from neon and its correlation with beam current distribution are characterized by TEM. In addition, some preliminary nanomachining work was performed on a 32 nm test chip and successfully demonstrated end-pointing on various device layers.

Structural characterization of He ion microscope platinum deposition and sub-surface silicon damage

In this paper we studied helium ion beam induced deposition (HIBID) of Pt on a silicon wafer using the recently commercialized helium ion microscope (HIM) at 25 kV and low beam currents. The motivation of this work was to understand the impact of light, inert helium ions on deposition rate and structure purity, with some implications on the usefulness of HIM nano-machining for circuit modification. Two Pt-rich deposits with sub-micron dimensions were grown with HIBID at different ion beam currents. The pillar and substrate structure were studied using bright and dark field TEM images. The authors analyzed metal purity profile of the HIBID deposit on height using energy dispersive x-ray spectroscopy. The maximum Pt content measured reached 41%, which is the highest measured metal content of a HIBID-grown structure. TEM studies of the sub-surface damage to the Si shows more damage below the deposit grown at a higher beam current. The differences in amorphization layer thickness between the two different beam currents are discussed. A comparison to Pt deposition by Ga FIB and electron beam induced deposition is provided, along with conclusions regarding the usage of HIBID technology for circuit modification.