Acoustic GHz-microscopy and its potential applications in 3D-integration technologies

Abstract

3D-integration is one of the most challenging approaches addressed by researchers in the field of microelectronics in the recent years. With the intension on integrating different components in three dimensions in one device performance and functionality will increase dramatically by reducing the devices footprint. A major challenge in 3D-integration concepts is the electrical interconnection of the stacked individual components. These interconnecting technologies employ micro bumping, temporary wafer bonding, wafer thinning and through silicon vias (TSVs). The increasing complexity and the miniaturization result in new requirements on testing, diagnostics, failure analysis and metrology techniques, methods and tools. Scanning acoustic microscopy (SAM) is a powerful tool for non-destructively inspecting internal structures and features. It employs elastic waves that can be focused and used for imaging and quantitative analyses. However, at conventionally used frequencies (5 MHz - 250 MHz) imaging resolution compromises the application on devices and technologies required in 3D-integration approaches. The current paper reports on the use of acoustic GHz-microscopy for the inspection, defect localization and its ability for identification of abnormalities in through silicon vias. Investigated were artificial and real defects in the TSV-fillings (voids) and the condition of the TSV-walls (rim-delaminations). Acoustic frequencies used in the current work ranged from 400 MHz up to 1.2 GHz allowing for imaging resolutions in the 1 μm - regime. However, highly focused acoustical lenses as employed here require large numerical apertures which inevitably result in a very complex wave propagation and acoustic field inside a solid sample. To improve the understanding and interpretation acoustic intensity fields have been simulated numerically. Results obtained by acoustic GHz-microscopy have been evaluated complimentarily by FIB-cross-sectioning and SEM imaging which gave a valuable insight into the abilities for acoustic TSV-inspection by GHz-SAM

Ultrahigh Frequency Ultrasonic Transducers (150MHz) Based on Silicon Lenses

“…Ultrasonic imaging has the advantages of being real-time, inexpensive and harmless to organisms. Acoustic microscopes [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ] are the systems used for high resolution ultrasonic imaging. Acoustic microscopes have great value in applications such as biomedical imaging [ 3 , 4 , 5 , 10 , 11 ] and non-destructive testing [ 7 , 8 , 9 , 12 , 13 ].…”

“…Acoustic microscopes [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ] are the systems used for high resolution ultrasonic imaging. Acoustic microscopes have great value in applications such as biomedical imaging [ 3 , 4 , 5 , 10 , 11 ] and non-destructive testing [ 7 , 8 , 9 , 12 , 13 ]. The resolution of systems is determined by the working frequency of transducers.…”

The Auto-focus Method for Scanning Acoustic Microscopy by Sparse Representation

“…Weglein fund that there is a series of regular periodical ( Δz ) oscillations occurs on the negative z side [11] in Eq. (5). It can be applied to measure the characteristics of different materials.…”

“…Alain Phommahaxay and Ingrid De Wolf made use of V(z) curve model to detect the defect in TSV of 3D-ICs [4]. Sebastian Brand applied GHz-SAM to check defect in 3D-Integration IC and obtained 1 µm-regime image resolutions in experiments [5,6].…”

Phasor Wave-Field Simulation Providing Direct Access to Instantaneous Frequency: A Demonstration for a Damped Elastic Wave Simulation

“…Elastodynamic wave propagation [1] is of crucial importance on a broad spectrum of length scales: starting in the kilometer range, from earth science including earthquake research and geophysical exploration [2][3][4], going down the scale to the millimeter and sub-millimeter range in medical diagnosis and therapy [5,6], sensors and actuators [7][8][9], material science [10][11][12], product and process monitoring [13][14][15], approaching the smallest scale, in non-destructive testing of microelectronic and nanoelectronic components [16,17] phononic crystals and hypersound propagation [18]. In many cases, damping of elastic waves is significant and desired; hence, it must be considered in the simulation of wave propagation phenomena [19][20][21].…”