Scanning acoustic gigahertz microscopy for metrology applications in three-dimensional integration technologies

Abstract

Abstract. Current trends in microelectronics focus on three-dimensionally integrating different components to allow for increasing density and functionality of integrated systems. Concepts pursued involve vertical stacking and interconnecting technologies that employ micro bumping, wafer bonding, and through silicon vias (TSVs). Both the increasing complexity and the miniaturization of key elements in three-dimensional (3-D) components lead to new requirements on inspection and metrology tools and techniques as well as for failure analysis methodologies. For metrology and quality assessment in particular, methods operating nondestructively are of major importance. Scanning acoustic microscopy has the ability of illuminating optically opaque materials and, thus, allowing the assessment and imaging of internal structures. Conventional scanning acoustic microscopy (SAM) equipment can be applied to analyze the quality of wafer-bonded interfaces in 3-D integration but may reach its limitations when structures shrink in size and gain complexity. A new concept of acoustic inspection in the gigahertz (GHz) frequency band is explored for its applicability to 3-D integration technologies. Extending the acoustic inspection frequency allows for lateral resolutions in the 1-μm range and also enables the inspection of microbumps and TSVs in addition to wafer bonded interfaces, which exceed the applicability of conventional SAM. Three case studies are presented here ranging from conventional SAM on a full wafer scale to acoustic GHz microscopy on thin films and TSVs.

Using SOM neural network for X-ray inspection of missing-bump defects in three-dimensional integration

“…Owing to the strong capability of spreading through multiple materials, ultrasound inspection is of considerable importance to semiconductor quality control [13]. The most advanced scanning acoustic microscope (SAM) equipped with the gigahertz transducer can provide a resolution below 1 μm [14,15], although the necessity of coupling fluid brings lots of practical limitations. Nowadays, microfocus and nanofocus X-ray systems are widely used for various kinds of defects inspection in microelectronic packaging industry [16].…”

Microstructure Size Measurement Based on C-scan Image of Scanning Acoustic Microscopy

“…although they may not cause great damage to the performance of these devices in the initial phase, and some also sweep through electrical or logic performance test, in the use, subject to ambient temperature and humidity, these defects keep evolving and expanding under thermal and electromagnetic effects formed by thermal cycle, electromagnetic and stress fields. In this case, the thermal diffusion that further gets weak in the micro devices makes the internal structure fracture in different degrees, ultimately leading the micro devices to failure [1][2][3][4][5][6]. In order to improve the reliability of micro devices, we should identify and eliminate various defects that possibly appear on these devices in a timely manner, if necessary, they should be replaced.…”

Sparse Reconstruction for Micro Defect Detection in Acoustic Micro Imaging

“…AMI, also known as scanning acoustic microscopy, has been proven to be sufficiently sensitive for detecting micro defects and features, such as delamination [4,5], voids in the interfaces [6], microbubbles [7,8], stress distributions [9], solder bumps in flip chip [10,11], etc. The general working modes of AMI include A-scan, B-scan, and C-scan, obtaining time-domain signal, time-spatial image, and spatial image, respectively.…”

“…Till now, little work has been involved in research on sparse reconstruction for C-scan images of AMI. Actually, C-scan can provide more effective results than A/B-scan for detecting micro defects, and the transducer is a focusing transducer whose central frequency can be as high as 230 MHz [10,11] or even GHz [6]. The acoustic field distribution of the focusing transducer is completely different from the planar transducer, and the formation of the C-scan image is also different from that of the B-scan image.…”