Applications of focused ion beams in microelectronics production, design and development

Abstract

Focused ion beam (FIB) systems using gallium liquid metal ion sources can remove material with a lateral resolution below 50 nm and can produce metal deposition at a similar resolution with ion beam-enhanced chemical vapour deposition. These capabilities have resulted in many valuable applications for the microelectronics industry. Circuit modifications are possible because existing connections can be severed and reconnected to different locations. Testing of circuitry can be enhanced by isolation of specific circuits, removal of overlayers and by creation of probe pads where desired. Grain sizes can be determined from secondary electron images by the delineation of individual grains due to orientation-dependent channeling of the ion beam. Secondary ion mass spectrometry analyses of small areas can provide ion images, elemental identification of small areas and endpoint detection with depth profiles. Scanning electron microscopy and transmission electron microscopy sections are prepared routinely using the FIB. These FIB-prepared sections are notable because specific features, such as defects, can be exposed and a range of materials including silicon, indium phosphide, gallium arsenide and even metal layers can be cut without distortion. Transmission electron micrographs of superior quality have been obtained with a large area of very uniform thickness that permits identification of features such as areas under stress.

Preparation of transmission electron microscopy cross-section specimens using focused ion beam milling

“…The needle is then raised away from the substrate and positioned over a support membrane on a TEM grid. Support membranes that have been used include continuous and lacey carbon membranes, 28 Formvar membranes, 40 and silicon nitride membranes. 34 The needle is lowered and simultaneously swept across the surface of the support membrane until an edge of the cross-section specimen catches on the membrane and attaches itself to it.…”

“…[28][29][30] Other techniques reported are the ''cantilever'' technique 31 and the ''encasing'' technique. 32 The trench technique involves the micromachining of an H-shaped sample in a polished or diced slice of the substrate.…”

Applications of the FIB lift-out technique for TEM specimen preparation

“…As a result, the application of this analytical technique continues to expand. One of the most valuable areas of interaction has been the preparation of specimens for transmission electron microscopy (TEM) (Assayag et al, 1993a,b;Basile et al, 1992;Black et al, 1992;Dickson et al, 1992;Hull et al, 1993Hull et al, , 1994Kirk et al, 1989;Lange and Czapski, 1991;Sandborn and Meyers, 1992;Stevie et al, 1995;Szot et al, 1992;Tarutani et al, 1992;Tomikawa and Shikata, 1993;Mendez et al, 1992;Nakajima et al, 1993;Overwijk et al, 1993;Yamaguchi et al, 1993). The concept of a lift-out method was first discussed by a group from Philips for semiconductor applications (Overwijk et al, 1993).…”

FIB Applications: A Historical Perspective

“…Development of TEM preparation coupled with the site specific capability provided by FIB significantly enhanced failure analysis for Si technology and in lightwave materials such as InP [1]. Initial TEM preparation still required mechanical polishing [2], but the use of a micromanipulator to lift-out a specimen was successful on the first attempt [3]. FIG.…”